AU6580294A

AU6580294A - Solar dish concentrator coupled to power generator

Info

Publication number: AU6580294A
Application number: AU65802/94A
Authority: AU
Inventors: Daya Ranjit Senanayake
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-05-11
Filing date: 1994-05-09
Publication date: 1994-12-12
Also published as: CN1127035A; DE4493139T1; WO1994027096A3; WO1994027096A2; ZA943198B; IS4160A

Description

SOLAR DISH CONCENTRATOR COUPLED TO POWER GENERATOR

FIELD OF THE INVENTION

This invention relates to the coupling of a solar dish concentrator to a power generator.

BACKGROUND TO THE INVENTION

Solar disc concentrators need to be raised from the ground and to be mounted to track the sun. The solar energy captured by a concentrator is continuously directed to a reception point, there to be used for instance for driving a Rankine cycle engine (for electrical power generation).

One of the current problems with solar dish concentrators is to find a suitable means of converting the concentrated solar rays into useful electrical power, including the further problem of transporting and storing the medium heated by the concentrated solar rays in a manner to minimising losses.

The invention has particular application to the generation of power by a Rankine binary cycle turbine. DESCRIPTION OF THE PRIOR ART

A solar powered Rankine Cycle Pumping Engine is disclosed in US Patent 4,103,493. The solar heat is received by collector, which however does not track the sun. There is no storage of surplus heat, nor therefore attempted equalisation between periods of surplus and shortfall.

A solar powered Rankine Cycle Pumping Engine is disclosed in US Patent 4,765,144. The solar energy is however received by a planar collector of limited dimensions; though the collector is mounted on a solar tracker, it has flexible fluid lines to and from the collector, which may not withstand the higher medium temperatures required for effective engine operation.

STATEMENT OF THE INVENTION

We provide an energy conversion assembly which includes a solar dish concentrator having a focal point, means to move the concentrator whereby to track the sun, absorbtion means to absorb solar energy, said absorbtion means being at said focal point characterised by a power generator, by fluid conduit means connecting the absorbtion means and the generator, and by at least one flexible joint in said fluid conduit means.

Thus the conduit means can be rigid (except for the joint or joints) and so better able to withstand the higher fluid temperatures to be used in the invention.

Furthermore the conduit means can be co-axial, with an inner conduit for the hotter fluid passing towards the engine and an outer encircling conduit for the cooler returning fluid. Thus the fluid is retained in a closed cycle.

A storage reservoir comprising an inner hot chamber and a cooler outer chamber can also be provided.

Each rotating or flexible joint can be surrounded by a flexible cover, filled with cool operating fluid, under pressure.

Preferably the power generator is a Rankine binary cycle turbine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described, by way of example, with reference to the accompanying drawings, in which:-

Fig.l shows a solar dish concentrator coupled to a Rankine binary cycle turbine power generator according to the invention; and

Fig.2 is a sectional view of a heat recovery pipe and rotating joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The solar dish 1 is known energy concentrator, which collects and concentrates solar rays to a receiver 2 fixedly mounted at the focal point of the concentrator 1.

A Rankine binary cycle power generator or engine 14 is positioned adjacent to the solar dish 1.

An insulated cross-flow heat recovery system according to the invention is connected between the receiver 2 and the engine 14.

A heat recovery pipe 3 is fixed at its one end to the receiver 2, and at its other (exit) end is fixed to a part of a rotating joint 4. The entire rotating joint 4 is enclosed in a flexible cover 5.

The rotating joint 4 is connected to one end of a second section of heat recovery pipe 6. The other end of the heat recovery pipe 6 is connected to a second rotating joint 7.

Rotating joint 7 is enclosed in a flexible cover 8.

Rotating joint 7 is connected to one end of a third heat recovery pipe 9. The other (exit) end of the pipe 9 is connected to a third rotating joint 10.

Rotating joint 10 is enclosed in a flexible cover 11.

The third rotating joint 10 is connected to a heat recovery storage tank 12.

A fourth heat recovery pipe 13 connects the heat recovery storage tank 12 to the inlet of the Rankine binary cycle turbine 14.

In operation, the receiver 2 contains a fluid which becomes heated by the solar rays concentrated to focal point on the receiver. The heated fluid flows through the inner core or conduit 20 of the heat recovery pipes 3,6,9 and 13 (which are insulated) and so (by way of inner chamber 16 of intermediate or storage unit 12) to the heat exchange unit of the Rankine binary cycle turbine 14, where the heated fluid (or energy transporting medium) imparts its heat.

After effecting energy transfer in known manner at turbine 14, the working fluid (now cooled) flows back through the outer conduit 22 of heat recovery pipe 13, to the heat recovery storage tank 12.

Storage tank 12 includes not only of the inner chamber or core 16 which is well insulated, and holds "on call" for the turbine 14 the hot fluid arriving from the receiver 2, but also has an outer chamber 17 which holds "on call" cooled fluid flowing back from the Rankine binary cycle turbine 14 through the outer conduit of heat recovery pipe 13. Chambers 16, 17 are insulated from each other and from the surrounding atmosphere.

