Patent Description:
A thermal energy cooling system according to the preamble of claim <NUM> is known from document <CIT>.

Conventional vapor compression systems may be efficient at cooling environmental loads, such as rooms or systems with relatively slow gains in heat. However, these systems alone do not generally provide the rapid cooling features necessary to cool a system that outputs bursts of heat. A vapor compression system may take up to a minute, or in some cases more time, to reach full capacity and usually several minutes or longer to provide cooling to the target heat load. However, once these vapor compression systems are running, they can be efficient in cooling a target heat load to a specific temperature. In scenarios of limited power availability, the use of a vapor compression system to handle heat bursts may require more power than available or can be stored within the constraints of available space and weight on a platform.

Thermal energy storage systems have been used to level a cooling load by substituting cooling capacity and at times reduce costs or displace additional refrigeration equipment capacity needs in many environments. Many different types of materials have been used as phase change materials within thermal energy storage systems, including inorganic systems such as salt and salt hydrates, organic compounds such as paraffins or fatty acids. Polymeric materials, such as poly(ethylene glycol) have also been used as phase change materials. However, some phase change systems may require a relatively high amount of energy to start a freezing cycle. For example, some phase change materials may need to be cooled far below their phase change temperature to initiate crystal formation (nucleation), which is a necessary first step in freezing the phase change material.

A thermal energy cooling system according to the invention is defined in claim <NUM>.

Thermal energy cooling systems and methods are disclosed for rapidly cooling products, devices or other heat loads, including ancillary equipment hereafter referred to as hotel loads. Such systems may use a thermal energy storage system configured to rapidly cool bursts of heat, such as from a directed energy weapon system such as a laser weapon system. The thermal energy storage system can act as a sink to absorb heat being generated by the directed energy weapon system without requiring a large amount of energy consumption. In one embodiment, the thermal energy storage system comprises a salt hydrate, such as potassium fluoride tetra hydrate as the phase change material that is used to store cold energy.

In one embodiment the thermal energy storage system comprises a tank filled with a plurality of sealed thermal storage tubes with phase change material inside. A vapor compression system may be used to cool heat transfer fluid or refrigerant that circulates through the tank and around the sealed thermal tubes to freeze the phase change material. Each tube within the tank acts as a heat transfer surface between the phase change material and the heat transfer fluid within the tank. In one embodiment, running laterally through each storage tube filled with phase change material is an inner tube connected to a nucleation cooling system. The nucleation cooling system may pump refrigerant or heat transfer fluid through each inner tube to cool the phase change material within each thermal storage tube. The inner tube acts as a heat transfer surface to transfer heat from the phase change media to the refrigerant or heat transfer fluid to cool the phase change media and to at least initiate or facilitate the phase change from a liquid to a solid form.

As used herein, the term "tube" means any container that may contain phase change media. The tube may be in a variety of longitudinal configurations, including cylindrical, spherical cuboid, conical, triangular prism, hexagonal prism, planar, plates, a stack of plates, and any other related shape.

As mentioned above, many phase change materials need to be cooled below their phase change temperature in order to start a nucleation process that allows the material to freeze. However, once the phase change material has started nucleation, a higher temperature is used to continue the freezing cycle. Thus, nucleation of the phase change media within the storage tubes may be initiated by the nucleation cooling system by circulating refrigerant or heat transfer fluid at a first relatively low temperature. For example, nucleation cooling system may circulate refrigerant or heat transfer fluid through the thermal storage tubes to maintain a temperature of <NUM> to <NUM> within the thermal storage tubes to initiate nucleation of the phase change media. Once nucleation of the phase change material has started, the nucleation cooling system may raise the temperature of the refrigerant or heat transfer fluid so that the phase change media maintains a temperature of, for example, <NUM> to <NUM> which will continue freezing the phase change media depending on the type of phase change material within the tubes, and its particular phase change temperature. The use of higher temperatures for continuing the crystallization process saves energy by requiring less cooling power to be used for freezing the phase change media after nucleation has been initiated.

In another embodiment, the nucleation cooling system may be used to initiate the nucleation of the phase change media at a lower temperature. but then the vapor compression system connected to the thermal energy storage may be used to continue the freezing process by circulating cold heat transfer fluid or refrigerant within the thermal energy storage tank that holds the storage tubes. For example, the temperature of the heat transfer fluid from the vapor compression system may be chosen to be between <NUM> to <NUM> to continue freezing the phase change media once nucleation has been initiated by the nucleation cooling system.

In one embodiment, the thermal energy cooling system pumps a heat transfer fluid from a heat exchanger in thermal contact with a directed energy weapons system through the thermal energy storage system to rapidly offload the absorbed heat. The heat transfer fluid may be ethylene glycol water or a phase change refrigerant. In this embodiment, the system may be configured to maintain the fiber amplifiers and other critical system components of the laser weapon system between about <NUM> - <NUM>, <NUM> - <NUM> or <NUM> - <NUM> or similar temperature ranges.

Thermal energy storage systems that are applicable for use with the above-mentioned high-energy laser cooling system may be configured to undergo a solid-liquid phase change with a phase transition temperature between about <NUM> and about <NUM>. This range may be between about <NUM> and <NUM> assuming that a heat transfer fluid (coolant) flow to the laser has a temperature in the range of about <NUM> to <NUM>.

In one embodiment the thermal energy storage system uses a potassium fluoride-based phase change material. The properties of potassium fluoride, and particularly potassium fluoride tetra hydrate allow the thermal energy storage system to rapidly absorb relatively large bursts of heat coming from a system such as a directed energy weapons system. In particular, this salt hydrate was found to have a very good crystal growth propagation following nucleation that spreads throughout the phase change material and aids thermal distribution into the phase change material. This material also has a high thermal conductivity, which helps minimize thermal gradients.

The operating conditions for a laser weapon cooling system in which the phase change materials are used as a thermal energy storage system call for much more rapid melt and freeze periods than traditionally required for seasonal or diurnal thermal energy storage. System discharge (melting) of the phase change material in the thermal energy storage system often has to occur in less than five minutes and more frequently even in less than three, or even two minutes. The time to charge (re-freeze) the phase change material is often also much shorter, typically in less than <NUM> minutes, and often less than <NUM>, <NUM>, <NUM>, <NUM> or <NUM> minutes. Thus, in cases where the phase change material has been completely melted so that no crystals remain, the nucleation cooling system may be initiated to rapidly begin nucleation and freezing of the phase change media. In some embodiments, once the phase change material in the thermal energy storage system is frozen, so that the storage system charged, the phase change material needs to be maintained in its frozen state. To maintain the phase change material in a frozen state, either the nucleation cooling system or a vapor compression system connected to the thermal energy storage may be activated at particular time intervals such that any phase change material which transitioned into a liquid state is cooled and transitioned back into a frozen state and/or maintained in the frozen state.

During use, the laser weapon may be activated for a total firing period of <NUM>, <NUM> or <NUM> or even <NUM> minutes and in some special applications even longer. Since the firing period usually occurs in pulses of several seconds for each target, as short as <NUM> or <NUM> seconds and as long as about <NUM> to <NUM> seconds, the total discharge period of <NUM>, <NUM> or <NUM> or even <NUM> minutes can occur over periods of <NUM> to <NUM> minutes. Depending on the target occurrence, or lack thereof, the system may also be recharged before it is completely depleted. The thermal management system, including the thermal energy storage system, however, usually has a design requirement to be able to operate under a worst case scenario of continuous lasing of <NUM>, <NUM> or <NUM> or even <NUM> minutes and in some special applications even longer, which likely will never occur. Accordingly, the thermal energy cooling system preferably has the capacity to discharge the thermal energy storage system and cool the laser over this entire continuous time period. Of course, the total activation period, including pauses between firing, may be longer, depending on the particular need. In addition, the system preferably can recharge (re-freeze) the phase change media in the thermal energy storage system fairly rapidly once the activation time has ended, for example in less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> minutes so that the thermal energy cooling system can be ready to effectively cool the laser weapon for additional activation periods.

