GB1585916A

GB1585916A - Solar energy collection and delivery

Info

Publication number: GB1585916A
Application number: GB31441/77A
Authority: GB
Original assignee: Vickers Ltd
Current assignee: Vickers Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-03-11

Description

(54) SOLAR ENERGY COLLECTION AND DELIVERY (71) We, VICKERS LIMITED, a British company, of -Vickers House, Millbank Tower, Millbank, London, SW1P 4RA, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to solar energy, and is concerned more particularly with the collection and delivery of solar energy to a point of application, and also with the utilisation of the energy.

According to the present invention there is provided apparatus for collecting solar energy and delivering collected energy to a point of application, comprising a solar radiation collector, for concentrating solar radiation onto a delivery input point of the apparatus, and an optical fibre bundle, having an input end mounted at the said delivery input point tto receive concentrated radiation for delivery to the point of application.

In a preferred embodiment of the present invention there is an array of solar radiation collection I concentrators, which collec tori concentrators comprise respective fresnel lenses for concentrating solar radiation onto input ends of respective optical fibre bundles, which bundles are brought together for delivering concentrated radiation to the said point of application.

Embodiments of the present invention can be applied in the domestic utilisation of solar energy and further embodiments of the present invention can be applied in the industrial utilisation of solar energy, for example in a solar power plant.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a block diagram schematically illustrating the basic components employed for collection, 'delivery and utilisation of solar energy, with the employment of optical fibres, Figure 2 is a graph showing a typical transmission curve for general purpose optical fibres on a plot of wavelength of radiation transmitted by the fibres against energy transmission efficiency, Figure 3 is a perspective diagram showing an arrangement of optical fibre bundles which may be employed in solar energy collection and delivery apparatus embodying the present invention, Figures 4, 5 and 6 are respective views of solar energy collection and concentration arrays which may be employed for collecting energy for delivery via optical fibres in an embodiment of the present invention Figure 7 is a graph illustrating efficiency of delivery of solar energy to an energy absorber medium versus working temperature of the medium, Figure 8 is a largely sectional view showing an arrangement of a solar energy absorber and connections thereto which may be employed for utilising solar energy delivered by optical fibres in an embodiment of the present invention, Figure 9 is a sectional view taken along the line AA1 in Figure 8, Figure 10 is a sectional view showing a modification of the arrangement of Figure 8, Figure 11 schematically illustrates modified optical fibre bundle configurations that can be employed for delivering solar energy in embodiments of the present invention, Figure 12 illustrates schematically a configuration for a solar power station employing optical fibres in apparatus embodying the present invention.

Figure 13 is a schematic diagram of part of a domestic solar energy utilisation system employing collection and delivery apparatus embodying the present invention, Figure 14 is a schematic diagram of further parts of the system of Figure 13.

Figures l5a and 15b together constitute a block diagram schematically illustrating control connections and energy distribution in a domestic solar energy utilisation system employing apparatus embodying the present invention, Figure 16 is a schematic block diagram illustrating alternative possible domestic energy distribution arrangements in a domes tic solar energy utilisation system embodying the present invention, and Figure 17 is a perspective view, partly cut away, of a house in which a solar energy utilisation system embodying the present invention is employed.

The basic components of a configuration employed for the collection, delivery and utilisation of solar energy in accordance with the present invention are illustrated in Figure 1. Solar energy collector-concentrator 1 collects solar radiation and concentrates the radiation onto the input end of an optical fibre bundle 2. The optical fibre bundle 2 delivers the concentrated solar radiation to an absorber 3 at the point of application of the energy of the radiation, which absorber absorbs the energy contained in the solar radiation. In the examples described hereinafter and relating more particularly to industrial uttilisation of solar energy, in the absorber, which is the means provided at the point of application of the energy for utilising that energy, the solar energy is employed to heat a fluid. The heated fluid may be employed, for example, for the generation of electrical power.In a domestic context the solar energy can be employed at the point of application for example to heat a hot plate or a storage heater, as described hereinafter. In such cases the hot plate, or the storage heater, is the absorber.

Each of the basic components will now be considered in detail.

Optical fibres Optical fibres are, generally speaking, wave guides of electromagnetic radiation at optical frequencies. In an optical fibre use is made of a transparent dielectric coating (e.g. of glass) of one refractive index on a transparent core (e.g. of glass) of another refractive index to conduct radiation within the fibre by multiple reflection. The coefficient of reflection in an optical fibre typically exceeds 0.9999 and high radiation transmissibility can be achieved for wavelengths of the order of 0.3811m to 1.6jam. The graph of Figure 2 shows a typical transmission curve for general purpose optical fibres on a plot of wavelength ( m) of radiation transmitted by the fibres (abscissa) against energy transmission efficiency (%).

An optical fibre bundle consists of a multitude of individual fibres bundled together mechanically.

Energy losses experienced when radiation is transmitted by an optical fibre bundle basically arise from two sources: transmission losses in the optical fibres themselves, and end losses at input and output faces of the bundle.

Transmission losses are mainly due to absorption, scattering, and imperfect reflection in the fibres, and depend on the length of the fibres.

