IL177522A - System and method for power generation by hydrothermal means - Google Patents

Description

SYSTEM AND METHOD FOR POWER GENERATION BY HYDROTHERMAL MEANS 177522/3 SYSTEM AND METHOD FOR POWER GENERATION BY HYDROTHERMAL MEANS FIELD OF THE INVENTION The present invention relates to a system and method for generating power by hydrothermal means, and adaptations of the system for producing hot water for commercial and private uses.

BACKGROUND OF THE INVENTION In view of global warming, alternative energy sources are at various stages of development. Perhaps the single most important non-polluting energy source being considered is solar radiation. However, up until now the cost of generating power using solar energy far exceeds that of generating electricity from fossil fuels.

Two decades ago a major power plant was built in the California desert for generating power using solar energy. It used solar radiation to generate steam which actuated gas turbines which in turn activated a generator for producing electricity. The solar radiation was collected by a bank of solar collectors through which oil was passed and heated to a temperature of 300°-400°C. The heated oil then transferred heat to a water reservoir generating steam.

The cost of building the power plant, planned to generate 80 MW, was about $280 million. The plant used a field of solar panels extending over 500000 m2. This translated into a fixed cost of $3500 per kW. The plant's operational cost was about 12 cents per kW while its efficiency was about 1 1 %.

Subsequently, another power plant was built, this time in the region of the Dead Sea, which used solar energy and operated on the same general principles as the California plant. However, instead of steam, heated Freon® gas was used to activate the gas turbines. It was found that the heated Freon® gas corroded the turbines in a relatively short period of time.

In view of the above, a need exists for a cheap power generating system based on solar energy. It would be desirable to develop a power generating system based on solar energy which uses relatively inexpensive components, requiring little maintenance 177522/2 and which can be operated at low temperatures. It would be further desirable if the system operated at temperatures which could be varied. Additionally, it would be desirable if such systems could be adapted to provide hot water for private and commercial uses.

SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to provide a low cost power generating system based on solar energy which can operate at lower temperatures than prior art power stations.

It is a further object of the present invention to provide a power generating system which can operate at any of several temperatures and incorporates a hydrothermal means for generating energy. The system should require little maintenance.

It is yet another object of the present invention to provide a method for generating energy by hydrothermal means.

It is a further object of the present invention to provide a system for generating hot water in commercial and residential settings.

There is thus provided in accordance with one aspect of the present invention a system for generating power. The system is comprised of a working liquid and a low-boiling point fluid flowing through the system with the working liquid. The system also includes at least two flow-through tanks, including a first tank and a second tank, through which the working liquid and the low boiling point fluid flow and a first conduit and a second conduit for connecting and bringing the first and second flow-through tanks into fluid communication with each other. The system additionally includes one or more power generating means in fluid communication with one of the first and second conduits. At least a portion of the low boiling point fluid in the first tank is in its gas phase forming bubbles causing the working liquid and the low boiling point fluid to flow from one of the first and second flow-through tanks to the other and then back again. This flow passes through the first and second conduits and the working liquid while passing through one of the first and second conduits activates the one or more power generating means, thereby providing power.

In one embodiment of the system, the tanks are formed as tubes and the one or 177522/2 more power generating means are two power generating means. The two power generating means are a heat exchanger and a condenser. The heat exchanger removes heat from the working liquid, the low boiling point fluid and the bubbles therein, and transfers heat to its surroundings. The condenser liquefies the bubbles causing them to reform low boiling point fluid while providing heat to the surroundings of the condenser.

In a further embodiment of the system having a condenser and heat exchanger there is an energy collector through which the working liquid and the low boiling point fluid flow absorbing a portion of the collected energy. The low boiling point fluid at least partly changes to its gaseous phase forming bubbles within the working liquid.

In additional embodiments of the system, the system further includes an additional heating means for heating the working liquid when the low boiling point fluid entering the first flow-through tank is a liquefied gas. The means for heating is positioned in the first tank.

In a further embodiment of the system with the condenser and heat exchanger, the surroundings of the condenser and the exchanger is a heating vessel containing a liquid to be heated.

In yet another embodiment of the system with the condenser and heat exchanger there is one or more pumps to assist in the circulation of the working liquid and low boiling point fluid.

In one embodiment of the system, the one or more power generating means comprises one or more liquid turbines positioned so that when the working liquid passes through one of the first and second conduits, the liquid also passes through and actuates the turbine. The one or more generator means is in mechanical communication with and actuated by the one or more turbines, when the turbines have been actuated.

