SE408087B - SEE THAT IN A GROUND BODY STORES THERMAL ENERGY - Google Patents

Description

.. ma: a.- 7? 1: 0'71 + 8 ~ 0 When using wind energy for local heating, there is one similar heat storage requirements. In many process industries obtained large amounts of heat at relatively low temperatures, which could be used for, for example, local heating. The lack of an economic economic possibility of being able to store this heat until a heat demand exists causes large amounts of energy to be wasted.

At, for example, combined heat and power plants where large variations in the need for electricity makes it impossible to rationally utilize heat production a heat storage option would be desirable.

In Incineration of waste in combination with a cheap heat storage method would entail the utilization of an energy resource, which today does not used.

A cheap and easy energy storage method that can be used on a small scale also encourages the individual to a rational utilization of waste materials, which would not otherwise be generated use.

Today, a number of methods are used to store heat. Various materials are used for heat storage. One method utilizes the materials specific heat by heating them. Other methods are used a heat of fusion or heat of vaporization of a material by the heat added at the melting or boiling point. Another method uses the energy exchange in crystal conversion in some material. Some methods are used today in ready-made systems, others methods are in a development stage.

Which method is used depends on the desired operating temperature range, compactness, acceptable heat leakage, removable power per weight / volume, construction costs, etc.

Common to the methods presented above is that none is intended or suitable for storage methods up to parts of years; The storage time for the best methods is a maximum of a few weeks.

In one application example, water is used as the storage medium when the energy is obtained from a solar collector. The stored heat energy shall be used for heating a residential property. If irradiated solar heat obtained during a day should be used for 24 hours consumption, and the temperature range is allowed to be 60-95 ° C, one is required well-insulated water tank of 2-3 m3. Heating under a sunless day must then be done with additional heat in some form. Do you want to reduce that inconvenience one can install a larger solar collector and a larger one heat storage unit. However, the cost of such an ambition is included today's energy price unjustifiable. 7710748-0 A more interesting heat storage method has also been proposed in recent times and consists in arranging a ground body, which stands in direct thermal connection with the surrounding soil, as indicated in the ningsvis. The channels arranged in the ground body can according to one proposals consist of boreholes in the ground, in each of which a pipe loop with a flowing fluid is immersed. According to another proposal the canals consist of shafts blasted in rock according to a certain pattern _and connected by drill holes. In both cases, high temperatures are assumed. temperatures of the fluid flowing in the channels (normal radiator temperature is at least 50 ° C) and a complicated control system to : control the input and output of the thermal energy. Because of those at high temperatures, the losses to surrounding soil and at fl the fluid cycle is very large, because for example surrounding soil has a significantly lower temperature (in Stockholm 800). About solar panels used, these have poor efficiency at high temperatures.

These disadvantages are in practice so considerable that the method does not have could be applied under realistic and economically justifiable attitudes.

What you want is a heat storage device like without excessive costs can be incurred: with a sufficiently high storage capacity, with losses that can be financially compensated, for example with solar collector surface, and with simple technology and simple materials.

This has been achieved according to the invention in that the channels arranged in such a number and with such a dimensioning and distribution depending on the estimated supply and withdrawal of thermal energy for a preferably long period of time, for example one year, to a ground body surrounding boundary surface at a distance a sz _ Q, where a = -E-, where ay is the frequency of the temperature variation 'Y P (periodic) I cp = specific heat for the ground body JL = the thermal conductivity of the ground body and of the density of the field body, from points on the outermost channels in all directions outwards from the ground body, obtains a maximum temperature of '(71 07% -0 u of the order of 35 ° C and one of the supply and removal of energy-conditioned variation during the time period not exceeding 10 ° C. The invention is based entirely on it in comparison with the previous ones proposed above related methods fundamental difference consisting of such a low temperature of the surrounding soil body the confinement surface of which about 3S ° C was used. IN When using solar panels, it is advantageous if from the solar collector output fluid has a temperature, which is limited to not more than ß5 ° C, preferably 35 ° C, whereby the solar collectors can be made extremely simple to construct and still have a very high even higher than the most sophisticated, focused solar catchers operating at temperatures up to 100 ° C, in the fluid.

Especially in combination with low temperature of the heat dissipating the devices obtain a high overall efficiency.

The method according to the invention thus achieves, inter alia, the following benefits: a) The capacity can be made as large as required without high costs nader, (b) the losses due to heat leakage are so small that they can be compensated financially, for example with increased solar collector surface, c) current technology is applicable and not complicated components required, I 7 7 d) simple solar collectors can be used with good efficiency, e) no major thermal stresses or fatigue phenomena occurs in the ground body, and f) the maximum overtemperature of the ground body is so low that ecological adverse effects do not occur.

