Systems and methods for solar energy management

Systems and methods are provided for solar energy management that can charge a battery from a solar panel as well as operate without a battery, using the same equipment. This multi-modal functionality provides the ability to incrementally increase capacity and extend the availability of electricity from daytime-only to a continuous supply irrespective of solar conditions.

BACKGROUND

Globally, almost 1 billion people live without access to electricity, and another billion have only unreliable access to electricity. These underserved communities living “beyond the grid” are typically among the world's most vulnerable and must rely on dangerous, polluting fuels like kerosene and diesel for daily energy needs. Most solar generators and Off-Grid Solar (OGS) products offered to consumers are unable to meet the needs of the end-user and lack the ability to increase capacity or work interchangeably with other components. Many solutions being deployed today include proprietary parts or are manufactured such that they are difficult to repair. Further, because many products are offered turnkey kits, they are often incorrectly sized for the operational conditions resulting in the battery continually functioning in a state of deficit, which eventually leading to system failure. This result not only leaves the consumer without power, but can also solidifies to the end user a common misconception that solar energy is not a viable option.

With regard to equipment used to covert solar energy to useable electricity, charge controllers are a type of product are widely used in solar power systems and power conversion. The primary purpose of a charge controller is to pull a maximum amount of power from a solar panel or solar cell at any instant in time. A charge controller, sometimes referred to as a charge regulator, generally functions as a voltage and/or current regulator to keep batteries from overcharging by regulating the voltage and current coming from the solar panels and going to the battery. One approach for regulating the charging process is through Maximum Power Point Tracking (MPPT.) The MPPT algorithm charges a battery at a fixed voltage level during this operation. Other types of products typically used with a solar cell are a “PWM Converter” or “DC/DC Converter.” These types of converters receive an input voltage from a solar cell and perform a DC/DC conversion to produce another voltage as an output. While a user can apply the output to a load, a PWM Converter does not charge a battery.

DETAILED DESCRIPTION

Throughout this disclosure, references to components or modules generally refer to items that logically can be grouped together to perform a function or group of related functions. Like reference numerals are generally intended to refer to the same or similar components. Components and modules can be implemented in software, hardware, or a combination of software and hardware. The term “software” is used expansively to include not only executable code, for example machine-executable or machine-interpretable instructions, but also data structures, data stores and computing instructions stored in any suitable electronic format, including firmware, and embedded software. The terms “information” and “data” are used expansively and include a wide variety of electronic information, including executable code; content such as text, video data, and audio data, among others; and various codes or flags. The terms “information,” “data,” and “content” are sometimes used interchangeably when permitted by context. It should be noted that, although for clarity and to aid in understanding, some examples discussed herein might describe specific features or functions as part of a specific component or module, or as occurring at a specific layer of a computing device (for example, a hardware layer, operating system layer, or application layer), those features or functions may be implemented as part of a different component or module or operated at a different layer of a communication protocol stack. Those of ordinary skill in the art will recognize that the systems, apparatuses, devices, and methods described herein can be applied to, or easily modified for use with, other types of equipment, can use other arrangements of computing systems, and can use other protocols, or operate at other layers in communication protocol stacks, than are described.

As described in more detail below, the present disclosure generally relates to power electronic systems, digital controls, and distributed energy conversion. The systems and methods described herein can charge a battery from a solar panel as well as operate without a battery, using the same equipment. Solar energy management systems described herein uniquely can operate both as a photovoltaic (PV) panel power regulator without battery storage as well as a charge controller with battery storage. This multi-modal functionality gives the solar energy management system the ability to incrementally increase capacity and extend the availability of electricity from daytime-only to a continuous supply irrespective of solar conditions. This functionality also allows the system to adapt to individual or situational needs.