In one embodiment of the turbine generator containing system there is further included 1. a collector of energy through which a heat absorbing liquid flows and absorbs energy and 2. a heat exchanger in fluid communication with the collector of energy and through which the heat absorbing liquid flows. The low boiling point fluid is in 177522/2 thermal communication with the heat exchanger absorbing heat brought by the heat absorbing liquid to the heat exchanger. The heated low boiling point fluid then is delivered in its gas phase to an inlet of one of the first and second flow-through tanks.

In yet another embodiment of the turbine-generator system there is included a means for cooling the low boiling point fluid. The means for cooling has a first and second end. The means for cooling is in fluid communication with both of the flow-through tanks at its first end and in fluid communication with the heat exchanger at its second end.

In yet a further embodiment of the turbine generator system, the system further includes a means for cooling the low boiling point fluid. The means for cooling has a first and second end. The means for cooling is in fluid communication with both of the flow-through tanks at its first end. It is also in fluid communication at its second end with an inlet in one of the tanks through which the cooled low boiling point fluid is introduced.

In some embodiments, the system further includes a pump to bring the low boiling point fluid to the inlet of one of the tanks. In yet other embodiments, the system further includes a means for heating the working liquid when the low boiling point fluid is brought to one of the tanks as a liquefied gas. The means for heating is positioned in one or more of the tanks. In other embodiments, there is included a means for heating the working liquid when the low boiling point fluid is brought to one of the tanks as a liquefied gas. The means for heating is a steam generating source in fluid communication with one of the tanks.

Additionally, in another aspect of the present invention there is provided a method for generating power. The method comprises the following steps: providing a working liquid and a low boiling point fluid in a first and second flow-through tank, the first tank being in fluid communication with the second tank; transferring the working liquid from the first tank to the second tank, the transfer flow resulting from bubbles produced by a liquid-to-gas phase transition of the low boiling point fluid in the working liquid; and conveying the working liquid from one of the first and second flow-through tanks to the other tank, wherein during conveyance of the working liquid, the liquid passes through one or more power generating devices. 177522/3 In a further embodiment of the method there is further included the step of collecting heat and transferring the collected heat to the low boiling point fluid to generate the liquid-to-gas phase transition.

In yet another embodiment of the method, the step of collecting heat is effected by one or more solar radiation collectors in fluid communication with the first and second flow-through tanks.

In yet another embodiment of the method of the present invention, the flow-through tanks have a tubular construction and the one or more power generating devices are two power generating devices. These comprise a heat exchanger which removes heat from the working liquid and bubbles therein while transferring heat to its surroundings, and a condenser for liquefying the bubbles, thereby causing them to reform the low boiling point fluid while providing heat to its surroundings.

In another embodiment of the method of the present invention, the power generating device in the step of conveying is comprised of one or more liquid turbines connected to and activating one or more generators for generating power.

In a further embodiment of the method, the method further includes the step of heating the working liquid to a temperature above the boiling point of the low boiling point fluid when the fluid is introduced as a liquefied gas into one of the first and second tanks.

In yet another embodiment of the method, the method further includes the step of cooling the low boiling point fluid prior to introducing the fluid into the first and second tanks as a liquefied gas.

In another embodiment of the method, the method further includes the step of collecting heat and transferring it to the low boiling point fluid prior to its introduction into the first and second tanks so that the fluid is introduced in its gaseous phase. In some instances of this last embodiment, the step of collecting heat is affected by a solar energy collection system.

TERMINOLOGY In what has been described above in the Summary of the Present Invention section and what will be discussed in the Detailed Description of the Preferred Embodiments and the Claims sections below, the terms within each of the following groups have been used interchangeably without intending to distinguish between them. 177522/4 First tank= first flow-through tank 1 or tank 1 or tube 101 Second tank=second flow-through tank 2 or tank 2 or tube 102 First conduit =transfer conduit 19 or conduit 19 or liquid transfer conduit 119 or conduit 1 19 Second conduit= turbine activating conduit 13 or conduit 13 or gas transfer conduit 1 12 or conduit 112.

The numbers shown are the numbers that appear in the drawings below and appear in the description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: Fig. 1 is a schematic view of a system for generating power constructed according to a first embodiment of the present invention; Fig. 2 is a schematic view of a system for generating power constructed according to a second embodiment of the present invention; Fig. 3 is a schematic view of a system for generating power constructed according to a third embodiment of the present invention; and Fig. 4 is a schematic view of a system for heating water constructed according to an embodiment of the present invention.

