Patent Publication Number: US-11050291-B2

Title: Systems and methods for energy storage using phosphorescence and waveguides

Description:
CROSS-REFERENCE 
     This application is a continuation of U.S. patent application Ser. No. 16/516,801, filed Jul. 19, 2019, which is a continuation of International Patent Application No. PCT/US19/020592, filed Mar. 4, 2019, which claims benefit of U.S. Provisional Application No. 62/638,646, filed Mar. 5, 2018, each of which applications is entirely incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     Especially in an age where so many activities and functions depend on a continuous supply of power, lapses or interruptions in the provision of power may lead to highly undesirable results. These recent years have seen a fast-growing market for readily accessible power, such as in batteries, supercapacitors, fuel cells, and other energy storage devices. However, such energy storage devices are often limited in many aspects. For example, they may be volatile or unstable under certain operating conditions (e.g., temperature, pressure) and become ineffective or pose a safety hazard. In some cases, an energy storage device may itself be consumed during one or more cycles of converting or storing energy and thus have limited lifetime. In some cases, a rate of charging may be too slow to effectively support or satisfy a rate of consumption of power. 
     SUMMARY 
     Recognized herein is a need for reliable systems and methods for energy storage. The systems and methods for energy storage disclosed herein may provide superior charging rates to those of conventional chemical batteries, for example, on the order of 100 times faster or more. The systems and methods disclosed herein may provide superior lifetimes to those of conventional chemical batteries, for example, on the order of 10 times more recharge cycles or more. The systems and methods disclosed herein may be portable. The systems and methods disclosed herein may be stable and effective in relatively cold operating temperature conditions. 
     The systems and methods disclosed herein may use phosphorescent material to store energy over a finite duration of time. For example, the phosphorescent material may store and/or convert energy with substantial time delay. The systems and methods disclosed herein may use light sources to provide an initial source of energy in the form of optical energy. The light sources can be artificial light sources, such as light emitting diodes (LEDs). The systems and methods disclosed herein may use photovoltaic cells to generate electrical power from optical energy. A system for energy storage may comprise a light source, a phosphorescent material, a photovoltaic cell, and a waveguide to direct waves between the light source and the phosphorescent material and/or between the photovoltaic cell and the phosphorescent material. 
     In an aspect, provided is a system for storing energy, comprising: a light source configured to emit optical energy at a first wavelength from a surface of the light source; a phosphorescent material configured to (i) absorb the optical energy at the first wavelength, and (ii) at a rate slower than a rate of absorption, emit optical energy at a second wavelength, wherein the second wavelength is greater than the first wavelength; a photovoltaic cell adjacent to the phosphorescent material, wherein the photovoltaic cell is configured to (i) absorb optical energy at the second wavelength, and (ii) generate electrical power from optical energy; and a waveguide adjacent to the phosphorescent material, wherein the waveguide is configured to (i) direct the optical energy at the first wavelength from the light source to the phosphorescent material or (ii) direct the optical energy at the second wavelength from the phosphorescent material to the photovoltaic cell. 
     In some embodiments, the waveguide is configured to direct the optical energy at the first wavelength from the light source to the phosphorescent material and wherein the system comprises a second waveguide configured to direct the optical energy at the second wavelength from the phosphorescent material to the photovoltaic cell. In some embodiments, the second waveguide and the phosphorescent material are concentric. 
     In some embodiments, the waveguide is configured to direct the optical energy at the first wavelength from the light source to the phosphorescent material, and wherein the waveguide is adjacent to the light source. In some embodiments, the waveguide is in contact with the light source. 
     In some embodiments, the waveguide is configured to direct the optical energy at the second wavelength from the phosphorescent material to the photovoltaic cell, and wherein the waveguide is adjacent to the photovoltaic cell. In some embodiments, the waveguide is in contact with the photovoltaic cell. 
     In some embodiments, the waveguide comprises one or more reflective surfaces, wherein the reflective surfaces are configured to (i) direct the optical energy at the first wavelength from the light source to the phosphorescent material or (ii) direct the optical energy at the second wavelength from the phosphorescent material to the photovoltaic cell. In some embodiments, the waveguide comprises a plurality of reflective surfaces having increasingly large reflective surfaces along an optical path within the waveguide, such that a first set of waves from the light source are configured to be reflected at a first reflective surface of the plurality of reflective surfaces for excitation of a first volume of phosphorescent material, and a second set of waves from the light source are configured to be reflected at a second reflective surface of the plurality of reflective surfaces for excitation of a second volume of phosphorescent material, wherein the second volume of phosphorescent material is disposed at a greater distance from the light source than the first volume of phosphorescent material. 
     In some embodiments, the light source is a light-emitting diode (LED). 
     In some embodiments, a rechargeable battery is electrically coupled to the light source and the photovoltaic cell, and wherein at least part of the electrical power generated by the photovoltaic cell charges the rechargeable battery, and wherein at least part of electrical power discharged by the rechargeable battery powers the light source. 
     In some embodiments, the phosphorescent material comprises strontium aluminate and europium. In some embodiments, the phosphorescent material comprises dysprosium. 
     In some embodiments, the phosphorescent material comprises grains having a particle size of less than about 5 micrometers. 
     In some embodiments, the phosphorescent material comprises grains having a particle size of less than about 20 nanometers. 
     In some embodiments, the light source is adjacent to and in contact with the waveguide. 
     In some embodiments, the light source is not in contact with the waveguide and the phosphorescent material. In some embodiments, the light source is located remote from the waveguide and the phosphorescent material, wherein the light source is in optical communication with the waveguide. 
     In some embodiments, the system further comprises a coating on the waveguide, wherein the coating is in optical communication with the waveguide and the phosphorescent material, wherein the coating comprises an optical filter. In some embodiments, the optical filter is a dichroic element. In some embodiments, the optical filter is configured to transmit waves having the first wavelength from the waveguide to the phosphorescent material and reflect waves having the second wavelength from the phosphorescent material back to the phosphorescent material. In some embodiments, the coating is in contact with the waveguide and the phosphorescent material. 
     In another aspect, provided is a method for storing energy, comprising: (a) emitting optical energy at a first wavelength from a surface of a light source; (b) directing the optical energy at the first wavelength, via a first waveguide, to a phosphorescent material; (c) at a rate slower than a rate of absorption of the optical energy at the first wavelength, emitting, by the phosphorescent material, optical energy at a second wavelength, wherein the second wavelength is greater than the first wavelength; (d) directing the optical energy at the second wavelength, via a second waveguide, to a photovoltaic cell, wherein the surface of the photovoltaic cell is adjacent to the phosphor; and (e) generating electrical power from the optical energy at the second wavelength. 
     In some embodiments, the second waveguide and the phosphorescent material are concentric. 
     In some embodiments, the first waveguide is adjacent to the light source. 
     In some embodiments, the second waveguide is adjacent to the photovoltaic cell. 
     In some embodiments, the first waveguide comprises one or more reflective surfaces, wherein the reflective surfaces are configured to direct the optical energy at the first wavelength from the light source to the phosphorescent material. In some embodiments, the first waveguide comprises a plurality of reflective surfaces having increasingly large reflective surfaces along an optical path within the first waveguide, such that a first set of waves from the light source are configured to be reflected at a first reflective surface of the plurality of reflective surfaces for excitation of a first volume of phosphorescent material, and a second set of waves from the light source are configured to be reflected at a second reflective surface of the plurality of reflective surfaces for excitation of a second volume of phosphorescent material, wherein the second volume of phosphorescent material is disposed at a greater distance from the light source than the first volume. 
     In some embodiments, the light source is a light-emitting diode (LED). 
     In some embodiments, a rechargeable battery is electrically coupled to the light source and the photovoltaic cell, and wherein at least part of the electrical power generated by the photovoltaic cell charges the rechargeable battery, and wherein at least part of electrical power discharged by the rechargeable battery powers the light source. 
     In some embodiments, the phosphorescent material comprises strontium aluminate and europium. In some embodiments, the phosphorescent material comprises dysprosium. 
     In some embodiments, the phosphorescent material comprises grains having a particle size of less than about 5 micrometers. 
     In some embodiments, the phosphorescent material comprises grains having a particle size of less than about 20 nanometers. 
     In some embodiments, the light source is in contact with the first waveguide. 
     In some embodiments, the light source is not in contact with the first waveguide and the phosphorescent material. In some embodiments, the light source is located remote from the first waveguide and the phosphorescent material, wherein the light source is in optical communication with the first waveguide. 
     In some embodiments, the first waveguide comprises a coating on the first waveguide, wherein the coating is in optical communication with the first waveguide and the phosphorescent material, wherein the coating comprises an optical filter. In some embodiments, the optical filter is a dichroic element. In some embodiments, the optical filter is configured to transmit waves having the first wavelength from the first waveguide to the phosphorescent material and reflect waves having the second wavelength from the phosphorescent material back to the phosphorescent material. In some embodiments, the coating is in contact with the waveguide and the phosphorescent material. 