Solar energy management systems in accordance with the present disclosure can provide one or more of the following benefits. Example solar energy management systems described herein can produce usable DC and AC electricity from the energy generated by photovoltaic (PV) modules of varying voltages and wattages and can also operate with or without local energy storage. Deploying solar energy management systems without a battery, can allow the cost of the system to decrease dramatically and energy can be used when being generated by the sun. Thus, the solar energy management systems described herein can provide enough electricity for basic or critical functions, such as device charging, refrigeration, low-power telecommunication equipment (WiFi mesh or radio), water pumps, etc., in situations when batteries fail or are unavailable.

The systems of the present disclosure can harness photovoltaic energy from a variety of solar panel types (such as, monocrystalline, polycrystalline, amorphous silicon, thin film, CIGs, and so forth) to produce regulated output voltage and current. In some embodiments, the output voltage generated by the solar energy management system is at 12V DC, 24V DC, or 48V DC with an auxiliary 5 V USB output. Such output(s) can be provided with or without battery/energy storage device. Furthermore, with the addition of a grid-interactive, grid-supporting, grid-forming, or off-grid inverter to the system, can include outputs from 110 to 600 VAC, single phase or three phase at predefined frequencies. If a temporary obstruction like a cloud shades sunlight causing PV panel power to drop, the solar energy management systems can automatically disconnect loads and reconnect when power is restored and stable with programmable disconnect and reconnect set-points.

In some embodiments, solar energy management systems are scalable to generate up to 2400 Watts of power and can be stacked in parallel to provide up to 9600 Watts in generation capacity, with or without an attached battery. Functioning without a battery can be beneficial, as batteries are typically the weakest link of an off-grid energy system and can have relatively short lifespans compared to other components of the energy systems. As the solar energy management systems described herein are operational without a battery, such systems can function as a safety net for off-grid systems, as they can continue to generate energy when solar energy is available, even if the associated storage device fails.

Moreover, as a solar energy management system with PV module(s) can provide power for a user, without requiring the user to procure a battery, overall startup costs for the user can be reduced. Over time, the user can expand system, add energy storage, and increase capacity at any time. Use of the solar energy management system also can beneficially attune the end-user to energy positive habits, which can include the efficient and effective productive use of solar energy, when it is available. Based on these habits, the user may be potentially influenced to select a smaller battery, for example, to extend power usability. In some embodiments, the electronics can be assembled by hand to allow for “field” repair, which may be particularly useful for first responders and relief workers during post-disaster and emergency situations. This configuration can also support ‘ethical electronics repair, reuse, repurposing and recycling’ to benefit local various repair economies in developing countries. As solar energy management systems can be repairable, the amount of Electronic Waste (e-waste), entering the waste stream can beneficially be reduced. Thus, solar energy management systems of the present disclosure can beneficially address usage patterns and conservation, while seeking to minimize total cost of ownership.

FIG. 1schematically depicts an example conversion of solar energy inputs102to various outputs106by a solar energy management system104in accordance with various embodiments. A first operational condition108schematically illustrates the use of the solar energy management system104without a battery112and a second operational condition110schematically illustrates the use of the solar energy management system104with a battery112. As shown, during the first operational condition108, the solar energy management system104works directly from the connected PV panel114. During the second operational condition110, the solar energy management system104is also able to work during conditions with adequate solar power (i.e., daytime) and conditions without adequate solar power (i.e., nighttime), due to the presence of the battery212.

The solar energy management system104can perform a self-introspection routine to determine the current operational conditions. In this regard, the solar energy management system104can determine whether a PV panel114is supplying an input voltage, whether a battery112(or other energy storage device) is attached and supplying an input voltage, or whether both a PV panel114and a battery112are attached. Based on this determination, the solar energy management system104determines whether to operate as a charge controller only, a PWM DC/DC converter only, or a combination of the two.

Solar energy management system in accordance with various embodiments of the present disclosure can be rated at 2 kW of power, with either a 48V DC, 24V DC, or 12V DC output, for example. Additionally, the system can accept batteries of the same voltage. In some implementations, the solar energy management system can have a user defined voltage out that exceeds 48V DC. The programmability functionality can allow for atypical battery voltages up to 400V DC, for example, that typically can be found particularly with battery technologies such as Lithium, for example. Furthermore, some example solar energy management systems limit the output to 80V DC to correspond with the National Electric Code (NEC) regarding Power Optimizers and rapid shut-down requirements for many photovoltaic systems. Moreover, in accordance with various embodiments, solar energy management systems can have the ability to control the charge voltage and current for two different energy storage devices.