Similar elements in the Figures are numbered with similar reference numerals. ■ 177522/3 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention provides a system and method for generating power at low temperatures using a hydrothermal source. These temperatures may be varied as required. The system of the present invention is a hydrothermal system which may be used with a solar energy source. The system is based on using a bubble producing fluid to generate bubbles in a tank containing a power generating liquid also described herein as an energy transferring liquid or a working liquid. The bubbles reduce the specific gravity of the liquid in the tank into which the bubble producing fluid is introduced, herein called the first tank or first flow-through tank, causing the power generating liquid, i.e. the working liquid, to flow through a connecting conduit from the first flow-through tank to a second tank, also denoted herein as a second flow-through tank. This flow causes a concomitant flow into the first tank from the second tank along another connecting conduit. The liquid flowing from the second tank to the first tank may also flow through one or more liquid turbines which actuate one or more generators producing power. In addition to operating at lower temperatures then prior art conventional and solar power systems, the system of the present invention uses liquid turbines which are much cheaper, have longer working lives, and require less maintenance than gas turbines. The bubble producing fluid is denoted often herein as a low boiling point fluid, where low boiling point fluid refers to a fluid having a boiling point below the operating temperature of the system. Since the operating temperature of the system may typically be 55°-60°C, the bubble producing fluid, i.e. the low boiling point fluid, must have a boiling point below that temperature range.

Surprisingly, the circulation resulting from the bubbles generates power at an efficiency significantly higher than expected. The efficiency approaches 12-15%. This compares favorably with conventional polluting power stations which have efficiencies of about 22%- 25%o and prior art solar power generating systems which have efficiencies of approximately 11 %-12%.

The systems discussed herein can be adapted and used to provide hot water for private and commercial uses. In such systems, the flow-through tanks are constructed as 177522/3 tubes through which the power generating liquid, i.e. working liquid, may flow. Instead of one or more liquid turbines and one or more generators, the system includes one or more condensers and/or one or more heat exchangers. In these condensers and heat exchangers, the working liquid and the low boiling point fluid are cooled and the bubbles are condensed back to their liquid phase.

Reference is now made to Fig. 1 which shows a system constructed according to a first embodiment of the present invention. The system includes two tanks 1 and 2, typically, but not necessarily, cylindrical tanks typically positioned with their long axis perpendicular to the ground, which contain a working liquid, typically, but not necessarily, water. The system includes a liquid turbine 3. Liquid turbine 3 is in mechanical communication with an electrical generator 7. Tanks 1 and 2, also sometimes referred to herein as "first tank" and "second tank", respectively, are in liquid communication with each other via transfer conduit 19 and turbine actuating conduit 13, herein also sometimes referred to as "second conduit" and "first conduit", respectively. Conduit 13 leads the working liquid from tank 2 to and from turbine 3, emptying it into tank 1. Conduit 19 allows the working liquid to move from tank I to tank 2.

The system also includes at least one solar radiation collector, sometimes a bank of solar radiation collectors 1 1. The solar radiation collectors contain a heat absorbing liquid, typically, but not necessarily, water, which absorbs the radiant energy collected by collectors 11. The heated liquid is brought from collectors 1 1 and circulated through a heat exchanger 4. The heat absorbing liquid is then re-pumped through the collectors by circulation pump 16.

The heat absorbing liquid flowing through collectors 1 1 may be water but may also be oil. These are exemplary liquids only and are not to be considered as limiting the present invention.

When water is the heat absorbing liquid, the heated water obtained from the solar collectors enters heat exchanger 4 at a temperature of typically about 55°C-60°C. However, this temperature should not be deemed to be limiting as it is a function of many factors including the number and nature of the solar collectors. Simple, commercially available solar collectors for household use, such as those manufactured by Amcor Ltd. or Electra Ltd., both Israeli companies, may be used.

In heat exchanger 4, the heat absorbed by the heat absorbing liquid passing 177522/3 through collectors ii is exchanged with a cooled, or even liquefied gas arriving via entrance conduit 15, flowing through heat exchanger 4 and exiting via exit conduit 17. Typically, but without limiting the invention, the cooled or liquefied gas is a gas such as a Freon® gas like Freon® 141 B. If the gas is a liquefied gas when entering, it typically boils and exits the heat exchanger as a gas. The heated gas enters tank 1 via exit conduit 17 at the inlet (not numbered) of flow-through tank 1 and serves as the bubble producing fluid, i.e. the low boiling point fluid.

