WO2015028471A1

WO2015028471A1 - Heat storage device for a greenhouse

Info

Publication number: WO2015028471A1
Application number: PCT/EP2014/068093
Authority: WO
Inventors: Uwe Schmidt
Original assignee: Humboldt-Universität Zu Berlin
Priority date: 2013-08-29
Filing date: 2014-08-26
Publication date: 2015-03-05
Also published as: DE102013217289B3

Abstract

The invention relates to a heat storage device (1) for a greenhouse comprising at least one storage reservoir (2), a storage fluid (3) which is introduced into the storage reservoir (2) and forms a surface (30), for storing heat and a heating system for a greenhouse (8), said system being connected to the storage reservoir (2) in such a way that storage fluid (3) can be introduced into the heating system. Additionally a covering device (4) is provided which is disposed floating on the surface (30) formed by the storage fluid (3) and covers the surface (30). In this way a heat storage device for a greenhouse is created, which in a simple, cost-effective manner enables the storage of heat even over a relatively long period of time.

Description

Heat storage device for a greenhouse

description

The invention relates to a heat storage device for a greenhouse according to the preamble of claim 1 and a greenhouse installation with a heat storage device.

Such a heat storage device for a greenhouse comprises at least one storage tank, a storage liquid which is filled in the storage tank and forms a surface for storing heat and a heating system of a greenhouse, which is in communication with the storage tank such that storage liquid introduced into the heating system can be.

From greenhouses solar energy can be obtained by using a cooling system, for example by means of suitable heat pumps. The energy production in greenhouses can have a considerable efficiency of, for example, 50%, so that the solar energy production in a greenhouse can be economically interesting. However, in order to use the heat gained in a greenhouse for the heating of the greenhouse, the heat must be stored for a long time, so that the heat obtained, for example, on warm days for heating, for example, on cold days can be kept in stock.

The use of currently customary small-volume and well-insulated day-night storage has proven to be uneconomical due to a relatively low efficiency, especially because bridging longer periods of time with cold nights and days with little sunlight are not readily realized with such small-volume storage can. Investigations for the development of aquifer reservoirs have therefore been undertaken where water is stored in the earth at a depth of 50 to 300 m to store heat. However, the energy required to transport the water, the cost of drilling and the underground heat losses are currently causing such aquifer stores to be uneconomic.

Regardless of heat storage, today many greenhouses have aboveground reservoirs in the form of simply built metal tanks or artificially created ponds that store rainwater for irrigation of plants.

There is a need for a heat storage device that can be comparatively simple and inexpensive, but allows storage of heat over a longer period to bridge cold day and night periods.

From DE 36 16 623 A1 discloses a floating roof for tanks for holding liquids is known, which consists of a fixed to floats, compliant disc. The tank serves to hold liquids to be stored, for example of oils or paraffin-containing middle distillates, but not as a heat storage device of a greenhouse system.

From EP 2 299 499 A1, a floating photovoltaic array is known, which is connected to a hydroelectric power plant at a reservoir or a coastal water to feed photovoltaically generated electricity into a power grid of the hydroelectric power plant.

Object of the present invention is to provide a heat storage device for a greenhouse and a greenhouse system with a heat storage device available that allow the storage of heat over a longer period of time in a simple, cost-effective manner.

This object is achieved by an article having the features of claim 1. Accordingly, the heat storage device has a covering device, which is arranged floating on the surface formed by the storage liquid and covers the surface. The present invention is based on the idea of using a water storage system in a greenhouse system, as it is often provided, for example, for receiving rainwater, as a heat storage device. Such a water reservoir is regularly formed as a surface storage, for example in the form of an at least partially embedded in the ground storage tank and receives water as a storage liquid.

Since such water reservoirs are conventionally only poorly insulated or not at all, and in particular are not covered on their surface, it is provided in the sense of the present invention to close off the storage tank at the top by a covering device so that heat does not overflow the surface of the storage liquid can escape without further ado. The surface of the storage liquid is therefore covered by the cover device floating on the storage liquid, so that an insulating layer is provided above the storage liquid, which reduces heat loss across the surface.

