WO2015061717A1

WO2015061717A1 - System and method for a regenerative heat engine cycle using reversible metal hydrides

Info

Publication number: WO2015061717A1
Application number: PCT/US2014/062225
Authority: WO
Inventors: Kimberly Peacock
Original assignee: Fkw, Inc.
Priority date: 2013-10-25
Filing date: 2014-10-24
Publication date: 2015-04-30

Abstract

A heat engine that includes reversible metal hydride pairs of a same material type. One of the pairs alternately acts as a positive hydrogen displacement pump and the other simultaneously acts as hydrogen storage and heat pump. A hydrogen receiver is thermally coupled via a network of heat pipes to a thermal battery and heat pump, which uses the hydrogen mass flow from hydrogen pump and the heat rejection from hydrogen storage to power to heat pump and thermal battery and initiate a sinusoidal signal which makes heat engine a hydride chemical oscillator.

Description

SYSTEM AND METHOD FOR A REGENERATIVE HEAT ENGINE CYCLE USING

REVERSIBLE METAL HYDRIDES

FIELD OF THE INVENTION

[0001] The present invention relates broadly to a regenerative heat engine and more particularly to a regenerative heat engine where internal energy is maintained during an engine cycle.

BACKGROUND OF THE INVENTION

[0002] A heat engine is a system that converts heat energy into mechanical motion, which can then be used to do work. An objective of a heat engine is to minimize energy used to produce power and maximize the work generated from the flow of energy.

[0003] A heat engine's efficiency is theoretically limited by Carnot's theorem where the maximum ratio of work generated to thermal energy flow for a single engine cycle is limited by the temperatures available at a high temperature source and a cold temperature sink. Some energy input into the engine must be rejected. [0004] While an engine cannot produce more work per cycle than the Carnot efficiency allows, the engine can be made to approach that efficiency. In conventional heat engines, heat energy is absorbed at a higher temperature and rejected to the colder sink where the energy is lost. Capturing thermal energy rejected to the sink by a non-Carnot engine and recycling that energy within the limits of the Carnot theorem can improve the energy efficiency of heat engines. [0005] Over the years, the regenerative class of heat engines (e.g., Stirling, Rankine, Schoel, Brayton) have attempted to improve engine efficiency by capturing the energy of a cycling engine and reusing it so that less energy is needed to be injected and rejected in order to cycle the engine. One of the regenerative engines, the Stirling Engine, for example, differs from hot air engines by including a regenerator, which is designed to operate at a mean temperature between an internal hot and cold source and provide cooling during a compression stroke and heating during the expansion of a gas stream. However, a regenerator can only hold a small percentage of energy in relation to the overall energy flow and an internal regenerator also cannot store the maximum potential of a source or sink. Although Stirling engines can operate on a very low temperature difference (e.g., as low as ½ Kelvin), they provide little useable power. Using a double opposed Stirling engine at very high pressures which requires a large area of heat exchange to stroke distance, confronts material limits to how much pressure and how large a heat source and sink area can be made when minimizing stroke distance. [0006] One way to overcome this limitation is discussed, for example, in U.S. Patent No. 7,898,155 where a chemical heat engine is used to store a gas in a solid state and the gas is then released, which results in displacement of a piezoelectric or electro-active membrane.

[0007] However, regenerative heat engines capture only a small part of energy flow. Temperature potentials are a mean between a heat sink and heat source. High temperature differentials lead to greater work output, but even greater amounts of thermal energy are rejected, as most heat engines demand a large temperature difference to cycle. As such, heat engines are not readily powered from natural ambient temperature sources and sinks (e.g., ocean, earth, or ambient temperatures).

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a heat engine having a cycle where internal energy is maintained. Because the engine cycle does not reject much heat energy to the environment, the engine itself can change in temperature and internal energy based on the environmental temperature, which must be at a minimum to keep internal energy at a minimum for the engine to cycle.