As described in more detail below, the solar energy management system can include a control power supply that enables the system to be powered up by either a battery or a PV panel, or both. This dual-power up functionality is generally referred to herein as self-introspection, as the system can determine whether a PV panel is attached, a battery is attached, or both are attached. As the self-inspection routine is enabled by the standalone control power supply, this control power supply is configured to be powered by either a PV panel or a battery, in order to handle various operational scenarios. The self-introspection routine can run constantly, or at least periodically. As such, for example, if a battery is attached subsequent to the initial power-up of the system, the self-introspection routine can detect the battery and change operational mode, as may be required.

Referring now toFIG. 2, one example embodiment of a solar energy management system200is shown. The solar energy management system200is shown electrically coupled to a photovoltaic (PV) panel(s)202and battery storage206. The PV panel(s)202can be any suitable panel delivering an input voltage up to 100V DC; in some embodiments up to 600V DC, or higher. However, it is to be appreciated, that in some operational conditions the PV panel may be disconnected, or otherwise not producing voltage. Additionally, battery storage206may or may not be present.

The solar energy management system200can operate as either a charge controller or a PWM converter. The solar energy management system200can execute decisioning to allow the solar energy management system200to determine whether the system is to operate as a charge controller or as a PWM converter. The solar energy management system200can comprise a control unit208, a buck regulator216, a first current sensor220, an output filter214, a first voltage sensor224, a switch204, a second current sensor226, a second voltage sensor228, and a third voltage sensor236. The solar energy management system200can also include a buck converter230, a low-dropout regulator232, and a plurality of outlets234. The buck converter230can electrically connect a PV panel202and/or the battery206to the plurality of outlets234and the low-dropout regulator232. The buck converter230can be supplied power from the connected PV panel202or a battery206and output a reduced voltage to the plurality of outlets234and the low-dropout regulator232. As shown, the buck converter230generally serves as a stand along control power supply. The solar energy management system200can allow for three modes of operations, providing operation as a combination charge and Pulse Width Modulation (PWM) controller, operation as a charge controller, or operation as a PWM controller, as described in more detail below.

The buck regulator216can ensure the voltage received from the PV panel202can be stepped down. The buck regulator216can be electrically connected to the control unit208and the first current sensor220. The first current sensor220can be operatively coupled to the control unit208and can send information to the control unit208regarding a level of current supplied by PV panel202. The third voltage sensor236can also be operatively coupled to the control unit208and can send information to the control unit208regarding the voltage level supplied by PV panel202. The first current sensor220can additionally electrically connect the buck regulator216to the output filter214. The output filter214can be electrically connected to the first voltage sensor224at a point common coupling. The first voltage sensor224can send information to the control unit208about the voltage level at the point common coupling. The switch204can also be electrically connected to the point common coupling, with the switch204controlled by the control unit208allowing the control unit208to switch between modes by opening or closing the switch.

The second current sensor226and the second voltage sensor228can be connected to the switch204, as shown, each of which provide information to the control unit208. The second current sensor226provides information to the control unit208regarding any current applied by the206battery. The second voltage sensor228provides information to the control unit208regarding any voltage supplied by the206battery.

Table 1, below, provides operational parameters for the example solar energy management system200in accordance with the present disclosure:

The solar energy management system200can operates as a PWM controller when a battery206is not attached. The solar energy management system200can recognize that no battery is present via any suitable type of sensing, such as indirect sensing or direct sensing. For instance, the solar energy management system200can utilize a model-based observer in firmware or as a direct measurement with voltage and or current feedback. This operational mode is referred to herein as “Mode 1,” and schematically shown inFIG. 3A.FIG. 3Bschematically illustrates this operational mode providing a DC output andFIG. 3Cschematically illustrates this operational mode providing a DC output and an AC output.

