GB1563076A

GB1563076A - Heat accumulators

Info

Publication number: GB1563076A
Application number: GB20506/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-05-17
Filing date: 1977-05-16
Publication date: 1980-03-19
Also published as: FR2352255B2; FR2352255A2; DE2621819B2; ATA299977A; NL7705247A; LU77327A1; IT1117672B; AT371584B; DE2621819A1; CH621621A5; BE854515R

Abstract

The heat store has a hood-shaped housing part arranged in the earth (14) and made from a thermally insulating material which surrounds from above and at the sides a compound (32) which is capable of storing heat. It is provided with a primary pipe circuit (16), which is inserted into the housing part and connected to a thermal energy receiver, as well as with a secondary pipe circuit (34), which is likewise inserted into said housing part and connected to the thermal energy consumer. The housing part is sealed at its lower end by a floor (28) made from thermally insulating material. The primary pipe circuit (16) is guided through above this floor (28) an the secondary pipe circuit (34) is guided through and below the ceiling (30) of the housing part. This heat store has low losses and a high efficiency. Downward thermal radiation is largely prevented by the floor (28) made from thermally insulating material. <IMAGE>

Description

(54) HEAT ACCUMULATORS (71) I, ARTUS FEIST a citizen of the Federal Republic of Germany (West Germany) of Weidenweg 9, 5060 Bensberg Refrath, West Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to heat accumulators.

The invention is concerned with utilizing sources of natural energy for heating purposes and in particular with apparatus for gathering radiant energy from the sun. This is collected by solar collectors. A liquid medium, which is water in the technologi cally simplest form, is heated with this energy. The operating costs of a solar collector are low. However, the difficulty lies in the fact that the amount of solar energy which is received during the daily and annual cycles varies very considerably and never coincides with the actual demand. Thus, heat accumulators are necessary.There are already known heat accumulators based on chemicals, heat accumulators in which energy is stored in the form of hot water, and also heat accumulators in which earth, rocks and sand are used as the storage medium, since it is available virtually free and its thermal capacity is approximately 1.8 times the thermal capacity of water.

Earth head accumulators of this type which are intended for houses are installed in the garden or simply in the area surrounding the house to be heated. For many reasons, amongst others, poor insulation and a low level of efficiency in the transfer of heat into the accumulator and out of the accumulator, the known heat accumulators need to have a large volume. Accordingly, a large area of ground must be removed for sinking and installing the various systems. This in turn gives rise to high costs. In addition, the area of ground which is available around a house or the piece of ground appertaining to a house is limited. With the known earth heat accumulators, therefore, the storing of solar energy from the period of the greatest incidence of heat in summer to the period of highest consumption in winter can only be achieved at considerable expense, or may not be possible at all.The idea of heating a house entirely with solar energy must therefore be completely abandoned, and solar derived energy must be considered as a supplement to a heating system which primarily uses other forms of energy, such as coat, gas, etc.

An underground heat accumulator comprising a heat insulating casing buried in the ground so that earth enclosed in the casing serves as a heat storage medium, a primary pipe circuit passing through the enclosed earth and a secondary pipe circuit likewise passing through the enclosed earth but out of the direct physical contact with the primary pipe circuit, the casing extending with clear- ance above and to the sides of the pipe circuits, is described and claimed in by British Patent Specification No. 1526024. In its construction the primary and the secondary pipe circuits are laid in sepentine coils. These coils of the two pipe circuits are arranged adjacent to each other on a common supporting surface. Then the soil is removed in the form of slits in several places around the house to be heated. Four such slits are interconnected.

The heat insulating material which forms the walls of the housing is lowered into these.