     In another aspect, provided is a method for wireless charging, comprising: (a) providing a battery assembly comprising: a phosphorescent material configured to (i) absorb optical energy at a first wavelength, and (ii) at a rate slower than a rate of absorption, emit optical energy at a second wavelength, wherein the second wavelength is greater than the first wavelength; a photovoltaic cell adjacent to the phosphorescent material, wherein the photovoltaic cell is configured to (i) absorb optical energy at the second wavelength, and (ii) generate electrical power from optical energy; and a waveguide adjacent to the phosphorescent material, wherein the waveguide is configured to (i) direct the optical energy at the first wavelength from a light source to the phosphorescent material or (ii) direct the optical energy at the second wavelength from the phosphorescent material to the photovoltaic cell; and (b) providing optical energy at the first wavelength from the light source to the waveguide, wherein the light source is not in contact with the waveguide and the phosphorescent material, and wherein the light source is in optical communication with the waveguide. emitting optical energy at a first wavelength from a surface of a light source, thereby charging the battery assembly. 
     Another aspect of the present disclosure provides a non-transitory computer readable medium comprising machine executable code that, upon execution by one or more computer processors, implements any of the methods above or elsewhere herein. 
     Another aspect of the present disclosure provides a system comprising one or more computer processors and computer memory coupled thereto. The computer memory comprises machine executable code that, upon execution by the one or more computer processors, implements any of the methods above or elsewhere herein. 
     Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     INCORPORATION BY REFERENCE 
     All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also “Figure” and “FIG.” herein) of which: 
         FIG. 1  shows an exemplary photon battery assembly. 
         FIG. 2  shows a photon battery in communication with an electrical load. 
         FIG. 3  shows an exemplary photon battery assembly in application. 
         FIG. 4A  illustrates a photon battery assembly with a waveguide. 
         FIG. 4B  illustrates a photon battery assembly with a coating comprising an optical filter. 
         FIG. 5  illustrates another photon battery assembly with a waveguide. 
         FIG. 6  illustrates another photon battery assembly with waveguides. 
         FIG. 7  shows a stack of a plurality of photon battery assemblies. 
         FIG. 8  shows an exploded view of another configuration for a photon battery assembly stack with hollow core waveguides. 
         FIG. 9  illustrates a partial cross-sectional side view of the photon battery assembly stack of  FIG. 8 . 
         FIG. 10  illustrates a method of storing energy in a photon battery. 
         FIG. 11  shows a computer system configured to implement systems and methods of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed. 
     Provided herein are systems and methods for energy storage. The systems and methods disclosed herein may use phosphorescent material to store energy over a significant duration of time, such as by making use of the time-delayed re-emission properties of phosphorescent material. For example, the phosphorescent material may store and/or convert energy with substantial time delay. A light source can provide an initial source of energy to the phosphorescent material in the form of optical energy. For example, the phosphorescent material may absorb optical energy from the light source at a first wavelength, and after a time delay, emit optical energy at a second wavelength. The light source can be an artificial light source, such as a light emitting diode (LED). A photovoltaic cell can generate electrical power from optical energy, such as from optical energy at the second wavelength that is emitted by the phosphorescent material. A waveguide may direct waves, such as the optical energy from the light source at the first wavelength between the light source and the phosphorescent material and/or the optical energy at the second wavelength between the phosphorescent material and the photovoltaic cell. Such waveguides may increase energy density and compactness of the energy storage system. Beneficially, such waveguide may greatly increase efficiency of the time-delayed optical energy transfer between the phosphorescent material and the light source and the photovoltaic cell, as well as facilitate efficient use of the available phosphorescent material. 
     The systems and methods for energy storage disclosed herein may provide superior charging rates to those of conventional chemical batteries, for example, on the order of 100 times faster or more. The systems and methods disclosed herein may provide superior lifetimes to those of conventional chemical batteries, for example, on the order of 10 times more recharge cycles or more. The systems and methods disclosed herein may be portable. The systems and methods disclosed herein may be stable and effective in relatively cold operating temperature conditions. 
     Reference will now be made to the figures. It will be appreciated that the figures and features therein are not necessarily drawn to scale. 
       FIG. 1  shows an exemplary photon battery assembly. A photon battery assembly  100  can comprise a light source  101 , a phosphorescent material  102 , and a photovoltaic cell  103 . The phosphorescent material may be adjacent to both the light source and the photovoltaic cell. For example, the phosphorescent material can be sandwiched by the light source and the photovoltaic cell. The phosphorescent material can be between the light source and the photovoltaic cell. While  FIG. 1  shows the light source, phosphorescent material, and photovoltaic cell as a vertical stack, the configuration is not limited as such. For example, the light source, phosphorescent material, and photovoltaic cell can be horizontally stacked or concentrically stacked. The light source and the photovoltaic cell may or may not be adjacent to each other. In some instances, the phosphorescent material can be adjacent to a light-emitting surface of the light source. In some instances, the phosphorescent material can be adjacent to a light-absorbing surface of the photovoltaic cell. 
     Regardless of contact between the phosphorescent material  102  and light source  101 , the phosphorescent material and the light source may be in optical communication. For example, as described elsewhere herein, the phosphorescent material and the light source may be in optical communication via a waveguide. Regardless of contact between the phosphorescent material and photovoltaic cell  103 , the phosphorescent material and the photovoltaic cell may be in optical communication. For example, as described elsewhere herein, the phosphorescent material and the photovoltaic cell may be in optical communication via a waveguide. In some instances, the same waveguide may be configured to facilitate optical communication between the phosphorescent material and the photovoltaic cell and between the phosphorescent material and the light source. 
     The phosphorescent material  102  may or may not be contacting the light source  101 . If the phosphorescent material and the light source are in contact, the phosphorescent material can interface a light-emitting surface of the light source. The phosphorescent material and the light source can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the light source and/or a support carrying the phosphorescent material may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the phosphorescent material may have adhesive and/or cohesive properties and adhere to the light source without an independent fastening mechanism. For example, the phosphorescent material may be painted or coated on the light-emitting surface of the light source. In some instances, the phosphorescent material may be coated onto primary, secondary, and/or tertiary optics of the light source. In some instances, the phosphorescent material may be coated onto other optical elements of the light source. The phosphorescent material and the light source can be permanently or detachably fastened together. For example, the phosphorescent material and the light source can be disassembled from and reassembled into the photon battery assembly  100  without damage (or with minimal damage) to the phosphorescent material and/or the light source. Alternatively, while in contact, the phosphorescent material and the light source may not be fastened together. 
     If the phosphorescent material  102  and the light source  101  are not in contact, the phosphorescent material can otherwise be in optical communication with a light-emitting surface of the light source, such as via a waveguide. For example, the phosphorescent material can be positioned in an optical path of light emitted by the light-emitting surface of the light source. In some instances, there can be an air gap between the phosphorescent material and the light source. In some instances, there can be another intermediary layer between the phosphorescent material and the light source. The intermediary layer can be air or other fluid. The intermediary layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the phosphorescent material and the light source. 
     The phosphorescent material  102  may or may not be contacting the photovoltaic cell  103 . If the phosphorescent material and the photovoltaic cell are in contact, the phosphorescent material can interface a light-absorbing surface of the photovoltaic cell. The phosphorescent material and the photovoltaic cell can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the photovoltaic cell and/or a support carrying the phosphorescent material may be coupled or fastened together at the interface. In some instances, the phosphorescent material may have adhesive properties and adhere to the photovoltaic cell without an independent fastening mechanism. For example, the phosphorescent material may be painted or coated on the light-absorbing surface of the photovoltaic cell. In some instances, the phosphorescent material may be coated onto primary, secondary, and/or tertiary optics of the photovoltaic cell. In some instances, the phosphorescent material may be coated onto other optical elements of the photovoltaic cell. The phosphorescent material and the photovoltaic cell can be permanently or detachably fastened together. For example, the phosphorescent material and the photovoltaic cell can be disassembled from and reassembled into the photon battery assembly  100  without damage (or with minimal damage) to the phosphorescent material and/or the photovoltaic cell. Alternatively, while in contact, the phosphorescent material and the photovoltaic cell may not be fastened together. 
     If the phosphorescent material  102  and the photovoltaic cell  103  are not in contact, the phosphorescent material can otherwise be in optical communication with a light-absorbing surface of the photovoltaic cell. For example, the light-absorbing surface of the photovoltaic cell can be positioned in an optical path of light emitted by the phosphorescent material. In some instances, there can be an air gap between the phosphorescent material and the photovoltaic cell. In some instances, there can be another intermediary layer between the phosphorescent material and the photovoltaic cell. The intermediary layer can be air or other fluid. The intermediary layer can be a light guide, light concentrator, or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the phosphorescent material and the photovoltaic cell. 
     In some instances, the photon battery assembly  100  can be assembled or disassembled, such as into the light source  101 , phosphorescent material  102 , or the photovoltaic cell  103  independently, or into sub-combinations thereof. In some instances, the photon battery assembly can be assembled or disassembled without damage to the different parts or with minimal damage to the different parts. 
     In some instances, the photon battery assembly  100  can be housed in a shell, outer casing, or other housing. The photon battery assembly  100 , and/or shell thereof can be portable. For example, the photon battery assembly can have a maximum dimension of at most about 1 meter (m), 90 centimeters (cm), 80 cm, 70 cm, 60 cm, 50 cm, 45 cm, 40 cm, 35 cm, 30 cm, 25 cm, 20 cm, 15 cm, 10 cm, 9 cm, 8 cm, 7 cm, 6 cm, 5 cm, or smaller. A maximum dimension of the photon battery assembly may be a dimension of the photon battery assembly (e.g., length, width, height, depth, diameter, etc.) that is greater than the other dimensions of the photon battery assembly. Alternatively, the photon battery assembly may have greater maximum dimensions. For example, a photon battery assembly having a higher energy storage capacity can have larger dimensions and may not be portable. 
