JPH0417353B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for storing and utilizing thermal energy, and in particular a method for storing thermal energy at a not-too-high temperature in water underground at a plurality of temperature levels at the same time. The aim is to provide a method for storing energy on a large scale and over a long period of time, and extracting and utilizing the energy in a timely manner.

One of the purposes of storing thermal energy underground is to store cold heat in the winter until the summer, or warm heat in the summer until the winter, on a large scale, and then take it out in the summer and winter and use it for cooling and heating, respectively. I'm trying.

There is considerable interest in the effective use of solar thermal energy, wind energy, or thermal energy derived from various types of agricultural, forestry, and livestock waste, which are generally referred to as local energy, but a serious drawback common to these is that the supply of the energy is discontinuous. In addition, there is a large discrepancy between the demand period and the supply period of the energy, making it impossible to respond appropriately to the desired demand. In order to eliminate these disadvantages, economic efficiency etc. There is a strong desire to establish a satisfactory long-term energy storage and utilization method.

BACKGROUND ART Conventionally, methods of utilizing underground aquifers have been attempted as a method for storing thermal energy in the summer and cold energy in the winter for a long period of time.

In other words, heat is stored by using an underground aquifer with a small flow of groundwater.One specific example is pumping up water from the aquifer in the summer and raising it using high-temperature outside air or active solar heat. The heated water is then injected into another aquifer to store thermal energy.

As is well known, aquifers exist in soil with low thermal conductivity, and are like heat storage tanks surrounded by excellent natural insulation, allowing for efficient heat storage with very little heat loss. be.

The hot water can then be pumped up in a timely manner, for example in winter, to melt snow from roofs and roads in snowy areas, and sometimes heated by a heat pump or the like and used for hot water supply or space heating. It is being done. On the other hand, it is also possible to return the cold water heat-exchanged by the snow melting to another aquifer tank and store it in preparation for use in summer cooling.

However, the existence of the above-mentioned aquifers suitable for storing such thermal energy is usually extremely limited regionally, and furthermore, the presence of such aquifers suitable for storing such thermal energy is not limited to anywhere near the above-mentioned hot energy or cold energy demand areas. The reality is that it is extremely difficult to ask for it.

The inventors have completed the present invention as a result of intensive studies with a view to resolving the above-mentioned location constraints, especially regarding the storage and utilization of thermal energy underground.

That is, the present invention provides a method for damming up an impermeable wall by directly contacting an impervious layer with the lower end of an impermeable wall installed in a substantially vertical direction in a suitable underground location where groundwater flows. an underground water storage part that overflows from the upper part formed by the above-mentioned structure, or a gap that allows water to flow without directly contacting the impermeable layer at the lower end of an impermeable wall installed substantially vertically. An underground water storage part is formed by being dammed with an impermeable wall, and water with a temperature higher than that of groundwater is stored in the upper layer, and water with a lower temperature is stored in the lower layer. In order to form temperature stratification, water guide pipes are installed vertically deeper and shallower than above ground to reach the low temperature lower water part and the high temperature upper water part of the water storage part, respectively, so as to reach the respective water layers. and a water pumping and water injection device forming a closed circulation path so that water can be pumped and injected through the pipe to store and extract thermal energy. storage and utilization methods.

Although underground water is dammed up by impermeable walls,
Depending on the purpose, if only hot water is used, use hot or cold water between the lower part of the impermeable wall and the bedrock, or above the aquifer and above the impermeable wall if only cold water is used. In this case, it is preferable to maintain a flow path for groundwater in the middle part of the impermeable wall.

The present invention will be described in detail below with reference to the drawings. Figure 1 shows the underground water storage section (hereinafter referred to as
This is a schematic cross-sectional view of a subterranean dam (also called an underground dam).
is the ground surface, 1' is the urban building etc. built on this ground surface, 2 is the underground bedrock, 3 is the above-mentioned underground aquifer, 4
is a groundwater flow.

And 5 is the bedrock (impermeable layer) in the example of Figure 1 B.
It is a water-shielding wall built in contact with the underground aquifer 2, and is located downstream of the urban area 1' with respect to the underground water flow 4, and is provided at a height approximately equal to the thickness of the underground aquifer 3. The above-mentioned underground water flow 4 is blocked by this impermeable wall 5, and an underground dam 6 is formed in the lower part of the city area 1' as shown in the figure. Water at a relatively low temperature is stored in the lower layer 6a, and water at a higher temperature is stored in the upper layer 6b, forming so-called temperature stratification.

In the example shown in FIG. 1C, the impermeable wall 5 is provided without its base touching the bedrock 2, and therefore, in this case, the groundwater always flows away from the bottom of the underground dam.

The technology for constructing such underground dams is almost established today, and specifically, a large number of injection boreholes are drilled perpendicularly or diagonally from the ground surface at the location where the underground dam is installed, and the holes are drilled through the boreholes. A cement bentonite liquid or the like is injected from the bottom to lower the permeability coefficient of the rock, and a water-shielding wall 5 is constructed by injecting a low-viscosity water glass liquid or the like. By installing the above-mentioned water-shielding wall 5,
In either case, the groundwater overflows when the water is full or flows underground under the impermeable wall, so the groundwater flow does not change significantly and there is a concern that ground subsidence may occur due to changes in the groundwater level downstream of the subsurface dam. almost never occurs.

Since the water storage section is generally formed of a gravel layer, convection due to temperature differences in the stored water is difficult to occur, and the above-mentioned temperature stratification is easily formed. It becomes eminently suitable.

Next, from the ground surface, as shown in the figure, the above-mentioned upper layer of the underground dam,
and install a well (pipe) 10 that reaches the lower layer,
Furthermore, these wells (pipes) 10 are connected to a water pumping and water injection device 11. In this case, the example shown in Figure 1B is suitable for storing low-temperature water because the upper layer flows out due to overflow of groundwater, while the example in Figure 1C is suitable for storing high-temperature water because groundwater constantly flows out at the bottom. . However, in both cases, it is necessary to take in and out the stored water separately through wells (pipes) that reach each layer directly, and it is necessary to avoid mistaken inflow and outflow of groundwater that may disturb the mutual stratification. Must be.

All of these water pumping and water injection devices 11 are provided with conventional means to operate in a closed circulation system.

Next, an example of a method of storing and utilizing thermal energy in the underground dam constructed as described above will be described in the case where it is used for snow melting in the winter in snowy areas and for cooling in the summer.

In Figure 2, 1'a is a building on the ground, 10a,
10b is a well (pipe) installed to reach the lower and upper layers of the underground dam 6, and 12 is a snow melting pipe placed on the roof of the building 1'a.

When it snows this winter, a pump (not shown) pumps up relatively high temperature water from the upper layer of the underground dam 6 through the well (pipe) 10b, passes it through the snow melting pipe 12 with fins, melts the snow on the roof, and exchanges heat here. The cooled water is fed to a well (pipe) 10.
It is returned to the lower layer of the underground dam 6 via a not shown injection pump.

Next, in the summer, on the contrary, the cold water from the lower layer is pumped up through the well (pipe) 10a, heat is exchanged with the coil 13a of the air conditioner 13 installed indoors, and the room is cooled, and the hot water is pumped up. It returns to the upper layer of the underground dam 6 via a well (pipe) 10b.

Cold water returned to the lower layer of the winter underground dam 6 mentioned above,
In addition, the hot water returned to the upper layer in the summer is not likely to cause convection and is in a natural insulating atmosphere, so the thermal energy is appropriately stored for a long period of time, and is sufficient for snow melting and cooling. It will be possible to comply.

Such equipment may be partially omitted from the wells (pipes), piping, and various equipment, etc., so that it is suitable for use only in the winter or summer season, depending on the purpose of use, especially regional considerations. It is necessary to provide separate heat exchange equipment for the water returning to the dam 6.

In addition, such rapid pumping of groundwater may lead to unexpected defects such as ground subsidence, and it is desirable to determine the amount of pumping or reinjection in advance to anticipate these problems.

In order to reduce the heat loss during pumping and injection, it is a good idea to install the above equipment as close as possible to the energy usage site, and by making the circulation system a closed system, it can be adapted to various purposes. Not only this, but also the clogging of the extraction or injection well (pipe), changes in water quality, etc. can be prevented, and therefore water can be recharged directly, which is particularly preferable.

When the thermal energy storage and utilization method shown in Figure 2 above is actually operated, the upper layer water will be pumped up and injected into the lower layer in the winter, and the reverse will occur in the summer, and the boundary between them, that is, the temperature stratification described above, will be maintained for a long time. Although the overall water composition fluctuates greatly, the overall water volume remains balanced.

What is particularly preferable is to introduce such a system all at once for the entire region and increase the capacity of the above-mentioned subsurface dams, but in this case, intensive water intake,
By performing reduction, it is also possible to install centralized equipment, and for one large-scale underground dam,
By distributing water intake and water injection to each area, it is also possible to use the stored energy in a distributed manner within each area.

In the above example of storage and usage methods, the single purpose is snow melting in the winter and cooling in the summer, and it is assumed that a certain balance can be achieved in the heat balance, but in general, snow melting energy in snowy areas is used. Usually, it occupies a large proportion.

From the perspective of such energy balance, it is necessary to comprehensively judge energy usage in the entire region and install equipment. An example of supplementing the energy balance for this purpose is shown in FIG.

In the figure, 22 is a cold warehouse for storing agricultural products such as rice, 23 is cultivation work for the purpose of relatively low-temperature cultivation of enoki mushrooms, etc., and 24 is a garbage incinerator, all of which are connected to the lower level of underground dam 6. It is capable of taking cold water and exchanging heat, and returning hot water to the upper layer, and by incorporating these into the above-mentioned equipment, it is possible to balance the energy balance of the above-mentioned thermal energy storage and utilization.