The preferably at least partially embedded in the ground reservoir is advantageously thermally insulated on its side walls and on its bottom wall by means of a suitable insulating layer and also sealed by a suitable sealing layer against leakage of liquid. The insulation layer may be sealed, for example, by rigid foam sheets (available under the brand name Styrodur) provided on the side walls and the bottom wall. The sealing layer can be formed for example by a suitable liquid-tight film. The insulating layer on the side walls and the bottom wall of the storage tank and the covering layer above the storage tank stored in the storage tank thus an all-round insulation for the liquid contained in the reservoir, preferably water, created so that the storage fluid both to the surrounding the reservoir bottom to the side and is thermally insulated to the bottom and to the ambient air upwards. In addition, the soil of a soil provides a natural insulation barrier, which allows an effective isolation of Speicherbecks at an economically acceptable cost. The cover means may be formed by individual segments in the manner of pontoons floating on the storage liquid. The segments of the covering device can in this case for example by hard foam boards (available under the Brand name Styrodur) be formed, on the one hand on the storage liquid, especially water, swim and on the other hand can provide good thermal insulation. In an advantageous embodiment, the covering device has at least one frame segment and at least one support segment adjustably arranged on the frame segment. The at least one support segment, for example, viewed in a plan view of the surface of the storage liquid, have a circular shape with a rotational symmetry axis directed perpendicular to the surface, wherein the at least one support segment can be pivoted about its rotational symmetry axis relative to the frame segment.

For adjusting the at least one support segment relative to the frame segment, for example, a suitable drive means may be provided with a motor and an adjustment mechanism, wherein the motor is arranged for example outside of the storage tank and an adjusting mechanism in the form of a drive shaft via suitable deflection gear, for example with drive spindles for adjusting one or more support segments is connected to one or more support segments in operative connection and thus can simultaneously adjust a plurality of support segments. At the at least one support segment, for example, a photovoltaic device for photovoltaic power generation can be arranged, which can be aligned by adjusting the support segment relative to the frame segment to the sun. Between the at least one frame segment and the at least one support segment, in an advantageous embodiment, at least one sealing element may be provided for sealing against a passage of moisture. The sealing element may in this case be designed to at least largely prevent moisture leakage out of the reservoir, for example by evaporation, so that moisture can not readily pass out of the reservoir through the segments of the cover. In this case, however, the sealing element can be designed to permit a seepage of, for example, rainwater into the storage tank, so that liquid can pass from the outside through the covering device into the storage tank.

The at least one frame element advantageously connects via an edge segment to a side wall of the storage tank, wherein the edge segment with so the frame segment is operatively connected, that the frame segment and the edge segment can be moved to each other at least by a certain distance along the surface of the storage liquid. For this purpose, the frame segment, for example, partially rest on the edge segment, so that the frame segment and the edge segment are tangent to each other. In this way, when changing the liquid level in the storage tank, the position of the frame segment can be adjusted relative to the edge segment to compensate for a change in size of the surface of the storage liquid in a vertical movement of the surface due to a level change in the storage tank.

An additional inlet for introducing liquid into the storage tank can be provided on the covering device, beyond the transitions formed between the individual segments. Preferably, however, the inlet is formed by the gap-like transitions between the segments, which may additionally be closed by permeable sealing elements for a leak, so that, for example, rainwater can seep into the reservoir from outside between the segments.

On the outside of the cover, preferably on one or more support segments of the cover, in one embodiment, one or more photovoltaic elements in the form of solar cells are provided, which are used for photovoltaic power generation. The energy generated by the photovoltaic elements can be used, for example, to operate the greenhouse system whose component is the heat storage device, and also for operating the heating system and for the drive device for adjusting the support segments, so that the energy supply of the greenhouse system can at least be supported. It is also conceivable to feed electrical energy generated at the photovoltaic elements in a power grid. The storage liquid is preferably water. Water is conveniently available and also has a good heat storage capacity of about 4.18 kJ / kg K. In one cubic meter of water, temperature differences of 4,180 kJ can be stored per Kelvin. As a result of the additional incorporation of storage elements, which preferably have so-called phase change materials (PCM), the storage capacity of the heat storage device can be improved even further Designated latent heat storage, save energy by exploitation a phase transition (for example, from solid to liquid) and give in reversed phase transition (for example, from liquid to solid) energy.