     The light source  101  can be an artificial light source, such as a light emitting diode (LED) or other light emitting device. For example, the light source can be a laser or a lamp. The light source can be a plurality of light emitting devices (e.g., a plurality of LEDs). In some instances, the light source can be arranged as one LED. In some instances, the light source can be arranged as rows or columns of multiple LEDs. The light source can be arranged as arrays or grids of multiple columns, rows, or other axes of LEDs. The light source can be a combination of different light emitting devices. A light emitting surface of the light source can be planar or non-planar. A light emitting surface of the light source can be substantially flat, substantially curved, or form another shape. 
     The light source can be supported by rigid and/or flexible supports. For example, the supports can direct the light emitted by the light source to be directional or non-directional. In some instances, the light source can comprise primary and/or secondary optical elements. In some instances, the light source can comprise tertiary optical elements. In some instances, the light source can comprise other optical elements at other levels or layers (e.g., lens, reflector, diffusor, beam splitter, etc.). The light source can be configured to convert electrical energy to optical energy. For example, the light source can be powered by an electrical power source, which may be external or internal to the photon battery assembly  100 . The light source can be configured to emit optical energy (e.g., as photons), such as in the form of electromagnetic waves. In some instances, the light source can be configured to emit optical energy at a wavelength or a range of wavelengths that is capable of being absorbed by the phosphorescent material  102 . For example, the light source can emit light at wavelengths in the ultraviolet range (e.g., 10 nanometers (nm) to 400 nm). In some instances, the light source can emit light at other wavelengths or ranges of wavelengths in the electromagnetic spectrum (e.g., infrared, visible, ultraviolet, x-rays, etc.). 
     In some instances, the light source  101  can be a natural light source (e.g., sun light), in which case the phosphorescent material  102  in the photon battery assembly  100  may be exposed to the natural light source to absorb such natural light. 
     The phosphorescent material  102  can absorb optical energy at a first wavelength (or first wavelength range) and emit optical energy at a second wavelength (or second wavelength range) after a substantial time delay. The second wavelength can be a different wavelength than the first wavelength. The optical energy at the first wavelength that is absorbed by the phosphorescent material can be at a higher energy level than the optical energy at the second wavelength that is emitted by the phosphorescent material. The second wavelength can be greater than the first wavelength. In an example, the phosphorescent material can absorb energy at ultraviolet range wavelengths (e.g., 10 nm to 400 nm) and emit energy at visible range wavelengths (e.g., 400 nm to 700 nm). For example, the phosphorescent material can absorb blue photons and, after a time delay, emit green photons. The phosphorescent material can absorb optical energy (e.g., photons) at other wavelengths (or ranges of wavelengths) and emit optical energy at other wavelengths (or ranges of wavelengths), such as in the electromagnetic spectrum (e.g., infrared, visible, ultraviolet, x-rays, etc.) wherein the energy emitted is at a lower energy level than the energy absorbed. A rate of emission of optical energy by the phosphorescent material can be slower than a rate of absorption of optical energy by the phosphorescent material. An advantage of this difference in rate is the ability of the phosphorescent material to release energy at a slower rate than absorbing such energy, thus storing the energy during such time delay. 
     The phosphorescent material  102  can be crystalline, solid, liquid, ceramic, in powder form, granular or other particle form, liquid form, or in any other shape, state, or form. The phosphorescent material can be long-lasting phosphors. In an example, the phosphorescent material can comprise strontium aluminate doped with europium (e.g., SrAl 2 O 4 :Eu). Some other examples of phosphorescent material can include, but are not limited to, zinc gallogermanates (e.g., Zn 3 Ga 2 Ge 2 O 10 :0.5% Cr 3+ ), zinc sulfide doped with copper and/or cobalt (e.g., ZnS:Cu, Co), strontium aluminate doped with other dopants, such as europium, dysprosium, and/or boron (e.g., SrAl 2 O 4 :Eu 2+ , Dy 3+ ,B 3+ ), calcium aluminate doped with europium, dysprosium, and/or neodymium (e.g., CaAl 2 O 4 :Eu 2+ , Dy 3+ , Nd 3+ ), yttrium oxide sulfide doped with europium, magnesium, and/or titanium, (e.g., Y 2 O 2 S:Eu 3+ , Mg 2+ , Ti 4+ ), and zinc gallogermanates (e.g., Zn 3 Ga 2 Ge 2 O 10 :0.5% Cr 3+ ). In some instances, the phosphorescent material may be provided in granular or other particle form. Such grain or particle may have a maximum diameter of between about 1 and about 5 micrometer. In some instances, the grain or particle may have a maximum diameter of at least about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 micrometers or more. Alternatively or in addition, the grain or particle may have a maximum diameter of at most about 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0 micrometers or less. 
     In some instances, the afterglow (e.g., emitted optical energy) emitted by the phosphorescent material can last at least about 1 hour (hr), 2 hr, 3 hr, 4 hr, 5 hr, 6 hr, 7 hr, 8 hr, 9 hr, 10 hr, 11 hr, 12 hr, 1 day, 2 days, 3 days, 4 days, 1 week, 2 weeks, 3 weeks, or longer. In some instances, the phosphorescent material can store and/or discharge energy for at least about 1 hr, 2 hr, 3 hr, 4 hr, 5 hr, 6 hr, 7 hr, 8 hr, 9 hr, 10 hr, 11 hr, 12 hr, 1 day, 2 days, 3 days, 4 days, 1 week, 2 weeks, 3 weeks, or longer. Alternatively, the afterglow emitted by the phosphorescent material (or energy stored by the phosphorescent material) can last for shorter durations. 
     In some instances, the phosphorescent material  102  may absorb optical energy at the first wavelength from any direction. In some instances, the phosphorescent material may emit optical energy at the second wavelength in any direction (e.g., from a surface of the phosphorescent material). 
     The assembly  100  can comprise one or a plurality of photovoltaic cells (e.g., photovoltaic cell  103 ) that are electrically connected in series and/or in parallel. The photovoltaic cell  103  can be a panel, cell, module, and/or other unit. For example, a panel can comprise one or more cells all oriented in a plane of the panel and electrically connected in various configurations. For example, a module can comprise one or more cells electrically connected in various configurations. The photovoltaic cell  103 , or solar cell, can be configured to absorb optical energy and generate electrical power from the absorbed optical energy. In some instances, the photovoltaic cell can be configured to absorb optical energy at a wavelength or a range of wavelengths that is capable of being emitted by the phosphorescent material  102 . The photovoltaic cell can have a single band gap that is tailored to the wavelength (or range of wavelengths) of the optical energy that is emitted by the phosphorescent material. Beneficially, this may increase the efficiency of the energy storage system of the photon battery assembly  100 . For example, for strontium aluminate doped with europium as the phosphorescent material, the photovoltaic cell can have a band gap that is tailored to the green light wavelength (e.g., 500˜520 nm). Similarly, the light source  101  can be tailored to emit ultraviolet range wavelengths (e.g., 20 nm to 400 nm). Alternatively, the photovoltaic cell can be configured to absorb optical energy at other wavelengths (or ranges of wavelengths) in the electromagnetic spectrum (e.g., infrared, visible, ultraviolet, x-rays, etc.). 
     In some embodiments, organic light emitting diodes (OLEDs) can replace the phosphorescent material  102  in the photon battery assembly  100 . In some embodiments, OLEDs can replace both the light source  101  and the phosphorescent material. OLEDs can be capable of electro-phosphorescence, where quasi particles in the lattice of the diodes store potential energy from an electric power source and release such energy over time in the form of optical energy at visible wavelengths (e.g., 400 nm to 700 nm). For example, OLEDs can be powered by an electrical power source, which may be external or internal to the photon battery assembly  100 . A light-emitting surface of the OLEDs can interface with a light-absorbing surface of the photovoltaic cell  103  to complete the photon battery assembly. For example, with OLEDs, the photovoltaic cell can have a band gap that is tailored to the visible wavelength range (e.g., 400˜700 nm). 
     The photovoltaic cell  103  may have any thickness. For example, the photovoltaic cell may have a thickness of about 20 micrometers. In some instances, the photovoltaic cell may have a thickness of at least about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 40, 50, 60, 70, 80, 90, 100 micrometers or more. Alternatively, the photovoltaic cell may have a thickness of at most about 100, 90, 80, 70, 60, 50, 40, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10 micrometers or less. 
       FIG. 2  shows a photon battery in communication with an electrical load. The photon battery  201  can power an electrical load  202 . The photon battery and the electrical load can be in electric communication, such as via an electric circuit. While  FIG. 2  shows a circuit, the circuit configuration is not limited to the one shown in  FIG. 2 . The electrical load can be an electrical power consuming device. The electrical load can be an electronic device, such as a personal computer (e.g., portable PC), slate or tablet PC (e.g., Apple® iPad, Samsung® Galaxy Tab), telephone, Smart phone (e.g., Apple® iPhone, Android-enabled device, Blackberry®), or personal digital assistant. The electronic device can be mobile or non-mobile. The electrical load can be a vehicle, such as an automobile, electric car, train, boat, or airplane. The electrical load can be a power grid. In some cases, the electrical load can be another battery or other energy storage system which is charged by the photon battery. In some instances, the photon battery can be integrated in the electrical load. In some instances, the photon battery can be permanently or detachably coupled to the electrical load. For example, the photon battery can be removable from the electrical load. 
