Power Generation Using Enthalpy Difference Gradient for Subatmospheric Regenerative Piston Engine

Abstract

A method for power generation via a liquid-gas phase transition. The method includes receiving atmospheric air as input to create an enthalpy difference gradient. A regenerative piston engine received atmospheric air. The regenerative piston engine collects heat generated from the enthalpy difference gradient. The regenerative piston engine converts the collected heat to a mechanical form of energy at the regenerative piston engine.

Claims

1. A method for power generation via a liquid-gas phase transition comprising: receiving atmospheric air as input to create an enthalpy difference gradient; supplying, as a result of receiving, the received atmospheric air to a regenerative piston engine; collecting heat generated from the enthalpy difference gradient; and convert the collected heat to a mechanical form of energy at the regenerative piston engine.

2. The method of claim 1, wherein receiving comprising receiving the atmospheric air as input to create the enthalpy difference gradient at a heat and mass exchanger.

3. A method for power generation via a liquid-gas phase transition comprising: receiving atmospheric air as input to create an enthalpy difference gradient; supplying, as a result of receiving, the received atmospheric air to a subatmospheric regenerative piston engine; collecting heat generated from the enthalpy difference gradient; and convert the collected heat to a mechanical form of energy at the subatmospheric regenerative piston engine.

4. A method for power generation via a liquid-gas phase transition comprising: receiving atmospheric air as input to create an enthalpy difference gradient via a heat pipe, said heat pipe evaporating and condensing a working fluid; supplying, as a result of receiving, the received atmospheric air to a subatmospheric regenerative piston engine; collecting heat generated from the enthalpy difference gradient; and convert the collected heat to a mechanical form of energy at the subatmospheric regenerative piston engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention of power generation using enthalpy difference gradient for the subatmospheric regenerative piston engine of will be more clearly understood by reference to the following detailed description, when read in conjunction with accompanying drawing, wherein like reference characters refer to like parts throughout the several views and in which:

[0056] FIG. 1 is a schematic depiction of the proposed subatmospheric regenerative piston engine system.

[0057] FIG. 2A-2D is show different stages in operation of the proposed subatmospheric regenerative piston engine.

[0058] FIG. 3 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the solar air heater 23 as a source of heat.

[0059] FIG. 4 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the fluid burner 24 as a source of heat.

[0060] FIG. 5 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the solar air heater 23 and auxiliary natural gas burner 25 as a source of heat.

[0061] FIG. 6 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the air cooler 27 for preliminarily pre-cooling and pre-dehumidifying of the working fluid after it is pushed from expansion zone.

DETAILED DESCRIPTION

[0062] Below is a table of reference numbers and elements used in the description below.

TABLE-US-00001 Reference Numeral Element 1 Outside airflow in 2 Input heat Qin 3 M-Regenerator 4 Dry channel 5 Wet channel 6 Product channel 7 Regenerative piston engine 8 Piston 9 Cylinder 10 Flywheel 11 Shaft 12 Mechanism for converting the linear motion of the piston to the rotation motion of the shaft 13 Heat Qout from the dry channel to the wet channel 14 Moist and hot airflow after the wet channel 15 Moist and hot airflow coming to the product channel 16 Cold and dry airflow after coming through the product channel 17 Heat of regeneration Q.sub.reg from the product channel to the wet channel 18 Condensed water from the product channel and air cooler for wetting of the wet channel 19 and Intake and exhaust valves for the inflow and outflow of 20 working fluid through an expansion zone 21 and Intake and exhaust valves for the inflow and outflow of 22 working fluid through an compression zone 23 Solar air heater 24 Fluid burner 25 Auxiliary natural gas burner 26 Dry airflow which is discharged into the atmosphere 27 Air cooler 28 Pre-cooled and pre-dehumidified airflow after the air cooler 29 Finally the cold and dry airflow after the product channel in a scheme with the air cooler 30 Outside airflow coming to the air cooler 31 Pre-heated outside airflow after the air cooler which is directed to the dry channel of the M-Regenerator 32 Moist and hot airflow after the wet channel in a scheme with the air cooler 33 Moist and hot airflow coming from the expansion zone to the air cooler

