DE2400460A1 - Heat storage with earth as heat-storing material - also using underlying strata of ground - Google Patents

Abstract

Heat is fed in and extracted by means of a medium which flows through channels fashioned in the earth or deposits and underlying strata. The heat-transmitting medium can be conveyed in channels of any cross section and the channels can have linings, e.g. pipes, of any material or be left bare, i.e. without lining. The channels can be fashioned in the ground in any direction and are traversed by the heat-transmitting medium in one direction or, in the case of double-walled channels, in a reverse flow with reversal of direction. The channels can be laid not only parallel to one another, but also in the form of a fan.

Description

Description of the process for heat storage is the subject of the invention is a process that makes it possible with calls for a new type of heat storage system to store large amounts of heat over a long period of time.

Numerous methods are already known for storing heat, those of the heat absorption capacity of matter in the form of liquids or solids is used for storage. However, the liquids must be in containers gesa @ melted or the solids in the form of stone structures (resuperators) or the like. are arranged, so that only relatively small amounts of matter for storage Therefore, the storage capacity of such memories is relative low and the heat can only be retained for a short time. This is how they are Storage is only suitable for storing high-quality heat, the recovery of which the iiohen costs for the storage justified.

In our determined by the drastic scarcity of fossil fuels But time also has the task of generating low-quality, low-temperature heat, as it occurs mainly as waste heat in power plants (especially nuclear power plants), all year round to be saved in order to be able to use them for heating purposes. Dzu must be extraordinary large amounts of heat can be stored for a very long time.

A storage method proposed in the following now allows Almost any amount of heat over months and possibly even years to save relatively low costs, so that waste heat is also saved in the long term store and then for heating purposes or for certain industrial processes (e.g. for beet distillation).

The principle of the process consists in the heat to be stored to be introduced in a suitable manner into @ the soil or the deeper soil layers, this heat up to the desired temperature and remove the heat again if necessary.

As overviews show, the soil, including the underneath lying soil layers down to practically any depths such a low level of warmth and thermal conductivity, even if no artificial insulation is used only small losses of stored heat occur. On the other hand, these are thermal Properties yet again sufficient to face the long times that for Heating and heat extraction are available, the heat without excessive effort initiate and can be removed again. This offers the ground and the deeper ones Soil layers as ideal storage for the tasks mentioned.

The memory can now be carried out as follows.

In the earth there are channels running roughly parallel to the surface with a very small diameter brought forward (drilled, pressed, etc.), through which a Gas or a liquid is sent through as a heat transfer medium. This medium has a higher temperature than the surrounding soil layers and heats so they open. A gas or a liquid is again used to extract heat, this time but sent through at a lower temperature than that of the soil, i.e. the Warm from the. Absorbs soil and passes it on to consumers.

Depending on the type of medium and the structure of the soil, the channels are with Linings (pipes, rectangular ducts, etc.) provided or left blank.

Thus, when using air as a medium, it should be sufficiently solid Floor structure, there is no need to line the ducts. The closing of individual channels by earth movements, narrowing of the cross-section by falling material and also the heat losses during the subsequent air / water heat exchange for remote transmission should in many cases outweigh the cost of a liner. On the other hand, can in the case of poorly water-soluble soil, water can also be routed through bare channels.

Ausapulungen are, as long as they are not too coarse, even favorable, because they increase the heat transferring area of the duct and thus that of the storage Increase in entropy (loss of temperature) in the stored heat help to reduce Excessive washings can be prevented by suitable methods (e.g. inclusion of the Outside of pipes, which are then pulled again) undone will.

The distance between the channels, which also increases the entropy decisively influenced, different choices can be made to achieve the most favorable storage ratios to reach. In this way, the same storage tank can be used for most of the heating season Required heat of medium temperature with wide channel spacings, which for the #### A few very cold days, on the other hand, require high-temperature heat with small channel spacings can be saved in order to save them quickly and with particularly low temperature losses can be found. (The storage of heat at different temperatures in the same storage tank does not present any difficulties because of the low heat conduction of the Eoden.) Storage tanks with very small channel spacings are also suitable for use during sewing Waste heat generated during off-peak periods for the requirements of the following day to save.