It should be noted that the term "gas" as used in the discussion herein is used interchangeably with the term "low boiling point fluid". The "gas" may be in its liquid or gaseous state except where specifically noted otherwise in the discussion.

The gas described above is cooled, and possibly even liquefied, by a condenser 5 and further cooled by blower 8 which blows air at ambient temperature on condenser 5. It should be understood that other cooling means can be used in place of blower 8. A water (or other coolant) cooling system may also be used. In such a case, the coolant of the cooling system circulates through condenser 5 but is itself cooled separately in a separate cooling element (not shown).

The cooled or liquefied gas flows from condenser 5 through gas tank 9 and then through a tank in fluid communication with a gas circulation pump 10. Pump 10 forces the cooled or liquefied gas through a one-way valve 20 on its way to entrance conduit 15 and heat exchanger 4. One-way valve 20 prevents heated gases exiting heat exchanger 4 from returning directly to condenser 5.

After exiting heat exchanger 4 and passing through exit conduit 17, the gas is brought to, and enters, flow-through tank 1 , the aforementioned first tank. The entering gas causes strong bubbling in tank 1 and leads to a decrease in the specific gravity of the working liquid in tank 1. The level of the working liquid in tank 1 rises in relation to the level of the working liquid in tank 2, the aforementioned second tank. This causes the working liquid to naturally flow through transfer conduit 19, as noted above, herein also referred to as the first conduit, from tank 1 to tank 2 in the direction of the indicating arrows in an attempt to equalize the liquid levels in the two tanks.

It should be noted that when the gas, i.e. low boiling point fluid, enters tank 1 as a liquid, the working liquid must be at a temperature above the boiling point of the liquefied 177522/3 gas. This condition allows the liquefied gas to change phase inside tank 1 and bubble to the top of the tank as previously described. Therefore, when the gas enters tank 1 as a liquefied gas, heating elements or other heating devices may be required and these are positioned and present in tank 1 and/or 2. These heating devices heat the working liquid to a temperature where it can evaporate and produce bubbles. These heating elements or devices are not shown in Figure 1. Without limiting the invention, these devices may include electrical resistors or solar heated liquids which can exchange heat with the working liquid in tank 1 and/or 2.

When not in operation, the water level in both tanks is the same. This is a necessary consequence of turbine actuating conduit 13, also referred to as the second conduit as mentioned above, connecting both tanks. Because the water in both tanks is at the same level, the pressure at the bottom of each tank is the same and water does not flow from one tank to the other.

The phenomenon of bubbling described above causes a decrease in specific gravity of the working liquid in tank 1. This decreases the pressure at the bottom of tank 1 vis-a-vis the pressure at the bottom of tank 2. Because of this pressure differential at the two ends of conduit 13, there is a steady flow of water from tank 2 to tank 1 through conduit 13 passing through turbine 3. In the Figure, arrows indicate the direction of this flow. This occurs the entire time that there is gas bubbling into tank 1. The flow caused by this pressure differential between the tanks is used to activate liquid turbine 3, typically, but without limiting the invention, a Kaplan turbine, with the activated turbine actuating generator 7, the latter producing electricity. Kaplan turbines may be obtained from many commercial sources, such as Alstom Power — Hydro Systems, Rugby, UK.

Essentially, all the gas bubbles rise to the top of tank 1 above the level of transfer conduit 19. The gas at the top of tank 1 and any residual gas that has entered tank 2, exit the tank system via gas exhaust conduits 18 and 12. The exiting gases are then brought to condenser 5 where cooling of the gas occurs as described above.

In another embodiment of the present invention, shown in Fig. 2 to which reference is now made, that portion of the system showing collectors 1 1 and heat exchanger 4, i.e. the solar energy providing elements, is absent. The remaining portions of the system are identical to that shown in and discussed with Fig. 1. Identical elements 177522/2 of the system are numbered identically. Where the elements operate in a manner similar to that described in conjunction with Fig. 1 , their operation will not be discussed again.

In Fig. 2, the cooled or liquefied gas exiting one-way valve 20 may flow directly through conduit 17 into tank 1 at its inlet. If the gas is just cooled, it enters tank 1 and bubbles to the top of the tank as described previously. If the gas enters as a liquefied gas, i.e. low boiling point fluid, the working liquid in tank 1 is kept at a temperature above the boiling point of the liquefied gas, thereby causing the gas to evaporate. Evaporation generates bubbles which produce the same working liquid flow between flow-through tanks 1 and 2 as discussed above.

