WO2012034173A1

WO2012034173A1 - Solar energy plant

Info

Publication number: WO2012034173A1
Application number: PCT/AU2011/001180
Authority: WO
Inventors: Geoffrey Andrew Kinghorn; Nicholas Jordon Bain
Original assignee: Graphite Energy NV
Current assignee: Graphite Energy NV
Priority date: 2010-09-17
Filing date: 2011-09-14
Publication date: 2012-03-22
Anticipated expiration: 2013-03-17

Abstract

This invention concerns a solar energy plant, for generating electrical energy from solar energy via the intermediary of heat energy storage in graphite. It comprises an array of solar tracking dish concentrators, each of which has a heat storage device mounted at its focal point to receive reflected solar heat. Each heat storage device has an inbuilt heat exchanger in fluid communication with a heat transfer circuit that extends through the superstructure of the respective dish concentrator to receive cold water from a feed source off-dish, and deliver heated fluid from the heat storage device to an off-dish heat transfer network of pipes. The off-dish heat transfer network receives heated fluid from each heat storage device at respective inlets, and also comprises plural switchable nodes that are operated to configure and reconfigure the flow paths of the heated fluid through the network pipes before delivering it to one or more heat consuming engines or processes via respective outlets.

Description

Title

Solar Energy Plant

Technical Field

This invention concerns a solar energy plant, for generating electrical energy from solar energy via the intermediary of heat energy storage in graphite.

Background Art

Solar energy is received during the daylight hours, and it is variable during daytime, depending on the weather conditions. As a result it is desirable to include energy storage capacity in-circuit between the solar collector and the energy consumer to set and regulate to energy output. Graphite has been found to be a useful medium to store heat energy for such circuits.

Disclosure of the Invention

The invention is currently envisaged as a solar energy plant, comprising an array of solar tracking dish concentrators, each of which has a heat storage device mounted at its focal point to receive reflected solar heat.

Wherein each heat storage device has an inbuilt heat exchanger in fluid communication with a heat transfer circuit that extends through the superstructure of the respective dish concentrator to receive cold water from a feed source off-dish, and deliver heated fluid from the heat storage device to an off-dish heat transfer network of pipes.

Wherein, the off-dish heat transfer network receives heated fluid from each heat storage device at respective inlets, and also comprises plural switchable nodes that are operated to configure and reconfigure the flow paths of the heated fluid through the network pipes before delivering it to one or more heat consuming engines or processes via respective outlets.

The plant further comprising a control system to operate the switchable nodes to control the temperature of the heated fluid being delivered at the outlets to respective energy consuming engines or processes. The heat storage devices may be graphite blocks. Typically the blocks are made up of a stack of smaller bricks and the heat exchanger comprises a network of pipes that extend through channels formed in the surface of the bricks. The pipes are typically stainless steel.

By operating the system appropriately, a large amount of solar energy may be captured and stored as heat energy in the graphite blocks, and then that heat energy may be tapped from the blocks and delivered at a precisely controlled temperature and flow rate to an energy consuming engine or process; for instance to generate electricity.

The solar tracking dish concentrators may be of the type with multiple ground engaging supports. One of these typically engages the ground at the origin of a circle, and the others ride around a circular path so that the entire dish revolves around the origin to track the sun.

The graphite blocks may be mounted at the focal point of the dish reflectors at the apex of a superstructure standing above the face of the dish. The heat transfer circuit extends through the superstructure to deliver water to the graphite block and remove superheated steam from it. The water may be delivered and the steam removed via respective manifolds at, or near to, the origin of the circular track. For instance via vertically arranged pipes that interconnect with toroidal manifolds connected to the heat transfer pipes. In this way water can enter the graphite block, and steam can be withdrawn, while the dish is tracking the sun. The steam is received off-dish in a network of pipes that may extend throughout the area covered by the solar energy plant; which could be many square kilometers. The network of pipes ends at one or more outlets where heat consuming engines or processes are driven. They may, for instance, be driven to convert the heat to other energy forms, such as electricity. The entire solar plant may drive a single steam turbine, or many smaller turbines, that could be distributed through the field.

