GB2473328A

GB2473328A - Apparatus for generating electricity and heat from solar energy

Info

Publication number: GB2473328A
Application number: GB1014092A
Authority: GB
Inventors: Stephen William Bell; John Robert Cottle
Original assignee: HELIOCENTRIC POWER Ltd
Current assignee: HELIOCENTRIC POWER Ltd
Priority date: 2009-09-03
Filing date: 2010-08-23
Publication date: 2011-03-09
Anticipated expiration: 2030-08-23
Also published as: GB2473328B; GB0915387D0; GB201014092D0

Abstract

An apparatus 2 for generating electricity and heat from solar energy comprises: an array of photovoltaic cells 4, such as triple junction cells, for generating the electricity and heat; a heat exchanger 6 for receiving the heat generated by the photovoltaic cells; optical means 8 for focussing rays from the sun; positioning aligning means 10 for enabling the optical means to track the path of the sun; a heat store 12 for receiving and storing heat from the heat exchanger; and a microprocessor controller 14 for controlling the operation of the apparatus. The apparatus further comprises a container 52 for collecting the rays from the sun including an aperture 54 for admitting the rays into the container and an interior surface 56 which causes the rays which are inside the container to strike the photovoltaic cells at right angles. The heat exchanger may be of a sandwich construction with fins designed to maximise heat transfer. Preferably, the optical means is a concave reflector such as a parabolic mirror, where the reflector may be made from aluminium, stainless steel, or from polycarbonate with vacuum deposited aluminium. The position aligning means may include motors (46, 48; fig.2) for controlling elevation and azimuth.

Description

F

I

APPARATUS FOR GENERATING ELECTRICITY AND

HEAT FROM SOLAR ENERGY

This invention relates to apparatus for generating electricity and heat from solar energy. The apparatus may be a generating station for harvesting solar energy from the sun.

Apparatus for generating electricity from solar energy is known.

Apparatus for generating heat from solar energy is also known. Often the two types of apparatus are inefficient in their use of the solar energy.

It is an aim of the present invention to provide apparatus for generating both electricity and heat from the solar energy, and which apparatus is efficient in operation.

Accordingly, in one non-limiting embodiment of the present invention there is provided apparatus for generating electricity and heat from solar energy, which apparatus comprises: (i) an array of photovoltaic cells for generating the electricity and the heat; (ii) a heat exchanger for receiving the heat generated by the photovoltaic cells; (iii) optical means for focussing rays from the sun; (iv) positioning aligning means for enabling the optical means to track the path of the sun; (v) heat storage means for receiving and storing heat from the heat exchanger; (vi) microprocessor control means for controlling operation of the apparatus; and (vii) a container for collecting the rays from the sun, the container comprising an aperture for enabling the rays of the sun to enter the container, and an interior surface which causes rays from the sun that are inside the container to strike the photovoltaic cells at right angles to the photovoltaic cells.

The apparatus of the present invention is able to generate both electricity and heat, and in an efficient manner. The apparatus may be in the form of a generating station for harvesting solar energy, for example a local micro solar heat and power generation station for domestic andlor industrial purposes.

The apparatus of the present invention is able to harvest solar energy to maximise energy yield at the high latitudes of Northern Europe where there is a large variation in solar energy availability over the yearly cycle of summer, autumn, winter and spring. These cyclic variations are out of phase with required usage demand. The apparatus of the present invention is able to store harvested excess energy for demand phase shifting. Also, the apparatus of the present invention is able to maximise the collection of available energy in winter months.

The apparatus may be one in which the photovoltaic cells are triple junction photovoltaic cells. The triple junction photovoltaic cells may respond to different energy spectrum wavelengths, and convert a maximum amount of light in the visible spectrum or near visible spectrum into electricity.

Presently preferred photovoltaic cells are those manufactured by Boeing Spectrolab and known as Boeing Spectrolab Terrestrial Solar Cells.

