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AU2011201748A1 - Evacuated tube solar heat collector with integral heat storage - Google Patents

Evacuated tube solar heat collector with integral heat storage Download PDF

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Publication number
AU2011201748A1
AU2011201748A1 AU2011201748A AU2011201748A AU2011201748A1 AU 2011201748 A1 AU2011201748 A1 AU 2011201748A1 AU 2011201748 A AU2011201748 A AU 2011201748A AU 2011201748 A AU2011201748 A AU 2011201748A AU 2011201748 A1 AU2011201748 A1 AU 2011201748A1
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AU
Australia
Prior art keywords
heat
glass tube
solar collector
evacuated glass
evacuated
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AU2011201748A
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Heinz-Joachim Muller
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SUN2STEAM Pty Ltd
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SUN2STEAM Pty Ltd
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Priority to AU2011201748A priority Critical patent/AU2011201748A1/en
Publication of AU2011201748A1 publication Critical patent/AU2011201748A1/en
Abandoned legal-status Critical Current

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00Solar heat collectors using working fluids
    • F24S10/40Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors
    • F24S10/45Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors the enclosure being cylindrical
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00Solar heat collectors using working fluids
    • F24S10/90Solar heat collectors using working fluids using internal thermosiphonic circulation
    • F24S10/95Solar heat collectors using working fluids using internal thermosiphonic circulation having evaporator sections and condenser sections, e.g. heat pipes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00Arrangements for storing heat collected by solar heat collectors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00Arrangements for storing heat collected by solar heat collectors
    • F24S60/10Arrangements for storing heat collected by solar heat collectors using latent heat
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/40Solar thermal energy, e.g. solar towers
    • Y02E10/44Heat exchange systems

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Sorption Type Refrigeration Machines (AREA)

Abstract

Evacuated tube solar heat collector with integral heat storage The solar thermal collector of this invention comprises an evacuated glass solar collector with an integral heat storage system in an internal tank and a means to transfer heat from the tank to the point of use. The evacuated glass tube and the tank are in a removable way connected to each other allowing easy handling during assembly and convenient replacement of the evacuated glass tube in case of damage. The integral heat storage system is based on phase change. A material providing a phase change in the desired temperature range can store more heat than a material showing no phase change in said temperature range. The evacuated glass solar collectors can be combined to a solar collector module by arranging the individual solar collector tubes in a substantially parallel linear arrangement. The solar thermal collector module of this invention forms a simple, compact, integrated unit of low cost and high efficiency which can be combined with other units to form an array of larger area. This invention avoids the use of additional storage tanks for heated materials like for instance hot water tanks in a solar hot water system.

Description

Evacuated tube solar heat collector with integral heat storage BACKGROUND OF THE INVENTION Field of the Invention This invention relates to solar heat collectors based on the Dewar principle. These collectors are usually called evacuated glass tube solar collectors or evacuated tube collectors or evacuated tube solar collectors. Specifically this invention relates to evacuated tube solar collectors with integral heat storage based on phase change. Description of the Prior Art Traditionally heat for hot water has been prepared directly or indirectly from burning fuel. With increasing cost of fossil fuels and driven by the risk of climate change the use of solar energy for the preparation of hot water has been increasing dramatically in the last years. Solar heat collectors, also called solar collectors are used all over the world to harvest solar radiation and convert it into heat energy. This heat energy is usually used directly or stored in the form of hot water. There are many variations of solar collectors. They can generally be divided into flat plate collectors and evacuated tube collectors. The application of flat plate collectors is limited by heat losses as an efficient thermal insulation of the adsorbing surface is not possible. This can be demonstrated by the fact that achievable maximum temperatures are much higher for evacuated glass tube solar collectors then they are for flat plate collectors. Evacuated tube solar collectors find more and more application because they are very efficient, even at low ambient temperatures. The reason for the high efficiency of evacuated tube collectors is the excellent thermal insulation between the heated inside and the outside based on the concept of a Dewar flask. Vacuum insulation for flat plate collectors is not possible because the resulting forces cause by the pressure difference would destroy flat glass plates of normal thickness. The evacuated glass tube solar collector comprises an outer glass tube and an inner tube of a gas impermeable material with a selective absorber layer with a high adsorptance of solar energy. Both tubes are sealed gastight together at least at one end, with each glass tube sealed individually at the other end as required. A permanent high vacuum between both tubes provides an excellent thermal insulation between the two glass tubes. The outside of the inner glass tube is coated with a selective layer with high absorptance over most part of the electromagnetic spectrum of solar radiation but a low emittance in the range of infrared radiation. This means that solar radiation heats up the inner tube and the inner tube stays hot because it is well insulated. The insulation is so good that even at temperatures below the freezing point of water, temperatures above 150 oC can be created in the evacuated collector tube under solar radiation when it is stagnant, which means the heat is not removed from the tube. Several such tubes are usually assembled in a parallel arrangement of 8 to 30 tubes to form a solar collector module. It is possible to improve the heat output of the modules by using reflectors as for instance described in US4649903. One of the most common designs is usually called Sydney tube. This evacuated tube solar collectors is consisting of an outer glass tube and an inner tube of the same material. The inner tube is sputter coated with a selective absorber layer with a high adsorption of solar energy. Good adsorption layers have a high adsorptance over most of the part of the solar spectrum and a low emittance in the infrared range of the electromagnetic spectrum. Both tubes are sealed gastight together at one end. Each glass tube is sealed individually at the other end. Such a system has been described in AU592620. In the present application reference is made to mechanical design and materials described inAU592620. The method of limiting the maximum temperature of the collector as mentioned in AU592620 is not necessarily required for this application. There are various modifications of this design as for instance relating to the mechanical stability of the glass tubes in 1 US4649903 or to the quality of the adsorption layer in AU1938883. All these designs have in common that the whole double wall tube, comprising an outer glass tube and an inner glass tube, is open at one end and closed at the other end. This allows for independent thermal expansion of the individual tubes without crating tensions that could lead to the breakage of the glass. The total length of the tube is about 10 to 40 times larger than its outside diameter. Common outside diameters are 47mm, 58mm and about 70mm. These collector tubes are either used as direct contact evacuated tube collectors directly in contact with water on the inside of the inner tube or as an indirect evacuated tube collectors containing a U shaped metal pipe for passing a liquid as a heat carrier, or a heat pipe to capture the heat from the inside of the inner tube of the evacuated tube collector as for instance described in US4119085. Usually the indirect evacuated tube collectors have metal fins to make a thermal connection between the metal pipe inside the glass tube and the inner surface of the inner glass tube. In the case of indirect collectors with heat pipes the heat will be transferred from the body of the heat pipe, called evaporator, inside the glass tube to the head of the heat pipe, called condenser, outside the glass tube. Usually several evacuated tube solar collectors are arranged in parallel to form solar collector modules. These collector modules are usually arranged with the open end facing up at an angle of about 20 to 90 degrees above horizontal to allow either convective water flow respectively proper functioning of the heat pipes. The solar collectors described so far require an external water tank to store heat in the form of hot water for the time when the sun is not shining. This makes the systems more complicated and costly as they need an external hot water tank. Several attempts have been made to overcome this issue. AU2006253150 describes a solar collector with integrated heat storage comprising of a large tank inside a mirror system. As the tank has a much larger diameter than usual evacuated tube systems, such a system is very bulky and is difficult to install on standard roofs. CN201297788Y describes a solar collector module comprising of evacuated tubes directly filled with water whereby the tubes and the connecting channel contain small containers with phase change material in order to increase the heat capacity stored inside the collector. This design is increasing the heat capacity inside the collector module. However this is limited as the containers must leave sufficient space around the containers to allow for convective water flow to transport the heat out of the tubes. The design also limits the maximum temperature to the boiling point of water. An evacuated glass tube with integrated tank is also described by CN101639296A and by CN201311104Y. Both inventions require designs of the evacuated tube collector that are more complicated than the common design for evacuated tube solar collectors based on the Sydney tube design. The systems are more difficult to install and more complicated because in case of a breakage individual glass tubes cannot be changed easily. There is little known about the application of evacuated tube solar collectors for space heating besides the use of hot water systems with tanks for heat storage in the form of hot water. There is a need for new technology that avoids the complications of water flow and hot water storage for space heating applications. Space heating means the heating of rooms in buildings to a comfortable temperature. Solar heat can also be used for solar cooling as described for an adsorption cooler in WO 2008114266. The design provides means for storing solar energy, but it does not make use of the advantageous properties of evacuated tube solar collectors. 2 SUMMARY AND OBJECT OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks by the provision of a solar collector with good insulation in the form of an evacuated glass tube solar collector, with integral heat storage in an internal heat storage tank and with a means for removal of heat from the storage tank for utilization. It is a further object of the present invention to make use of the latent heat of phase change in the heat storage material. It is a further object of the present invention to use such evacuated glass tube solar collectors arranged as solar collector module. It is a further object of the present invention to use such a solar collector module for heating of water without requiring an additional hot water tank. It is a further object of the present invention to provide a solar collector module with integrated heat storage whereby the evacuated glass tubes are easily removable thus making installation and repair much simpler. It is a further object of the present invention to use such a solar collector module for heating of air to be used in space heating or other applications. It is a further object of the present invention to use such a solar collector module for heating and cooling in air conditioning and other applications. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF DRAWINGS The present invention is illustrated in the accompanying drawings, in which: Fig. 1 is a cross-sectional view of one embodiment of the evacuated tube solar energy collector with heat storage and heat pipe; Fig. 1a is a cross-sectional view perpendicular to the length axis of the evacuated tube collector showing one embodiment of the solar energy collector with heat storage and heat pipe; Fig. 2 is a cross-sectional view of one embodiment of the evacuated tube solar collector with heat storage and a heat pipe in thermal contact with pipe conducting a liquid; Fig. 3 is a cross-sectional view of one embodiment of the evacuated tube solar collector with heat storage and a heat pipe with fins at the upper end in direct contact with heat air in a channel; Fig. 4 is a cross-sectional view of one embodiment of the evacuated tube solar collector with heat storage and a heat pipe with fins at the upper end in direct contact with heat air in a channel, with the heat storage based on adsorption/desorption of a fluid on an adsorbent; Fig. 5 is a cross-sectional view of one embodiment of the evacuated tube solar collector with heat storage and a heat pipe with the upper end of the heat pipe in contact with a solid heat conductor, for instance a hot plate for cooking. 3 Fig. 6 is a cross-sectional view of one embodiment of the evacuated tube solar collector with heat storage and a heat pipe with the upper end of the heat pipe in contact with a secondary heat pipe for further transfer of heat to the point of use without the need for pumping a heat transport fluid. FIG. 7 is a view of several evacuated collector tubes from of Fig. 2 arranged as a solar collector module for liquid heating; FIG. 8 is a view of several evacuated collector tubes from of Fig. 3 arranged as a solar collector module for air heating; FIG. 9 is a view of several evacuated collector tubes from of Fig. 4 arranged as a solar collector module for air heating and cooling; DETAILED DESCRIPTION OF THE INVENTION The present invention makes use of the latent heat of phase change to increase the heat capacity of the storage material. Latent heat of phase change is the heat that is required to change the state for a material (phase) from solid to liquid (melting) or from liquid to gas (evaporation). The same amount of heat will be generated when the when the phase change happens in the opposite direction by solidification respectively condensation. In the scope of this invention adsorption of a fluid (gas or liquid) to an adsorbent as well as desorption are also described as phase change. Beside the large amount of energy that can be stored and recovered using phase change, using phase change for heat storage has the added advantage, that the temperature of the heat storage stays nearly constant as long as the phase change is not complete. This makes use of the heat energy much easier. The invention will now be explained in the following description which is provided with accompanied schematic drawings of embodiments. These examples are only explanatory and are not meant to be limiting the scope of the invention. Explanations given at the description of the individual embodiments can be applied to other embodiments unless especially limited by the context. In a first embodiment Fig. 1 shows in a cross-sectional view the basic principle of a common evacuated tube solar collector comprising an outer tube 1 and an inner tube 2, tightly sealed to contain a permanent high vacuum between the two collector tubes, to which a heat storage comprising metal tube 3 and phase change material 4 has been added. In Fig. la the cross section of the solar collector along the dotted line in Fig. 1 can be seen. The broad arrow in Fig.1 to Fig.6 ae symbolizing solar radiation. Evacuated tube solar collectors are produced and used in large numbers because of the favourable properties especially high solar radiation adsorptance and very small heat losses because of the vacuum between the tubes 1 and 2 and the specific design of the adsorption layer on tube 2. This makes evacuated tube solar collectors superior to flat panel solar collectors which cannot be built with vacuum insulation because the forces created by the pressure difference would destroy flat glass plates. These tubes are usually made of borosilicate glass. Other materials and even a combination of glass and metal are possible. It is even possible that the tube 2 and the metal tube 3 are actually the same part. But in these cases the glass-metal connections must be permanently stable to changes of temperature in order to maintain a permanent vacuum in the gap between tube 1 and 2. Therefore the preferred embodiment of this invention comprises an all-glass evacuated tube. 4 There are specific dimensions of these tubes which are common throughout the industry. One of the most common dimensions is a collector tube with 1.8m length and an outer diameter of tube 1 of 58 mm and an outer diameter of the inner tube of 47mm. Another common dimension is a collector with 1.5m length and an outer diameter of 47mm. The invention is not limited to these dimensions. An expert knowledgeable in the subject of heat and heat transfer can easily make adjustments to the dimensions allowing for an optimisation of the heat capacity of the heat storage in regard of the expected heat input into the solar collector. It is possible to use reflectors to increase the amount of solar radiation hitting the evacuated solar collector tubes. So for instance reflectors can be used to improve the performance of collector modules comprising evacuated glass tube collectors in an essential parallel arrangement. This will utilize the solar radiation that hits the gap between individual collector tubes and would otherwise be lost. It is also possible to use a larger reflector area per collector tube and thus increase the energy significantly that hits the collector tube. However in these cases care must be taken to select the proper dimensions of the collector tube and the heat capacity of the heat storage material to match the expected heat input in order to avoid creating excessive temperatures. The heat storage comprises a metal tube 3 with an outer diameter slightly smaller than the inner diameter of the inner glass tube 2 of the evacuated tube collector. Not shown in Fig. 1 and the following figures, but recommended, is a means to improve the heat transfer between the inner tube 2 and tube 3, for example by having a thin corrugated metal sheet or a high boiling liquid or some sort of heat transfer grease in the gap between inner tube 2 and metal tube 3. In Fig. 1 tube 3 is drawn as being open to the atmosphere. However tube 3 can be open to the atmosphere or closed depending on the nature of the phase change material 4. If phase change materials are used that are stable under atmospheric conditions at elevated temperatures and essentially do not evaporate it is usually cheaper to have tube 3 open at the top. If tube 3 is closed, it has to be made sure that it is sufficiently stable and will not leak or rapture when the heat storage is heated and the pressure inside is increasing. Contained within metal tube 3 is essentially a phase change material 4, meaning a solid with a melting point in a range between 70 to 150 0C, preferentially in a range of 80 to 140 0C and even more preferentially in a range of 100 to 120 C. The melting point must suit the purpose and the expected heat input into the solar collector. If the melting point is too low, the usable heat will be at the same low temperature which could be too low for the application. If the melting point is high, the usable temperature will be correspondingly higher, but as heat losses are increasing with increasing difference between storage temperature and ambient temperature, too much heat could be lost during heat storage. Also if the melting point is too high, the phase change material may not melt at all during normal conditions sunshine. The melting point of phase change materials can be looked up in tables. For the selection of the phase change material not only the melting point but also other properties like corrosiveness, cost and safety are of importance. There are various classes of phase change materials like salts, salt hydrates or organic materials. The spectrum of organic materials is very wide with some of the major groups being paraffin wax and sugar alcohol. One preferred sugar alcohol as phase change material of this invention is erythritol. With a melting point of about 115 0C erythritol is well suited for the application. Erythritol is not corrosive and safe. It can be kept in an open tube 3. Using specific additives as for instance described in EP0722997 help to prevent degradation of the phase change material material at elevated temperatures. These and other additives can also be used to prevent supercooling. Supercooling happens when the crystallisation of material is delayed and starts below its melting point which can make heat storage more difficult to use. It is also possible to add paraffin wax or similar immiscible materials with low density to the phase change material. The incompatible material with will cover the phase change in tube 3 and will reduce degradation by limiting access of oxygen from air to the phase change material. 5 The tube 3 should be filled with the maximum possible amount of heat storage material in order to maximize the heat storage capacity. In an open container care must be taken, that there is no overflow of the phase change material when the system is heating up. In a closed system it is advantageous if a sufficiently large void is left when filling the tube 3 with phase change material 4 to allow for expansion of the melt without bursting the tube 3. The void can be evacuated before tube 3 is sealed to prevent the unnecessary build up of pressure. A further element of the evacuated tube solar collector with integral heat storage is a means for removal of heat from the heat storage material 4 in tank 3 for utilization. Any means of heat transport along the length axis of tube 3 is possible. Transport of a fluid, for instance a liquid comprising water, through a U-shaped metal pipe is an option. However it is usually easier to have a heat pipe inserted into tube 3. Heat pipes in their simplest form are tubes usually made of metal with a long tube as evaporator 6 and an upper section as condenser 7. The heat pipe is sealed at both ends and contains a small amount of a liquid under vacuum, with the remaining inner volume of the heat pipe being filled with vapour of said liquid corresponding to temperature and pressure. The solar collector and hence the heat pipe is at least slightly inclined with the condenser 7 at the upper end. When the evaporator 6 is warmer than the condenser 7, some liquid will evaporate and condense in the condenser 7, releasing heat. The condensed liquid will trickle back into the evaporator 6 and the process can continue until the temperature between evaporator and condenser drops below a certain amount. This process is very efficient and works over a wide temperature range. In comparison to fluid flow in a U tube or similar, the heat transfer by a heat pipe has the advantage that the process works without any external pumping and that the material in the heat pipe is not in direct contact with the final heat carrying medium. The evacuated glass tube and the tank are in a removable way connected to each other allowing easy handling during assembly and convenient replacement of the evacuated glass tube in case of damage An important advantage of this set-up is that in the major embodiment of this invention the evacuated glass tubes 1 and 2 are not inseparably and permanently connected to tube 3 containing the phase change material. In case of a breakage of the glass tube 1 or 2 or loss of vacuum, the evacuated glass tube can be easily removed and replaced by a new evacuated glass tube of the same dimension. The evacuated glass tube and the tank are in a removable way connected to each other allowing easy handling during assembly and convenient replacement of the evacuated glass tube in case of damage. In order to prevent heat loss and to reduce external influence on the phase change material the evacuated glass tube comprising the combined glass tubes 1 and 2 can be covered with a lid 5. The lid does not seal completely to allow for pressure release when the solar collector is varying temperature. In another embodiment of the invention Fig. 2 shows in a cross-sectional view the basic principle as shown in Fig. 1. In addition to Fig. 1 the condenser 7 of the heat pipe is in surface contact with a pipe 8 used for transporting a fluid for heat transfer, usually a liquid essentially a liquid containing water. In this embodiment tube 3 is shown as closed. The condenser 7 can be permanently fixed to the pipe 8 but it is preferred to have a removable contact for instance by inserting condenser 7 in fitting pockets formed or welded or soldered into pipe 8. It is also possible that pipe 8 comprises more than one pipe. In this case the condenser in can be wedged into fitting sections formed in pipes 8. The pipe 8 is covered by appropriate insulation material 9 like for instance glass wool to prevent heat loss. Such a system can be used to provide hot water on demand by drawing heat from the internal heat storage as required. 6 In another embodiment of the invention Fig. 3 shows in a cross-sectional view the basic principle as shown in Fig. 1. In addition to Fig. 1 the condenser 7 of the heat pipe is sitting inside an air channel 10. Air flowing through channel 10 can be heated up by the heat coming from condenser 7. In the context of this invention air means air or any other suitable gas or gas mixture. In order to improve the heat transfer between condenser and air, the condenser can be equipped with fins 11 or other ways of increasing the surface of condenser 7 or by any other means like for instance increasing the turbulence of the air. Another embodiment of the invention is shown in Fig. 4 in a cross-sectional view. In this embodiment the phase change process is related to adsorption and desorption. In this case the invention makes use of the day-night cycle for desorption and adsorption of a fluid on an adsorbent. However it is also possible to add extra adsorption/desorption cycles by shading the solar collector in intervals. Adsorption cooling systems as such are well known but they have not been documented in combination with the concept of this invention. A variety of combinations of adsorbents and fluids is possible. The best known adsorbents are silica gel, zeolite and activated carbon. However many other adsorbents either of homogeneous nature or composites like for instance zeolite or activated carbon loaded with calcium chloride are possible. The combination of an adsorbent and a fluid, which is usually called refrigerant in the art, is called working pair. Some of the most common working pairs are activated carbon plus methanol and zeolite plus water. Each working pair has its distinctive properties and the selection of the working pairs by somebody skilled in the art can be based on the requirements of the specific system. In the description of this example the working pair zeolite plus water has been used as it is simple, safe and cost efficient. However this invention is not limited to this working pair. Any other working pair can be chosen according to the specific requirements of the process. Tube 3 contains an adsorbent 14. The adsorbent comprises particles sufficiently large to allow gas flow between the particles. Alternatively the adsorbent can be formed in a permanent shape that is designed to fit into tank3 and that contains sufficient channels to allow vapour flow the adsorbent material. The tube is connected through a condenser 12 to a tank 13. The system comprising tube 2, condenser 12, tank 13 and connecting pipes is evacuated and contains a certain amount of a liquid in balance with its vapour according to temperature and pressure. During day time when the collector receives heat from the sun, the adsorbent 14 releases vapour of the fluid that had been adsorbed. The vapour is condensing in the condenser 12 and the condensed liquid is collected in the tank 13. Condenser 12 can be cooled by ambient air or by any other coolant that can withdraw sufficient heat from the condenser. During the night, heat can be removed from the condenser 7 of the heat pipe. The adsorbent 14 cools down and starts to adsorb vapour according to the nature of the working pair, pressure and temperature. This adsorption process creates heat which keeps the temperature of the adsorbent up and allows the removal of more heat from the condenser 7 of the heat pipe. The process can continue until either the adsorbent 14 is saturated with the fluid or until all liquid has evaporated from the tank 13. The same system can be used for cooling. As the evaporation of the liquid from the tank 13 consumes heat, the temperature of the liquid in tank 13 will drop during evaporation of the liquid when the tank 13 is well insulated with insulation 15. The total amount of heat can be maximized by cooling the condenser 7 of the heat pipe during this process with air at ambient temperature or which will keep the temperature of the adsorbent 14 low and increases the amount of vapour that can be adsorbed. The 'coolness' can be stored in the heat capacity of the tank 13 and in the remaining liquid in the tank 13 or it can cool down another heat reservoir like for instance water stored or flowing outside the tank. In the case of water being used as the adsorbing fluid, the evaporation of water from 7 the tank 13 can cause the remaining water in the tank 13 to freeze which is another case of highly efficient heat storage by phase change. After the process comes to a halt, an efficient insulation 14 can be used to cover the cold storage. During the day this cold storage can be used for cooling, either by blowing air through the cavity surrounded by insulation 14 cool the air down before it is used for cooling in an air conditioning system or by using the cold storage to cool a liquid that can be used as coolant in an air conditioning system or by any suitable other method. In another embodiment of the invention Fig. 5 shows in a cross-sectional view the basic principle as shown in Fig. 1. In addition to Fig. 1 the condenser 7 of the heat pipe is in thermal contact with a heat conducting body 15 that can be used as a hot plate. Insulation 16 around the hot plate and an optional insulating cover 17 prevent heat losses. In order to increase the heat capacity of the cooker several condensers 7 of heat pipes can be connected to the same heat conducting body by adjusting the shape and arrangement of the heat pipes accordingly. In another embodiment of the invention Fig. 6 shows in a cross-sectional view the basic principle as shown in Fig. 2. Different to the process shown in to Fig. 2 the condenser 7 is in surface contact with a tube 8 which is actually the evaporator of a secondary heat pipe. This heat pipe can transfer the heat further to its condenser where it can be put to use. This design allows collecting the heat from several evacuated collector tubes arranged in a module similar to Fig. 7 and transporting the heat to the point of use without any moving parts and without using external energy. The standard design of heat pipes like the ones formed from evaporator 6 and condenser 7 allows only the transport heat against gravity which means the solar collector module must be arranged that the secondary heat pipe 20 is sloped at a certain angle above horizontal. However there are advanced heat pipe designs known to experts skilled in the art that can transport heat horizontally or downwards. Fig. 7, 8 and 9 show a cross sectional view along the length axis of the evacuated collector tube perpendicular to the view in Fig. 1 to 6. Fig. 1a is the cross sectional view perpendicular to the length axis of the evacuated collector tube. In another embodiment, the solar collector module shown in Fig. 7 comprises a multiplicity of substantially parallel evacuated glass solar collector tubes held by framing material 21 using appropriate fixings. The upper part of each glass solar collector tube is held by a case around insulation 9. The condensers 7 of the heat pipes are in surface contact with pipe 8 used for transporting a fluid for heat transfer, usually a liquid essentially containing water as shown in Fig. 2. As can be seen from Fig. 7 each evacuated glass tube can be removed and replaced without the need to disassemble any other part of the solar collector module, exempt the fixings for the individual evacuated glass tube. In another embodiment, the solar collector module shown in Fig. 8 comprises a multiplicity of substantially parallel evacuated glass solar collector tubes held by framing material 21 using appropriate fixings. The upper part of each glass solar collector tube is held by a case around insulation 9. The condensers 7 of the heat pipes have fins or other means for surface enlargement. Air flowing through channel 10 can be heated up as it passes along the condensers 7 as can be seen in Fig. 3 in more detail. As in the examples before each evacuated glass tube can be installed, removed or replaced individually without affecting the collector module. The hot air coming from this module has to be moderated in order to have an output of an air stream at constant and controllable temperature as required for most applications. One way of achieving this is to blend the hot air flowing from channel 10 of the collector module with a cold air flow, using the resulting air temperature as input for an appropriate device controlling at least one of said air flow rates. 8 In another embodiment, the solar collector module shown in Fig. 9 can be used for heating and cooling of air as mentioned in the description of Fig. 4. The collector module looks similar to the collector module shown in Fig. 8. Instead of holding a phase change material, tube 3 is filled with an adsorbent. One or several or all of the individual tubes 7 are collected through one or several coolers 12 to one or several containers 13. The container 12 is surrounded by insulation material 14. By using methods explained in the description of Fig. 4 fluids can be either cooled of heated for application in air conditioning or other in applications where heat or cold is required. It is possible to use several With the invention described it will be obvious that it can be varied in many ways. Such variations are not regarded as a departure of the spirit and scope of the invention, and all modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 9

Claims (20)

1. An evacuated glass tube solar collector consisting of an outer glass tube and an inner tube of a gas impermeable material with a selective absorber layer with a high adsorption of solar energy, both tubes sealed gastight together at least at one end, with each glass tube sealed individually at the other end as required, with a permanent vacuum between both tubes providing an excellent thermal insulation of the inner tube, characterised by having an integral heat storage comprising an inner tank filled with a material supplying high heat storage capacity based on the phase change effect, said tank containing heat storage material, said tank being in a removable way located inside the evacuated glass tube and a means for removal of heat from the heat storage material for utilization
2. An evacuated glass tube solar collector according to claim 1 with the inner tank made from metal
3. An evacuated glass tube solar collector according to claim 2 with a closed inner tank
4. An evacuated glass tube solar collector according to claim 2 with an inner tank open to the atmosphere
5. An evacuated glass tube solar collector according to claim 1 with a means for removing the stored heat comprising one or several heat pipes.
6. An evacuated glass tube solar collector according to claim 1 with a means for removing the stored heat comprising of metal pipes for fluid flow for heat transport.
7. One or several evacuated glass tube solar collectors according to claim 1 in combination with one or several coolers and one or several condensate tanks, with heat storage provided by an adsorption process using a working pair, with the inner tank or inner tanks filled with adsorbent.
8. An evacuated glass tube solar collector according to claim 1 with heat storage provided by a phase change material with a melting point between 70 0C and 150 0C.
9. An evacuated glass tube solar collector according to claim 8 with heat storage provided by an organic phase change material with a melting point between 70 0C and 150 0C.
10. An evacuated glass tube solar collector according to claim 9 with heat storage provided by an organic phase change material comprised of sugar alcohols.
11. An evacuated glass tube solar collector according to claim 10 with heat storage provided by an organic phase change material consisting essentially of erythritol.
12. An evacuated glass tube solar collector according to claim 5 with the condenser of the heat pipe transferring the heat to air.
13. An evacuated glass tube solar collector according to claim 5 with the condenser of the heat pipe transferring the heat to a liquid.
14. An evacuated glass tube solar collector according to claim 5 with the condenser of the heat pipe transferring the heat to a hot plate.
15. An evacuated glass tube solar collector according to claim 5 with the condenser of the heat pipe transferring the heat to a secondary heat pipe.
16. An evacuated glass tube solar collector according to claim 1 in a parallel arrangement with several other glass tubes to form a solar collector module.
17. An arrangement of several evacuated glass tube solar collectors according to claim 12 to form a solar collector module for heating air.
18. An arrangement of several evacuated glass tube solar collectors according to claim 13 forming a solar collector module for heating a water based heat carrier.
19. An arrangement of several evacuated glass tube solar collectors according to claim 13 forming a solar collector module for heating a water as an instantaneous water heater.
20. An arrangement of several evacuated glass tube solar collectors according to claim 7 forming a solar collector module that can be used for heating and cooling. 1
AU2011201748A 2011-04-19 2011-04-19 Evacuated tube solar heat collector with integral heat storage Abandoned AU2011201748A1 (en)

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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL2012949B1 (en) * 2014-06-04 2016-06-22 Global-E-Systems Europa B V Heat collector.
CN106403316A (en) * 2016-03-16 2017-02-15 内蒙古博特科技有限责任公司 Intelligent greenhouse solar vacuum pipe type energy storage heater
US11029064B2 (en) * 2018-04-09 2021-06-08 Arizona Board Of Regents On Behalf Of Arizona State University Solar adsorption heat pump and evacuated tube adsorption heat pump and desalination system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL2012949B1 (en) * 2014-06-04 2016-06-22 Global-E-Systems Europa B V Heat collector.
CN106403316A (en) * 2016-03-16 2017-02-15 内蒙古博特科技有限责任公司 Intelligent greenhouse solar vacuum pipe type energy storage heater
US11029064B2 (en) * 2018-04-09 2021-06-08 Arizona Board Of Regents On Behalf Of Arizona State University Solar adsorption heat pump and evacuated tube adsorption heat pump and desalination system

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