     In some cases, a photon battery  201  can power a plurality of electrical loads in series or in parallel. In some cases, a photon battery can power a plurality of electrical loads simultaneously. For example, the photon battery can power 2, 3, 4, 5, 6, 7, 8, 9, 10 or more electrical loads simultaneously. In some cases, a plurality of photon batteries, electrically connected in series or in parallel, can power an electrical load. In some cases, a combination of one or more photon batteries and one or more other types of energy storage systems (e.g., lithium ion battery, fuel cell, etc.) can power one or more electrical loads. 
       FIG. 3  shows an exemplary photon battery assembly in application. Any and all circuits illustrated in  FIG. 3  are not limited to such circuitry configurations. A photon battery assembly  300  can be charged by a power source  304  and discharge power to an electrical load  306 . The photon battery assembly can comprise a light source  301 , such as a LED or a set of LEDs. The light source can be in electrical communication with the power source  304  through a port  305  of the light source. For example, the power source and the port  305  can be electrically connected via a circuit. The power source  304  may be external or internal to the photon battery assembly  300 . The power source can be a power supplying device, such as another energy storage system (e.g., another photon battery, lithium ion battery, supercapacitor, fuel cell, etc.). The power source can be an electrical grid. 
     The light source  301  can receive electrical energy and emit optical energy at a first wavelength, such as via a light-emitting surface of the light source. The light-emitting surface can be adjacent to a phosphorescent material  302 . The light source can be in optical communication with the phosphorescent material. The phosphorescent material can be configured to absorb optical energy at the first wavelength and, after a time delay, emit optical energy at a second wavelength. In some cases, the rate of emission of the optical energy at the second wavelength can be slower than the rate of absorption of the optical energy at the first wavelength. An advantage of this difference in rate is the ability of the phosphorescent material to release energy at a slower rate than absorbing such energy, thus storing the energy during such time delay. In some instances, the phosphorescent material can store and/or discharge energy for at least about 1 hr, 2 hr, 3 hr, 4 hr, 5 hr, 6 hr, 7 hr, 8 hr, 9 hr, 10 hr, 11 hr, 12 hr, 1 day, 2 days, 3 days, 4 days, 1 week, 2 weeks, 3 weeks, or longer. 
     The photon battery assembly can comprise a photovoltaic cell  303 . The photovoltaic cell can be configured to absorb optical energy at the second wavelength, such as via a light-absorbing surface of the photovoltaic cell. The photovoltaic cell can be in optical communication with the phosphorescent material  302 . The light-absorbing surface of the photovoltaic cell can be adjacent to the phosphorescent material. The photovoltaic cell can generate electrical power from the optical energy absorbed. The electrical power generated by the photovoltaic cell can be used to power an electrical load  306 . The photovoltaic cell can be in electrical communication with the electrical load through a port  307  of the photovoltaic cell. For example, the electrical load and the port  307  can be electrically connected via a circuit. 
     The energy stored by the photon battery assembly  300  can be charged and/or recharged multiple times. The power generated by the photon battery assembly can be consumed multiple times. The photon battery assembly can be charged and/or recharged by supplying electrical energy (or power) to the light source  301 , such as through the port  305 . The photon battery assembly  300  can discharge power by directing electrical power generated by the photovoltaic cell to the electrical load  306 , such as through the port  307 . For example, the photon battery assembly  300  can last (e.g., function for) at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 500, 1000, 10 4 , 10 5 , 10 6 , or more recharge (or consumption) cycles. 
     The photon battery assembly  300  may provide superior charging rates to those of conventional chemical batteries, for example, on the order of 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 times faster or more. For example, the photon battery assembly can charge at a speed of at least about 800 watts per cubic centimeters (W/cc), 850 W/cc, 900 W/cc, 1000 W/cc, 1050 W/cc, 1100 W/cc, 1150 W/cc, 1200 W/cc, 1250 W/cc, 1300 W/cc, 1350 W/cc, 1400 W/cc, 1450 W/cc, 1500 W/cc or greater. Alternatively, the photon battery assembly can charge at a speed of less than about 800 W/cc. The photon battery assembly may provide superior lifetimes to those of conventional chemical batteries, for example, on the order of 2, 3, 4, 5, 6, 7, 8, 9, 10 times more recharge cycles or more. 
     The photon battery assembly  300  may be stable and function effectively in relatively cold operating temperature conditions. For example, the photon battery assembly may function stably in operating temperatures as low as about −55° Celsius (° C.) and as high as about 65° C. The photon battery assembly may function stably in operating temperatures lower than about −55° C. and higher than about 65° C. In some instances, the photon battery assembly may function stably under any operating temperatures for which the light source (e.g., LEDs) functions stably. The photon battery assembly may not generate excess operating heat. 
       FIG. 4A  illustrates a photon battery assembly with a waveguide. A photon battery assembly  400  can comprise a light source  401 , a phosphorescent material  402 , a photovoltaic cell (not shown), and a waveguide  404 . The waveguide may be adjacent to the light source and the phosphorescent material. For example, the waveguide may be sandwiched by the light source and the phosphorescent material. In other examples, as shown in  FIG. 4A , some surfaces of the waveguide may be adjacent to the phosphorescent material and some surfaces of the waveguide may be adjacent to the light source. In some instances, additionally, the waveguide may be adjacent to the photovoltaic cell. The configuration of the photon battery assembly with the waveguide is not limited to  FIG. 4A . 
     Regardless of contact between the phosphorescent material  402  and waveguide  404 , the phosphorescent material and the waveguide may be in optical communication. Regardless of contact between the light source  401  and waveguide, the light source and the waveguide may be in optical communication. In some instances, regardless of contact between the photovoltaic cell and waveguide, the photovoltaic cell and the waveguide may be in optical communication. 
     The waveguide  404  may or may not be contacting the light source  401 . If the waveguide and the light source are in contact, the waveguide can interface a light-emitting surface of the light source. The waveguide and the light source can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the light source and/or a support carrying the waveguide may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the waveguide may have adhesive and/or cohesive properties and adhere to the light source without an independent fastening mechanism. The waveguide and the light source can be permanently or detachably fastened together. For example, the waveguide and the light source can be disassembled from and reassembled into the photon battery assembly  400  without damage (or with minimal damage) to waveguide and/or the light source. Alternatively, while in contact, the waveguide and the light source may not be fastened together. 
     If the waveguide  404  and the light source  401  are not in contact, the waveguide can otherwise be in optical communication with a light-emitting surface of the light source. For example, the waveguide can be positioned in an optical path of light emitted by the light-emitting surface of the light source. In some instances, there can be an air gap between the waveguide and the light source. In some instances, there can be another intermediary layer, such as a solid material (e.g., glass, plastic, etc.) and/or another waveguide, between the waveguide and the light source. The intermediary layer can be air and/or other fluid. The intermediary layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the waveguide and the light source. In some instances, the waveguide may be in optical communication with one or more surfaces of the waveguide. For example, the light source may comprise an array and/or row of LEDs that are in optical communication with one or more surfaces of the waveguide. The waveguide may receive light from the light source from any surface. In some instances, a surface of the waveguide in optical communication with a surface of a light source may be parallel, perpendicular, or at any angle whether in direct contact or not in contact. Either or both surfaces may be flat. Either or both surfaces may be angled and/or have a curvature (e.g., convex, concave). Either or both surfaces may have any surface profile. 
     The waveguide  404  may or may not be contacting the phosphorescent material  402 . If the waveguide and the phosphorescent material are in contact, the waveguide can interface a light-absorbing surface of the phosphorescent material. The waveguide and the phosphorescent material can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the phosphorescent material and/or a support carrying the waveguide may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the waveguide may have adhesive and/or cohesive properties and adhere to the phosphorescent material without an independent fastening mechanism. In some instances, the phosphorescent material may have adhesive and/or cohesive properties and adhere to the waveguide without an independent fastening mechanism. For example, the phosphorescent material may be painted or coated on a light-emitting surface of the waveguide. The waveguide and the phosphorescent material can be permanently or detachably fastened together. For example, the waveguide and the phosphorescent material can be disassembled from and reassembled into the photon battery assembly  400  without damage (or with minimal damage) to waveguide and/or the phosphorescent material. Alternatively, while in contact, the waveguide and the phosphorescent material may not be fastened together. 
     If the waveguide  404  and the phosphorescent material  402  are not in contact, the waveguide can otherwise be in optical communication with a light-absorbing surface of the phosphorescent material. For example, the phosphorescent material can be positioned in an optical path of light emitted by the light-emitting surface of the waveguide. In some instances, there can be an air gap between the waveguide and the phosphorescent material. In some instances, there can be another intermediary layer, such as another waveguide, between the waveguide and the phosphorescent material. The intermediary layer can be air or other fluid. The intermediary layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the waveguide and the phosphorescent material. In some instances, the waveguide may be in optical communication with one or more surfaces of the phosphorescent material. The phosphorescent material may receive light from the waveguide from any surface. In some instances, a surface of the waveguide in optical communication with a surface of a phosphorescent material may be parallel, perpendicular, or at any angle, whether in direct contact or not in contact. Either or both surfaces may be flat. Either or both surfaces may be angled and/or have a curvature (e.g., convex, concave). Either or both surfaces may have any surface profile. 