Inside these housing walls at an equal distance there are other slits. The supporting surfaces bearing the two pipe circuits are lowered into these. The whole is covered over with the heat insulating material which forms the top of the housing and filled in with more soil. To build this heat accumulator it is only necessary therefore to make slits in the soil at several points and to lower in the heat insulation and the supporting surfaces. This is a simple process and can be carried out easily with special excavators, after which the slits containing the heat insulating material and the supporting plates are covered with more head insulating material. The simplicity of this installation is offset by a certain disadvantage in that there is no insulation at the bottom of the housing. Heat can flow away into the surrounding soil.For this the heat must flow downwards over the lower edges of the housing walls out towards the bottom. Since heat is only transferred upwards and this flow of heat downwards would only occur when the heat accumulator was thermally loaded to capacity, the heat loss is small. Despite this, it can come to an appreciable amount, measured in absolute figures. The losses arising in this way are compensated for by more housings, or larger housings.

However, when a house is built in an area which is already densely populated only a little free area is available. Accordingly, the number and the volume of the housings is restricted. This leads to the desire for a heat accumulator with only insignificantly small losses. When a house is constructed in a densely populated area, frequently an excavation must be made with is larger than the actual ground plane of the house, in order to remove rubble and the remains of walls of earlier buildings. The problem was therefore posed of developing the proposed heat accumulator further, so that it is more efficient in operation, allowing if necessary, larger excavation works in its installing.

According to the present invention a heat accumulator comprises a housing having a base, walls and roof made of thermally insulating material which is buried in the ground and is filled with heat storing material and in which a primary pipe circuit is situated in the housing close to the base of the housing and a secondary pipe circuit also situated in the housing is located close to the roof of the housing, both circuits passing through the walls of the housing.

Any loss of heat downwards is prevented bv the base of thermally insulating material.

This gives small losses and a correspondingly higher level of efficiency. The provision of the base naturally requires the excavation of a correspondingly larger hole than for an accumulator of the type described in my Specification No. 1526024.

Heat introduced from below travels upwards naturally. towards the roof of the housing, where it accumulates. The secondary pipe circuit therefore alwavs lies in the warmest part of the housilng. In this way, the last remaining heat stored will still be conducted away out of the accumulator. even at the end of a winter period.

The construction of a heat accumulator embodying the invention thus ensures that heat is stored at no extra constructional cost, both without losses and also in such a way that to the very last remaining amount, the heat can be conducted away out of the heat accumulator.

To simplify construction the primary and secondary pipe circuits may be in the form of flat plates occupying different parallel planes in the housing. In this case the primary and the secondary pipe circuits are preferably arranged on supporting surfaces. Thus the two pipe circuits can each be individually laid on reinforcement wire mesh mats, wire netting or other supports and, if required, can be cast in concrete. Alternatively a framework of slats or battens can be made, and flexible pipes of hoses which form the pipe circuits can be attached to these with clamping straps or clips.

Preferably both pipes are coiled up in spiral or serpentine manner and are secured on, with or in supporting surfaces.

This spiral or serpentine form for the two pipe circuits makes possible a well-defined spatial correlation of the hot outflow and the cold return flow to a specific point inside the housing. This is based on the assumption that a point lying centrally in the housing is better insulated than the peripheral region of the housing. While the peripheral region is only insulated from the surrounding soil by the heat insulating material which forms the casing of the housing, the centrally located points inside the housing are additionally insulated by the substance contained in this, which has heat storing properties.

To make full use of this effect, provision is made in one embodiment of the invention for the hot section of the primary pipe carrying heated fluid from a thermal energy receiver to run into the centre of the spiral or serpentine coil and for its outer coil to return the fluid to the inlet end of the thermal energy receiver. In this way the heat is admitted at the point of greatest insulation. The heat travels upwards from a central point above the base and therefdre heats the heat storing material located there most strongly. The temperature of this material drops towards the less well-insulated peripheral region.

This reduces the loss of heat through the casing of the housing, which is dependent on temperature difference, and increases the efficiency of the heat accumulator.

To further exploit this effect, the secondary pipe circuit is connected to a thermal energy consumer so that fluid flow is from the centre of the upper coil.

The housing can be filled with any substance which has heat storing properties.

This can be the soil obtained from the excavation, rubble, remains of walls, lumps of concrete, mortar to be re-applied, sand, gravel, and any material which combines low cost with good heat storing properties.

The housing can be any geometric shape.

A rectangular or a cylindrical shape is expedient. Under certain circumstances the shape will be decided by the ground plan of the hole which may have been excavated for other reasons.

The volume of the housing depends on the storage capacity required and the space available. As a basis, it can be stated that the diameter of a cylindrical housing or the length of the sides of a rectangular housing will typically lie in the range 6 metres to 7 metres, and its height will typically lie in the range of 2.50 metres to 8 metres.

When using a heat accumulator according to the invention, the radiant energy from the sun, which may be collected by a solar collector, for example, at a temperature anywhere in the range from 50"F up to the boiling point of water, is introduced into the substance with heat storing properties via the primary circuit, which may have water flowing through it, for example. Over the length of the primary pipe circuit the heat is transferred into the substance with heat storing properties, which it heats up. The heating takes place inside the volume enclosed by the housing. In the ideal case the substance with heat storing properties is heated up to the highest temperature of the primary pipe circuit. The energy thus stored is drawn off as required, via the secondary pipe circuit.Both the pipe circuits have cocks or valves and are each open or shut according to the incidence of sunlight and the consumption of heat. At the end of a heating period in the late winter months the temperature inside the housing has fallen considerably. When the temperature lies only slightly above the ambient temperature, energy can be drawn off via a heat pump.

The invention will now be further described by way of example with reference to the accompanying drawing in which: Figure 1 is a cross-section through the heat accumulator, looking onto the spirally coiled primary pipe circuit, and Figure 2 is a vertical section through the heat accumulator.

Figure 1 shows a housing 12, made of heat insulating material. In the example shown it has a rectangular ground plan. It is surrounded by earth 14. In the housing 12 the spirally coiled primary pipe circuit 16 lies in one plane. Its centrally located inlet 18 is connected to the hot outflow end 20 of the thermal energy receiver 22. The outer coil 24 of the primary pipe circuit 16 leads to the cold inlet end 26 of the thermal energy receiver 22.

As shown in Figure 2, the housing 12 is closed off at the bottom by a base 28 and at the top by a cover 30. Inside the housing formed there is a substance 32 with good heat storing properties. Figure 2 also shows the primary pipe circuit 16 (already described). Its coils are indicated by the small circles which represent a cross-section through the turns of a flexible pipe or hose.

In the example shown this hose lies in a layer of concrete. At the centre point of this layer the inlet 18 runs in. Immediately under the cover 30 there is the secondary pipe circuit 34, also spirally coiled. The section of pipe 38 which leads to the inlet 36 of the thermal energy consumer comes out at the centre. As shown in Figure 2, the heat accumulator lies under a layer of earth 14, which is sown with grass 40, or may also be concreted, paved or covered in some other way, or it can also be left free.

WHAT I CLAIM IS: 1. A heat accumulator comprising a housing having a base, well and roof thermally insulating material which is buried in the ground and is filled with heat storing material, and in which a primary pipe circuit is constructed in the housing close to the base of the housing and a secondary pipe circuit also situated in the housing is located close to the roof of the housing, both circuits passing through the walls of the housing.

2. A heat accumulator as claimed in claim 1 in which the primary and secondary pipe circuits lie in two spaced apart parallel planes in the housing.

3. A heat accumulator as claimed in claim 1 or 2 in which each of the primary and secondary pipe circuits is arranged on, secured to or embedded within a supporting means.

4. A heat accumulator as claimed in claim 3 in which each of the primary and secondary pipe circuits is coiled in a spiral or serpentine.

5. A heat accumulator as claimed in claim 4 in which heated fluid from a thermal energy receiver is fed to the centre of the primary pipe circuit coil.

6. A heat accumulator as claimed in claim 4 in which fluid in the secondary pipe circuit is fed from the centre turn of the secondary pipe circuit to a heat energy consumer.

7. A heat accumulator as claimed in claim 6 in which the outer coil of the secondary pipe circuit is connected to the cold return end of the thermal energy consumer.

8. A heat accumulator as claimed in any of claims 1 to 7 in which the housing is filled with earth.

9. A heat accumulator as claimed in any of claims 1 to 7 in which the housing is filled with a material such that the mass of material has a high thermal capacity.

10. A heat accumulator as claimed in any of claims 1 to 9 in which the housing is cylindrical.

11. A heat accumulator as claimed in any of claims 1 to 9 in which the housing has rectangular sides and base.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A rectangular or a cylindrical shape is expedient. Under certain circumstances the shape will be decided by the ground plan of the hole which may have been excavated for other reasons. The volume of the housing depends on the storage capacity required and the space available. As a basis, it can be stated that the diameter of a cylindrical housing or the length of the sides of a rectangular housing will typically lie in the range 6 metres to 7 metres, and its height will typically lie in the range of 2.50 metres to 8 metres. When using a heat accumulator according to the invention, the radiant energy from the sun, which may be collected by a solar collector, for example, at a temperature anywhere in the range from 50"F up to the boiling point of water, is introduced into the substance with heat storing properties via the primary circuit, which may have water flowing through it, for example. Over the length of the primary pipe circuit the heat is transferred into the substance with heat storing properties, which it heats up. The heating takes place inside the volume enclosed by the housing. In the ideal case the substance with heat storing properties is heated up to the highest temperature of the primary pipe circuit. The energy thus stored is drawn off as required, via the secondary pipe circuit.Both the pipe circuits have cocks or valves and are each open or shut according to the incidence of sunlight and the consumption of heat. At the end of a heating period in the late winter months the temperature inside the housing has fallen considerably. When the temperature lies only slightly above the ambient temperature, energy can be drawn off via a heat pump. The invention will now be further described by way of example with reference to the accompanying drawing in which: Figure 1 is a cross-section through the heat accumulator, looking onto the spirally coiled primary pipe circuit, and Figure 2 is a vertical section through the heat accumulator. Figure 1 shows a housing 12, made of heat insulating material. In the example shown it has a rectangular ground plan. It is surrounded by earth 14. In the housing 12 the spirally coiled primary pipe circuit 16 lies in one plane. Its centrally located inlet 18 is connected to the hot outflow end 20 of the thermal energy receiver 22. The outer coil 24 of the primary pipe circuit 16 leads to the cold inlet end 26 of the thermal energy receiver 22. As shown in Figure 2, the housing 12 is closed off at the bottom by a base 28 and at the top by a cover 30. Inside the housing formed there is a substance 32 with good heat storing properties. Figure 2 also shows the primary pipe circuit 16 (already described). Its coils are indicated by the small circles which represent a cross-section through the turns of a flexible pipe or hose. In the example shown this hose lies in a layer of concrete. At the centre point of this layer the inlet 18 runs in. Immediately under the cover 30 there is the secondary pipe circuit 34, also spirally coiled. The section of pipe 38 which leads to the inlet 36 of the thermal energy consumer comes out at the centre. As shown in Figure 2, the heat accumulator lies under a layer of earth 14, which is sown with grass 40, or may also be concreted, paved or covered in some other way, or it can also be left free. WHAT I CLAIM IS:

1. A heat accumulator comprising a housing having a base, well and roof thermally insulating material which is buried in the ground and is filled with heat storing material, and in which a primary pipe circuit is constructed in the housing close to the base of the housing and a secondary pipe circuit also situated in the housing is located close to the roof of the housing, both circuits passing through the walls of the housing.

12. A heat accumulator as claimed in any

of claims 1 to 11 in which the housing has a diameter or a side length in the range 6 metres to 7 metres.

13. A heat accumulator as claimed in any of claims 1 to 12 in which the height of the housing lies in the range 2.50 metres to 8 metres.

14. A heat accumulator constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.