End losses depend upon Fresnel reflection at the input and output end faces of the bundle, the packing factor (inclusive of core coatings) of fibres in the bundle, and quality of polishing (assuming that a cone of radiotion incident on the input end face conforms to the effective numerical aperture of the bundle).

Considering the sun to be a black body source at 100000R typically 80% of emitted energy incident on the input end of an optical fibre will be accepted into the fibre.

As a further illustration, a 1.5 m long optical fibre bundle with resin-bonded fibre input ends and a 5mm active diameter can give an overall transmission efficiency of the order of 60%.

For the present solar energy applications an individual fibre diameter of from 0.05 to 0.1 mm is proposed to be used in optical fibre bundles having an active bundle diameter in the range from 4 mm to 6 mm.

Optical fibre bundles are generally designed to work in an ambient temperature range from -300C to +200 C. An optical fibre bundle with fused fibre ends can withstand, at those ends, temperatures up to + 350 C.

These working limitations have to be taken into account in the design of collectorconcentrators 1 and absorbers 3.

Particularly, a temperature rise is manifest at the input end of an optical fibre bundle.

This temperature rise is mainly due to absorption in interstices between fibre cores and fibre coatings. It is noted that the use of fused fibre ends gives a higher packing factor than the use of bonded fibre ends.

The packing factor should be as high as possible to minimise such rise in temperature, and unwanted heat loss.

At the output end of an optical fibre bundle the problem of output end temperature arises if the bundle is feeding energy to an absorber at the point of application at a temperature higher than 350"C. The location of the output end face of the optical fibre bundle in relation to the absorber should be selected so that radiation or conduction from the absorber does not result in the output end exceeding its working temperature limit, This problem is discussed further below, with reference to absorber design.

For present purposes, where the optical fibre bundles are exposed to the weather, waterproof sheathing compatible with operational environmental conditions is provided for the optical fibre bundles.

Optical fibre bundles with both resin bonded and fused ends are well established.

Bundles with fused ends presently offer the higher packing factor (see above) but require more delicate use.

For the present applications the ends of the optical fibre bundles are provided with attachment sleeves for attachment to collector-concentrators. The attached sleeves may be constituted by glass, ceramic, ferrous or non-ferrous ferrules. The thermal expansion of the attachment sleeves should, of course, be matched to that of the optical fibres.

When connected to solar collector-concentrators (see below) which track daily (and seasonal) movements of the sun (to maximise the amount of energy collected) the optical fibre bundles are subpected to diurnal cyclic flexing. It is anticipated that the bundles will be able to withstand such flexing under the worst conditions (i.e. where the minimum permissible radius of curvature for the bundles is achieved) for many years without loss of transmission.

Thermal cycling of an optical fibre bundle, due to diurnal cycling and input variation due to clouds. may have an effect on the integrity of the input face, but it is anticipated that a useful life of around 40 years may be achieved for the bundle.

In the present purposes, and more particularly for industrial applications of solar energy a number of bundles having individual fibre diameter, and active bundle diameter, as described above) having their input ends connected to respective solar energy collector-concentrators may advantageously be brought together in a larger bundle to deliver solar energy to an absorber at a point of application.

Figure 3 schematically illustrates such an arrangement.

Optical fibre bundles 2, each comprising a multitude of optical fibres 2a in a sheath 2b, have at their input ends respective attachment ferrules 4, for connection to respective collector-concentrators (not shown). A number of bundles 2 are brought together in a non-coherent manner to provide a larger bundle 5 having a common bonded sheath Sa.

At the output end of the bundle 5 the optical fibres are fused to a glass adapter ring 6 for connection with an absorber (not shown), for utilisation of the solar energy in an industrial context. The bundle 5 has an active output area 7 from which is delivered a cone of radiation for absorption in the absorber at a point of application.

A clamping nut 8 and clamping ring 9 are provided for mechanically connecting bundle 5 to the absorber, as explained here Collector-concentrators The collector-concentrators presently preinafter, with reference to Figures 8, 9 and 10.

ferred are based on Fresnel lenses.

However, as alternatives to the use of Fresnel lenses, other types of lenses, parabolic reflectors, simple reflectors or other reflective or refractive means, or combinations thereof, may be employed.

It is presently anticipated that square acrylic Fresnel lenses, for example 15 cm x 15 cm in size, will be suitable. Such lenses may be made by die casting.

Lenses of perspex or other materials, particularly plastics materials, may also be suitable, particularly from the point of view of simplicity of fabrication.

Each fresnel lens directs collected and concentrated solar energy on to the input end of an optical fibre bundle (2 in Figure 3). The input end may be mounted at the focus of the lens and receive energy directly from the lens. Alternatively, correction means may be provided. Such correction means comprise a correcting lens for converting convergent rays delivered from the Fresnel lens into parallel rays which are then incident upon the input end of the optical fibre bundle. The correcting lens may be placed at the focus of the Fresnel lens.

The presence of correcting means can enhance efficiency.

It is proposed that a plurality of collectorconcentrators be arranged together in an array such that the diurnal and seasonal movements of the sun can be tracked.