Of course, the heat dissipation system must be dimensioned as follows, that required amounts of heat can be transferred from the fluid to the room at a temperature of the fluid which does not differ from of the room with more than 10 ° C. in The ground layer consists primarily of an inner zone Zl (see fig. 3a and Sh), which are provided with channels or conduits for supply of heat. The boundary surface Y1 for this zone consists of “of the surface enclosing the active conduits in the ground. _ When calculating the storage capacity of the soil layer, it can be above defined zone is assumed to be fully included in the pipelines temperature variations, provided that each volume element in the body _ is at the maximum distance sl from any of the conduit paths. 'where a = 7710748-6 From Jacob, Heat Transfer, Sixth printing, March 1958, page 303, available to and Q) = the frequency of the temperature variation (period Ä.

I '° P disk), where Ä_ = the thermal conductivity of the ground body I = soil body density and specific heat from the ground body.

° P The distance between two adjacent conduits should therefore be less than 2 sl. .In case of periodic variation of the temperature in z nens limitation area, heat will migrate out or be taken back from surrounding land. The heat thus supplied cyclically respectively taken back from the surrounding land can write ~ r according to _ Jacob: Heat Transfer, page 293, Q = Yl.20a.¿e. -åï where 29a is the temperature variation (see Fig. 30) .ß. cp lll This amount of heat Q can be stored in an outer zone Z2 in the ground storage, which fully participates in (follows) the surface Ylzs temperature variation 2 a.

The volume of this outer zone Z2 can be written Y1. s2, where sz can interpreted as the "equivalent penetration depth" in the ground outside zon Zl. The volume of the land stock can thus be regarded as the sum of zones Z1 and Z2 and with a boundary surface Y2, which lies on distance sz from the surface Yl. 1 Alitsågälier Q = Y.26a. ,, (.- Ví = s2.srl.29a.f.cp whereby sz = \ / å is obtained.

It is thus found that sl = sz.

In order to achieve optimal utilization of in heat storage The working mass of the soil is suitably distributed in the channels so that each mass element participating in the process has a maximum distance in to a canal of about 1 meter for very water-rich ground to approx 3 meters for very water-poor soil or bedrock, such as granite. 7710748-0 For optimization of the possibility of it in the heat storage process working soil mass to assimilate maximum available effect, the total available mantle surface of the channels can be given a suitable size by adjusting the effective cable length and cable diameter. _ The required channels can be provided particularly easily, if the method according to the invention has those specified in claims 5 or 6 the characteristics.

The invention and the advantages achieved thereby will be discussed in more detail below with reference to the attached on which figure 1 shows an embodiment of a simple line path accomplished by means of a borehole, Figure 2 shows an example of a participant in heat storage ground body under a villa, island ' figure 3a and 3b shows a ground body in two projections, and Figure 3c shows the range of temperature variations in one cut through the ground body.

Figure 1 shows a channel or hinge arranged in a ground body 1. created by drilling in addition to a thermal insulation clay conduit with 3 * m length a for example 10 meter deep hole 2 with a diameter of, for example, 2.5 cm, which borehole is lined with a "sock" 3 of, for example, aluminum foil, in which a concentrated trical supply pipe N is located. The feed 3, as by e.g. an overpressure shock has been pressed into abutment against the borehole 2 walls, are sealingly connected to a connecting pipe 5, which like with the pipe 4 is connected to a pipeline 5, over which the pipes 3,4 together with a device 7 for supplying heat, for example a solar collector, and a device 8 for emitting heat, for example radiators, form a closed circuit for a flowing fluid, for example water. in In order for the temperature on the ground surface not to be significantly affected the upper part of the pipe is insulated approximately the distance S2.

The boreholes 2 are arranged at intervals of the order of magnitude not more than 2.s, the value of which depends on the type of land and is given below: v 77107lr8'0 Ground type Distance 2 sl (cyke1 = 1 year) 2 32 Granite 6, H m Sand U, 6 m Morän _ 5, U m Lera '' 3.5 m Gyttja 2.0 m Water 1.8 m Figure 2 shows a normal villa 10 with length x width measurements x 8 m built on bedrock and with an annual energy requirement of 26,000 kWh, on which a substantially horizontal solar collector ll of H0 m2 is thought to be built into the roof. From this you can calculate that for 100% coverage of the annual need for solar energy, one is required ground body 12 according to the invention with a volume of 2300 m3. Such a is easily achieved by means of two rows of boreholes with a depth of 10 m and a space of about 6 m (2sl = 6 m). The boreholes need self- the case should not be vertical but may be tilted if required.

The ground body extends (granite) about 3 m out from the two rows with boreholes both outwards on the sides and downwards (and upwards about the boreholes upper parts would be insulated) and cover a volume> 2300 m3.

