GB2558245A

GB2558245A - Photovoltaic systems

Info

Publication number: GB2558245A
Application number: GB1622064.2A
Authority: GB
Inventors: Nashat Sahawneh Faris
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-12-22
Filing date: 2016-12-22
Publication date: 2018-07-11
Also published as: GB201622064D0

Abstract

A concentrator photovoltaic (PV) system, comprising: at least one PV module 1 having at least one solar cell; at least one reflector 2 having a reflective surface arranged at a tilt angle configured to reflect solar radiation onto the at least one PV module 1; and a mechanism for adjusting the tilt angle of the reflective surface; wherein the tilt angle of the reflective surface is adjustable relative to horizontal during operation. The system may comprise a temperature sensor. The tilt angle may be dependent on the time of day or year. The PV module may be covered, at least in part, by a film to reflect infrared (IR) radiation. The reflector may be moved so as to cover and protect the PV system. The system may also include a solar thermal collector which can be arranged between adjacent PV modules. The reflective surface may be curved or planar.

Description

(54) Title of the Invention: Photovoltaic systems

Abstract Title: PHOTOVOLTAIC SYSTEM INCLUDING REFLECTOR (57) A concentrator photovoltaic (PV) system, comprising: at least one PV module 1 having at least one solar cell; at least one reflector 2 having a reflective surface arranged at a tilt angle configured to reflect solar radiation onto the at least one PV module 1; and a mechanism for adjusting the tilt angle of the reflective surface; wherein the tilt angle of the reflective surface is adjustable relative to horizontal during operation. The system may comprise a temperature sensor. The tilt angle may be dependent on the time of day or year. The PV module may be covered, at least in part, by a film to reflect infrared (IR) radiation. The reflector may be moved so as to cover and protect the PV system. The system may also include a solar thermal collector which can be arranged between adjacent PV modules. The reflective surface may be curved or planar.

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PHOTOVOLTAIC SYSTEMS

Field of the Invention

This invention relates to photovoltaic (PV) systems, in particular to a system and method for optimising the performance of PV modules in a low concentration PV system.

Background

Renewable energy has become a major objective for many countries around the world. Solar photovoltaic (PV) technologies have recently become more feasible than in the past with prices of PV modules reducing around the world. Although still in a research and development stage, without large-scale commercialization, it is thought that concentrator photovoltaic (CPV) technology can further reduce the price of PV systems and has the potential to become one of the most feasible renewable energy technologies.

CPV systems are generally classified as low, medium and high CPV systems, with low CPV (LCPV) systems capable of handling irradiance levels of 2 to 100 suns, medium CPV (MCPV) capable of handling irradiance levels of 100 to 300 suns, and high CPV (HCPV) systems capable of handling irradiance levels of up to 1,000 suns, or more. To handle higher irradiance levels CPV systems generally comprise specially designed PV modules, which utilise CPV cell technology.

CPV systems generally employ one or more reflective surfaces (e.g. “reflectors” or “mirrors”) to concentrate solar power onto the PV cells and thereby increase the power output of the PV module. A low-concentration photovoltaic (LCPV) system that is being commercialized is the C7 system developed by Sunpower, which can handle up to 7 suns and is integrated in a segmented parabolic trough-type concentrator that tracks the sun.

In another exemplary LCPV system, described in “Low-X Single-Axis Solar Louver Tracking System for Residential Rooftop Applications, K Casperson et al, DOI:10.1109/PVSC.2011.6186111”, two reflectors are placed at opposing ‘east’ and ‘west’ sides of PV cells configured to operate up to irradiance levels of 3 suns. However, the arrangement of two reflectors on opposite sides of the PV module may limit the ability to integrate solar thermal collectors into the system. The reflector arrangement may also limit the ability to use ordinary PV modules. Indeed, the system is designed to operate at between 2 to 3 suns at all times during useful hours of the day (i.e. one hour after sunrise and one hour before sunset). This system requires the incorporation of modified PV modules and cold mirror films.

Other LCPV systems are described in “T. J. Hebrink (2012): Durable Polymeric Films for Increasing the Performance of Concentrators, Third Generation Photovoltaics, Dr. Vasilis Fthenakis (Ed.), InTech, DOI: 10.5772/28889”. For example, a non-tracking LCPV mirror design is described, which incorporates an electronically smart PV module that can handle shading and non-uniform irradiance levels (Tenksolar). Another exemplary PV system comprises a single axis and dual axis carousel trackers (JX Crystal), “Fraas L, Minkin L, Huang H, Maxey C, Gehl A 2008), Carousel Trackers with 1 sun or 3 sun Modules for Commercial Building Rooftops, Proceeding of ASES Conference, 2008, San Diego, California, USA”.

In addition, US7569764 describes solar modules with tracking and concentrating features; WO2010/099236 describes a one-dimensional concentrator photovoltaic system; US9353974 describes a solar collecting device; and US 2006/0054212 describes solar photovoltaic mirror modules.

A primary barrier for concentrator PV technologies to enter the main-stream market is the requirement for large investments to develop the industry for manufacturing specialized CPV cells and modules.

Summary of Invention

The present invention seeks to provide an improved low-concentration photovoltaic (LCPV) system, and to alleviate at least some of the disadvantages associated with the prior art PV systems described above.

Described herein is a concentrator photovoltaic (PV) system, comprising: at least one PV module having at least one solar cell; at least one reflector having a reflective surface arranged at a tilt angle configured to reflect solar radiation onto the at least one PV module; and a mechanism for adjusting the tilt angle of the reflective surface; wherein the tilt angle of the reflective surface is adjustable relative to horizontal during operation.

Optionally, the tilt angle is adjustable relative to horizontal during operation depending on at least one of: the solar altitude angle, the solar azimuth angle, the irradiance level, the temperature, and other parameters. The invention involves novel concepts in the system design and method of operation that enables PV systems to generate maximum power with an optimized performance. Unlike the technologies in the prior art the present invention can be applied to many types of PV modules, including the ordinary main-stream market PV technologies, for example polycrystalline silicon PV modules (having the largest market share of PV modules sold annually). The invention can even be applied to existing solar power stations (i.e. retrofitted on an existing solar power station).

By providing the system with a reflector arranged to be moveable so as to change its tilt angle relative to horizontal, the performance of the PV module can be optimised due to the amount of solar radiation reflected onto the PV module being controllable to ensure that maximum energy can be generated by the PV system, for example to accommodate the varying solar altitude angles and/or other parameters at different times of day and year (i.e. the system enables the PV module to operate at peak power at different times of day and year). Novel design concepts described later can allow many types of PV modules to operate at their peak power.

The tilt angle of the reflective surface (or reflector) may be adjustable both relative to the horizontal and to the at least one PV module. The at least one reflector may be moveable relative to the at least one PV module so as to change the tilt angle of the reflective surface. The at least one reflector may be arranged to move along a track configured to define, at least in part, a curved path. The at least one reflector may be arranged to pivot relative to the at least one PV module, optionally wherein the at least one reflector is attached to a rotatable shaft.

Optionally, the tilt angle of the reflective surface may alternatively be considered to be adjustable relative to vertical, or adjustable relative to a surface or structure to which the reflector (or the PV system) is mounted or attached, for example. Optionally, the tilt angle of the PV module is not adjusted when the tilt angle of the reflective surface is adjusted. The reflector may be attached to the PV module, optionally being directly attached or to a housing or casing (or similar) that houses the PV module.

Optionally, the reflective surface may be arranged to have a tilt angle in a range that can be determined from the equations described later on. The convention used in the equations defines the tilt angle such that the angle between the PV module 1 and the reflector 2 equals the sum of the tilt angle and 90 degrees. In other words, the reflector 2 has zero tilt angle when it is perpendicular with the PV module 1- has positive tilt angles when the angle between the PV module 1 and the reflector 2 is obtuse (i.e. greater than 90 degrees) and negative tilt angles when the angle between the PV module 1 and the reflector 2 is acute (i.e. less than 90 degrees). Of course, the tilt angle can be expressed in alternative conventions (e.g. relative to the horizontal).

Optionally, the reflective surface is completely planar. A planar reflective surface may ensure that the PV module receives uniform irradiance levels. The at least one reflector may comprise a plurality of reflectors each having a reflective surface.

The at least one reflector may have at least two reflective surfaces, optionally two opposing reflective surfaces, which may be arranged to reflect solar radiation in two directions, for example away from both the front and rear of the reflector.

The at least one reflector may comprise a plurality of reflectors, optionally which may be arranged to be adjusted simultaneously, for example in unison. A member (e.g. a shaft or rod) arranged to couple with each of the plurality of reflectors may be arranged to move the plurality of reflectors in unison. The plurality of reflectors may be arranged to be adjusted simultaneously using a gearing mechanism and/or a common shaft, optionally wherein the gearing mechanism comprises gears attached to each reflector, optionally wherein the gears are of a non-circular profile.

The at least one reflector may have an extendable section having a reflective surface arranged to increase the total surface area of the reflective surface. The extendable section may be slidably attached to the at least one reflector, for example such that in a non-extended configuration the extendable section can be stored behind the reflective surface.

Optionally, the at least one reflector may comprise at least one of: aluminium; mirror glass; and cold mirror.

The at least one PV module may comprise a plurality of PV modules arranged adjacently, for example in a row. The at least one reflector (or reflective surface) may extend substantially the width of the at least one PV module, preferably such that the reflective surface can reflect solar radiation onto each PV module. Optionally, the at least one reflector (or reflective surface) may be arranged to extend beyond (e.g. either one, or optionally both, of) the outermost PV module(s), for example so as to reflect solar radiation onto the side of the PV module(s) to avoid non-uniform irradiation levels on the outermost PV module at times close to sunrise or sunset.

The at least one PV module may be arranged to be placed directly on the ground (e.g. PV modules attached parallel to the ground on supports that are attached directly above ground level). The at least one PV module may be arranged to be inclined (or sloped) upwards from the ground, for example such that a lowermost part of the PV module rests on a ground level support and an uppermost part of the PV module is inclined above it. The at least one reflector may of course be capable of being adjusted to change the tilt angle. In such arrangements, the at least one PV module may have a fixed slope, optionally being arranged on a static rack for maintaining the slope.

Alternatively, the at least one PV module may be arranged to be supported spaced above (or from) the ground, optionally wherein the at least one PV module can pivot (or tilt) relative to the ground, for example wherein the at least one PV module is mounted on a raised support.

The solar cell(s) in the PV module may be silicon-based or a multi-junction cell. The solar cell(s) may comprise silicon or lll-V compounds, such as gallium arsenide (GaAs). The at least one PV module may be covered by a film (or another suitable covering) arranged to reflect infrared radiation (e.g. light).

The mechanism for adjusting the tilt angle of the reflector may comprise at least one actuator arranged to change the tilt angle of the reflective surface. The PV system may further comprise a (e.g. micro) controller configured to control the tilt angle of the reflective surface, for example by controlling the at least one actuator. At least one sensor may be arranged to determine at least one of: ambient temperature and the temperature of the at least one PV module.

The controller may be configured to monitor the temperature of the at least one PV module to determine whether the temperature exceeds a predetermined value, and further to move the at least one reflector upon determining that the predetermined value has been exceeded.

The controller may be configured to monitor the rate of change of the temperature of the at least one PV module, so as to estimate the desired tilt angle that would achieve a preferred operating temperature for the at least one PV module.

At least one sensor may be arranged to determine the tilt angle of the at least one reflector relative to at least one of: horizontal and the at least one PV module. At least one sensor may be arranged to measure power output of the at least one PV module. At least one sensor may be arranged to detect an amount of solar radiation incident on the at least one PV module.

The controller may comprise a (e.g. micro) processor configured to calculate a required tilt angle for the at least one reflector based on at least one of: the power output of the at least one PV module; the amount of solar radiation incident on the at least one PV module; the temperature of the at least one PV module; and the ambient air temperature.

The controller may be configured to move the at least one reflector to a maximum tilt angle away from the at least one PV module upon detection of a fault in the system, for example wherein the temperature of the at least one PV module exceeds a predetermined value.

The controller may be configured to move the at least one reflector to a predetermined tilt angle relative to the at least one PV module upon determination that a detected solar irradiance falling on the at least one PV module is below a predetermined value. The sensor for detecting an amount of solar radiation incident on the at least one PV module may comprise a pyranometer and/or a pyrheliometer.

The at least one reflector may be capable of being moved to a position in which it at least partially covers the at least one PV module, and optionally covers the entire surface of the at least one PV module so as to provide protection.

The PV system may further comprise at least one solar thermal collector, for example which is disposed between adjacent PV modules, and/or for example which is arranged to receive solar radiation reflected from the at least one reflector. Optionally, at least one further reflector having a reflective surface may be arranged to reflect solar irradiance onto the at least one solar thermal collector. The at least one further reflector may be a static reflector, for example arranged to be static relative to the PV module and/or adjustable reflector. Optionally, the reflective surface may have a curved profile.

The PV system may further comprise a cold mirror film arranged to at least partially cover the at least one solar thermal collector. Optionally, the cold mirror film may be connected to a rotating section arranged to control the length of the cold mirror film covering the at least one thermal collector, for example to fold and unfold the film. This arrangement may be used in relation to an arrangement wherein a PV module and reflector are arranged 90 degrees apart, optionally wherein the PV module and the reflector are arranged to be fixed in that relationship, as discussed further on.

The PV system may further comprise an arrangement for cleaning the at least one PV module and/or at least one reflector automatically, optionally wherein the cleaning means is integrated into the system.

Also described herein is a method of optimising the performance of a concentrator photovoltaic system as described herein, the method comprising: obtaining at least one input value relating to a parameter associated with the PV module; determining a desired tilt angle of the reflective surface based on the input value; and adjusting the tilt angle of the reflective surface to the desired tilt angle. Optionally, the method is performed by the controller, for example by a processor of the controller.

By comparing at least one input value relating to a parameter associated with the PV module to a predetermined (or expected) value, the tilt angle of the reflective surface can be adjusted (e.g. controlled) based on this comparison to ensure that the amount of solar radiation reflected onto the PV module allows optimum performance of the PV system to ensure that maximum energy can be generated by the PV system, for example to accommodate the varying solar altitude angles and/or other parameters at different times of day and year.

The method may further comprise comparing the input value against a predetermined value, wherein the desired tilt angle of the reflective surface is based on said comparison. The input value may be the temperature of the PV module and the predetermined value may be a maximum operating temperature, such that when the temperature of the PV module approaches the maximum operating temperature, the tilt angle can be adjusted to reduce the amount of reflected solar irradiance on the PV module before it reaches the maximum operating temperature (e.g. a predetermined tolerance margin away from the maximum temperature).

The input value may be a rate of change of temperature of the PV module and the predetermined value may be an expected rate of change of temperature, wherein the rate of change of temperature may be to estimate the desired tilt angle that would give a preferred operating temperature of the PV module.

The method may further comprise determining a desired position of the reflector based on at least one of: the power output of the at least one PV module; the amount of solar radiation incident on the at least one PV module; the temperature of the at least one PV module; and the ambient air temperature.

The input value may be the measured solar irradiance falling on the PV module and the predetermined value may be an expected solar irradiance, such that when the measured solar irradiance is below the expected solar irradiance, the desired position of the reflector is a position in which the amount of solar radiation reflected onto the PV module is increased, optionally to a maximum amount possible.

Also described herein is an apparatus for use in the system described herein, comprising: a first section arranged to support the at least one PV module; and a second section arranged to support the at least one reflector having a reflective surface arranged to reflect solar radiation onto the at least one PV module; wherein the second section is arranged to be moveable so as to change the tilt angle of the reflective surface relative to horizontal during use.

By providing a housing for both the PV module and the reflector that allows the tilt angle between the reflective surface and horizontal to be adjusted when in operation, a convenient apparatus for implementing the PV system described herein may be provided.

The second section may be further arranged to be moveable relative to the first section. Optionally, the first and second sections may be arranged to be fixed at 90 degrees apart, for example to form a substantially V-shaped arrangement. Optionally, the V-shaped arrangement may be controlled to be facing the sun (i.e. an equivalent zenith angle perpendicular to the aperture plane), for example at one or more times of the day of year. The equivalent zenith angle may be defined herein as the projection of the zenith angle on the north - south vertical plane.

The apparatus may further comprise a rotatable shaft, for example wherein the housing is attached to the shaft such that rotation of the shaft tilts the housing relative to horizontal. Optionally, the rotatable shaft may be arranged to conceal electrical connections and/or heat transfer pipes concealed within, optionally wherein the shaft is hollow.

The first section of the apparatus may comprise at least one extruded portion arranged to contain fluid for the transfer of heat away from the at least one PV module.

The invention may extend to a system and/or apparatus substantially as described herein and/or as illustrated in the accompanying drawings.

As used herein, the terms ‘reflecting surface’ and ‘mirror’ may be used interchangeably. The term ‘reflector’ may also occasionally be used to refer to the ‘reflective surface’.

As used herein, the term ‘horizontal’ may connote a plane that is generally parallel with the horizon; and/or a plane that is tangential to the surface of the Earth; and/or a plane that is perpendicular (or normal) to the (imaginary) radius of the Earth, for example. It may also be used to refer to a generally ‘flat’ portion of the ground (or a suitable surface) on which the PV module may be rested or supported, in use or operation, for example.

As used herein, the term ‘vertical’ may connote a plane that is generally parallel with the (imaginary) radius of the Earth; and/or a plane that is normal to horizontal, for example.

As used herein, the term ‘solar altitude angle’ preferably connotes the angle of the sun in the sky (i.e. the angle between the line to the sun and the horizontal), for example which can be related to the angle of incidence of the solar radiation on the reflective surface, and therefore the angle of reflection of the solar radiation onto the PV module.

The ‘solar altitude angle’ (or ‘solar elevation angle’) is related to the ‘solar zenith angle’. These two angles are complementary (i.e. the cosine of either one of them equals the sine of the other).

As used herein, the terms ‘mirror’ and ‘reflector’ may be used interchangeably, both of which may have a reflective surface. Also, the terms ‘level’ and ‘amount of’ may be used interchangeably with reference to solar irradiance.

Brief Description of Drawings

Aspects and embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1a and 1b show a PV system with a reflector arranged on the ground in front of a PV module;

Figures 2a and 2b show a PV system with a PV module arranged on the ground in front of an adjustable reflector;

Figure 3 shows solar radiation being reflected by different regions of a reflector partly onto a PV module;

Figure 4 shows a general layout of an exemplary PV power plant;

Figure 5 shows the PV system of Figures 2 to 4 incorporating solar thermal collectors;

Figure 6 shows another example of a solar thermal collector incorporated into a PV system;

Figure 7 shows a further example of a solar thermal collector incorporated into a PV system;

Figure 8 shows a PV system having an inclined PV module and an adjustable reflector that can be retrofitted to existing solar power stations;

Figure 9 shows an alternative PV system having an inclined PV module and an adjustable reflector that can be retrofitted to existing solar power stations;

Figure 10 shows a PV system utilizing smaller PV modules;

Figure 11 shows a method of adjusting the tilt angle of multiple reflectors;

Figure 12 shows another method of adjusting the tilt angle of multiple reflectors;

Figure 13 shows various angles and other relevant measurements used in the equations disclosed herein;

Figure 14 shows a PV system having an extendable reflector;

Figures 15a and 15b show an alternative arrangement for changing the tilt angle of a reflector;

Figure 16 shows the PV system of Figure 5 utilizing cold mirrors;

Figure 17 shows a single-axis tracking PV system with an adjustable reflector;

Figure 18 shows another example of a PV system where the PV module and reflector are arranged 90 degrees apart;

Figure 19 shows another example of a PV system having a foldable cold mirror;

Figure 20 shows a plurality of PV modules and reflectors being arranged in a closed unitized system;

Figure 21 shows various reflector tilt angles vs. the hour angle at selected days of the year; and

Figures 22a and 22b show the ratio of the solar irradiance reaching PV modules over the maximum irradiance for varying hour angles for PV modules having different mirror lengths.

Description of Various Embodiments

With reference to Figures 1a and 1b, a simple low concentration photovoltaic (LCPV) system may comprise a reflector 85 placed horizontally on the ground (e.g. flat, or at substantially zero degrees) and a PV module 1 that is tilted relative to the reflector 85 so as to receive ‘indirect’ (e.g. reflected) solar radiation from the reflector 85. A limitation of this PV system is, however, that the solar radiation reflected by the reflector 85 may only reach the PV module 1 if the slope of the PV module 1 (i.e. the angle between the PV module and the horizontal.) is greater than the projection of the solar altitude angle on the north - south vertical plane (i.e. for PV modules 1 facing south in the northern hemisphere or facing north in the southern hemisphere).

For high solar altitude angles, as illustrated in Figure 1a, the slope of PV module 1 will need to be very steep in order for it to receive any extra ‘indirect’ irradiance 82 from the reflector 85, but this has the detrimental effect of greatly reducing the amount of ‘direct’ irradiance 81 that can reach the PV module 1. Thus, the PV module 1 cannot achieve its full power output for high solar altitude angles using a horizontal reflector 85; in other words, the PV module 1 cannot operate at its full power output at certain times of the day.

If the reflectors 85 used were diffuse reflective rather than specular, then the ‘indirect’ irradiance received by the PV module 1 may not differ greatly from albedo (ground reflected) radiation reflected from any high reflectivity ground surface.

Moreover, as illustrated in Figure 1b, even for low solar altitude angles, the PV module 1 may only receive reflected solar radiation 84 on part of the PV module 1, if tilted to face the sun - different irradiance levels on the PV module 1 would severely reduce output power. To address this, the slope of the PV module 1 would have to be reduced, which in turn limits the direct irradiance 83 reaching the PV module 1 at low solar altitude angles.

In more detail, Figure 1b shows an incident ray 83 with a low solar altitude angle, and a reflected ray 84, reflected from an end of the reflector 85, reaching a region in the middle of the PV module 1, thus causing non-uniform radiation levels. Thus, at low solar altitude angles, the reflected rays 83, 84 can cause non-uniform radiation levels to fall on the PV module 1, assuming the slope of the PV module 1 is optimal. Fora plurality of PV modules 1 arranged in rows, for example, there is a requirement for large reflectors 85 and a requirement for large PV module 1 spacing to avoid shading of the reflector 85.

Given a large enough mirror length, such PV systems may perform well in certain situations, with full PV module 1 power being achievable for very limited times (e.g. in the winter season with lower midday solar altitude angles and with the assumption that there are no clouds in the sky). However, calculations have shown that for any equivalent zenith angle (i.e. the projection of the zenith angle on the north - south vertical plane) below 30 degrees the reflector 85 does not perform its function and the optimal slope of the PV module 1 will be equal to the equivalent zenith angle (i.e. PV modules facing the sun). For equivalent zenith angles above 30 degrees, the optimal slope of the PV module 1 will be 90 degrees (with the approximation that solar radiation is totally reflected by the mirror and the mirror is large enough) - this slope would cause non-uniform irradiance to fall on the modules for reasonable mirror lengths - thus requiring the module slope to be reduced until uniform radiation levels are achieved.

In summary, the PV system of Figures 1a and 1b works best for very limited times with certain solar positions for large mirror lengths and large module spacing; otherwise, when the sun is above a certain altitude angle, the angle of incidence is such that much of the “extra” solar radiation 82 reflected by the reflector 85 cannot not reach the PV module 1, as shown in Figure 1a.

Figures 2a and 2b show an arrangement of a PV module 1 and reflector 2, according to the concepts of the present invention. In use, the PV module 1 is placed horizontally on ground level supports or at a raised horizontal level above the ground and the reflector 2 is arranged to reflect solar radiation onto the PV module 1. Furthermore, the slope of the reflector 2 (or the reflective surface) may be changed (i.e. the tilt angle is changed) relative to the PV module 1. The reflector 2 may be mechanically tilted to control the amount of reflected solar irradiance incident on the PV module 1.

Typically, the PV module 1 may have a substantially laminar, rectangular shape. The dimensions of the PV module 1 may be approximately 1m x 2m, for example in the main-stream market. The length 31 of the PV module (used in later calculations) may be chosen as the smaller of the two dimensions, thereby allowing for smaller reflector 2 lengths (e.g. the length of the reflective surface). The reflector (or ‘mirror’) length may range from approximately 0.25m to 1m for PV module lengths 31 of about 1m (i.e. a mirror length ratio range of 0.25 to 1).

By allowing the reflector 2 to move between a first position 43 (Figure 2a) - where the reflector 2 is tilted (i.e. moved) towards the PV module 1 - and a second position (Figure 2b) - where the reflector 2 is tilted (i.e. moved) away from the PV module 1 - the slope of the reflector 2 relative to the PV module 1 changes and thus the total amount of solar radiation falling on the PV module 1 - both ‘directly’ (from the sun) and ‘indirectly’ (i.e. reflected from the reflector 2) - can be controlled. Indeed, by allowing the reflector 2 to move relative to the PV module 1 it is possible to ensure that an optimum amount of solar radiation falls on the PV module 1 such that the PV module 1 can operate near its peak power at many different times of day and year.

Figures 2a and 2b also show that the effective length 32 of the reflector 2 (i.e. the length of reflector area, which reflects solar radiation inside the PV module area) changes as the angle of tilt (e.g. slope) of the reflector 2 changes. Figure 2a shows that as the reflector is tilted (e.g. moved) towards the PV module 1 (i.e. towards the first position 43), the effective length 32 of the reflector 2 increases until it becomes substantially the entire length of the reflector 2. Further tilting of the reflector 2 towards the PV module 1 beyond this point is undesirable, as it will cause non-uniform radiation levels to fall on the PV module 1. Figure 2b shows the effective length 32 of the reflector 2 being decreased (e.g. to around the mid-point 33) of the reflector 2 as it is tilted (e.g. moved) away from the PV module 1 towards the second position 44. For example, when solar radiation is high (normally with high solar altitude angles) and when the total amount of incident solar radiation (direct and reflected) exceeds the targeted irradiance level on the PV module 1, or if a PV module 1 approaches its maximum operating temperature, then the reflector 2 should be tilted away from the PV modules (e.g. towards the second position 44). The previous ‘relative’ position 40 of the reflector 2 is also indicated.

When solar radiation is high and the PV module 1 is overheated, the reflector 2 can be tilted away 44 from the PV module 1 to reduce the amount of reflected irradiance falling on the PV module 1. The solar radiation is shown as both an incident solar ray 41 on the reflector 2, and a reflected solar ray 42 on the PV module 1. As will be understood, the reflector 2 may be tilted either towards 43 or away 44 from the PV module 1.

Figure 3 shows the PV module 1 and moveable reflector 2 arrangement of Figure 2b in more detail in relation to the reflection of solar radiation 34, 35, 36 by the reflector 2. As described above, the reflector 2 has an effective length 32 that may be described as the length (and hence a corresponding area can be defined) of reflector 2, for a given slope of the reflector 2, which will reflect solar radiation 36 onto the PV module 1. As can be seen in Figure 3, any solar radiation 34, 35 that is reflected by the reflector 1 by a region of the reflector 2 that extends beyond the end point 33 of the effective length 32 of the reflector 2 will not be reflected onto the PV module 1. As will be understood, the effective length 32 of the reflector 2 will change according to, for example, the tilt angle of the reflector 2 and the solar altitude angle (i.e. the projection of the solar altitude angle on the north - south vertical plane).

In Figure 4, an exemplary layout of a photovoltaic (PV) power plant is shown, which comprises several rows (e.g. arrays) of PV modules 1 having at least one reflector 2 arranged to reflect solar radiation onto the PV modules 1, as described above with reference to Figure 2 and Figure 3. A plurality of PV modules 1 may be arranged in a row, preferably a large number of PV modules 1, as this may reduce the total number of mechanical tilting systems connected to the rows, or individual motors connected to each row. Also the extra reflector width 30 required at the ends of a row would become insignificant as a percentage of total reflector 2 width with increasing number of PV modules 1 in a row. Optionally, one reflector 2 may be provided for each row of PV modules 1. The reflector(s) 2 may be hinged to the PV module(s) 1.

A spacing region 5 is provided between adjacent rows of PV modules 1. The spacing region 5 may be minimised to save space, especially for a space limited application, such as a rooftop solar arrangement. The minimum spacing region 5 may be determined by the minimum distance that would avoid having a row of PV modules 1 being shaded by the reflector 2 of an adjacent row of PV modules 1.

Each reflector 2 is arranged to extend beyond the row of PV modules 1, which allows the reflectors 2 to reflect a uniform amount of solar radiation on the PV modules 1 placed at the ends of each row during times near to sunrise or sunset.

The tilt angle of the reflectors 2 can be controlled by an arrangement of sensors and actuators (not shown). The required tilt angle of the reflectors 2 at different times can be calculated using equations described later. The range of tilt angles for a PV system is dependent on the latitude, the solar irradiance levels, the mirror length, and optionally other parameters. Each PV system may have a specific preferred range of tilt angles depending on these parameters. For use in the UAE, for example (see Figure 21 for exemplary UAE related data) for a system with a mirror length ratio of 0.4, the range of tilt angles required is (-8.2° < 0_r < 57.9°). For larger mirror length ratios this range of tilt angles would tend to increase. Also, for higher latitudes, and for the winter season, the range of tilt angles required would tend to shift towards negative tilt angles.

The actual tilt angle during the operation of the PV system can be further adjusted by feedback from one or more sensors, including feedback from the measured power output from the PV modules, feedback from solar radiation sensors, and feedback from temperature sensors that measure the module temperatures and ambient temperature. The amount of tilt of the reflectors 2 towards the PV modules 1 is controlled (e.g. adjusted) to ensure that the reflectors 2 reflect an amount of solar irradiance that allows the PV modules 1 to operate near their maximum rated power. An inverter (not shown) may be provided to the PV system, to convert the variable direct current (DC) output of the PV modules 1 to an alternating current (AC) arrangement, which can be supplied to a conventional electrical grid. The inverter can also provide data of the power output from the PV modules. A system control that uses the power output feedback from the inverters can be used to ensure that the PV modules 1 never operate beyond their maximum rated power while still allowing the PV modules 1 to operate near their maximum rated power.

The maximum amount of allowable tilt of the reflectors 2 towards the PV modules 1 varies with the amount of solar irradiance. This key feature of the system enables this CPV technology to be applied to many types of PV module (e.g. Silicon, Cadmium Telluride, etc.), including main-stream market PV modules (e.g. polycrystalline Silicon PV modules, which currently have the largest market share of PV modules sold annually) and newly developed PV modules. It can also be applied to modules in an existing power station (see Figures 7 and 8), as the power generated would never exceed the maximum rated power of the system. The maximum power calculations would take into account the efficiency reduction in the PV modules due to higher operating temperatures.

A further feature of the system utilises feedback from temperature sensors (not shown), which measure the PV cell temperatures during operation as well as the ambient temperature, to ensure that the system never operates beyond the maximum operating temperature of the system. This temperature feedback also enables the system to track the tilt angle of the reflectors 2 that would give a preferred operating temperature.

The determination of the required tilt angle adjustment to achieve a preferred operating temperature can be performed by several methods - in the simplest form this would involve a control system that would alter the tilt angle of the reflectors 2 to reduce the reflected solar irradiance incident on the PV modules 1 by a calculated amount if the temperature of the modules exceeds a defined maximum. Further methods of temperature control may include recording the rate of change of the temperature. This can provide further information that can be used to track the tilt angle of the reflectors 2 that would give the preferred operating temperature. Many variations of temperature tracking methods can be utilized - ultimately; the temperature tracking of the system will fine-tune the tilt angle of the reflectors 2 until the chosen temperature of operation is achieved.

Figure 5 shows the arrangement of the PV modules 1 and reflectors 2 with solar thermal collectors 3 placed within the spacing region between rows of PV modules 1. The reflectors 2 are tilted to an optimal angle for that specific direction of incoming solar radiation, and are hinged 4 to the modules. There is shown a solar ray 46 directly incident on PV module 1, a solar ray 47 reflected to the PV module, a solar ray 48 reflected to the solar thermal collector, and a solar ray 49 reflected twice and reaching solar thermal collector (note that this ray after being reflected twice would be parallel to the original ray 49). The solar rays 46-48 are reflected onto one of the PV modules 1 and solar thermal collectors 3.

In this embodiment, the reflector 2 comprises reflective surfaces on both faces. By comprising reflective surfaces on both faces, the reflector 2 is operable to reflect incoming solar rays 46-48 onto one of the PV modules 1 and solar thermal collectors 3, while simultaneously reflecting the solar ray 49 onto a different solar thermal collector 3. The solar ray 49 would otherwise have been reflected only once, and overshot both the PV module 1 and the solar thermal collector 3 adjacent to the reflector 2 upon which it was incident. Therefore no energy collection for that ray would have been performed, and therefore the energy from the solar radiation not collected.

Figure 6 shows an alternative example of how the solar thermal collectors 3 can be placed. A reflective curved mirror 6 (e.g. a ‘further reflector’) is placed between the PV module 1 and the solar thermal collector 3. The reflective curved mirror 6 may be parabolic, circular, or have a specifically tailored mathematical formula for the shape. Ideally it may have a shape that will maximize the reflection of solar irradiance on the solar thermal collector 3 (which may be specific to certain parameters in a given system). This arrangement is, ideally, for designs where the solar thermal collectors 3 are not covering the full spacing length 5 between rows of PV modules 1. The curved mirror may be static within the PV system, for example resting on ground supports.

This arrangement can increase the solar thermal energy collection under certain circumstances. For example, when solar rays are incident from a particular direction, the reflective curved mirror 6 may act to focus the incident solar radiation onto the solar thermal collector 3 and thereby provide a collection means for the solar radiation which may otherwise remain uncollected. Here, the solar thermal collector 3 is placed in the space 5 between the PV modules. Many different designs for the solar thermal collectors 3 can be utilized.

Figure 7 shows a further example of how the solar thermal collector arrangement of Figure 6 may be varied to suit a given requirement. In this example, each solar thermal collector 3 is placed within a depression formed by each reflective curved mirror 6. The curved mirror 6 is positioned adjacent the reflector 2. As in Figure 6, the reflective curved mirror 6 may act to focus the incident solar radiation onto the solar thermal collector 3 and thereby provide a collection means for the solar radiation which may otherwise remain uncollected. However in this example the focused incident solar radiation is reflected onto both sides of the solar thermal collector 3, as opposed to a single side. As in Figure 5, the reflector 2 may comprise reflective surfaces on both faces, thereby reflecting incident solar rays from one face onto both the PV module 1 to which it is coupled, and reflecting from the other face incident solar rays onto the curved mirror 6 and/or the thermal collector 3.

In Figure 8, the PV module 1 is inclined (or “sloped”), with the reflector 2 being provided at the raised (e.g. uppermost) end of the PV module 1. Here, the PV module 1 is mounted on a rack 7 and sloped at an optimal angle (which is a common arrangement in many existing solar power stations). The optimal slope to which the PV modules 1 will be attached may, in general, be approximately equal to the latitude at the location. This arrangement can be applied (e.g. retrofitted) to existing power stations, which have already been built (i.e. the reflector system is connected to the uppermost end of the PV module).

Figure 9 shows an alternative arrangement for applying the invention on an inclined PV module 1 with the reflector 2 being provided at the lowermost end of the PV module 1. This arrangement may provide an advantage of saving space in space-limited locations, for example the reflectors 2 may be placed in the spacing region between the PV modules 1, although at a lower effectiveness than the previously described embodiments.

As with the arrangement of Figure 8, the arrangement in Figure 9 can be applied (e.g. retrofitted) to existing power stations. It will of course be appreciated that such a PV system can have many variations of design and that the PV system described herein is simply one example of such a PV system. The arrangement of Figure 9 can be incorporated in PV systems where the optional feature of adding solar thermal collectors is of no interest and/or is not feasible. This arrangement may also be particularly relevant in space limited systems in higher latitudes, with larger PV module slopes.

Figure 10 shows an example of an arrangement that utilizes a smaller type of PV module, which may be referred to as a “small” PV module. The small PV module may comprise an extruded (e.g. aluminium) section 8 containing PV cells 10 encapsulated by, for example, an ethylene vinyl acetate (EVA) layer 11 and an edge sealant 22. A region 9 for the passage of heat transfer fluid to cool down the PV cells 10 may be provided, for example beneath the PV cells 10. The extruded section 8 is designed to be closed (e.g. sealed) with an external glass cover 12. Furthermore, an electrically insulating back sheet (or other layer) with adhesive 23 may bond to the extruded section 8. An outer powder coating layer (not shown) can provide corrosion resistance (alternatively, the section can be anodized). Additional heat transfer fins (not shown) can be incorporated in the extruded section 8.

Advantages include a reduced amount of structural members to support the reflectors against wind loading and a more effective heat transfer, which provides lower module temperatures. Such an arrangement can also be incorporated in designs that utilize the heat from the modules for thermal applications. Such thermal applications may include preheating air surrounding an air source heat pump used for domestic hot water, in an adsorption cooling application, and/or in low temperature heat engines such as those demonstrating an Organic Rankine Cycle (ORC). Many variations are possible for material choices and design modifications. The arrangement in Figure 10 is just an example of the many possibilities of design variations that may be used to implement one or more of the concepts described herein. Another arrangement may involve modules having glass instead of, for example, Tedlar back sheets (i.e. the module being composed of two glass layers with two EVA layers on the inner faces encapsulating PV cells, and where the module is scaled to the required dimensions).

The “small” PV modules may be in the form of a PV module having a small length (in the convention of module length 31 defined in this invention) and an elongate width (e.g. the module may have one cell across the module length and several cells across the module width). The module length 31 may range between approximately 0.1m and 0.2m, depending on the type of PV material used. For example, one typical silicon PV cell is 0.156m x 0.156m, so the small module length 31 in this case would be 0.156m (the edges will increase the size of the module slightly, however, the PV module length 31 is taken as the length of the PV region). Cadmium Telluride (CdTe) - and other suitable thin film technologies - can be scaled to other sizes, thus the module length 31 may be, for example, 0.1m or less. The module width may range between, for example, 0.5m and 2m depending on the design requirements.

Multiple small PV modules can be arranged in a row as with the regular sized PV modules. However, in certain designs, a single small PV module may be long enough to represent one row in a PV system comprising a unitized prefabricated plurality of PV module rows attached as a single unit and operating in unison. A single PV module can also be divided into individual rows in a unitized prefabricated system. An advantage of using small PV modules is that the extra width of reflector 30 required at the ends of a row of PV modules would be reduced as a percentage of the total reflector width. The percentage reduction of extra reflector width 30 required with decreasing module length 31 is similar to the percentage reduction of extra reflector width 30 required with increasing number of modules in a row for larger scale systems involving larger PV modules (e.g. solar power stations).

Figure 11 shows an example of how the tilt angle of a plurality of reflectors 2 can be adjusted in unison in a small module system, such as the module system of Figure 10. An array of modules 1 is attached to a rack 14. The reflectors 2 are hinged to the modules 1, but also comprise gears 17 attached at the edges of the reflectors 2 near the PV modules 1. The tilt angle is adjusted by a common shaft 15 that can be moved into position by an electric motor or actuator. The common shaft 15 passes adjacent a plurality of PV modules 1.

Toothed regions 16 on the shaft 15, adjacent the gears 17 on the reflectors 2, engage with corresponding gears 17. Longitudinal movement of the shaft 15 therefore causes a plurality of reflectors 2 to tilt in unison as the shaft 15 is moved. Therefore if the tilt angle of the reflectors 2 is to be adjusted, all of the reflectors 2 in the small module system of Figure 11 may be adjusted simultaneously. This provides ease of adjustment, as well as complete uniformity of tilt angles. The gears 17 may be designed to comprise of a non-circular profile to optimize the motion profile. Furthermore, electrical connections between the modules 1 can be concealed within the rack, which may serve to protect and preserve the electrical conditions for example in the case of inclement weather or other adverse conditions.

Figure 12 shows a further example of how the tilt angle of a plurality of reflectors 2 can be changed in unison in a PV system, such as described herein. This arrangement involves a common shaft 20 connected to a plurality of reflectors 2 by hinges 21. The hinges 21 are connected to the reflectors 2, but are offset from the hinges 4 which couple each individual PV module 1 to an individual reflector 2. Therefore the longitudinal motion of the shaft 20 causes the reflectors 2 to be rotated about the hinges 4, adjusting the tilt of all connected reflectors 2 simultaneously thereby providing similar advantages as in reference to Figure 11. As will be understood, the shaft 20 will have to move slightly in the vertical direction (i.e. up and down). This movement can be easily provided, for example by a mechanical system connecting the shaft to the actuator.

The shaft linkage can be displaced to position by an electric motor or actuator. Many other types of mechanisms are possible to tilt the reflectors and will be apparent to a person skilled in the art.

Figure 13 shows the angles and other relevant terms used in the equations as disclosed herein. Figure 13 shows the tilt angle 0_r with a positive value. Mathematically, the range of tilt angles would lie in the region (-90° < 0_r < 90°). The operation of the PV system can be achieved by sensors and actuators, which control the PV system to work near the maximum rated power of the PV modules and are at least partially governed by the following equations. Some of equations that describe the operation of the PV system can be derived from the solar irradiance and incidence angle equations.

The angle of incidence θ of beam radiation on a surface can be related by the following equation [Solar Engineering of Thermal Processes. J A Duffie, W A Beckman. Third Edition. John Wiley & Sons, Inc. 2006], cos θ = sin δ sin φ cos β — sin δ cos φ sin β cosy + cos δ cos φ cos β cosgj + cos δ sin φ sin β cosy cos ω + cos δ sin β siny sin ω

Where φ is the latitude, δ is the declination angle, β is the slope of the surface, y is the surface azimuth angle, and ω is the hour angle. The declination angle is given by the following equation.

( 284 + n\ δ = 23.45 sin 360-—

V 365 )

Where n is the day of year.

The zenith angle θ_ζ and the solar azimuth angle y_s are used in the calculations. The zenith angle is given by, θ_ζ = cos^_1(cos φ cos δ cos ω + sin φ sin δ)

And the solar azimuth angle is given by, /cos θ_ζ sin φ — sin δ\ γ_ς = signfG)) cos ¹ --⁷ \ sinO_zcos<p /

The angle of incidence can also be written as, cos θ = cos θ_ζ cos β + sin θ_ζ sin β cos(y_s — y)

The control of the PV system aims to operate the PV modules near their peak power rating capacity, given that the module temperature does not exceed the maximum operating temperature. Adjustments to the tilt angle of the reflector(s) are made to make the total amount of solar radiation incident on the PV modules approach the peak operational radiation intensity of the PV modules. This peak radiation intensity (G_max) is determined in the initial design of the system and the PV module specifications, while taking into account the maximum operating temperature (T_max). For the mainstream PV modules already in the market, the standard test conditions define the peak radiation intensity (e.g. G_max = 1000 W/m²). Mainstream PV modules can operate at slightly higher radiation levels (e.g. G_max = 1200 W/m²) with simple modifications, such as enhancing the passive cooling of the PV module. Maximum operating temperatures are specified by the module manufacturer (e.g. T_max = 85°C). If the operating temperature would be higher than T_max at a radiation level of G_max, then the PV module will be set to operate at a radiation level below G_max that keeps the PV module temperature below ^Tmax· ^A further level of control involves operating at lower power if the demand for electrical power is low in a stand-alone PV system - this can also provide some control of the ratio of electrical power to thermal power in specific applications, which include solar thermal collectors integrated in the PV system.

The PV system can be designed for PV modules that have a slope towards south in the northern hemisphere or towards north in the southern hemisphere. The PV system can also be designed for modules for any surface azimuth angle - it can also be applied in the east west orientation. However, the preferred PV system would be for PV modules facing south in the northern hemisphere (with reflectors attached to the north side of the modules) or facing north in the southern hemisphere (with reflectors attached to the south side of the PV modules). The equations developed here are for horizontal PV modules facing south in the northern hemisphere; nevertheless, they can be easily modified for PV modules of any orientation.

The total beam radiation reaching the PV modules (sum of direct and reflected from mirror) is set by the PV system to be limited by a radiation level G_m given by,

6m ^{— G}max — G_d

Where G_d is the diffuse radiation reaching the PV module - this can be approximated as being the same as the diffuse radiation that would reach the PV module in the absence of reflectors (diffuse radiation blocked by mirror is compensated by diffuse radiation reflected by mirror - assuming a high mirror reflectance and an isotropic sky).

However, further accurate calculations of the exact amount of diffuse radiation reaching the mirror would be incorporated in the equations and in the control system. Further modifications to the equations would also involve taking into account the spectral distribution variation of the solar irradiance at different times. The equations here are simplified; nevertheless, they sufficiently describe the control system involved.

The total beam radiation reaching the modules can be equated by, ^Gm = ^Gb(l + ^Rm^Rb^xe)

Where G_b is the beam radiation on a horizontal surface, R_m is the reflectivity of the mirror, R_b is the ratio of beam radiation on a tilted surface to that on a horizontal surface, and x_e is the effective length ratio of the mirror - the effective length of the mirror 32 is x_el_p - where l_p is the length of the PV module 31 (see Figure 13).

The effective length of the mirror is defined here as the length of the mirror region that reflects incident solar radiation inside the PV module area (Figures 2a, 2b and Figure 3). The effective length ratio x_e is defined here as the effective length of the mirror 32 divided by the length of the PV module 31.

Rearranging the equation for G_m gives,

Substituting the right hand side of the equation with parameter C_n - which can be defined as a parameter related to the required amount of reflected solar irradiance to achieve maximum solar irradiance on the PV module. This gives R_bx_e = C_n and, _c ⁿ R_mVG_b J

The ratio R_b can be calculated by the following equation, cos θ cos(cp — β) cos δ cos ω + sin(cp — β) sin δ

R*³ cos0_z cos φ cos δ cos ω + sin φ sin δ

Alternatively, the equation can be written as,

R_b = cos β + tan θ_ζ sin β cosy_s

Substituting β = h - θ_Γ gives,

R_b = sin 0_r + tan θ_ζ cosy_s cos 0_r

Where θ_Γ is the tilt angle of the reflectors (see Figure 13). The effective length ratio x_e can be equated to the following, cos(6_ze + 20_r) ^X® sin(0_ze + θ_Γ)

Where 6_ze is defined here as an equivalent zenith angle and is given by,

0_ze = tan^-1 (tan θ_ζ cosy_s)

The equivalent zenith angle is defined here as the projection of the zenith angle on the north - south vertical plane. This angle can be related to the pseudo-incidence angle and to the profile angle.

The equation for R_b can be written as,

R_b = sin 0_r + tan 0_ze cos 0_r

Substituting for R_b and x_e into [R_bx_e = C_n] gives, cos(0_ze + 20_r) , sin(fl_zc + θ_Γ) ^(sin θ_Γ + tan θ„ cos 0_r) = C„

This can be simplified to the following equation, cos 20_r — tan 0_ze sin 20_r = C_n

Solving this equation gives the value for the required tilt angle θ_Γ, θ _ i~ ton θ_ζθ + fysec θ_ζθ - C_n\ ^r ^an V J

This gives the tilt angle required to make the PV modules operate at the maximum power rating for a given time.

It can be seen that the maximum value for the parameter C_n is given by,

Cnmax ^ec θ_ζθ

This defines a critical point of the reflected solar power achievable by the mirror. If C_n > C_nmax for a given time then the maximum power of the PV modules can’t be achieved (this typically occurs when solar radiation is very low at times close to sunrise or sunset - requiring a high concentration ratio to attain maximum PV module power). The maximum irradiance that can reach the PV module beyond the critical point G_aiwould be less than the maximum irradiance capacity of the PV module G_m. This would be given by G_ai = G_b(C_nmaxR_m + 1) for positive values of 0_ze, and by G_ai = 2G_b for negative values of 0_ze.

Mathematically speaking, the maximum irradiance that can reach the PV module beyond the critical point would occur at 9_r = -j0_ze - with an effective length ratio x_e = csc(i0_ze)for positive values of 0_ze and would occur at 0_r = - 0_ze with an infinite effective length ratio for negative values of 0_ze - the mathematical range of the mirror length ratio would be x₀ > V2. Small variations of 0_r from the mathematical limits would give close values to G_ai with values of x₀ < 1. It can be shown from the mathematical limits that for x₀ < csc(±0_ze) for positive values of 0_ze and for any x₀ for negative values of 0_ze that the maximum irradiance that can reach the module would occur at x_e = x₀. The mirror length ratio x₀ is defined here as the mirror length divided by the PV module length 31.

The primary limitation to attaining full PV module power is the mirror length ratio x₀ (for designs with x₀ < 1). If the effective length ratio x_e required at a given time to achieve the maximum power exceeds the mirror length ratio x₀, then the tilt angle of the mirror is set at an angle that makes the effective length ratio equal the mirror length ratio (x_e = x₀)· Typical mirror length ratios would be in the range of (x₀ < 1) for practical designs (see Figures 2a, 2b).

The tilt angle required to maximize the power when the limit of x_e = x₀ has been reached can be found by solving the following fourth order equation in sinO_r, sin⁴ 0r + 4 xosin³ 0r + (χθ — 4) sin² 0r — 2x0(sin² 0ze + 1) sin 0_r+ cos² θζθ — χθ sin² 0ze = 0

It can be seen that the operation of the system comprises of two phases. The first is where full PV module power can be achieved (e.g. 1000 W/m²), with x_e < x₀. The second is where the full module power can’t be achieved - in the phase where full module power can’t be achieved, the power is maximized by setting x_e = x₀ (for designs within the normal range of x₀).

A further limitation in the operation of the PV system that may occur at times close to sunrise and sunset is where the reflection from the reflectors may lead to nonuniform irradiance levels on the edge PV modules. As shown in Figure 4, this can be avoided by increasing the reflector width 30 beyond the width of the row of PV modules 1. If the extra reflector 2 width is insufficient (i.e. in space limited situations) then the tilt angle can be altered from optimal to an angle that removes the non-uniform irradiance; alternatively, some minimal non-uniform irradiance can be allowed on the edge PV modules for short periods of time - the edge PV modules with non-uniform irradiance levels will be bypassed by the bypass diodes.

For PV modules that are sloped, the equations can be modified by a simple adjustment - this involves using an artificial latitude in the equations (a latitude that is equivalent to the original latitude reduced by the PV module slope). This would involve substituting the latitude in the equations with the artificial latitude φ - β. Sloped PV modules would have the same angular relationships as a horizontal surface on the artificial latitude. The value of G_b would have to be modified to the irradiance at the sloped PV module, which can be done by using the R_b equation.

Average values of solar irradiance on a horizontal surface are generally known for a given location and are available from the meteorological data. These values are used with a safety factor to determine the tilt angles required if the sensors are not functioning. This provides a fail-safe system that would keep the PV modules within the normal range of operation. A further safety feature would comprise a mechanical system that would operate if there is a fault in the system - this mechanical system would move the reflectors to the largest tilt angle away from the PV modules in the range of motion and set the reflectors in idle mode. Other additional features may comprise the option of the reflectors being operable to cover the PV modules, which would be useful in the case of storms and hail to provide a partial protection for the PV modules; this also provides protection during thunderstorms if a lightning bolt strikes the modules. Further additional features may comprise a cleaning system integrated with the mirror system to automatically clean the PV modules and the reflectors.

The actual values of solar irradiance for a given location can be measured by sensors (e.g. pyranometers and pyrheliometers). The tilt angle is adjusted according to the irradiance data. The control of the system can be achieved by the use of microcontrollers, or by the use of more advanced control units in larger scale projects.

Figure 14 shows an alternative embodiment, wherein the reflector 2 comprises an extendable section 19 that can be moved up or down to increase or decrease the length of the reflective element 2. The extendable section 19, as with the reflector 2, comprises a mirrored surface on at least one face so as to reflect incident solar rays towards the PV module 1. This can be useful in space-limited situations, where there may not be sufficient room for a full-size reflector all the time. Therefore when there is sufficient space, the extendable section 19 may be extended from the reflector 2 to provide a greater area from which to reflect incident solar rays onto the PV module 1. When the extendable section 19 is not required, or when there is not sufficient space, it may be housed within the reflector 2. Such a housing may act so as to prevent damage to the extendable section 19 and provide a compact and efficiently packed arrangement for the system as a whole. The extendable part can be moved by any mechanical system, such as a rail with motor 18. This can be a linear actuator, telescopic actuator, pneumatic actuator, actuator and pulley system, or any other appropriate mechanism.

Figures 15a and 15b show examples of how the height of the reflector 2 can be reduced for tilt angles corresponding to different solar altitude angles. The reflectors 2 are attached by a sliding connection 25 to a curved section 24, which acts like a cam and defines the motion of the reflector 2. The shape of the curved section may vary with specific system parameters such as latitude, regional irradiance levels, and spacing between rows of modules. The shape will mainly take into account the need to reduce the height of the mirror sufficiently to avoid shading PV modules in adjacent rows in space limited situations. Each reflector 2 is operable to slide along the curved track 24 via the sliding connection 25 adjacent each PV module 1, thereby adjusting the tilt angle of the reflector 2 relative to the PV module 1 and/or the ground. The motion can be achieved by actuators, motors, or any other appropriate mechanism.

In Figure 15b, the height of the reflector 2 can be reduced for tilt angles corresponding to low solar altitude angles. The shading behind the PV modules 1 reaches an endpoint 26 behind the PV modules 1. As shown in Figure 15a, shading is minimal for high solar altitude angles. However in Figure 15b, during a low solar altitude angle, the shading reaches a maximum. It can be beneficial to reduce the shading extent in space limited situations; as such shading may overlap other PV modules and hence severely reduce their efficiency. This is just one example of how this can be achieved, and other possible designs may be used. This may include linkage design, several sets of motors, and/or foldable reflectors. Another arrangement for reducing mirror length may involve a mirror that can be folded from its midpoint to reduce the length of the mirror to half the original. This may comprise hinges at the midsection with a mechanical locking system that can fold and unfold the upper half of the mirror and lock it into position. It will be apparent to a skilled person that other arrangements may be used.

Figure 16 shows the system utilizing cold mirrors, which reflect the visible region of the solar spectrum and transmit the infrared region of the solar spectrum. An incident solar ray 51 on the cold mirror 55 may comprise light of many different wavelengths (a variety of wavelength selective transmission and reflection ranges can be tailored in cold mirrors to suit a specific application). A ray 52 with a wavelength in the visible region would be reflected, and hence be incident on a PV module 1 or solar thermal collector 3. However an incident solar ray 51 with a wavelength in the infrared region of the solar spectrum would be transmitted 53 through the mirror. The infrared ray 53 is then incident on a solar thermal collector 3. PV modules 1 are conventionally unable to collect energy from solar radiation in the form of infrared radiation.

PV modules can only convert solar radiation to useful electrical energy when the photon energy is greater than the band gap of the PV material (e.g. 1,1eV for Silicon, 1.4 eV for GaAs). All wavelengths associated with an energy less than the band gap energy would produce no electrical power and will be converted to waste heat in the solar cell. However solar thermal collectors 3 can collect energy at a range of different wavelengths of solar radiation, including both visible and infrared radiation. Therefore for efficiency of collection of energy from solar radiation, the cold mirrors 55 are arranged to reflect visible radiation towards the PV modules 1 and/or the solar thermal collectors 3, whilst infrared radiation which passes through the cold mirrors 55 is incident upon the solar thermal collectors 3 only. The cold mirror film may also reduce heat build-up in the PV modules, which would be beneficial as a higher temperature would generally serve to reduce the performance of PV modules.

Figure 17 shows the system as previously described being applied on an existing single-axis tracking PV system. The reflector 2 tilt angle may be fixed relative to the PV module 1, or may be tilted by an independent mechanical system, or may be tilted by a mechanical system that is linked to a mechanical system that moves the PV modules 1. As previously described, an incident solar ray 71 is reflected (i.e. in the form of a reflected solar ray 72), which is then incident on the PV module 1. The PV module 1 is coupled to a mounting rack 75 as part of a PV tracking system (not shown). The PV tracking system is operable to adjust the tilt angle of the PV module 1 (and/or the tilt angle of the reflector 2) through adjustment of the mounting rack 75 so as to maximise the efficiency of the solar radiation collection system even as the angles of incidence of the solar rays in relation to the ground changes as the sun moves relative to the Earth.

The system can also be applied to existing power stations, and can use reflectors 2 on the north or south side of the PV modules 1. The reflectors 2 can be attached at a fixed optimal tilt angle or can have an adjustable tilt angle. The design incorporating an adjustable mirror tilt angle would have a similar method of operation as a mirror system installed on a non-tracking PV system. A further variation of this design can have the reflector 2 tilt angle adjustment to be connected to the tilting mechanism of the PV modules 1 (the same motor or actuator system that moves the PV modules 1 will be connected to move the reflectors) and can be synchronized by a mechanical system (e.g. linkage or cam) to have an optimally adjusted tilt angle relative to the module tilt angle. The mechanical system can further comprise different adjustable settings that change the motion profile of the reflectors relative to the motion profile of the PV modules 1 to optimize the system for a given time. This can be designed for many tracking systems, including those that are already built. Using the mirror system on a single-axis tracking PV system may enable single axis tracking systems to perform better than dual-axis PV tracking systems that do not utilize reflectors under certain conditions. Depending on the system parameters and the mirror lengths used, such an arrangement can increase the energy collection of a single-axis tracking PV system by approximately 20% to 40%.

Figure 18 shows an example of another variation of the invention being applied to small section designs (e.g. one PV cell across the module length 31). This V-shape arrangement has a PV region 91 covered by an infrared reflecting film 92, connected to a solar thermal collecting region 94 covered by a cold mirror film 95. The PV regions 91 and the solar thermal collecting regions 94 are rigidly attached to each other and are tilted as a single unit about a rotating shaft 93. Electrical wiring and heat transfer tubes can be concealed within the rotating shaft 93. The shaft 93 is connected at the ends to rails that connect the other V-shaped units to form a PV module (alternatively a sufficiently long V-shaped unit can form a single PV module). The solar rays 96 incident on the PV region 91 have their visible portion pass to the PV cells and their infrared portion reflected 98 to the solar thermal collecting region 94. The solar rays 97 incident on the solar collecting thermal region 94 have their infrared portion transmitted to the solar thermal collector and their visible portion reflected 99 to the PV region 91. The PV cells can be designed to handle approximately 1.4 suns or the V-section can be tilted to an angle such that the total solar irradiance received by the PV cells is limited to their maximum capacity.

V-shaped section arrangements may have a PV cell region 91 and a solar thermal collector region 94 attached at a right angle (e.g. 90 degrees) to each other. The V-section may be tracked to be facing the sun (equivalent zenith angle perpendicular to the aperture plane). PV cells in this design can be adapted to handle about 1.4 suns (as the aperture width is V2 times the PV cell region width). If the design is chosen to limit the PV cells to standard irradiance (i.e.1000 W/m²), then the V-section will be set to a tilt angle away from the sun, which reduces the radiation reaching the PV cell region to the required level. A modification to this example may involve a cold mirror film connected to a rotating section that folds and unfolds the film to control the length of the film covering the thermal collector region - this will enable collection of solar power (that would otherwise be uncollected) by the solar thermal collector at tilt angles not facing the sun.

In Figure 19, a foldable cold mirror 95 is attached on a rolling section that enables the film to be folded and unfolded - this changes the length of the film covering the solar thermal collecting region, which increases the total solar irradiance received by the solar thermal collectors. The V-shaped section would be tilted to an angle that reflects the visible light uniformly on the PV cells.

A solar ray 100 is shown incident on a region not covered by the cold mirror film 95 and passing completely to the solar thermal collecting region 94. In an arrangement with a non-foldable cold mirror, the ray 100 would have its visible portion reflected outside the PV module region 91 rather than being collected by the solar thermal region 94. A rotating shaft 101 folds and unfolds the mirror film 95. A secondary rotating shaft 102 with a spring system is shown pulling thin wires attached to the cold mirror film 95 to hold it in position. There is provided a glass cover 103 for the solar thermal region 94 and the PV cell region 91, as well as electrical wire 104 and a heat transfer tube 105.

By using a foldable cold mirror the total solar collection may be increased, especially in a system where the PV region cannot handle 1.4 suns and needs to be tilted to an angle that reduces the total solar irradiance incident on the PV region. The cold mirror unfolded length in this design would be set to equal the effective length ratio.

A foldable cold mirror may involve additional complexity in comparison with a stationary cold mirror. However, this may be justified by the extra energy that may be collected and/or other potential benefits such as the ability to control the ratio of electrical to thermal power generated at different times of the day and year, which may be desirable in certain applications, such as stand-alone systems.

Figure 20 shows an example of a closed unitized system, where a plurality of PV cells 106 and reflectors 2 operate as a single module that produces electrical and thermal power. The arrangement involves a plurality of rows of PV cells 106, where each row has a reflector (e.g. cold mirror) 2 attached on a rotating shaft 4. The PV cells 106 can be Silicon or thin film (e.g. CdTe) and can be scaled to any size required, for example, a PV cell row 106 can have dimensions of (0.05m * 2m) and the module can have, for example, ten rows or more.

Preferably, solar thermal collecting regions are provided between the PV cell rows 106 and compound parabolic collectors (CPC) 107 are utilized, which can be made from any reflective material. The compound parabolic collectors (CPC) 107 concentrate solar radiation onto a receiver 108, which absorbs solar radiation. A transparent sheet 109 covers the receiver 108 and has a thin opening 110 (i.e. slit) for the passage of air.

In this arrangement circulating air transfers the solar thermal energy through insulated conduits 112 to a heat exchange unit on the end of the module (not shown), which can be connected to heat transfer pipes to transfer the energy to a thermal application. The air circulates in a closed loop through the conduits 112 to the heat exchange unit and enters an upper air region 113 at ambient air temperature. The air in the upper air region 113 cools down the heated PV cells 106 and is drawn into the solar thermal region through the openings 110 on the transparent sheets 109. The air is then heated by the receivers 108 and enters the insulated conduits 112 through passages 111. A DC micro air compressor (not shown), which consumes a very small amount of energy, makes the air circulate in the closed loop.

The insulated conduits 112 can be formed by, for example, extruded polystyrene 114, which also forms the passages 111 and provides good thermal insulation. The reflectors 2 may be connected by a shaft (not shown) to tilt them in unison in a similar way to the arrangement in Figure 12. The shaft may be moved by an actuator, which may also be a piezoelectric actuator for this arrangement.

Also shown are a glass cover 116, a back sheet 115, and an aluminium edge section 117, which provides a glass cover seal 118 and a back sheet seal 119.

An advantage of this arrangement is that the heat in the PV cells 106 is, at least in part, collected as thermal energy. Also, the flow of air from the upper air region 113 through the opening 110 in the transparent sheet 109, provides a means of reducing heat dissipation from the solar thermal region back to the PV cells 106 (i.e. heat escaping from the thermal region is recaptured by the flowing air from the upper air region 113 through the opening 110. Another advantage is that the reflectors 2 are protected inside a closed system; hence they can be very thin and without any structural supports.

Figure 21 shows graphs of reflector tilt angles 0_r versus the hour angle ω at selected days of the year. The declination angle δ corresponding to these days is shown on the left of curves (note that the declination angle changes slightly during a day). All angles shown are in degrees. The hour angle changes by 15° per hour - 0° corresponds to solar noon and the curves range from -75° to 75° (7:00 AM to 5:00 PM solar time). The graphs are generated for solar irradiance data in the UAE. Maximum radiation intensity is set at G_max = 1000 W/m². The reflector has a reflectance of 90%, i.e. (R_m = 0.9). The length of the reflector is chosen here as 40% of the module length, i.e. the mirror length ratio is (x₀ = 0.4) and attached on the north side of horizontal modules (with no slope and aligned parallel to the east-west axis, i.e. reflectors facing south).

Figures 22a and 22b show curves of the ratio of the solar irradiance reaching the modules over the maximum irradiance G_max (vertical axis) for varying hour angles (horizontal axis). The solid curves represent irradiance for a system utilizing the mirror system and the dashed curves are for a system without reflectors. The three solid curves and the three dashed curves are for declination angles 23.45°, 0°, and -23.45° from top to bottom (summer solstice, spring-autumn equinox, and winter solstice respectively). Figure 22a shows a system where the mirror length ratio x₀ = 0.4, and Figure 22b shows a system where x₀ = 0.7. Graphs are generated for normalized solar irradiance data in the UAE. Maximum radiation intensity is set at G_max = 1000 W/m². Reflectors have a reflectance of = 0.9. The modules are horizontal and aligned parallel to the east-west axis (i.e. reflectors facing south). Annual increase in solar energy collected by the PV modules is estimated at 28% for x₀ = 0.4 and 37% for x₀ = 0.7. The annual percentage increase in solar energy collected by the PV modules would be higher for higher latitudes, where the solar irradiance is lower, also if the modules are sloped to face south - for the northern hemisphere - (with a slope in the range of half the latitude) this would increase the annual increase in collected solar energy. Under certain circumstances the invention can increase the solar energy collected by ordinary PV modules by about 70%.

The reflector 2 may comprise any suitable reflective material, which has good durability and resistance to the environment of the system. This may include, but is not limited to, aluminium (e.g. treated, enhanced, protected, etc.), mirror glass, cold mirror (as described in reference to Figures 16 and 18, for example 3M cold mirror), and other materials.

For the case of cold mirrors, it provides an advantage of reduced operating temperature of the modules. Figure 16 shows an example design of the system utilizing cold mirrors. Reflectors having a reflective surface such as mirror glass and aluminium can incorporate surface micro or nano structuring and have specific coatings, which enable the reflection of selected wavelength ranges of the electromagnetic spectrum of solar radiation.

Any system feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to system aspects, and vice versa. Furthermore, any, some and/or all features in one aspect can be applied to any, some and/or all features in any other aspect, in any appropriate combination.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and/or supplied and/or used independently.

Claims

1. A concentrator photovoltaic (PV) system, comprising:

at least one PV module having at least one solar cell;

at least one reflector having a reflective surface arranged at a tilt angle configured to reflect solar radiation onto the at least one PV module; and a mechanism for adjusting the tilt angle of the reflective surface; wherein the tilt angle of the reflective surface is adjustable relative to horizontal during operation.

2. The system of Claim 1, wherein the tilt angle of the reflective surface is adjustable both relative to horizontal and to the at least one PV module.

3. The system of Claim 1 or 2, wherein the at least one reflector is moveable relative to the at least one PV module so as to change the tilt angle of the reflective surface.

4. The system of Claim 3, wherein the at least one reflector is arranged to move along a track configured to define, at least in part, a curved path.

5. The system of Claim 3, wherein the at least one reflector is arranged to pivot relative to the at least one PV module, optionally wherein the at least one reflector is attached to a rotatable shaft.

6. The system of any preceding claim, wherein the reflector is attached to the PV module.

7. The system of any preceding claim, wherein the reflective surface is arranged to have a tilt angle in the range of between about 0 to 180 degrees relative to horizontal during operation.

8. The system of any of Claims 1 to 7, wherein the reflective surface is completely planar.

9. The system of any preceding claim, wherein the at least one reflector comprises a plurality of reflectors each having a reflective surface.

10. The system of any preceding claim, wherein the at least one reflector has at least two reflective surfaces, optionally two opposing reflective surfaces, preferably arranged to reflect solar radiation in two directions, for example away from both the front and rear of the reflector.

11. The system of any preceding claim, wherein the at least one reflector has an extendable section having a reflective surface arranged to increase the total surface area of the reflective surface.

12. The system of Claim 11, wherein the extendable section is slidably attached to the at least one reflector, for example such that in a non-extended configuration the extendable section can be stored behind the reflective surface.

13. The system of any preceding claim, wherein the at least one PV module comprises a plurality of PV modules arranged adjacently, for example in a row.

14. The system of any preceding claim, wherein the at least one reflector extends substantially the width of the at least one PV module, preferably such that the reflective surface can reflect solar radiation onto each PV module.

15. The system of any of Claim 14, wherein the at least one reflector is arranged to extend beyond either one, or optionally both, of the outermost PV module(s), preferably so as to reflect solar radiation onto the side of the PV module(s).

16. The system of any preceding claim, wherein the at least one PV module is arranged to be placed directly on the ground during operation.

17. The system of any of Claims 1 to 16, wherein the at least one PV module is arranged to be supported spaced from the ground, optionally wherein the at least one PV module can pivot (or tilt) relative to the ground, for example wherein the at least one PV module is mounted on a raised support.

18. The system of any preceding claim, wherein the at least one PV module is covered, at least in part, by a film arranged to reflect infrared radiation.

19. The system of any preceding claim, wherein the mechanism comprises at least one actuator arranged to change the tilt angle of the reflective surface.

20. The system of any preceding claim, further comprising a controller, optionally a microcontroller, configured to control the tilt angle of the reflective surface, preferably by controlling the at least one actuator.

21. The system of any preceding claim, further comprising at least one sensor arranged to determine at least one of: ambient temperature and the temperature of the at least one PV module.

22. The system of Claim 21, wherein the controller is configured to monitor the temperature of the at least one PV module to determine whether the temperature exceeds a predetermined value, and further to move the at least one reflector upon determining that the predetermined value has been exceeded.

23. The system of Claim 21 or 22, wherein the controller is configured to monitor the rate of change of the temperature of the at least one PV module so as to estimate the desired tilt angle that would give a preferred operating temperature for the at least one PV module.

24. The system of any preceding claim, further comprising at least one sensor arranged to determine the tilt angle of the at least one reflector relative to at least one of: horizontal and the at least one PV module.

25. The system of any preceding claim, further comprising at least one sensor for measuring a power output of the at least one PV module.

26. The system of any preceding claim, further comprising at least one sensor for detecting an amount of solar radiation incident on the at least one PV module.

27. The system of any of Claims 21 to 26, wherein the controller comprises a processor configured to calculate a required tilt angle for the at least one reflector based on at least one of: the power output of the at least one PV module; the amount of solar radiation incident on the at least one PV module; the temperature of the at least one PV module; and the ambient air temperature.

28. The system of Claim 27, wherein the controller is configured to move the at least one reflector to a maximum tilt angle away from the at least one PV module upon detection of a fault in the system, for example wherein the temperature of the at least one PV module exceeds a predetermined value.

29. The system of any of Claims 21 to 28, wherein the controller is configured to move the at least one reflector to a predetermined tilt angle relative to the at least one PV module upon determination that a detected solar irradiance falling on the at least one PV module is below a predetermined value.

30. The system of any preceding claim, wherein the at least one reflector can be moved to a position in which it at least partially covers the at least one PV module, and optionally covers the entire surface of the at least one PV module so as to provide protection.

31. The system of any preceding claim, further comprising at least one solar thermal collector, optionally which is disposed between adjacent PV modules.

32. The system of Claim 31, further comprising at least one further reflector having a reflective surface arranged to reflect solar irradiance onto the at least one solar thermal collector, optionally wherein the at least one further reflector is a static reflector.

33. The system of Claim 32, wherein the reflective surface has a curved profile.

34. A method of optimising the performance of a concentrator photovoltaic system according to any preceding claim, the method comprising:

obtaining at least one input value relating to a parameter associated with the PV module;

determining a desired tilt angle of the reflective surface based on the input value; and adjusting the tilt angle of the reflective surface to the desired tilt angle.

35. The method of Claim 34, wherein the input value is at least one of:

• the solar altitude angle local to the PV module;

• the power output of the at least one PV module;

• the amount of solar radiation incident on the at least one PV module.

• the temperature of the PV module;

• the rate of change of temperature of the PV module;

• ambient temperature; and • the tilt angle of the reflective surface relative to at least one of:

o horizontal;

o vertical; and o the at least one PV module.

36. The method of Claim 34 or 35, wherein the desired tilt angle is dependent on the time of day and/or year local to the PV module.

37. The method of any of Claims 34 to 36, further comprising comparing the input value against a predetermined value, wherein the desired tilt angle of the reflective surface is based on said comparison.

38. The method of any of Claims 37, wherein the input value is the temperature of the PV module and the predetermined value is a maximum operating temperature, such that when the temperature of the PV module approaches the maximum operating temperature, the tilt angle can be adjusted to reduce the amount of reflected solar irradiance on the PV module before it reaches the maximum operating temperature.

39. The method of any of Claims 34 to 38, wherein the input value is a rate of change of temperature of the PV module, the method further comprising using the rate of change of temperature to estimate the desired tilt angle that would give a preferred operating temperature of the PV module.

40. The method of any of Claims 34 to 39, further comprising determining a desired position of the reflector based on at least one of: the power output of the at least one PV module; the amount of solar radiation incident on the at least one PV module; the temperature of the at least one PV module; and the ambient air temperature.

41. The method of any of Claims 34 to 40, wherein the input value is the measured solar irradiance falling on the PV module and the predetermined value is an expected solar irradiance, such that when the measured solar irradiance is below the expected solar irradiance, the desired position of the reflector is a position in which the amount of solar radiation reflected onto the PV module is increased, optionally to a maximum amount possible.

42. An apparatus for use in the system of any preceding claim, comprising:

a first section arranged to support the at least one PV module; and a second section arranged to support the at least one reflector having a reflective surface arranged to reflect solar radiation onto the at least one PV module;

wherein the second section is arranged to be moveable so as to change the tilt angle of the reflective surface relative to horizontal during use.

43. The apparatus of Claim 42, wherein the second section is further arranged to be moveable relative to the first section.

44. The apparatus of Claim 42, wherein the first and second sections are arranged to be fixed at 90 degrees apart.

45. The apparatus of any of Claims 42 to 44, further comprising a rotatable shaft, wherein the housing is attached to the shaft such that rotation of the shaft tilts the housing relative to horizontal.

46. The apparatus of Claim 45, wherein the rotatable shaft is arranged to conceal electrical connections and/or heat transfer pipes concealed within, optionally wherein the shaft is hollow.

47. The apparatus of any of Claims 42 to 46, wherein the first section comprises at least one extruded portion arranged to contain fluid for the transfer of heat away from the at least one PV module.

48. A solar power station incorporating the system, method or apparatus of any

5 preceding claim.

49. A photovoltaic system substantially as described herein and/or as illustrated in the accompanying drawings.

10

50. An apparatus for use in a photovoltaic system substantially as described herein and/or as illustrated in the accompanying drawings.

Intellectual

Property

Office

Application No: GB 1622064.2 Examiner: Jonathan Huws