Figures 4, 5 and 6 provide respective views of such an array which is to stand outdoors, for example to collect energy for industrial utilisation, and illustrate the ability of the array to track the movements of the sun.

The provision of such an ability is greatly facilitated by the flexibility of the optical fibre bundles.

The illustrated array 12 comprises a plurality of collector modules 10 each containing a number of Fresnel lenses and each having a protective glass front cover 11.

The Fresnel lenses in a module 10, and the input ends of the optical fibre bundles 2 connected thereto, are enclosed within the module. This minimises abrasion of the Fresnel lenses and reduction in efficiency due to deposition of dust. The individual optical fibre bundles associated with the individual Fresnel lenses of the module are preferably joined together in a common bundle, as shown in Figure 3.

Filters (not shown) are preferably provided on the modules to ensure adequate air circulation through the modules for dealing with condensation. The filters should be fine, rust-free filters.

Nozzles and guttering may also be provided in the array 12 for delivering water, for example, for cleaning the insides and front faces of the modules 10. The cleaning water may be filtered and recirculated to a main reservoir.

It is proposed that such cleaning opera tions be carried out in the early morning, before useful energy collection commences, with the array parked in the "noon" position (see Figure 4).

As an alternative to the use of modules 10 with glass front covers 11, the modules may be made of a transparent material. The protective glass (or other material) front covers for the modules will result in losses at air-glass, glass-air, air-Fresnel lens, and Fresnel lens-air interfaces. Geometrical defects and absorption in the lenses and the glass covers will result in further losses.

However, it is anticipated that an overall transmission efficiency, from collector module input face to optical fibre bundle output face, of from 30% to 50% will be achieved in practice. This efficiency is defined as the ratio of the energy output of the optical fibre bundle which delivers energy from the module to the energy incident on the glass cover 11 of the module.

The efficiency of the collector-concentrator/ optical fibre bundle combination is independent of the ambient conditions, which is not the case with previously proposed flat plate collectors and concentrators with exposed fluid paths.

The graph of Figure 7 is a plot of the efficiency (ordinate) with which solar energy is collected and delivered at a point of application to a working energy absorber medium against working temperature of the energy absorber medium, and allows a comparis on to be made between conventional collectors (both coated and uncoated) and a collector-concentrator optical fibre bundle arrangement in accordance with the present invention, in which energy from collectorconcentrators is delivered through optical fibre bundles from 5m to 7m in length.

It will be seen that for conventional systems efficiency depends upon the temperature of the working medium into which collected energy is absorbed. It will be seen that for temperatures above 250"C the use of optical fibres offers an efficiency advantage as well as advantages of convenience, and this can be of particular importance in industrial applications.

As mentioned above the array 12 is trackable to follow diurnal movement of the sun.

In the array 12, a plurality of individual collector modules 10 are mounted in a framework 13. The framework 13 is pivotable around a mounting axis 14 on a support structure schematically illustrated at 15. The axis 14 is aligned north-south and is at an angle of, for example, 37 06' to the horizontal (for use at a particular Spanish latitude).

Diurnal tracking gear 16 is provided to turn the array around the axis 14 to follow the daily movements of the sun.

Figure 5 shows the disposition of the array 12 as seen from the west at 1800 hrs.

(GMT) in mid-March or mid-September, whilst Figure 4 shows the disposition of the array at noon at mid-March or mid-September.

Arrangements are also made to follow the seasonal variations in the sun's path across the sky. The illustrated array, as best seen in Figure 5, has four modules 10.

Each of the modules is pivotable within the framework 13 about a pivot axis 17 perpendicular to axis 14.

Seasonal tracking gear (not shown) is provided to turn each of the modules about its axis 17 to allow for seasonal changes in the path of the sun across the sky.

Figure 6 shows, by way of example, the disposition of the modules at noon in midsummer, as seen from the west.

The array is constructed so that no module occludes or shadows another in any disposition of the array for any disposition of the modules within the array.

The daily and seasonal changes in disposition of the modules of the array may be pre-programmed. Transducers may be provided to monitor the disposition of array and of the modules within the array.

The reliability of the array drive, and such transduccrs, are desirable such as will provide a substantial working lifetime for the arrangement in the environmental conditions which will be experienced.

Preferably, however, the modules should be designed so that, in the event of drive failure, and the focussed image of the sun provided by a Fresnel lens in a module 10 moving away from the input end of the optical fibre bundle associated with the lens, the heat dissipation from the external surfaces of the module limits the maximum temperature attainable inside the module.

Further, the sttiffness of the support structure, the array, the modules and the tracking gear should be such that the maximum displacement of the focussed image of the sun provided by a Fresnel lens, laterally with respect to the input end of the associated optical fibre bundle, does not exceed, for example, 0.1 mm under any operational loading conditions. The array 12 should be parked in a horizontal position in adverse weather conditions.

It may be preferable for each module 10 to hold more than ten Fresnel lenses.

The modules may be factory assembled.

In this case the only on-site operation required is clamping of a module in framework 13 and connection of optical fibre bundle 5 to the absorber.