In one embodiment, the thermal energy storage system comprises an enclosure or tank comprising a system of storage tubes holding phase change media that are running throughout the tank. In some embodiments, the storage tubes having annular cross-sections that contain the phase change material and an inner tube containing refrigerant or first heat transfer fluid from the nucleation cooling system circulating through the inner tube while a second heat transfer fluid or refrigerant from the directed energy weapon or a vapor compression cooling system circulates around the outside of the storage tube.

In one embodiment, the thermal energy storage system may be made out of one or more modules, each module having a plurality of storage tubes with phase change material inside the storage tubes and heat transfer fluid flowing on the outside of the storage tubes and within the thermal energy storage tank. Such a plurality of storage tubes may be in multiple planar levels or in one or more bundles. An example storage tube diameter may be <NUM> inch, but embodiments may include storage tubes with an outer diameter between about ¼ inch and <NUM> inches or above, preferably between about ¼ inch or about <NUM> inch mostly depending on system response time requirements, but to some degree also depending on heat transfer enhancements or the effectiveness of any crystallization additives used within the phase change material to reduce subcooling. Examples of such crystallization additives include pumice, a textured volcanic glass, which reduces the subcooling during the freezing process.

As mentioned above, running longitudinally within each storage tube is an inner tube from the nucleation cooling system. The inner tube may be chosen to optimize the flow of refrigerant or heat transfer fluid through the inner tube while also providing enough space within the storage tube for a sufficient volume of phase change material to meet the energy storage capacity requirements of the thermal energy storage. For example, if the storage tube filled with phase change material has an outer diameter of <NUM>", the inner tube from the nucleation cooling system running within the storage tube may be ¼" to ½" in diameter. However, if the storage tube is only ½" in diameter, the inner tube may be <NUM>/<NUM>" to <NUM>/<NUM>" in diameter. It should be realized that these dimensions are exemplary only and are not limiting on the scope of the invention.

As will be described more fully below with reference to <FIG>, the nucleation cooling system may comprise a vapor compression loop that circulates refrigerant from a refrigerant receiver or tank through a pump to the inner tubes of the thermal energy storage. After traversing the thermal energy storage system, the refrigerant may be circulated back to the refrigerant receiver. The refrigerant receiver acts as a storage of liquid and vapor refrigerant and is connected to a compressor to compress the vapor to be condensed and routed back into the low temperature receiver. Such system is often referred to as a liquid overfeed system in the refrigeration terms. As illustrated below, the conventional vapor compression loop within the nucleation cooling system comprises a single compressor, however embodiments of the invention may include a nucleation cooling system with multiple compressors. In other embodiments there may be more than vapor compression loop within the nucleation cooling system, with each loop circulating refrigerant to specific inner tubes within the thermal energy storage tank. For example, the thermal energy storage tank may comprise four modules of storage tubes. The nucleation cooling system may comprise two, three, four, five, six or more separate vapor compression loops, with each loop serving to circulate refrigerant to a particular module of storage tubes.

In another embodiment, the nucleation cooling system may not circulate refrigerant to the thermal energy storage system. Instead the nucleation cooling system may cool a heat transfer fluid through a heat exchanger that is pumped through the inner tubes of the thermal energy storage system.

In this first operating mode, the nucleation cooling system is used to initiate crystal formation at a first low temperature and then continue with freezing the phase change media at a relatively higher temperature. Typical subcooling for potassium fluoride tetra hydrate phase change medium is <NUM> to <NUM> below its transition temperature of <NUM>. This subcooling may be achieved by circulating a refrigerant or first heat transfer fluid within the inner tubes running through the storage tubes containing the potassium fluoride tetra hydrate. Once solidification and freezing of the phase change material has started the nucleation cooling system may circulate higher temperature refrigerant or heat transfer fluid at a temperature that is closer to the transition temperature of the potassium fluoride tetra hydrate to complete the freezing process, provided an adequate differential temperature for rapid freezing is maintained.

This may call for an operating strategy in which a relatively cold refrigerant is circulated to the inner tubes of the thermal energy storage system, of about <NUM>-<NUM>, preferably <NUM>- <NUM>, to initiate the nucleation of the phase change material. The remainder of the cooling energy may be provided by circulating refrigerant from the nucleation cooling system that is much closer to the phase change temperature of the potassium fluoride tetra hydrate material, of for example <NUM>- <NUM>. By continuing to freeze the phase change material with refrigerant or heat transfer fluid at a relatively higher temperature of <NUM>- <NUM> for the later stages of the freezing cycle, the overall system conserves energy and is more efficient.

One uniquely desirable feature of conducting the entire freezing process with the nucleation cooling system is that the other cooling system does not have to be altered in its operating temperature at any time to freeze the phase change material but can continue serving hotel loads at the most ideal temperature for such loads and can do so while the nucleation system is charging the thermal energy storage system preparing it for the next laser operation induces burst load to manage or assist with burst cooling.

In this second operating mode, the nucleation cooling system is used to initiate crystal formation at a first low temperature and then a second vapor compression system that is in thermal contact with the thermal energy storage completes or at least significantly assists in the freezing cycle. For example, the nucleation cooling system circulates refrigerant within the inner cooling tubes to bring the temperature of the phase change media to below the crystallization formation point. For example, for potassium fluoride tetra hydrate, the refrigerant may be cooled to at about <NUM>- <NUM>. Once crystallization of the phase change material has started the nucleation cooling system may be turned off, operated at the same low or higher temperature, but the second vapor compression system in thermal communication with the storage tubes within the thermal energy storage may be used to continue freezing the phase change material to its final frozen state. The vapor compression system may be used to cool heat transfer fluid that is circulated through the thermal energy storage at a temperature that causes the phase change media to continue changing phase from liquid to solid form. For example, with potassium fluoride tetra hydrate, this may be at a temperature of about <NUM>- <NUM>.

In this third operating mode, the nucleation cooling system may not be used at all. In some scenarios it may be more efficient to only use the vapor compression system to initiate and freeze the phase change media. In this embodiment, the vapor compression system that is in thermal contact with the thermal energy storage system may first cool a heat transfer fluid to a relatively low temperature such that phase change material within the storage tubes may start to form crystals. Once crystallization of the phase change material has started the vapor compression system may be adjusted to circulate relatively warmer heat transfer fluid, of about <NUM> to <NUM> to continue the freezing cycle. Thus, the vapor compression system may be used to initiate and maintain the phase change media in a frozen state in this operating mode.

In this maintenance mode, the nucleation cooling system is only used to maintain the phase change media in a frozen state. During normal use, the phase change material will warm to the ambient temperature unless additional cooling power is added to maintain the thermal energy storage phase change material in a frozen state. In this maintenance mode, the nucleation cooling system circulates refrigerant or heat transfer fluid through the storage tubes of phase change material at a temperature designed to keep the phase change material in a frozen state over time. A control system may monitor temperature sensors to determine the ambient temperature and the temperature of the thermal energy storage system and determine the proper temperature of refrigerant or heat transfer fluid to circulate through the thermal energy storage system to maintain the phase change material in a frozen state.

As mentioned, an advantage of this operating mode is the fact that the second vapor compression system can be dedicated to serve the hotel loads at the optimum temperature for such cooling without any adjustment needs for maintaining the thermal storage system in the frozen state.

In this maintenance mode, the second vapor compression system is used to maintain the phase change media in a frozen state. During normal use, the phase change material will warm to the ambient temperature unless additional cooling power is added to maintain the thermal energy storage phase change material in a frozen state. In this maintenance mode, the vapor compression system circulates cold heat transfer fluid through the thermal energy storage system and around the storage tubes of phase change material in order to keep the phase change material in a frozen state over time.

In some embodiments, cooling system capacity controls may make it also advantageous to have the nucleation system assist in the maintenance via the second vapor compression loop.