As shown inFIG. 3A, the buck regulator216receives a voltage from the PV panel202and outputs a lower voltage to the first current sensor220. The first current sensor220then sends to the control unit208information regarding a current level provided by the buck regulator216. Once the control unit208receives information from the first current sensor220, the control unit208can set the switch204to an open state, allowing voltage outputted by the buck regulator216to flow through the first current sensor110and the output filter214to a load attached to the output terminals210, as shown with the arrow250. Thus, in the mode of operation depicted inFIG. 3A, the solar energy management system200operates in Buck mode, creating a lower output voltage versus the input voltage.

Next, the solar energy management system200can operate as a combined charge controller and a PWM DC/DC converter, where the output voltage at the output terminals210is set to a user determined level, such as 12V DC, 24V DC, or 48V DC, with the battery206supplying the power. In some embodiments, the user can define an output that his higher than 48V DC. A control algorithm of the solar energy management system200can utilize a MPPT tracking algorithm to pull optimal amounts of power out of the PV panel202that is attached to the input. Simultaneously, the output voltage at the output terminals210can be is maintained to the level set by the user. This operational mode is referred to herein as “Mode 2,” and schematically shown inFIG. 4A.FIG. 4Bschematically illustrates this operational mode providing a DC output andFIG. 4Cschematically illustrates this operational mode providing a DC output and an AC output.

As shown inFIG. 4A, the buck regulator216receives a voltage from the PV panel202and outputs a lower voltage to the first current sensor220. The first current sensor220then sends information to the control unit208regarding a level of current provided by the buck regulator216. Once the control unit208receives information from the first current sensor220, the control unit208can set the switch204to a closed state, allowing a voltage outputted by the buck regulator216to flow through the first current sensor220and the output filter214to both a load attached to the output terminals210and a battery206that is electrically connected to the solar energy management system200, as shown with the arrows252and254.

The solar energy management system200can also operate as charge controller when the battery206is present. In this operational condition, the PV panel202is either not present or is not producing sufficient voltage levels (i.e. low/no light conditions). When the battery206is present, a switch204of the solar energy management system200can be transitioned to a conductive state (i.e., “closed”) by the control unit208. When the switch204is closed, a power transfer from the battery206to a load attached at output terminals210is facilitated. This operational mode is referred to herein as “Mode 3,” and schematically shown inFIG. 5.

Referring the mode of operation depicted inFIG. 5, in this mode of operation the battery206supplies power to the load via output terminals210in an unregulated fashion. Thus, whatever the voltage the batter206is producing will be present at the output terminals210and usable by the user. The switch204provides overload current protection and undervoltage lockout protection. As such, if the battery voltage decays to an unacceptable low value as monitor by the second voltage sensor228that may damage the battery, the switch204is opened and the battery206is disconnected. Likewise, if the current is excessive, as monitored by the second current sensor226indicating a short circuit or overload condition, the switch204is opened to disconnect the battery206from the circuit. In this mode, power flows from the battery206to the load, as shown by the arrow256. In this example embodiment, the PV panel202(if present) can be selected to have a reverse blocking diode (not shown) in the array.

Furthermore, it is noted that the switch204beneficially allows for pre-charging the output filter214while in Mode 3, which is critical for prevention of over current conditions. While the switch204will allow for PWM operation to “softly charge” the output filter214of the buck regulator, shown as a point of common coupling (PCC), the switch204is to operate as a DC/DC converter while in operation Mode 3.

The multi-modal operation of the solar energy management system200can beneficially enable user familiarity “ramp up” over time. First, a user can operate the solar energy management system200without connecting a battery206. During this type of use, the user can develop familiarity and comfort with the system. Next, as familiarity with the system advances, the user can incrementally add one or more batteries206to the system. Thus, the solar energy management system200beneficially can allow users to develop cognitive confidence over time and allow the user to utilize more sophisticated solar management techniques as their comfort level increases.