Individual modules may be removed from the framework 13 for repair or replacement. (The link to the absorber for the bundle 5 being closed off as will be better understood from the description of the absorber given below). The remainder of the modules continue to function.

The Absorber In the context of industrial applications, the generation of power, it is presently preferred to use the solar energy to heat a working fluid at the point of application.

The heated fluid may then, for example, be vaporised to drive a turbine to generate electricity. The absorber is, in this context, apparatus wherein the solar energy is delivered to the working fluid.

Figures 8 and 9 shows an absorber 3 wherein energy is transferred from an optical fibre bundle 5 to a working fluid, for example water, where the working temp era- ture of the water does not exceed 350"C (the safe upper temperature limit for the end face of the optical fibre bundle).

The absorber 3 is arranged in a working fluid pipe 19. An absorber chamber 20 defined within the absorber is connected to carry therethrough working fluid passing along the pipe 19, by way of inlet aperture 21 and outlet aperture 22 at opposite ends of the chamber 20 as seen in Figure 8.

The working fluid passes through the chamber along a path generally indicated by arrows 23.

Through an aperture 24, energy from an optical fibre bundle 5 is delivered directly to the working fluid.

The glass adaptor ring 6 (see Figure 3) at the output of the bundle 5 sits in a recess 30 defined by an externally threaded lip 31.

The clamping nut 8 is screwed on to the lip 31 and the adaptor ring 6 is wedged in place by the clamping ring 9. The diameter of the aperture 24 is adapted to the active output area 7 of the bundle 5.

The absorber may be adapted to take a second optical fibre bundle 5 as illustrated at 24a.

When the absorber is in use working fluid impinges directly upon the adaptor ring 6 at the output end of the bundle 5, ensuring efficient transfer of energy to the working fluid.

Advantageously the chamber 20 may be of such a form that turbulence is caused in working fluid passing therethrough, to ensure efficient heating the fluid. For example, conical projections 25, projecting into chamber 20, may be employed to cause turbulence.

If the working temperature of the working fluid is about 350"C it may be unsafe for working fluid passing through an absorber to impinge directly upon an adaptor ring 6 provided directly at the output face of an optical fibre bundle connected to the absorber.

In such a case a modified form of connection between the optical fibre bundle and the absorber such as is shown in Figure 10 may be employed.

In the arrangement of Figure 10 a ceramic tube 32 acts as a spacer between the output end of optical fibre bundle 5 and working fluid in the chamber 20a of the absorber 3.

The ceramic material of the tube acts as a thermal insulator.

The ceramic tube is attached at one end to a clamping nut 8a which is fastened to the lip 31 of the aperture 24. A glass adaptor ring 6a is wedged in place in the recess 30 by means of a clamping ring 9a. Working fluid impinges directly on the glass adaptor ring 6a.

At the other end of the ceramic tube 32, safely isolated from the working fluid, the output end of optical fibre bundle 5 is attached by means of attachment and sealing means 33.

A jacket of thermal insulation 34 may be provided as shown for better thermal isolation of the opposite ends of tube 32.

Thus energy is delivered from the output end of the bundle 5, passes down the tube 32 and through adaptor ring 6a into the working fluid.

Incidentally, it will be seen from Figures 8 and 9 that when a collector module 10 is removed for repair the aperture in an absorber to which the optical fibre bundle 5 from that module is normally connected may simply be closed off with a threaded closure fitted on the lip 31.

It will be seen that a solar power plant in which solar energy is collected and concentrated by means of arrays of collector modules as described above, the collected and concentrated solar energy being passed through optical fibre bundles to absorbers in which the energy is employed at the point of application to heat a working fluid, can be constructed.

Working fluid may be passed around a piping system in which a plurality of absorbers are disposed, effectively concentrating the energy output of many arrays for heating working fluid.

The piping system for carrying the working fluid through the absorbers should be designed so that unwanted heat loss is minimised. For example most of the pipework may be installed underground. If this is done the earth itself will act as a thermal insulator and additionally will provide a large thermal reservoir preventing freezing of water in the pipework if the water is left unheated, in uninsulated pipes, for long periods in winter.

It may be, however, that overground piping will prove economically more advantageous.

In any case it is advised that heat loss from the pipework should not be allowed to exceed 150 Watts per metre run of pipe at a temperature of 5000C within the pipework and preferably, in these conditions, the losses should be limited to 70 Watts per metre run of pipe.

As a further point, the pipework should be designed to accommodate movement due to thermal expansion, and this should also be allowed for in the lengths of the optical fibre bundles 5 and their connections to the absorbers.

The effects of creep on the pipework as a result of the thermal cycling which will be suffered are also to be considered.

Alternative Absorber system As an alternative to leading the output ends of optical fibre bundles 5 directly to the point of application at absorbers 20 as shown in Figures 8, 9 and 10, convex glass lenses may be adapted to the output ends of the bundles 5 so that the energy from the bundles can be transmitted as parallel or slightly convergent beams of light from the output ends to the point of application.

Such a lens may be formed as an integral part of the output end of a bundle 5, as shown at 40 in Figure 11(a), or may be spaced from the output end of a bundle 5 as shown at 41 in Figure ll(b), in which case the transmittance of the lens should, of course, be compatible with the band-pass spectrum of interest.