     The waveguide  404  may be configured to direct waves at a first wavelength emitted from the light source  401  to the phosphorescent material  402 . Beneficially, the waveguide may deliver optical energy from the light source to the phosphorescent material with great efficiency and minimal loss of optical energy (or other forms of energy). The waveguide may provide optical communication between the light source and distributed volumes of the phosphorescent material where otherwise some volumes of phosphorescent material would not be in optical communication with the light source, allowing for flexible arrangements of the light source relative to the phosphorescent material. For example, without waveguides, the optical energy at the first wavelength emitted from the light source may be absorbed most efficiently by the immediately adjacent volume of phosphorescent material (relative to the light source or otherwise in immediate optical communication with the light source), such as at the phosphorescent material-light source interface. However, once such immediately adjacent phosphorescent material absorbs the optical energy at the first wavelength, it may no longer have capacity to receive further optical energy and/or prevent other volumes of phosphorescent material (further downstream in the optical path) from absorbing such optical energy. While large surface area interface between the phosphorescent material and the light source may facilitate efficient optical energy delivery from the light source to the phosphorescent material, this may be impractical when constructing compact energy storage systems. By implementing waveguides to facilitate optical communication between the light source and the phosphorescent material, different volumes of the phosphorescent material may evenly absorb the optical energy from the light source even if such phosphorescent material and the light source are not immediately adjacent. 
     The waveguide  404  may have a maximum dimension (e.g., width, length, height, radius, diameter, etc.) of at least about 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 200 micrometers, 300 micrometers, 400 micrometers, 500 micrometers, 600 micrometers, 700 micrometers, 800 micrometers, 900 micrometers, 1 millimeter (mm), 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 1 centimeter (cm), 2 cm, 3 cm, 4 cm, 5 cm, 10 cm, 15 cm, 20 cm, 30 cm, 40 cm, 50 cm or more. Alternatively or in addition, the waveguide may have a maximum dimension of at most about 50 cm, 40 cm, 30 cm, 20 cm, 15 cm, 10 cm, 5 cm, 4 cm, 3 cm, 2 cm, 1 cm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1 mm, 900 micrometers, 800 micrometers, 700 micrometers, 600 micrometers, 500 micrometers, 400 micrometers, 300 micrometers, 200 micrometers, 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, 60 micrometers, 50 micrometers, 40 micrometers, 30 micrometers, 20 micrometers, 10 micrometers, or less. The waveguide may be square, rectangular (e.g., having an aspect ratio for length to width of about 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:3, 1:4, 1:5, 1:10, etc.), or any other shape. The waveguide may comprise material such as plastic or glass. The waveguide may comprise material used in an injection mold. 
     For example, in  FIG. 4A , the optical energy emitted from the light source  401  is directed through the layer of waveguide  404  to reach various locations of the phosphorescent material  402 . As described elsewhere herein, after a time delay, the phosphorescent material  402  may emit optical energy at the second wavelength for absorption by a photovoltaic cell (not shown). The waveguide may comprise one or more reflective surfaces  405  to direct waves from the light source to the phosphorescent material. The one or more reflective surfaces may have increasingly large reflective surfaces in the optical path within the waveguide to allow some waves to be reflected at a first reflective surface for excitation of a first volume of phosphorescent material, and some waves to travel further before being reflected at a second reflective surface for excitation of a second volume of phosphorescent material that is further from the light source than the first volume, and some waves to travel further before being reflected at a third reflective surface for excitation of a third volume of phosphorescent material that is further than the second volume, and so on. There may be any number of reflective surfaces in the waveguide. For example, there may be at least about 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, or more reflective surfaces. Alternatively or in addition, a single reflective surface may gradually increase surface area, such as in a conical shape, in the optical path within the waveguide to achieve a similar outcome. 
     In some instances, the waveguide may be adjacent to the phosphorescent material from a first surface, and adjacent to the light source from a second surface, wherein the first surface and the second surface are substantially orthogonal. The one or more reflective surfaces may be configured to direct waves in a substantially orthogonal direction such as to receive from the light source from the second surface and to transmit through the first surface. Alternatively or in addition, the first surface and the second surface may be at any other angle and the one or more reflective surfaces may be configured to direct waves in the other angle, such as to receive from the light source from the second surface and to transmit through the first surface. As illustrated in  FIG. 4A , the waveguide may be adjacent to a plurality of layers of phosphorescent material (e.g., interfacing different surfaces of the waveguide). The one or more reflective surfaces may be configured to direct waves received from the light source to the plurality of layers of phosphorescent material by reflecting the waves (e.g., light) to the plurality of layers. 
     In some instances, alternative to or in addition to the light source  401 , the photon battery assembly  400  may be charged (or the phosphorescent material excited) wirelessly. In some embodiments, a photon battery assembly can comprise the phosphorescent material  402 , a photovoltaic cell (not shown), and the waveguide  404 , without having the light source  401  integrated in the assembly. For example, the light source  401  (illustrated in  FIG. 4A ) can be remote and detached from the other components. The light source may be driven by a power source that is separate and/or detached from the photon battery assembly that it charges. Such remote light source can be configured to provide optical energy to the assembly to achieve wireless charging of the assembly. Regardless of where the light source  401  is disposed with respect to the assembly and/or the waveguide, the light source may be in optical communication with the waveguide and/or the phosphorescent material to provide optical energy for excitation of the phosphorescent material. The remote light source can be configured to provide optical energy at a higher energy level than the optical energy emitted by the phosphorescent material. For example, where the phosphorescent material is strontium aluminate, the remote light source may provide optical energy at wavelengths that is shorter than the emission wavelength of about 520 nanometers. For example, the remote light source may provide waves at wavelengths between about 300 nanometers to about 470 nanometers. The remote light source may provide such optical energy via LED, lasers, or other optical beams, as described elsewhere herein. In some instances, a photon battery assembly configuration may maximize (or otherwise) increase the exposed surface area of one or more waveguides and/or the phosphorescent material to facilitate such wireless charging. Beneficially, the compactness and the transportability of the photon battery assemblies described herein may be greatly increased by allowing for wireless charging. Further, such wireless charging may allow for fast charging, optical charging, and on-demand charging, as well as benefit from the general widespread availability of charging sources (e.g., availability of light sources). Any of the photon battery assemblies may be configured for wireless charging, either in addition to wired (e.g., integrated) light source charging, or alternative to integrated light source charging. 
     In some instances, the waveguide may be coated at one or more surfaces. Otherwise, the waveguide may be adjacent to and/or in contact with another layer at one or more surfaces. For example, the waveguide may be coated at one or more surfaces that interfaces the phosphorescent material  402 . An example coating configuration is shown in  FIG. 4B . A photon battery assembly can comprise a light source (not shown), a phosphorescent material  452 , a photovoltaic cell  453 , and a waveguide  451 , which has a coating  454  on one or more of its surfaces that interfaces the phosphorescent material. The waveguide may be adjacent to the light source and the phosphorescent material, as described elsewhere herein. 
     The coating  454  may be disposed between the waveguide  451  and the phosphorescent material  452 . In some instances, all surfaces of the waveguide interfacing (or in optical communication with) the phosphorescent material may be covered by the coating. In other instances, a portion of the surfaces interfacing (or in optical communication with) the phosphorescent material may be covered by the coating and a portion of the surfaces interfacing (or in optical communication with) the phosphorescent material may not be covered by the coating. For example, such surfaces may be uncovered by anything and in direct optical communication with the phosphorescent material, or be covered by another coating or another layer (e.g., glass, another waveguide, etc.) and be in optical communication with the phosphorescent material through the other coating or other layer. In some instances, the other layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there may be a plurality of layers between the waveguide  451  and the phosphorescent material  452 , including the coating  454 . For example, the plurality of layers may include an air gap or other fluid gap, a solid layer (e.g., glass, plastic.), other optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.), and/or any other layer, in any combination, and arranged in any order or sequence. Regardless of coating or waveguide configuration, the phosphorescent material  452  and the waveguide  451  may be in optical communication. 
     The waveguide  404  may or may not be contacting the coating  454 . The waveguide and the coating can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the coating and/or a support carrying the waveguide may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the coating may have adhesive and/or cohesive properties and adhere to the waveguide without an independent fastening mechanism. In some instances, the waveguide may have adhesive and/or cohesive properties and adhere to the coating without an independent fastening mechanism. For example, the coating may be painted or coated on a surface of the waveguide. The waveguide and the coating can be permanently or detachably fastened together. For example, the waveguide and the coating can be disassembled from and reassembled into the photon battery assembly without damage (or with minimal damage) to waveguide and/or the coating. Alternatively, while in contact, the waveguide and the coating may not be fastened together. 
     The coating  454  may be a dichroic coating or comprise other optical filter(s). For example, the coating may be configured to allow waves at certain first wavelength(s) (e.g., longer wavelength) in to excite the phosphorescent material  452 , but reflect the waves at certain second wavelength(s) (e.g., shorter wavelength). For example, waves with longer wavelength(s) may be allowed to reach the phosphorescent material through the coating, and waves with shorter wavelengths(s) emitted by the phosphorescent material may be reflected by the coating and kept within the phosphorescent material layer to (i) increase the likelihood that such waves with shorter wavelengths are incident upon the photovoltaic cell  453 , and (ii) prevent such waves from entering the waveguide  451  and generating undesired heat. 
     The coating  454  may have any thickness. For example, the coating may be between 0.5 micrometers and 5 micrometers. In some instances, the coating may be at least about 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 micrometers or more in thickness. Alternatively or in addition, the coating may be at most about 5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5 micrometers or less in thickness. 