The Boeing Spectrolab Terrestrial Solar Cell has an efficiency of 40%, and it is considerably smaller than conventional photovoltaic cells which have an efficiency peak of about 18%.

The apparatus of the present invention may be one in which the heat exchanger is of a sandwich construction with fins constructed to maximise heat transfer from plates into cooling.

The optical means may be a concave mirror. The concave mirror is preferably a parabolic mirror. The parabolic mirror may be a one piece parabolic mirror, or it may be a parabolic mirror which is made in two or more pieces.

The concave mirror, for example the parabolic mirror, may be made of a polycarbonate with vacuum deposited aluminium on the back. Transmission losses may occur through the polycarbonate. Alternatively, the mirror may be a stainless steel mirror. This may give an attenuation effect at some frequencies. Alternatively, the mirror may be an aluminium mirror. The aluminium should be treated to ensure that it does not oxidise.

The position aligning means may comprise: (a) a first motor for controlling elevational movement of the optical means; and (b) a second motor for controlling azimuth movement of the optical means.

The elevational movement may be controlled using a toothed arc, The azimuth movement may be controlled using a worm drive and toothed ring.

Other arrangements may be employed for the elevation movement and the azimuth movement.

The control means may include: (a) calendar means for determining where the sun ought to be; and (b) monitor means for monitoring output from different parts of the array of photovoltaic cells in order to provide information on where the sun actually is.

With information from the calendar means and the monitoring means, the control means is able to control operation of the position aligning means so that the optical means is able to track the path of the sun and thereby obtain maximum solar energy.

S

The heat storage means may be an underground heat storage means.

The underground heat storage means preferably has a plurality of holes. The holes may extend vertically and/or horizontally. The vertical holes may be in the form of pits. The horizontal holes may be in the form of trenches. The underground heat storage means will be able to store a large amount of heat.

The heat storage means may alternatively be a swimming pool. The swimming pool may be in private houses, schools, health centres, holiday centres and fitness centres. Other types of heat storage means may be employed, for example water tanks.

The apparatus of the present invention may include a heat pump for retrieving heat from the heat storage means, the retrieved heat being in the form of a hot fluid. The heat pump may heat the hot fluid to a higher temperature, for delivery at a greater temperature than when the fluid was retrieved from the heat storage means. The delivered hot fluid may be used for domestic heating, or for agricultural or horticultural purposes. Alternatively, the heat pump may coot the hot fluid, for delivery at a lower temperature than when the fluid was retrieved from the heat storage means. In this case, the cooled fluid may be used for air conditioning systems in summer.

The apparatus may be one in which the microprocessor control means controls the position aligning means such that the optical means follows the sun, and in which the microprocessor means senses the brightest available part of the sun from which the optical means receives rays from the sun.

Other means may be employed for ensuring that the optical means receives the maximum amount of rays from the sun.

With small photovoltaic cells, for example the above mentioned Boeing Spectrolab Terrestrial Solar Cell, it may be advantageous to use the small cells in conjunction with a solar concentrator. The solar concentrator is able to focus a large area of solar energy onto a relatively small array of the photovoltaic cells, thereby to provide the opportunity to increase efficiency.

A preferred solar concentrator is a container for collecting the rays from the sun, the container comprising an aperture for enabling the rays of the sun to enter the container, and an interior surface which causes rays from the sun that are inside the container to strike the photovoltaic cells at right angles to the photovoltaic cells. The container may allow the use of reflected rays, and bring them in a forwards direction to the photovoltaic cells.

The container may have a waffle-shaped grid at one end. The grid may enable the container to minimise or avoid reflection losses in the container.

The grid may also enable the container to be connected to other containers without loss of radiation at the connection point between two containers.

The container can be of any desired shape, including cylindrical, conical, square, hexagonal and octagonal.