The parallel or convergent beam of light from a bundle 5 may then be focussed on an absorber input aperture.

Beams of light from a number of bundles could be brought together at a single absorber input aperture.

This system lends itself to use where the working temperature of the working fluid can exceed 550"C, without risk of damage to bundle output ends.

Further, instead of passing working fluid around a pipework loop to a plurality absorbers connected to optical fibre bundles as shown in Figures 8, 9 and 10, a centralised absorber loop system could be employed as illustrated in Figure 12.

In the system of Figure 12 the energy output from optical fibre bundles 5 of modules 10 in the arrays 12 are focussed on to absorbers in a central absorber loop 50 as illustrated.

This system can reduce the length of pipework required and hence heat loss from pipework.

A further system which has features in common with both the absorber systems described above may also be used. This may be particularly advantageous if the working fluid is required to achieve a high temperature, say, 550"C for use in driving a turbine.

In such a system, working fluid is first brought to an intermediate temperature of, say, 350"C using an absorber system as described with reference to Figures 8 and 9.

Working fluid heated to 3500C is then passed through a centralised absorber system as shown in Figure 12, to bring it up to 550"C. In this way, the length of piping carrying high temperature working fluid (above 350"C) can be reduced as compared with a case in which the centralised absorber system is used throughout, and heat losses can be correspondingly reduced.

Figures 13 to 17 illustrate a system embodying the present invention for the domestic application of solar energy.

In the system of Figure 13, solar radiation collection is effected by an array 101 (shown in part only) of collector-concentrators 105, comprising for example Fresnel lenses. The array 101 has essentially the same features as the array of Figures 4 to 6. The lenses of the devices of the array collect solar radiation and focus it onto input ends of optical fibre bundles 102 (with or without correction means). The optical fibre bundles 102 deliver the solar radiation received thereby to an energy delivery point of a solar control switching unit 103 from whence the solar radiation can be distributed via further fibre optics bundles 104, to selected points of application where the solar energy contained in the radiation is to be utilised.

For a typical domestic application the solar radiation collecting area of the array 101 is about 30m2.

The arrays 101 of collector-concentrators 105 is preferably arranged so that the devices are directed in such a manner that the maximum amount of solar radiation is collected thereby at any given time, the array tracking so as to follow the sun as discussed with reference to Figures 4 to 6. Figure 13 illustrates schematically an array which is of simpler detailed construction. Collectorconcentrators 105 are arrayed one after another along an axial mounting member 107 parallel with the earth axis (further collector-concentrators 105 may be arrayed alongside those shown in Figure 13 after another along an axis parallel to the axis of member 107). The individual collectorconcentrators are then arranged so as to be rotatable about mutually parallel axial mounting members 106 so that seasonal effects upon the position of the sun can be accommodated. Alternatively, for accommodating seasonal effects upon the position of the sun, the member 107 may be arranged to be rotatable as a whole out of parallel with the earth axis, the individual collectorconcentrators each being fixedly mounted in relation to the member 107. Further, the illustrated collector-concentrators of the array 101 are arranged together to be collectively rotatable around the axis of mounting member 107 so that the devices 5 follow the daily travel of the sun. These rotations may be manually or automatically effected and controlled.

Possible applications for solar energy derived from array 101 in a domestic situation are illustrated in Figure 14. The collected solar energy may be distributed via optical fibre bundles 104 to, for example, an absorption type refrigeration unit 108 (for example for use in air conditioning) a thermosyphon domestic hot water and storage heater system 109, cooking facilities 110, and other appliances 111, for example for energy storage or conversion.

The control of distribution of solar energy to the various appliances may be effected automatically, in accordance with actual or anticipated demand, by means of programmed switching in the control unit 103 (Figure 13). The control unit 103 may select particular optical fibre bundles 104 along which energy is to be delivered at any time.

As can be seen most clearly in Figure 14 in relation to cooking facilities 110, the collected solar radiation is directed, by means of optical fibre bundles 104, onto a hot plate 112, which is insulated by insulation 113 from fibre optics cooling means 114.

The cooling means 14 serve, for example, to prevent melting of optical fibre bundle ends (see above in relation to maximum operating temperatures).

The use of optical fibre bundles for the distribution of energy can have advantages in ease of installation and in relatively low installation and equipment costs.

The use of optical fibre bundles can enable high or even very high temperatures to be provided.

Further, the optical fibre bundles are subject only to low transmission losses as discussed above and this together with the absence of the necessity for any energy transfer medium for the applications shown in Figure 14 can, subject to the efficiency of concentrating device lenses or reflectors, provide for very efficient utilisation of solar energy in a domestic context.

Apparatus embodying the present invention can be used in a domestic context to provide energy at a point of application for cooking or air-conditioning, as illustrated in Figure 14, for energy storage (for example by chemical means) for energy conversion (for example thermomechanical or thermoelectrical) or, in non-domestic fields, for powering furnaces, pumps, drying equipment, water electrolysis equipment, power generation, and many other uses, conceivably for powering vehicles.