When the gas enters tank 1 as a liquefied gas, heating elements or other heating devices are required. These are present in tanks 1 and/or 2 to ensure that the working liquid in the tanks is at a temperature above the boiling point of the low boiling point fluid. These heating elements or other heating devices are not shown in Fig. 2.

While typically the working liquid in tanks 1 and 2 of the present invention will be water, this is not essential. Any working liquid can be used provided that no interaction, chemical or physical, between the low boiling point fluid and working liquid occurs. A typical, but non-limiting alternative working liquid may be alcohol. The density of the working liquid may be heavier or lighter than water. The boiling point of the working liquid typically is greater than that of the low boiling point fluid.

The system described herein may be an "open" or a "closed" system. A closed system as used here indicates a system where the low boiling point fluid is continuously circulating, being condensed, evaporated, and then returned to a condenser. Fig. 1 represents a closed system. What is meant by an open system here is a system where the exiting gas, originating from the low boiling point fluid, is returned to the ambient. An open system requires a constant supply of additional low boiling point fluid.

Fig. 3 to which reference is now made represents yet another embodiment of the present invention. This embodiment employs an open system.

The portion of the system shown in Fig. 1 representing the solar collectors 1 1 , the heat exchanger 4, and the circulation pump 16 are absent. Similarly, the entire cooling system, elements 5, 8, 9 10, 20 and 15 of Fig. 1 are absent. Present is element 32 which 177522/3 represents a steam generator which provides steam via conduit 17 to the inlet (not numbered) of tank 1. Upon entering tank 1 , herein, as noted above, also referred to as the first tank, the steam bubbles to the surface of tank 1 and exits directly to the ambient. Conduits 12 and 18 of Fig. 1 are absent as they are not required in an open system such as Fig. 3. The working liquid circulates as in Fig. 1 through conduits 13 and 19 in the direction indicated by the arrows. Turbine 3 produces power as a result of liquid flowing through conduit 13.

In other embodiments, more than a single liquid turbine may be used with the systems of the present invention shown in Figs. 1-3. When more than a single liquid turbine is used, the turbines may be positioned on the same turbine actuating conduit or each turbine may be positioned on a different turbine actuating conduit.

In yet other embodiments of the present invention more than two tanks may be present in the system.

When a closed system constructed according to the present invention is used, the temperature differential between the low boiling point fluid and the working liquid in tanks 1 and 2 determines the amount of power generated. For a closed system as in Fig. 2, the determining temperature differential is the temperature of the working liquid in tanks 1 and 2 less the temperature of the low boiling point fluid in condenser 5. For the closed system in Fig. 1 , the determining temperature differential is the temperature of the low boiling point fluid as it leaves heat exchanger 4 less the temperature of the low boiling point fluid at condenser 5. For an open system, the temperature differential is essentially irrelevant in determining the amount of power generated.

In general, the larger the temperature differential the greater the flow of the liquid and the greater the electric power generated. The temperature differential that can be used with systems constructed according to the present invention may range between about slightly above 0° to 250°C.

The present invention is not necessarily intended to operate at a single fixed temperature as with other power generating systems. Operating temperatures may be varied. However, the system described herein is typically operated at temperatures much lower than other power generating systems.

In a prototype system using the embodiment shown in Fig. 2, Freon® 141 B was 177522/4 used as the circulating gas, i.e. as the low boiling point fluid, and water as the working liquid in tanks 1 and 2. The water in condenser 5 was kept at a temperature of 20°C and the water (working liquid) in tanks 1 and 2 was kept at a temperature of 60°C. The tanks where heated by resistive heating elements and the temperature controlled by a thermostat. The efficiency of the system was found to be about 15%.

Fig. 4 to which reference is now made, illustrates another embodiment of the present invention. The embodiment in Fig. 4 illustrates a system for generating hot water constructed according to the principles of the present invention. The "flow-through tanks" of previous embodiments are in the present embodiment formed as tubes. The tubes, just as the tanks in previous embodiments, are operative as flow-through conduits for a working liquid.

The system 100 includes two tubes 102 and 101 positioned so as to enter and exit a solar radiation collector 111 , respectively. Tubes 101 and 102, as noted above "first tank" and "second tank", respectively, and collector 1 1 1 contain a working liquid, usually, but not necessarily, water. Tubes 101 and 102 are in liquid communication via working liquid transfer conduit 119 and gas transfer conduit 1 2. Conduits 12 and 119 are herein referred to at times as "second conduit" and "first conduit", respectively. Conduits 112 and 119 lead a gas produced by heating a low boiling point fluid and working liquid, respectively, from tube 101 to tube 102.