The network of pipes that make up the heat transfer network includes an array of switchable nodes that control the mixing of the superheated steam before delivery to the one or more outlets. The mixing enables control of the temperature and pressure of the delivered steam. Cooler steam may be mixed with hotter steam in proportion to the desired resulting temperature. This makes best use of different temperatures in the steam at different locations in the plant. For instance, at night when no energy is being collected from the sun, the entire plant may be cooled by extracting heat from one region and then another. As the temperatures reduces in one region the output steam temperature (which may be as reduced to 100°C in the case of saturated steam) may be increased by blending it with super-heated steam from a hotter region.

The network may also include secondary heat storage devices at various locations within the network; for instance at the network nodes. This provides greater thermal mass to the network, and therefore greater stability in the output temperature.

A sophisticated computer operated control system may be used to automatically control the switchable nodes to produce the desired output steam temperature and pressure. The control system may collect real-time readings of temperature and pressure from a network of sensors throughout the network, in order to effect proper control.

Brief Description of the Drawings

An example of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a plan view of a solar energy plant.

Fig. 2 is a schematic view of a heat storage device.

Best Modes of the Invention Referring first to Fig. 1 the solar energy plant 10 comprises an array of solar tracking dish concentrators 12, each of which has a graphite heat storage device 14 mounted at its focal point to receive reflected solar heat. The solar tracking dish concentrators 12 are of the type with multiple ground supports. One of these engages the ground at the origin of a circle 16, and the others ride along the path of the circle 18 so that the entire dish revolves around the origin 16 to track the sun.

Referring also to Fig. 2, each heat storage device 14 comprises a large block of graphite 20 surrounded by cladding 22. Each block 14 has a heat exchanger 24 embedded within it. The graphite block 20 is insolated by the suns rays 2, after reflection off the dish 12 via an aperture 26 in the cladding 24, which opens into a cavity 28 in the underside of the graphite block 20. Heat exchanger 24 is in fluid communication with a heat transfer circuit 30 that extends through the superstructure 32 of the respective dish concentrator 12 to receive cold water 34 from a feed pond 38, and deliver super-heated steam 36 from the heat storage device 14 to a heat transfer network of pipes 40.

The heat transfer network 40 receives the super-heated steam from each heat storage device 14 at respective inlets 42. From the inlets 42 the network 40 comprises stainless steel pipes 44 interconnected by controllable switchable nodes 46 which enable selective flow downstream through network 40 to the load 50. The plant also comprises a control system 60 to operate the switchable nodes 46 to control the temperature and pressure of the super-heated steam being delivered at the outlets to respective energy consuming engines or processes. For example, taking switchable node 140, this can be controlled so that the input is directed into none, or one or more of the pipes 142, 144 or 146. Also, this node 140 could receive input from any combination of pipes 138, 142, 144 and 146 (but it cannot receive input and send output down the same pipe at the same time). The nodes can however be switched from time to time, or at regular synchronized intervals, in order to reconfigure part, or parts, or the entire network 40.

In the example shown, the entire network 40 feeds superheated steam at a controlled temperature and pressure to a single turbine 50 that is used to generate electricity. The water is delivered and the steam removed via respective manifolds at, or near to, the origin 16 of the circular track 18. As shown in Fig. 2, a feedpipe from reservoir 38 comprises a ring-shaped rising main that encircles origin 16. From this main cold water 34 can flow up through the dish superstructure 32 to the graphite block 14; regardless of the orientation or movement of the dish 12.