[0063] In one embodiment (see FIG. 1), the subatmospheric regenerative piston engine comprises the M-Regenerator 3 and piston engine 7 as the double-acting piston engine. The M-Regenerator 3 is the key component of this piston engine, providing very high cycle regeneration rate. The M-Regenerator 3 contains the dry 4, wet 5 and product 6 channels. Besides, any wet channel 5 is always placed between the dry 4 and product 6 channels. There is the heat exchange mechanism between these channels. Any wet working channel 5 directly connected to the dry working channel 4, the wet working channels 5 operatively form a water layer therein, the wet working channels 5 are separated from the dry working channels 4 and from the product channels 6 by a respective common heat-conducting wall thereby establishing pair-wise heat transfer relations there between; and a water line 18 connecting the bottom of the M-Regenerator 3 with the wet working channels 5. It is important to emphasize, for the proposed piston engine 7, the additional water is not needed, and because it constantly replenishes water from the exhaust working fluid during its passing along the product channels 6.

[0064] The product channels 6 are placed between an outlet of the airflow 15 from expansion zone and an inlet of the airflow 16 to compression zone of engine.

[0065] The piston engine 7 contains a cylinder 9 with a movable piston 8, which is connected to a power output shaft 11 by an appropriate mechanism 12 for converting the linear motion of the piston 8 to the rotating motion of the shaft 11.

[0066] Referring to FIG. 1, a cylinder 9 has the cylinder expansion zone (left side) with an intake 19 and exhaust 20 valves for the inflow and outflow of working fluid through an expansion zone. Also a cylinder 9 has compression zone (right side) with an intake 21 and an exhaust valves 22, which are provided for the inflow and outflow of working fluid through a compression zone.

[0067] Consider the direction and order of movement for airflow as the working fluid in the proposed engine. Operation of the engine of FIG. 1, in accordance with the present invention, begins when an airflow 1 as the working fluid, supplied from the outside, has heat exchange contact with the input heat 2 (Q.sub.in), wherein the airflow 1 increases its temperature, and, thereafter it is directed at first into the dry channel 4, and next into the wet channel 5 of the M-Regenerator 3. Then the airflow 1 is heated and moisturized therein and further as the saturated airflow 14 with high enthalpy it is drawn and directed for expansion process through the intake valve 19 to the expansion zone of a piston engine 7 (left side), where a pressure below the atmospheric pressure. After some actions inside of a cylinder 9 of an engine 7 (see description of these actions below) the working fluid as airflow 15 is directed through the exhaust valve 20 to the product channel 6 of the M-Regenerator 3. Later this airflow as the dry and cold airflow 16 with small enthalpy is focused for compression process through the intake valve 21 to the compression zone of a piston engine 7 (right side). After some actions inside of a cylinder 9 (see description of these actions below) this airflow as airflow 26 is discharged through the exhaust valve 22 into the atmosphere.

[0068] Consider different stages (processes) in operation of the proposed subatmospheric regenerative piston engine 7 (see FIGS. 2A-2D). For convenience of description, the engine operation will begin with the compression process of the working fluid in the cylinder 9 (see FIG. 2A).

[0069] The working fluid as the heated and moisturized airflow 15 (see FIG. 2A) is pushed from expansion zone of a cylinder 9 to the product channel 6 of the M-Regenerator 3 and in this an exhaust valve 20 is opened. Passing along the product channel 6 the heated and moisturized airflow 15 is cooled and dehumidified approaching the dew point temperature of outside air. During this process the heat of regeneration 17 (Q.sub.reg) is transferred from the product channel 6 to the wet channel 5. At the same time, the pressure behind the piston 8 (right side) decreases, the intake valve 21 is opened. The intake valve 19 and exhaust valve 22 are closed.

[0070] The fully heated and moisturized saturated airflow 15 (see FIG. 2B) is driven to the product channel 6 of the M-Regenerator 3 with following its cooling and dehumidification, which leads to reduction of enthalpy of airflow 15. After the working fluid as the cold and dry airflow 16 with small enthalpy is directed through the intake valve 21 to the compression zone of a cylinder 9 behind (right side) of the piston 8. This leads to the maximum pressure drop (differential pressure) in front (left side) and behind (right side) of the piston 8. The exhaust valve 20 and intake valve 21 are open; the intake valve 19 and exhaust valve 22 are closed.