The channels themselves will usually have a circular cross-section, but can also be executed with other forms. So it can be cheaper In the upper layers of the earth, long rectangular channels of great depth to be excavated, which are suitable Way to be supported against ground pressure. With them you get great heat transferring Areas between storage tank and medium, with which the temperature differences between Keep the heat input and output low. If you store heat in them low temperature, Bo one has besides the advantage of the small temperature difference also that of the low storage temperature in the layers close to the surface, which means sioh the soil can be used right up to the surface.

If the storage facility is laid out on level ground, vertical ones must first be used Shafts are dug from which the canals advance and later have medium loaded. These shafts can be used as longitudinal shafts on one storage side be applied to the medium-carrying channels parallel to each other to the other storage side to be able to lead. However, individual perforated shafts can also be excavated from from which the channels are led in a fan shape to the other safety side. lort they can also open into individually drilled holes, from which then the medium is filled.

A fundamentally different memory design is obtained when one the medial channels are not along the surface of the earth, but perpendicular to it you bring down in the ground. The heat-transferring medium then flows first down through an inner tube, is diverted to the ground and passes through eiXn concentrically lying outer tube up again.

The outer tube can be under the aspects already mentioned above disappear and the outer flow channel is bounded directly by the soil itself will. The supply and discharge of the medium to the boreholes can be carried out through the Collecting channels lying on the surface of the earth take place.

Which type of memory design is cheaper is determined by the respective depend on local conditions.

The temperature of the heat brought into such storage is limited only by the conditions of the soil. You collte: r avoiding interference in the groundwater content do not exceed the local evaporation temperature. There this depends on the local soil pressure, which increases with the depth, can The lower the respective storage areas in the Lying on the ground. Basically, storage is also possible at great depths very high temperatures possible.

This option becomes practical because of the high drilling costs however, if necessary, make use of it in local mines.

With the possibility of using this process to generate large amounts of heat in the long term and to be able to store it cheaply, it is to be regarded as extremely environmentally friendly. Since almost all the facilities required for storage are underground, will the landscape and the rest of the buildings have only changed insignificantly. but The biological use of the soil is also not impaired, because the thermal conductivity of the soil is so small that in the areas pervaded by the plant roots it is close to the surface Layers of the earth only a very slight warming of the soil occurs. This corresponds to the usual warming during the summer months and should thus the Vachstut of plants and promote rather than adversely affect soil microbes. So can such Create storage in any used terrain (also in forests), manage its use or compromise value.

Another advantage of the process is ultimately the Independence from the shape of the terrain. In principle, the memory can not only i * er level, but also in brackets and mountains, if only the hard one the rock does not cause excessive drilling costs.

However, artificial embankments such as waste heaps, Piles of rubbish and the like, because the @ediumfuhrenden channels are in their soft subsoil can be invested very cheaply.

The accommodation of the memory in a hill or mountain also has Another advantage is that the canals are @eboart directly from the outside ## into the slope can. without having to dig cross cuts first.

Claims (5)

Patent claims 1. A method for storing heat, characterized in that bs heat-storing material the soil left in its given state (Likewise, earth-like artificial embankments such as spoil heaps, piles of rubbish and the like) is used together with the underlying layers of soil. The heat will registered or taken with a medium that flows through channels that enter the Soil or the embankments and the layers of soil underneath are introduced are. 2. Heat storage for the Verfanren according to claim 1, characterized in that that the heat-transferring medium is guided in channels of any cross-section and that the ducts are provided with linings (e.g. Ronren) made of any material or left blank, i.e. without a lining. 3. Heat storage for the method according to claim 1, characterized in that that the channels can be used in any direction in the modes and that they of the heat transfer medium in one direction or - in double-walled Channels - are flowed through in a reverse flow with a reversal of direction. 4. Heat storage for the method according to claim 1, characterized in that that heat of different temperatures can be stored therein and that to achieve the most favorable conditions for the heat transfer the channels with different Intervals can be created. 5. Heat storage for the method according to claim 1, characterized in that that the channels are not only laid out parallel to one another starting from longitudinal shafts, but can also proceed from individual perforated shafts in a fan shape.