     Alternatively or in addition to the coating  454 , the waveguide  451  may comprise a surface feature  455  (or multiple features) to facilitate the direction of waves towards a certain direction, and/or increase the uniformity of the direction in which waves are directed. For example, one or more surfaces of the waveguide may comprise physical structures or features, such as grooves, troughs, indentations, hills, pillars, walls, and/or other structures or features. In an example, a bottom surface of the waveguide may comprise one or more grooves formed inwards the waveguide such that waves from the light source are uniformly reflected in a direction towards the phosphorescent material to excite the phosphorescent material. Such grooves (and/or other physical structures or features) may be patterned into the waveguide. The patterns may be regular or irregular. For example, the grooves may be spaced at regular intervals or irregularly spaced. In some instances, such grooves (and/or other physical structures or features) may be discrete features. The physical structure or feature may be formed by any mechanism, such as mechanical machining. In some instances, diamond turning can be used to etch or cut the physical structures or features (e.g., grooves) into the waveguide. In some instances, one or more physical features may be integral to the waveguide. In some instances, one or more physical features may be external to, and/or otherwise coupled/attached to the waveguide by any fastening mechanism described elsewhere herein. Alternatively or in addition to the coating  454  and/or the surface feature  455 , the waveguide  451  may further comprise surface marking to facilitate the direction of waves towards a certain direction. For example, one or more surfaces of the waveguide may comprise painted markings having certain optical properties that facilitating the scattering of waves in a certain direction. For example, such painted markings may be white painted dots that facilitate scatter of light towards the phosphorescent material to excite the phosphorescent material. The waveguide may comprise any number of such painted dots (or other surface markings). The waveguide may comprise any type of painted markings, including other colored dots. The markings may form a pattern. The patterns may be regular or irregular. For example, the dots may be spaced at regular intervals or irregularly spaced. In some instances, such dots may be discrete markings. 
     Any of the photon battery assemblies described herein may comprise a waveguide in optical communication with an optical filter, such as the dichroic coating described with respect to  FIG. 4B , or comprise a waveguide comprising the physical features and/or markings described with respect to  FIG. 4B . For example, the photon battery assembly  100  of  FIG. 1  may comprise a waveguide (not shown) in optical communication with a coating disposed between the waveguide and the phosphorescent material  102 . For example, the photon battery assembly  400  of  FIG. 4A  may comprise a coating disposed between the waveguide  404  and the phosphorescent material  402 . 
       FIG. 5  illustrates another photon battery assembly with a waveguide. A photon battery assembly  500  can comprise a light source (not shown), a phosphorescent material  502 , a photovoltaic cell  503 , and a waveguide  506 . The waveguide may be adjacent to the photovoltaic cell and the phosphorescent material. For example, the waveguide may be sandwiched by the photovoltaic cell and the phosphorescent material. In other examples, as shown in  FIG. 5 , some surfaces of the waveguide may be adjacent to the phosphorescent material and some surfaces of the waveguide may be adjacent to the photovoltaic cell. In some instances, additionally, the waveguide may be adjacent to the light source. The configuration of the photon battery assembly with the waveguide is not limited to  FIG. 5 . 
     Regardless of contact between the phosphorescent material  502  and waveguide  506 , the phosphorescent material and the waveguide may be in optical communication. Regardless of contact between the photovoltaic cell  503  and waveguide, the photovoltaic cell and the waveguide may be in optical communication. In some instances, regardless of contact between the light source and waveguide, the light source and the waveguide may be in optical communication. 
     The waveguide  506  may or may not be contacting the photovoltaic cell  503 . If the waveguide and the photovoltaic cell are in contact, the waveguide can interface a light-absorbing surface of the photovoltaic cell. The waveguide and the photovoltaic cell can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the photovoltaic cell and/or a support carrying the waveguide may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the waveguide may have adhesive and/or cohesive properties and adhere to the photovoltaic cell without an independent fastening mechanism. The waveguide and the photovoltaic cell can be permanently or detachably fastened together. For example, the waveguide and the photovoltaic cell can be disassembled from and reassembled into the photon battery assembly  500  without damage (or with minimal damage) to waveguide and/or the photovoltaic cell. Alternatively, while in contact, the waveguide and the photovoltaic cell may not be fastened together. 
     If the waveguide  506  and the photovoltaic cell  503  are not in contact, the waveguide can otherwise be in optical communication with a light-emitting surface of the photovoltaic cell. For example, the photovoltaic cell can be positioned in an optical path of light emitted by a light-emitting surface of the waveguide. In some instances, there can be an air gap between the waveguide and the photovoltaic cell. In some instances, there can be another intermediary layer, such as another waveguide, between the waveguide and the photovoltaic cell. The intermediary layer can be air or other fluid. The intermediary layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the waveguide and the photovoltaic cell. 
     The waveguide  506  may or may not be contacting the phosphorescent material  502 . If the waveguide and the phosphorescent material are in contact, the waveguide can interface a light-emitting surface of the phosphorescent material. The waveguide and the phosphorescent material can be coupled or fastened together at the interface, such as via a fastening mechanism. In some instances, a support carrying the phosphorescent material and/or a support carrying the waveguide may be coupled or fastened together at the interface. Examples of fastening mechanisms may include, but are not limited to, form-fitting pairs, hooks and loops, latches, staples, clips, clamps, prongs, rings, brads, rubber bands, rivets, grommets, pins, ties, snaps, velcro, adhesives, tapes, a combination thereof, or any other types of fastening mechanisms. In some instances, the waveguide may have adhesive and/or cohesive properties and adhere to the phosphorescent material without an independent fastening mechanism. In some instances, the phosphorescent material may have adhesive and/or cohesive properties and adhere to the waveguide without an independent fastening mechanism. For example, the phosphorescent material may be painted or coated on the waveguide. The waveguide and the phosphorescent material can be permanently or detachably fastened together. For example, the waveguide and the phosphorescent material can be disassembled from and reassembled into the photon battery assembly  500  without damage (or with minimal damage) to waveguide and/or the phosphorescent material. Alternatively, while in contact, the waveguide and the phosphorescent material may not be fastened together. 
     If the waveguide  506  and the phosphorescent material  502  are not in contact, the waveguide can otherwise be in optical communication with a light-emitting surface of the phosphorescent material. In some instances, there can be another intermediary layer, such as another waveguide, between the waveguide and the phosphorescent material. The intermediary layer can be air or other fluid. The intermediary layer can be a light guide or another layer of optical elements (e.g., lens, reflector, diffusor, beam splitter, etc.). In some instances, there can be a plurality of intermediary layers between the waveguide and the phosphorescent material. 
     The waveguide  506  may be configured to direct waves at a second wavelength emitted from the phosphorescent material  502  to the photovoltaic cell  503 . Beneficially, the waveguide may deliver optical energy from the phosphorescent material to the photovoltaic cell with great efficiency and minimal loss of optical energy (or other forms of energy). The phosphorescent material may emit optical energy at the second wavelength without directional specificity, such as in isotropic emission. The waveguide may provide optical communication between the photovoltaic cell and distributed volumes of the phosphorescent material where otherwise some volumes of phosphorescent material would not be in optical communication with the photovoltaic cell, allowing for flexible arrangements of the photovoltaic cell relative to the phosphorescent material. For example, without waveguides, the optical energy at the second wavelength emitted from the phosphorescent material may be absorbed most efficiently by the immediately adjacent light absorbing surface of the photovoltaic cell, if it reaches the photovoltaic cell at all. The optical energy that is emitted away from the light absorbing surface of the photovoltaic cell may be lost in the process. While large surface area interface between the phosphorescent material and the photovoltaic cell may facilitate efficient optical energy delivery from the phosphorescent material to the photovoltaic cell, this may be impractical and expensive when constructing compact energy storage systems. By implementing waveguides to facilitate optical communication between the photovoltaic cell and the phosphorescent material, the photovoltaic cell may efficiently absorb the optical energy from the phosphorescent material even if they are not immediately adjacent. 
     The waveguide  506  may have a maximum dimension (e.g., width, length, height, radius, diameter, etc.) of at least about 1 millimeter (mm), 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 1 centimeter (cm), 2 cm, 3 cm, 4 cm, 5 cm, 10 cm, 15 cm, 20 cm, 30 cm, 40 cm, 50 cm or more. Alternatively or in addition, the waveguide may have a maximum dimension of at most about 50 cm, 40 cm, 30 cm, 20 cm, 15 cm, 10 cm, 5 cm, 4 cm, 3 cm, 2 cm, 1 cm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1 mm or less. The waveguide may be square, rectangular (e.g., having an aspect ratio for length to width of about 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:3, 1:4, 1:5, 1:10, etc.), or any other shape. The waveguide may comprise material such as plastic or glass. The waveguide may comprise material used in an injection mold. 
     For example, in  FIG. 5 , the optical energy emitted from the phosphorescent material  502  is directed through the layer of waveguide  506  to reach the photovoltaic cell  503 . As described elsewhere herein, the phosphorescent material  502  may have absorbed optical energy at the first wavelength from a light source (not shown), such as in the configuration illustrated in  FIG. 4A . The waveguide  506  may have a refractive index such as to allow for total internal reflection of the optical wave at the second wavelength within the waveguide  506  until such optical energy is transmitted to the photovoltaic cell  503 . The waveguide may have a lower refractive index than any adjacent layer to the waveguide. In some instances, the waveguide may be adjacent to the phosphorescent material from a first surface, and adjacent to the photovoltaic cell from a second surface, wherein the first surface and the second surface are substantially orthogonal. In some instances, the waveguide may be adjacent to a plurality of layers of phosphorescent material (e.g., interfacing different surfaces of the waveguide), and configured to direct waves received from the plurality of layers of phosphorescent material to the photovoltaic cell. 