[0071] This process (see FIG. 2C) produces the useful work. The intake valve 19 is opened and the new portion of the working fluid as outside airflow 1 is directed at first through the dry 4 and after wet 5 channels. Then this working fluid as the heated and moisturized saturated airflow 14 with high enthalpy is directed through the intake valve 19 to the expansion zone (left side) of a cylinder 9.

[0072] Passing along the dry channel 4 the working fluid is cooled approaching the dew point temperature of outside air. During of this process the heat 13 (Qout) is transferred from the dry channel 4 to the wet channel 5. After passing through the dry channel 4 the same cooled airflow 1 is directed concurrently to the wet channel 5, where it is heated, moistened by water. Next it is drawn as the saturated airflow 14 with high enthalpy by a piston 8 to the expansion zone of a cylinder 9 of an engine 7. Herewith the exhaust valve 20 is closed. A piston 8 starts to move from a left side (expansion zone) to a right side (compression zone) for direction of the downward pressure (or enthalpy), transmitting mechanical energy to flywheel.

[0073] The driving force for a piston 8 movement is the enthalpy difference gradient which was created by the working fluid on both sides of the piston 8. On the left side of the piston 8 is brought the high enthalpy of the airflow 14 on the right side of the piston 8 simultaneously is brought the low enthalpy airflow 16. The intake valve 21 is opened and the exhaust valve 22 is closed.

[0074] There is a moment (see FIG. 2D) when the pressure in front of and behind the piston 8 is aligned; herewith the intake valve 21 is closed. The exhaust valve 22 opens and begins the release of the working fluid as the exhaust airflow 26 into the atmosphere. The intake valve 19 is open, and the exhaust valve 20 is closed.

[0075] Then all four processes described above are repeated in the same sequence.

[0076] A higher air humidity ratio and temperature of the airflow 14 (see FIG. 1), which is directed from the wet channel 5 through the intake valve 19 to a cylinder 9 for expansion process, reduces its density that enhances the thermal efficiency of this gas expansion process.

[0077] Thereafter, the working fluid from the expansion zone of the regenerative piston engine 7, as the moist and hot airflow 15, is directed through the exhaust valve 20 for cooling and dehumidifying to the product channels 6 of the M-Regenerator 3. Therein, the saturated airflow 15, at a predetermined low pressure is cooled below the wet bulb temperature and it approaches the dew point temperature of outside air with reducing its absolute humidity. This low temperature helps condensing vapor of water 18 from the airflow 15. Consequently, moisture contained in the airflow 15 is condensed and the quantity of the airflow 15 decreases. Herewith density of the airflow 15 increases. After (see FIG. 1), the working fluid as the airflow 16 is directed through the intake valve 21 to the compression zone of a cylinder 9. Thus, a power necessary for driving of the piston 8 for compression process is reduced by increasing of density and reducing quantity of the airflow 15, which as the airflow 16 is directed to a cylinder 9 for compression process.

[0078] Water 18 extracted from the airflow 15 is drained and recovered. The condensable cold water 18 is directed by a water line from the product channel 6 for wetting of the wet channels 5. Therefore, additional water will not be needed for operating the M-Regenerator 3, because it constantly liberates water from the airflow 15. The line for the condensed water 18 can include a condensate separator for cleaning some polluting condensate components and additional replenishing of water, if it is necessary.

[0079] The cooling and dehumidifying processes for the airflow 15 inside of the product channel 6 result in a reduction of volume of the airflow 15 inside the product channels 6. This substantially increases the density of the airflow 15 supplied as the airflow 16 into the compression zone of a cylinder 9. It increases the efficiency of operating of compression process, when a piston 8 is moving inside of cylinder 9 from a left side to a right side.

[0080] After passing through the product channels 6 (see FIG. 1), the working fluid as the airflow 16 is coming into the compression zone of a cylinder 9, compressed to the atmospheric pressure by a piston 8 (during its moving from a left side to a right side) and discharged into the atmosphere through the exhaust valve 22 as the airflow 26. This provides effective cooling and dehumidifying processes for the working fluid reducing its enthalpy, when the airflow 16 passes through the product channels 6. A piston 8, during its moving from a left side to a right side, compresses the cold and dry airflow 16 which enthalpy is lesser. Thereby pressure of the airflow 16 is rising therein to the atmospheric pressure. Herewith the exhaust valve 22 is opened, and the working fluid as the airflow 26 is ejected through the exhaust valve 22 into the atmosphere.

[0081] The process of extraction of the sensible and latent heat of regeneration 17 (Q.sub.reg) from the moist and hot airflow 15 (see FIG. 1), during its passing through the product channels 6, is used to heat and humidify the outside airflow 1, during its passing through the wet channels 5. Condensed water 18 from the airflow 15 inside the product channels 6 adds a significant amount of heat of regeneration 17 (Q.sub.reg), which transfers from the product channel 6 to the wet channels 5 of the M-Regenerator 3. It is important to consider that it takes 1 Btu to cool one pound of water at 1 F. and 1040 Btu to condense that same one pound of water vapor. Adding the latent heat has a significant effect on the thermal efficiency of the proposed piston engine.

[0082] As described above (see FIG. 1), the outside airflow 1 before was preheated by the input heat 2 (Q.sub.in) and thereafter, as the working fluid, is at first passed through the dry channels 4 and next into the wet channels 5. Next the heated and moisturized working fluid with high enthalpy as the saturated airflow 14 is drawn from the M-Regenerator 3 through the intake valve 19 to the expansion zone of a piston engine 7 (left side), where a pressure is below the atmospheric pressure.

[0083] During the passing through the wet channels 5, the working fluid significantly increases its absolute humidity and temperature, and consequently increases its the enthalpy, due to of the sensible and latent heat of regeneration 17 (Q.sub.reg), which is transferred from the product channel 6 to the wet channel 5 of the M-Regenerator 3. It is important emphasize that absolute humidity of the airflow 14, after its passing along the wet channel 5, is always more than that obtainable from any other known methods of humidifying. The increased humidity and temperature raises the volumetric flow rate of the working fluid through the expansion process of the piston engine7. A higher volume of the airflow 14 means that there is more air to force a piston 8 to move a greater distance, and thereby increasing its power output through the embodiments of the invention.

[0084] The suggested invention of power generation, using enthalpy difference gradient for the subatmospheric regenerative piston engine of FIG. 1, offers a significant improvement in the thermal efficiency of producing power (more than 70%). It is possible to get high thermal efficiently for the proposed piston engine 7 only due to using of the M-Regenerator 3 together with this piston engine, as this is shown on FIG. 1. It gives an opportunity to dehumidify and cool (approaching the dew point temperature of outside air) the working fluid, which is directed as the airflow 16 from the product channel 6 with small enthalpy for compression process through the intake valve 21 into the compression zone of a cylinder 9. It increases their power output and efficiencies. Simultaneously the working fluid as the airflow 14 is humidified and heated prior to its extension through extension zone of the piston engine 7, where it with high enthalpy is directed from the wet channel 5 for expansion process via the intake valve 19 to expansion zone of a cylinder 9. It also increases their power output and efficiencies. Moreover, both these processes for the airflow 16 (with small enthalpy) and airflow 14 (with high enthalpy) are realized more effectively than traditional evaporative cooling and humidifying processes, and are effected using only one apparatus as the M-Regenerator 3.

[0085] Thereby the M-Regenerator 3 is the unique heat and mass exchanger which through the M-Cycle realizes the best heat recovery process. The M-Regenerator 3 effectively ensures the production of the two air streams 14 and 16 as the working fluids, which the enthalpy difference gradient is significant value, and that it is a driving force for the production of mechanical energy by the proposed piston engine 7. Moreover, this enthalpy difference gradient increases exponentially with increasing temperature of the input heat 2 (Q.sub.in).