The solar energy management system200is flexible with regard to input power source. In this regard, the solar energy management system200can be powered up without requiring a battery206being attached to the system. This flexibility is provided by an auxiliary DC/DC converter, shown as a buck convertor230on a power board212, which can process inputs from the PV panel202and inputs from the battery input206. The power board212can perform a logical OR operation on both of these voltages, thereby allowing either power source to drive the control unit208, as provide power to the plurality of outlets234.

The solar energy management system200can allow for the arbitrary insertion of an energy storage device. Specifically, once a battery input is detected, the switch204can be controlled to either soft start the output filter capacitors214of a buck regulator216, assuming they are of a low value with an input from a PV panel202not present. If the output filter capacitors214are charged, the switch204can be closed. The system can charge the output capacitors214appropriately when between these operational conditions.

In accordance with various embodiments, the solar energy management system200can allow for user protection in the various modes of operation. In particular, the conditions of overcurrent and undervoltage at the user load point, designated as output terminals110inFIGS. 2-5, can be protected for overcurrent and undervoltage irrespective of operational conditions.

Referring now toFIG. 6, a Finite State Machine diagram280for the solar energy management system200in accordance with one non-limiting embodiment is depicted. The operational modes of the solar energy management system200are depicted, with Mode 1 being a PWM operation (as also shown inFIG. 3A), Mode 2 being an MPPT operation (as also shown inFIG. 4A), and Mode 3 being standalone battery operation (as also shown inFIG. 5).

The self-introspect state282can be entered upon power up, as the control unit208is evaluating the hardware conditions. The result is a determination as to whether to transition to Mode 1, Mode 2, or Mode 3. Once operating in that mode, the state machine will vector to the next appropriate state.

While in Mode 1, the PV panel(s)202is energizing the solar energy management system200(Vpanel>Vpanel_min) and the voltage from the battery206is read as zero or not present (Vbatt<Vbatt_min), and the switch204remains open. The converter will run in DC/DC buck converter mode and produce a user programmed voltage at the output terminals210. While in Mode 2, the user connects the PV panel202or the battery206, and the power board212is energized to provide power to the control unit208. It is noted that the sequence of the use connecting the PV module202and the battery206is non-determinative, which is a beneficial operational aspect of the solar energy management system200. While in Mode 2, control unit208will perform MPPT tracking while maintaining the output voltage at the output terminals210at the level selected by the user, as long as Vpanel>Vmin and Vbatt>Vbatt_min. As shown inFIG. 4A, a difference in the firmware structure between Mode 1 and Mode 2 is the execution of the MPPT algorithm in Mode 2 will be running in software, and updating the current loop commands to the buck regulator. Mode 3 is generally similar as Mode 1, however the digital control algorithm for the buck regulator is turned OFF in the control unit208. Mode 3 will be maintained as long as Vpanel<Vmin and Vbatt>Vbatt_min. In accordance with the present disclosure, the digital control algorithm can be any suitable control paradigm, such as a PID controller, a Model Reference Adaptive Controller (MRAC), a neural network, or any other suitable type of control algorithm.

Solar energy management systems in accordance can be provide in a variety of form factors in implementations. The control logic of the solar energy management can be provided by any suitable technique, such as via an Field Programmable Gate Array (FPGA), an Application-Specific Integrated Circuit (ASIC), a microcontroller, or a microprocessor. By way of example,FIG. 7is a photograph of a circuit board of an example solar energy management system. As shown, the circuit board is removed from a housing and attached to a test fixture.

The foregoing description of embodiments and examples has been presented for purposes of description. It is not intended to be exhaustive or limiting to the forms described. Numerous modifications are possible in light of the above teachings. Some of those modifications have been discussed and others will be understood by those skilled in the art. The embodiments were chosen and described for illustration of various embodiments. The scope is, of course, not limited to the examples or embodiments set forth herein, but can be employed in any number of applications and equivalent articles by those of ordinary skill in the art. Rather it is hereby intended the scope be defined by the claims appended hereto.