As noted above, the system includes a solar radiation collector 11 1. In some embodiments, the solar radiation collector may be a bank of solar radiation collectors. Passing through the solar radiation collector is the working liquid, typically, but not necessarily, water, which absorbs the radiant energy collected by collector 11 1.

While the working liquid flowing through collector 111 may be water it may also be other liquids such as alcohols. These are exemplary liquids only and are not to be construed as limiting the present invention. In general, the boiling point of the working fluid should be greater than the boiling point of the low boiling point fluid.

When water is the heat absorbing, working liquid in tubes 101 and 102, the heated working liquid obtained from the solar collectors enters tube 101 at a temperature of typically about 55°C-60°C. However, this temperature should not be deemed to be limiting as it is a function of many factors including the number and nature of the solar collectors. Simple, commercially available solar collectors for household use, such as those 177522/2 manufactured by Amcor Ltd. or Electra Ltd., both Israeli companies, may be used.

Mixed in with the heat absorbing, working liquid is a low boiling point fluid. Typically, but without limiting the invention, the low boiling point fluid may be selected from the family of Freon® gases, such as Freon® 22 or Freon® 141 B. These gases are easily liquefied. If the low boiling point fluid mixed in with the working liquid is in its liquid phase when entering collector 111 from tube 102, it typically boils and exits the solar collector 1 11 as a gas.

It should be noted that other low boiling point fluids may be used. The choice of fluid is determined by the temperature at which the system is to be operated. The boiling point of the low boiling point fluid must always be such that it is below the operating temperature of the system. As noted above, when the working liquid is water the operating temperature of the solar collectors is typically about 55°C-60°C. However, if the operating temperature of the solar collectors is higher, for example 80°C, either methanol or ethanol could be used as the low boiling point fluid.

The gas produced by the low boiling point fluid described above is cooled, and possibly even liquefied, by a condenser 105 positioned within a heating vessel 142 containing a liquid which is to be heated. This latter liquid is typically, but without being limiting, water. In Fig. 4, the warmed gas is brought via tube 101 to conduit 112 which passes through condenser 105. The cooled or liquefied gas flows from condenser 105 through conduit 112 to tube 102 from whence it is returned and passed through collector 1 1 1 and reheated.

In solar collector 1 1 , the low boiling point fluid is heated and passes into its warmed gaseous state. After exiting collector 1 11 and entering tube 101 , the gas causes strong bubbling in tube 101 which leads to a decrease in the specific gravity of the working liquid in tube 101. As a result, the level of the working liquid in tube 101 rises in relation to the level of the working liquid in tube 102. This causes the working liquid to naturally flow through conduits 1 12 and 119 from tube 101 into tube 102 in an attempt to equalize the liquid levels in the two tubes.

It should be noted that in embodiments where the low boiling point fluid, enters , tube 101 as a liquid, the working liquid must be at a temperature above the boiling point 177522/2 of the low boiling point fluid. This condition allows the liquefied gas to change phase inside tube 101 and bubble to the top of the tube as previously described. Therefore, when the gas enters tube 101 as a liquefied gas, heating elements or other heating devices may be required and these are positioned and present in tube 101 . These heating devices heat the working liquid to a temperature where it can cause a phase change in at least a portion of the low boiling point fluid. These heating elements or devices are not shown in Fig. 4. Without limiting the invention, these devices may include electrical resistors or other solar heated liquids.

The phenomenon of bubbling described above causes a decrease in specific gravity of the working liquid in tube 101 . This decreases the pressure at the bottom of tube 101 vis-a-vis the pressure at the bottom of tube 102. Because of this pressure differential, there is a steady flow of water towards tube 102 from tube 101 via conduits 112 and 19 and from tube 102 through collector 111 towards tube 101. The heated working liquid passes through a heat exchanger 144 after being brought from tube 101 by conduit 119. This allows heat to be transferred to the water to be heated in heating vessel 142. After the working liquid passes through heat exchanger 144 and is cooled, it travels via conduit 119 towards tube 102, ultimately returning to collector 111.

In the Figure, arrows indicate the direction of this flow. This flow occurs the entire time that there is gas bubbling into tube 101 from collector 11 1 as a result of the liquid-togas phase change in the low boiling point fluid. Essentially, all the gas bubbles rise to the top of tube 101 entering conduit 112 positioned above the level of conduit 9.

As noted, there are two heat sources for heating the water in heat vessel 142, heat exchanger 144 and condenser 105. The former is similar to the common heat sources found in many commercial residential solar water heaters. Condenser 05 is an additional heat source with which the water in heating vessel 142 is heated. In addition to transferring heat as a result of the temperature differential between the water entering heat exchanger 144 and the water in heating vessel 142, the gas produced by the low boiling point fluid delivers heat by losing its heat of vaporization to the water in the heating vessel 42. In the case of Freon 22, for example, this is about 55 kcal/kg.

In conventional commercially available solar heating systems, water flows from the 177522/2 collectors to the heating vessel relatively slowly. This is a result of the small temperature differential between the water to be heated in the heating vessel and the water flowing through the collector and the resultant differences in their specific gravities.

In the system of the present invention, there is faster circulatory flow of the heat carrying liquid and therefore the rate of heat transfer to the liquid to be heated is faster than in currently commercially available solar water heating systems. The accelerated flow is a result of the liquid-to-gas phase change of the bubble generating fluid present in the working liquid. The gas generated from the low boiling point fluid bubbles its way through tube 101 towards conduit 119 and heat exchanger 144 and conduit 1 12 and condenser 105. These bubbles accelerate the flow of the heated working liquid increasing the rate of heat transfer between the working liquid and the liquid to be heated in heating vessel 42.

While not shown in Fig. 4, some embodiments of the system presented may also contain one or more pumps to further increase the heated liquid flow rate. While not shown in Fig. 4, in other embodiments of the system, heating vessel 142 may include a sleeve which surrounds heat exchanger 144 and gas condenser 105, conduits 1 12 and 9 and the portion of tubes 102 and 101 adjacent to exchanger 144 and condenser 105. This sleeve, known to those skilled in the art from current commercially available heating vessels, limits the volume of water to be heated at any given time to the volume of water within the sleeve and close to the two heat sources. This allows for more rapid heating.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the invention is defined by the claims that follow.

Claims (30)

177522/3

1. A system for generating power, said system comprising: a working liquid; a low-boiling point fluid flowing through the system with said working liquid; at least two flow-through tanks, including a first tank and a second tank, through which said working liquid and said low boiling point fluid flow; a first conduit and a second conduit for connecting and bringing said first and second flow-through tanks into fluid communication with each other; an energy collector in thermal communication with said working liquid and said low boiling point fluid; and at least one power generating means each of which being in fluid communication with a single one of said first and second conduits, wherein at least a portion of said low boiling point fluid in said first tank absorbs energy from said energy collector and is thereby brought to s-m its gas phase forming bubbles causing said working liquid and said low boiling point fluid to flow from one of said first and second flow-through tanks to the other and then back again, said flow passing through said first and second conduits, and said working liquid while passing through at least one of said first and second conduits transfers energy to said at least one power generating means thereby providing power.

2. A system for generating power according to claim 1 wherein said tanks are formed as tubes and said at least one power generating means are two power generating means, said two power generating means comprised of: a heat exchanger removing heat from said working liquid, low boiling point fluid and bubbles therein wherein heat is transferred to the surroundings of said exchanger; and a condenser for liquefying the bubbles, thereby to cause them to reform said low boiling point fluid while providing heat to the surroundings of said condenser.

3. A system as in claim 2, wherein said energy collector is constructed so that 177522/3 said working liquid and said low boiling point fluid flow through said collector absorbing a portion of the collected energy therefrom, and in which said low boiling point fluid at least partly changes to its gaseous phase forming bubbles within said working liquid.

4. A system as in claim 3 further including an additional heating means for heating said working liquid when the low boiling point fluid which enters said first flow-through tank is a liquefied gas, said means for heating positioned in said first tank.

5. A system as in claim 2 wherein said surroundings of said condenser and said exchanger comprise a heating vessel containing a liquid to be heated.

6. A system as in claim 2 further comprising at least one pump to assist in the circulation of the working liquid and low boiling point fluid.

7. A system as in claim 1 where said at least one power generating means is at least one heat exchanger.

8. A system as in claim 1 where said at least one power generating means is at least one condenser.

9. A system for generating power according to claim 1 , wherein said at least one power generating means comprises: at least one liquid turbine positioned so that when said working liquid passes through one of said first and second conduits, said liquid also passes through and actuates said turbine; and at least one generator in mechanical communication with and actuated by said at least one turbine, when said turbine has been actuated.