[0009] A suitable temperature source, for example, is 20 meters below the earth's surface where the temperature represents the average constant within a ½ Kelvin annually is a suitable source for example on the temperature at this depth on Long Island NY is 283.15 Kelvin. The invention can also be powered by the ocean down to the freezing point of 253.15 Kelvin, which means that these thermal resources can be considered thermal batteries charged by the sun. Thus, these thermal resources can be considered to be thermal batteries charged by the sun. It takes must less energy to maintain a room that contains the engine at constant temperature when insulated, and taking into account the maximum and minimum ambient temperatures than a conventional engine rejecting thermal energy to the environment during each cycle.

[0010] The engine cycle is lossless because the hot temperature during an engine cycle never rises above ambient, which locks the internal energy within the engine as heat flows from hot to cold. For internal energy to flow out of an engine, the engine temperature would have to be higher than ambient. A temperature differential is generated, but this differential oscillates with each cycle generating a sinusoidal signal (e.g., just like the thermal signals of the seasons stored in the ground). The temperature may change at the surface, but at a certain depth the signal cancels out and is constant. The regenerator is external to the power stroke of the engine and therefore all thermal energy can be captured at a lower potential internally and converted to a higher potential.

[0011] In an embodiment, the present invention is directed to a regenerative heat engine with a lossless heat engine cycle, comprising a pair of reversible metal hydrides, which oscillate between functions of a hydride hydrogen pump and a hydrogen store, and in which the chemical reactions of releasing hydrogen and absorbing hydrogen are conveyed to a thermal battery and a heat pump. The hydrogen mass flow between the hydride pairs is in a closed pipeline with an expandable volume capable of transmitting force over distance and the maximum temperature in the engine is ambient temperature, whereby internal energy cannot be lost as a result of thermal transfer, because heat must flow from hot to cold, and where thermal battery as a sink, which is 20 Kelvin lower than ambient, and where hydride storage is connected to the sink via heat pipes. In one embodiment an expandable volume with a compressible fluid/refrigerant is allowed to expand thereby lowering the temperature of storage hydride, and whereby the reaction of absorbing hydrogen converts more of the refrigerant in the expandable volume from liquid to gas thereby expanding the expanding volume. The expansion volume is connected to a compression volume, such that the expansion from the heat rejected by the hydride storage absorbing hydrogen is conveyed to the refrigerant vaporizing and the work output from the expansion, and is captured to provide power to the heat pump, which compresses a compressible fluid/refrigerant. The heat of compression is at a pressure whereby it will compress at ambient, and is connected via heat pipes to the hydrogen pump, such that all hydrogen mass is moved from the hydrogen pump to storage, and at which point, compressible volume on the thermal battery is allowed to expand, thereby cooling the hydride which in the previous cycle was the hydride hydrogen pump, and which now is devoid of hydrogen. Simultaneously this expansion of the refrigerant volume in the thermal batteries expandable volume attaches to the hydride, which formerly was the pump but now is the storage, compressing some of the refrigerant in the expandable volume attached to now what is the hydride pump, and the heat of condensation is transmitted to the hydride hydrogen pump, thereby raising its temperature to ambient and at which point the expandable volume between the hydride hydrogen pump is allowed to expand and hydrogen flows from the hydride hydrogen pump to the expandable volume and from there to the hydride hydrogen store.

[0012] In an embodiment, the thermal battery is comprised of two hydride pairs of different material types. The hydride used as the sink for the hydride hydrogen store is a high pressure hydride and the hydride used as a hydride hydrogen store is a low pressure hydride. During cycling, one of the hydride pairs can be selected depending on which one is the hydrogen pump and which one is the hydrogen storage. The thermal battery hydrides can be selected based on a heat of reaction and a mass storage similar to the drive hydrides. Hydrogen can flow out of the thermal battery hydride and into an expandable volume such as a hydraulic accumulator or similar device where the pressure volume of the hydrogen mass is stored momentarily, which is thermally connected to the drive hydride storage. This cools the hydride hydrogen storage by 20 Kelvin below ambient temperature. The expandable volume is then compressed by the accumulator or similar device that is triggered to send pressurized hydrogen into the low pressure thermal hydride, which is thermally connected to the hydride hydrogen pump. As the hydride thermal battery is matched to the hydride hydrogen pump, thermal energy is alternately absorbed and released driving the pump, and because temperature is not allowed to rise above ambient, the engine is insulated and the thermal cycle between hydrides results in a sinusoidal signal, internal energy is kept within the engine based on the temperature of ambient (ambient being at a sufficient level) that internal energy is high enough to run the cycle.