In one embodiment, the system is operated to retain a reserve of frozen phase change material to prevent the phase change material from completely melting. Because the required heat transfer fluid temperature required to initiate crystallization of the phase change material is relatively low, the system may be more energy efficient by keeping a reserve of crystallized frozen phase change material within the thermal energy storage unit. For example, each sub-containment portion of the thermal energy storage system (e.g. tube or channel) may retain a minimum percentage of frozen, crystalized phase change material. For example, the retained minimum percentage may be <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or more of the total frozen phase change material. The retained portion may be <NUM>%-<NUM>%, <NUM>%-<NUM>%, or <NUM>%-<NUM>%, <NUM>%-<NUM>% <NUM>%-<NUM>%, or <NUM>%-<NUM>% of total volume of phase change material in the thermal energy storage system. Higher percentages of total frozen phase change material will of course also avoid the need for initial nucleation and crystallization.

If the system retains a minimum amount of frozen phase change material, the temperature of the heat transfer fluid required to freeze the thermal energy storage system can be, for example, between <NUM> and <NUM>. If the phase change material is allowed to fully melt, the temperature of the refrigerant or heat transfer fluid from the nucleation cooling system or vapor compression system may need to be <NUM> or colder to initiate crystallization of the phase change material. Accordingly, in one embodiment it is more energy efficient to maintain the retained minimum portion of crystalized, frozen phase change material during cooling operations and prevent the phase change material from completely melting.

In one embodiment, a control system monitors sensors that report the temperature of the phase change material or the heat transfer fluid temperatures entering and exiting the thermal energy storage system along with the flow rate of the refrigerant or heat transfer fluid. From these data, the control system may calculate or estimate the amount of frozen phase change material remaining in the thermal energy storage system. The thermal energy storage system may be made of hundreds of separate tubes or channels. In case of storage tubes, each tube may have more or less frozen phase change material located within it. Measuring the actual amount of frozen phase change material in each individual tube may not be practical, so estimating the amount of frozen phase change material by measuring the overall temperature of the phase change material and refrigerant or heat transfer fluid flows may be more practical.

If the control system determines that the amount of remaining frozen phase change material is below a predetermined threshold, the control system may initiate the nucleation cooling and/or vapor compression system to start circulating refrigerant or heat transfer fluid in order to freeze the phase change material. In addition, the control system may prevent the system from being able to initiate additional cooling operations using the thermal energy storage system until the vapor compression system has had time to freeze more of the phase change material in the thermal energy storage system. In one embodiment, the system may only allow the system to perform additional cooling cycles if, after such a cooling cycle, the remaining frozen phase change material would remain above the minimum set threshold. In other cases, an imminent threat or other condition requiring the laser to fire may override such threshold preservation mode.

To ensure that every storage tube, or almost every storage tube, within the thermal energy storage system is very likely to contain at least some frozen phase change material, the system may choose a minimum set threshold value that is higher than what is needed in any particular tube. For example, the system may set the threshold at <NUM>% or <NUM>%, such that when the control system determines that only <NUM>% or <NUM>% of the total volume of phase change material remains frozen it will activate the nucleation cooling system or vapor control system to start freezing the phase change material. By choosing a minimum value of for example <NUM>% or <NUM>%, this may ensure that each storage tube within the thermal energy storage system has at least some frozen phase change material to start an efficient cooling cycle. Of course, depending on the system design, it may require the minimum threshold to be set at <NUM>%, <NUM>%, <NUM>% or even <NUM>% to ensure that each storage tube within the system contains some amount of frozen phase change material. Selecting a higher percentage is of course always an option, however, the higher the percentage of left-over frozen material, the lower the thermal energy storage system capacity will be.

In one embodiment. the thermal energy storage system acts as a burst mode cooling system to remove the heat generated from each firing event of a directed energy weapons system, such as a laser weapons system. During each firing cycle, the system transfers thermal energy from the weapon to the cooling and thermal energy storage system. In one embodiment this can be accomplished by running the heat transfer fluid outside the storage tubes containing the phase change material. It is also possible, that refrigerant or thermal heat transfer fluid coming from directed energy weapons system and hotel loads may be routed through a vapor compression system to perform initial cooling on the heated thermal transfer fluid, followed by circulation through the thermal energy storage system or routed through the thermal energy storage system first and then followed by the vapor compression system to reach its final temperature.

In another embodiment, the vapor compression system or nucleation cooling system is used to supplement the cooling capacity of the thermal energy storage system as the directed energy weapons system is being fired. Accordingly, during a firing event, the nucleation cooling system, the vapor compression system, and thermal energy storage system may all act in concert to provide cooling capacity to remove heat from the directed energy weapons system and hotel loads. In one embodiment, the control system for the nucleation cooling system and/or vapor compression system is a vector drive controller that is used to increase efficiency of the overall system.

Directed energy weapons systems may also include additional ancillary mechanical or electrical equipment or components that need to be cooled in order to operate the weapons system efficiently. Such additional equipment, also termed a "hotel load" may include sensors, radar systems, batteries, power modules, generators, pumps, motors, computers, electronics and other equipment that is ancillary to the main weapons system. In particularly warm environments, such as the desert, these additional components may work more efficiently by being cooled prior to use. Thus, in one embodiment, the thermal energy cooling system includes a vapor compression system that acts as an ancillary cooling system configured to cool these additional components (as well as the laser diode amplifiers) to a predetermined temperature, or within a temperature range, so that they operate efficiently in warmer environments.

In some embodiments, the directed energy weapons system and hotel loads are located on a single platform. The platform may include a variety of different sensors to monitor and to receive signals from or send signals to components of the directed energy weapons system and the hotel loads. These sensors are used to generate sensor data that is read by the weapon system including the thermal energy cooling system controller in order to determine the proper time to activate the weapon system including the burst mode cooling cycle and discharge the thermal energy storage system. In some embodiments, the controller also receives sensor data from sensors and systems that are not located on the platform, and the controller may use this external sensor data to help determine the correct time to activate the weapon system and the burst mode cooling event.

The one or more vapor compression systems may be composed of multiple compressors, some dedicated to freeze and maintain frozen phase change material, such as potassium fluoride tetra hydrate, in the thermal energy storage system, and some configured to cool the hotel load or the hotel load and the laser cooling load in case of firing. However, given a control signal that there is a need to charge the thermal energy storage system, all compressors may be activated to charge the thermal energy storage system if the hotel load is determined to be able to afford a temporary lack of cooling and the laser is not firing or expected to be firing shortly. This determination may be based on whether the individual components of the hotel load are detected to be at or below their individual component design temperature. The compressors, some or all, may also be used to cool the high-energy laser in parallel to use of the thermal energy storage system being discharged. In some embodiments, the vapor compression system has a capacity of about 1kW to 50kW, 51kW to 100kW, or up to several hundred kilowatts of cooling power or more.

In some embodiments, the one or more vapor compression systems comprises a vapor compression system with one or more variable speed compressors controlled to vary the output capacity of the vapor compression system. The vapor compression system may be controlled by a Vector Control System (VCS) that is configured to optimize the efficiency of the vapor compression system by varying the torque placed on the compressor.

In some embodiments, the one or more vapor compression systems comprise one or more high voltage variable speed DC compressors to vary output capacity and be able to operate off a high voltage battery.

It should be realized that thermal energy storage systems are not only made from potassium fluoride tetra hydrate, but also from other salt hydrates such as calcium chloride hydrates, calcium chloride/calcium bromide mixture hydrates, sodium based hydrates, lithium based hydrates, such as lithium chlorate tri-hydrate. etc. If such media are used, the operating temperatures may be adjusted to the media specific phase change temperatures and the specific subcooling requirements. In some embodiments, the salt hydrate is the <NUM> hydrate of potassium fluoride.

In some embodiments, the thermal energy storage system has its own pump connected to route thermal heat transfer fluid through the thermal energy storage system cooling loop. If the thermal heat transfer fluid is a liquid such as ethylene or propylene glycol water, the pump may be a pump that is controlled by a variable speed motor. If the thermal heat transfer fluid is phase change refrigerant, the pump motor may be connected to a vector control system (VCS) programmed to optimize efficiency of the thermal energy storage system pump between the best amount of heat transfer and the resulting pressure drop of the refrigerant.

