GB1602434A

GB1602434A - Solar heat collectors

Info

Publication number: GB1602434A
Application number: GB1062/77A
Authority: GB
Original assignee: Michaelis J D
Current assignee: Michaelis J D
Priority date: 1978-04-11
Filing date: 1978-04-11
Publication date: 1981-11-11

Description

(54) IMPROVEMENTS IN OR RELATING TO SOLAR HEAT COLLECTORS (71) I, JOHN DOMINIC MICHAELIS, a British Subject, of Bay 8, 16 South Wharf Road, London W2 lPF, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to solar heat collectors.

Solar heat collectors of generally flat form have been known and used for some time, but involve various disadvantages due to the low concentration of energy collected. Parabolic concentrators have been used to achieve concentration, but have the disadvantage of the need to track the sun bodily, which requires expensive moving gear. Stationary reflectors with tracking absorbers (SRTA) have been proposed, but have generally proved to be too costly to build using conventional construction methods.

It is one object of the present invention to provide a relatively simple and inexpensive form of solar collector, the concept of the invention being applicable to SRTA and other forms of solar collectors.

According to the present invention, there is provided a solar heat collector comprising an envelope having a lower part of partspherical or parabolic form provided with a reflective concave face, and an upper part which is translucent, and also comprising an absorber disposed within said envelope to receive energy reflected from said face.

Suitably, said envelope is inflatable and, said lower part comprises a mirrorised membrane of part-spherical form and said absorber comprises a linear absorber pivotally mounted to track the sun. In this case, the sun's rays penetrating into the inflated structure are reflected onto a line which is parallel to the sun's rays. The linear absorber, at this position, intercepts the reflected rays and pivots about a point at the summit of the upper part so that the axis of the absorber is parallel to the incoming radiation.

Alternatively, said lower part may be a membrane of parabolic form and said absorber is arranged to move with the reflector.

It will be appreciated that the upper translucent membrane protects the delicate mirrorised surface from dust, rain, hail and wind, and the collector can be arranged so that at least the lower membrane is protected by the ground around the site of the collector.

The whole assembly can be tilted to act efficiently at different latitudes, the mirror axis always being orientated due south in northern latitudes.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view of one form of a solar collector according to the present invention; Figure 2 is a sectional view on the line II--II of Figure 1; Figure 3 is a diagrammatic sectional elevation showing another form of solar collector according to the invention; Figure 4 is a plan view of a solar collecting roof according to the invention; Figure 5 is a section on the line V-V of Figure 4; and, Figure 6 is a detail section on the line V-V of Figure 4.

Referring to Figures 1 and 2 of the drawings, the solar collector comprises a lower part-spherical reflector 1 and a transparent upper cover 2, which are linked by a rigid circular ring beam 3 to form a closed envelope. The beam 3 acts as a tie ring when pressurised air fills the space between the reflector and the cover which are formed as membranes or skins of suitable plastics material. Air inlets 4 are provided around the ring beam 3 to allow air to be blown into the space from a fan 5, and the air pressure is such as to stabilise the upper and lower membranes against deformation due to wind, variations in temperature, etc.

The reflector is straddled by a lattice structure 6 of space-frame construction which provides a minimum of overshadowing. At its summit, the structure supports a connection cone 7 which is capable of taking the crown compression and tension forces involved, and the upper cover 2 is connected to the lower end of the cone. A pivot support 8 is carried at the top of the cone 7 to lie directly above the centre of the reflector 1.

A service platform 10 is mounted above the cone 7. A directional control mechanism 9 comprising three telescopic legs is based on the platform 10 to act on the shorter end of a boom 12 which pivots about the support 8 and is counterweighted, as necessary, by a suitable mass or by the weight of a turboalternator l l or other type of generator or power transformer.

An absorber 13 is provided at the lower end of the boom 12 so that, when the boom is parallel to the source of solar radiation (the sun), all radiation falling on the metallised reflector surface is directed to the absorber.

Heat from the absorber 13 is transferred through the boom to operate the turbogenerator 11 or to be fed to a heat storing device.