       FIG. 6  illustrates another photon battery assembly with waveguides. A photon battery assembly  600  can comprise a light source  601 , a phosphorescent material  602 , a photovoltaic cell  603 , a first waveguide  604 , and a second waveguide  606 . In some instances, the first waveguide  604  may correspond to the waveguide  404  described with respect to  FIG. 4 . In some instances, the second waveguide  606  may correspond to the waveguide  506  described with respect to  FIG. 5 . 
     The photon battery assembly  600  may be constructed such that the first waveguide  604  is adjacent to the second waveguide  606 , and the second waveguide is adjacent to the phosphorescent material  602 . The first waveguide and the phosphorescent material may each be adjacent to two surfaces of the second waveguide that are substantially parallel. The first waveguide may be adjacent to the light source  601 . The light source and the second waveguide may be adjacent to two surfaces of the first waveguide that are substantially orthogonal. The second waveguide may be adjacent to the photovoltaic cell  603 . The photovoltaic cell and the phosphorescent material may be adjacent to two surface of the second waveguide that are substantially orthogonal. In some instances, the photovoltaic cell and the light source may be substantially parallel and/or coplanar. The configuration of the photon battery assembly with waveguides is not limited to  FIG. 6 . 
     In operation, the photon battery may be charged via the first waveguide  604  which guides optical energy emitted by the light source  601  at the first wavelength to the phosphorescent material  602 . The optical energy received from the light source may be substantially orthogonally reflected (e.g., via a reflective surface) within the first waveguide to pass through the second waveguide  606  (with minimal energy loss) for even absorption across the phosphorescent material and subsequent excitation. After a time delay, as described elsewhere herein, the phosphorescent material may emit optical energy at a second wavelength. Such emission may be isotropic (e.g., non-direction specific). The emitted optical energy may be directed by the second waveguide, such as via total internal reflection, to the photovoltaic cell for absorption by the photovoltaic cell. Alternatively or in addition, the emitted optical energy may be directed to the photovoltaic cell directly. In some instances, the second waveguide may have a refractive index that is lower than that of the first waveguide and that of the phosphorescent material to allow for total internal reflection. As illustrated in  FIG. 6 , the photon battery may be stacked in a similar configuration. 
       FIG. 7  shows a stack of a plurality of photon battery assemblies. A photon battery assembly can be connected to achieve different desired voltages, energy storage capacities, power densities, and/or other battery properties. For example, an energy storage system  700  may comprise a stack of a first photon battery assembly, a second photon battery assembly, a third photon battery assembly, a fourth photon battery assembly, and so on, which are stacked vertically or horizontally. Each photon battery assembly may comprise (or share) a light source, phosphorescent material, photovoltaic cell, first waveguide, and second waveguide, as described elsewhere herein. While  FIG. 7  shows six photon battery assemblies stacked together, any number of photon battery assemblies can be stacked together in any configuration. For example, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, or more photon battery assemblies can be stacked together. While  FIG. 7  shows a linear grid-like stack in the horizontal and vertical directions, the assemblies can be stacked in different configurations, such as in concentric (or circular) stacks. 
       FIG. 8  shows an exploded view of another configuration for a photon battery assembly stack with hollow core waveguides. A waveguide  806  may comprise a hollow core. For example, the waveguide may be an optical fiber or cable with a hollow core. Alternatively, the waveguide may have a cavity or trench with an opening. The waveguide may have a plurality of cavities or trenches with a plurality of openings. The hollow core (or cavity or trench) may be filled by phosphorescent material  802  such as to form filled cylindrical units. Alternatively, the hollow core may be any shape (e.g., rectangular, triangular, hexagonal, non-polygonal, etc.). The cylindrical units may be linearly stacked, such as in groups of 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 200, or more units. The groups of linearly stacked cylindrical units may be sandwiched on opposing sides by light source panels  801 . In some instances, a single light source panel may stretch along a length of a cylindrical unit. Alternatively, as shown in  FIG. 8 , a plurality of light source panels may be intermittently placed along the length of the single cylindrical unit. In some instances, groups of linearly stacked cylindrical units and the sandwiching light source panels may be stacked in alternating layers. Although this example shows four groups of six linearly stacked cylindrical units alternating with five light source panels for each unit length of cylindrical unit, the stack may be in any configuration (e.g., 25 groups of 7 linearly stacked cylindrical units alternating with 26 light source panels). A photovoltaic cell  803  may be adjacent to the end of the cylindrical units, substantially orthogonal to the lengths of the cylindrical units, and substantially orthogonal to the light source panels. The photon battery assembly may resemble a cuboid shape, as illustrated in  FIG. 8 . The photon battery assembly is not limited to the configuration illustrated in  FIG. 8 . 
     In some instances, the light source panel  801  may comprise a light source (e.g., LED) and a waveguide. The waveguide may correspond to the waveguide  404  described with respect to  FIG. 4  and configured to direct optical energy from the light source to different cylindrical units.  FIG. 9  illustrates a partial cross-sectional side view of the photon battery assembly stack of  FIG. 8 . The optical energy emitted by a light source  901  is directed by one or more reflective surfaces  905  in a first waveguide (e.g., in the light source panel  801 ) to the phosphorescent material  902  in different cylindrical units. The optical energy may pass through a second waveguide  906  (configured to direct optical energy emitted from the phosphorescent material to the photovoltaic cell (not shown)). The first waveguide may comprise increasingly larger reflective surfaces (e.g.,  905 ) in the direction of the optical path of the optical energy emitted by the light source  901  such as to evenly distribute the optical energy to the different cylindrical units (e.g., in the linear stack). 
     Each photon battery assembly can be configured as described in  FIGS. 1-9 . Alternatively, different components of the photon battery assembly (e.g., light source, phosphorescent material, photovoltaic cell, first waveguide, second waveguide, coating, etc.) can be stacked in different configurations (e.g., orders). A plurality of photon battery assemblies can be electrically connected in series, in parallel, or a combination thereof. In some instances, there may be interconnects and/or other electrical components between each photon battery assembly. In some instances, a controller can be electrically coupled to one or more photon battery assemblies and be capable of managing the inflow and/or outflow of power from each or a combination of the battery assemblies. 
       FIG. 10  illustrates a method of storing energy in a photon battery. The method can comprise, at a first operation  1001 , emitting optical energy at a first wavelength (e.g., λ 1 ) from a light source. The optical energy at the first wavelength can be emitted from a light-emitting surface of the light source. The light source can be an artificial light source, such as a LED, laser, or lamp. The light source can be a natural light source. The light source can be powered by an electric power source, such as another energy storage device (e.g., battery, supercapacitors, capacitors, fuel cells, etc.) or another power supply (e.g., electrical grid). 
     At a second operation  1002 , a phosphorescent material that is adjacent to the light source can absorb the optical energy at the first wavelength. The optical energy may be directed from the light source to the phosphorescent material via a first waveguide. For example, the phosphorescent material can be adjacent to the light-emitting surface of the light source. In some instances, the first wavelength can be an ultraviolet wavelength (e.g., 20-400 nm). 
     At a next operation  1003 , after a time delay, the phosphorescent material can emit optical energy at a second wavelength (e.g., λ 2 ). In some instances, the first wavelength can be a visible wavelength (e.g., 400-700 nm). The second wavelength can be greater than the first wavelength. That is, the optical energy at the first wavelength can be at a higher energy level than the optical energy at the second wavelength. In some instances, the rate of absorption of the optical energy at the first wavelength by the phosphorescent material can be faster than the rate of emission of the optical energy at the second wavelength by the phosphorescent material. 
     At a next operation  1004 , a photovoltaic cell adjacent to the phosphorescent material can absorb the optical energy at the second wavelength that is emitted by the phosphorescent material. The optical energy may be directed from the phosphorescent material to the photovoltaic cell via a second waveguide. For example, a light-absorbing surface of the photovoltaic cell can absorb the optical energy at the second wavelength. In some instances, the photovoltaic cell can be tailored to absorb the wavelength or range of wavelengths that is emitted by the phosphorescent material. In some instances, the light-absorbing surface of the photovoltaic cell can comprise one or more depressions defined by corresponding protrusions to allow for increased interfacial surface area between the phosphorescent material and the photovoltaic cell. 
     At a next operation  1005 , the photovoltaic cell can convert the absorbed optical energy at the second wavelength and generate electrical power. In some instances, the electrical power generated by the photovoltaic cell can be used to power an electrical load that is electrically coupled to the photovoltaic cell. The electrical load can be an electronic device, such as a mobile phone, tablet, or computer. The electrical load can be a vehicle, such as a car, boat, airplane, or train. The electrical load can be a power grid. In some instances, at least some of the electrical power generated by the photovoltaic cell can be used to power the light source, such as when no electrical load is connected to the photovoltaic cell. In some instances, at least some of the electrical power generated by the photovoltaic cell can be used to charge a rechargeable battery (e.g., lithium ion battery), such as when no electrical load is connected to the photovoltaic cell. The rechargeable battery can in turn be used to power the light source. Beneficially, a photon battery assembly used in this method can be at least in part self-sustaining and prevent loss of energy from the system (e.g., other than from inefficient conversion of energy). 