A control system monitors the temperatures of the various systems, including the directed energy weapons system, the ancillary components, the thermal energy system and the vapor compression systems. The control system uses stored logic and programming to determine the appropriate use of each component. If the system is idle, and the temperature of the thermal energy storage system is high or indicates a partial melt, the control system may activate a vapor compression system to begin re-freezing the thermal energy storage system. However, if the control system also determines that the ancillary components are too hot, the control system may prioritize having the one vapor compression system cool the ancillary components so they don't become damaged before having the vapor compression system re-freeze the phase change material in the thermal energy storage system. The flexibility of the system allows for the control system to work towards being as efficient as possible to cool the components of the system and maintain the system in a state of readiness for the next activation of the directed energy weapons system.

The control system may be configured in many ways to activate a burst mode cooling cycle of the system. In one embodiment, the controller is any electronic device or apparatus that activates, modulates, or deactivates the flow of refrigerant or heat transfer fluids in the system. The control system may include any electronic device or apparatus that controls a pump, fan, or valve which moves heat transfer fluid throughout the system.

In one embodiment, the nucleation cooling system uses a refrigerant to directly cool the phase change material within the thermal energy storage system. By using refrigerant the nucleation and/or freezing process may be faster than freezing with heat transfer fluid. In addition, the use of refrigerant may require less energy to cool the phase change material in comparison to a cooling system that cools a heat transfer fluid which is then pumped through the phase change material.

In one embodiment, the control system is linked to one or more temperature sensors and activates a burst mode cooling cycle when a temperature sensor near the directed energy weapons system reaches a predetermined target temperature. The temperature sensor may be thermally linked to the directed energy weapons system so when that thermal load reaches the predetermined target temperature, a burst mode cooling cycle is begun. Alternatively, the control system may be electronically linked to an activation signal that triggers a burst mode cooling cycle. The activation signal may be controlled by a predictive process that senses a variety of data, including intelligent signaling of approaching target(s) and then predict when to activate a cooling cycle. For example, the control system may sense the present temperature of the thermal load, the time since the last activation, and the state of other equipment of devices linked to the directed energy weapons system. Using this data, the system may activate a burst mode cooling cycle just before the directed energy weapons system starts to heat. In some embodiments, the control system may activate a cooling cycle <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more seconds in advance of a determined or predetermined cooling event.

<FIG> shows one exemplary thermal energy cooling system <NUM> that has a vapor compression system <NUM> and a nucleation cooling system <NUM>. The thermal energy cooling system <NUM> is designed to provide burst mode cooling to rapidly cool a directed energy weapons system <NUM>, which may be during the firing event of operation, by moving heat transfer fluid from a heat exchanger <NUM> adjacent and connected to the directed energy weapons system <NUM> to a thermal energy storage system <NUM>.

The vapor compression system <NUM> connects to output control valves <NUM> which control output of thermal heat transfer fluid from the vapor compression system <NUM> and/or thermal energy storage system <NUM> to the heat exchanger <NUM> that is in thermal communication with a directed energy weapons system <NUM>. The heat exchanger <NUM> then connects to a pump <NUM> which communicates with a set of input control valves <NUM> to form a cooling loop from the vapor compression system <NUM> and/or thermal energy storage system <NUM> to the directed energy weapons system <NUM> and back again.

As shown in <FIG>, the pump <NUM> and input control valves <NUM> connect to the thermal energy storage system <NUM>. The thermal energy storage system <NUM> may include frozen or partially frozen phase change material, such as potassium fluoride tetra hydrate, that is used to cool the directed energy weapons system <NUM> while active. The thermal energy storage system <NUM> is connected to the output control valves <NUM> which connect the thermal energy storage system to the directed energy weapons system heat exchanger <NUM>. The directed energy weapons system heat exchanger <NUM> connects to the pump <NUM> which can return heated thermal heat transfer fluid from the directed energy weapons system heat exchanger <NUM> to the input control valves <NUM> and back to the thermal energy storage system <NUM> in a thermal energy storage system cooling loop.

In some embodiments, the directed energy weapon system may be cooled using both the vapor compression system <NUM> and the thermal energy storage system <NUM>. For example, the heat transfer fluid cooled by the vapor compression system <NUM> and the heat transfer fluid cooled by the thermal energy storage system <NUM> may be circulated to the directed energy weapon system heat exchanger <NUM>. The heat transfer fluids may mix after being cooled by their respective cooling systems and then the heat transfer fluid circulated to the heat exchanger <NUM> using the output control valves <NUM>. In some embodiments, there may be separate lines where the heat transfer fluids do not mix. For example, the heat transfer fluid from the vapor compression system <NUM> may circulate directly to the heat exchanger <NUM>. Similarly, heat transfer fluid from the thermal energy storage system <NUM> may circulate directly to the heat exchanger <NUM> as well. In some embodiments the flow may be serial through the thermal storage system followed by the vapor compression system or vice versa. In some embodiments the flow can be partially in series and partially in parallel.

In one embodiment, the vapor compression system <NUM> is designed to form a heat transfer fluid cooling loop to the hotel load heat exchanger <NUM> in order to cool the components of the system <NUM> that make up the hotel load. As shown, the output control valves <NUM> may route heat transfer fluid from the vapor compression system <NUM> to the hotel load heat exchanger <NUM> that is adjacent to the hotel load <NUM>. The pump <NUM> then may recirculate the thermal heat transfer fluid coming from the hotel load heat exchanger <NUM> back though the input control valves <NUM> to the vapor compression system <NUM>, forming a hotel load cooling loop.

As shown in <FIG>, the vapor compression system <NUM> is also connected to the thermal energy storage system <NUM> through pipes <NUM> running heat transfer fluid into the thermal energy storage system <NUM>. The vapor compression system <NUM> may use a heat exchanger to cool heat transfer fluid and charge the thermal energy storage system <NUM>. It should be realized that the thermal energy storage system <NUM> may comprise a series of storage tubes filled with phase change media which act as heat exchangers to transfer heat from the heat transfer fluid to the frozen phase change material within the thermal energy storage system <NUM>. The vapor compression system <NUM> may be used to continue crystallization and freezing of phase change material within the thermal energy storage system <NUM> after initial nucleation of such material from the nucleation cooling system <NUM>. A pump <NUM> may circulate the cooled heat transfer fluid from the thermal energy storage system <NUM> to the vapor compression system <NUM>. The pump <NUM> and pipes <NUM> form a vapor compression cooling loop used to cool the thermal energy storage system <NUM>.

It should be realized that in one embodiment the vapor compression cooling loop and the hotel load cooling loop may use the same heat transfer fluid and thereby share some of the same piping, valves and pumps to communicate within the system <NUM>. Alternatively, the system <NUM> may include parallel cooling loops from the vapor compression system and the thermal energy storage system where they do not share the same heat transfer fluid, piping, valves and pumps, and therefore thermally communicate through the same or different heat exchangers with the directed energy weapons system.

The thermal energy storage system <NUM> is connected to the nucleation cooling system <NUM> via pipes <NUM> and the pump <NUM>. A second heat transfer fluid that is separate from the heat transfer fluid of the vapor compression system <NUM> may circulate from the nucleation cooling system <NUM>, through pump <NUM>, to the thermal energy storage system <NUM>, and back through the pipes <NUM> to form a nucleation cooling loop. The second heat transfer fluid may be a different type of fluid from the heat transfer fluid of the vapor compression system <NUM>, or the two fluids may be of the same type. The nucleation cooling system <NUM> may be used to facilitate crystallization of the phase change material in the thermal energy storage system <NUM> by providing relatively lower temperature refrigerant or heat transfer fluid through storage tubes <NUM> (see <FIG> and <FIG>) containing the phase change material to cause nucleation, i.e. initial forming of solid material of the phase change material. After this initial crystallization of the phase change material, then a relatively higher temperature of refrigerant is used to continue the crystallization. The ability to use higher temperature fluid saves energy. The higher temperature heat transfer fluid may be supplied by the vapor compression system <NUM>, in one embodiment. Alternatively, or in addition, in some embodiments, the higher temperature heat transfer fluid may be supplied by the nucleation cooling system <NUM> operating at a higher temperature. The preferred heat transfer fluid of the nucleation cooling system <NUM> is refrigerant supplied to the storage tubes <NUM> via a liquid overfeed system.