The apparatus may be one in which there are two of the grids, in which the grids are positioned back to back, in which the heat exchanger has a heat conductive plate, and in which the two grids are integrated with the heat conductive plate.

The control means may comprise control software for effecting the following functions: * sun trajectory tracking (full sun and cloud cover) * temperature control and cooling of the photovoltaic cells * managing and optimising the production of electrical power * managing the heat storage and recovery system * building/dwelling heat management * monitoring performance and recommending maintenance (collect cleaning etc) * extreme weather shut-down protection * apparatus functioning monitoring and reporting.

The apparatus may be one in which the optical means is configured to leak air and thereby reduce wind resistance. The optical means may be configured to leak air by being provided with a plurality of slots.

The apparatus may be one in which the optical means is of a saucer shape, and in which the saucer shape includes aerodynamic formations for causing the saucer shape to have an improved aerodynamic shape.

Preferably, the aerodynamic formations are provided at a rim part of the saucer shape, and at a rear convex surface of the saucer shape.

The apparatus may include parking means for parking the mirror in a horizontal position in high winds.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows apparatus of the present invention; Figure 2 is a side view of optical means and position aligning means shown in Figure 1; Figure 3 is a front view of the parts of the apparatus shown in Figure 2; Figure 4 is an enlarged sectional view of part of the apparatus as shown in Figure 2; Figure 5 is a sectional view of an alternative to the part of the apparatus as shown in Figure 4 and illustrates the passage of light rays within the container; Figure 6 is a plan view of a waffle grid which is present at the left hand end of the container used in the apparatus of the present invention; Figure 7 is a side view of the waffle-shaped grid as shown in Figure 6; Figure 8 is a side view of a different design for the optical means and incorporating a mirror plate; and Figure 9 is a plan view of the mirror plate usedin Figure 8.'' * Referring to Figures 1 -7, there is shown apparatus 2 for generating electricity and heat from solar energy. The apparatus 2 comprises: (I) a matrix of photovoltaic cell 4 for generating the electricity and the heat; (ii) a heat exchanger 6 for receiving the heat generated by the photovoltaic cells 4; (iii) optical means 8 for focussing rays from the sun; (iv) position aligning means 10 for enabling the optical means to track the part of the sun; (v) heat storage means 12 for receiving and storing heat from the heat exchanger; and (vi) microprocessor control means 14 for controlling operation of the apparatus 2.

As shown in Figure 1, hot water is able to pass along pipe 16 to hot water control valves 18. A pipe 20 connects the hot water control valves 18 to a house 22. A pipe 24 is connected to the pipe 20 and leads to a heat pump 26. The microprocessor control means 14 is connected by a cable 28 to the hot water control valves, by a cable 30 to the house 22, and by a cable 32 to the heat pump 26. A further cable 34 provides power control to the photovoltaic cells 4, the heat exchanger means 6 and the optical means 8.

Raw electricity passes along cable 36. As shown in Figure 1, the microprocessor control means 14 is connected by a cable 38 to the World Wide Web 40, and by a cable 42 to an electricity grid 44, for example, a local or national grid.

Referring to Figures 2 and 3, it will be seen that the position aligning means 10 includes a first motor 46 for controlling elevational movement of the optical means 8, and a second motor 48 for controlling azimuth movement of the optical means. As shown in Figure 3, the optical means 8 is a focussed mirror 8 which is preferably a parabolic mirror. Figure 2 shows the heat exchanger 6, the array of photovoltaic cells 4, and a mounting frame 50 for the photovoltaic cells 4.

Figures 2 and 4 illustrate how the apparatus 2 includes a container 52 for collecting the rays from the sun. The container 52 comprises an aperture 54 for enabling the rays of the sun to enter the container 52. The container 52 has mirror polished internal surfaces 56. The photovoltaic cells 4 concentrate rays from the sun at a focal point 58. A light ray 60 is shown.