A detailed example of a domestic system in which apparatus embodying the present invention can be used is illustrated in Figures 15a and 15b. The illustrated system is such that mains electrical energy supply is supplemented by utilisation of solar energy (or, conversely, it may be said that back-up mains supply is provided for a solar energy power system).

As illustrated in Figure 13, collected solar radiation is delivered from the array 101, via optical fibre bundles 102, to the solar control switching unit 103, from whence it is delivered by way of optical fibre bundles 104 to points of application at various appliances. Mains electricity is delivered from a supply 115 via supply lines 116 to the various appliances also. Control signals are passed through the system by way of control lines 119.

In the system of Figures 15a and 15b respective optical fibre bundles 104 are available for delivering solar energy to points of application at a cooking hot plate 121, at an air conditioning refrigeration unit 126, at a storage heater 128, and at a hot water tank 146.

Control unit 118 is responsive to the output of a solar energy sensor 120 and in dependence upon the level thereof is operable to turn on or off, via control lines 119, an on/off switch 117. On/off switch 117 is connected, via supply lines 116, on its input side to mains supply 115 and on its output side to a supply adjustment unit 123 and thence to the cooking hot plate 121. The unit 123 serves for adjustment of electrical supply to hot plate 121. An optics control unit 124 has a control connection to an adjustment unit 125 of the solar control switching unit 103, and the overall effect of units 124 and 125 is such that the supply of solar radiation to the hot plate 121 controlled in dependence upon the adjustment of the optics control 124.Mains electricity can be supplied to the plate 121 along a supply line 116, controlled by manual control unit 122, which by-passes on/off switch 117 and which is connected to adjustment unit 123.

On/off switch 117 is also connected on its output side, via a manual control unit 133 and an on/off switch 134, to refrigeration unit 126. The on/off switch 134 is controlled in dependence upon control signals from a thermostat 135, which senses the temperature of the refrigeration unit, and a control unit 136 (which also supplies control signals to the solar control switching unit 103 to control passage of solar radiation to the refrigeration unit 126). The optical fibre bundle 104 which supplies solar radiation to refrigeration unit 126 is also controlled by a manual switch 127 of the solar control switching unit.

On/off switch 117 is further connected on its output side, via a timer 132 (which, for example, is switched on when mains supply is available at an economic off-peak price rate), and a supply adjustment and switchoff unit 131, to storage heater 128. Mains electricity can be supplied to the storage heater 128 along a supply line 116, controlled by manual control unit 130, which bypasses on/off switch 117. Solar radiation is supplied to storage heater 128 along an optical fibre bundle 104 controlled by an adjustment and switch-off unit 129.

Fans 137 and 138 of the refrigeration unit 126 and the storage heater 128, respectively, are supplied with mains electricity, along supply lines 116 by-passing on/off switch 117, via manual control unit 145 and on / off switch 144 and via manual control unit 42 and on/off switch 43 respectively.

The on/off switches 143 and 144 are controlled in dependence upon control signals derived from a room temperature sensor 139, a thermostat 140 and a control unit 141, so that the storage heater 128 and refrigeration unit 126 can be utilised to maintain a constant room temperature for example.

On/off switch 117 is further connected on its output side, via on/off switch 149, to a heater of a hot water tank 146. The on/off switch 149 is controlled in dependence upon control signals derived from a thermostat 150 and a control unit 151. Main electricity can be supplied to the heater of hot water tank 146 along a supply line 116, controlled by a manual control unit 148 and on/off switch 147, by-passing on/off switch 117.

The on / off switch 147 is also controlled in dependence upon control signals derived from thermostat 150 and control unit 151.

The solar control switching unit is also connected to receive control signals from thermostat 150 and control unit 151, in dependence upon which solar radiation supply to the hot water tank is controlled.

It will thus be appreciated that the system of Figure 15 is operable to provide a complete domestic solar/main electrical power arrangement.

in Figure 16 illustrates the manner in which, in a system as shown in Figures 15a and 15b, distribution of solar radiation may be altered in dependence upon seasonal variations in availability of solar energy and demand for energy.

Thus, in hot summer weather, solar energy is more readily available and is, for example, supplied to air conditioning refrigeration unit 126, domestic water heating 146, cooking hot plate 121 and, optionally, energy store 160.

In cold winter weather solar energy is less readily available and air conditioning is not normally required so that energy is supplied to storage heaters 128 and domestic water heating 146 or cooking hot plate 121.

Energy store 160 is not supplied. In intermediate weather energy may be supplied to unit 126 or storage heaters 128 alternatively, to cooking hot plate 121 or energy store 160 alternatively, and to domestic water heating 146 continuously.

Thus, it will be appreciated that the use of fibre optics conductors for the distribution of solar energy can provide for simple, efficient and flexible distribution.

The provision of a solar control switching unit whereby collected solar radiation can be delivered, via respective fibre optics bundles, to each of a number of appliances in a preselected manner and in preselected amounts can further provide for flexibility and efficiency in the use of collected solar energy. However, it will be appreciated that simple direct fibre optics connections between, for example, the collection array 101 and an appliance to be powered by collected solar radiation could be provided so that an energy delivery point at the appliance receives concentrated solar radiation conducted directly thereto.