As mentioned above, the thermal energy storage system <NUM> and vapor compression system <NUM> are connected to the set of input control valves <NUM> and output control valves <NUM>. These valves control the flow of thermal heat transfer fluid through the system <NUM> and into and out of each component. As shown, a control system <NUM> is in electrical communication with the vapor compression system <NUM>, the nucleation cooling system <NUM>, input control valves <NUM> and output control valves <NUM>. By opening and closing the electrically controllable valves within the input control valves <NUM> and output control valves <NUM> the control system <NUM> may control which component of the system is circulating heat transfer fluid or refrigerant at any particular time during operation of the system <NUM>.

The output control valves <NUM> connect to the directed energy system heat exchanger <NUM> that is in thermal communication with the directed energy weapons system <NUM>. The directed energy weapons system <NUM> is shown as being thermally connected to the heat exchanger <NUM>. In the case that two phase refrigerant is being circulated within the system <NUM>, it should be realized that the heat exchanger <NUM> may be an evaporator configured to change or partially change the phase of the refrigerant. In the case that a heat transfer fluid or media such as glycol-water is being circulated, the heat exchangers may be heat transfer tubes, coils or plates configured to absorb heat into the thermal heat transfer fluid.

In one embodiment, the directed energy weapons system <NUM> may be a high-energy laser, and the directed energy system heat exchanger <NUM> may be in thermal communication with the laser diodes and diode amplifiers of that system which generate the bulk of heat bursts while the system is activated. A high-energy laser may include lasers that are <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> kilowatt or higher energy lasers.

The output control valves <NUM> also connect to the one or more hotel loads heat exchangers <NUM> that are in thermal communication with the hotel load <NUM> adjacent to the directed energy weapons system <NUM>. As discussed above, the hotel load <NUM> may include the batteries, motors, radar, communications and other equipment that is ancillary to the directed energy weapons system. As mentioned above, in the circumstance where thermal transfer media such as glycol-water is used instead of refrigerant, the hotel load heat exchangers may be replaced with a thermal transfer system configured to transfer heat to the thermal transfer media.

It should be realized that the system <NUM> may include more than the one pump <NUM> and that additional pumps, fans, valves and motors may be included within the system to operate as described herein. For example, additional pumps may be included adjacent to the output control valves <NUM> to move thermal heat transfer fluid to the heat exchangers <NUM>, <NUM>. Fans may be disposed adjacent to the directed energy system heat exchanger <NUM> or hotel load heat exchanger <NUM> to move heated or cooled air across the heat exchangers.

The system <NUM> is flexible in that during use the system <NUM> may route heated fluid from the directed energy weapons system heat exchanger <NUM> into either or both of the vapor compression system <NUM> and thermal energy storage system <NUM>. Depending on the temperature of the heat transfer fluid, and the predicted cooling needs of the system, the heat transfer fluid may be routed to only the thermal energy storage system <NUM> or only the vapor compression system <NUM> for cooling. However, in some embodiments, the heat transfer fluid may be routed in parallel or sequentially through the thermal energy storage system <NUM> and the vapor compression system <NUM>.

The control system <NUM> is also electrically connected with the nucleation cooling system <NUM>. The control system <NUM> may receive data from sensors and in response control operation of the nucleation cooling system <NUM> to initiate crystallization of phase change material within the thermal energy storage system <NUM>. Sensors may be located within the thermal energy storage system <NUM>, with the directed energy weapons system <NUM>, within the hotel load <NUM>, and/or within the vapor compression system <NUM>, or any components or pipes connected thereto. For example, temperature sensors within the thermal energy storage system <NUM> may provide temperature data to the control system <NUM> which may analyze the data and determine whether to operate the nucleation cooling system <NUM>. The nucleation cooing system <NUM> may be used if it is determined that initial crystallization has not begun or has not begun sufficiently, or that energy from the phase change material has been completely discharged or discharged beyond a threshold amount, within the thermal energy storage system <NUM>. It may also be used to operate the nucleation cooling system <NUM> prior to reaching complete melting at a higher temperature to re-freeze or maintain the phase change material as frozen in the thermal energy storage system <NUM>.

<FIG> are schematic illustrations respectively of the vapor compression system <NUM> and the nucleation cooling system <NUM>.

As shown in <FIG>, the vapor compression system <NUM> includes a compressor <NUM>, a condenser <NUM>, and a heat exchanger <NUM> which may be an evaporator. Refrigerant is circulated through the compressor <NUM>, condenser <NUM>, and heat exchanger <NUM> to remove heat from one or more heat transfer fluids circulating through the heat exchanger <NUM>. As shown, heat transfer fluid may be received from the thermal energy storage system <NUM> via the pump <NUM> to be cooled by the heat exchanger <NUM>, and then exit the heat exchanger <NUM> for circulation back to the thermal energy storage <NUM>. The cooled heat transfer fluid may be used by the thermal energy storage system <NUM> to continue crystallization of phase change material within the storage system <NUM>, as described herein.

As further shown, heat transfer fluid may circulate from the directed energy system heat exchanger <NUM> and/or from the hotel load heat exchanger <NUM> via the input control valve <NUM>. The valve <NUM> may be operated to cause or prevent flow of heat transfer fluid from the valves <NUM> to the heat exchanger <NUM> of the vapor compression system <NUM> for cooling. The heat transfer fluid from the valve <NUM> may get cooled by and exit the vapor compression system <NUM> and circulate to the output control valve <NUM> for circulation back to the directed energy system heat exchanger <NUM> and/or to the hotel load heat exchanger <NUM> to remove heat respectively from the directed energy weapon system <NUM> and/or the hotel load <NUM>.

As shown in <FIG>, the nucleation cooling system <NUM> includes a compressor <NUM>, a condenser <NUM>, and a refrigerant reservoir <NUM>. Refrigerant is circulated through the compressor <NUM>, condenser <NUM>, and refrigerant reservoir <NUM> to remove thermal energy from refrigerant circulating through the refrigerant reservoir <NUM> by re-condensing the refrigerant portion evaporated by the load. Refrigerant may circulate from the thermal energy storage system <NUM> in which it partially evaporates as it charges the thermal energy storage system to the refrigerant reservoir <NUM> where it returns as a two-phase mixture of liquid and gas. Refrigerant from the condenser <NUM> is returned into the reservoir <NUM> in the liquid phase. The liquid collects at the bottom of the reservoir <NUM> while the vapor fills the space above the liquid. The liquid refrigerant is then circulated from the reservoir <NUM> to the thermal energy storage system <NUM> via the pump <NUM>. The refrigerant is used to cause nucleation, and possibly the entire freezing, of the phase change material within the thermal energy storage system <NUM>, as described herein. The refrigerant then flows from the thermal energy storage <NUM> back to the nucleation cooling refrigeration system via the pipe <NUM>. If the nucleation cooling system is used to complete the entire freezing cycle, the cooling temperature may be increased after initial nucleation in the storage tubes of thermal energy storage system <NUM> is achieved.

Inside the reservoir <NUM>, the vapor from the liquid refrigerant is circulated through the vapor compression system <NUM> to the compressor <NUM> and then condenser <NUM> and then cools and changes to a liquid which is then returned back into the reservoir <NUM>.

<FIG> is a schematic illustration of a cross section of the thermal energy storage system <NUM>, according to one embodiment. The thermal energy storage system <NUM> includes two separate heat transfer fluid paths for initially causing crystallization of phase change material <NUM> and then continuing the crystallization process. The phase change material is frozen or partially frozen to provide cooling to heat transfer fluid circulated through the thermal energy storage system <NUM> that is received from the directed energy system heat exchanger <NUM> and/or from the hotel load heat exchanger <NUM> via the input control valves <NUM> and then exits to flow back to the directed energy system heat exchanger <NUM> and/or from the hotel load heat exchanger <NUM> via the output control valves <NUM>.