Figure 5 is like Figure 4 but shows an alternative arrangement with light guides 61 in the form of a waffle-shaped grid 62, which is shown in more detail in Figures 6 and 7. Also shown in Figure 5 is an electric bus bar 64 for the photovoltaic cells 4. Also shown are a heat exchanger 65, and light rays passing through the focal point 58.

In operation of the apparatus 2 shown in Figure 1, the heat exchanger 6 harvests heat from the sun and also cools the array of photovoltaic cells 4.

The microprocessor control means 14 manages all of the functions of the apparatus 2 shown in Figure 1 which is basically a power station. The microprocessor control means 14 optimises the output of energy by both open and closed loop function control. The microprocessor control means 14 optimises the electrical power that can be extracted from the array of photovoltaic cells 4, and feeds the electrical power into the electricity grid 44.

If no grid connection is available, then the microprocessor control means 14 is able to manage electricity storage and use from a battery bank (not shown).

The microprocessor control means 14 is also able to manage the heat generation and the storage of the heat. A flow of coolant through the heat exchanger 6 is actively controlled to obtain an optimum photovoltaic cell I1 operating temperature, and also to maximise usable heat yield. The microprocessor control means 14 also manages the heat storage means 12.

The optical means 8 is preferably in the form of a parabolic mirror which focuses sunlight onto the array of photovoltaic cells 4. The photovoltaic cells 4 are mounted on the heat exchanger 6, attached to the mirror 8 by support struts forming part of the mounting frame 50. The heat exchanger 6 allows for the extraction of the thermal content of the solar energy arriving at the array of photovoltaic cells. The first and second motors 46, 48 enable elevation and azimuth motions to track the trajectory of the sun. The first and second motors 46, 48 are managed by the microprocessor control means 14.

The apparatus 2 is able to be expanded by the addition of further photovoltaic cells 4, heat exchangers 6, optical means 8 and heat storage means 12. A basic unit of the apparatus 2 may be 4m2. Each unit may be able to provide approximately 1.6kW of electrical power and approximately 1.6kW of thermal energy.

Some of the energy that it is focussed on the photovoltaic cells 4 will be reflected off the surface of the photovoltaic cells 4. This reduces the efficiency of the energy yield. The light reflected from the edges of the reflector is worst affected, as it strikes the photovoltaiC cell surface at the shallowest angle. Most of the energy collected is at the outer surfaces of the reflector where the area is largest. This is of little consequence in times of maximum solar flux. However, under poor light conditions, any losses should be avoided to ensure maximisation of the energy yield. This maximisation of the energy yield is effected by the heliocentric array of photovoltaic cells 4 being surrounded by the light collector container 52. The parabolic mirror B is focussed in front of the array of photovoltaic cells 4 at the aperture 54 in the front of the container 52. The light passes through the aperture 54 and strikes the surface of the photovoltaic cells 4. The energy that reflects from the surface of the photovoltaic cells strikes the polished internal surfaces 56 inside the container 52, and is reflected off the internal surfaces 56, eventually arriving back at the surface of the photovoltaic cells 4. The use of the container 52 helps to maximise energy yield in winter months.

The photovoltaic cells 4 are preferably triple-junction photovoltaic cells 4. They require sunlight to be concentrated on their surface by a factor of 500 -1000 times. The apparatus of the present invention uses the reflecting concentrator container 52 to focus sunlight onto the array of the photovoltaic cells 4. This only works if the collector (i.e. the parabolic mirror 8) is pointing at the sun. The use of the first and second motors 46, 48 ensures that the movement of the sun is tracked. The microprocessor control means 14 operates to provide the following controller functions: * sun trajectory tracking (full sun and cloud cover) * temperature control and cooling of the photovoltaic cells * managing and optimising the production of electrical power * managing the heat storage and recovery system * building/dwelling heat management * monitoring performance and recommending maintenance (collect cleaning etc) extreme weather shut-down protection apparatus functioning monitoring and reporting.

