WO2010067359A2

WO2010067359A2 - Closed loop solar energy system with a push-pull electric generator

Info

Publication number: WO2010067359A2
Application number: PCT/IL2009/001162
Authority: WO
Inventors: Abraham Sadeh
Original assignee: Abraham Sadeh
Priority date: 2008-12-09
Filing date: 2009-12-09
Publication date: 2010-06-17
Also published as: IL195823A0; WO2010067359A3

Abstract

A solar energy system comprising: a solar collector for vaporizing a heat transfer fluid; an electrical generator downstream said solar collector and including a push-pull motor having a fluid inlet valve and outlet valve; a piston and crank shaft; a condenser tank downstream of said electric generator; a heat transfer fluid temperature control unit; piping within which the heat transfer fluid is transported; a pressure sensor disposed between the solar collector and generator; and a control system, wherein the solar collector comprises one or more low-diameter collector tubes with an inner-diameter on the order of millimeters; and the generator is designed so that the inertia produced by the crank shaft and/or the pressure decrease in the system's piping due to condensation downstream of the generator aids the movement of the piston.

Description

CLOSED LOOP SOLAR ENERGY SYSTEM WITH A PUSH-PULL

ELECTRIC GENERATOR

FIELD OF THE INVENTION

The present invention relates to a solar energy system, in particular such system for providing electrical energy.

BACKGROUND OF THE INVENTION

An electric solar energy system provides a means for deriving electrical energy from solar energy. Thermal energy can also be derived from such a system.

US 4,409,129 (Johnston) discloses a closed loop solar collector system including a linear concentrating parabolic reflector, a linear vaporizer tube horizontally aligned along the focal line of the parabolic reflector, and a fluid metering assembly attached to the input end of the vaporizer tube for precisely metering a quantity of a vaporizable heat transfer fluid from a supply tank to the vaporizer tube. Solar energy concentrated by the parabolic reflector on the vaporizer tube vaporizes the heat transfer fluid. The heated vapor flows out the outlet end of the tube opposite the fluid metering assembly through a pipe and enters a heat exchanger. The heat exchanger contains a heat absorptive medium which absorbs heat from the vaporized fluid to cause the fluid to condense and release its latent heat of vaporization to the heat absorptive medium. The condensed fluid flows back to the heat storage tank for re-use under pressure provided by the vaporized fluid entering the heat exchanger. A thermoelectric generating system using the present closed loop solar system is connected to the heat exchanger and utilizes a separate loop with a working fluid, such as ammonia, to drive an electric generator.

US 4,171,617 (Sakamoto et al) describes a solar thermal electric power system in which a solar collector; a heat storage vessel filled with a thermal storage material adapted to effect a phase change between solid and liquid internally; a turbine; a condenser; a condensate storage tank; and a feed water pump are connected in a closed loop by suitable conduits. A first control valve is provided en route between the solar collector and a heat storage vessel. A steam accumulator filled with water is connected via a second control valve in a pipe route between the solar collector and the first control valve, as well as to a pipe route between the first control valve and the heat storage vessel via a third control valve. The temperature of a fluid flowing out of the solar collector is detected, and when the temperature detected is to be lower than a set temperature, then the first control valve is controlled so as to be closed, while the second control valve is opened.

US 4,176,655 (Levy) discloses a solar energy collection and utilization storage system constructed by using a lenticulated transparent element closed at the back to form channels which are used to carry an energy storage fluid. The lenticulations are designed as light trapping surfaces so that virtually all of the energy from the sun at any time of day falling on the sheet is trapped by the lenticulations and transferred to an energy storage fluid which is in the passages formed by the lenticulations and the back cover panel. The rate of flow through the solar collector panel is controlled by a thermostatic valve element which opens the flow when the fluid reaches a predetermined temperature. The energy storage fluid is a dispersion of a crystalline polymer in a heat transfer fluid which has the capacity of storing heat by a latent heat of crystallization as well as by sensible heat. By use of a suitable polymer the energy storage fluid can store energy at a high enough temperature to produce a significant amount of shaft power utilizing a heat engine. The remainder of the system comprises a storage container, suitable fluid connecting lines, a heat exchanger to extract sensible heat, and means to circulate the fluid through the system. The combination of the flat panel collector and the efficient energy storage fluid combine to make an effective collector system which can be employed to drive a heat pump for heating and cooling or to generate electric power.

