WO2007028938A1

WO2007028938A1 - Thermal energy system and apparatus

Info

Publication number: WO2007028938A1
Application number: PCT/GB2006/002408
Authority: WO
Inventors: Gurvinder Singh Virk
Original assignee: Endoenergy Systems Ltd
Priority date: 2005-09-07
Filing date: 2006-06-29
Publication date: 2007-03-15
Also published as: EP1931922A1; NZ566780A; GB0518218D0

Abstract

A thermal energy system for heating and/or cooling applications, system having solar collection means for transferring heat energy to and/or from a heat transfer fluid, thermal upgrading means for increasing the thermal energy within the system and thermal storage means. The collection means, upgrading means and storage means are connected so as to allow the transfer of heat therebetween via the heat transfer fluid. Control means is arranged to receive readings of operational variables from the thermal energy system and to process the operational variables using a system model so as to predict future operational variables for the system. The control means controls the flow of the heat transfer fluid around the system based on the predicted operational variables. The collection means may have an outer thermally conductive surface for the reception of solar radiation and one or more formations extending behind the outer surface, the formations being formed integrally with the outer surface and shaped to provide one or more elongate conduits for conveying a heat transfer fluid through the collection means during use.

Description

Thermal Energy System and Apparatus

The present invention relates to thermal energy systems and more particularly to the use of solar assisted heating and cooling systems for meeting thermal energy requirements primarily in buildings.

Solar assisted heating systems in the form of active solar heaters or solar assisted heat pumps are known to be able to provide a useful source of thermal energy. In particular the thermal energy derived from such devices can lead to a significant reduction in carbon dioxide emissions when compared to the use of conventional gas fired systems for space and water heating applications .

A typical solar assisted heating system includes a collector for absorbing solar energy and a heat store for maintaining the absorbed energy in a form which is suitable for use as required. It is a recognised and well documented problem that generally low-grade energy is freely available from the sun and the atmosphere, whilst the heat store is required to store it and provide it for upgrading for space and water heating applications . Hence the provision of an energy converter in the form of a heat pump is generally required to upgrade the energy- for use in for example space heating and hot water applications in domestic, commercial or else industrial premises.

Whilst solar water heating systems have become established as a renewable energy source in some niche markets, the widespread adoption of such systems for heating applications within homes and other buildings has been hampered by a number of problems: The success of solar assisted heating systems is heavily dependent upon installation costs and operating efficiencies . Since operating temperature gradients for such systems are relatively low compared to more conventional gas fired systems, any heat losses during collection, upgrading, delivery or storage can potentially negate the potential energy savings. In particular it is often the case that, when the greatest amount of energy is available from the sun and atmosphere, energy consumption for heating applications is at a minimum. Thus an overriding problem to be solved is how to store the heat from the time the energy is collected to the time it is needed without incurring an unacceptably high loss together with a decrease in temperature, which can in itself render the remaining energy almost worthless .

Traditional solar energy systems tend to maximise the collection temperature by using glazed collectors . However collection systems can also usefully be employed for cooling, wherein the excess energy is dissipated via the collector at the appropriate time, for example, at night when ambient temperature is lower than the system temperature. Thus traditional glazed collectors are not suitable for this dual purpose system which requires both collection and convection. In this regard the applicant has coined the phrase 'collvector' to refer to a collector which independently collects and convects heat energy as required.

To further this problem, a solar assisted system is also heavily dependent on the uncertainty in the climate as well as day to day changes in weather. Thus a solar assisted system does not operate in a steady state and, whilst individual components can be optimised for predefined conditions, such an arrangement will not provide a reliable solution for all year round use. The use of a heat pump poses a further complication, since, within predefined operating limits, the efficiencies of collectors generally decreases with increasing collection temperatures. In contrast the coefficient of performance (COP) of a heat pump is generally inversely proportional to the temperature lift provided by the heat pump. A lower collection temperature requires a greater temperature lift by the heat pump and so there is a constant balance that needs to be struck to maintain suitable operating efficiency.

A similar situation holds in the cooling mode when the hat pump has to be operated to lower the temperature in a low temperature store by transferring energy to a high temperature store. The cooled heat transfer fluid can then be used for cooling applications . Excess heat in the high temperature store can be radiated via the 'collvectors' at the appropriate time (e.g. at night time) to ensure a high coefficient of performance of the heat pump .

Traditional control optimisation strategies have been based on so-called Proportional, Integral, Derivative (PID) control schemes, which have limitations in complex applications. Given the highly non-linear heat transfer processes which occur within the system, there is a need for a suitable control system which can take account of all the above factors.

Keeping all of the above issues in mind, the viability of solar assisted heating and cooling systems will likely be decided based upon a number of commercial and practical factors. More specifically the cost of installing the system must be offset by the cost savings which can be derived from reduced consumption of energy from other sources . Hence, not only the efficiency but also the operating life of the system must be considered in order to provide a suitable solution. < Traditional collection arrangements include a variety of flat plate collectors and metal tubes in glass or plastic collectors . Whilst some copper, aluminium and steel collectors have been developed, such systems must generally be retrofitted to existing roofs and cause an eye sore. Even for newly built houses, the roof must first be constructed and the energy collectors installed thereafter.

The use of water for energy storage can also be impractical in terms of cost and size, since large volumes of water may need to be stored at relatively low temperature in order to provide the required operating efficiency. Both collection and storage are hampered by building regulations which can make conventional systems unusable for a significant percentage of buildings regardless of the emissions and cost savings which can be achieved.

In view of the above factors, the present invention aims to provide an improved solar assisted thermal energy system which overcomes the setbacks of known systems and offers improved cost and operation efficiency.

According to a first aspect of the present invention there is provided a thermal energy system for heating and/ or cooling applications, the thermal energy system having solar collection means for transferring heat energy to a heat transfer fluid, thermal upgrading means for increasing the thermal energy within the system and thermal storage means, the collection means, upgrading means and storage means being connected to allow the transfer of heat therebetween via the heat transfer fluid, the control means arranged to receive readings of operational variables from the thermal energy system and to process the operational variables using a system model so as to predict future operational variables for the system and the control means controlling the flow of the heat transfer fluid around the system based on the predicted operational variables.

The present invention is particularly advantageous in that the predictive nature of the control allows control decisions to be made in advance, thus overcoming the thermal inertia of the system and building and increasing the system efficiency.

Preferably the collection means independently allows both transfer of heat to the heat transfer medium as well as removal of heat energy from the system as necessary. The collection means typically collects heat energy substantially by radiation and conduction and separately transfers heat from the system substantially by convection.

The system model may take the form of a thermal performance model. Typically the operational variables comprise controlled variables and disturbances. Preferably the system model includes both the controlled variables and the disturbances in the model in order to determine the impact of those variables on the system. Controlled variables may include flow rates at various points within the system and the temperature increase provided by way of the thermal upgrading means .