The heating system, with which the storage tank is in fluid communication, may have at least one heat pump and a heat exchanger device connected to the heat pump. Using the heat pump and the associated heat exchanger device, for example in the form of arranged in a greenhouse, fluid-flow spiral finned tubes, the heat storage device can be operated as a mixed storage at relatively low water temperatures (for example in a temperature range between 5 ° C and 45 'Ό), which the on the surface of the storage liquid resulting heat losses additionally reduced.

The idea underlying the invention will be explained in more detail with reference to the figures illustrated embodiments. FIG. 1 shows a schematic sectional view through a heat storage device with a storage tank and a storage liquid located therein; FIG. a plan view of the heat storage device; and

Fig. 3 is a schematic view of the heat storage device in

Interaction with a greenhouse plant.

1 and 2 show an embodiment of a heat storage device 1 comprising a reservoir 2, which is at least partially embedded as an upwardly open basin in a bottom 7, for example, the soil at the location of a greenhouse system, and at least in the region of its upper edge of a ( Earth) Wall 70 is surrounded. In the storage tank 2 is a storage liquid 3, for example water, which serves to store heat on the one hand and on the other hand optionally as a reservoir for an irrigation system of a greenhouse system.

The storage tank 2 has a bottom wall 21 and adjoining the bottom wall 21 side walls 20. On the bottom wall 21 and the side walls 20, the storage tank 2 by means of an insulating layer 22nd thermally insulated from the surrounding soil 7. The insulating layer 22 may, for example, be realized by one or more layers of rigid foam plates, wherein on a side facing inside the storage tank 2 side of the insulating layer 22 is a sealing layer 23 in the form of a liquid-impermeable film or the like, by means of which the storage tank 2 against the Floor 7 is sealed liquid-tight.

The insulating layer 22 may also be formed of a different material, for example a heat-insulating bulk material, e.g. Glass granules.

The storage tank 2 is open at the top. However, in order to avoid heat loss on a surface 30 of the storage liquid 3, a covering device 4 is provided, which floats on the storage liquid 3 and consists of individual segments 40-42, which float in the manner of pontoons on the storage liquid 3 and cooperate in such a way in that the storage tank 2 is thermally insulated towards the top. For example, the segments 40-42 may be made of rigid foam (available under the brand name Styrodur) and completely cover the storage basin 2 at the top. The individual segments 40-42 can in principle also be made of other materials. For example, segments 40-42 may also be used as evacuated hollow bodies, e.g. made of glass or plastic, be realized whose walls enclosing a cavity, for example, can also be transparent, to allow light into the storage tank.

The cover 4 is composed of different segments. On the one hand, the covering device 4 has one or more frame segments 41, into which the support segments 40 are inserted such that the support segments 40 can be adjusted relative to the frame segments 41. The support segments 40 are in this case in the plan view (in a viewing direction perpendicular to the surface 30, corresponding to the drawing plane in Fig. 2) circular and inserted into corresponding recesses of the frame segments 41 such that the support segments 40 about their rotational symmetry axis S along an adjustment V can be rotated relative to the frame segments 41.