The ring beam 3 which holds the inflated collector, is supported by a continuous ring platform 17 mounted on a foundation assembly 16. The ring platform 17 receives drainage from the upper membrane 2, the water being collected and, if required, stored for possible use in a cooling cycle having cooling towers and water tanks 21.

As shown in Figure 2, a dish has been excavated, the excavated surface 15 being stabilised and provided with a drained or pumped sump 14 at its base. The excavated earth is used to form a bank 18 which provides protection against wind, and trees 19 planted on the bank can offer an additional wind and dust barrier.

Electric power derived from the collector and generated by the generator 11 can be fed through cables carried by the lattice structure 6 and led off at a suitable connection point to pylon-supported power cables 20. Alternatively, a heat pipe may be employed to transfer heat from the absorber to flow pipes leading to a working fluid. The heat pipe may be flexible or flexibly jointed to allow tracking without moving joints which could be susceptible to leakage. Movement of the boom carrying the absorber may be effected through an independent tracking system mounted at the pivot.

The lattice structure 6 can also act to support an access route for equipment to and from the platform 10.

In a development of the invention, the inflated collector can be tilted in the support structure to achieve better solar collection during winter in higher latitudes.

Because of its light weight, the collector could, if produced to a smaller scale than that illustrated in Figures 1 and 2, be incorporated into the structure of a building.

The inflated collector membranes may be arranged to be folded and packed, and the structure may be readily dismantled. Thus, in larger applications prefabrication and transport may be simplified, and in smaller applications portable units may be constructed.

Referring now to Figure 3, an inner envelope 30 has a lower reflector 31 of parabolic section and this envelope is pivotally arranged within an outer spherical inflated envelope 32 formed of transparent plastics material. This arrangement is possible because of the relatively light weight of the membranes.

The inner envelope 30 is inflated to a pressure slightly higher than that in the surrounding envelope 32, and is formed of a mirrorised parabolic membrane to provide reflector 31 and a clear upper membrane 33.

The two membranes are interconnected and supported along their edges by an inner ring beam 34.

The inner ring beam 34 is provided with two pivots 35 at diametrically opposed edges to allow the inner inflated assembly to pivot.

At its focus is a punctual absorber 36 which is linked to an electric generator or other power generating device 37, or to an external heat using or storing device.

Since the inner assembly is required to track the sun, the pivots 35 are arranged to be moved along an outer ring beam 38 to allow the plane of the inner ring beam 34 to remain perpendicular to solar radiation. The outer ring beam 38 supports the optional outer envelope 32 which protects the inner structure from wind, rain, dust, etc. The whole assembly is raised as before from the ground and held by support structures 39.

Because of the punctual concentration achieved by the collector illustrated in Figure 3, much higher temperatures can be achieved than with linear absorbers such as are illustrated in Figure 1.

In both the type of solar collector described, thin shell structures might be employed instead of inflatable envelopes, although, in this modification of the invention, the whole assembly would be much heavier.

The advantage of using inflatables is the light weight and consequent economy of material that can be achieved, both in the membranes themselves and in the support structures.

However, thin shell structures would be much lighter than concrete structures, and could act without supplementary internal pressure being applied. For their stiffness, the thin shell structures would rely on stressed skin formations.

In a further alternative, an external lightweight geodetic structure could be used to support the reflective and transparent membranes.

In Figures 4, 5 and 6, there is described a solar collector assembly which, because of the light weight of the components, can be incorporated in or form a weathertight roof structure of, for example, a factory. Light to the covered space below can pass between the hemispherical reflectors which can be inclined as necessary to suit the latitude of the site. By using the collectors as a roof, valuable covered space can be provided, which can usefully contribute to the economic viability of the solar collecting area.

Figure 4 shows a solar collecting roof which provides energy for a central generating plant 41, with flow and return pipework 42serving individual collectors 43.

Figure 5 illustrates the manner in which the roof-mounted collectors 43 are assembled to form the covering over a climatised zone 44 which can be used for industrial or agricultural purposes. Energy is supplied to a thermal store 45 to carry over provision of heat during night time or sunless periods and, in this embodiment, a steam turbine 46 is provided.