[0013] In an embodiment, the thermal battery comprises two chambers that include different variable pressures from deep vacuum to ambient. A heat pipe can connect the chambers to a hydride pair of a hydride hydrogen pump and a hydride hydrogen storage. The hydride hydrogen storage can be connected by heat pipes to a liquid (e.g., water), which evaporates at a reduced temperature as a result of being under vacuum. As the liquid vaporizes, it reduced the temperature of the liquid by 20 Kelvin below ambient. At this point, the expandable volume between the hydride hydrogen pump and the hydride hydrogen storage is allowed to expand and hydrogen is absorbed by the hydride hydrogen storage, as the heat pipes connected to the thermal battery chamber with the vaporizing liquid is 20 Kelvin below ambient, and as it absorbs hydrogen it passes it to the liquid which vaporizes as a result. The vacuum is generated by a Venturi, which is powered by the compressed fluid after it has expanded in the heat exchanger and alternately the compressed fluid is channeled through a blower to develop a deeper vacuum. The liquid vapor in the thermal battery is conveyed by a channel between the thermal battery chambers where it is heated by heat rejection from the compressible fluid, where hydride hydrogen pumps expandable volume is applying its force to compress air or a refrigerant (e.g., double acting pump), and the heat is rejected to the vapor stream via heat pipes, and the pressure is allowed to increase until it condenses at ambient temperature and this is conveyed to the hydrogen hydride pump which compresses the compressible fluid, a refrigerant or air, and rejects its heat to the vapor increasing its temperature and allowing pressure to increase until it condenses. When all the hydrogen has been transferred from the hydride hydrogen pump to the hydrogen storage, then compressed fluid, which has had its heat rejected and expanded into a heat exchanger absorbs heat.

[0014] In an embodiment, the expandable volumes of the thermal battery are made of electro-active polymers with embedded piezoelectric materials such that expansion and contraction generate an electrical signal which powers the thermoelectric element that is connected between the thermal batteries source and sink and the hydride hydrogen pump and the hydride hydrogen storage, and signaling is such that polarity can be reversed providing a direction of heat transfer and improved heat transfer. [0015] In an embodiment, the expandable volume of the hydride hydrogen pump and hydride hydrogen storage hydride pair drives a yoke and flywheel.

[0016] In an embodiment, the expandable volume of the hydride hydrogen pump and hydride hydrogen storage drives an air compressor.

[0017] In an embodiment, the expandable volume of the hydride hydrogen pump and hydride hydrogen storage pair drives a double diaphragm hydraulic pump. [0018] In an embodiment, the thermal battery includes two chambers under various pressures from deep vacuum to atmospheric pressure where the energy supplied to provide enhance the vacuum is generated by a water and zeolite pair. The zeolites affinity for water vapor generates an exothermic reaction and brings down the vapor pressure. There are two such zeolite chambers, one is recharged and the other is active at any time. The zeolites are recharged from heat rejection from a compressible fluid while under partial vacuum. Where heat generation from the zeolites is conveyed via heat pipes to a liquid antifreeze, and where the liquid chamber has heat pipes connected to a chamber with liquid antifreeze, and where antifreeze chambers are circulated by a pump powered by the compressible fluid generated by the hydride hydrogen pumps expandable volume, and there are reversing valves to alternately direct the warm and cold antifreeze to the hydride hydrogen pump and hydride hydrogen energy storage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a chart that shows energy transfer of a hydride pair at a temperature difference where a hydride hydrogen pump has an equilibrium pressure that is twice that of the hydride hydrogen storage;

[0020] Figure 2 is a schematic diagram depicting flow of a thermochemical hydride hydrogen pump;

[0021] Figure 3 A and 3B depict schematic diagrams of embodiments of the present invention for a lossless heat engine cycle where a vapor compression system is used for the thermal battery; [0022] Figure 4 is a schematic diagram of an embodiment for a regenerative heat engine cycle of the present invention;

[0023] Figure 5 is a schematic of a hydride hydrogen air- water thermal battery of the present invention; and

[0024] Figures 6 and 7 are schematics relating to thermal energy of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0025] Figures 1-7 illustrate aspects of embodiments of a system and method for a heat engine and a lossless heat engine cycle of the present invention.

[0026] Figure 1 is a chart of the present invention that shows energy transfer of a hydride pair at a temperature difference where a hydride hydrogen pump has an equilibrium pressure that is twice that of the hydride hydrogen storage.

[0027] Figure 2 is a schematic diagram of the present invention relating to a thermochemical hydride hydrogen pump. As shown, by raising the temperature of the hydride, the equilibrium pressure is also increased. If the gaseous pressure is above the equilibrium pressure then hydrogen is absorbed resulting in an exothermic reaction generating heat. This reaction is over 20 KJ per 2.02 grams of hydrogen absorbed. The rate of absorption is proportional to how quickly the heat generated and the thermal energy can be transferred out of the hydride. If gaseous pressure is below the equilibrium pressure, hydrogen is then released by the hydride and an endothermic reaction is generated of over 20 KJ per 2.02 grams of hydrogen released. Thermal energy must be supplied to the hydride releasing hydrogen at a rate of over 20 KJ per 2.02 grams of hydrogen or the temperature of the hydride will decrease and therefore its equilibrium pressure will decrease.

[0028] Figures 3A and 3B illustrate schematic diagrams of the present invention where a hydride hydrogen pump 1 is at ambient temperature, where the equilibrium pressure is higher than the pressure in the hydrogen path 2. Hydrogen flows from the hydrogen pump 1 through 2 to a pilot valve 5, which selects an expandable volume. Such mechanisms are common in double acting pumps and pistons, such as double acting diaphragm pump. A linkage 7 between expandable volumes such that when one is expanding the other is contracting. The hydrogen on contraction exits through a valve which blocks hydrogen from escaping hydride expandable volume expanding, and open a port from hydride hydrogen expandable volume undergoing compression. This hydrogen mass flow powering the pump is the result of thermal input into 1 from 15 via 16 and heat rejection from 9 to 11 via 10. When hydrogen is released from the hydride hydrogen pump it is accompanied by an endothermic reaction in the range of - (20-30) KJ per Mol (2.02 grams of Hydrogen) and on absorption the opposite exothermic reaction occurs with a + (20-30) KJ reaction. To maintain equilibrium pressure and transfer the hydrogen stored and out of the hydride hydrogen pump 1 , thermal energy must be supplied equal to the endothermic reaction and the mass flow is proportional to the rate at which we can move this thermal energy in and out of the hydride pair. So although other thermal transfer methods may be used, heat pipes 16 and 10 are the preferred method of transferring thermal energy from 15 to 1 and 9 to 10. In Figures 3 A and 3B it is shown that the positions of hydrogen hydride pump and hydride hydrogen storage switch positions 1 and 9, and that in the thermal battery source and sink 11 and 15 switch positions, and in the thermal battery expandable volumes switch from being compressed and expanding 12 and 14. During each cycle when hydrogen has been completely transferred from 1 to 9, the cycle momentary dwells and the hydrogen expandable volumes are locked and in the thermal battery 12 and 14 swap positions. 14 expands and becomes 12 as a result of the linkage control valve reducing the pressure constraints, and this results in a refrigerant vaporizing and increasing in volume, which is communicated via the linkage 13 to expand 12 compressing 14 which delivers the heat of condensation via 10 to 1 the hydride hydrogen pump, this occurs while hydride hydrogen expandable volumes are locked such that no hydrogen mass is flowing, and this lowers the temperature of 9 by 215-20 Kelvin below ambient, while increasing the temperature of 1 up to ambient, at which point the lock on linkage 7 is released and hydrogen is allowed to flow from 1 to 2 through 5 and 4 or 3 and out through 6 to 9.