At the apex of the superstructure 32 the cold water 34 flows into the heat storage device 14. Here it passes through the cladding 22 and into the heat exchange circuit 24 embedded in the graphite. In passing through the heat exchanger 24 the cold water is heated and converted to super-heated steam if the graphite has stored enough heat. The super-heated steam 36 passes out of the heat storage device in pipes that travel back through the superstructure 32 to the dish. The steam is collected in a toroidal manifold 38 that feeds downward through the origin 16 of the dish and enters the network 40.

The network of pipes 40 may also include secondary heat storage devices 120 at various locations within the network to provide greater thermal mass, and therefore stability in the output temperature.

A sophisticated computer operated control system 60 provides control signals to the switchable nodes to produce the desired output temperature and pressure. To do this the control system collects real-time readings of temperature and pressure 130 from sensors 132 embedded at the switchable nodes 46 of the network 40.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A solar energy dish and storage plant, comprising an array of solar tracking dish concentrators, each of which has a heat storage device mounted at its focal point to receive reflected solar heat;

wherein each heat storage device has an inbuilt heat exchanger in fluid communication with a heat transfer circuit that extends through the superstructure of the respective dish concentrator to receive cool heat transfer fluid from a feed source off-dish, and deliver heated fluid from the heat storage device to an off-dish heat transfer network of pipes;

wherein, the off-dish heat transfer network receives heated fluid from each heat storage device at respective inlets, and also comprises plural switchable nodes that are operated to configure and reconfigure the flow paths of the heated fluid through the network before delivering it to one or more heat consuming engines or processes via respective outlets.

the plant further comprising a control system to operate the switchable nodes to control the temperature of the heated fluid being delivered at the outlets to respective energy consuming engines or processes.

2. A solar energy dish and storage plant according to claim 1, further comprising means whereby the tilt of the dish can be changed to track the rise and fall of the sun in the sky during the day.

3. A solar energy dish and storage plant according to claim 1, wherein the heat storage devices are graphite block receivers.

4. A solar energy dish and storage plant according to claim 1, wherein the heat exchanger comprises a network of pipes that extend through channels formed on the surface and in the body of the graphite receiver.

5. A solar energy dish and storage plant according to claim 4, wherein the pipes are appropriate for a carbon rich high temperature environment

6. A solar energy dish and storage plant according to claim 1, wherein each storage device is mounted at the focal point of a respective dish reflector at the apex of a superstructure standing above the face of the dish.

7. A solar energy dish and storage plant according to claim 6, wherein each heat transfer circuit extends through the superstructure to deliver cool heat transfer fluid to the storage device and remove heated fluid from it.

8. A solar energy dish and storage plant according to claim 7, wherein the vertical pipes are each connected to the heat transfer circuit extending through the superstructure of the dish via one or more flexible elbows involving ball joints or rotating unions.

9. A solar energy dish and storage plant according to claim 8, wherein the ball joints are able to rotate and flex.

10. A solar energy dish and storage plant according to claim 9, wherein the heated fluid is received off-dish in a network of pipes that extends throughout the area covered by the solar energy plant.

11. A solar energy dish and storage plant according to claim 10, wherein the network of pipes ends at one or more outlets where heat consuming engines or processes are driven.

12. A solar energy dish and storage plant according to claim 11, wherein heat consuming engines or processes are driven to convert the heat to electricity.

13. A solar energy dish and storage plant according to claim 12, wherein the entire solar plant drives a single Rankine cycle turbine.

14. A solar energy dish and storage plant according to claim 12, wherein the entire solar plant drives plural Rankine cycle turbines distributed through the plant.

15. A solar energy dish and storage plant according to claim 10, wherein the network of pipes includes an array of switchable nodes that control mixing of the heated fluid before delivery to the one or more outlets.

16. A solar energy dish and storage plant according to claim 15, further comprising a computer operated control system to automatically control the switchable nodes to produce the desired output steam temperature and pressure.

17. A solar energy dish and storage plant according to claim 16, wherein the control system also collects real-time readings of temperature and pressure from a network of sensors throughout the network.