Low cost solar energy extraction

• US 20040020528A1
• Filed: 03/22/2003
• Published: 02/05/2004
• Est. Priority Date: 04/01/2002
• Status: Active Grant

• Current Assignee: Niket Keshav Patwardhan
• Original Assignee: Niket Keshav Patwardhan
• Inventors: Patwardhan, Niket Keshav
• Granted Patent: US 7,481,057 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: F03G 6/04 gaseous F03G6/064, F03G6/068 take precedence
• CPC Class Codes: F24S 10/80 comprising porous material or permeable masses directly contacting the working fluids for conveying liquefied working fluid from evaporator sections to condenser sections with capillary force F24S10/95
• CPC Class Codes: F24S 20/69 in the form of shingles or tiles
• CPC Class Codes: F24S 40/00 Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors control arrangements F24S50/00
• CPC Class Codes: Y02B 10/20 Solar thermal
• CPC Class Codes: Y02E 10/44 Heat exchange systems
• CPC Class Codes: Y02E 10/46 Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines

Abstract

While solar energy is widely available, current means to harness it are sufficiently expensive that for most applications it is not economically viable. The basic problem is that solar energy is not sufficiently concentrated, and the cost of the collector becomes the limiting factor. This invention teaches a way of building a solar collector and an associated energy conversion engine that together allow one to build cost effective solar electric systems that can compete with natural gas based power plants.

Claims

1. A device called a solar collector to capture solar energy as heat and deliver hot air and comprised of:

a screen to block turbulence or wind from reaching the collector surface while allowing air and radiation to do so;

a collector surface that absorbs the solar radiation, and is separated from the screen by a gap;

holes in the collector surface through which the air heated by conduction from the collector surface may be drawn into the solar collector;

a spectrally selective coating on either the screen or the collector surface, or both, that reflects longer wave radiation, and that either absorbs shorter wave radiation in the case of the collector surface coating, or transmits shorter wave radiation in the case of a coating on the screen;

and an insulated enclosure under or behind the collector surface from which hot air may be drawn.

2. The device of claim 1 where:

the screen is made of glass roofing tiles;

the coating is transparent and on the underside of the glass tiles.

3. The device of claim 1 where:

the screen is made of glass roofing tiles and a film underneath the glass tiles with holes in the film;

the coating is transparent and on the underside of the film.

4. The device of claim 1 where:

the screen is a fine mesh;

the collector surface is aluminium plate or aluminium foil, with small holes in them, and coated with the opaque spectrally selective coating on the side facing the sun.

10. The device of claim 9 where:

the solar collector is the device of claim 1, 2, 3, or 4.

12. The device of claim 9 where:

the solar collector is the device of claim 1, 2, 3, or 4;

and the air engine is the device of claim 5, 6, 7, or 8.

5. A device to convert hot air into mechanical energy or compressed air called an air engine comprised of:

one or more nozzles to expand hot air and convert some of its heat energy into kinetic energy;

a mixing section into which the nozzles deliver the air;

a water injector that atomizes and sprays water through the mixing section at high velocity thus cooling the air with little relative motion between the air and water;

a diffuser that compresses the mixture at low pressure and with high kinetic energy back to the input pressure or above.

6. The device of claim 5:

which has a turbine that converts the remaining kinetic energy at the exit of the diffuser into rotational mechanical energy.

7. The device of claim 5 where:

the nozzles are arranged in a circle and oriented to produce a swirling air mass above the water injector;

the water injector is a spinning wheel onto which water is dropped, or in whose axle a small channel delivers water to the center of the wheel;

the mixing section is an annular gap in the enclosure for the wheel that is aligned with the water spray from the spinning wheel;

the motive force for the wheel is a small motor that drives the wheel.

8. The device of claim 7 where:

the spinning wheel and motor are dispensed with and replaced with an atomizer and pump that sprays water outward from the space that would have been occupied by the wheel.

11. The device of claim 9 where:

the air engine is the device of claim 5, 6, 7, or 8.

9. A device that converts solar energy into mechanical energy comprising of:

a solar collector that heats ambient pressure air;

and an engine that heats a fluid at constant pressure, expands it to near ambient temperature to convert the heat into work, and isothermally or near isothermally compresses it to restore it to the original pressure or above.