       FIG. 11  shows a computer control system. The present disclosure provides computer control systems that are programmed to implement methods of the disclosure. A computer system  1101  is programmed or otherwise configured to regulate one or more circuitry in a photon battery assembly, in accordance with some embodiments discussed herein. For example, the computer system  1101  can be a controller, a microcontroller, or a microprocessor. In some cases, the computer system  1101  can be an electronic device of a user or a computer system that is remotely located with respect to the electronic device. The electronic device can be a mobile electronic device. The computer system  1101  can be capable of sensing the connection(s) of one or more electrical loads with a photon battery assembly, the connection(s) of one or more rechargeable batteries with a photon battery assembly, and/or the connection(s) of a photovoltaic cell and a light source within a photon battery assembly. The computer system  1101  may be capable of managing the inflow and/or outflow of power from each or a combination of photon battery assemblies electrically connected in series or in parallel, and in some cases, individually or collectively electrically communicating with a power source and/or an electrical load. The computer system  1101  may be capable of computing a rate of discharge of power from the photon battery and/or a rate of consumption of power by an electrical load. For example, the computer system may be based on such computation, determine whether and how to direct power discharged from a photovoltaic cell to a light source, an external battery (e.g., lithium ion battery), and/or an electrical load. The computer system may be capable of adjusting or regulating a voltage or current of power input and/or power output of the photon battery. The computer system  1101  may be capable of adjusting and/or regulating different component settings. For example, the computer system may be capable of adjusting or regulating a brightness, intensity, color (e.g., wavelength, frequency, etc.), pulsation period, or other optical characteristics of a light emitted by a light source in the photon battery assembly. For example, the computer system may be configured to adjust a light emission setting from a light source depending on the type of phosphorescent material used in the photon battery. 
     For example, the computer system  1101  can be capable of regulating different charging and/or discharging mechanisms of a photon battery assembly. The computer system may turn on an electrical connection between a light source and a power supply to start charging the photon battery assembly. The computer system may turn off an electrical connection between the light source and the power supply to stop charging the photon battery assembly. The computer system may turn on or off an electrical connection between a photovoltaic cell and an electrical load. In some instances, the computer system may be capable of detecting a charge level (or percentage) of the photon battery assembly. The computer system may be capable of determining when the assembly is completely charged (or nearly completely charged) or discharged (or nearly completely discharged). In some instances, the computer system may be capable of maintaining a certain range of charge level (e.g., 5%˜95%, 10%˜90%, etc.) of the photon battery assembly, such as to maintain and/or increase the life of the photon battery assembly, which complete charge or complete discharge can detrimentally shorten. 
     The computer system  1101  includes a central processing unit (CPU, also “processor” and “computer processor” herein)  1105 , which can be a single core or multi core processor, or a plurality of processors for parallel processing. The computer system  1101  also includes memory or memory location  1110  (e.g., random-access memory, read-only memory, flash memory), electronic storage unit  1115  (e.g., hard disk), communication interface  1120  (e.g., network adapter) for communicating with one or more other systems, and peripheral devices  1125 , such as cache, other memory, data storage and/or electronic display adapters. The memory  1110 , storage unit  1115 , interface  1120  and peripheral devices  1125  are in communication with the CPU  1105  through a communication bus (solid lines), such as a motherboard. The storage unit  1115  can be a data storage unit (or data repository) for storing data. The computer system  1101  can be operatively coupled to a computer network (“network”)  1130  with the aid of the communication interface  1120 . The network  1130  can be the Internet, an internet and/or extranet, or an intranet and/or extranet that is in communication with the Internet. The network  1130  in some cases is a telecommunication and/or data network. The network  1130  can include one or more computer servers, which can enable distributed computing, such as cloud computing. The network  1130 , in some cases with the aid of the computer system  1101 , can implement a peer-to-peer network, which may enable devices coupled to the computer system  1101  to behave as a client or a server. 
     The CPU  1105  can execute a sequence of machine-readable instructions, which can be embodied in a program or software. The instructions may be stored in a memory location, such as the memory  1110 . The instructions can be directed to the CPU  1105 , which can subsequently program or otherwise configure the CPU  1105  to implement methods of the present disclosure. Examples of operations performed by the CPU  1105  can include fetch, decode, execute, and writeback. 
     The CPU  1105  can be part of a circuit, such as an integrated circuit. One or more other components of the system  1101  can be included in the circuit. In some cases, the circuit is an application specific integrated circuit (ASIC). 
     The storage unit  1115  can store files, such as drivers, libraries and saved programs. The storage unit  1115  can store user data, e.g., user preferences and user programs. The computer system  1101  in some cases can include one or more additional data storage units that are external to the computer system  1101 , such as located on a remote server that is in communication with the computer system  1101  through an intranet or the Internet. 
     The computer system  1101  can communicate with one or more local and/or remote computer systems through the network  1130 . For example, the computer system  1101  can communicate with all local energy storage systems in the network  1130 . In another example, the computer system  1101  can communicate with all energy storage systems within a single assembly, within a single housing, and/or within a single stack of assemblies. In other examples, the computer system  1101  can communicate with a remote computer system of a user. Examples of remote computer systems include personal computers (e.g., portable PC), slate or tablet PC&#39;s (e.g., Apple® iPad, Samsung® Galaxy Tab), telephones, Smart phones (e.g., Apple® iPhone, Android-enabled device, Blackberry®), or personal digital assistants. The user can access the computer system  1101  via the network  1130 . 
     Methods as described herein can be implemented by way of machine (e.g., computer processor) executable code stored on an electronic storage location of the computer system  1101 , such as, for example, on the memory  1110  or electronic storage unit  1115 . The machine executable or machine readable code can be provided in the form of software. During use, the code can be executed by the processor  1105 . In some cases, the code can be retrieved from the storage unit  1115  and stored on the memory  1110  for ready access by the processor  1105 . In some situations, the electronic storage unit  1115  can be precluded, and machine-executable instructions are stored on memory  1110 . 
     The code can be pre-compiled and configured for use with a machine having a processor adapted to execute the code, or can be compiled during runtime. The code can be supplied in a programming language that can be selected to enable the code to execute in a pre-compiled or as-compiled fashion. 
     Aspects of the systems and methods provided herein, such as the computer system  1101 , can be embodied in programming. Various aspects of the technology may be thought of as “products” or “articles of manufacture” typically in the form of machine (or processor) executable code and/or associated data that is carried on or embodied in a type of machine readable medium. Machine-executable code can be stored on an electronic storage unit, such as memory (e.g., read-only memory, random-access memory, flash memory) or a hard disk. “Storage” type media can include any or all of the tangible memory of the computers, processors or the like, or associated modules thereof, such as various semiconductor memories, tape drives, disk drives and the like, which may provide non-transitory storage at any time for the software programming. All or portions of the software may at times be communicated through the Internet or various other telecommunication networks. Such communications, for example, may enable loading of the software from one computer or processor into another, for example, from a management server or host computer into the computer platform of an application server. Thus, another type of media that may bear the software elements includes optical, electrical and electromagnetic waves, such as used across physical interfaces between local devices, through wired and optical landline networks and over various air-links. The physical elements that carry such waves, such as wired or wireless links, optical links or the like, also may be considered as media bearing the software. As used herein, unless restricted to non-transitory, tangible “storage” media, terms such as computer or machine “readable medium” refer to any medium that participates in providing instructions to a processor for execution. 
     Hence, a machine readable medium, such as computer-executable code, may take many forms, including but not limited to, a tangible storage medium, a carrier wave medium or physical transmission medium. Non-volatile storage media include, for example, optical or magnetic disks, such as any of the storage devices in any computer(s) or the like, such as may be used to implement the databases, etc. shown in the drawings. Volatile storage media include dynamic memory, such as main memory of such a computer platform. Tangible transmission media include coaxial cables; copper wire and fiber optics, including the wires that comprise a bus within a computer system. Carrier-wave transmission media may take the form of electric or electromagnetic signals, or acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media therefore include for example: a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD or DVD-ROM, any other optical medium, punch cards paper tape, any other physical storage medium with patterns of holes, a RAM, a ROM, a PROM and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave transporting data or instructions, cables or links transporting such a carrier wave, or any other medium from which a computer may read programming code and/or data. Many of these forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution. 
     The computer system  1101  can include or be in communication with an electronic display  1135  that comprises a user interface (UI)  1140  for providing, for example, user control options (e.g., start or terminate charging, start or stop powering an electrical load, route power back to self-charging, etc.). Examples of UI&#39;s include, without limitation, a graphical user interface (GUI) and web-based user interface. 
     Methods and systems of the present disclosure can be implemented by way of one or more algorithms. An algorithm can be implemented by way of software upon execution by the central processing unit  1105 . The algorithm can, for example, change circuitry of a photon battery assembly or a stack of photon battery assemblies based on, for example, sensing the connection(s) of one or more electrical loads with a photon battery assembly, the connection(s) of one or more rechargeable batteries with a photon battery assembly, and/or the connection(s) of a photovoltaic cell and a light source within a photon battery assembly. The algorithm may be capable of managing the inflow and/or outflow of power from each or a combination of photon battery assemblies electrically connected in series or in parallel, and in some cases, individually or collectively electrically communicating with a power source and/or an electrical load. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.