The elevation and azimuth control operates using either a calendar/almanac within the control system, or by computation using date, time and geographic location of the collector. The tracking system operates continuously from sunrise to sunset, and is independent of the degree of cloud cover. The microprocessor control means 14 may utilise a fine tune function that operates by small cone dither, and ensures maximum optimum energy capture.

The microprocessor control means 14 regulates the electrical power output of the array of photovoltaic cells 4. Electric current is fed to a DC link.

The microprocessor control means 14 regulates the voltage of the link to maximise output from the photovoltaic cells 4. The microprocessor control means 14 regulates the output voltage in order to ensure maximum power output from the prevailing level of sunlight and collector surface reflectivity which may be affected by environmental contamination.

The microprocessor control means 14 is able to regulate the output of a grid-connect inverter to ensure the DC link is maintained at an optimum level for given light conditions.

The array of photovoltaic cells 4 is mounted on the heat exchanger 6 which is liquid-cooled. The microprocessor control means 14 is able to regulate fluid flow through the heat exchanger 6, in order to maintain the array of photovoltaic cells 4 at a predetermined and appropriate temperature.

Heated fluid from the heat exchanger 6 is harvested for domestic use or for thermal storage. A secondary heat exchanger is advantageously provided for this purpose. The microprocessor control means 14 regulates flow in both heat exchangers in order to control usage and storage temperatures at set levels.

Excess heat, i.e. that heat which cannot be utilised immediately or stored, is diverted to a passive air-cooled heat exchanger. Recovery of stored heat energy, for example for winter heating, is realised by the heat pump 26.

The microprocessor control means 14 manages all aspects of thermal control, storage, usability and excess. The microprocessor control means 14 is able to manage installations with multiple generators. The microprocessor control means 14 is also capable of managing the heat and cooling requirements of buildings.

The cyclic nature of the heat yield inevitably results in a surplus of heat during summer months. The heat storage means 12 is therefore employed.

The heat storage means 12 is preferably a ground source heat storage means 12 which is used in conjunction with the heat pump 26. The heat storage means 12 and the heat pump 26 allow storage and recovery of the heat. The stored heat is able to be recovered from the heat storage means 12 by the heat pump 26 under the management of the microprocessor control means 14. The apparatus 2, for example a power station, is flexible and can utilise other heat storage means such for example as water tanks and swimming pools. The apparatus 2 can provide air conditioning during summer months, putting unwanted heat into the heat storage means 12.

A typical performance for a 4m2 unit of the apparatus 2 operating as a heat and electricity generating station is as follows: Nominal Output Electricity -1.6kW Nominal Output Thermal -1.6kW Collector Area -4m2 Max Cell Array Operating Temperature -70°C Azimuth Sweep -1800 Elevation Sweep -900 Concentration -1000 Suns Cell Array -CDO-100-.IC Controller -DPS with lnverter Foot Print -Approx 3.3m Square As indicated above, the solar energy concentrator is preferably in the form of a concave mirror and especially a parabolic mirror. The mirror may be of any diameter and is not necessarily of circular form. The solar energy is brought to a focus on the photovoltaic cells which may be regarded as a semi-conductor block. With a focus beam, the higher energy can more efficiently be converted into electricity by the photovoltaic processes afforded by the photovoltaic cells with their semi-conductor materials.

The magnification of the apparatus 2 may be expressed as a ratio of the area of the mirror divided by the area of the array of photovoltaic cells.

The unit of magnification is usually called a "sun" and systems typically operate at magnifications of between 200 and 1000 "suns". Optimising the chosen value requires variation according to latitude and many other conditions.

The apparatus of the present invention may generate photovoltaic electricity at an efficiency conversion of 40%, which is approximately twice the efficiency of conversion of currently known apparatus. In energy terms, the amount of collectable heat may be roughly the same as the electricity generated. Thus the overall system efficiency in converting solar energy to usable energy is potentially of the order of 80%.