Figure 3a shows a vertical section through a ground body 12 formed by four rows of vertical channels or conduits 2.

A boundary surface Y1 encloses the channels 2 and passes through the outermost ones located the channels and their end faces. The distances between the channels and the one enclosed by the boundary surface Y1 is at most the distance sl the zone is designated Zl. extends a zone Z2, which has the extent Around zones Zl These zones and surfaces are shown sz out to a boundary surface Y2. from in Figure 3b.

Figure 3c shows the temperature distribution within the soil body extent 12 'in a horizontal plane and the temperature swing with size 2Ûa when input and output of heat energy to resp. from the soil layer. The position of the constraints shown in Figs. surfaces Y1 and Y2 are marked in Figure 3c as well as temperature distribution outside the outer boundary surface Y2. ¿V? 1ov4s-o For raising the temperature of the soil body according to the invention for example to 25 ° C and 30 ° C is required during an initial stage one relatively large amount of energy, which can be obtained from, for example, folding solar panels, set up at the construction site. Also other temporary heat sources are conceivable. The cost of this initial training of the soil body can be considered as an investment.

In a similar way as in the normal villa, an apartment building can equipped with, for example, solar panels and a ground body, which is allowed to work against a heating system of low temperature type in the house. That on this ways to 100% cover the heating needs even in multi-family houses can of course provide large financial gains.

In many cases and especially in countries with a ground temperature of upwards of 20 ° C it may be appropriate to according to the same principle alternatively or in addition arrange a cooler ground body with a temperature of approx -l5 ° C for keeping cool in a room that has been exposed to for a long time unwanted supply of heat.

The soil storage method according to the invention can of course also used for tempering swimming pools.

The invention is generally applicable to varying supplies of thermal energy from solar panels, wind generator (via mechanical water brake or electric heating), waste heat and varying or constant extraction of thermal energy but also with constant supply of thermal energy and varying outlets, which may momentarily be greater than that added energy.

The dimensioning of the ground body and the distribution of the channels can in some cases require complicated calculations, as a matter of course , is greatly facilitated if computer processing is resorted to.

The invention is of course not limited to those shown here embodiments without numerous modifications are possible within within the scope of the invention defined in the claims.

Claims (6)

.vyf fi - 9 7710748-0 P A T E N T K R A V A method of storing thermal energy in a soil body which is in direct thermal communication with the surrounding soil, which from heat-absorbing devices, such as solar collectors, is supplied to the soil body via a plurality of channels arranged in the soil body by circulating a fluid in a circuit containing the channels and the heat-absorbing devices, and extracting stored thermal energy from the ground body by means of the fluid for tempering an object, such as a building, by circulating the fluid in a circuit containing the channels and heat-emitting devices, due to the fact that the channels are arranged in such a number - and with such a dimensioning and distribution depending on the calculated supply and extraction of thermal energy for a preferably long period of time, for example one year, that a ground body surrounding boundary surface at the distance 7 \ 3.cp wherein LJ is the frequency of the temperature variation (periodic) where a = cp specific heat for the ground body '7L thermal conductivity the density of the soil body _3 = the density of the soil body, from points on the outermost channels calculated in all directions outwards from the soil body, obtains a maximum temperature of the order of 35 ° C and a variation of energy supply and withdrawal during the time period not exceeding 10 ° C. 2. A method according to claim 1 for tempering a building, characterized in that the fluid is supplied to the heat-emitting devices at a temperature which does not differ from the intended room temperature of the building by more than 10 ° C, preferably 5 ° C. 3. A method according to claim 1 or 2, wherein solar collectors are used as heat-absorbing devices, characterized in that the fluid emanating from the solar collectors has a temperature which is limited to a maximum of HSOC, preferably 3590. "Ära _ 7710748-0 1 ° 4. A method according to any one of claims 1-3, characterized in that in order to achieve optimal utilization of the storage process, the channels are distributed so that each mass element participating in the process has a maximum distance to a channel equal to the distance s. 5. A method according to any one of claims 1-4, characterized in that the channels in the ground body are provided by drilling a number of holes from the ground surface and inserting a liner, preferably of metal with the required compressive strength in each borehole, in which a concentrically, open pipes are arranged at the bottom of the borehole, and the pipes and liners are connected with pipelines to form at least one closed circuit containing the heat-emitting and heat-absorbing devices. A method according to any one of claims 1-M, wherein the soil has a soft nature, characterized in that the channels in the soil body are produced by pressing into the soil body a number of tubes closed at the end of the depression and arranging in each tube a concentric, at the closed end of the tube open inner tube, together with the outer and inner tubes are connected with pipelines to form at least one closed circuit containing the heat emitting and heat absorbing devices. MENTION PUBLICATIONS: