WO2004029522A2

WO2004029522A2 - Method of effecting the safe transfer of solar energy and a low-pressure equipment system for the transport of solar energy

Info

Publication number: WO2004029522A2
Application number: PCT/PL2003/000081
Authority: WO
Inventors: Adam Skorut
Original assignee: Adam Skorut
Priority date: 2002-09-27
Filing date: 2003-08-25
Publication date: 2004-04-08
Also published as: PL356349A1; AU2003265029A1; WO2004029522A3; EP1549887A2

Abstract

The subject of the present invention concerns a method of effecting the safe and failure-free transfer of solar energy, and a low-pressure equipment system for the transport of solar energy, which serves to transfer solar energy gathered by collectors to the usable water storage tank, thereby enabling the functioning of the circuit of collectors at a low pressure. The method of effecting the safe transfer of solar energy consists in the introduction of a closed low-pressure gas pocket (4) to the closed circuit of transfer fluid (17) that transports solar energy from the solar collectors (2) to the heat exchanger (6). The low-pressure equipment system for the transport of solar energy utilises two independent circuits, whereas the primary transfer circuit (1), used to transport transfer fluid (17), is made up of solar collectors (2) connected by means of pipes (3) with a heat exchanger (6). The heat exchanger (6) is connected via pipes (3) and through a drainage tank (5) with the circulating pump of the primary circuit (11) and the solar collectors (2), The secondary transfer circuit (7) comprises a circulating pump of the secondary circuit (10), installed on the pipeline which supplies cold water to the heat exchanger (6), and pumps which carry hot water away from the heat exchanger (6) to the usable warm water tank, whereas both the primary and secondary transfer circuits are equipped with a control system (13).

Description

Method of effecting the safe transfer of solar energy and a low-pressure equipment system for the transport of solar energy

The subject of the present invention concerns a method of effecting the safe and failure-free transfer of solar energy, and a low-pressure equipment system for the transport of solar energy, which serves to transfer solar energy gathered by collectors to the usable water storage tank, thereby enabling the functioning of the circuit of collectors at a low pressure.

Existing methods of effecting the transfer of solar energy gathered by collectors are based on a closed system of high-pressure pipelines, which transport the energy-absorbing medium from solar collectors to a heat exchanger. These systems have a medium transport pump and, because of the fact that their working pressure ranges from 0.6 to 0.8 MPa, one or more safety valves. One of these valves is located on the pipeline, directly at the solar collectors. In the event of system failure or a voltage collapse, this causing the shutdown of the pump which transports the energy absorbing medium from the solar collectors, the medium present in the pipeline overheats, and in consequence the excess volume thereof at a pressure above 0.8 MPa must be purged through the safety valve in order to prevent the rupture of the pipes transporting the heat absorbing medium from the solar collectors. The activation of the circuit that absorbs heat from the solar collectors requires the maintenance of a temperature difference between the temperature measured in the solar collector and the temperature of the cold medium leaving the usable water storage tank of at least 8°C.

There exist many different types of equipment that are used to transport solar energy gathered by collectors to heat exchangers. These comprise differing kinds of solar collectors, voluminal preheaters, high- pressure pump modules, control modules and heat exchangers. The voluminal preheaters applied in such systems are of varying design and utilise differing methods of exchanging heat between the solar cycle medium and warm usable water. In such systems, heating water is commonly stored in special buffer containers, which retain the solar thermal energy exceeding that required in order to preheat warm usable water, thereby facilitating the greater efficiency of the existing solar systems. The high-pressure pump modules used in existing systems are fitted - in addition to a circulating pump - with safety and functional equipment, such as safety valves, fluid meters, or nonreturn and cut-off valves, usually installed as a compact subassembly. In order to ensure the optimal utilisation of solar energy, these systems are equipped with various types of control modules which ensure the maximum efficiency of the solar installation; these operate on the basis of the differential temperature principle - the utilisation of solar energy is registered as it occurs and may at any time be checked on the spot by equipment operators. The reheating of water in the preheater by means of a boiler or additionally installed electric heaters may, whenever the need arises, be checked using an additional module. Polish Patent Specification No. 177415 concerns a system for feeding receivers of thermal energy with a carrying medium that is heated in at least one heat source, containing at least one distributing apparatus fitted with a number of outputs. These outputs are used to connect conduits supplying thermal energy receivers with differing temperature levels. Among others, solar collectors may be utilised as heat sources. The system additionally comprises a heat pump fitted with an evaporator, which in turn has a cold receiver, compressor and condenser, the output of which is connected with the input of the next distributing apparatus; this has a greater number of outputs leading to receivers with high temperature levels. The return conduits of receivers with low temperature levels are connected to the outputs of a cumulative apparatus, which is equipped with a single output conduit. The return conduit of the cold receiver is connected to the input of the next distributing apparatus, the outputs of which are connected to receivers with low temperature levels; furthermore, this apparatus is connected to a mixing valve, which - in turn - is connected to conduits leading to the thermal collectors and the evaporator of the heat pump.

One of the disadvantages of the existing methods and equipment systems used to transfer solar energy lies in the high-pressure transport of mediums absorbing heat from the solar collectors. The high pressures occurring within the pipeline and the solar collectors necessitate the application of a number of precise apparatuses protecting the pipeline system against ruptures. These systems cannot operate under extreme conditions or in the field, where the power networks required to provide electricity to the solar energy transfer equipment support apparatuses are unavailable.

Although all of the existing apparatuses and systems take into consideration numerous factors that are of vital importance for the provision of thermal energy to receivers, they do not meet the currently applicable technical and organisational requirements that concern - in particular - the possibility of usage in locations without access to power networks and lacking constant system testing and supervision, and also safety of usage in households.

These disadvantages, resulting from the state of technical knowledge, have been solved in the present invention. The method of effecting the safe transfer of solar energy covered by the invention consists in the introduction to a closed circuit of a medium that transports solar energy from solar collectors to a heat exchanger; within this circuit there is also a low- pressure, advantageously airy low-pressure gas pocket. The volume of the gas pocket is such that it is able to contain the entire - or nearly the entire - quantity of the circuit medium that absorbs heat from the solar collectors. When the system that receives heat from the solar collectors is inoperative, the gas pocket is filled by the freely flowing medium, while the gas in the gas pocket is forced through to the pipeline and heat receiving channels in the solar collectors by the pressure exerted on it by the medium. It is advantageous for the medium which transports the solar energy to be a propylene glycol-based solution that contains anticorrosive and antiexpandable additives. When conditions do not allow for the utilisation of solar energy, the medium is duly secured and fills the low-pressure gas pocket, while the solar collectors and the pipeline that transports the medium thereto are filled with gas. When it becomes possible to use solar radiation energy, the circulating pump is activated and forces the medium to the pipeline, simultaneously pushing the gas out of both the pipeline and the collectors into the low-pressure gas pocket. The medium, with the assistance of the circulating pump and under a pressure not exceeding 100 kPa, flows through the solar collectors and absorbs heat; once it is forced through to the heat exchange, it gives up the heat to another fluid, in most cases directly to the usable water. Throughout this time, the air remains in the low-pressure gas pocket. When darkness falls, or in any other instance when it becomes impossible to utilise solar radiation energy, the circulating pump is switched off. When the pump is deactivated, the medium flows of itself to the low-pressure gas pocket, while air is channelled off to the pipeline and solar collectors .

The low-pressure equipment system for transporting solar energy covered by the present invention is one that serves to transfer solar energy gathered by solar collectors to a usable water storage tank, or a different heat absorbing medium. This system makes use of two independent transfer circuits and a suitably designed closed drainage tank which enables the functioning of the circuit of collectors at a low pressure. The closed drainage tank is installed on the route of the closed circulating transfer fluid pipeline, advantageously behind the point at which the transfer fluid exits the heat exchanger. The capacity of the drainage tank is such that it is able to contain the entire - or nearly the entire - quantity of the circulating transfer fluid. The system comprises solar collectors that are connected via the pipeline with the heat exchanger (advantageously a panel-type model) which in turn is connected via the pipeline with the closed drainage tank installed on its route. The drainage tank is connected with the solar collectors by the pipeline, along the route of which there is installed a primary circuit circulating pump. The system also includes a secondary circuit pipeline that channels cold water to the heat exchanger from the warm usable water tank and also carries hot water away from the heat exchanger to the warm usable water tank, along the route of which there is installed a secondary circuit circulating pump. It is advantageous for all primary and secondary circuit pipelines to be made from copper pipes fitted with special insulation. The system is also equipped with an electronic control system connected with an electronic board fitted with control pushbuttons and system operation indicators. Furthermore, the system includes primary and secondary circuit terminals and a housing that constitutes the basic solar energy transfer module. The primary solar circuit comprises solar collectors installed at a point of good insolation; these are connected via pipes with the solar energy transfer module, which is located in the boiler-room or a different room. The transfer fluid of the primary circuit is, advantageously, a propylene glycol-based solution that contains anticorrosive and antiexpandable additives. The transfer fluid is pumped from the drainage tank located inside the module to solar collectors, where it absorbs energy; subsequently, it returns and - via the heat exchanger (advantageously a panel-type model) - gives the heat up to the secondary warm usable water circuit. The supply and return lines between the system constituting the subject of the present invention and the solar collectors are inclined towards the equipment system module containing the drainage tank. It is advantageous if this inclination is at least 5°.

The secondary circuit is directly connected with the separate warm usable water tank via pipes. The circulating pump of the secondary circuit, which is located within the module, forces cold water from the warm usable water tank to the heat exchanger, where it absorbs energy from the primary circuit; the water, now hot, returns to the usable water tank.

The principle of operation of the primary solar circuit is as follows: when the system is not transferring energy, the pumps are inoperative, thus allowing the transfer fluid of the primary solar circuit to flow of itself to the drainage tank which is located within the module. This protects the transfer fluid against temperature extremes when the system is inoperative, and also the collectors when no electricity is available during sunny weather, for both the channels of the solar collectors and pipes are filled with air, and thereby secured against overheating. The lack of transfer fluid in the solar collectors and pipes during system standstill ensures that the maximum working pressure of the solar circuit does not exceed 100 kPa. The circuit that receives heat from the solar collectors is activated by a small temperature difference - totalling approximately 2°C - between the temperature measured at the solar collectors and the temperature of water measured in the cool part of the warm usable water tank. At this point, the hysteresial controller activates the circulating pump of the primary circuit. The circulating pump of the primary circuit starts to force the transfer fluid into the air-filled fluid transport pipes and solar collector channels. Air is forced out of these elements and occupies the space vacated by the transfer fluid in the drainage tank, however to such a level of transfer fluid in the drainage tank at which the point of entry of transfer fluid to the circulating pump of the primary circuit is always flooded. The circulating pump of the secondary circuit is also controlled by a hysteresial controller and is activated at the same time. The control system serves to monitor the temperature in the usable water tank and on the solar collectors, so as to detect when the quantity of energy collected is such that it should be transported from the collectors to the warm usable water tank. A variant of the equipment system for the transport of solar energy covered by the present invention, intended for conditions where no electricity is available for powering the system, is a system additionally fitted with photovoltaic battery; this cooperates with a regulator and gel accumulator, ensuring that the system is fully independent of power networks. Through the regulator, the photovoltaic battery powers the electric motors of the circulating pumps of the primary and secondary circuits and the control system, transferring excess electricity to the accumulator. If the photovoltaic battery cannot be used, the gel accumulator supplies the electricity necessary to power the equipment system and the control system. Since the photovoltaic battery of the gel accumulator provides power, the system does not require practically any mains electricity - even for loading the accumulator. The voltage thus obtained for powering the equipment system, with a nominal value of 12 V, is completely safe for human operators.

In addition, the equipment system covered by the present invention is fitted with an apparatus that controls water and transfer fluid temperatures at every point of their respective circuits. It is highly advantageous for the system to be equipped with a kit for measuring the total quantity of heat transferred to the water during system operation.

It is advantageous for the control system to be fitted with a processor enabling the monitoring of the process of solar radiation transformation using a PC, while by installing special software and connecting the PC to the Internet the operation of the equipment system covered by the present invention may be supervised using mobile telephony from any point on earth.

One of advantages of the method of effecting the safe transfer of solar energy and the low-pressure equipment system for the transport of solar energy covered by the present invention consists in its simple principle of operation, the simple and inexpensive design of the whole equipment system, this resulting from the elimination of a number of equipment items protecting against the potential effects of high pressure, in its operational reliability, and - finally - in its resistance to low temperatures of up to -40°C. Due to the absence of high pressure in the heat transfer system, the equipment system can be operated and used with considerable safety. A significant advantage of the low-pressure equipment system for the transport of solar energy lies in the fact that in extreme conditions, i.e. in the event of a sudden electricity failure, and in locations where power networks are unavailable it can operate with a photovoltaic battery as its power source. Another important advantage of the equipment system consists in the fact that is activated by a small temperature difference - totalling approximately 2°C - between the temperature measured at the solar collectors and the temperature of water measured in the cool part of the warm usable water tank.

A working drawing of the method of effecting the safe transfer of solar energy and the low-pressure equipment system for the transport of solar energy covered by the present invention has been presented in the illustration, where: Fig. 1 contains a diagram depicting the method of effecting the safe transfer of solar energy during system start and operation, with the gas pocket being filled with gas; Fig. 2 contains a diagram depicting the method of effecting the safe transfer of solar energy in a situation when no energy can be collected and when the system is inoperative, with the gas pocket being filled with transfer fluid; Fig. 3 contains a diagram of the equipment system for the transport of solar energy as provided for under the present invention; Fig. 4 and Fig.5 contain lists of apparatuses constituting system elements, installed on an exemplary modular system housing; Fig. 6 contains a diagram depicting the supply of electricity to the system from a photovoltaic battery; and Fig. 7 contains a diagram depicting the remote monitoring option for the solar energy transport system, which enables supervision from any point on earth.

The solar energy transport system covered by the present invention is activated when the circulating pump 11 is switched on. The medium 1_7 is then pumped into the pipeline, while gas 1_8 fills the space vacated in the low-pressure gas pocket _4; the system is now fully operational. In the course of normal operation, the entire volume of gas 1_8 is retained in the low- pressure gas pocket _4. When solar energy cannot be transferred, the system switches itself off, the medium

17 returns and occupies the gas pocket 4_, while the gas

18 moves to the pipeline and the solar collector channels 2. An example of the equipment system for the transport of solar energy covered by the present invention comprises a modular housing 1_4, inside of which there is located a drainage tank ,5 fitted with a switch _12_. for controlling the level of transfer fluid, a heat exchanger _β, a circulating pump of the primary circuit 1_1, a circulating pump of the secondary circuit 10_, and a control system 1_3. The system is additionally fitted with a photovoltaic battery 1_9, an accumulator 25, and a regulator 20. The equipment system for the transport of solar energy possesses a primary solar circuit 1_, which comprises solar collectors 2_, connected via pipes 3_ with module 14 for the transfer of solar energy. The transfer fluid flows inside the pipes 3 and is forced out of the drainage tank 5 to the collectors 2_, where- from it returns after taking energy from the heat exchanger _6, where it comes into contact with the second - water - circuit 1_. The second circuit 1_ is directly connected via pipes _3 with a separate warm usable water tank. By means of the circulating pump 10, cold usable water is pumped from the warm usable water tank and through the internal heat exchanger _6, where- from it returns to the warm usable water tank after first taking energy. The mobile telephony-based control and supervision system comprises a processor that receives signals through a modem 2_4, the telephone network, a PC 22_, or a mobile telephone 23.

Claims

Patent claims

1.Method of effecting the safe transfer of solar energy, consisting in the transport of solar energy from solar collectors to a heat exchanger and back to the solar collectors by forcing the circulation of a medium utilising high-pressure circulating pumps, distinguishable by the fact that a closed low- pressure gas pocket (A ) is introduced to the closed circuit of transfer fluid (17) that transports solar energy from the solar collectors (2) to the heat exchanger (_6) , whereas if conditions are not appropriate for utilising solar energy, the transport medium (17_) is secured and fills the low-pressure gas pocket ( A ) , while the solar collectors (2) and pipeline supplying the transfer fluid to the solar collectors (2 ) are filled with gas (1_8) , while when it becomes possible to utilise solar energy, the circulating pump (1_1) is activated and forces the medium ( 11 ) into the pipeline, simultaneously forcing the gas (1_8) out of both the pipeline and the solar collectors (2) into the low-pressure gas pocket ( A ) , and subsequently the transfer fluid (17) , assisted by the circulating pump (11) and under a pressure not exceeding 100 kPa, flows through the solar collectors ( 2 ) , absorbs heat and is then forced into the heat exchanger (_6) , where it gives up its heat to the water, while the gas (1_8) remains in the low- pressure gas pocket (_4) , and when darkness falls or in any other instance when it becomes impossible to utilise solar radiation energy, the circulating pump

(11) is switched off, while the transfer fluid (17) flows of itself to the low-pressure gas pocket (4), while the gas (1_8) travels to the medium circuit pipes and to the solar collector channels (2) .

2. The method pursuant to claim l _r distinguishable by the fact that the volume of the low-pressure gas pocket ( ) is such that it is able to contain the entire - or nearly the entire - quantity of the medium ( 11 ) in the circuit which absorbs heat from the solar collectors (2) .

3. The method pursuant to claims 1 and 2, distinguishable by the fact that the medium (17) which transports solar energy is a propylene glycol- based solution that contains anticorrosive and antiexpandable additives.

4. The method pursuant to claims 1, 2 and 3, distinguishable by the fact that the gas (1_8) in the closed circuit is air.

5. low-pressure equipment system for the transport of solar energy, comprising solar collectors, a pipeline transporting the medium, a heat exchanger, high- pressure circulating pumps, connected via high- pressure pipes, and also a control system, distinguishable by the fact that it utilises two independent circuits, whereas the primary transfer circuit ( 1 ) , used to transport transfer fluid (27) , is made up of solar collectors ( 2 ) connected by means of pipes (_3) with a heat exchanger ( 6) , which is connected via pipes (_3) and through a drainage tank ( 5 ) with the circulating pump of the primary circuit (11) and the solar collectors (2), whereas the pipes of the primary transfer circuit (_1) connecting the equipment system covered by the present invention with the solar connectors (2 ) are inclined in the direction of the module (1_4) , while the secondary transfer circuit (1_) comprises a circulating pump of the secondary circuit (1_0) , installed on the pipeline which supplies cold water to the heat exchanger ( 6 ) , and pumps which carry hot water away from the heat exchanger (_6) to the usable warm water t^ank, whereas both the primary and secondary transfer circuits are equipped with a control system (1/3) .

6. he system pursuant to claim 5, distinguishable by the fact that the heat exchanger ( 6) is a panel-type heat exchanger.

7. he system pursuant to claim 5, distinguishable by the fact that the drainage tank (5) is fitted with a switch (1_2) for controlling the level of transfer fluid.

8. The system pursuant to claim 5, distinguishable by the fact that the inclination of the pipes (_3) of the primary transfer circuit (_1) in the direction of the module (14) is at least 5°.

9. The system pursuant to claim 5 distinguishable by the fact that it is equipped with a photovoltaic battery (JL9) power supply, with the battery being coupled with a regulator (20) and accumulator (25) .

10. The system pursuant to claims 5 and 9, distinguishable by the fact that the control system (13) monitors the temperature in the cold part of the usable warm water tank and on the solar collectors (2) , so as to detect when a sufficient quantity of solar energy has been collected.

11. The system pursuant to claims 5, 9 and 10, distinguishable by the fact that it is equipped with apparatuses that control water and transfer fluid temperatures at every point of their respective circuits .

12. The system pursuant to claims 5, 9 and 11, distinguishable by the fact that it is equipped with a kit for measuring the total quantity of heat transferred to the water during system operation.

13. The system pursuant to claims 5 and 12, distinguishable by the fact that the control system of the equipment system is fitted with a processor and modem (2_4) , which enable the monitoring of the process of solar radiation transformation using a PC (22) .

14. The system pursuant to claim 13, distinguishable by the fact that it has installed special software and an installation enabling connection of the PC (22) with the Internet, this for the purpose of supervising the equipment system covered by the present invention by means of mobile telephony (23) .