[0086] Since the traditional power engines have the high-temperature and high-pressure working fluids, it is difficult to recover power from unused, high-temperature or atmospheric exhaust gases produced by manufacturing processes by the old-style power engine cycles. It is reason why the costs of the heat recovery are intolerably high.

[0087] As stated above, the M-Regenerator 3 is used in the proposed subatmospheric regenerative piston engine, wherein the heating and mass recovery processes are effected at the atmospheric pressure. It significantly improves all characteristics of the M-Regenerator 3 as well as the whole piston engine 7. This atmospherically supplied M-Regenerator 3 and the whole piston engine 7 are preferred as an engine for motorcycle or car industries and also in the residential or commercial setting, being due to their much lower cost, simplicity of design, and ease of maintenance. It is also noted that most of existing power engines typically have material problems, since the materials, they are built from, not only don't satisfactorily withstand high pressures, but also don't withstand high pressures at high temperatures, particularly in stack gases and combustion products, which tend to be corrosive. An effort to overcome these problems usually results in solutions involving considerable expenses, rendering power plants inefficient. The proposed subatmospheric regenerative piston engine 7 of FIG. 1 operates with lower pressures at lower temperatures, which solves these problems and provides this piston engine 7, incorporating the M-Regenerator 3, for being more efficient and inexpensive.

[0088] FIG. 3 illustrates yet another embodiment of the inventive of power generation using enthalpy difference gradient for the subatmospheric regenerative piston engine, similar to the illustrated on FIGS. 1 and 2, in which contains the solar air heater 23 as a source of heat.

[0089] With the advent of the energy crisis there has been substantial emphasis placed on the utilization of renewable energy sources, such as solar heat. One of the principal problems associated with effective utilization of solar heat has been the cost of storing significant quantities of such heat that is the cost of a heat accumulator for use during non-daylight hours or during extended periods, when the sun was obscured by cloudy or overcast skies. Indeed, the high cost of construction of the existing storage systems has minimized the effective utilization of solar heat.

[0090] It is also noted that existing solar heat accumulators, such as solar air heaters of the existing solar power systems and engines, which are used to realize the Brayton, Diesel, Otto or combine cycles, have significant material problems, since the materials do not typically withstand high pressures. Existing solar heat accumulators, such as solar air heaters for transforming the concentrated solar radiation energy to a high pressure air are complex, expensive and excessively sized. An effort to overcome these problems usually results in solutions involving considerable cost penalties, so that efficient solar power systems and engines remain unavailable to the general public. The proposed subatmospheric regenerative piston engine, and its element as the solar air heater 23 (see FIG. 3), operates with lower pressures, and resolves these problems and provides a more efficient and inexpensive solar thermally driven power system incorporating the piston engine 7.

[0091] The traditional solar air heater has typically comprised a device for transferring the concentrated solar radiation energy to a high temperature/high pressure air as by means of a relatively complex heat exchanger. The high pressure air, in turn, is expanded through a high pressure turbine or piston. However, these power systems and engines have not been widely used because of the complexity and expense of the high pressure solar heat exchanger, together with the required relatively large sizes of the heat exchanger.

[0092] The proposed subatmospheric regenerative piston engine comprises the improved the solar air heater 23 with a high thermal efficiency, which also eliminate expensive and complicated heat transfer apparatuses, and which are capable of operating at relatively low temperatures and pressures, using inexpensive and light-weight materials.

[0093] The solar air heater 23 (shown in FIG. 3) captures heat from the sun by the outside airflow 1 supplied there into, and transfers through the M-Regenerator 3 this heat by the working fluid as the moist and hot airflow 14 with high enthalpy to the piston engine 7. In general, the solar air heater 23 comprises an interior space, a glazing surface oriented to the sun, a plate which absorbs solar radiation and converts it into heat, and intake and discharge passages for a circulating heat-transfer fluid as outside air 1. The solar air heater 23 is said to be air-based because for this proposed subatmospheric regenerative piston engine the heat transfer fluid is air. A system as a whole is said to be active if it utilizes a device for compelling circulation of air, rather than relying on natural convection.