In the figure, 24' is an incineration work chimney, 25 is each heat exchanger, 26 is a central water intake pipe, and 27 is each water injection pipe.

Next, in municipal waste incineration plants, steam is sometimes generated from the heat generated by waste incineration and used for turbine power generation, and the above-mentioned cold water can be used as condenser cooling water for the steam turbine. An example is shown in FIG.

In the figure, 28 is an incineration boiler, 29 is a steam turbine, 30 is a generator, and 31 is a condenser. Specifically, the lower layer water of the dam 6 can be used for cooling the condenser 31, and the hot water can be returned to the upper layer.

If we adopt the example shown in Figure 1C in which the steam impermeable wall 5 does not come into direct contact with the impervious bedrock 2, the water in the lower layer of the underground dam 6 will constantly flow away and the water in the upper layer will be stored relatively quietly. Therefore, it is particularly suitable for long-term storage of relatively high-temperature water.

Applying this to the example equipment shown in Figure 2 above, cold water is circulated through a finned circulation pipe on the roof for snow melting in the winter, and hot water is created using solar heat in the summer, when heat energy is abundant, and this water is used until the winter. You can create storage facilities.

Particularly in areas where there is a large amount of snow melting, it is very effective to increase the amount of hot water stored and prepare for snow melting not only on roofs but also on roads.

As described in detail above, the present invention actively forms a subterranean dam by installing an impermeable wall in a suitable location underground, and utilizes the high thermal insulation properties inherent in the underground to simultaneously efficiently generate cold and thermal energy. Since this method is a method for storing and using the stored waste in a timely manner, it has an excellent effect in that the above-mentioned location constraints are significantly improved.

In addition to the original effects of the present invention, () Serious problems such as ground subsidence caused by pumping up groundwater for snow melting, etc. are significantly reduced, () Fuel for producing hot water for snow melting, etc. It is extremely economical compared to other types of underground dams, () Even in urban areas where it would be difficult to find a water source in adjacent areas, the use of the above-mentioned underground dam makes it possible. erect a wall,
It is also possible to form a completely artificial underground water reservoir by injecting and storing cold water or hot water. () The structure is extremely simple and economical. () There are significantly fewer restrictions on the installation location. , () It is easy to cope with the planned amount of heat storage, etc., and the scope of its use is very wide, not only for snow melting and heating, etc., and after all, local energy is a discontinuous energy source. The industrial effects that can contribute to the local economy, in particular, are truly significant.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an underground dam for explaining the method of the present invention, where A is a vertical cross-sectional view, B is a cross-sectional view, and C is a cross-sectional view.
is a cross-sectional view of another embodiment, FIG. 2 is a schematic diagram of an example in which the same method is used for snow melting and heating, FIG. 3 is a schematic diagram of an example in which the same method is further expanded to other fields of application, and FIG. The figure is a schematic diagram showing an example of using the heat generated during garbage incineration to return thermal energy to turbine power generation cooling water. 1...Ground surface, 1'...Urban building, 2...Underground bedrock (impermeable layer), 3...Underground aquifer, 4...Groundwater flow, 5...Waterproof wall, 6...Underground dam ( water storage part), 6a, 6b...upper layer, lower layer (temperature stratification), 1
0a, 10b...well (pipe), 11...pumped water,
Water injection device, 12... pipe with fins for snow melting, 13
...Air conditioner, 25...Heat exchanger, 26,27...
Central piping, 29...steam turbine, 30...generator, 31...condenser.

Claims (1)

[Scope of Claims] 1. A dam constructed by installing an impermeable wall in a suitable underground location where groundwater flows, with the lower end of the impermeable wall installed in a substantially vertical direction in direct contact with an impermeable layer. An underground water storage area that overflows from the upper part that is raised, or a gap that allows water to flow without directly contacting the impermeable layer is provided at the bottom end of an impermeable wall installed substantially vertically. An underground water storage area is formed by being dammed with an impermeable wall, and water with a temperature higher than that of the groundwater is stored in the upper layer, and water with a lower temperature is stored in the lower layer. In order to form temperature stratification, the lower water part of the water storage section has a lower temperature, and the upper water part of a higher temperature water part has a vertically deeper part than the ground part, so as to reach the respective water layers.
In addition to installing a water guide pipe in a shallow area, a pumping and water injection device was installed that formed a closed circulation path so that water could be pumped and injected through the pipe, and thermal energy was stored and extracted. Features methods for storing and utilizing thermal energy. 2. A method for storing and utilizing low-temperature thermal energy, characterized in that the underground water storage section according to item 1 above is of a type that overflows from the upper part, and stores water at a lower temperature than normal ground water in the lower layer of the storage section. 3. The underground water storage section in paragraph 1 above is a type of water storage section formed by an impermeable wall with a gap in which the lower end of the impermeable wall allows water to flow without being in direct contact with the impermeable layer, and the water storage section A method for storing and utilizing high-temperature thermal energy, which is characterized by storing water at a higher temperature than normal groundwater in the upper layer of the ground.