10. A system as in claim 9, wherein a heat absorbing liquid flows through said energy collector and absorbs energy therefrom; and said system further includes 177522/3 a heat exchanger in fluid communication with said energy collector and through which said heat absorbing liquid flows, and wherein said low boiling point fluid is in thermal communication with said heat exchanger absorbing heat brought by said heat absorbing liquid to said heat exchanger, said heated low boiling point fluid then being delivered in its gas phase to an inlet of one of said first and second flow-through tanks.

11. 1 1. A system as in claim 10 further including a means for cooling said low boiling point fluid, said means for cooling having a first and second end, said means for cooling in fluid communication with both of said flow-through tanks at said first end and in fluid communication with said heat exchanger at said second end.

12. A system as in claim 9 further including a means for cooling said low boiling point fluid, said means for cooling having a first and second end, said means for cooling in fluid communication with both of said flow-through tanks at said first end and in fluid communication at said second end with an inlet in one of said tanks through which said cooled low boiling point fluid is introduced.

13. A system as in claim 12 wherein said system further includes a pump to bring said low boiling point fluid to said inlet of one of said tanks.

14. A system as in claim 12 further including a means for heating said working liquid when said low boiling point fluid is brought to one of said tanks as a liquefied gas, said means for heating positioned in at least one of said tanks.

15. A system as in claim 12 further including a means for heating said working liquid when said low boiling point fluid is brought to one of said tanks as a liquefied gas, said means for heating being a steam generating source in fluid communication with one of said tanks.

16. A method for generating power, said method comprised of the following steps: 177522/3 providing a working liquid and a low boiling point fluid in a first and second flow-through tank, the first tank being in fluid communication with the second tank; transferring the working liquid from the first tank to the second tank, the transfer flow resulting from bubbles produced by a liquid-to-gas phase transition of the low boiling point fluid in the working liquid; and conveying the working liquid from one of the first and second flow-through tanks to the other tank, wherein during conveyance of the working liquid, the liquid passes through at least one power generating device.

17. A method according to claim 16 further including the step of collecting heat and transferring the collected heat to the low boiling point fluid to generate the liquid to gas phase transition.

18. A method according to claim 17 wherein said step of collecting heat is effected by at least one solar radiation collector in thermal communication with the first and second flow-through tanks.

19. A method for generating power according to claim 17, wherein the flow-through tanks have a tubular construction and the at least one power generating device is two power generating devices comprising: a heat exchanger removing heat from the working liquid and bubbles therein while transferring heat to the surroundings of the exchanger; and a condenser for liquefying the bubbles, thereby to cause them to form low boiling point fluid while providing heat to the surroundings of the condenser.

20. A method for generating power according to claim 17, wherein the flow-through tanks have a tubular construction and the at least one power generating device is at least one heat exchanger removing heat from the working liquid and bubbles therein while transferring heat to the surroundings of the exchanger.

21. A method for generating power according to claim 17, wherein the flow-through tanks have a tubular construction and the at least one power generating device is at least one condenser for liquefying the bubbles, thereby to cause them to form low boiling point fluid while providing heat to the surroundings of the condenser.

22. A method for generating power according to claim 16 wherein the at least one power generating device in said step of conveying is comprised of at least one liquid turbine connected to and activating at least one generator for generating power.

23. A method according to claim 22 further including the step of heating the working liquid to a temperature above the boiling point of the low boiling point fluid when the fluid is introduced as a liquefied gas into one of the first and second tanks.

24. A method according to claim 23 further including the step of cooling the low boiling point fluid prior to introducing the fluid into the first and second tanks as a liquefied gas.

25. A method according to claim 22 further including the step of collecting heat and transferring it to the low boiling point fluid prior to its introduction into the first and second tanks so that the fluid is introduced in its gaseous phase.

26. A method according to claim 25 wherein said step of collecting heat is affected by a solar energy collection system.

27. The system according to any of claims 1-15, and substantially as shown and described hereinabove in conjunction with any of Figs. 1-4.

28. The system according to any of claims 1-15, and substantially as shown in any of Figs. 1-4.

29. The method according to any of claims 16-26, and substantially as shown and described hereinabove in conjunction with any of Figs. 1-4. 177522/1

30. The method according to any of claims 16-26, and substantially as shown Figs. 1-4. For the Applicant, Jeremy M. Ben-David & Co. Ltd. YADK 617/1 .1