Expansion engine for converting thermal energy into mechanical energy and method for converting thermal energy into mechanical energy using said engine

Abstract

The present invention discloses an expansion engine that, by means of a cycle similar to the Carnot cycle, converts thermal energy in general, and solar energy in particular, so as to transform the heat from a hot source and a cold source into mechanical work and subsequently into electrical energy. There is no economically viable means in the prior art for converting heat resulting from small temperature differences into work. This applies both to systems based on the Rankine cycle and to those based on the Stirling cycle. The present invention generates useful energy from an inexhaustible source such as the sun, using an abundant resource such as water, in a closed circuit. When applied to the utilization of solar energy, the expansion engine has the notable advantage of using virtually the entire spectrum of solar radiation, from infrared and visible light to ultraviolet, and not just a fraction of the visible spectrum, as is the case with photovoltaic panels. The invention is aimed at the production of energy from vast heat sources resulting from small temperature differences, such as those available in geothermal sources, from the temperature difference between surface water and deep-sea water, or from water heated by solar thermal radiation. The present invention enables the production of energy at the required locations and in the required amounts, thereby eliminating the need for electrical distribution networks. The present invention encompasses a system for storing large amounts of energy.

Description

"EXPANSION ENGINE FOR CONVERTING THERMAL ENERGY INTO MECHANICAL ENERGY AND METHOD FOR CONVERTING THERMAL ENERGY INTO MECHANICAL ENERGY USING SAID ENGINE" FIELD OF THE INVENTION

[0001] The present invention belongs to the technological sector of energy generation from thermal sources, and refers to an expansion engine that uses new means to transform thermal energy in general, and solar energy in particular, into mechanical and electrical energy from a closed circuit of hot water to act as a high-temperature heat source and a closed circuit of cold water to act as a low-temperature heat source.

[0002] Furthermore, the present invention relates to a system and method for generating energy using said motor. FUNDAMENTALS OF THE INVENTION

[0003] Traditionally, the techniques available for converting heat into work or electricity involve the use of machines such as steam turbines; Stirling engines; Rankine organic cycle turbines; and / or Peltier-Seebeck effect plates.

[0004] However, steam engines and turbines require high temperatures (>100°C) and are therefore not suitable for all types of applications, as they depend on the temperature difference between the hot and cold heat sources. Additionally, Stirling engines heat and cool air through the respective hot and cold walls of the same container. Let the wall temperatures be specified by T. a , the highest temperature, and T b , the lowest temperature. Heat transmission The movement of air from the walls to the air occurs through two processes: radiation and conduction. Radiation <p r It is governed by Stefan-Boltzmann law. r= cr. (Ta - T&), where o is the Boltzmann constant. The conduction (p c , on the other hand, is proportional to the temperature difference: (p c = C. (T a - T b , where C is a constant that depends on the materials involved. It follows from these two formulas that radiation prevails at high temperatures: the <p r = 4cr. < T > 3 . AT,

[0005] whereas driving is prevalent in low temperatures: (p c = C. T

[0006] Therefore, to operate at low temperatures, a Stirling engine would rely on thermal conduction. However, air is a poor conductor of heat. This problem will be greater the larger the dimensions of the Stirling engine. It follows that large Stirling engines are not suitable for operating at low temperatures.

[0007] Furthermore, Rankine organic cycle turbines present a promising technology but still face some challenges to their wider acceptance. The organic fluids used, such as hydrocarbons, refrigerants, or siloxanes, are often very expensive, toxic, or aggressive to the turbines themselves and the environment. The interaction between the organic fluids and other components must be carefully considered to avoid corrosion, degradation, and other problems. Problems that can compromise the safety and economic potential of the system, increasing operating costs and making the installation of these systems unfeasible in various types of power generation plants.

[0008] Peltier-Seebeck effect plates exhibit low efficiency, high cost, require a large temperature difference, and present thermal management challenges, in addition to significant difficulty in adequately insulating the plate's ends. This limits their viability for large-scale energy production.

[0009] These technical limitations are opening up space for innovations in the area of ​​energy generation, which are proving to be more versatile, safe, and adapted to modern demands for practicality and sustainability. In this sense, some solutions and technologies have already been developed using these principles:

[0010] Document US2010218741 discloses a heat engine comprising a cylinder and a piston and an insulated heat battery including at least one thermal mass, such as the engine block itself, for storing and retaining heat in order to increase or cause the expansion of the fluid within the cylinder and actuate the piston, wherein the heat battery further comprises an electrolytic chamber containing a thermal electrolyte to function as a thermal electric battery, and the heat is stored in the heat battery, for example, by activating heating elements by electrical resistance in the heat battery; such that the stored heat causes the expansion of a non-combustible expanding fluid, such as water, or increases the expansion of a combustible expanding fluid, such as gasoline.

[0011] Furthermore, document W02008064418 discloses a method for operating a non-combustion piston engine comprising a cylinder with an upper and lower chamber separated by a partition including an opening with a valve, a first means of supplying air to at least one of the chambers; and a second means of supplying at least water vapor and hydrogen to the lower chamber, the method comprising supplying air to at least one of the chambers; compressing the air into the upper chamber and closing the valve to temporarily store the heated air; supplying at least water vapor and hydrogen to the lower chamber; and opening the valve when the lower chamber is at a minimum volume where the heated air is released into the lower chamber, causing the water vapor and / or hydrogen to expand and force the piston out of the cylinder.

[0012] As can be observed, state-of-the-art thermal energy conversion systems operate under high thermal gradients in order to maximize their thermodynamic efficiency. However, a high thermal gradient also causes an inevitable increase in heat loss and a consequent decrease in overall efficiency.

[0013] Another problem for the efficient conversion of thermal energy into work relates to energy storage. This issue is an essential part of the operation of power plants, given that production according to demand is a requirement for the convenient operation of a power plant. At the same time, it is also necessary to cope with variations in the primary availability of energy. Thus, an effective system and Economic considerations for energy storage should be an integral part of the design of a power generation unit, and particularly of a solar power plant, due to the intermittent nature of its basic energy source.

[0014] Furthermore, few proposed solar energy systems directly integrate energy storage into the generator design. In practice, in many state-of-the-art solar energy projects, energy generated during periods of higher insolation is often stored in electric batteries so that this energy can be used during periods of higher consumption. However, the costs, environmental impacts, and limited storage capacity of currently available batteries have hindered the wider and more economical use of photovoltaic solar energy.

[0015] Furthermore, in these systems, heat is stored and transferred to the energy conversion device. The undeniable fact is that heat loss will always be greater the larger the temperature gradient involved. For example, available solar energy storage and conversion systems based on high-temperature molten sodium are, by their very nature, inefficient from the point of view of conserving stored heat. In addition, the materials currently available for manufacturing these heat exchangers must be resistant to the strong corrosion of molten sodium and are therefore very expensive and severely limit operating conditions. It is therefore clear that new, efficient methods and installations for heat storage and transfer are fundamental requirements for economically viable power plants, and this is particularly true. For solar power plants. Molten sodium-based solar power plants aim to exploit more efficient regimes through operation at higher temperatures. However, to achieve this, it is necessary to overcome many limitations related to costs and the thermal and mechanical resistance of the materials used. Furthermore, all components of these plants are subject to significant physical degradation as a result of high and repetitive thermal shocks. In fact, maintenance and component replacement represent a large part of the total cost of a molten sodium-based solar energy system. Thermal stress results in a short lifespan for these elements due to their use under varying temperatures and subjection to large thermal gradients.

[0016] Therefore, there is currently no device capable of converting a large amount of heat from small temperature differences into useful energy.

[0017] To solve these problems, the present invention conceives an expansion engine based on a cycle that approximates the Carnot cycle, for the transformation of collected heat into mechanical work and subsequently into electrical energy from heat sources originating from small temperature differences. The small temperature difference in which energy production occurs can originate from geothermal heat sources, or from the temperature difference between surface and seabed water, or from water heated by solar thermal radiation. In any of these cases, the present invention proposes to extract useful energy from a large amount of heat originating, however, from a small temperature difference between the hot and cold heat sources.

[0018] Furthermore, in the energy storage and conversion system presented here, the heated water tanks can be sized to be large enough to store energy for many consecutive days without any sunshine. The combination of the tanks' large mass with the high specific heat of water allows for maximizing the thermodynamic utilization of the solar energy source. On the other hand, the relatively low temperature differences and the large volume of water involved drastically minimize heat losses by conduction. In short, the large heat storage capacity allows a system using the present invention to operate continuously and under conditions suitable to the demand and availability of the energy source.

[0019] Therefore, there is no solution in the state of the art equivalent to that presented here in the present invention that combines technical differentiators, economic advantages, and reliability and safety. OBJECTIVES OF THE INVENTION

[0020] Thus, it is an objective of the present invention to provide a solution to the challenges and limitations listed above, by presenting an expansion engine for the production of energy from heat from geothermal sources, or from the temperature difference between surface and seabed water, or from water heated by solar thermal radiation.

[0021] It is also an objective of the present invention to provide an expansion engine based on a cycle that approximates the Carnot cycle, for the transformation of collected heat into mechanical work. and subsequently in electrical energy.

[0022] Another objective of the present invention is to provide an optimized method for heat exchange between a liquid medium such as water and a gaseous medium such as air.

[0023] It is also an objective of the present invention to provide an efficient system that utilizes existing heat sources in nature without harming the environment. SUMMARY OF THE INVENTION

[0024] The present invention achieves these and other objectives by means of an expansion engine comprising:

[0025] a heat exchanger comprising a piston that delimits the height of said heat exchanger; said exchanger being thermally insulated on its external part and connected to two air inlets, each controlled by an atmospheric air intake valve;

[0026] - a hot water spray valve configured to inject hot water into the heat exchanger, forming a hot water inlet at the bottom of one side of said heat exchanger;

[0027] - a cold water spray valve configured to inject cold water into the heat exchanger, forming a cold water inlet at the bottom on the opposite side of said heat exchanger;

[0028] - A hot receptacle is placed at the base of the heat exchanger to collect the hot water sprayed in each cycle of the expansion engine;

[0029] A cold receptacle is placed at the base of the heat exchanger to collect the cold water sprayed in each engine cycle. the expansion;

[0030] - wherein the hot receptacle is arranged to receive hot water sprayed by a hot water spray valve and connected to a hot air and water exhaust valve and a hot separator, wherein said hot separator is connected by pipes to a first hot air outlet configured to conduct the discarded air to the atmosphere; and further connected to a heated fluid feedback circuit; and

[0031] - wherein the cold receptacle is arranged to receive cold water sprayed by a cold water spray valve and connected to a cold air and water exhaust valve and a cold separator, wherein said cold separator is connected by pipes to a second cold air outlet configured to conduct the discarded air to the atmosphere; and further connected to a cooled fluid feedback circuit; and

[0032] Furthermore, in another aspect, the present invention achieves these and other objectives by means of a method of converting thermal energy into mechanical energy, using said expansion engine which comprises:

[0033] - a pre-cycle stage, in which the atmospheric air intake valves are kept open to allow air to enter until the entire volume of the heat exchanger is filled and the piston remains expanded, while the hot air and water exhaust valve and the cold air and water exhaust valve are kept closed, and the expansion movement of the piston causes atmospheric air to be drawn into the heat exchanger;

[0034] - a first stage, that of isothermal compression at low temperature, in which a spray cam, installed in a valve control disc, acts to open the valve of Cold water spray; and, either by the action of a starter motor or by human action during starting, or by the continuous movement of an inertia disc, the piston compresses the air contained inside the heat exchanger and, at the same time, cold water is injected through the base of the heat exchanger via the cold water spray valve, in order to maintain the temperature of the compressed air constant throughout the stage, the air temperature being T1 = Tb, where T1 is slightly above a temperature (Tf). b ) from the cold storage tank and the cold water is collected by the cold receptacle at the base of said heat exchanger;

[0035] - a second stage, adiabatic compression, in which the contents of the heat exchanger are isolated from the outside world by closing all the valves, and after the injection of cold water ceases, either by the action of a starter motor or by human action during starting, or by the continuous movement of the inertia disc, the piston continues compressing the air contained inside the heat exchanger, with all the valves kept closed, until the air temperature reaches a temperature T3 = Ta, where T3 is slightly below a temperature (7 a ) from the hot storage tank;

[0036] - a third stage, that of isothermal expansion at high temperature, in which the spray cam acts to open the hot water spray valve and keeps the other valves closed, so that the air contained inside the heat exchanger expands and pulls the piston inside the heat exchanger while being heated by thermal contact with the hot water sprayed by the hot water spray valve, maintaining a constant temperature T4=T3=Ta, and the water being Hot water is collected in the hot receptacle at the base of the heat exchanger;

[0037] - a fourth stage, the adiabatic expansion stage, in which all valves are kept closed, in order to isolate the contents of the heat exchanger from the rest of the system until the temperature returns to the value of the first stage T1 = Tb, so that the air expands and pushes the piston inside the heat exchanger; and

[0038] - a post-cycle stage, in which isobaric exhaust of air, hot water and cold water occurs, where a suction and exhaust cam, installed on the valve control disc, acts to open the atmospheric air intake valve, the hot air and water exhaust valve, and the cold air and water exhaust valve, resulting in air exhaust to the atmosphere, and the hot water spray valve and cold water spray valve are closed, and the hot water that was in the hot receptacle inside the heat exchanger is directed, along with some air, to the hot separator and the air is released to the atmosphere through the hot air outlet and the hot water returns to the heated fluid feedback circuit, and finally to the hot storage tank;The cold water that was in the cold receptacle inside the heat exchanger is directed, along with some air, to the cold separator where the air is released to the atmosphere through the cold air outlet and the cold water returns to the chilled fluid feedback loop, and finally to the cold storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be described based on the attached drawings, which illustrate: Figure 1 represents the schematic of the expansion engine in a preferred embodiment. Figure 2 depicts the behavior of the expansion engine system before and after an isobaric atmospheric air intake stage, in a preferred embodiment of the present invention. Figure 3 depicts the behavior of the expansion engine system before and after a low-temperature isothermal compression stage, in a preferred embodiment of the present invention. Figure 4 depicts the behavior of the expansion engine system, before and after an adiabatic compression stage, in a preferred embodiment of the present invention. Figure 5 depicts the behavior of the expansion engine system before and after a high-temperature isothermal expansion step, in a preferred embodiment of the present invention. Figure 6 depicts the behavior of the expansion engine system, before and after an adiabatic expansion step, in a preferred embodiment of the present invention. Figure 7 depicts the behavior of the expansion engine system before and after an isobaric exhaust stage of the air, hot water, and cold water used in the cycle, in a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention relates to an expansion engine based on a cycle that approximates the Carnot cycle, for the The transformation of collected heat into mechanical work and subsequently into electrical energy. The present invention utilizes an innovative construction comprising a system that aims to exploit vast heat sources arising from small temperature differences between hot and cold heat sources, such as those available in geothermal sources, or from the temperature difference between surface and seabed water, or water heated by solar thermal radiation, thus being able to extract useful energy from a large amount of heat arising from a small temperature difference between hot and cold heat sources.

[0041] Conventional piston engines operate through explosions derived from fossil fuels, whereas the present expansion engine uses the compression and expansion of air, making use of a large amount of thermal energy from a small temperature difference between the cold and hot sources.

[0042] The expansion engine revealed here operates according to the quasi-Carnot cycle shown below. A single quasi-Carnot cycle of the expansion engine encompasses a Carnot cycle and an intake and exhaust cycle. Consequently, the expansion engine requires a camshaft connected to the flywheel through a 2:1 ratio, meaning that two revolutions of the flywheel correspond to a single revolution of the camshaft. This operation can be achieved by means of two gears that maintain this 2:1 ratio in their diameters and that can be connected directly, or through a toothed belt, for example. This same strategy is Commonly used in 4-stroke internal combustion engines, both diesel and gasoline. For the sake of clarity, we illustrate in Figures 2 to 7 below the various valve opening and closing controls and cams through a wired connection of these controls, which are powered by electrical sources. Naturally, these same controls can also be executed through mechanical transmissions involving shafts, rods and cams without affecting the innovation criteria of the present invention.

[0043] The present invention offers numerous technical and economic advantages when compared to the state of the art, some of which are listed below: • The present invention eliminates dependence on extensive electrical distribution networks because it allows for uninterrupted energy production, according to demand, and in the required locations. • The present invention features the use of water at relatively low temperatures, increasing the safety of energy conversion plants. • The present invention utilizes a renewable and efficient energy source when compared to other methods of energy production. • The present invention describes an efficient and economical system for storing large quantities of energy as an integral part of the design of a power generation unit.

[0044] With reference to Figure 1, an expansion engine (1) comprises a heat exchanger (8) housing a piston (11) that delimits the height of the heat exchanger (8). According to a preferred embodiment of the present invention, the heat exchanger (8) is thermally insulated on its outer part. Similarly, a hot storage tank (3) is also thermally insulated. In both cases, the use of glass wool as a lining material is preferred.

[0045] The expansion engine (1) further comprises a hot water spray valve (26) located at the bottom left side of said heat exchanger (8) and a cold water spray valve (27) located at the bottom right side of said heat exchanger (8). The hot water spray valve (26) is configured to inject hot water into the heat exchanger (8) and the cold water spray valve (27) is configured to inject cold water into the heat exchanger (8).

[0046] The expansion engine (1) further comprises a hot receptacle (16) disposed on the right side at the base of the heat exchanger (8) in order to collect the hot water sprayed in each cycle of the expansion engine (1) and a cold receptacle (17) is disposed on the left side at the base of the heat exchanger (8) in order to collect the cold water sprayed in each cycle of the expansion engine (1).

[0047] According to the preferred embodiment of the present invention, the hot receptacle (16) communicates via ducts to an air and hot water exhaust valve (28) and a non-return valve (31) connected to a hot separator (15) which in turn communicates with a heater (4) and a hot storage tank (3). Additionally, the cold receptacle (17) communicates via ducts to an air and cold water exhaust valve (29) and a non-return valve (31) connected to a cold separator (18) which in turn communicates with a heat radiator (10) and a cold storage tank (12).

[0048] Furthermore, according to the present invention, the hot water spray valve (26) contains a plurality of orifices through which hot water is sprayed from the base of the heat exchanger (8), on the left side, in the form of jets. The jets have a relatively small diameter and flow in the form of a shower, transferring the temperature of the hot water to the air contained inside the heat exchanger (8).

[0049] Similarly, the cold water spray valve (27) contains a plurality of orifices through which cold water is sprayed from the base of the heat exchanger (8), on the right side, in the form of jets. The jets have a relatively small diameter and flow in the form of a shower, transferring the temperature of the cold water to the air contained inside the heat exchanger (8).

[0050] With reference to Figures 2-7, a first inlet to the heat exchanger (8) is associated with two air inlets (2), each controlled by an atmospheric air inlet valve (25). A second inlet to the heat exchanger (8) is connected to the hot water spray valve (26) for adding heat to the interior of the heat exchanger (8).

[0051] Furthermore, a first outlet of the heat exchanger (8) is associated with an air and hot water exhaust valve (28) to a hot separator (15), said hot separator (15) being connected by pipes to a hot air outlet (7) configured to conduct the discarded air to the atmosphere; and also connected to a heated fluid feedback circuit (9) formed by the tank of hot storage (3) and the heater (4), so that the water remaining in the hot separator (15) is routed and kept heated for subsequent return to the heat exchanger (8) via the hot water spray valve (26), closing the heated fluid feedback loop (9).

[0052] A third inlet to the heat exchanger (8) is connected to said cold water spray valve (27) for cooling the heat exchanger (8), and a second outlet of the heat exchanger (8) is connected to the cold air and water exhaust valve (29) for the cold separator (18), said cold separator (18) being connected to a cold air outlet (30) configured to conduct the discarded air to the atmosphere; and further connected to a cooled fluid feedback circuit (19) formed by the cold storage tank (12) and the heat radiator (10), so that the water remaining in the cold separator (18) is routed and kept cooled for subsequent return to the heat exchanger (8) by means of the cold water spray valve (27), closing the cooled fluid feedback circuit (19).

[0053] In a preferred embodiment, the heater (4) of the heated fluid feedback circuit (9) may be a solar collector positioned to optimize its direct exposure to sunlight, wherein a heat storage fluid, which in a preferred version of the invention may be water, is circulated by means of a pump (not shown), or spontaneously by means of a thermal siphon, between the solar collector and the hot storage tank (3), wherein inside the solar collector is disposed a radiation receiver consisting of a plurality of tubes for the transfer of heat collected in the solar collector to the heat storage fluid, which It can be water. The heat storage fluid, after being heated inside the heater (4), which can be a solar collector, is carried by pumping or by thermal siphon to the hot storage tank (3) in order to transfer the heat collected in the solar collector to the cooled fluid feedback circuit (19).

[0054] As the heat storage fluid passes through the heater's radiation receiver (4), solar radiation heats the heat storage fluid to a temperature where the fluid remains liquid. The heated liquid is then transferred via a heated liquid circulation line (5) to the hot storage tank (3). The hot storage tank (3) is thermally insulated to minimize heat loss by radiation and conduction through its walls. The heated liquid is circulated through the heated liquid transfer line (5) by means of a thermal siphon between the solar collector and the hot storage tank (3). The heated liquid is conducted, at an appropriate rate and according to the power plant's energy production needs, to the heat exchanger (8).This conduction of the heated liquid is carried out through a hot feed pipe (6) and through the hot water spray valve (26) of the hot storage tank (3).

[0055] It is important to highlight that a mass of water heated to approximately 60°C above ambient temperature contains a considerable amount of thermal energy. This is due to the fact that water has, among all available substances, the highest specific heat of 4.18 kJ / (°CL). Regarding the cooled fluid feedback circuit (19), the heat radiator (10) is preferably positioned to promote contact thermal between the cold storage tank (12) and the environment, wherein a heat storage fluid, which in a preferred version of the invention may be water, after being cooled in the heat radiator (10), is made to circulate by means of a pump, or spontaneously by means of a thermal siphon, between the heat radiator (10) and a cold storage tank (12).

[0056] In this example, as the cold fluid passes through the heat radiator (10), its temperature decreases and the cooled liquid is transferred by a cold liquid circulation line (13) to the cold storage tank (12). The cold storage tank (12) is maintained in close thermal contact with the environment in order to maximize heat diffusion by radiation and conduction through its surfaces. The cooled liquid is circulated at an appropriate rate and as needed through a cold liquid circulation line (13) by means of a pump or thermal siphon between the heat radiator (10) and the cold storage tank (12).

[0057] The cooled liquid is conveyed, at a suitable rate and according to the energy production needs of the plant, through a cold feed pipe (14) between the cold storage tank (12) and the heat exchanger (8).

[0058] Thus, the construction of the heat exchanger (8) allows that, once the air is heated by the spraying of heated water, the consequent increase in its pressure is used to propel the piston (11) and thus actuate an inertia disc (22). Similarly, once the air is cooled by the spraying of cold water, the consequent decrease in its pressure is used to retract the piston (11) and thus continue the actuation of the disc. of inertia (22). According to the method presented here, heated water and cold water are alternately sprayed in a controlled manner onto the air contained within the heat exchanger (8) which, as a result, heats up and expands, and cools down and contracts.

[0059] Furthermore, the entire system is preferably configured so that the water and air come into intimate thermal contact with each other inside the heat exchanger (8). Thus, the inlets and outlets are arranged in the chamber so that the air and water can prolong the heat exchange as they flow from their inlets to their respective outlets. Thus, the present invention provides a heat exchange system that aims at use in an assembly that combines energy storage and conversion.

[0060] The heat exchanger (8) has the function of carrying out heat transfer between water and air. Pumps are provided to conduct and collect both water and air to and from the heat transfer chamber. The heat exchanger (8) includes means to transfer the temperature of the water to the air. In this way, heat communication is carried out in the heat exchanger (8) between the water and the air. The hot storage tank (3) for storing heated water supplies both the heater (4) and the expansion engine (1), and a cold storage tank (12) for storing cold water supplies both a heat radiator (10) and the expansion engine (1).

[0061] Furthermore, the expansion engine (1) comprises a spray cam (23), installed in a valve control disc (33), which allows switching on and off both the hot water spray and the cold water spray at the respective appropriate times; as well as a suction and exhaust cam (24), installed in the disc of valve control (33), which allows switching on and off at the respective times determined, both the intake of new air, as well as the exhaust of air, cold water and hot water.

[0062] The cams or lobes, installed on the camshaft disc (33), of the expansion engine (1), are responsible for opening and closing the intake, injection and exhaust valves, allowing the entry of new air, hot water or cold water and the exhaust of the air and water mixture at predetermined times.

[0063] The shape and arrangement of the cams are designed to ensure the correct timing of valve operations as the valve control disc (33) rotates.

[0064] In the energy conversion system described here, the minimum size of the hot storage tank (3) would be that required to maintain a sufficient quantity of heated water for energy production for several days. Preferably, the system should store the largest mass of water that is practical and possible.

[0065] The hot storage tank (3) is constructed taking into account its physical and chemical stability in contact with water. Much relevant information for the design and construction of such containers is available in the literature on tank industry technology. Additionally, the walls of the hot storage tank (3) can be constructed of a plurality of layers of insulating and heat-resistant materials, being an efficient means of storing thermal energy.

[0066] Additionally, the possibility is foreseen of water being replaced by another liquid medium suitable for the exchange of Heat in the system described by the present invention. Water is most advantageous because, among all available substances, it has by far the highest specific heat (4.18 Joules / °C.gr). It is also worth noting that water is much more readily available than any of the other substances that could be used for energy storage. The solar collector, commonly found in the state of the art, can heat water to a temperature slightly below 100°C or 373°K. This heated water can be stored in suitably thermally insulated tanks, allowing its use according to the needs of a solar power plant constructed in accordance with the present invention. The air heated by the hot water undergoes expansion, while the air cooled by the cold water undergoes contraction.These volume changes are used to drive the piston (11) inside the heat exchanger (8) in order to drive the inertia disc (22) and an electric generator (21).

[0067] The temperature of the hot water from the hot storage tank (3) is transmitted to the air inside the heat exchanger (8). As jets of hot water pass through the interior of the heat exchanger (8), the hot water transmits its temperature to the air. The hot water from the jets released by the hot water spray valve (26) is collected in the hot receptacle (16) positioned at the base of the heat exchanger (8).

[0068] The temperature of the cold water from the cold storage tank (12) is transmitted to the air inside the heat exchanger (8). As jets of cold water pass through the interior of the heat exchanger (8), the cold water transmits its temperature to the air. The cold water from the jets is released by the cold water spray valve. (27) is collected in the cold receptacle (17) positioned at the base of the heat exchanger (8).

[0069] In this way, the air is constantly expanded and compressed, so that mechanical energy is extracted, in this embodiment, by means of the piston (11) which drives the inertia disc (22), which, in turn, drives an electric generator (21) in order to produce electrical energy.

[0070] The walls of the heat exchanger (8) of the expansion engine may have the inner surface coated with a hydrophobic polymer material, such as a fluorocarbon, in order to restrict water retention by capillarity. This structure may be produced with a casing of thermally insulating material such as a plastic or a composite material and also with external coatings, also thermally insulating. The heat exchanger (8) of the engine itself is constructed with insulating materials similar to that of the hot storage tank (3) lining.

[0071] The efficiency with which energy conversion and storage occur is favorably reflected in the total cost of the solar energy conversion system. According to what has been presented here, more useful energy can be obtained by simply adding more solar collectors, which are particularly inexpensive. Furthermore, the low thermodynamic efficiency of the expansion engine proposed here (~16%), a consequence of the small temperature difference between the hot source (~80°C) and the cold source (~25°C), is still sufficiently high to offer itself as an advantageous option compared to the alternatives available today. Finally, the fact that the spraying of hot and cold fluid is always carried out inside the... heat exchanger (8), maximizes the thermal conduction potential between the heat exchange media and minimizes energy losses.

[0072] The said expansion engine (1) is the central component of the energy storage and conversion system presented here, where jets of hot and cold water are alternately sprayed through the hot water spray valve (26) and the cold water spray valve (27) inside the heat exchanger (8). System Operation

[0073] According to the method presented here, heated water and cold water from the system are sprayed alternately onto the air contained within the heat exchanger (8), which, as a result, heats up and cools down, leading to an expansion and compression of the air in the heat exchanger (8), in order to move the piston (11) delimiting the heat exchanger (8) in a desired and controlled manner. The operation of this system is achieved by the controlled opening and closing of the system valves (25, 26, 27, 28, 29). Although there is a very high number of possible combinations of valve openings (25, 26, 27, 28, 29), the system and method of operation of the present invention provides for a finite and reduced number of system steps, each of which steps is defined by which valves (25, 26, 27, 28, 29) are open and closed, enabling or preventing the communication of the engine components to the expansion (1) in predetermined ways.

[0074] In a pre-cycle stage, as illustrated in Fig. 2, the atmospheric air intake valves (25) are held open to allow air intake until the entire volume of the heat exchanger is filled. heat (8) and keep the piston (11) expanded, with the hot air and water exhaust valve (28) and the cold air and water exhaust valve (29) kept closed, and the expansion movement of the piston (11) causes atmospheric air to be drawn into the heat exchanger (8) in order to allow the cycle to begin.

[0075] In a first stage of low-temperature isothermal compression, as illustrated in Fig. 3, the spray cam (23) acts to open the cold water spray valve (27), which makes it possible to compress the air without a temperature increase. During this stage, the intake valves (25) are closed and isothermal compression begins. In this stage, either by the action of a starter motor or by human action during starting, or by the continuous movement of the inertia disc (22), the piston (11) compresses the air contained inside the heat exchanger (8), and at this moment, all the outlets of the heat exchanger (8) are closed.At the same time, cold water is injected through the base of the heat exchanger (8) via the cold water spray valve (27) in the form of a plurality of jets launched upwards, but which, due to gravity, fall and reach a cold receptacle (17) of the heat exchanger (8), maintaining the temperature of the compressed air constant throughout the process since the air contained inside the heat exchanger (8) is cooled by thermal contact with the sprayed cold water. The cold water is injected through the cold water spray valve (27) in the quantity necessary to maintain the air temperature T1 = Tb constant, close to and slightly above the temperature. from the cold storage tank (12) and the cold water is collected in cold receptacle (17) at the base of the heat exchanger (8). At this stage, work is done on the motor.

[0076] For example, the temperature in the isothermal compression stage can be T1 = Tb = 303°K = 30°C and the temperature of the cold water in the cold storage tank (12) of ( T^)= 293°K = 25°C.

[0077] In a second stage, corresponding to adiabatic compression, as illustrated in Fig. 4, the contents of the heat exchanger (8) are isolated from the outside world by closing all the valves (25, 26, 27, 28, 29). This compression aims to raise the air temperature to a value close to the temperature of the hot source. In this stage, the expansion engine requires an amount of mechanical work that is proportional to the difference between the initial temperature Tb and the final temperature Ta of the air. In relation to the previous stage, the cold water injection is off and, either by the action of a starter motor or by human action during starting, or by the movement of the inertia disc (22), in continuous operation, the piston (11) continues to compress the air contained inside the heat exchanger (8), with all outlets closed, until the air temperature T3 = Ta approaches a value slightly below the temperature ( Tf a) from the hot storage tank (3). In this situation the air volume reaches its lowest value. At this stage, work is done on the engine.

[0078] For example, the final temperature of the adiabatic compression stage can be T3 = Ta = 343K = 70°C and the temperature of the hot water in the hot storage tank (3) of (T fa ) =353°K = 80°C.

[0079] In a third stage corresponding to isothermal expansion at high temperature, as illustrated in Fig. 5, it is possible to... Note that only the spray cam (23) acts to open the hot water spray valve (26) in order to maintain a constant air temperature through the spraying of hot water, originating from the hot storage tank (3), injected into the heat exchanger (8) by the hot water spray valve (26) in the form of a plurality of jets launched upwards, but which, due to the action of gravity, decay and reach the hot receptacle (16) of the heat exchanger (8). The air contained inside the heat exchanger (8) is heated by thermal contact with the sprayed hot water, expands and pulls the piston (11) inside the heat exchanger (8) with all outlets closed. Hot water is injected by the hot water spray valve (26) in the quantity necessary to maintain a constant air temperature T3=T4=Ta close to and slightly below the temperature (Tfa) of the hot storage tank (3).Hot water is collected in the hot receptacle (16) at the base of the heat exchanger (8). At this stage, work is performed by the motor.

[0080] Preferably, it is desirable that the temperature during the isothermal expansion be maintained at Ta = 343°K = 70°C and the temperature in the hot storage tank (3) be ( Ty a ) = 80°C.

[0081] In a fourth stage corresponding to adiabatic expansion, as illustrated in Fig. 6, all valves are closed again, in order to isolate the contents of the heat exchanger (8) from the rest of the system. This expansion is necessary to lower the air temperature to a value close to the temperature of the cold source. In this stage, the expansion engine performs an amount of mechanical work proportional to the difference between the initial temperature Ta and the final temperature Tb of the air. The work gain in this expansion stage adiabatic is equal to the labor cost for performing the previously analyzed adiabatic compression step. The valves remain closed until the temperature returns to the initial value Tb. The air expands and pushes the piston (11) inside the heat exchanger (8) until the air temperature T1 = Tb approaches and is slightly above the temperature (7} fc ) from the cold storage tank (12). In this situation, the air volume reaches its highest value. Also in this stage, work is performed by the engine.

[0082] In a post-cycle stage, as illustrated in Fig. 7, isobaric exhaust of the air, hot water and cold water used in the recently executed cycle occurs, whereby the suction and exhaust cam (24) acts to open the atmospheric air intake valve (25), the hot air and water exhaust valve (28), and the cold air and water exhaust valve (29).Finally, the Quasi-Carnot cycle is completed with the triple exhaust of air to the atmosphere, of hot water back to the heated fluid feedback loop (9) and of cold water to the cooled fluid feedback loop (19), where the hot water spray valve (26) and cold water spray valve (27) are closed and the air exhaust and the hot water and air exhaust valve (28) and the cold water and air exhaust valve (29) are opened and the hot water that was in the hot receptacle (16) inside the heat exchanger (8) is routed, along with some air, to the hot separator (15) and the air is released to the atmosphere through the hot air outlet (7) and the hot water returns to the hot storage tank (3). Similarly, the cold water found in the cold receptacle (17) inside the heat exchanger (8) is. sent, along with some air, to the cold separator (18) where the air is released to the atmosphere through the cold air outlet (30) and the cold water returns to the cold storage tank (12).

[0083] The spray cam (23) allows switching on and off both the hot water spray and the cold water spray at the appropriate times; as well as the suction and exhaust cam (24) allows switching on and off at the appropriate times both the intake of new air and the exhaust of used air, cold water and hot water.

[0084] The switching of the valves of the expansion engine (1) is preferably carried out by electrical contacts (20) arranged in said expansion engine (1) which make up the valve circuit (25, 26, 27, 28, 29) as illustrated in Figures 2 to 7, as the piston (11) of the expansion engine (1) sets the inertia disc (22) in motion and, consequently, the valve control disc (33), the cams (23, 24) close and open the circuits of each electrical contact (20) in a sequential manner, activating and deactivating the valves (25, 26, 27, 28, 29) as the electrical contacts (20) are activated by the cams (23, 24).

[0085] As a result, the present invention provides an efficient expansion engine (1) in which the heat exchanger (8) requires materials that are not subject to large mechanical stresses and thermal stresses. In this way, the expansion engine, constructed according to the present invention, is not exposed to the problems related to intense thermal and mechanical shocks, as is characteristic of the current technique of thermal energy conversion system into mechanical energy.

[0086] Furthermore, due to the small differences in operating temperatures and pressures, the expansion motor (1) of the present invention proves capable of exhibiting a service life far superior to that of other energy conversion systems available in the state of the art.

[0087] The expansion motor (1) of the present invention is also substantially immune to the problems associated with conventional energy converters, such as corrosion, wear, low reliability due to the high thermal gradients and pressures used. The expansion motor of the present invention also offers outstanding performance in heat exchange, due to the considerable area for heat transfer provided by the large surface area of ​​the dense cloud of sprayed liquid.

[0088] Furthermore, the reliability of the expansion motor of the present invention is improved due to the fact that it does not require piping subjected to high pressure and, therefore, prone to rupture.

[0089] Another novel result of the energy conversion method provided by the present invention is the ability to store energy in a volume necessary for the operation of the expansion engine. By accumulating energy directly in the water, the energy storage can very easily be integrated with the energy and power production cycle.

[0090] This aspect is of utmost importance for all intermittent energy sources and, more specifically, for solar energy. Ultimately, the integrated capacity for energy storage and production presents itself as one of the main advantages of the expansion engine.

[0091] Thus, what could be a clear disadvantage due to low thermodynamic efficiency, compared to already established technologies, is largely compensated for by the ease of energy collection, storage, and conversion. This provides advantages such as greater utilization of stored energy in large quantities of heat, even when there are small temperature differences.

[0092] In the case of solar energy captured by conventional solar collectors, the heated water must be stored in substantially large, thermally insulated hot water tanks, allowing for the storage of solar energy in a large quantity of water heated to a relatively low temperature, just below 100°C.

[0093] The use of an expansion engine for harnessing solar energy has the remarkable characteristic of utilizing virtually the entire solar radiation spectrum: from infrared and visible light to ultraviolet. In other words, almost all available solar energy is captured, stored, and converted into usable energy. Thus, the solar radiation absorbed by the solar collector generates, despite the efficiency limitations imposed by thermodynamics, a significant amount of usable energy, especially when compared to conventional solar energy production technologies, whether thermal, molten sodium-based, or photovoltaic.

[0094] The method described in this invention has an efficiency comparable to that of photovoltaic panels (-15%) and fossil fuel combustion engines (-25% for gasoline and -30% for diesel). However, it offers a significant advantage by capturing and utilizing energy. 16.6% of the energy comes from a free and inexhaustible source, such as the Sun, while using an abundant resource like water in a closed circuit.

[0095] Having described some examples of preferred embodiments of the present invention, it should be understood that the scope of the present invention encompasses other possible variations of the inventive concept described, being limited only by the content of the claims alone, including possible equivalents.

Claims

CLAIMS 1. Expansion engine (1) for converting thermal energy into mechanical energy characterized by comprising: - a heat exchanger (8) comprising a piston (11) that delimits the height of said heat exchanger (8); said heat exchanger (8) being thermally insulated on its external part and connected to two air inlets (2), each controlled by an atmospheric air intake valve (25); - a hot water spray valve (26) configured so as to inject hot water into the heat exchanger (8), forming a hot water inlet at the bottom of one side of said heat exchanger (8); - a cold water spray valve (27) configured to inject cold water into the heat exchanger (8), forming a chilled water inlet at the bottom of the opposite side of said heat exchanger (8); - a hot receptacle (16) is disposed at the base of the heat exchanger (8) so as to collect the hot water sprayed in each cycle of the expansion engine (1); - a cold receptacle (17) is arranged at the base of the heat exchanger (8) in order to collect the cold water sprayed in each cycle of the expansion engine (1); - wherein the hot receptacle (16) is associated with a hot air and water exhaust valve (28) and a hot separator (15), wherein said hot separator (15) is connected by pipes to a hot air outlet (7) configured to conduct the discarded air to the atmosphere; and also connected to a heated fluid feedback circuit (9); and - the cold receptacle (17) is connected to said cold water spray valve (27) for cooling the heat exchanger (8), and a second heat exchanger outlet (8) connected to a cold air and water exhaust valve (29) for the cold separator (18); said cold separator (18) being connected to a cold air outlet (30) configured to conduct the discarded air to the atmosphere; and further connected to a cooled fluid feedback circuit (19).

2. Expansion motor (1), according to claim 1, characterized by: - the said cooled fluid feedback circuit (19) being formed by a cold storage tank (12) and a heat radiator (10) connected by a cold liquid circulation line (13), so that the water remaining in the cold separator (18) is routed to the cooled fluid feedback circuit (19); and - the heated fluid feedback loop (9) is formed by a hot storage tank (3) and a heater (4) connected by a heated liquid circulation line (5), so that the water remaining in the hot separator (15) is routed to the heated fluid feedback loop (9).

3. Expansion engine (1), according to claim 2, characterized in that the heater (4) of the heated fluid feedback circuit (9) is a solar collector, in which a heat storage fluid is circulated by means of a pump (not shown), between said solar collector and the hot storage tank (3), and inside the solar collector is disposed a radiation receiver consisting of a plurality of tubes for the Transfer of heat collected in the solar collector to the heat storage fluid.

4. Expansion motor (1), according to claim 2, characterized in that the heater (4) is capable of heating water through a natural heat source.

5. Expansion engine (1), according to claim 2, characterized in that the heat radiator (10) is positioned in such a way as to promote thermal contact between the cold storage tank (12) and the environment, wherein a heat storage fluid, which in a preferred version of the invention may be water, after being cooled in the heat radiator (10), is made to circulate by means of a pump, or spontaneously by means of a thermal siphon, between the heat radiator (10) and a cold storage tank (12).

6. Expansion engine, according to claims 1 to 3, characterized by comprising a cold feed pipe (14) between the cold storage tank (12) and the heat exchanger (8) and a hot feed pipe (6) between the hot storage tank (3) and the heat exchanger (8).

7. Expansion engine (1), characterized by the valves (25, 26, 27, 28, 29) being mechanically controlled.

8. Expansion engine (1), characterized in that the valves (25, 26, 27, 28, 29) are electrically controlled.

9. Expansion motor (1), according to claims 1 to 8, characterized in that the expansion motor (1) is connected to an electric generator (21).

10. Method of converting thermal energy into mechanical energy. using a motor as defined in claims 1 to 7, characterized by comprising: - a pre-cycle stage, in which the atmospheric air intake valves (25) are kept open to allow air intake until the entire volume of the heat exchanger (8) is filled and the piston (11) is kept expanded, while the hot air and water exhaust valve (28) and the cold air and water exhaust valve (29) are kept closed, and the expansion movement of the piston (11) causes atmospheric air to be drawn into the heat exchanger (8); - a first stage of isothermal compression at low temperature in which the spray cam (23) acts to open the cold water spray valve (27);and, either by the action of a starter motor or by human action, at start-up, or by the movement of the inertia disc (22), in continuous regime, the piston (11) compresses the air contained inside the heat exchanger (8) and, at the same time, cold water is injected through the base of the heat exchanger (8) via the cold water spray valve (27) maintaining the temperature of the compressed air constant throughout the stage, the air temperature being T1 = Tb, where T1 is slightly above a temperature (Tf; b ) from the cold storage tank (12) and the cold water is collected by the cold receptacle (17) at the base of said heat exchanger (8); - a second adiabatic compression stage, in which the contents of the heat exchanger (8) are isolated from the outside world by closing all the valves (25, 26, 27, 28, 29), and the piston (11) continues to compress the air contained inside the heat exchanger (8) until the air temperature reaches a temperature T3 = Ta, where T3 is slightly below a temperature ( Ty a ) of hot storage tank (3); - a third stage of isothermal expansion at high temperature, in which the spray cam (23) acts to open the hot water spray valve (26) and keeps the other valves (25, 27, 28, 29) closed, so that the air contained inside the heat exchanger (8) expands and pulls the piston (11) inside the heat exchanger (8) while the air is heated by thermal contact with the hot water sprayed by the hot water spray valve (26), in this stage the air temperature being kept constant and equal to T4=T3=Ta, and the hot water being collected in the hot receptacle (16) at the base of the heat exchanger (8); - a fourth adiabatic expansion stage, all valves (25, 26, 27, 28, 29) are kept closed, so as to isolate the contents of the heat exchanger (8) until the temperature returns to the value at the beginning of the first stage T1 = Tb, so that the air expands and pushes the piston (11) inside the heat exchanger (8); and - a post-cycle stage, in which isobaric exhaust of air, hot water and cold water occurs, where the suction and exhaust cam (24) acts to open the atmospheric air intake valve (25), the hot air and water exhaust valve (28), and the cold air and water exhaust valve (29), and the hot water spray valve (26) and cold water spray valve (27) are closed, and the hot water that was in the hot receptacle (16) inside the heat exchanger (8) is directed, along with some air, to the hot separator (15), and the air is released to the atmosphere through the hot air outlet (7), and the hot water returns to the heated fluid feedback circuit (9), and finally to the hot storage tank (3); and the cold water which was in the cold receptacle (17) inside the heat exchanger (8) is routed, together with some air, to the cold separator (18) where the air is released to the atmosphere through the cold air outlet (30) and the cold water returns to the cooled fluid feedback loop (19), and finally to the cold storage tank (12).

11. Method according to claim 10, characterized in that the valves (25, 26, 27, 28, 29) are mechanically controllable.

12. Method according to claim 10, characterized in that the valves (25, 26, 27, 28, 29) are electrically controllable.

13. Method according to claims 10 to 12, characterized in that the expansion engine (1) is connected to an electric generator (21).

14. Method, according to claims 10 to 13, characterized in that the pre-cycle step is performed at the beginning of the method and the post-cycle step is performed at the end of the method, wherein, during the performance of the method, the steps of isothermal compression, adiabatic compression, isothermal expansion and adiabatic expansion are performed sequentially and cyclically, defining a Quasi-Carnot cycle.

15. Method according to claims 10 to 14, characterized in that the cold storage tank (12) is a large body of water such as that of a river or an ocean.

16. Method according to claims 10 to 15, characterized in that the cold storage tank (12) is a body of water at ambient temperature such as a water table and a lake.

17. Method, according to claims 10 to 16, characterized in that the hot storage tank (3) is one of: a mass of water heated by said heater (4), a geothermal source, a mass of water originating from a geyser and / or a mass of water originating from a heated aquifer.

18. Method, according to claims 10 to 17, characterized in that the heater (4) uses the following means to heat a mass of water: heat from natural sources, solar energy and / or geothermal sources.

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