Figure 17 illustrates a house in which the system of Figure 15 has been installed. As will be seen the collector concentrator array 101 is located in the roof void. At least part of the roof is glazed, to admit light to the array. The solar control panel 103 and the hot water tank 146 are also located in the roof void. Part solar powered air-conditioning refrigeration unit 126 and cooking facilities 121 are provided. Storage heater 128 is located underground, surrounded by thermal insulation 170. Underfloor ducting 171 is provided for circulating air warmed by the storage heater 128 as indicated by arrows in the Figure. The house is preferably constructed from the most suitable materials incorporating double-glazing and insulation to minimise heat loss.

WHAT WE CLAIM IS:- 1. Apparatus for collecting solar energy and delivering collected energy to a point of application, comprising a solar radiation collector, for concentrating solar radiation into a delivery input point of the apparatus, and an optical fibre bundle, having an input end mounted at the said delivery input point to receive concentrated radiation for delivery to the point of application.

2. Apparatus as claimed in claim 1, wherein the solar radiation collector comprises a Fresnel lens.

3. Apparatus as claimed in claim 2, wherein the said input end is mounted at the focal point of the Fresnel lens.

4. Apparatus as claimed in claim 2, wherein a correction lens is mounted at the focal point of the Fresnel lens, for converting convergent rays from the Fresnel lens into parallel rays directed onto the said input end of the optical fibre bundle.

5. Apparatus as claimed in claim 2, 3 or 4, wherein the Fresnel lens is made of a plastics material.

6. Apparatus as claimed in claim 5,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. electricity can be supplied to the storage heater 128 along a supply line 116, controlled by manual control unit 130, which bypasses on/off switch 117. Solar radiation is supplied to storage heater 128 along an optical fibre bundle 104 controlled by an adjustment and switch-off unit 129. Fans 137 and 138 of the refrigeration unit 126 and the storage heater 128, respectively, are supplied with mains electricity, along supply lines 116 by-passing on/off switch 117, via manual control unit 145 and on / off switch 144 and via manual control unit 42 and on/off switch 43 respectively. The on/off switches 143 and 144 are controlled in dependence upon control signals derived from a room temperature sensor 139, a thermostat 140 and a control unit 141, so that the storage heater 128 and refrigeration unit 126 can be utilised to maintain a constant room temperature for example. On/off switch 117 is further connected on its output side, via on/off switch 149, to a heater of a hot water tank 146. The on/off switch 149 is controlled in dependence upon control signals derived from a thermostat 150 and a control unit 151. Main electricity can be supplied to the heater of hot water tank 146 along a supply line 116, controlled by a manual control unit 148 and on/off switch 147, by-passing on/off switch 117. The on / off switch 147 is also controlled in dependence upon control signals derived from thermostat 150 and control unit 151. The solar control switching unit is also connected to receive control signals from thermostat 150 and control unit 151, in dependence upon which solar radiation supply to the hot water tank is controlled. It will thus be appreciated that the system of Figure 15 is operable to provide a complete domestic solar/main electrical power arrangement. in Figure 16 illustrates the manner in which, in a system as shown in Figures 15a and 15b, distribution of solar radiation may be altered in dependence upon seasonal variations in availability of solar energy and demand for energy. Thus, in hot summer weather, solar energy is more readily available and is, for example, supplied to air conditioning refrigeration unit 126, domestic water heating 146, cooking hot plate 121 and, optionally, energy store 160. In cold winter weather solar energy is less readily available and air conditioning is not normally required so that energy is supplied to storage heaters 128 and domestic water heating 146 or cooking hot plate 121. Energy store 160 is not supplied. In intermediate weather energy may be supplied to unit 126 or storage heaters 128 alternatively, to cooking hot plate 121 or energy store 160 alternatively, and to domestic water heating 146 continuously. Thus, it will be appreciated that the use of fibre optics conductors for the distribution of solar energy can provide for simple, efficient and flexible distribution. The provision of a solar control switching unit whereby collected solar radiation can be delivered, via respective fibre optics bundles, to each of a number of appliances in a preselected manner and in preselected amounts can further provide for flexibility and efficiency in the use of collected solar energy. However, it will be appreciated that simple direct fibre optics connections between, for example, the collection array 101 and an appliance to be powered by collected solar radiation could be provided so that an energy delivery point at the appliance receives concentrated solar radiation conducted directly thereto. Figure 17 illustrates a house in which the system of Figure 15 has been installed. As will be seen the collector concentrator array 101 is located in the roof void. At least part of the roof is glazed, to admit light to the array. The solar control panel 103 and the hot water tank 146 are also located in the roof void. Part solar powered air-conditioning refrigeration unit 126 and cooking facilities 121 are provided. Storage heater 128 is located underground, surrounded by thermal insulation 170. Underfloor ducting 171 is provided for circulating air warmed by the storage heater 128 as indicated by arrows in the Figure. The house is preferably constructed from the most suitable materials incorporating double-glazing and insulation to minimise heat loss. WHAT WE CLAIM IS:-

1. Apparatus for collecting solar energy and delivering collected energy to a point of application, comprising a solar radiation collector, for concentrating solar radiation into a delivery input point of the apparatus, and an optical fibre bundle, having an input end mounted at the said delivery input point to receive concentrated radiation for delivery to the point of application.

6. Apparatus as claimed in claim 5,

wherein - the said plastics material is an acrylic.

7. Apparatus as claimed in any preceding claim, comprising at least one collector array having a plurality of such collectors, the collectors of the array concentrating radiation onto -respective such delivery input points at which input ends of respective optical fibre bundles are mounted.

8. Apparatus as claimed in claim 7, wherein the or each collector array is manoeuverable as a whole so that the collectors of the plurality in the or each array can be caused to track movement of the sun.

9. Apparatus as claimed in claim 7 or 8, wherein the collectors of the said plurality in the or each array are movable within the array concerned, so that the collectors can be caused to track movements of the sun.

10. Apparatus as claimed in claim 7, 8 or 9, wherein the optical fibres of a plurality of optical fibre bundles, respective input ends of which are mounted at respective such delivery input points, are brought together into a larger bundle, for delivery of concentrated radiation to such a point of application.

11. Apparatus as claimed in any preceding claim, wherein the optical fibres of a bundle having an input end at such a delivery input point extend directly to such a point of application, at which an absorber is provided.

12. Apparatus as claimed in any preceding claim, wherein the optical fibres of a bundle having an input end at such a delivery input point extend to a switching unit, from whence a further optical fibre bundle extends to such a point of application, at which an absorber is provided, the switching unit being operable to direct, or not to direct, solar radiation delivered thereto by the said optical fibres that extend to the switching unit to the further optical fibre bundle for onward delivery to the absorber at the point of application concerned.

13. Apparatus as claimed in any one of claims 1 to 10, wherein at an output end of a bundle (which may be a larger bundle) the optical fibres of which form a bundle or bundles having an input end or input ends mounted at such a delivery input point or at respective such delivery input points, an output lens is provided whereby solar radiation emerging from the said output end is focussed on an absorber which is provided, spaced apart from the said output end, at such a point of application.

14. Apparatus as claimed in claim 13, wherein the said output lens is formed as an integral part of the said output end.

15. Apparatus as claimed in claim 13 or 14, wherein a plurality of such bundles (which may be larger bundles), having respective output lenses at their output ends, are arranged for focussing solar radiation emerging from those output ends onto a single absorber which is provided, spaced apart from those output ends, at such a point of application.

16. Apparatus as claimed in any one of claims 11 to 15, wherein the or each such absorber the energy of the solar radiation delivered to the point of application concerned is employed to heat a working fluid.

17. Apparatus as claimed in claim 16, wherein the or each such absorber defines a chamber, through which a flow of working fluid is caused to pass when the apparatus is in use, having an input aperture through which solar radiation is delivered to heat the working fluid.

18. Apparatus as claimed in claim 17, wherein the chamber of the or each such absorber is of such a form that turbulence is induced in the flow of working fluid that passes therethrough, for the more efficient transfer of energy to the working fluid.

19. Apparatus as claimed in claim 17 or 18, read as appended to claim 11 or 12, wherein the optical fibres which deliver collected solar radiation to the working fluid in the chamber of such an absorber terminate at an optical fibre bundle output end that is provided with a glass adapter ring, fixed to the optical fibres of that bundle, which fits the said input aperture of the absorber concerned so that its outer face is -in contact with the working fluid.

20. Apparatus as claimed in claim 17 or 18, read as appended to claim 11 or 12, wherein the input aperture of the or each such absorber is closed by a glass adapter ring having a face in contact with the working fluid, the or each such absorber further comprising a tube of a thermal insulator one end of which is mounted at the input aperture of the absorber concerned, the optical fibres which deliver collected solar radiation to the working fluid in that absorber terminating at an optical fibre output end that is mounted at the other end of the tube, so that radiation emerging from the optical fibres of that bundle passes down the tube and through the glass adapter ring into the working fluid in the chamber of the absorber, whereby the output end of that optical fibre bundle is thermally isolated from the working fluid.

21. Apparatus as claimed in any one of claims 17 to 20, comprising a plurality of such absorbers arranged in a working fluid circuit so that the working fluid passes in turn through each absorber, to be progressively heated.

22. Apparatus as claimed in claim 21, comprising a first plurality of absorbers, each as claimed in claim 19 or 20, arranged in the said working fluid circuit so that the working fluid passes through each absorber of the first plurality to be progressively heated, and a second plurality of absorbers, each as claimed in claim 13, to which the working fluid heated by the absorbers of the first plurality is passed for further heating.

23. Apparatus as claimed in claim 12, wherein there are provided a plurality of absorbers, at respective such points of application, to each of which such further optical fibre bundles extend, the switching unit being selectively operable to direct or not to direct solar radiation to any selected absorber of the plurality.

24. Apparatus as claimed in claim 23, wherein the absorbers of the plurality include a cooking hot plate, a storage heat, an absorption type refrigeration unit, or a water heater.

25. Apparatus as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawings.