FI124800B - Solar heating system for a building - Google Patents

Description

BUILDING SOLAR HEATING SYSTEM FIELD OF THE INVENTION

The present invention relates to a solar heating system for a building as defined in the preamble of claim 1.

BACKGROUND OF THE INVENTION

Prior art in the field of the invention is disclosed, for example, in CN101650098 and US2007214815. In pursuit of less energy-consuming buildings and away from fossil energy sources, more and more direct heat from the sun and soil heat has been used to heat buildings. The systems are largely based on ground source heat pumps and air source heat pumps, which usually provide more than half of the required energy from soil, water or air, are complex, expensive and maintenance-intensive and require at least one third of the total electricity requirement.

On the other hand, solar thermal systems currently in use have poor annual efficiency. They can heat about half of the hot water used by the property and cover 10-20% of the total heating energy used by the property.

PURPOSE OF THE INVENTION

The object of the invention is to overcome the above-mentioned drawbacks of the prior art. In particular, it is an object of the invention to provide a new type of solar heating system for buildings, whereby most of the thermal energy required by a building is obtained from so-called free energy. It is a further object of the invention to provide a simple, reliable, maintenance-free solar system with minimal space inside the building.

SUMMARY OF THE INVENTION

The solar heating system according to the invention has started from two basic ideas. First of all, the system must be operating without an air source heat pump or a ground source heat pump, so that in the normal operation of the system, all the energy used must, as far as possible, be obtained as direct solar heat or geothermal heat. However, this does not eliminate the possibility that in some applications heat pumps may be used. Secondly, there are a large number of different and variable energy states in and around buildings, such as variations in solar thermal radiation depending on the time of day and season, indoor temperature, outdoor temperature, underground temperature, near water temperature etc. between which heat can almost always be transferred direction only with mass flow directions and simple heat exchangers.

The solar heating system of a building according to the invention comprises a liquid collector solar collector, a liquid-filled heat accumulator and at least one heat exchanger in the heat accumulator for utilizing the heat stored in the accumulator. The heat reservoir is a vertically elongated reservoir, i.e. a reservoir, which, due to its height, provides a clear temperature difference between its upper fluid and lower fluid. Further, the fluid circulation of the solar collector is arranged to open at the top of the heater, fill the entire heater and thus surround one or more heat exchangers used, and finally exit from the lower part of the heater back to the solar collector. Such a high and relatively narrow heat reservoir provides a large temperature difference between its upper and lower ends and the fluid used and circulating inside the container is not mixed in the container but slowly descends in the container according to the magnitude of the circulation.

An essential part of the invention is thus a relatively high and narrow heat insulated container forming a heat reservoir filled with a heat transfer medium of the solar circuit. When the container is sufficiently high relative to its horizontal diameter, no significant liquid mixing occurs in the container. Thus, the heat reservoir is a vertical tube having a height of at least 10, preferably greater than 20 and even of the order of 100 times its diameter. It can even be said that the heat reservoir is formed by the vertical portion of the solar collector fluid circulation tube, where the liquid passes from top to bottom and the tube diameter is significantly larger than elsewhere in the liquid circulation. Thus, in this expanded region of the tube, the flow rate is significantly lower than elsewhere, but substantially no mixing of the liquid occurs along the length of the tube. At the top of the tank, the temperature of the liquid may be as high as about 90 ° C, while at the bottom the temperature of the liquid is only about 4 ° C. Thus, the temperature in the container rises relatively evenly from the bottom up. This allows thermal energy flows at different temperature levels to be transferred to or from the container.

Because the height and width of the heat accumulator are essential for the functionality of the system according to the invention, it is preferably located in the building to extend substantially throughout its height or at least to the highest possible free space in the building. Thus, for example, in a block of flats, a heat sink may be located in the stairwell and fill the middle shaft of the staircase from floor to ceiling or may be located in a generally disused waste bin. In the absence of a suitable space inside the building, it can also be placed well insulated against the exterior wall of the building.

In one embodiment of the invention, the at least one heat exchanger is a hot water circulation heat exchanger in a building arranged to extend substantially over the entire height of the tank. The heat exchanger may be a spiral or other tubular structure extending throughout the height of the container. In a preferred embodiment, the heat exchanger comprises a lower heat exchanger at the bottom of the tank and an upper heat exchanger at the top of the tank, and a connecting pipe connecting them. In this way, the lower heat exchanger is supplied with cold raw water, which is primarily intended to cool the liquid leaving the tank to the solar collector to the lowest possible temperature. The top heat exchanger then heats the hot water circulation to the top of the tank. Generally, the hot water thus obtained is too hot to be used as hot water, so the hot water obtained must be supplied to the mixing valve before use.

The connecting pipe between the upper and lower heat exchangers is intended only for the transfer of liquid between the heat exchangers, i.e. no heat transfer from the tank to the water is required in the connecting pipe. In this way, the connecting pipe may be thermally insulated and may be located either inside the container or equally well outside the container.

In one embodiment of the invention, the system comprises a heat recovery device connected to the liquid circulation of the solar collector and operating in parallel with the solar collector, which may be, for example, an exhaust heat pump for transferring heat energy from air to water. It can be controlled according to the ambient temperatures so that the heat from the exhaust air is recovered when there is not enough heat from the solar collector. Of course, the system can also use the known pre-heating of the supply air with exhaust air.

In one embodiment of the invention, the system comprises a soil-mounted heat exchanger for heating or cooling the fluid circulation in conditions connected to the fluid circulation of the solar collector. A ground-based heat exchanger is a piping system located below the frost boundary, which may be submerged in the ground or water, or may be located in a well, for example. For example, an oxygen diffusion-protected underfloor heating pipe can be used as a pipe for a ground pipe. The pipelines provide geothermal heat but can also be used to cool the air circulation in the building's rooms on hot summer days.

The high accumulator according to the invention is provided with heat for short-term needs. For a longer period, that is months, and for the winter, heat can be stored in a heat accumulator, which can be the actual earth circuit, such as a number of wells drilled into the bedrock. The heat accumulator may also be a well-insulated water tank, such as a hemispherical tank located under the house. The size of the tank is optimized based on the heat requirement and, for example, whether or not a heat pump is used to discharge heat from the battery. It is also possible to use a heat cellar, that is, a part of a full-height basement or a raised floor area of the entire house. The heat accumulator or heat cellar can be implemented, for example, in a swimming pool bag made of PVC. The bag may be made with a second bag inside the outer bag. This leaves a closed space inside the bags. For connection, fill-up and maintenance, the bags are provided with a through flange. through the flange the gap can be filled with insulation such as EPS granules or light gravel. In addition, the closed space can be pressurized with a poorly conductive gas such as argon. Vacuum can also be sucked into the enclosed intermediate space for improved thermal insulation. For vacuum, the space must be filled with material that does not collapse so that the material would begin to conduct heat despite the vacuum.

When using a heat pump, the temperature of the fluid in the accumulator may be lower, for example 15-25 ° C. This reduces heat loss and requires less insulation. If the heat pump is not in use, the temperature of the liquid must be about 25-35 ° C in order to keep the house warm. This increases heat loss and the need for insulation.

In one embodiment of the invention, the system comprises a building air supply pre-heater connected to the solar circuit fluid circuit. Alternatively, by controlling the fluid circulation accordingly to the prevailing temperatures, fresh supply air to the building may be preheated by heat from the solar collector, heat from the heat sink, or geothermal from the soil. Correspondingly, the same arrangement can be used to cool the supply air by a liquid circulation in the soil during summer.

In one embodiment of the invention, the system includes a heat exchanger associated with a suitable portion of the height of the heat reservoir in connection with a heat distribution facility in the building, such as a radiator network or underfloor heating. In this way, in addition to hot water, the heat sink provides optimum heating energy for the interior of the building. This heat exchanger can only be placed in a heat reservoir at a certain suitable height so that the water circulating in the heat distribution equipment is suitably heated. It is even possible for this heat exchanger to have two or more parts so that the water is heated by circulating water only with a part of the heat exchanger, such as at the top, middle or bottom depending on the temperature of the heat exchanger fluid at different parts of the heat exchanger.

In principle, all types of solar collectors can be combined with the system of the invention to transfer solar heat to the heat storage fluid. To maximize the benefits of the system throughout the year, choosing a solar collector is of great importance. The optimum result may not be achieved with only one type of collector or with only one angle fixed to the ground or only with one-way fixed collectors. Thus, preferably, a solar tube concentrating solar radiation is provided as a solar collector and is provided with a rotatable paraboloid reflector with a focal point positioned within the vacuum tube. In this way, even in harsh winter, the sun shines in the system, and on the other hand, the summer overheating can be prevented by turning the reflector away from the sun to shield the vacuum tube, which acts as an absorber.

For example, solar collectors can be horizontally rotating solar heat collectors with CPC reflectors inclined so that even though the collector is upright to minimize snow loads, the reflectors are inclined at 27 degrees. The reflection angle of the reflectors can be 55 degrees, which corresponds to the maximum height of the sun in Finland. Further, the reflectors may be lower at their outer ends than in the center of the collector, so that snow and water drain out of the trough formed by the reflector.

In situations where the temperature of the top of the heater is not high enough to heat the domestic hot water to a high enough temperature, an electric flow heater may be used. It is connected in series with the hot water coil downstream, so that if the water is not warm enough after the heat accumulator, the flow heater will automatically switch on and raise the water temperature to a suitable level, for example about 55 ° C. In most cases, however, throughout the year the temperature of the heat accumulator is higher than the maximum allowable temperature for hot water. Therefore, a hot water circulation should include a mixing valve for adding cold water to the circulation before using the water.

As will be appreciated from the foregoing description, the system of the invention can be used in many different ways and always controlled for energy flows according to need and availability. Essential to the invention is a high heat accumulator which, due to its height, provides a significant temperature difference between its top and bottom, and in which heat is supplied by top-down heat flows and heat is taken by bottom-up liquid flows. Further, it is essential to the invention that, by continuously monitoring the system and associated temperatures, it is always possible to optimally transfer and recover thermal energy. Further, it is essential for the system that heat is always transferred from a higher temperature to a lower temperature, that is, through natural energy transfer. However, this does not preclude the use of electrically driven heat pumps in the system when energy efficient.

The structure according to the invention is particularly suitable for multi-storey houses such as apartment blocks as well as for example two-storey detached houses with basements where the total height of the building is already almost 10 meters. This high and narrow heat reservoir can be optimized to operate.

The solar heating system of the building according to the invention provides significant advantages over the prior art. Conventional solar heating systems provide about half of the annual hot energy required for hot water and 10-20% of the total heat required by the building. In the system according to the invention, by measuring and comparing the temperatures of different sites, optimizing the heat fluxes properly, and using techniques that require little external energy, i.e. using pumps that mainly use only the necessary fluxes, 40-60% of the total thermal energy required in the building.

In addition, due to the simple design of the system, with only pumps and stable piping and heat exchangers, its investment costs, as well as operating and maintenance costs, are very low compared to conventional solutions. One of the most advantageous target groups for the system according to the invention is the old blocks of flats with gravity or exhaust ventilation, where the most cost-effective solution is to also use an exhaust heat pump.

LIST OF FIGURES

The invention will now be described in detail with reference to the accompanying drawings, in which Fig. 1 is a schematic diagram of an auxiliary heating system according to the invention and Fig. 2 is a diagrammatic view of another auxiliary heating system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

For example, in a block of flats, the building's solar heating system according to Figure 1 comprises a heat store 2, or a tubular tank, which extends the staircase size of the building or at least almost the entire height. The system also has a solar collector 1, preferably a centralized vacuum tube collector, from which the heated fluid circulation 11 is directed to the upper part 4 of the heat accumulator 2. The cooled return cycle 12 is output from the lower part 5 of the heat accumulator 2.

In addition, the heat accumulator 2 generally has a heat exchanger 3 formed of a copper coil, which can extend substantially throughout its height. Usually, however, the heat exchanger is located only in a portion of the heat sink, for example at the top, i.e. the hottest part. In Figure 1, the heat exchanger is shown as only one straight pipe. The flow of water in the heat exchanger 3 is opposite to the downward flow in the heat reservoir. Thus, from the hot water supply 13, water flows through the lower part 5 of the heat accumulator through the heat exchanger 3 to the upper part 4 of the heat accumulator 2 and further to the mixing valve 14. Cold water is drawn into the mixing valve if necessary.

Further, the heat accumulator 2 has a second, bottom-up heat exchanger 9, which is connected to the radiator or underfloor heating circuit of the building. The heat exchanger 9, i.e. the coil, is placed in the heat reservoir only at a certain height to reach, for example, 1-2 meters in the height direction. The height is chosen to provide enough hot but not too hot circulation water in all circumstances.

In the embodiment shown, the coil also has a tap-off 30. Thus, the return pipe 17 of the radiator network is connected to the lower part of the heat exchanger 9 and the outlet pipe 18 to the upper part thereof. Appropriate selection valves (not shown), known per se, can switch either return flow 17 or outlet 18 flow to tap 30. Thus, depending on the temperature of the heater at different altitudes, relatively uniform heat is circulated throughout the coil, at the bottom or only at the top.

An expansion tank 19 and a safety valve 20 are also coupled to the heated fluid circuit 11 from the solar collector 1, because with efficient concentrating solar collectors, temperatures and pressures can be dangerously high. In this embodiment, the system also includes a building exhaust air heat recovery device 6. It is coupled in parallel with the solar collector 1 so that the liquid stream pumped by the pump 21 from the return cycle 12 is controlled from the three-way valve 22 to provide more heat to the liquid stream. Liquid circulation 12-11 thus passes through a heat recovery device 6 in which the exhaust air 23-24 to be removed from the building moves upstream. In a preferred embodiment, the heat recovery device 6 is a heat pump, which uses external energy but which effectively recovers heat energy from the exhaust air.

In the system of Figure 1, the optimization of energy use and system operation is based on several measurements. The system compares and optimizes the amount of heat produced and consumed as is known per se and directs the heat to where it is most useful in any given situation of heat generation and consumption. Examples of measurement points include:

T1 fluid from solar collector 1, T2 fluid from heat recovery unit 6, T3 fluid from heat reservoir.

Figure 2 illustrates another embodiment of the invention having a vertical, high and tubular heat accumulator 2 similar to Figure 1 filled with the same heat transfer fluid circulating through solar collector 1. The heat accumulator 2 has a heat exchanger 3 which communicates with the hot water supply 13 for supplying the cold 15 and hot 16 hot water of the building to the mixing valve 14. In this embodiment, an additional auxiliary heater 10 is automatically connected to the hot water circuit. sufficient. Solar collector 1 is fluidly connected 11 to heat reservoir upper part 4 and return cycle 12, respectively, from heat reservoir 2 lower part 5 via pump 21 back to solar collector 2. Liquid circuit 11 has an expansion tank 19 and a safety valve 20. The heat exchanger 3 has two parts the upper heat exchanger 31 and the lower heat exchanger 32 and the connecting pipe 33 connecting them. Both heat exchangers 31 and 32 are, for example, copper coils having a height of, for example, about 5-10% of the height of the heat reservoir, for example 0.5-1 m. 32, it effectively cools the liquid entering the solar collector and thus effectively recovering heat from the solar collector. In the upper heat exchanger 31, the already slightly warmed water warms up to at least the temperature of the hot water before final adjustment of the hot water temperature via the mixing valve 16. The connecting pipe only connects the two heat exchangers 31 and 32 to one another, since no heat exchanger is required at full height of the tank. The connecting tube may pass inside the container or equally well outside. In this way, the heat exchangers 31 and 32 are small and separate and their maintenance and installation at the top and bottom of the tank are easy compared to a single heat exchanger. In addition, by using only the necessary parts of the entire height of the heat reservoir, the fluid flows of the heat reservoir are vertically calm and turbulent. With such a high heat reservoir, the warm liquid mass flows down steadily and slowly while its temperature drops relatively steadily.

Further, in the embodiment of Figure 2, the system includes a heat exchanger 8 utilizing the heat of the earth. It may be a sufficiently long pipe submerged in the ground below the frost, a pipe inserted into a body of water such as a lake or drilled in a hole. The heat exchanger 8 is supplied via a three-way valve 25 in return cycle 12 between pump 21 and solar collector 1. The return flow of the heat exchanger 8 is arranged to a three-way valve 26 located between the solar collector 1 and the heat accumulator 2 in the fluid circuit 11. Thus, when the solar collector 1 does not produce heat, the fluid pumped by pump 21 can be controlled by the three-way valve 25 via valve 26 to heat accumulator 2.

Further, the system of Figure 2 includes a building outdoor preheater / cooler 7. The outdoor air 27 flows to the preheater and through it preheated to the room 28. The preheating operates with the same fluid circulation through solar collector 1, heat accumulator 2 and heat exchanger 8 as follows. Between the three-way valve 26 and the heat exchanger 8 there is a tap 29 from which the liquid can circulate to the preheater 7. The fluid exits and connects to the return circuit 12 between the heat accumulator 2 and the pump 21. By measuring the liquid and gas flow temperatures T1 to T5 at different points, the three-way valves 25 and 26 can be controlled to achieve optimum energy supply. For example, whenever the outdoor air is colder than a suitable indoor air, it is advisable to heat it wherever possible. Similarly, in freezing temperatures, it is advisable to heat the supply air as warm as the heat of the earth can be obtained by means of the heat exchanger 8, since this energy is free.

Further, the system can be used equally cheaply without the use of essential external energy to cool the excessively warm supply air during summer time. In this case, closing the three-way valve 26 completely and directing the liquid flow from the three-way valve 25 to the heat exchanger 8 of the pump 21 causes the liquid flow to cool in the ground and thereby cool the supply air in the heat exchanger 7. Similarly, other excess heat can be fed into the ground during the summer and reserved for land use for later use.

It should be noted that the system according to the invention is not intended to cover the entire heating energy requirement of a building throughout the year, but is intended to make the best economic use of the free energy flows available at different times of the year. Thus, the system needs additional energy at some point during the year. This additional energy can be obtained in various ways from the district heating, district heating, various available waste heat, combustion processes in boilers and fireplaces, ground source heat pump, air heat pump, etc., as is known per se.

For example, a fireplace in which the excess or even all of the heat is recovered by suitable flue gas cycles in a high heat reservoir can easily be combined with the system of the invention. From there, the heat can then be distributed to applications by the same means and means as the heat collected from the solar collector. The tall, well-insulated tank, which can be up to several cubic meters in a small house, can serve as the main source of heat in a building heated for several days while utilizing geothermal and solar radiation wherever possible.

The invention is not limited to the above examples only, but many modifications are possible within the scope of the inventive idea defined by the claims.

Claims (10)

A solar heating system for a building comprising a liquid-circulating solar collector (1), a liquid-filled heat accumulator (2) and at least one heat exchanger (3) for utilizing heat stored in the accumulator, the heat accumulator (2) being vertically elongated in the characterized by the fact that the heat sink (2) is a vertical pipe having a height of at least 10, preferably more than 20 and even orders of magnitude 100 times. its diameter. A system according to claim 1, characterized in that the heat accumulator (2) is located in the building extending substantially over its entire height, such as from floor to ceiling in the stairwell or at the full height of the debris shaft. System according to Claim 1 or 2, characterized in that the heat exchanger (3) is a heat exchanger for hot water circulation in the building arranged to extend substantially over the entire height of the tank. System according to Claim 3, characterized in that the heat exchanger (3) comprises an upper heat exchanger (31) and a lower heat exchanger (32) and a connecting pipe (33) connecting them. System according to one of Claims 1 to 4, characterized in that the system comprises a heat recovery device (6), such as a heat pump, connected to the liquid circulation of the solar collector (1) and parallel to the solar collector. System according to one of Claims 1 to 5, characterized in that the system comprises a building air supply preheater (7) connected to the liquid circulation of the solar collector (1). System according to one of Claims 1 to 6, characterized in that the system comprises a ground-mounted heat exchanger (8) connected to the fluid circulation of the solar collector (1) for heating or cooling the fluid circulation according to the conditions. System according to one of Claims 1 to 7, characterized in that the system comprises a heat exchanger (9) connected to the building's radiator network extending for part of its height inside the heat accumulator (1). System according to one of Claims 1 to 8, characterized in that the solar collector (1) is a vacuum tube collector, which is preferably provided with a rotatable paraboloidal reflector, to which the vacuum tube is located. System according to one of Claims 1 to 9, characterized in that an additional heater (10), such as an electric heater, is provided in connection with the hot-water circulation of the building for additional heating of hot domestic water, if necessary.