The phase change material <NUM> may be a hydrated salt complex, such as potassium fluoride tetrahydrate. The phase change material <NUM> is contained in a series of storage tubes <NUM>, shown here as elongated, cylindrical tubes having an annular cross-section (see <FIG>). The storage tubes <NUM> each have an elongated opening through which an inner tube <NUM> extends to circulate refrigerant from the nucleation cooling system <NUM> therethrough. By circulating the refrigerant through the center of the phase change material <NUM>, the phase change material will more efficiently begin to freeze. The design using a separate refrigeration system <NUM> for nucleation allows for the use of a lower temperature to rapidly initiate nucleation without the need to cool down the entire system heat transfer loop connected to pump <NUM> to a temperature that may not be ideal for the hotel loads <NUM> or the pre-cooling of the laser diodes and diode amplifiers within the directed energy weapons system <NUM>. The refrigerant enters the inner tube <NUM> from the nucleation cooling system <NUM> via an intake distributor or manifold <NUM>. The distributor or manifold <NUM> distributes the refrigerant through a set of inner tubes <NUM> to initiate crystallization of the respective phase change materials contained within respective storage tubes <NUM>. The inner tubes <NUM> connect to an exit manifold or pipe <NUM>. The refrigerant, now partially evaporated due to transferring heat from the phase change material <NUM>, then circulates from the exit pipe <NUM> back to the nucleation cooling system <NUM> for re-condensation.

It should be realized that the thermal energy storage system <NUM> may include a series of input and output distributors, manifolds, or pipes, wherein each one connects to a row of inner tubes <NUM> as shown in <FIG>. For example, the thermal energy storage system <NUM> may include <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more rows of <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more inner tubes, with each row being connected to its own input distributor, manifold or tube and output distributor, manifold or tube. The input distributors and output manifolds each come together, respectively, outside of the thermal energy storage system <NUM> to route refrigerant from and to the nucleation cooling system.

The thermal energy storage system <NUM> receives heat transfer fluids from the directed energy system heat exchanger <NUM> and/or from the hotel load heat exchanger <NUM> via the input control valves <NUM> and may receive heat transfer fluid from the vapor compression system <NUM>. The heat transfer fluids are received into an entrance manifold <NUM> and flow over and around the storage tubes <NUM> and to an exit manifold <NUM> where it flows back to the vapor compression system <NUM> and back to the directed energy system heat exchanger <NUM> and/or from the hotel load heat exchanger <NUM> via the output control valves <NUM>.

The thermal energy storage system <NUM> may selectively receive one or the other sources of heat transfer fluid or receive both simultaneously. In some uses of the system <NUM>, the heat transfer fluid may be received from the vapor compression system <NUM> to continue the crystallization of the phase change material <NUM>, and the circulation of heat transfer fluid from the input control valve <NUM> may be stopped or reduced. This operation may be used in between firings of the weapons system in order to freeze the phase change material and prepare for another firing of the weapon.

In some uses of the system <NUM>, the heat transfer fluid may be received from the input control valve <NUM> to cool heat transfer fluid from the weapon or hotel load heat exchangers, and the circulation of heat transfer fluid from the vapor compression system <NUM> may be stopped or reduced or continued in parallel to achieve maximum cooling capacity during firing.

<FIG> shows a cross-sectional view of the thermal energy storage system <NUM> as taken along the line A-A depicted in <FIG>. As shown in <FIG>, the thermal energy storage system <NUM> contains a tank or enclosure <NUM>, filled with a heat transfer fluid <NUM>, and having rows of storage tubes <NUM> with an opening in the inner tube <NUM> extending therethrough to form an annular cross-section of the storage tube <NUM>. Each storage tube <NUM> is filled with phase change material <NUM> and disposed within a set of support brackets, baffles or cavities within the tank <NUM>. Each storage tube <NUM> may be cylindrical with a longitudinal cylindrical opening in the inner tube <NUM> extending therethrough to define an inner cylindrical surface and an outer cylindrical surface forming a closed annular volume of the cylinder comprising the respective portion of the phase change material <NUM>.

The size and number of storage tubes <NUM> deposited within the tank <NUM> can be chosen to maximize the thermal transfer of heat from the heat transfer fluid <NUM> circulating in the tank into the phase change material <NUM> within the storage tubes <NUM>. The thermal energy storage system <NUM> may include ten or more, twenty or more, fifty or more, one hundred or more, two hundred or more, three hundred or more, five hundred or more or eight hundred or more storage tubes <NUM>. In some embodiments, there are ten to a thousand of the storage tubes <NUM>.

In some embodiments, the cooling system <NUM> may include multiple thermal energy storage systems <NUM>. Each thermal energy storage system <NUM> may form a "module. " There may be two, three, four, five, six, seven, eight, nine, ten or more of the thermal energy storage systems <NUM> or modules within a system. In some embodiments, the directed energy weapons system <NUM> is a high-energy laser having a power between about <NUM> kW and about <NUM> kW and the system <NUM> includes from two to six or more of the thermal energy storage systems <NUM> or modules. In some embodiments, the directed energy weapons system <NUM> is a high-energy laser having a power of <NUM> kW to <NUM> kW and the system <NUM> includes two, four, six, eight or over a dozen of the thermal energy storage systems <NUM> or modules. In some embodiments, the directed energy weapons system <NUM> is a high-energy laser having a power between about <NUM> kW and about <NUM> kW and the system <NUM> includes one, two, three, or four of the thermal energy storage systems <NUM>.

In this embodiment, the storage tubes may have an outer diameter of <NUM>", but they could be any dimension between ¼" and <NUM>" or even <NUM>" or <NUM>" and functionally similar. Each tank may have <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more storage tubes depending on the specific architecture of the thermal energy storage system. In one embodiment, the tank <NUM> includes about <NUM> storage tubes that are <NUM>" in outer diameter and about <NUM> inches in length.

<FIG> shows an illustration of the control system <NUM>, which is programmed with instructions to control operations of the cooling system <NUM>. The control system <NUM> includes a processor <NUM> which may be any type of well-known microprocessor or microcontroller that is capable of managing the valves, pumps, fans and other components of the system <NUM>. The processor <NUM> is connected to a memory <NUM> for storing programs and commands for operating the system.

The processor <NUM> is connected to a directed energy module <NUM> which includes instructions for activating a cooling cycle in response to the directed energy weapons system <NUM> being activated by firing or anticipated to activated for firing. In one embodiment, the directed energy module <NUM> is programmed to activate the burst mode cooling cycle from the vapor compression system <NUM> and/or thermal energy storage system <NUM> to rapidly cool the thermal load when a predetermined signal is received by the control system <NUM>. The signal may be an activation signal from a firing system connected to the directed energy weapons system <NUM>. With each firing event, the weapon system may interface with a vapor compression control module <NUM> and/or thermal energy storage module <NUM> to trigger the burst cooling mode of the system <NUM> in order to maintain and control the temperature of the weapon system.

In one embodiment, the directed energy module <NUM> communicates with a sensor such as a temperature sensor which monitors the temperature of the directed energy thermal load. In one embodiment, the directed energy module <NUM> activates a burst cooling cycle by interfacing with the vapor compression control module <NUM> when the temperature of the directed energy load reaches a predetermined temperature. For example, when the temperature of the directed energy system is above <NUM>, then the directed energy module <NUM> instructs the vapor compression control module <NUM> to begin rapidly circulating heat transfer fluid to the directed energy weapons system heat exchanger <NUM> and through the thermal energy storage system <NUM>. When the temperature is below <NUM> a heating system is activated to bring up the temperature. In some embodiments, the vapor compression control module may be activated when the temperature of the directed energy load is above <NUM> or above <NUM>. In some embodiments a heating system may be activated when the temperature of the directed energy system is below <NUM> or below <NUM>.

Of course, embodiments are not limited to performing only a single burst cooling procedure. During activation, the thermal load, or an attached weapons system, may request multiple burst mode cooling operations to maintain the temperature of the thermal load below or within a certain target temperature range.