The cooled fluid in the outer chamber(s) 17 of the heat recovery storage tank 12 is pumped back to the receiver 2 as required, through the outer cores or conduits of co¬ axial heat recovery pipes 9,6 and 3, to be reheated by the concentrator 1, completing a cycle.

The flow arrangement for the cooled fluid (through the outer core of the heat recovery pipes 3,6,9 and 13) ensures that any heat loss from the hot fluid located therewithin is recovered largely by the returning cooled fluid; furthermore as the pipes are insulated to the outside the heat loss from the system to the atmosphere is minimised.

The flexible covers 5,8 and 11 also transmit cooled fluid to the outside and the hot fluid to the inside, also to utilise heat losses from the hotter fluid.

The rotating joints 4,7 and 10 permit flexible movement of the pipes as the receiver 2 and the concentrator 1 move in tracking the sun.

The heat recovery storage tank 12 permits the collection and storage of hot fluids from e.g. three solar dish concentrators, so that the power production of the system can perhaps operate effectively for 24 hours with a sunshine period of perhaps only 8 hours per day.

The main advantages and unique features of this invention are :-

(a) high temperature heat generated at the receiver 2, can be transferred, handled and stored without serious heat losses because of the "heat recovery" pipe designs, the counter-flow arrangement, and the design of the heat recovery storage tank. {b} the required movement of the receiver 2 can be accommodated by using a system incorporating one or more rotating joints. These joints are also encased, as with the heat recovery system, to minimise thermal losses to the outside.

{c} the coupling of the solar dish concentrator 1 to the Rankine binary cycle turbine permits the use of a range of temperatures for the working fluid in the range 80° to 400°» and enables the use of one or more heat sources to maintain power output.

{d} modular units each of approximately 1 megawatt can be set up, and expanded in modules to create 100 megawatt installations, or more.

(e) flexible cover 5 provides an extra seal for the rotating joint; the flexible cover is insulated and pressurised with the same fluid and clamped/sealed in place. In this embodiment the pressure of the fluid in the flexible cover 5 is maintained at a slightly higher pressure than the pressure of the fluid in the outer core of heat recovery pipe 3,6,9 and 13 (to prevent any leaks from the pipes). In other embodiments, other types of turbines, rather than Rankine binary cycle turbines, may be used.

Various types of heat-resistant materials and of insulated pipes can be used.

One or more different embodiments of rotating and flexible joints may be used, including labyrinth joints and graphite discs and bearings.

Claims

1. An energy conversion assembly which includes a solar dish concentrator having a focal point, means to move the concentrator whereby to track the sun, absorbtion means to absorb solar energy, said absorbtion means being at said focal point characterised by a power generator, by fluid conduit means connecting the absorbtion means and the generator, and by at least one flexible joint in said fluid conduit means.

2. An energy conversion assembly according to Claim 1 characterised in that the power generator is a Rankine binary cycle turbine.

3. An energy conversion assembly according to Claim 1 characterised in that the fluid conduit means comprises at least one rigid tube and two flexible joints, said joints being connected one to each end of the tube.

4. An energy conversion assembly according to Claim 3 characterised in that the flexible joints are rotatable.

5. An energy conversion assembly according to Claim 1 characterised in that the fluid conduit means comprises at least one tube having two separated passageways, one passageway being for fluid flow towards the generator, the other passageway being for fluid flow from the generator, and in that the said one passageway is within the said other passageway.

6. An energy conversion assembly according to Claim 1 characterised in that the fluid conduit means includes a a first dwell chamber and a second dwell chamber, the first dwell chamber being in the flow path to the generator, the second dwell chamber being in the flow path from the generator.

7. An energy conversion assembly according to Claim 6 characterised in that the first dwell chamber is within the second dwell chamber and in that the first dwell chamber is insulated to inhibit heat transfer between the chambers and in that the second dwell chamber is insulated to inhibit heat loss from the second dwell chamber to the outside air.

8. An energy conversion assembly according to Claim 1 characterised in that said absorbtion means is a container for a liquid working medium.

9. An energy conversion assembly according to Claim 1 characterised in that the fluid conduit means includes a heat recovery pipe having one end fixed to the absorbtion or solar ray receiving means and its other end to a first joint, in that a second pipe has its one end connected to the first joint and its other end to a second joint, in that a third pipe has its one end connected to the second joint and its other end connected to a third joint, and in that a fourth pipe has its one end connected to the third joint and its fourth end connected to a dwell chamber; and in that a fifth pipe has its one end connected to a dwell chamber and its other end to the power generator.

10. An energy conversion assembly according to Claim 9 characterised in that each of said joints is enclosed in a flexible cover, in that each said cover is impervious to the working fluid, and in that each said cover contains working fluid under pressure.