Figure 6 shows details of a single collector 43. A ring beam 47 is supported by columns 48, and upper transparent membrane 49 and lower reflective membrane 50 are attached to the beam. The flow and return pipes 42 feed the working fluid through a two-way pivot 51 to and from a linear absorber 52 where solar energy is collected. The location of the absorber is controlled by motors 53 which are mounted on the ring beam 47 and operate through cables 54 attached to the base of the absorber which is mounted at the lower end of a boom 55. Alternatively, the boom may be controlled by forces applied near the pivot point, either hydraulically or mechanically.

In a further modification, the reflector and cover form a total sphere, the upper half being transparent and the lower half reflective. The energy absorber would be located at the centre of the sphere, and the orientation of the hemispherical reflector may be varied without any bodily movement of the suppport structure.

In another modification of the invention, the booms may carry photo-voltaic cells to produce electricity directly.

WHAT I CLAIM IS: 1. A solar heat collector comprising an envelope having a lower part of part-spherical or parabolic form provided with a reflective concave face, and an upper part which is translucent, and also comprising an absorber disposed within said envelope to receive energy reflected from said face.

2. A solar heat collector according to Claim 1, in which said absorber is mounted at the lower end of a pivotally mounted boom.

3. A solar heat collector according to Claim 2, in which said absorber is a linear absorber and said lower part is of partspherical form.

4. A solar heat collector according to Claim 1 or Claim 2, in which said absorber is a punctual absorber and said lower part is of parabolic form.

5. A solar heat collector according to any preceding Claim, and further comprising a surrounding protective envelope which is translucent at least in its upper part.

6. A solar heat collector according to any preceding Claim, in which the first-mentioned envelope is inflated.

7. A solar heat collector according to Claim 6, in which said lower part comprises a mirrorised membrane.

8. A solar heat collector according Claim 6 or Claim 7, in which said upper part comprises a transparent membrane.

9. A solar heat collector according to Claims 7 and 8, in which said membranes are linked by a circular supporting beam.

10. A solar heat collector according to any of Claims 1 to 5, in which said lower and upper parts comprise thin shell structures.

11. A solar heat collector, substantially as hereinbefore described with reference to Figures 1 and 2, or Figure 3 of the accompanying drawings.

12. A solar heat collecting installation comprising a series of collectors as claimed in any preceding Claim and arranged to form a roof structure.

13. A solar heat collecting roof, substantially as hereinbefore described with reference to Figures 4 to 6 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. incorporated in or form a weathertight roof structure of, for example, a factory. Light to the covered space below can pass between the hemispherical reflectors which can be inclined as necessary to suit the latitude of the site. By using the collectors as a roof, valuable covered space can be provided, which can usefully contribute to the economic viability of the solar collecting area. Figure 4 shows a solar collecting roof which provides energy for a central generating plant 41, with flow and return pipework 42serving individual collectors 43. Figure 5 illustrates the manner in which the roof-mounted collectors 43 are assembled to form the covering over a climatised zone 44 which can be used for industrial or agricultural purposes. Energy is supplied to a thermal store 45 to carry over provision of heat during night time or sunless periods and, in this embodiment, a steam turbine 46 is provided. Figure 6 shows details of a single collector 43. A ring beam 47 is supported by columns 48, and upper transparent membrane 49 and lower reflective membrane 50 are attached to the beam. The flow and return pipes 42 feed the working fluid through a two-way pivot 51 to and from a linear absorber 52 where solar energy is collected. The location of the absorber is controlled by motors 53 which are mounted on the ring beam 47 and operate through cables 54 attached to the base of the absorber which is mounted at the lower end of a boom 55. Alternatively, the boom may be controlled by forces applied near the pivot point, either hydraulically or mechanically. In a further modification, the reflector and cover form a total sphere, the upper half being transparent and the lower half reflective. The energy absorber would be located at the centre of the sphere, and the orientation of the hemispherical reflector may be varied without any bodily movement of the suppport structure. In another modification of the invention, the booms may carry photo-voltaic cells to produce electricity directly. WHAT I CLAIM IS:

1. A solar heat collector comprising an envelope having a lower part of part-spherical or parabolic form provided with a reflective concave face, and an upper part which is translucent, and also comprising an absorber disposed within said envelope to receive energy reflected from said face.