As also indicated above, the energy collection by the apparatus of the present invention is optimised by the use of a solar energy connector such for example as the container 52. In order to achieve the highest reflection coefficients from a mirror surface, the reflection should not be accompanied by losses inherent in layers of plastic or varnish that absorb solar energy.

Also, the surface of any mirror, or mirror elements, should not scatter the reflected beam beyond the photovoltaic cells 4 and the heat exchanger 6.

Irregularities in the reflector surface resulting in scattering of a lesser nature are unimportant provided the scattered beam is captured in its entirety.

Precision in the focussed beam greater than this can be counter-productive, unless the beam is brought to a focus at the aperture 54 of the container 52, which container 52 is designed to deliver all the radiant energy uniformly over the array of photovottaic cells 4. The container 52, or other container operates to maximise the radiation that passes through the small aperture 54 which positioned at the focal length of the mirror, and to ensure that the divergent beam from that point falls directly on the surface of the photovoltaic cells 4 or via the walls of the container 52 at a low angle of incidence. This minimises losses between the aperture 54 and the photovoltaic cells 4, and allows control over the uniformity of radiant intensity by variation of the internal surface finish of the container 52 and its orientation. The internal surface of an aperture cap may be mirror polished to minimise retro-refiective losses.

Generally, the container 52 may provide the following features: (i) a hollow cylindrical container having a mirror-finished internal surface.

(ii) a container with a diameter of the order of the array of photovoltaic cells 4 where the beam strikes.

(iii) an aperture 54 that limits the diameter of the entering beam and provides an inner-mirror surface where retro-reflected energy is able to be returned to the array of photovoltaic cells.

(iv) the diameter of the aperture 54 is located at the focal length of the mirror such that there will be a converging beam before it and a diverging beam thereafter. This defines the maximum "suns" magnification, but not the actual magnification at the surface of the photovoltaic cells.

(v) the container 52 can have any cross-sectional shape, so that it can for example be circular, square, hexagonal or octagonal.

The container 52 may adopt a non-parallel aspect along its length, which can be chosen to optimise the distribution of radiation over the surface of the array/block of photovoltaic cells 4.

(vi) the container 52 may incorporate irregularities on its internal surface or surfaces 56, so as to optimise the distribution of the radiation over the array of photovoltaic cells 4.

(vii) the container 52 may have dimensions which can be adjusted so as to allow a wide range of different focal lengths, for example to take advantage of some locations where there is a low profile and therefore a short focal length.

(viii) The container 52 may incorporate a double-walled jacket to allow heat to be collected and carried away advantageously.

The internal surface 56 of the container 52 is mirror-polished. The photovoltaic cells 4 may be lOm x 10mm. To allow for electrical connections (not shown), the photovoltaic cells 4 may be spaced 6mm apart. An array of strips in a "naughts and crosses" pattern, each with a generally triangular profile, may be employed to shield the spaces. The height of the strips may be 30mm but this value may be modified to optimise performance. The faces of the strips are mirror-polished. The strips may each have one face perpendicular to the plane of the photovoltaic cells 4, and one sloping face.

The perpendicular faces are all nearest to the principle axis.

Light arriving at the centre of the mirror is reflected axially to the container 52. Light reflected from the edge of the mirror may arrive anywhere across the face of the aperture. Light from the edges of the mirror entering the container 52 near the edge of the aperture 54 strike the photovoltaic cell 4.

All these rays may strike a strip, but always on its inner (axial and vertical) face. Reflection, should they arise, will be angled toward the axis.

The reflections ensure that no arriving solar energy fails to be collected by the photovoltaic cells 4.

The collector 52 may be varied in dimensions. In particular, if the aperture 54 is increased, the spread of the rays is increased, which ma' require the diameter and length of the container 52 to be varied. Also, height adjustments of the strips may be needed to avoid non-optimal reflections from the "rear" of the strips.