[0029] The refrigerant used in the thermal battery must have a high heat of vaporization and condensation, and the mechanical input for compression must be less than the power developed from the hydrogen mass flow of 1 plus and resistive loads on 3, 4, and 9, and the power generated from expansion of refrigerant at reduced pressure just below the condensation pressure at a temperature 20 Kelvin below ambient temperature. This allows a constant temperature and pressure of condensation and vaporization, expansion and compression respectively. There are Hydrides such as CeNi5H6 which have an equilibrium pressure of 613 PSI at 283.15 Kelvin which allow such an engine run on ambient temperature conditions, with refrigerants like Propane. CeNi5H6 doubles and halves in equilibrium pressure in 15 Kelvin increments and therefore the temp differences is only 15 Kelvin and this sets up a COP of over 19. One can use refrigeration cycles and choose propane and get a COP of over 16, but this reflects raising the temperature above 15K difference because in such a system there is not the connected chemical heat source and sink which the hydrides represents.

[0030] As shown in Figure 4, in an embodiment of a hydride thermal battery of the present invention, hydrogen can flow from a high pressure hydride through a pipe 11 and a valve to a double diaphragm 8. The double diaphragm 8 is connected to a gas accumulator 6, which in turn is connected by a gas pipe line 10 and a valve to a low pressure hydride 7.

[0031] During an engine cycle, all of the hydrogen is transferred from one of the hydride pairs to the other hydride pair and the hydride hydrogen pump is adapted to become the hydride storage. If the hydride hydrogen pump is at ambient temperature, the temperature must first be reduced so that it can became a suitable hydrogen storage for the hydride hydrogen pump. As such, hydrogen flows out of high pressure hydride 3 to

11 to 8 and temperature of the alloy drops until it is 20 Kelvin below the ambient temperature and as 3 is connected by 17 a heat pipe to 2, the temperature of hydride storage 2 is reduced. Simultaneously, when the high pressure hydride 3 starts releasing hydrogen, it activates the accumulator 6, which is connected by pipe 10 to 7, and the accumulator which stores hydrogen under a pressure volume is delivered to low pressure hydride 7, raising the temperature of the alloy to ambient, and as the low pressure hydride 7 is connected to 1 by 16, a heat pipe the temperature of 1 increases to ambient. At which point, the linkage on 15 is open and hydrogen flows from 1 through 18 or 19 and to 2. The thermal energy of the exothermic reaction at 2 absorbing hydrogen is transferred to the high temperature hydride 3 which pumps its hydrogen through 11 a pipe and valve which is open to a double diaphragm pump 8, which is actuating an accumulator the accumulator is used such that we can provide heating and cooling simultaneously. Hydrides are used which are formulated such that high temperature hydride is just above equilibrium pressure of low-pressure hydride at 20 Kelvin below ambient.