The disclosure of the cited art is fully incorporated herein by reference.

SUMMARY OF THE INVENTION

The present invention relates to a closed loop solar energy system. Hot gaseous fluid exiting a solar collector of the system is introduced into a generator with a push-pull engine for producing electrical energy. The solar collector is preferably a flat plate type collector having heat transfer tubes on the millimeter scale, however, according to some embodiments, radiation concentrating type collectors (e.g. parabolic or with a plurality of focusing mirrors), are also usable.

It is a particular feature of the present invention that the solar collector comprises one or more collector tubes of low-diameter (thin), in particular with collector tube(s) having an inner-diameter on the order of millimeters, thereby affecting a rapid heat transfer without requiring a concentrating solar collector or other such expensive collectors and/or solar tracking. For example, the volume in the collector tubes for each square meter in area is 10 cubic centimeters.

It is another particular feature of the present invention that the system and the generator are designed so that the inertia produced by the crank shaft of the generator's motor and/or the pressure decrease in the system's piping system due to condensation downstream of the generator aids the movement of the piston.

Accordingly, in embodiments of one aspect of the invention there is provided a system as defined in claim 1; and particular embodiments are defined in claims depending therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood upon reading of the following detailed description of non-limiting an exemplary embodiments thereof, with reference to the following drawings.

Identical or duplicate or equivalent or similar structures, elements, or parts that appear in more than one drawing are generally labeled with the same reference numeral. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale or true perspective. For clarity, some structures are not shown or shown only partially, or without perspective, and duplicate or equivalent or similar parts may not be repeatedly labeled.

Fig. 1 is a schematic view of an embodiment of a solar energy system in accordance with the present invention;

Fig. 2 is a schematic isometric view of a solar collector for use in the of the present solar energy system; and

Fig. 3 is a schematic of an exemplary control system for the present solar energy system. DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The following description relates to some non-limiting examples of embodiments of the invention.

Fig. 1 shows a schematic representation of an embodiment of the present solar energy system. The system includes a solar collector, such as a flat-plate solar collector 10; a generator 12 having a push-pull motor 14; and a condenser tank 16, the aforementioned components connected by fluid carrying piping 18. Motor 14 has a piston 20 with a crank shaft 22. Push-pull motor 14 also has associated therewith a gas suction or inlet valve 24 and outlet valve 26 for delivery and exhaust of heat transfer fluid, respectively.

In other embodiments, the present system can derive thermal energy from "waste" heat (bottoming cycle) and therefore either not include solar collector 10, else be designed to receive thermal energy form both or either the solar collector or waste energy source (not shown).

The system also includes a heat transfer fluid temperature control unit or cooling unit 28 (exemplified by a ventilator); a one-way valve 30; a pressure relief valve 32; a pressure sensor 34 at the outlet of the solar collector 10; a starter 36 for motor 14; and a control system (detailed below).

Fig. 2 schematically illustrates the flat-plate solar collector 10, which is a vacuum-type collector, which comprises thin-gauge diameter collector tubes 45; and an entrance 46 and exit 48. As a result of the use of thin- gauge diameter collector tubes 45, there is a relatively high ratio of solar radiation (calories) on the collector 10 to quantity of fluid in the collector, providing an effect similar to a concentrating collector (e.g. parabolic collector). Fig. 3 schematically illustrates an exemplary control system fed from a power supply having a voltage and current directly received from a battery 40 electrically connected to a UPS 42 and the electrical mains 44.

The control system can be adapted to control or receive a signal from the following components: one or both of the motor's inlet and outlet valves 24, 26; cooling unit 28; pressure sensor 34; and starter 36.

Operation:

Heat transfer fluid flows through the system, i.e. through piping 18 including into solar collector 10 where the heat transfer fluid (e.g. water), entering in the liquid phase, is vaporized to gas (e.g. steam). When the fluid reaches the required pressure, pressure sensor 34 signals starter 36 to start motor 14 and fluid (gas/steam) enters the motor via inlet valve 24. Pressurized fluid pushes piston 20 to begin power generation (typically electrical energy). For ease of description, the movement of piston 20 will be referred to as "downward" during the aforementioned step, however, it should be understood that the actual direction of piston movement depends on the orientation of the motor 14 (the opposite and analogous being true for the upward stroke of the piston). This downward movement moves crank shaft 22 to produce power.