While burst mode cooling can be performed by operating the vapor compression system <NUM> alone or the vapor compression system <NUM> and the thermal energy storage system <NUM>, in some embodiments, the system performs a burst mode cooling cycle by only communicating with the thermal energy storage system <NUM>. For example, as shown in <FIG>, the thermal energy storage module <NUM> may also be activated by the directed energy module <NUM> to begin a cooling cycle in response to the directed energy weapons system <NUM> being discharged. For example, as of a discharge or in anticipation of a discharge the directed energy module <NUM> may instruct the thermal energy storage module <NUM> to begin a cooling cycle. The thermal energy storage module <NUM> would then adjust the input control valves <NUM> and output control valves <NUM> so that thermal heat transfer fluid running through the thermal energy storage system <NUM> begins circulating in a thermal energy cooling loop though the heat exchanger <NUM> adjacent to the directed energy weapons system <NUM>.

The vapor compression control module <NUM> may include instructions for managing the motor, valve and pump functions of the vapor compression system <NUM> as discussed above. For example, the vapor compression control module <NUM> may control the input valves and output valves, along with valves routing thermal heat transfer fluid into and out from the thermal energy storage system <NUM>. By manipulating these valves, the vapor compression control module <NUM> may route thermal heat transfer fluid to the particular components of the system <NUM> as needed to efficiently operate the system.

As shown the vapor compression control module may also include a vector control system <NUM> that is configured as discussed above to provide efficient control of the vapor compression system compressor and torque. For example, the vector control system <NUM> may monitor the torque placed on a compressor within the vapor compression system and adjust the speed of one or more fans or blowers to alter the pressure within the system to increase, or decrease, the torque placed on the compressor to increase the vapor compression system efficiency.

Alternately, the vapor compression control module <NUM> may also include a high voltage DC compressor control system that can easily be operated off high voltage DC battery systems. Such DC system may also monitor torque and serve as vector drive.

After the burst mode cooling requests have subsided, the thermal energy storage module <NUM> may communicate with a sensor such as the temperature sensor within the thermal energy storage system and in response activate the vapor compression system <NUM> and/or nucleation cooling system <NUM> to start cooling the thermal energy storage system <NUM> back down to its target temperature and freeze the phase change material.

As shown, the control system <NUM> also includes a nucleation cooling system module <NUM> for controlling cooling of the phase change media in the thermal energy storage system <NUM>. The nucleation cooling system module <NUM> may include instructions for operating the pump <NUM> to circulate heat transfer fluid from the nucleation cooling system <NUM> through the inner tubes <NUM> of the thermal energy storage system <NUM> to initiate crystallization of the phase change material <NUM> within the storage tubes <NUM>. Data from one or more sensors, such as temperature data from temperature sensors, within the thermal energy storage system <NUM> may be received by the control system <NUM> and the nucleation cooling system module <NUM> may be further programmed to begin, increase the rate of, decrease the rate of, or cease, the flow of heat transfer fluid from the nucleation cooling system <NUM> to the thermal energy storage system <NUM>.

In some embodiments, the nucleation cooling system module <NUM> has instructions to communicate with the vapor compression control module <NUM> when one or more temperatures within the thermal energy storage system <NUM> reaches a certain threshold indicative of a desired amount of crystallization of the phase change material. The instructions may cause the control system <NUM> to then operate the vapor compression system <NUM> to provide further heat transfer fluid to continue the crystallization of the phase change material, to not provide cooling from vapor compression system <NUM> and let nucleation cooling system <NUM> perform the entire charge or any combination thereof. The nucleation cooling system module <NUM> and the vapor compression control module <NUM> may be programmed to circulate refrigerant from the nucleation cooling system <NUM> at a first relatively lower temperature and after initial crystallization of the phase change material based on temperature sensor feedback to then circulate a heat transfer fluid from the vapor compression system <NUM> at a second relatively higher temperature as compared to the first temperature of the refrigerant to continue the crystallization or increase the temperature of nucleation system <NUM> after initial nucleation and operate system <NUM> to complete the freezing process or use both systems <NUM> and <NUM> to complete the freezing process.

In some embodiments, during lasing at maximum thermal load conditions, not only could vapor compression system <NUM> and thermal energy storage system <NUM> be used simultaneously to maximize cooling output, but nucleation system <NUM> may also be engaged at the same time to provide additional cooling through the thermal energy storage system <NUM>.

As shown, the control system <NUM> also includes a hotel load control module <NUM> for controlling cooling of the hotel loads within the system <NUM>. The hotel load control module <NUM> may include instructions for reading data from temperature or other environmental sensors and determining the proper parameters for cooling or heating the hotel load or adjacent systems of the directed energy weapons system. For example, if the hotel load control module <NUM> receives data showing that the hotel load is above <NUM> it may activate the vapor compression system <NUM> to begin a cooling cycle to reduce the temperature of the hotel load back down to a target temperature. Similarly, if the hotel load control module <NUM> determines that the thermal load is below, for example, <NUM> it may initiate a heating cycle of the vapor compression system or an auxiliary heater to increase the temperature of the thermal load up to a target temperature.

It should be realized that aspects of the control system may manage the variable speed operation of various pumps and fans within the system based on the temperature of the thermal load. For example, as the temperature of the thermal load. or surrounding environment, increases the speed of pumps and fans within the system may also increase. Similarly, as the temperature of the thermal load, or surrounding environment decreases, the controller may slow the speed of the pumps and/or fans.

In operation, a cycle may be activated when a directed energy weapons system is first begun to be powered up for use. While the below operation is described for circulating refrigerant to the hotel load and directed energy system heat exchanger, it should be realized that the system is not limited to using phase change refrigerant, and thermal heat transfer fluids may also work similarly within the system.

As can be realized, these systems include ancillary equipment that may need to be cooled before the system becomes fully operational. For example, the ancillary equipment may be powered on along with the vapor compression system. The control system may therefore activate the output control valves such that the refrigerant output of the vapor compression system is routed to the various components of the hotel load heat exchanger, the input control valves are set to recirculate the refrigerant from the hotel load heat exchanger back to the vapor compression system, and the pump is activated to move the refrigerant in a cooling loop to begin removing heat from the hotel load. The nucleation cooling system <NUM> may also be operated to facilitate cooling the ancillary equipment, albeit through the thermal energy storage system in the examples shown in the drawing. Different valving could make the nucleation system also available to hotel loads, if needed.

The control system <NUM> may detect the temperature of the thermal energy storage system <NUM> using a temperature sensor, and determine if the thermal energy storage system <NUM> is cooled to a target temperatures so that it may act as a heat capacitor to absorb excess heat from the system once the system becomes operational. If the control system <NUM> determines that the temperature of the thermal energy storage system <NUM> is above a predetermined threshold it may begin routing thermal heat transfer fluid or refrigerant that has been cooled by the vapor compression system <NUM> and/or the nucleation cooling system <NUM> into the thermal energy storage system. The control system <NUM> may include programming to balance the cooling requirements of the hotel load against the necessity to also cool the thermal energy storage system <NUM>, and determine the priority for each system based on their current temperature and how soon the system may need to use the thermal energy storage system <NUM>.

Once the system is ready to fire, the vapor compression system <NUM> may be put into a standby mode where it is ready to begin burst mode cooling as soon as a firing event is detected or a control signal indicates immediate firing to be initiated. Once a firing event is signaled or detected the system will enter a burst mode cooling cycle. The control system <NUM> will activate the thermal energy storage system <NUM> loop so that heated thermal heat transfer fluid from the directed energy system heat exchanger is routed into the thermal energy storage system and possibly assisted by vapor compression system <NUM> to maximize cooling output.

As the directed energy system heat exchanger <NUM> continues to detect firing events and transfers heat from the heat exchanger <NUM> to the thermal energy storage system <NUM> for burst cooling, the control system <NUM> may monitor each component to ensure that the flexible system is operating efficiently. For example, in one embodiment in the first <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more seconds following activation, the heated thermal heat transfer fluid from the directed energy system heat exchanger <NUM> may not be routed to the vapor compression system <NUM> because the cooling requirement during that firing event may be handled sufficiently by the thermal energy storage system <NUM>. However, as the firing events continue and the thermal load of the directed energy weapons system <NUM> maintains or increases, the control system <NUM> may route a portion of the heat transfer fluid coming from the directed energy weapons system heat exchanger <NUM> directly to the vapor compression system. The nucleation cooling system <NUM> may also be operated as described herein to facilitate freezing of the phase change material within the thermal energy storage system <NUM>.