By proactively controlling the flow rates throughout the thermal system, the present invention allows heat transfer fluid to be provided where it is required in advance of an actual demand or else a change to the operating conditions such that the available thermal energy is collected and stored or dissipated more efficiently. Thus the present invention allows for higher grade energy to be stored, reducing the volumes of liquid required to be stored for use. In one embodiment, the system model is provided by way of a generic basic model which adapts to changes in operational variables over time. According to a preferred embodiment, the model is adaptive in that operational variables can be added or removed from the model as required. Thus the accuracy of the model can be tailored to suit specific applications and can take greatest account for variables which are of most impact in a particular locality or for a specific purpose.

According to a preferred embodiment, the system model is maintained on a web server and can be remotely accessed by a user. Typically the web server administers multiple system models such that the user of any of the modelled thermal energy systems can access the model specific to their system.

Typically data for the operating variables is monitored and stored by the control means. Thus the control means may generate a log of the changes in the operational variables over time so as to be able to predict trends in disturbances such as, for example, ambient temperatures and/or occupant behaviour.

Typically the thermal storage means comprise a hot water reservoir, and/or a high temperature store and/or a low temperature store. Typically the high and low temperature stores are respectively connected to one or more heating and cooling units, wherein the controller controls the delivery of heat derived from the thermal collection means to either the hot water reservoir, the high temperature store or the low temperature store. Typically the system includes thermal delivery means, for delivering heat to a hot water system or space heating and/or cooling units.

According to one embodiment, the system comprises one or more valves arranged for the control of flow of the heat transfer medium between any combination of the collection means, the thermal upgrading means and/ or the storage means. Preferably the operation of the valves is controlled by the control means . Typically one or more of the valves takes the form of a three- way valve, which may be either a three-way diverting valve or a three-way mixing valve.

Preferably the system comprises one or more pumps and/or fans to drive the heat transfer fluid around the system. Typically the pump (s) and or fan(s) are under the control of the control means such that the flow rate of the heat transfer fluid can be regulated. One or more further pumps or fans may be provided between the thermal upgrading means and the hot and/ or cold stores . Typically pumps are used to pump heat transfer liquid around the system although fans may be used to blow air through the system or else to cause airflow through the collectors so as to assist in removal of heat from the system as necessary.

Typically the thermal energy system includes one or more temperature sensors. Preferably the temperature sensors measure the temperature of any, or any combination, of the heat transfer medium entering the collection means, the heat transfer medium leaving the collection means, the top and/or bottom of the hot and cold stores, the hot water reservoir and/or the ambient temperature in one or more areas to be heated or cooled. Temperature readings from one or more temperature sensors may be received by the control means. In one embodiment the control means is provided with one or more predetermined or preset temperature values.

In one embodiment the control means compares temperature readings from one or more sensors and/or one or more preset temperature values to determine the required transfer of energy around the system. Preferably the system includes one or more valves and/ or dampers to allow control of the fluid flow around the system.

Preferably the upgrading means comprises a heat pump in fluid communication with any or any combination of the collection means, the high temperature store, the low temperature store and/or the hot water reservoir. Typically the heat pump can do work on the fluid so as to upgrade the thermal energy of the fluid from the collector passing via either the hot water reservoir, the high temperature store or the low temperature store.

Typically heat is transferred from the fluid to any or any combination of the heat pump, the hot water reservoir, the high temperature store and/or the low temperature store by direct means or else by indirect heat exchangers.

According to a further aspect of the present invention there is provided control means for a thermal energy system, the thermal energy system having thermal storage means, solar collection means for transferring heat energy to a heat transfer fluid, and thermal upgrading means for increasing and/or lowering the thermal energy within the system, the collection means, upgrading means and storage means being connected to allow the transfer of heat therebetween via the heat transfer fluid, the control means arranged to receive readings of operational variables from the thermal energy system and to process the operational variables using a system model so as to predict future operational variables for the system and the control means controlling the flow of the heat transfer medium around the system based on the predicted operational variables. According to a further aspect of the present invention there is provided, solar collection means for a thermal energy system, said collection means having an outer thermally conductive surface for the reception of solar radiation, wherein said collection means has one or more formations extending behind the outer surface, the formations being formed integrally with the outer surface and shaped to provide one or more elongate conduits for conveying a heat transfer fluid through the collection means during use.

Thus the collector can be made of a single piece construction, allowing reduced manufacturing time and material costs. In addition the integrally formed conduit avoids the thermal discontinuity which occurs at the join between adjacent parts, thus improving conduction of heat to the transfer fluid. Thus the outer surface and the formations are formed as a single thermally conductive unit.

Preferably the collection means operates in a first collection mode when the transferring heat energy to the system and a second dissipation mode in which the collector transfers heat from the system when the ambient temperature is lower than the temperature within the system.

Preferably the outer surface and formations have a substantially constant cross sectional profile along their length and in one embodiment the outer surface and the one or more formations are integrally formed by extrusion. In one embodiment, the entire collection means is extruded. The present invention is particularly advantageous in that an extruded collector member can be formed continuously and cut to the required lengths for installation. The formations extend along the length of the member and thus provide structural strength. Typically the collection means has a fluid inlet and outlet and one or more elongate conduits in fluid communication therebetween. The conduits may share a thermally conductive surface via which heat energy can be transferred to and/or from the fluid as it flows along said channels. Typically the collector- is an endothermic collector for receiving solar energy and/or thermal energy from the surrounding environment. The collection means can also be used as a convector in the cooling mode when it is used for dissipating excess heat stored in the thermal system into the surroundings, particularly during nighttime.

The energy harvest from the collection means can be optimised since heat absorbed by the thermally conductive surface from outside of the collector member is conducted straight to the channels . This is also the case when heat is dissipated from the system.

According to one embodiment the inlet and outlet are provided at the same end of the collection means such that the or each conduit is shaped to convey fluid initially in a first direction away from the first end and subsequently in a second opposing direction. In this embodiment the conduit may be U-shaped. Alternatively the conduit may make multiple passes back and forth in a snake like manner.

In an alternative embodiment, the inlet and outlet may be arranged at opposing ends of the collection means. Multiple conduits may be arranged in a side by side orientation so as to form a row of conduits. In this embodiment, multiple conduits may be fed by a single inlet and outlet. In one embodiment the conduits are spaced by the formations such that the conduits and formations therebetween substantially cover an inner side of the conductive surface.

The number, size and shape of the conduits can be adapted for optimal heat transfer at operational flow rates which cause minimal pressure drop along the length of the conduits. The internal surface of the or each conduit may be profiled so as to increase the surface area for conduction. In one embodiment, the conduits are substantially circular in cross section.

Typically the first outer surface is separated from a second opposing surface by the one or more formations. The formations may form internal voids or channels, which may run substantially parallel with the conduits. The provision of voids formed integrally with the conduits allows weight saving and advantageously provides air filled sections which serve to provide insulation around the conduits, avoiding unwanted conduction of heat away from the conduits . Alternatively the air voids can themselves be used for heat collection by circulating air as a heat transfer fluid. The formations may take the form of partitions or internal walls defining the voids and conduits.

This avoids complicated and expensive fabrication of the collectors for sealing and installation of plumbing fittings.

The first and second surfaces may be flat or curved in profile or else may take another appropriate shape. The outer surface may be adapted from an aesthetic viewpoint to better blend in with the surrounding built environment. Typically the first exposed surface of the collection means is curved to form one or more peaks and troughs running along the length of the collection means. The collections means may therefore take the appearance of a conventional roof for a house and may replace a conventional roof.

The formations may be substantially perpendicular to the first and/or second surfaces or else may extend obliquely therebetween. In one embodiment, the outer surface, the second surface and the formations are formed integrally and may be made of aluminium. Alternatively the second surface may be formed of a different material to the first surface and may be attached to the formations. The second surface may be made of an insulating material. Additionally the discontinuity formed between the formations and the second surface inhibits conduction of heat away from the conduits.

Preferably the collection means comprises one or more connection members . The connection members may be provided at a peripheral edge of the collection means and in one embodiment the connection members extend along one or more sides of the collection means. The connection members may include an abutment portion and may take the form of an elongate groove or recess. Typically the connection members extend from either the first or second surface. Preferably, the collection member is provided with two sets of opposing connection members on opposing sides of the member.

According to a preferred embodiment, two or more collection means may be provided in a side by side arrangement and connected together by way of the connection formations to form a collector. When connected along opposing sides, preferably the connection members of the adjacent collection members engage such that the outer surfaces of the adjacent collection means form a substantially continuous collector surface. In this manner a collector covering a required area, such as for example the roof of a building, can be constructed out of a number of interconnected collection members.

Thus the collector of the present invention can replace a conventional roof and in a manner which blends in with other buildings in the vicinity. The collector may also form the outer covering of the building facade or be a free standing structural installation.

Preferably the collection means is provided with locating means. Typically the locating means take the form of a slot or recess or else a leg portion. Typically the locating means are associated with the opposing surface of the collection means and may form an extension therefrom or else a discontinuity therein. The location means may take the form of an elongate recess. The recess may have an opening which is of reduced dimensions so as to provide a neck portion. Thus a bolt head may be received in the recess so as to constrain movement of the collection means. Typically the second surface provides a backing to the collection means arranged for attachment to a building frame.

Preferably the formations are shaped to provide either or both of the connection members and the locating means such that they are integral with the collection means.

Typically the exterior of the collection means is matt in texture and may be coated using a powder coating and/or roughened, or otherwise treated to increase absorption of light rays. In one embodiment the outer surface of the collection means is provided with nano-particles. The nano-particles may be provided as nano crystals of predetermined dimensions so as to absorb light rays within a specific range of wavelengths. According to a further aspect of the present invention, there is provided a solar collector for a thermal energy system, the collector comprising a plurality of collector panels, the panels having locating means for attachment of the panels to a building and connection means for connection of each panel to an adjacent panel, each panel having an outer surface and one or more formations extending behind the outer surface, the formations being formed integrally with the outer surface and shaped to provide one or more elongate conduits for conveying a heat transfer fluid through the collector panels during use.

Typically each collector/convector panel is connectable to an adjacent collector/convector panel to form the solar collector with a substantially continuous outer surface comprising the joined outer surfaces of each of the collector panels.

Specific embodiments of the present invention will be described in further detail below in relation to the accompanying drawings, of which:

Figure 1 shows a schematic of a thermal energy system and associated control means according to the present invention;

Figure 2 shows one arrangement of a thermal energy system according to the present invention;

Figures 3a-d shows a sectional views of collection means according to a first embodiment of the present invention;

Figures 4a and b show two further embodiments of a collection means according to the present invention;

Figures 5a-e show the collection means of figure 4a during various stages of fabrication; and, Figures 6a and 6b show two aligned collector members for use.

Turning firstly to figure 1 , there is shown a system level schematic of a thermal energy system and control means according to the present invention, which provides for the supply of heating, cooling and hot water within a domestic environment.

The system generally comprises a premises 2, such as a house or commercial property, which is subjected to climatic conditions and within which there is a need for hot water, heating and possibly cooling at the demand of one or more occupants.

The house includes a thermal energy system 3 according to the present invention. The thermal energy system 3 has a number of sensors as will be described in further detail below. The sensors generate readings 4, such as temperature readings from rooms within the premises and temperatures at various points within the system 3, which are sent as a data output 5 to control means 6 which comprises a system model.

The control means 6 is typically provided at a remote location on a server which, in one embodiment, can be accessed by the internet. The data output 5 can be sent and received automatically and a user can access the predictive model online using suitable interface software. The control means 6 monitors the operation of the thermal energy system via the system model and provides instructions in the form of control data 8 back to the thermal energy system to affect the operation of the system. The system model according to the present invention is predictive in that it receives current data from the premises 2 and generates control data based on a prediction of the operational variables at some point in the future. A number of variables affect the operation of the system 3. The variables which can be controlled by the control means 6 are referred to as control variables, whilst the variables which cannot be controlled are referred to as disturbances, all of which are included within the model. Disturbances may include the climate as well as the associated impact on temperatures within the premises and also the behaviour of occupants.

These predicted values are then used to determine what control instructions are required to meet the demands on the system made by the occupant.

The system model is provided initially by way of a generic adaptive model which can change over time in response to the data received from the thermal energy system 3 in question. Therefore the system model becomes suited to the operation of a specific thermal system 3 and so the model for one system may, and likely will, differ from the model for another system. In this way the initial generic model undergoes the stages of learning, adapting, tuning and finally prediction to a high level of accuracy as the model converges to actual system parameters.

The control means stores the data received from the system such that a log or history is built up over time. Trends in the variations of the disturbances are recognised. In this manner the model learns for example the behaviour of the occupants and the trends in temperature change as a result of climate.

The model therefore adapts to the changes which occur. As data values are logged, a data plane is generated as a reference for comparison with future values. When new data falls within the existing data plane then there is no new information for refinement of the model, but when received data falls outside the existing data plane, the model adapts to inclide those new- features .

All variables are accounted for within the system model and may be of greater or lesser significance dependent on their influence on the operation of the system. The control means receives data output from the system as data values at a time ^ct\ The system model then approximates the operation of the system as a function of the operational variables, which can be represented generally as :

f{ T1_t> T2_t, T3_t ... Tx_t, F1_t ... Fx_r .. }

where Tl -Tx are values of temperatures at various points within the premises and the system as shown in figure 2, and Fl -Fx are values of flow rate of one or more heat transfer fluids within the system. Further variables, which appear within the model are omitted for the sake of clarity.

The system model then predicts the future values for the operational variables at time t+Δt using time advancing techniques . Initial predicted values of incremental changes in the operational variables are provided which are then processed to generate a statistical error values. The residuals are used to correct the predicted values and the corrected values are processed to generate further statistical error values which are again fed back in an iterative loop . The iterative steps are repeated until predicted values are obtained for which the error value is within an acceptable range. Thus the processing of the received data values in this way generates predictions for the operational variables which converge towards final predicted values with an acceptable level of accuracy. The time step Δt thus provides for a single step prediction which allows the model to provide proactive instructions for the control of the system. By applying the technique to multiple steps, the model can build up predictions further into the future to take account for a number of minutes, hours, days or weeks, using so-called 'k-step' ahead prediction.

Turning now to figure 2, further details of the thermal energy system 3 are shown including the control variables. The system 3 generally comprises an energy collection system, an energy upgrading system and an energy delivery system.

When used in a heating mode, the energy collection system can freely harvest the available thermal and solar energy from the environment by way of collection means 10 which are described in further detail below in relation to figures 3 to 6. In addition the system can be operated in a cooling mode to allow heat energy to be actively transferred to the environment.

Within figure 2, heat transfer fluid in the form of a propylene- glycol/water mixture is pumped through the collectors by pump 36. The heat transfer fluid can also be provided with nanoparticles in order to improve its heat transfer properties . The transfer fluid is drawn from two collector arrangements through a single conduit 38 by way of three-way mixing valve 40. The two collector arrangements 10 are provided on opposing sides of a roof and each collector 10 typically comprises a number of collection means in the form of interconnected collector panels as described in further detail below.

The three-way mixing valve 40 allows heat transfer fluid to be pumped from collectors 10 on a first and second side of the roof either independently or else in unison. The fluid then passes along the conduit 38 to a three way diverting valve 42, from where the fluid can be directed to the hot water cylinder 44 or else to the cold 48 or hot 50 stores via conduit 46. The hot water cylinder has indirect heat exchangers 45 for transferring heat from the fluid from the collectors 10 to water for use within the building. Once it has passed through the heat exchangers, the transfer fluid can pass straight back to the collectors along conduit 52.

If the transfer fluid is directed away from the hot water unit by valve 42 then it passes along conduit 46 to another diverting valve 54 which diverts fluid to either the hot 50 or cold 48 stores depending on the temperature of the fluid. The transfer fluid passes through indirect heat exchangers 51 , 49 within either the hot or cold stores and is then passed back to the collectors along conduit 56 or 58, respectively. The hot and cold stores provide thermal reservoirs for space heating and cooling systems .

Within the hot store 50, heat is transferred to heating delivery system 60 via heat exchangers 61. A pump 62 for the heating delivery system pumps hot water through the heating delivery system to one or more heating units and back to the hot store in a closed circuit. In a similar manner, a cooling delivery circuit 66 passes through indirect heat exchangers 67 in the cold store 48 and provides a closed loop to one or more cooling units 68 by way of pump 70. A number of heating units 64 and cooling units 68 may be provided at various locations within a building such that the system can provide simultaneous heating and cooling in different locations.

In conjunction with the hot water system and the hot and cold stores, an energy upgrading system is provided to upgrade low grade thermal energy to useful temperatures for space heating and cooling and for hot water. The energy upgrading system includes a heat pump 72 which is thermally connected to each of the hot water cylinder 44, the hot store 50 and the cold store 48. The heat pump uses the cold storage tank's medium as a heat source for its own low temperature side. The heat pump allows heat energy to be transferred between the cold store and the hot store or the hot water reservoir so as to effectively further heat the hot stores and cool the cold store. This results in what is referred to as a solar-assisted heat pump based system. In this regard, the cold store is connected to the evaporator side of the heat pump, whilst the hot store and hot water cylinder are connected to the condenser side.

A closed loop is provided between heat exchangers 74 in the cold store 48 and heat exchangers 76 in the heat pump such that fluid can be driven as necessary around the closed loop by pump 78. A separate system through the heat pump is provided for the hot water cylinder 44 and hot store 50 which is driven by pump 80. In this system indirect heat exchangers 82, 83 and 84 are provided in each of the hot water cylinder, the hot store and the heat pump respectively, each of the heat exchangers being connected by diverting valve 86. Direct flow of the heat transfer fluid can also be used if the entire system is provided with the same level of water/glycerol fluid.

Thus thermal energy can be pumped from the hot water cylinder 44 via conduit 88 to be upgraded by passing through the heat pump 72. Upon leaving the heat pump, heated fluid can then be delivered back to the hot water cylinder 44 or else to the hot store 50 by operation of three-way diverting valve 86. Once the fluid has passed through the heat exchangers 83 in the hot store, it may be passed back to the heat pump or else delivered back to the collectors 10 as necessary. The heat pump 72 is provided with a heater 90 to be used as a backup heater for supplementing the heat delivered by the collectors 10. In particular the back up heater provides thermal energy when the cold store is too cold. The backup heater 90 may take the form of any conventional heater which may be directly connected to the heat pump 72 or else may deliver heat by indirect heat exchangers. Auxilliary heating may be provided by fuel burning furnaces or electric heaters.

The pumps 36, 62, 70, 78 and 80 as well as the valves 40, 42, 54 and 86 can all be operated by a control means . The energy collected is then transferred to the hot water cylinder, the hot store or the cold store in that order of priority under the control of the control means. The control logic is governed by temperature readings from temperature sensors located throughout the system as follows:

Tl - temperature of heat transfer fluid upon entry into the roof prior to entering collectors 10 T2 - temperature of heat transfer fluid leaving collector on first side of the roof T3 - temperature of heat transfer fluid leaving collector on second side of roof

T4 - temperature of heat transfer fluid passing along conduit 36 T5 — temperature of water in hot water cylinder 44 T6 — top hot store temperature 50 T7 — bottom hot store temperature 50 T8 — top cold store temperature 48 T9 - bottom cold store temperature 48 Tl O - actual air temperature in cooled room TH - actual air temperature in heated room

TC — minimum preset operating temperature for the cold store TH - preset temperature for hot store The suffix 'S' added to any of the above temperatures means a preset value for that temperature.

The valves 40, 42, 54 and 86 can each be switching or mixing valves and each have operating conditions 0, 1 and 2 as shown in figure 2 in which they can allow no flow, or else flow from direction 1 or 2 (for switching valves) . Alternatively for mixing valves, a mixed flow through 1 and 2 can be provided.

Hysteresis values H5, H6, H9, Hl O and HH in the range of 2- 5°C are set for each of the respective hot water cylinder, hot and cold stores and cooled and heated rooms. Taking the above values, a set of basic rules defining the reactive control logic for the system, when used in a heating mode, is as follows:

IF T2>T1 OR T3>T1 , THEN pump 36 ON

IF T2>T3 + 5° THEN valve 40 = 1 (collect from one side only AND select pump 36 speed)

ELSE IF | T2-T3 | < 5 THEN valve 40 = 1 ,2 (collect and mix from both sides so T4=T2=T3)

Priority 1 : roof to hot water cylinder 44 IF T4>T5 then valve 42 = 1

Priority 2: Roof to Hot store 50

IF T4<T5 OR (T5 > = T5S) THEN valve 42 = 2

Priority 3 : Roof to cold store 48

IF T4<T6 THEN valve 53 = 2

IF T4<T8 THEN pump 36 OFF The control logic for the operation of the heat pump is as follows:

Priority 1: Cold store to hot water cylinder IF T5<(T5S - H5) THEN valve 86 = 1

IF T8>TC THEN heat pump ON (pumps 78 and 80 ON) ELSE IF T8<=TC then heater 90 ON AND heat pump ON

Priority 2: Cold store to Hot store

IF T5>=T5S THEN valve 86 = 2

IF T6<(TH - H6) AND T8>TC THEN heat pump ON (pumps 78 and 80 and COMP ON)

IF T6<(TH - H6) AND T8<=TC THEN heater 90 ON AND heat pump ON

IF T6 >=TH THEN heat pump OFF

The control logic for the operation of heating and cooling is as follows:

IF T10<(T10S - HlO) AND T6>(T6S-H6) THEN pump 62 ON (heating ON)

IF T11>(T11S+H11) AND T9 <(T9S+H9) THEN pump 70 ON (Cooling ON)

This control strategy forms the basic operation of the system in the heating mode which is used to determine how the pumps and valves should be operated in accordance with temperature readings around the system. In the heating mode solar radiation is therefore used as a source of heat energy which is transferred to the system via the collector 10. The heat energy within the system is upgraded using the heat pump to ensure that the hot store is sufficiently hot and the cold store is sufficiently cold. In the heating mode it is important that the cold store actually receives low grade heat energy (i.e. it is heated to some extent) in order to ensure that the temperature gradient between the hot and cold stores is sufficient to allow the heat pump to operate efficiently. If the cold store is too cold then the efficiency of the heat pump will diminish.

Conversely the thermal energy system of figure 2 is also operable in a cooling mode. In this mode, the system is operated to reject excess heat from the hot store in order to maintain the required thermal gradient for efficient operation of the heat pump. In order to achieve this, the heat transfer fluid is pumped between the hot store and the collectors when ambient conditions allow heat to be transferred from the collectors to the surrounding environment.

This can efficiently be achieved during the night when ambient temperatures are at their lowest and also when there is little or no solar radiation. It is also possible to achieve the required cooling capacity during the daytime when the inlet temperature of the collector fluid is sufficiently higher than ambient temperatures. The side of the roof which is shaded from the sun's rays can usefully be employed in this regard. In such a cooling mode the warm side of the heat pump can be connected to the collector inlet and the cold side to the cold store 48.

In accordance with the present invention, predicted future or time advanced values of temperature can be substituted in place of the temperature readings in order to determine predictive control schemes . In addition the intelligent control aspect of the invention allows account to be given to occupier behaviour such that likely demands for heating, cooling or hot water can be pre-empted such that the required energy stores can be supplemented in advance.

Whilst the control aspect according to the present invention is described above in some detail, it is to be understood that alternative advanced control methods could be generated using known techniques of model-based control, neural network based control and/or fuzzy logic control.

These methods are similar in that they allow control of the system by studying the energy requirements for space heating, cooling and hot water, the amount of collected heat over time, the weather patterns and the performance of the endothermic system and developing appropriate models and control laws using neural networks, intelligent decision making and fuzzy logic strategies. In addition different scenarios of use have been proposed to improve efficiency of the system at different times of the year.

In a winter scenario, such as during the period between 01 January to 31 March, the inlet temperature in the collectors can be adjusted so that losses from the collector members are minimised. In this instance the outlet temperature T2 or T3 will not be lower than the inlet temperature. In practice this behaviour would only be achieved if the collector fluid is circulated through the collector only and not through the accumulator tank when irradiation is too low, such as at night time. Thus the collectors will reach an equilibrium temperature with the surroundings and no heat would be lost to the ambient. In addition no heat is lost from the stores through the collector and only a small amount of fluid (i.e. within the collectors) will need to be heated by the first rays of sun. In a summer scenario it is possible to use the collector panels to heat tap water as well as for passive cooling during night time. In the cooling case the inlet temperature of the collector at Tl is set to 25⁰C. Any surplus temperature that the collector fluid is able to store may be supplied to a seasonal storage such as a borehole or ground coils. The temperature of the fluid entering the collector in this mode may be set to 15⁰C.

In the case that irradiation of the collector 10 is inadequate, which may well be the case for a portion of each year, a complementary heat source may be provided. This may be due to limited solar irradiation during peak heating months, which is possible in many regions due to short sunlight hours and the sun standing low over the horizon. In addition, peak demand for heating in winter or cooling in summer may simply be too great to be met by the collector alone. Such a hybrid system may make use of an auxiliary renewable source or else a primary energy source to provide additional heating at the heater 90.

Heat sources may comprise a standard type liquid to air fin-coil unit, connected to the collector fluid circuit either directly with the heat pump or via the thermal storage tank. A fin-coil unit will operate a significantly lower temperature level of outgoing fluid than the solar collectors . Thus the fin— coil battery will decide the operating temperature of the low temperature side of the circuitry.

Additionally a close-to-surface ground collector or else a bore hole collector could provide an auxiliary heat source in a hybrid system. Bore holes drilled to a depth of 50-20Om with a U- shaped collector hose inserted into the bore hole will allow heat to be taken from the ground solids and water in the region of the bore hole. The collector hose can be connected either directly to the low temperature side of the heat pump or indirectly via the cold store. Since the cold store decides the operating temperature of the solar collectors, it may be necessary to monitor and control direct connection of a bore hole collector with the cold store to ensure that the bore hole does not cool the cold store.

Close to surface ground collectors at 1 -3 metres depth could utilise solar irradiation stored in the soil and will thus vary according to solar irradiation but with a time delay compared to the solar collectors.

In the case of primary energy sources, a fuel burning furnace or an electric heater can be connected to the high temperature store. Electric heaters can operate with high efficiency at relatively low temperatures which are suitable for a distribution system according to the present invention. To avoid condensation of exhaust gases and maintain a reasonable efficiency of a furnace, a fuel burning distribution system has to operate at temperatures which are significantly higher than the low temperature distribution system of the present invention. This may be solved by shunting but the effect on the efficiency of the heat pump will also need to be controlled.

Turning now to figures 3a-c, a first embodiment of a collection means according to the present invention is shown. Figure 3a shows a cross section through the collection means which takes the form of collector panel 100.

The panel 100 is formed as a single piece aluminium extrusion with a curved outer surface 102. The cross sectional profile of the extrusion is such that a number of formations 104 are formed behind the outer surface so as to provide an series of cavities or voids 106. It will be appreciated that, by virtue of the extrusion process, the cavities 106 and the formations 104, which serve as cavity walls, are elongate in form such that the cavities extend substantially along the length of the panel 100. Thus the cross-sectional profile is generally constant along the panel.

The cavities 106 are filled with air. However the extrusion profile is shaped such that the formations also form one or more conduits 108 which are substantially circular in profile. These are used for the heat transfer fluid and allow standard fittings to be attached as well as other special fittings for circulation of the heat transfer fluid. Given that the fabrication costs make up the substantial part of the total cost of the collector, the provision of an integral circular conduit is particularly advantageous since it avoids the need for any additional fabrication steps to allow connection of the collector to exiting pipework.

The conduits are provided with a profiled interior surface which has a series of peaks and troughs around the circumference. The cavities 106 are of irregular shape, which serve to reduce the amount of aluminium used within the panel 100 whilst still retaining sufficient structural strength.

Along one edge of the panel, a connection member is provided in the form of a groove or lip 110. The lip 1 10 extends from the outer surface 110 and is offset at a slight angle therefrom. The opposing edge of the panel is shaped to provide a corresponding connection formation in the form of a slot 112 behind the outer surface. The slot 112 has an opening which is shaped to constrain the lip 1 10 of an adjacent panel within the slot 1 12. Thus the panels cannot be easily pulled apart once aligned in the same plane.

The panel also comprises a second surface which opposes the outer surface and which provides a base 114. The base 114 is of reduced width compared to the outer surface 102. A conduit inlet 116 and/or outlet 118 extends through the base at an end of the panel to allow for flow into and from the one or more conduits 1 18.

Each edge of the base 114 is provided with locating means 120 which takes the form of an elongate recess formed within the opposing surface of the panel. The recesses 120 therefore face away from the outer surface 102 and have a narrow opening which leads into a wider recess portion. The recesses 120 are generally rectangular in shape and extend along the length of the panels . As shown in figure 2a the each recess 120 is shaped to receive a bolt head 122 such that the shank 124 extends through the narrower neck portion.

When installing the plank on a roof support 126, one or more bolts are provided with the head 122 protruding from the support 126 as shown. The recesses 120 may then be aligned with the bolt heads 122 and the panel can slide into place. The bolts can then be tightened via nuts 128 so as to lock down the panel in place.

Whilst the base 114 in figure 3 is shown as being integrally formed by extrusion with the remainder of the collector, it is possible that the base could be formed separately. In such an arrangement, the base may be formed of a different material to the outer surface. One embodiment in particular makes use of a base which is a polymer and which is preformed with grooves for reception of the ends of one or more formations. The simple insertion of the formations within slots in a polymer base is not normally sufficient to bond the base with the collector.

In this regard a manufacturing method can be used which involves the deformation of the base using a roller after the formations have been inserted in the respective slots. Rolling the base in this manner causes the base to grip the formations within the slots so as to adequately secure the base and collector in place for use. The deformation process is aided if multiple parallel slots are provided in the upper surface of the base so as to allow correct deformation upon rolling.

Figure 3B shows two panels 100 arranged in a side-by-side arrangement for use. It can be seen that the lip 110 of one panel is engaged in the slot 1 12 of the adjacent panel. This is achieved by insertion of the lip into an end of the slot 1 12. A shown in figure 2b one panel could then be slid in a direction towards or away from the page until the two panels are aligned. Typically one panel will be fixed in place prior to installation of the adjacent panel.

Once in place the adjacent panel can be bolted down and a further panel can be added. This process can be repeated in order to cover an entire roof area so as to form a continuous outer collector surface with a series of conduits running therebehind.

Figure 3c shows a cross section of a support 126 which may be provided for location of the panels and the plumbing needed for the heat collection. The support may be elongate in the form of a beam and includes a lower support 130 which is provided with bore holes 132 which can be used to attach the beam to the frame of a house. The beam includes a locating member 134 which includes further bores through which bolts 122 pass. The bores may be threaded to securely hold the bolts at the required position.

Disposed between the support 130 and the locating member 134 are conduits 136. Two conduits 136 are provided in a parallel arrangement. The conduits include one or more ports 138 which allow liquid to flow in or out of the conduits. The ports 138 correspond to the inlets 116 and/or outlets 118 of the conduits 108 within the panels 100. The conduits 136 in the beams 126 may run perpendicular to the conduits 108 in the panel such that one conduit 136 can serve as an inlet for one or else a series of panel conduits 108. Similarly, the second conduit 136 may serve as an outlet for the panel conduits 108.

It will be appreciated that this arrangement is flexible in that the beam can be provided with ports in varying arrangements. Thus a single conduit 108 within the panel can be provided with an inlet at one end and an outlet at the opposing end. A number of conduits can then be fed by a single common feed conduit in the beam 126.

In addition to the liquid heat transfer fluid flowing through the conduits 108, the air cavities or voids 106 can also be put to good use to improve the efficiency of the collector. The air within the voids 106 when stationary acts to substantially insulate the conduits 108. Additionally, when the collector is in the cooling mode, air can be moved along the voids 106 using a fan in order to improve convection of heat away from the heat transfer liquid.

In a further embodiment, the flow of air through the collectors can be used to provide an additional or else alternative heating capability. As shown in figure 5d, air is circulated through the collector 10 by a fan, such that warm air exits the collector and passes along conduit 140 towards the heat exchanger 142. The heat energy from the warm air is exchanged to a liquid transfer fluid which is pumped by pump 144 to the cold store 48. As has been described above, the cold store is connected to the heat pump 72 and hot store 50 so as to allow upgrading of the heat energy in the system for heating or cooling applications.

An alternative embodiment of the 'collvector' according to the present invention is shown in figure 4a. This shows a cross sectional profile of a flat collection means 12 and figure 4b shows a cross sectional profile of a curved collector means 14. Other roof tile shapes can also be catered for by providing a collector with an outer surface of the required shape. Each collection means takes the form of a panel and includes a first 16 and a second 18 surface. The surfaces are separated by a predetermined distance and extend in a generally parallel arrangement such that the gap between the surfaces is substantially constant over the area of the surfaces.

Internal formations take the form of partitions or fins 20 and extend between the first and second surfaces to define a series of channels or conduits 22 running side by side along the length of the member. The partitions 20 are substantially perpendicular to each of the first 16 and second 18 surfaces forming conduits 22 which are generally quadrilateral in cross section. For the flat collector 12, the conduit cross section is rectangular, whilst the curved collector 14 conduits are generally trapezoidal.

During use the first surface 16 functions as a solar collecting surface and the conduits 22 allow for flow of a heat transfer fluid which is pumped or blown through the collector panels.

Location means in the form of legs 24 extend from the second surface of the collector member. The free end of each leg 24 is bent to provide a foot portion 26 capable of supporting the collector member a distance above a supporting member during use. The fabrication of the collector 10 will now be described in relation to figures 5a-d. Figure 4a shows a flat aluminium collection means 12 which has been extruded with a cross sectional profile as shown in figure 4a. The extruded panel 12, which is generally planar in form is then cut to the required length, which may be altered as necessary but which is likely to be in the range of 0.2-6m.

Each member is extruded in one or more sections with integral connection members 28 at each side thereof which run along the length of the member. The connection members 28 include a portion which extends from one of the first or second surfaces and a further portion which is disposed at an angle thereto, forming an L-shaped projection. The L-shaped projection creates a trough or gulley adjacent the outermost channel of the member. As can be seen in figure 3a, a pair of offset troughs are provided at each side of the member, separated by an outermost partition 30, such that a first trough extends to a first side of the partition 30 and a second trough extends to the opposite side of the partition. The troughs are disposed at different heights so as to form a dual locking arrangement.

The opposing side of the extruded member has similar but inverted trough formations.

According to another arrangement, which is in many ways preferred, the collector member can be extruded in two or more sections . In the case of two sections, a first section can be extruded for the first surface and the upper portion of the partitions, with a second section being extruded for the remainder of the collector member. In this manner a flow diverting means in the form of one or more fins or plates can be inserted between the first and second sections. The fins will be located within the channels so as to direct the fluid flow towards the channel walls, thus increasing heat transfer therefrom. The first and second sections can then be welded together to form a single collector member. In this manner cross flow elements can be introduced into the channels during fabrication to increase the heat collection effectiveness.

Once the member has been cut to the required length, the internal partitions 20 of the member in figure 4a are then recessed by removing a length of material from each end of the partitions such that the channels 22 start and end within the boundaries of the first and second surfaces. In addition, material is cut from the ends of each leg 24 so that the first 16 and second 18 surfaces overhang the ends of the legs 24 as shown in figure 3b.

In figure 5c a hole has been cut in the second surface 18 at each end of the collector member 12 and a pipe 32 has been welded in place to provide an inlet and outlet for heat transfer fluid. Each end of the collector member is then sealed by welding a sheet aluminium strip 34 to the end faces as shown in figure 5d.

The sealed member 12 is then coated or otherwise surface treated to improve the thermal transfer properties . Conventional treatments include powder coating, anodising, etc. The collector surface or coating is provided with nano-particles which are of the correct size so as to absorb light of suitable wavelengths, thereby increasing the efficiency of the collector.

Furthermore the inner and outer surfaces of any embodiment of a collector according to the present invention may also be provided with nanosurfaces or nanoparticles using conventional techniques . Nanosurfaces on the interior increase the available surface area for convective heat transfer to the heat transfer fluid. The heat transfer fluid may also be provided with nano- p articles to improve heat transfer properties .

The collector members are not glazed so that temperature differentials can allow energy to be collected even at night if necessary.

The fabricated collector members can then be installed on a building for use in place of a conventional roof using right hand or left hand fixing clips shown in figure 5e. The fixing clip 33 is for attachment on the right hand side of the collector member, whilst the fixing clip 35 is for the left hand side.

The feet 26 of a first collector member 12 can be mounted and fixed to a roof structure or frame on a building. A second collector member 13 can then be arranged alongside the first collector member such that the connection members 28 of the adjacent members overlap as shown in figures 4a. Thus the walls of the trough formations provide abutment surfaces which interlock to hold the adjacent members in place. Subsequent members can be added to cover the entire roof of a building. As can be seen in figures 4a and b, the first surface of each of the adjacent panels is substantially planar such that there is no gap between panels.

In figure 6b, the connection members 28 comprise a single L- shaped proj ection which interlocks with an opposing L-shaped projection on an adjacent member.

The interlocking nature of the collector members allows for simple installation that can replace a conventional roof and does not require panels to be fitted over an existing roof in an unsightly manner. Thus the collector of the present invention gives the appearance of a conventional roof but with the increased efficiency and functionality offered by the energy collector design. Whilst the above description refers exclusively to the flat and curved profiles shown, a variety of profiles can be provided in line with local building practices such as, for example, a bold roll collector or a pantile collector.

In addition to visual appearance, the surface area for collection and transfer of energy to the heat transfer fluid of a curved profile collector is greater than for a flat collector. Thus performance can be increased. Whilst, replacement of a conventional roof is intended as a primary application of the collector, it will be apparent to the person skilled in the art that the collector of the present invention could be used at any angle between horizontal and vertical. Thus the collector of the present invention could replace any outer cladding of a building. The joining edges of the collector panels could be made water tight by providing sealing material along the join such that a flat roof can simply be catered for.

In a further advancement of the present invention, the outer surface of the collector may be provided with photovoltaic cells such that the collector is used to generate electricity. The aluminium structure of the collector in this embodiment conducts heat away from the photovoltaic cells which is transferred to the heat transfer fluid. In this embodiment, the collector thus serves to not only provide a source of heat for the heat transfer system, but also cool the PV cells, increasing the efficiency thereof.

Studies into the structural strength, the thermal behaviour and also the fluid dynamics within the collector members have been carried out. A collector member in the region of 200-600mm wide, with a series of channels having internal surface dimensions of l Ommxl Omm, wall thickness of 2mm and an internal fin wall thickness of 1mm has been found to provide a suitable strength by calculation of the surface moment of inertia. Furthermore the aluminium walls provide a fairly even surface temperature around each channel which is close to the member's outer surface temperature.

Various configurations of mass flow of heat transfer fluid per member and channel width produce variable amounts of heat gain and efficiency depending on the weather conditions. Thus the width of the channels may be varied, although a range of between 5-30mm has been found to be suitable with mass flow rates per member of between 0.02-0.4 kg/s for domestic heating. However for different applications, such as heating swimming pools, larger volumes of lower temperature water can be put to good use and so the dimensions and operating variables for the present invention may be altered to suit specific applications.

Optimised designs will also take account of the cost of aluminium compared to the mechanical strength and thus product life of the collector. In addition, whilst the collector will operate at a greater efficiency for increased flow rates, one must take into account the whole thermal system, since a larger temperature lift by the heat pump will incur system inefficiencies .

Claims

What is claimed is:

1. A thermal energy system for heating and/or cooling applications, the thermal energy system having solar collection means for transferring heat energy to a heat transfer fluid and thermal storage means connected to the collection means to allow the transfer of heat therebetween via the heat transfer fluid, the system having control means arranged to receive readings of operational variables from the thermal energy system and to process the operational variables using a system model so as to predict future values of the operational variables for the system and the control means controlling the flow of the heat transfer fluid around the system based on the predicted operational variable values.

2. A thermal energy system according to claim 1 , wherein the system model is adaptive to current and/or predicted changes in operational variables.

3. A thermal energy system according to claim 1 , wherein the operational variable readings are stored by the control means.

4. A thermal energy system according to claim 3, wherein changes in the operational variable readings over time are monitored so as to be able to predict future operational variables.

5. A thermal energy system according to claim 3, wherein the control means generates a data plane based upon stored operational variable readings and compares new readings with the data plane in order to determine any discrepancy therebetween.

6. A thermal energy system according to claim 1 , wherein the control means is arranged to perform statistical time advancing processing of the operational variables readings in order to determine predicted operational variables.

7. A thermal energy system according to claim 6, wherein error values for the predicted operational variable values are generated and used to iteratively refine the predicted operational variable values until acceptable error values are obtained.

8. A thermal energy system according to claim 1 , wherein the system comprises thermal upgrading means connected to the collection means and the thermal storage means .

9. A thermal energy system according to claim 8, wherein the thermal upgrading means comprises a heat pump .

10. A thermal energy system according to claim 1 , wherein the control means is provided remotely of one or more premises to be heated and/or cooled by the thermal energy system.

1 1. A thermal energy system according to claim 10, wherein the control means is accessible from the premises via the internet.

12. A thermal energy system according to claim 10 or claim 1 1 , wherein the control means is common to control multiple thermal energy systems .

13. A thermal energy system according to claim 1 , wherein the system includes a pump or fan and one or more valves disposed between the collection means and the thermal storage means, the pump or fan and valves being controlled by the control means.

14. A thermal energy system according to claim 1 , wherein the thermal storage means comprise any or any combination of a hot water reservoir, a high temperature store and/or a low temperature store.

15. A thermal energy system according to claim 1 , wherein the system includes one or more sensors for taking operational variable readings.

16. A thermal energy system according to claim 1 , wherein the operational variable readings comprise a plurality of temperature readings taken at different points within the system.

17. A thermal energy system according to claim 1 , wherein the system is operable in a heating mode and a cooling mode, wherein heat is transferred to the transfer fluid via the collection means in said heating mode and wherein heat is transferred from the transfer fluid via the collection means in said cooling mode.

18. Control means for a thermal energy system, the thermal energy system having solar collection means for transferring heat energy to a heat transfer medium, thermal upgrading means for increasing the thermal energy within the system and thermal storage means, the collection means, upgrading means and storage means being connected to allow the transfer of heat therebetween via the heat transfer fluid, the control means arranged to receive readings of operational variables from the thermal energy system and to process the operational variables using a system model so as to predict future operational variables for the system and the control means controlling the flow of the heat transfer medium around the system based on the predicted operational variables.

19. Solar collection means for a thermal energy system, said collection means having an outer thermally conductive surface for the reception of solar radiation, wherein said collection means has one or more formations extending behind the outer surface, the formations being formed integrally with the outer surface and shaped to provide one or more elongate conduits for conveying a heat transfer fluid through the collection means during use.

20. Solar collection means according to claim 19, wherein the outer surface and formations are elongate in form and have a substantially constant cross sectional profile along their length.

21. Solar collection means according to claim 19, wherein the outer surface and formations are extruded as a single member.

22. Solar collection means according to claim 19, wherein the collection means has a fluid inlet and outlet and one or more elongate conduits in fluid communication therebetween.

23. Solar collection means according to claim 19, wherein a the solar collection means has a plurality of conduits which share a thermally conductive outer surface via which heat energy can be transferred to and/or from the heat transfer fluid as it flows along said conduits.

24. Solar collection means according to claim 23, wherein the inlet and outlet are provided at the same end of the collection means such that the or each conduit is shaped to convey fluid initially in a first direction away from the first end and subsequently in a second opposing direction.

25. Solar collection means according to claim 19, wherein an internal surface of the or each conduit is profiled.

26. Solar collection means according to claim 19, wherein the formations form internal voids in addition to the conduits, the voids being substantially parallel with the conduits.

27. Solar collection means according to claim 19, wherein the outer surface is curved in profile so as to form one or more peaks and troughs running along the length of the collection means.

28. Solar collection means according to claim 19, wherein the collection means comprise one or more connection members extending along one or more sides of the collection means.

29. Solar collection means according to claim 28, wherein opposing connection members are integrally formed on opposing sides of the collection means.

30. Solar collection means according to claim 28 or claim 29, wherein the connection members comprise a lip and/or slot.

31. Solar collection means according to any one of claims 28 to 30, wherein the connection members are associated with the outer surface.

32. Solar collection means according to claim 19, wherein the collection means comprise integral locating means for attachment of the collection means to a building.

33. Solar collection means according to claim 32, wherein the locating means take the form of a recess having an opening of reduced dimensions

34. Solar collection means according to claim 19, wherein the first outer surface is separated from a second opposing surface by the one or more formations, the second surface providing a backing to the collection means arranged for attachment to a building frame.

35. Solar collection means according to claim 19, wherein the collection means is operable in a heating mode and a cooling mode, wherein heat is transferred to the transfer fluid via the collection means in said heating mode and wherein heat is transferred from the transfer fluid via the collection means in said cooling mode.

36. Solar collection means according to claim 19, wherein the conduit is substantially circular in cross section.

37. A solar collector for a thermal energy system, the collector comprising a plurality of collection means, the collection means taking the form of panels having locating means for attachment of the panels to a building and connection means for connection of each panel to an adjacent panel, each panel having an outer surface and one or more formations extending behind the outer surface, the formations being formed integrally with the outer surface and shaped to provide one or more elongate conduits for conveying a heat transfer fluid through the collector panels during use.

38. A solar collector according to claim 37, wherein each collector panel is connectable to an adjacent collector panel to form the solar collector with a substantially continuous outer surface comprising the joined outer surfaces of each of the collector panels.