When piston 20 reaches the lowest level (one step/stroke) suction valve 24 closes, and the rotating crank 22, moving continuously in a circular path (inertial circle), moves/starts the piston upward (second step/stroke) and the fluid is released (pumped out) though outlet valve 26. The upward movement of crank 22 is aided by the pressure drop (suction) as a result of gas condensing in condenser tank 16.

Fluid (gas) exiting the motor 14 is received and condensed in condenser tank 16. The upward motion of the piston is aided by the inertia of the rotating crank and the suction/contraction of condensing fluid in condenser tank 16. The fluid (gas) cools and condenses in condensation tank 16, lowering the fluid pressure thereby opening, or at least aiding in the opening of, outlet valve 26 of generator 12.

The above activity repeats aided by the pressure differences or changes at the inlet valve 24 and outlet valve 26 of motor 14 during its alternating movement.

The generator 12 can produce one-phase, or more, electrical power with corresponding voltage and current.

In preferred embodiments, the system further includes a cooling unit 28 which is actuated to cool the fluid when the fluid temperature exiting the condenser tank 16 exceeds a pre-determined temperature (e.g. 110 degrees Celsius). The temperature in condenser tank 16 is preferably kept at or above 110 degrees Celsius in order to preserve the latent heat and to remain at a relationship of relatively high pressure to temperature. Thus the system operates on pressure differences above the latent heat temperature.

In particular embodiments, in place of, or in addition to, the cooling unit 28, the system may include another means to prevent fluid overheating, for example a means to direct solar collector 10 so as to absorb less solar radiation.

In particular embodiments, the system further includes an auxiliary hot water tank, or the like (not shown), disposed between the condenser tank 16 and cooling unit 28. Such water tank can be useful for controlling the fluid temperature and/or taking advantage of particularly hot fluid circulating in the system.

A closed loop solar energy system in accordance with the present invention was built with the following specifications: a 15 cc generator with thin gauge solar collector tubes of 1 mm inner diameter and having a 2.5 square meter surface area (25 cc fluid), with a resultant capacity of 1.2 kW at a pressure difference of 3.4 atmospheres, using steam as the working fluid, at the condition when the temperature of the steam exiting the collector and entering the generator was 141 degrees Celsius. It should be noted that other working fluids can be used, for example alcohol.

The present invention has been described using descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise various features, not all of which are necessarily required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of the features. Alternatively and additionally, portions of the invention described/depicted as a single unit may reside in two or more separate physical entities which act in concert to perform the described/depicted function. Alternatively and additionally, portions of the invention described/depicted as two or more separate physical entities may be integrated into a single physical entity to perform the described/depicted function. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments can be combined in all possible combinations including, but not limited to use of features described in the context of one embodiment in the context of any other embodiment.

Claims

1. A solar energy system comprising: a solar collector for vaporizing a heat transfer fluid; an electrical generator downstream said solar collector and including a push-pull motor having a fluid inlet valve and outlet valve; a piston and crank shaft; a condenser tank downstream of said electric generator; a heat transfer fluid temperature control unit; piping within which the heat transfer fluid is transported; a pressure sensor disposed between the solar collector and generator; and a control system, wherein the solar collector comprises one or more low-diameter collector tubes with an inner-diameter on the order of millimeters; and the generator is designed so that the inertia produced by the crank shaft and/or the pressure decrease in the system's piping due to condensation downstream of the generator aids the movement of the piston.

2. The system according to claim 1, wherein the tube's inner diameter is about 1 millimeter.

3. The system according to claim 1, wherein the solar collector is a vacuum-type solar collector.

4. The system according to claim 1, further comprising a starter associated with the motor.

5. The system according to claim 1, wherein the solar collector is a flat- plate collector.

6. The system according to claim 1, wherein the solar collector is a solar concentrating collector.

7. The system according to claim 1, further comprising an auxiliary hot water tank.

8. The system according to claim 1, wherein the working fluid in the pipes is water.

9. The system according to claim 1, wherein the working fluid in the pipes is alcohol.

10. The system according to claim 1, operated at pressure differences above the latent heat temperature.