[0094] In a solar air heater of any type, there are, of course, time periods, during which the solar energy is not sufficiently absorbed to provide the necessary quantity of heat for the particular power engine. Therefore, an auxiliary heating system is normally provided in combination with the solar air heating system. The source of auxiliary heat supply is a major problem. It depends on the field of application of the proposed piston engine. For motorcycle or car industries it is rational to use the liquid fuel or balloon gas, propane, and the like for the auxiliary heating system. For residential or commercial setting it is normal to use energy from a commercial utility grid, either pipeline natural gas or electricity which can be available at a uniform price. Preferably, the withdrawal of energy from a gas pipeline may be made at any time a demand exists.

[0095] FIG. 4 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the fluid burner 24 as a source of heat that may optionally use any type of fuel.

[0096] All existing combustion power engines as the internal combustion piston engines or a gas turbine engines are used the fuel (gas or liquid) which is supplied for combustion process under high pressure. An atmospheric combustion for existing power engines is impossible and heat of the atmospheric exhaust gas cannot be used. Thus, all existing combustion power engines have difficulties in using various gaseous or liquid fuels, solid fuels and unused high-temperature gases. It is structurally impossible for these engines to reduce emission of heat from the system by circulating the exhaust gas, which is disadvantageous with respect to the thermodynamic cycle. As mentioned above, in a conventional power engines, the pressurized fuel must be supplied to the combustor or burner because the pressure in the combustor is high. It is the reason why the costs of the burner systems are intolerably high.

[0097] In the proposed subatmospheric regenerative piston engine (shown in FIG. 4), a fluid burner 24 is used, wherein the combustion or burning processes are provided at the atmospheric pressure. It significantly improves all characteristics of the fluid burner 24. This is due to their much lower costs, simplicity of design, and ease of maintenance.

[0098] Sometimes it is rational to use for the proposed subatmospheric regenerative piston engine two source of heat. FIG. 5 shows an embodiment of the suggested engine, which comprises two source of heat: (1) solar air heater 23, and (2) auxiliary natural gas burner 25. Together with natural gas, it is possible to use any kind of gas, liquid or solid fuel, for example, gasoline, kerosene, coal, bio fuel, wood and etc. Accordingly, for any kind of fuel it is used for a fit design of the combustion chamber. Today, natural gas is the best popular fuel for the stationary conditions and gasoline for transport. Also, this power system comprises required valves (they don't show). It provides for an opportunity for this engine to selectively work in different thermal modes, using (a) only solar air heater 23, or (b) only auxiliary natural gas burner 25, or (c) together the solar air heater 23 and auxiliary natural gas burner 25.

[0099] Since the natural gas input as fuel of the atmospheric pressure is fed into the auxiliary natural gas burner 25 without increasing the pressure of fuel, the proposed subatmospheric regenerative piston engine does not need any fuel compressor or pump.

[0100] It is important emphasized that auxiliary natural gas burner 25 (see FIG. 5) can be designed for heating process for the working fluid through as direct and as indirect ways. It can be the direct combustion chamber, where the exhaust gas after combustion process is mixing with the working fluid through the direct contact. In this case the combustion process is more efficient because not loses of heat and whole heat of combustion is transferred for the working fluid. Disadvantage of this technology is contamination of the working fluid. Using the indirect heating process through heat exchange surface for the working fluid, it is possible not pollute of the working fluid. But in this case the combustion process is less efficient, because some part of the heat is lost by removing of the exhaust gases to the atmosphere. For proposed subatmospheric regenerative piston engine it is possible to use both technologies.

[0101] Sometimes it is rational to use the auxiliary natural gas burner 25 with direct heating process for the working fluid. A higher air humidity ratio and temperature of the airflow 14, which enters to the auxiliary natural gas burner 25, creates a lower density of the airflow 14 by growing its volumetric flow rate through its increasing of temperature and humidity. It is better for the efficiency of the expansion process inside of a cylinder 9, when the moist and hot airflow 14 from the auxiliary natural gas burner 25 is directed through the intake valve 19 to the expansion zone of the piston engine 7.

[0102] Raising of temperature and humidity of the airflow 14, which is directed to the auxiliary natural gas burner 25 (see FIG. 5), requires less heating of the air fuel mixture, and is therefore more efficient. What is more surprising is that adding humidity to the airflow 14 will also reduce the fuel needed. The added humidity increases the mass flow of the input airflow 14 at a higher temperature requiring less fuel to heat this airflow 14 before its coming to the expansion zone of the piston engine 7.

[0103] Water vapor has other positive effects. For example, it comprises polyatomic molecules (three atoms H.sub.2O as opposed to two atoms like O.sub.2 or N.sub.2), that can radiate and be radiated to. This ability to radiate reduces hot spots in the burning process of the auxiliary natural gas burner 25 giving more complete burning with about half the amount of NO.sub.x, an endothermic or energy draining reaction. This is similar to but better than an existing automobile engine that uses a small amount of exhaust gas recirculation or CO.sub.2 plus H.sub.2O recirculation to lower its NO.sub.x. The higher efficient burning at lower temperatures also decreases the carbon monoxide (CO) in the same way as reducing NO.sub.x.

[0104] Using the auxiliary natural gas burner 25 with direct heating process for the proposed piston engine 7, pollution is dramatically (at times) reduced due to the water vapor of the moist and hot airflow 14 creating a more even burning process inside of the auxiliary natural gas burner 25 during the combustion. For example, the most toxic pollution from combustion process NO (NO.sub.x) issue is reduced by 10.3 times and [CO] concentration is reduced by 1.95 times (see a paper by B. Soroka et al.: DEVELOPMENT OF CONPUTATION TECHNIQUES AND DATA GENERALIZATION ON BURNING VELOCITY OF DRY AND HUMIDIFIED INFLAMMABLE GAS FUEL-OXIDANT MIXTURES, International Journal of Energy for a Clean Environment, Volume 12, p. 187-208, 2012).

[0105] The M-Regenerator 3 tends to be the most expensive single component in the proposed subatmospheric regenerative piston engine that is equipped therewith. The M-Regenerator 3 extracts through the M-Cycle the sensible and latent heat of regeneration 17 (Q.sub.reg) from the product channel 6 (where the working fluid as airflow 15 is passing through) to the wet channel 5 (where the working fluid as airflow 1 is passing through). The M-Regenerator 3 provides an indirect evaporative cooling process through the M-Cycle having efficient wicking action, allowing easy wetting of the surface area of the wet channels 5 without excess water (which would cool the water rather than the air).

[0106] After passing through the solar air heater 23 (see FIG. 5), the working fluid as airflow 1 is directed at first to the dry channels 4, and next to the wet channels 5 of the M-Regenerator 3, and thereafter it as the moist and hot airflow 14 is sent off to the auxiliary natural gas burner 25.

[0107] Only the above described procedure and sequence of processes of the proposed piston engine ensures its high engine thermal efficiency and lower fuel consumption by the auxiliary natural gas burner 25.

[0108] Sometimes it is rational to realize two stage cooling and dehumidifying processes for the working fluid, before it is directed with small enthalpy through the intake valve 21 for the compression process of an engine 7.

[0109] The air psychrometric saturation line slopes such that cool air has a greater change in energy for a given humidity ratio change than at higher temperatures. This means that in the M-Regenerator 3 there will be more condensation than evaporation, producing the condensed water 18 from water vapor of airflow 15, which is passing along the product channel 6. It is desirable to maintain a balance between the evaporative and condensing processes as condensate amount in the product channel 6 was close to the amount of evaporated water in the wet channel 5. This allows for getting of maximum efficiency of the heat recovery process for the M-Regenerator 3, and it means the maximum thermal engine efficiency for the proposed piston engine. For this purpose, it is desirable sometimes to implement a pre-condensation process, using additional apparatus as the air cooler, which will help to comply with regulation of evaporation and condensation balance through the M-Regenerator 3. Because using the M-Regenerator 3 there will be more condensation than evaporation, it expedient to realize the pre-condensing process for airflow before its coming to the product channel 6 of the M-Regenerator 3.

[0110] FIG. 6 is a schematic depiction of the proposed subatmospheric regenerative piston engine system which contains the additional air cooler 27 for preliminarily pre-cooling and pre-dehumidifying of the working fluid, before it is pushed to the product channel 6 of the M-Regenerator 3.

[0111] As the air cooler 27 it is possible to use any kind of a heat exchange apparatus, which can realize the indirect heat exchange process between outside air 30 and the moist and hot airflow 33 coming via the exhaust valve 20 from the expansion zone of the piston engine 7. Because temperature and absolute humidity of outside air 30 is always less than temperature and absolute humidity of the moist and hot airflow 33, last, after passing through the air cooler 27, reduces its temperature and absolute humidity. In connection with this outside air 30, after passing through the air cooler 27, increases its temperature due to the selection of the sensible and latent heat flux from the moist and hot airflow 33. After, the working fluid as the preheated airflow 31 (see FIG. 6) is directed from the air cooler 27 through heating by input heat 2 (Q.sub.in) to the dry channel 4 of the M-Regenerator 3. Before its coming to the dry channel 4 airflow 31 has heat exchange contact with the input heat 2 (Q.sub.in), wherein the airflow 31 increases its temperature, and, thereafter it is directed at first into the dry channel 4, and next into the wet channel 5 of the M-Regenerator 3. In this case amount of the necessary input heat 2 (Q.sub.in), which we have to spend for heating of airflow 31, will be less because before airflow 31 was preheated during its passing through the air cooler 27. Thereby using the air cooler 27 it gives the opportunity not only to improve the performance of the M-Regenerator 3, but it also is provided an opportunity to recovery some part of sensible and latent heat from the moist and hot airflow 33. It also increases the efficiency of the proposed piston engine.

[0112] The moist and hot airflow 33, after passing through the air cooler 27, reduces its temperature and absolute humidity by cooling of the colder outside air 30. This low temperature of the available outside air 30 helps partly condensing vapor of water 18 from the airflow 33. Consequently, moisture contained in the airflow 33 partly is condensed and the quantity of the airflow 33 decreases. After, the working fluid (see FIG. 6) as the pre-cooled and pre-dehumidified airflow 28 is directed from the air cooler 27 to the product channel 6 of the M-Regenerator 3 for its final cooling and dehumidification. Later the cold and dehumidified working fluid as the airflow 29 is sendoff through the intake valve 21 for the compression process of a piston engine 7.

[0113] The condensed water 18 is directed by a water line from the air cooler 27 for wetting of the wet channels 5 of the M-Regenerator 3. Thereby in this case (see FIG. 6) the drain condensed water 18 can come for wetting of the wet channels 5 from two sources: water 18 condensed from the airflow 33 in the air cooler 27; and water 18 condensed from the airflow 28 in the product channel 6 of the M-Regenerator 3. Therefore, additional water will not be needed for wetting of the wet channels 5 of the M-Regenerator 3, because it constantly liberates water from the airflows 33 and 28. The lines for condensed water 18 can include a condensate separator for cleaning some polluting condensate components and additional replenishing of water, if it is necessary.

[0114] Due to very high humidity of the saturated airflow1, after its passing along the wet channels 5, (up to 0, 5 kg vapor in 1 kg of dry air) the air-vapor blend enthalpy at the temperature of 300-400 C. is equal to the combustion gas enthalpy at the temperature of 1300-1400 C. for traditional engines. The ability to obtain a high enthalpy of the working fluid through its low temperature is a crucial factor in a significant reduction in the irreversible losses of the proposed piston engine, its pollution and also cost and size.

[0115] Thus, the proposed power generation method and regenerative piston engine provide very high thermal efficiency (more than 70%) at relatively low air-vapor flow temperature (but high enthalpy). It opens the principal opportunity of the proposed piston engines development operating without organic fuel. It is possible to use for these engines only the solar air heater 23 (see FIG. 3) without the chemical fuel energy, abandoning of the auxiliary natural gas burner 25 (see FIG. 5). Instead, only solar and psychrometric energy, as two kinds of renewable energy, can be used, as well as various industrial waste heat sources.

[0116] Also it gives unique opportunity to create the new kind of the efficient solar cars using the existing low temperature solar air heater (as a source of the heat energy instead of fuel) through the proposed piston engines.