It should be realized that in some embodiments the vapor compression cooling system <NUM> is used to supplement the cooling provided by the thermal energy storage system <NUM>. Thus, following activation, the thermal energy storage system <NUM> may provide rapid burst mode cooling for the first seconds after the weapon's activation. Then, or even simultaneously, the vapor compression system <NUM> may be activated to provide a secondary cooling loop to the directed energy weapons system heat exchanger <NUM> and provide additional cooling capacity above that provided by the thermal energy storage system <NUM>. Alternately, the vapor compression system <NUM> may be used first with the thermal energy storage system <NUM> following thereafter. In such cases, the nucleation cooling system <NUM> may also be operated to more rapidly cool and freeze, or keep frozen, the phase change material within the thermal energy storage system <NUM>.

<FIG> is a flow chart showing an embodiment of a process <NUM> for facilitation of a phase change material freeze cycle using a nucleation cooling system. The process <NUM> begins at a start state <NUM> and then moves to a decision state <NUM> where a determination is made whether to initiate a freeze cycle. The determination may be made based on temperature sensor data, weapon firing data, or freezing progress of the phase change material. If it is determined in step <NUM> that a freeze cycle is not to be initiated, then the process <NUM> moves to state <NUM> and enters a maintenance mode. In the maintenance mode the nucleation cooling system may be kept off or kept at a current or other operating level.

If a determination is made at the decision state <NUM> to initiate a freeze cycle, then the process <NUM> moves to state <NUM> where the nucleation cooling system is activated. The nucleation cooling system may circulate refrigerant at a first temperature through the inner tubes traversing the storage tubes of the phase change material in the thermal energy storage system to cause nucleation of the material.

The process <NUM> then moves to decision state <NUM> where it is determined if nucleation of the phase change material has initiated. This may be determined, for example by determining nucleation or freezing of the phase change material, or a threshold amount of nucleation, has been initiated. If it is determined in state <NUM> that nucleation or a threshold amount of nucleation has not been initiated, then the process <NUM> moves to state <NUM> where nucleation of the phase change material is continued. The cooling may be continued by the circulation of the refrigerant from the nucleation cooling system through the thermal energy storage system.

If it is determined in state <NUM> that nucleation or a threshold amount of nucleation has been initiated, then the process <NUM> moves to decision state <NUM> where it is determined if the nucleation cooling system will be used to continue freezing of the phase change material, following nucleation. This determination may be made by gathering data from various sensors, such as temperature sensors, or based on the energy consumption or other conditions of the system. If in state <NUM> it is determined that the nucleation cooling system will be used to continue freezing of the phase change material, then the process <NUM> moves to state <NUM> where the nucleation cooling cycle is continued. If in state <NUM> it is determined that the nucleation cooling system will not be used for additional freezing of the phase change material, then the process <NUM> moves to state <NUM> where the nucleation cooling system is shut down. The process <NUM> then moves to a decision state <NUM> to determine if the vapor compression system will be used to continue freezing of the phase change material.

A determination is then made at decision state <NUM>, whether additional freezing from the vapor compression cooling system is needed. For example, if the nucleation cooling system is already activated and freezing the phase change material, then the vapor compression system may not need to be activated to also cool the phase change material within the thermal energy storage system. However, if the nucleation system was only used to initiate nucleation and is not being used to continue freezing the phase change material following nucleation, then the vapor compression system may be activated to continue with the process of freezing the phase change material.

If in state <NUM> it is determined that additional freezing from the vapor compression system is needed, then the process <NUM> moves to state <NUM> where the cooling and further freezing of the phase change material from the vapor compression system is continued. If in state <NUM> it is determined that additional freezing from the vapor compression system is not needed, then the process <NUM> moves to state <NUM> where the vapor compressions system is shut down. This may occur when the nucleation cooling system is already freezing the phase change material.

The process <NUM> then moves to decision state <NUM> where it is determined if all cooling is completed. Such decision may be determined by analyzing data from the various sensors as described. If it is determined in decision state <NUM> that all cooling is not completed, then the process <NUM> moves back to decision step <NUM> and proceeds as described above. If it is determined in decision state <NUM> that all cooling is completed, then the process <NUM> moves to state <NUM> and ends. After this freezing process ends, the thermal energy storage system would typically enter a maintenance mode where the vapor compression system or nucleation cooling system would be used to maintain the phase change material in a frozen state.

<FIG> describes one process <NUM> for cooling a directed energy weapon system, such as a laser weapon. The process <NUM> begins at a start state <NUM> and then moves to a decision state <NUM> wherein a determination is made whether an imminent or current laser firing event has been detected by the control system. If a laser firing event is not detected the process <NUM> moves to state <NUM> and enters a maintenance mode. In the maintenance mode, the system continues to maintain the hotel load at a target operational temperature so that the system is ready to operate once a firing event has been detected. During the maintenance mode the nucleation cooling system and/or the vapor compression system may be used to maintain or recharge the phase change material or media housed within the thermal energy storage system so that the thermal energy storage system is prepared to deliver cooling power to the system when needed.

If a determination is made at the decision state <NUM> that a current or imminent laser firing event has been detected, then the process <NUM> moves to a state <NUM> wherein the thermal energy storage system is initiated to quickly absorb a burst of heat, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more kilowatts of heat energy from the laser system. After activating of the burst mode cooling system at the state <NUM>, the process <NUM> moves to a state <NUM> wherein a cooling loop from the thermal energy storage system and/or the vapor compression system is activated to provide additional cooling power to the laser weapon. These two cooling sources may come on at the same time, for example where the vapor compression system is possibly on already to cool hotel loads at reduced capacity cooling and only needs to ramp up to provide additional cooling power. Because the vapor compression system may take additional time to absorb heat, it may be used as an ancillary cooling supply to the more rapid cooling provided in the first few seconds in a firing event by the thermal energy storage system. In some embodiments, the nucleation cooling system may also be activated in state <NUM> to provide supplemental cooling capacity to freeze the phase change material in the thermal energy storage system. For instance, where very high and/or sustained heating loads need cooling, all three of the thermal energy storage system, the vapor compression system, and the nucleation cooling systems may be used together to provide an ability to rapidly cool the laser weapon system and hotel loads in one scenario.

After cooling is initiated from the thermal energy storage system, vapor compression system and nucleation cooling system at state <NUM>, the process <NUM> moves to a decision state <NUM> wherein a determination is made whether further or additional cooling is needed. The determination may be made based on anticipated firing events to maintain the laser weapons system at its target temperature or range. Typically, this target temperature may be between <NUM> and <NUM>. If it is determined that additional cooling is needed, then the process <NUM> moves to a state <NUM> wherein the flow rate of the one or more cooling loops from the thermal energy storage system, the vapor compressions system, and/or the nucleation cooling system may be increased to help move additional heat away from the laser weapons system. The vapor compression system may be ramped up in cooling capacity to add additional cooling power to the overall system and help maintain the temperature of the laser weapons system in the allowable range.

Claim 1:
A thermal energy cooling system (<NUM>), comprising:
a thermal energy storage system (<NUM>) comprising a phase change material (<NUM>) in thermal communication with a plurality of first heat transfer surfaces (<NUM>) and second heat transfer surfaces (<NUM>);
a first refrigerant or heat transfer fluid in thermal contact with the plurality of first heat transfer surfaces (<NUM>), wherein the thermal energy cooling system is configured to circulate the first refrigerant or heat transfer fluid at a first temperature to at least initiate crystallization of the phase change material (<NUM>); and
a second refrigerant or heat transfer fluid (<NUM>) in thermal contact with the plurality of second heat transfer surfaces (<NUM>) and configured to transfer heat from a thermal load to the plurality of second heat transfer surfaces, wherein the thermal energy cooling system is configured to pump the second refrigerant or heat transfer fluid at a second temperature that is higher than the first temperature,
characterized in that
after the crystallization of the phase change material (<NUM>) is initiated, the thermal energy cooling system is configured to circulate the first refrigerant or heat transfer fluid or the second refrigerant or heat transfer fluid (<NUM>) at a higher temperature than the first temperature to freeze the phase change material.