As mentioned above, the collector 52 advantageously has a waffle-shaped grid 62 at one end. The waffle shape is created between each photovoltaic cell 4. The waffle-shaped grid 62 has the following features: (i) a wall of thickness sufficient to allow for electrical connections between the photovoltaic cells 4 and beyond.

(ii) a wall having an upstand of height adequate to collect incident radiation at grazing incidence where the reflection will be delivered to the surface of the photovoltaic cells 4. 4 0

(iii) the upstand has a shape which is generally the shape of a knife edge.

(iv) a polished surface is not necessary.

(v) the material of construction may need to be heat-resistant and yet electrically non-conducting so that the material of construction may typically be a ceramic material.

(vi) the array of photovoltaic cells 4 may be assembled but not flat, so as to form a concave surface (depending on the position of the electrical connection) which will allow the width of the wall to be minimised.

(vii) the geometry of the waffle-grid 62 should allow optimum interfacing with the design of the heat collection system including the heat exchanger 6.

The apparatus of the present invention is such that the mirror 8 may give wind resistance. The wind resistance may be forces acting an a perpendicular direction, and aerodynamics to cover the forces that arise from the side where the mirror presents an aerofoil section. The apparatus of the invention may be fitted with a shut-down facility that enables the mirror to be parked horizontally when it is desirable, for example in high winds. Such parking would however not be desirable at low wind speeds where useful sunlight would be lost if the mirror were to be parked. To enable continued * operation at higher wind speeds, the mirror may be designed with wind-resistance and aerodynamic considerations in mind and reference will now be made to Figures 8 and 9. In Figures 8 and 9, wind resistance is reduced by arranging for the surface of the mirror plate 70 to leak air. One way of doing this is to use slots 72. The slots 72 form air gaps. The slots 72 are provided in such a way as to ensure that the solar capture area is not reduced. This may require the slot profile to be in the plane at right angles to the reflective surface.

With regard to aerodynamic considerations, a saucer shape will generally lift in a planar air flow with lower pressure over a convex region. An aim may be to break up the pressure differentials that cause it. This may be done in two areas, namely one at the rim and the other at the rear convex surface. At the rim, it is necessary to break up the leading edge effect that leads to a lower pressure over the convex region. This can be done by fitting a narrow flange angled towards the rear. It may also have a slot. Over the convex region, small tabs may be mounted in a circular arrangement, for example linearly or randomly orientated. Wind-resistance slots may be used.

Wind-resistance reduction considerations may be as follows: (i) a mirror dish having slots in its structure so as to allow the passage of air.

(ii) The position of slots so arranged so as not to reduce the reflective area of the mirror. * I

(iii) the plane of the slots to be generally at right angles to the surface of the mirror.

(iv) the surface of the mirror to be divided into a number of elements which are not co-planar.

(v) the non-co-planar surface elements should remain focussed and the same focal point as if the surface rearrangements were not present.

(vi) the adjacent co-planar elements may be above or below the next surface.

Aerodynamic considerations may be modifications to the mirror in order to ensure damaging loads or vibrations do not occur by: * (a) the fitting of a flange to the outer rim to break-up leading edge laminar flow, and/or (b) the fitting of small upstands systematically or randomly arranged over the convex surface.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Also, various parts of the drawings may be used for different types of apparatus of the present invention.