The support segments 40 are used to carry photovoltaic elements 5 for photovoltaic power generation on an upper side 43 of the covering device 4 Adjusting the support segments 40 about their rotational symmetry axis S, the photovoltaic elements 5 are aligned with the sun, so that the photovoltaic elements 5 can be tracked during the day of the sun. At some or all edges of the storage tank 2, edge segments 42 are provided, via which the frame segments 41 adjoin the side walls 20 of the storage tank 2. 2, edge segments 42 are provided only on the left and lower side walls 20. Corresponding edge segments 42 may, however, also be used on the right and upper side walls 20 of the storage tank 2.) As can be seen in FIG the frame segments 41 at least in sections on the associated edge segments 42, so that the frame segments 41 can be moved at least by a certain distance along the surface 30 relative to the edge segments 42. This movable connection of the frame segments 41 with the edge segments 42 compensates for a change in the surface area of the surface 30 as a result of a change in level of the storage liquid 3 in the reservoir 2. At a level change, the frame segments 41 can move along the surface 30 relative to the edge segments 42, so that a change in size of the surface 30 compensated and regardless of the level of the storage liquid 3 complete coverage of the surface 30 can be provided by the cover 4.

Between the different segments 40-42 sealing elements 44 are arranged in the form of, for example, foam strips, which seal the transition between the segments 40-42. The seal can be designed such that a moisture leakage from the reservoir 2 is at least reduced, but at the same time a liquid inlet, for example, infiltration of rainwater into the reservoir 2, from outside Shen is possible. At the location of the transition between the segments 40-42 thus Einläute 45 are created for rainwater from the outside, so that liquid can penetrate from the outside into the reservoir tank 2.

For adjusting the support segments 40 relative to the frame segments 41, a drive device 6 is provided. The drive device 6 has a motor 60, which is coupled via an adjustment mechanism 61 with the support segments 40, so that via the adjustment mechanism 61 all support segments 40 can be moved in a uniform manner. The adjusting mechanism 61 is formed by a drive shaft 600 of the motor 60, which via angular gear 610 with drive spindles 61 1 such is coupled, that a rotational movement of the drive shaft 600 is converted via the angular gear 610 in a rotational movement of the drive spindles 61 1.

In the illustrated embodiment, in this case on the drive shaft 600 three angle gear 610 with three adjoining drive spindles 61 1 for driving six support segments 40 of the cover 4 are provided.

In the storage liquid 3 in the storage tank 2 in addition storage elements 31, comprising so-called phase change materials, for example, salt or paraffin-based, arranged. These storage elements 31 serve to increase the heat capacity of the heat storage device 1 and allow based on a phase transition, an additional, efficient storage of heat.

As shown schematically in FIG. 3, the storage tank 2 is in fluid communication with a heating system of a greenhouse 8, which has a heat pump 80 and a heat exchanger device 81 in the form of, for example, installed in the greenhouse 8 piping. By incorporating the storage tank 2 in the heating system using a heat pump 80, the heat storage device 1 can be performed as a mixed storage at relatively low water temperatures, for example at water temperatures between 5 'Ό and 45' Ό. In particular, the comparatively low maximum temperature of for example 45 ° C leads to a reduction of heat losses at the surface 30 of the storage liquid 3, because due to the comparatively low heat difference to the ambient air, there is a comparatively low heat radiation.

For the operation of the heating system, warm water can be conducted from the storage tank 2 to the heat pump 80, which extracts heat from the water and transfers it to the heat exchanger device 81 as useful heat. The heat exchanger device 81 can thereby be used for heating the greenhouse 8, wherein water is passed from the storage tank 2 after passing through the heat pump 80 back into the storage tank 2.

Likewise, for example condensation liquids can be conducted from the greenhouse 8 to the storage tank 2. The storage tank 2 may also be connected to an irrigation system of the greenhouse 8 so that the water stored in the storage tank 2 can also be used for watering plants in the greenhouse 8. The idea underlying the invention is not limited to the above-described embodiments, but can also be realized in completely different types of embodiments.

For example, a storage liquid other than water can in principle also be used. In addition, it is in principle conceivable to design the covering device in a different manner, for example by using films which seal the top of the storage tank liquid-tight, so that from outside liquid does not readily enter the storage tank and also leak from the inside no liquid from the storage tank 2 can.

In another use, the reservoir can be used for example as a fish tank for breeding fish. This results in a multiple use of the storage tank for heat storage, irrigation and fish farming. If the storage tank is also used for fish farming and it is therefore intended that fish will float in the storage liquid (water) contained in the storage tank, the storage tank is preferably provided with a comparatively low maximum temperature of e.g. Operated at 30 ° C. The water in the reservoir is thus kept below a temperature of 30 'Ό to allow the fish farming.