[0032] Figure 5 is a schematic illustrating a hydride hydrogen air-water thermal battery of the present invention. Hydride 1 and 2 represent a pair of reversible metal hydride connected to a double diaphragm pump 14, which is connected to a hydraulic motor 13, which in turn provides hydraulic fluid power to an air compressor 8. The heat of compression of the air from the air compressor 8 is passed via 7 to a heat pipe 26, which is attached to an air water heat exchanger 27, which receives thermal energy input from the condenser 25 as an air circuit traverses condenser 25 to the heat exchanger 27 and is controlled by a reversing air valve which selects for the hydride releasing hydrogen, and the air stream exits via the air manifold 5 as the average temperature of air temperature of both absorbing and desorbing hydride which should be ambient, where it flows into the air compressor 8. The pressure in 25 is allowed to increase from partial vacuum up to ambient to condense water vapor at ambient temperature conditions, where the vapor goes to an insulated water tank 24, and an air operated diaphragm pump 23 pumps it to water chiller 17 where it flows through cross flow heat exchanger exchanging its thermal energy with the air stream on to number 6 a reversing air valve which selects hydride 1 or two based on which is absorbing hydrogen ensuring that the absorbing hydride is maintained at a temperature 20 kelvin below ambient. As air is compressed it's conveyed to an air tank 9 where it is regulated at a controlled pressure to an air motor 11 , where the exhaust air goes through a cross-flow heat exchanger, as heat of compression removed internal energy from the air stream and expansion cools the air even further much like a rankine turbine thermal energy should be picked up from the environment and ambient temperature should restore working pressure of the exhaust fluid, rotary tesla valves are utilized to prevent backflow and set up a pulsing pattern which alternate drops pressure on one side and increases it on the other. The air pipe passes through the water chiller and on to 20 which provides and air supply to 23 via 21 and selects 19 or 22 depending on the vacuum level needed in the chiller 18. The water chiller uses vacuum to lower the vaporization temperature of a liquid such as water. As system has a compressed air stream is available in system using air stream for Venturi is extremely efficient and provides rapid vacuum down to a temperature of vaporization of 283.15 Kelvin, below this level a roots blower type vacuum is employed which because there is minimal pressure to blow against uses very little energy to generate the vacuum. In a variation of this a zeolite chamber can be embedded in the condenser which will itself act as a getter reducing the need for a rotary vacuum pump but one would need the condenser to have two chambers where one is being recharged at higher temperature where water vapor is exhausted to water tank and heat input is rejected to the heat exchanger and an electrical connection from generator 12 in a parasitic load to recharge said zeolites under partial vacuum. [0033] Figures 6 and 7 show schematics where thermal energy is stored within a material or gas, where a heat pump, thermoelectric element, such as a peltier device lifts thermal energy storage up to the temperature of ambient, from the energy storage which is collected at 20 Kelvin below ambient. The reason for doing so is that its cost much less energy to transfer energy than to generate it and rejects it, at a temperature difference of only 20 Kelvin we have a coefficient of performance of greater than 16, which is developed by the pressure difference of the hydride pair on the hydrogen pump by providing a sink 20 Kelvin below ambient. This is possible because thermal energy is exchanged round robin from hydride to thermal battery and from thermal battery to hydride. The pressurized flow potentials runs counter to the thermal flow potentials. Where the absorbing hydrides heat rejection to the thermal battery sink generates work, which contributes to the work input required to lift the temperature up from the 20 Kelvin below ambient. The thermal battery sink uses entropy to collect the thermal energy from sink at a lower temperature and pressure, which is used to convert the thermal energy rejected to a more dense higher pressure and temperature configuration, whereby the remaining energy input comes from the work output of the hydride hydrogen pump and the pressure difference set up by them having a temperature difference of 15-20 Kelvin.

[0034] The hydride hydrogen volumes can use electro active polymers and piezoelectric materials to generate electricity, which can power peltier junctions to improve thermal transfer and provide an electronic heat pump. And the same can be done on a thermal battery, which has expandable volumes.

[0035] In an embodiment, the heat engine is a regenerative engine that includes at least two reversible metal hydrides or metal hydride pairs, which are thermally coupled to a heat pump by a plurality of heat pipes. Work output from the phase change of one of the metal hydrides to hydrogen plus alloy and the phase change from liquid to gas expansion of the refrigerant coupled to the hydride being formed, and work output being combined to compress refrigerant to drive condensation of refrigerant, and in which the heat of vaporization is used to drive the hydride releasing hydrogen.

[0036] In an embodiment, the engine cycle comprises the following steps:

[0037] (1) The volume containing a condensed refrigerant is connected by a network of heat pipes to a hydride alloy with a volume of hydrogen at a pressure which is below the equilibrium pressure of the hydride (equilibrium pressure of the hydride is equal to or greater than outside pressure), a value attached to the refrigerant volume is opened and allows the refrigerant to expand lowering the pressure of the refrigerant and its boiling point and cooling the refrigerant, which transfers heat from the hydride alloy lowering it temperature and thus its equilibrium pressure until the hydrogen volume attached to the hydride alloy is greater than or equal to the equilibrium pressure, at which point the hydrogen is absorbed by the hydride alloy and the heat of reaction is passed to the liquid refrigerant resulting in vaporization and expansion of the refrigerant volume.

[0038] (2) The hydrogen volume attached to an opposite phased and paired hydride is at the minimum volume and it equilibrium pressure is below the outside pressure exerted by the hydrogen volume. The hydrogen volume is constrained in volume by a valve. The attached refrigerant is compressed by the expansion of the opposite paired refrigerant attached to the hydride absorbing hydrogen, and this raises the temperature of the hydride and thus its equilibrium pressure. When the hydride reaches a set temperature and equilibrium, the valve opens to the hydrogen volume allowing it to expand. The equilibrium of the hydride is greater than the outside pressure which will result in the hydrogen flowing from the hydride to the hydrogen volume with the heat of disassociation, an endothermic reaction being proportional to the condensing of the refrigerant and its passing the heat condensation by a network of heat pipes to the hydride disassociating hydrogen. The pressure and volume displacement of the hydrogen volume contributes a proportional work output to the compression of the refrigerant being condensed with the refrigerant being expanded with left over pressure and volume displacement used to power a hydraulic pump, which can be attached to an electrical generator for electrical power output.

[0039] (3) Upon complete expansion of the hydrogen volume, the attached refrigerant to the hydride alloy with minimum hydrogen store is fully condensed which in turn opens a valve. Steps 1 and 2 are then repeated on the opposite paired sides.

[0040] One advantage of the heat engine is that it is driven by internal energy within the system. Hydrides having a high equilibrium pressure at temperatures below 10°C can be used such as Ceni5 and TicrMn. This allows one to use solar power and geothermal energy such as that used in geo-exchange systems, where on average at a depth of 20 meters the temperature is constant. In addition, it opens up ocean thermal energy to where it is viable on 80% of the earth's surface instead of just at a few locations. At a small depth below the ocean's surface, like geothermal temperature is stable annually. Using a refrigerant (e.g., propane) or a two stage refrigerant system (e.g., trans critical Co2 with zeolite thermal storage and hydrides such as cENi5 >H6 or Ticrmn) or any other high pressure hydride at low temperatures can allow operation down to temperatures of 0°C, which opens up the entire surface of the ocean for generating power. In essence, this is representing inexpensive ocean thermal energy conversion. In particular, because on average at 100 feet of depth the temperature difference at the coldest time of the year at the surface and the temperature at 100 feet is just 1.5°C such a system may be created.

[0041] As this engine is driven by internal energy, which is kept from being in equilibrium by phase change transfers and values that restrict the flow path thermodynamically, energy is lost or gained by wither loss or mass and or thermal losses as a result of the outside ambient temperature being lower than the outside temperature of the engine.

[0042] If the temperature outside of the engine is higher than that of the engine average, the engine will then gain internal energy. If it is lower, it will lose internal energy, but if it is held at a constant temperature, it will remain at the same internal energy.

[0043] The internal energy of the engine is represented by the states of the working fluids, the chemical reactions and the specific heat capacity of the engine.

[0044] The momentary expansion of refrigerant cools the hydride within the engine as a signal only travels a small distance within the engine. The compression of the refrigerant only restores the hydride to ambient temperature conditions.

[0045] The refrigerant expansion and contraction are equal in magnitude in temperature change so over the time of two cycles they average a zero change unless within that time period a thermal signal either lower or higher can travel from the outside to the inside of the engine. In such an event, even if the magnitude of that change is not large, some work may be lost to compress the refrigerant to a higher temperature, which will be rejected to the outside, providing a new internal energy equilibrium

[0046] The thermal signaling is similar to that which is encountered in low temperature geothermal applications, which is just the earth being used as a thermal body.

[0047] Therefore, it is critical to have a cycle time which is less than the time for a thermal signal to travel through the engine to or from the outside and increase or decrease the internal energy of the engine.

[0048] Although the description above and accompanying drawings contains much specificity, the details provided should not be construed as limiting the scope of the embodiments, but merely as describing some of the features of the embodiments. The description and figures should not to be taken as restrictive and are understood as broad and general teachings in accordance with the present invention. While the embodiments have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that modifications and variations to such embodiments, including, but not limited to, the substitutions of equivalent features and terminology may be readily apparent to those of skill in the art based upon this disclosure without departing from the spirit and scope of the invention.

Claims

CLAIMS What is claimed is:

1. A regenerative heat engine, comprising; a plurality of reversible metal hydrides, including a first pair of metal hydrides and a second pair of metal hydrides, the first pair of metal hydrides thermally coupled to a hydrogen pump and the second pair of metal hydrides thermally coupled to a hydrogen storage; wherein the pump having an expandable volume in a closed loop between hydride pairs, in which an expandable volume uses hydrogen pressure volume from the hydride hydrogen pump to hydride hydrogen storage to apply a force to move a substance a distance; and said engine comprises thermal storage which provides a heat sink for the hydrogen storage and a heat pump and source for the hydride hydrogen pump.

2. A regenerative heat engine according to claim 1, wherein the thermal battery is comprised of an expandable volume and compressible volume, wherein expansion contributes to compress the compressible volume and wherein thermal battery uses a refrigerant which condenses in the compressible volume and expands in the expandable volume, and where both compressible and expandable volumes have heat pipes connecting heat transfer from the compressible and expandable volumes of the thermal battery to the hydrides where heat of condensation from compressing refrigerant is condensed at a pressure equal to condensing at ambient temperature, and transferred to the hydride hydrogen pump, and where the refrigerant in the expanding volume is allowed to expand at a pressure, which drops the temperature of the refrigerant to below ambient temperature and serves as a heat sink for the hydride hydrogen storage.

3. A regenerative heat engine according to claim 1, wherein the thermal battery comprises separate hydride pairs known as thermal battery source hydride and thermal battery hydride sink, and where hydrides are of different types, where sink hydride is a high pressure hydride relative to heat source hydride which is a low pressure hydride, and where there is a closed path between hydrides and where the chemical reactions of the hydrogen release and absorption match those of the hydride drive pair of the hydride hydrogen pump and hydride hydrogen storage, and where there is an expandable volume where hydrogen can flow from thermal battery hydride sink and store the pressure volume of the hydrogen mass flow, thereby reducing its temperature and where because hydride thermal battery sink hydride is a high pressure hydride as it reduces in temperature it still has sufficient pressure to the thermal battery hydride source for it to absorb hydrogen and reject heat at a temperature equal to ambient and in which heat pipes connect hydride thermal battery source and sink to drive hydride hydrogen pump and storage.

4. A regenerative heat engine according to claim 1, wherein the thermal battery has two chambers of a sink and source which alternate, and which are under a partial vacuum, where a liquid is vaporized and the vaporization results in the liquid cooling to below ambient conditions, and where the vapor is condensed by allowing pressure to rise, and is heated by the compression of a compressible fluid being rejected to the vapor stream, and where the fluid in both the sink and source are communicated to heat pipes attached to hydride hydrogen pump and hydride hydrogen receiver, and where a reversing valve is used to alternately provide a sink or source to the hydride, and where heat rejected from the hydride hydrogen storage is delivered to the sink, increasing vaporization rate, and where hydride hydrogen pumps expandable volume is applying compression to a compressible fluid, and where the compressible fluid heat is rejected to the condensate, and wherein on expansion the compressible fluid is channeled through a Venturi to draw a vacuum, and wherein the compressible fluid is conveyed to a heat exchanger, and wherein heat exchanger conveys heat from ambient to the compressible fluid on expansion, and where expansion of compressible fluid operates a blower which further reduces vacuum pressure when needed, and where compressible fluid operates a gas motor or pump.

5. A regenerative heat engine according to claim 1, wherein expandable volumes are made of electro-active materials with piezoelectric materials, and where deformation generates electrical signal, and where electrical signals are conveyed to a thermoelectric element which increases heat transfer, and converts hydrogen mass flow to electric power.

6. A regenerative heat engine according to claim 1, wherein heat pump is a thermoelectric element and where expandable volume is an electro active polymer with embedded piezoelectric elements embedded, and whereby the electrical signals are conveyed to the thermoelectric element.

7. A regenerative heat engine according to claim 1, wherein the expandable volume of the pumps drives a yoke and a flywheel.

8. A regenerative heat engine according to claim 1, wherein the expandable volume drives an air compressor.

9. A regenerative heat engine according to claim 1, wherein the expandable volume comprises a double diaphragm hydraulic pump.

10. A regenerative heat engine according to claim 1, wherein a thermoelectric element connects hydride hydrogen pump to hydride hydrogen storage, and wherein a thermal battery contains an expandable volume which contains electro active polymers with embedded piezoelectric elements and the signals are conditioned and controlled to power and regulate the thermoelectric element.

11. A regenerative heat engine according to claim 1 , wherein the vacuum is supplemented by a zeolite and water pair, with the zeolite providing thermal energy up and beyond ambient, and the zeolite reducing vacuum level to the point that water will freeze, with the water chamber as heat sink to the hydrogen storage, and the zeolite a heat source for the hydride hydrogen pump.