Claims

ICLAIMSApparatus for generating electricity and heat from solar energy, which apparatus comprises: (i) an array of photovoltaic cells for generating the electricity and the heat; (ii) a heat exchanger for receiving the heat generated by the photovoltaic cells; (iii) optical means for focussing rays from the sun; (iv) positioning aligning means for enabling the optical means to track the path of the sun; (v) heat storage means for receiving and storing heat from the heat exchanger; (vi) microprocessor control means for controlling operation of the apparatus; and (vii) a container for collecting the rays from the sun, the container comprising an aperture for enabling the rays of the sun to enter the container, and an interior surface which causes rays from the sun that are inside the container to strike the photovoltaic cells at right angles to the photovoltaic cells. 4 a
2. Apparatus according to claim 1 in which the photovoltaic cells are triple-junction photovoltaic cells.
3. Apparatus according to claim 1 or claim 2 in which the heat exchanger is of a sandwich construction with fins constructed to maximise heat transfer from plates into cooling.
4. Apparatus according to any one of the preceding claims in which the optical means is a concave mirror.
Apparatus according to claim 4 in which the concave mirror is a parabolic mirror.
6. Apparatus according to claim 4 or claim 5 in which the mirror is made of a polycarbonate with a vacuum-deposit aluminium on the back.
7. Apparatus according to claim 4 or claim 5 in which the mirror is a stainless steel mirror.
8. Apparatus according to claim 4 or claim 5 in which the mirror is an aluminium mirror.
9. Apparatus according to any one of the preceding claims in which the position aligning means comprises: a (a) a first motor for controlling elevation movement of the optical means; and (b) a second motor for controlling azimuth movement of the optical means.
10. Apparatus according to claim 9 in which the control means includes: (a) calendar means for determining where the sun ought to be; and (b) monitor means for monitoring output from the different parts of the array of photovoltaic cells in order to provide information on where the sun actually is.
11. Apparatus according to any one of the preceding claims in which the heat storage means is an underground heat storage means.
12. Apparatus according to claim 11 in which the underground heat storage means has a plurality of holes.
13. Apparatus according to claim 12 in which the holes extend vertically and/or horizontally.
14. Apparatus according to any one of claims 1 -10 in which the heat storage means is a swimming pool or a tank.I
15. Apparatus according to any one of the preceding claims and including a heat pump for retrieving heat from the heat-storage means, the retrieved heat being in the form of a hot fluid.
16. Apparatus according to claim 15 in which the heat pump heats the hot fluid for delivery at a greater temperature than when the fluid was retrieved from the heat storage means.
17. Apparatus according to claim 15 in which the heat pump cools the hot fluid for delivery at a lower temperature than when the fluid was retrieved from the heat storage means.
18. Apparatus according to any one of the preceding claims in which the microprocessor control means controls the position aligning means such that the optical means follows the sun, and in which the micro-processor control means also senses the brightest available part of the sun from which the optical means receives rays from the sun.
19. Apparatus according to any one of the preceding claims in which the container has a waffle-shaped grid at one end.
20. Apparatus according to claim 19 in which there are two of the grids, in which the grids are positioned back to back, in which the heat exchanger has a heat conductive plate, and in which the two grids are integrated with the heat conductive plate.
21. Apparatus according to any one of the preceding claims in which the microprocessor control means comprises control software for effecting the following functions: * sun trajectory tracking (full sun and cloud cover) * temperature control and cooling of the photovoltaic cells * managing and optimising the production of electrical power managing the heat storage and recovery system * building/dwelling heat management * monitoring performance and recommending maintenance (collect cleaning etc) * extreme weather shut-down protection * apparatus functioning monitoring and reporting.
22. Apparatus according to any one of the preceding claims in which the optical means is configured to leak air and thereby reduce wind resistance.
23. Apparatus according to claim 22 in which the optical means is configured to leak air by being provided with a plurality of slots.
24. Apparatus according to any one of the preceding claims in which the optical means is of a saucer shape, and in which the saucer shape includes 4 * aerodynamic formations for causing the saucer shape to have an improved aerodynamic shape.
25. Apparatus according to claim 24 in which the aerodynamic formations are provided at a rim part of the saucer shape, and at a rear convex surface of the saucer shape.
26. Apparatus according to any one of the preceding claims and including parking means for parking the mirror in a horizontal position in high winds.
27. Apparatus for generating electricity and heat from solar energy, substantially as herein described with reference to the accompanying drawings.