Structurally, only slight modifications to the heat storage device are required to allow use of the reservoir also for fish farming. For example, a closable supply opening can additionally be provided in the covering device, via which, for example, feed can be introduced into the storage basin.

In particular, when using the storage tank for fish farming may also be advantageous if the cover is at least partially transparent designed to allow light into the reservoir and to create a suitable habitat for fish in the reservoir. LIST OF REFERENCE NUMBERS

1 heat storage device

2 reservoirs

20 side wall

21 bottom wall

22 insulation layer

23 sealing layer

3 storage fluid

30 surface

31 storage element

4 Floating cover

40 support segment

41 frame segment

42 edge segment

43 Outside

44 sealing element

45 enema

5 photovoltaic element

6 drive device

60 engine

600 drive shaft

61 adjustment mechanism

610 angular gear

61 1 drive spindle

7 soil

70 Wall

8 greenhouse

80 heat pump

81 heat exchanger device

S rotational symmetry axis

V adjustment direction

Claims

claims

Heat storage device for a greenhouse, with

at least one storage tank,

- A storage liquid which is filled in the reservoir and forms a surface for storing heat and

a heating system of a greenhouse, which is in communication with the storage tank such that storage liquid into the heating system can be introduced, characterized by a cover (4), which is arranged floating on the memory liquid (3) surface (30) and the surface (30) covers.

Heat storage device according to claim 1, characterized in that the storage tank (2) is at least partially embedded in a bottom (7).

Heat storage device according to claim 1 or 2, characterized in that the storage tank (2) has a side wall (20) and a bottom wall (21), wherein the storage tank (2) on the side wall (20) and / or the bottom wall (21) an insulating layer (22) is heat-insulated and / or sealed by a sealing layer (23) against a liquid passage.

Heat storage device according to one of claims 1 to 3, characterized in that the covering device (4) has at least one frame segment (41) and at least one on the frame segment (41) adjustably arranged support segment (40).

5. Heat storage device according to claim 4, characterized in that the at least one support segment (40), viewed in a plan view of the surface (30), a circular shape with a perpendicular to the surface (30) directed rotational symmetry axis (S).

6. Heat storage device according to claim 5, characterized in that the at least one support segment (40) about its rotational symmetry axis (S) is pivotable.

7. Heat storage device according to one of claims 4 to 6, characterized by a drive device (6) having a motor (60) and an adjusting mechanism (61) for adjusting the at least one support segment (40).

8. Heat storage device according to one of claims 4 to 7, characterized in that between the at least one frame segment (41) and the at least one support segment (40) at least one sealing element (44) for sealing a moisture passage between the at least one

Frame segment (41) and the at least one support segment (40) is arranged.

9. Heat storage device according to one of claims 4 to 8, characterized in that the at least one frame segment (41) via at least one along the surface (30) movably connected to the at least one frame segment (41) edge segment (42) to a side wall (20 ) of the storage tank (2) connects.

10. Heat storage device according to one of the preceding claims, characterized in that the covering device (4) has at least one inlet (45) for introducing liquid into the storage tank (2).

1 1. Heat storage device according to one of the preceding claims, characterized by at least one photovoltaic element (5) which is disposed on a side facing away from the storage liquid outside (43) of the cover (4).

12. Heat storage device according to claim 1 1, characterized in that the at least one photovoltaic element (5) on at least one support segment (41) of the cover (4) is arranged.

13. Heat storage device according to one of the preceding claims, characterized by at least one in the storage liquid (3) arranged storage element (31).

14. Heat storage device according to claim 13, characterized in that the storage element (31) comprises a phase change material.

15. Heat storage device according to one of the preceding claims, characterized in that the heating system has at least one heat pump (80) and one with the heat pump (80) connected to the heat exchanger means (81).

16. Greenhouse plant with a heat storage device according to one of the preceding claims.