JPH04350464A - Utilization of geothermal energy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a method of utilizing underground thermal energy, which utilizes thermal energy stored in underground non-aquifers for melting snow on roofs, clearing snow from roads, and the like.

0002

[Background Art and Problems to be Solved by the Invention] Underground strata can be classified into the following two types depending on the presence or absence of groundwater.

・Saturated zone below the groundwater table: aquifer ・Unsaturated zone above the groundwater table: non-aquifer Groundwater in this aquifer is directly pumped up to melt snow on roofs and snow on roads, etc. Although the use of groundwater has been regularly used and has achieved excellent results, there is no need to provide any literature, on the other hand, as the amount of groundwater used increases, the phenomenon of lowering of groundwater level and ground subsidence is occurring. This problem has arisen and its resolution has become a major problem.

[0004] As a countermeasure to this problem, Japanese Patent Application Laid-Open No. 53-14304
Although a heat exchange device using geothermal heat is disclosed in Publication No. 4,
This idea involves a method of forcibly circulating air and water in a hole bored in the ground to extract heat energy stored in the ground, and collecting heat from the surrounding soil. . This heat collecting device has a cylindrical hole inside.
The hole is filled with an air permeable medium such as gravel, and has a structure in which two pipes with openings are arranged above and below the hole.

[0005]Also, the idea of collecting heat from the surrounding soil using holes drilled in the ground is also adopted in the snow melting method of Utility Application No. 1982-28995, but the above-mentioned geothermal heat exchange device is also used. It is still a method that collects heat from the soil around the hole.

[0006] Furthermore, in a similar soil-type heat exchanger for heating and cooling using natural energy, disclosed in Japanese Patent Application Laid-Open No. 54-16763, the thermal characteristics of soil are positioned as follows.

[0007] Soil has a large heat capacity and can be used as an inexpensive heat storage material.

[0008] Soil has low thermal conductivity and high heat retention, so it is suitable for long-term heat storage, but on the other hand, it is difficult to collect heat when extracting it.

[0009] This thermal non-conductivity of the soil reduces the heat collection efficiency even in the heat collection devices using underground vertical holes as disclosed in the above-mentioned Utility Application No. 60-28995 and Japanese Unexamined Patent Publication No. 53-143044. , the problem of having to dig a large number of holes to extract a large amount of heat cannot be avoided.

[0010] In this regard, this prior application proposes the following measures to increase the underground heat collection efficiency. ■The ground is completely excavated and heat exchange pipes are buried in the soil in multiple layers to ensure a wide contact area with the soil.

[0011] In order to increase the speed of heat transfer in the soil, water is allowed to permeate and flow down from the underground pipes above, and the water warmed by the soil particles moves downward and collects heat from the underground pipes below.

[0012] Although this measure certainly increases the heat collection efficiency of the buried pipe, it requires extensive excavation to bury the pipe, which poses problems in terms of economy and workability.

The present invention proposes a method of utilizing underground thermal energy that solves these problems.

[0014]

SUMMARY OF THE INVENTION The gist of the present invention will be explained with reference to the accompanying drawings.

[0015] The natural thermal energy stored in the non-aquifer b above the underground aquifer a is transferred to the ground using air that is forced to flow inside the non-aquifer b by pressurization or depressurization as a medium. This relates to a method of utilizing underground thermal energy, which is characterized by extracting the air and using the air as a heat source.

[0016]

[Function] In aquifer a, the gaps between soil particles (usually 10 to 30% in a gravel layer) are filled with groundwater, but in non-aquifer b, the gaps between soil particles are filled with air. .

[0017] Normally, temperature changes underground are smaller than at the surface, and remain stable at around 13°C throughout the year.

[0018] For this reason, the temperature of groundwater also changes little throughout the year, maintaining a temperature of about 10°C to 15°C, so air conditioning and cooling are not required in the summer.
It is widely used as a cold heat source for cooling, and in winter as a heat source for heating, snow removal, etc.

By the way, in underground aquifers, the ratio of groundwater to the total volume of aquifer a is usually 10 to 30.
%, and the remaining 70-90% is filled with soil particles.

[0020] If: Volumetric heat capacity of water 1000kcal/
m3・℃・Volume heat capacity of soil particles 550kcal
/m3・℃・Aquifer porosity 0.3(
30%), the heat capacity of 1 m3 of aquifer is 0.3 x 1000 kcal/m3・℃+(1-
0.3)×550kcal/m3・℃ ≒700
kcal/m3・℃ =685kcal/. ．． ．． 700kcal. ．．
．． becomes.

[0021] At this time, the ratio of heat capacity of soil particles to water is
(Heat capacity of water): (Heat capacity of soil particles) = 0.3 x 100
0:(1-0.3)×550
=300:3
It becomes 85.

That is, in the underground aquifer a,
More heat exists underground as the temperature of soil particles (sensible heat) than is stored as the temperature of groundwater.

A similar theory holds true for non-aquifer b.

Non-aquifer b Particularly non-aquifer b near aquifer a
As shown in the previous calculation, the soil particles in the (unsaturated layer)
This means that sensible heat energy comparable to the heat energy of groundwater in the same volume of aquifer a is stored.

Conventionally, in a saturated zone below the groundwater table, it has been possible to extract the heat of the groundwater and the thermal energy of soil particles using water as a medium by constructing a well and pumping up groundwater.

However, in the unsaturated zone above the groundwater table, there is no heat medium called groundwater, so it has been difficult to efficiently extract thermal energy from this area. The methods listed in the prior art section, such as the method of sucking the thermal energy around the hole and the method of burying pipes in multiple layers above and below to collect heat, have poor heat collection effects and are not economical, so they are not practical. It wasn't.

In the present invention, the thermal energy stored in the soil particles in the unsaturated zone can be forced to flow inside the non-aquifer by using air as a medium instead of groundwater, and by pressurizing or depressurizing it. The natural heat energy stored in the non-aquifer B is taken out to the ground using air as a medium, and this air is used as a heat source or cold source, and the air flows through the non-aquifer B. Because it directly collects heat energy when doing so, it is extremely economical and efficient to collect natural heat energy underground together with the air, and it is not possible to use conventional artificial heat storage by burying gravel underground. There is no such thing as creating a tank and passing hot or cold air through it to store hot or cold heat and use it as a heat source for various purposes. It becomes a large-capacity heat utilization system that can be easily and economically taken out and used simply by allowing the flow to pass through.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the present invention is comprised of an air collection device 1 installed underground and an air pump 2 for sucking air from a non-aquifer layer b.

[0029] As the air collecting device 1, a perforated pipe, a wire mesh pipe,
Any structure that can suck air from the soil, such as a cylinder with a bottom, may be used.

[0030]Furthermore, if the air collecting device 1 is connected to the voids of underground sewer pipes, electric conduit pipes, etc. in a communicating manner, existing underground facilities can also be used.

Furthermore, the air pump 2 utilizes various types of air pumps for suction and exhaust.

Next, as an applied example, an example in which the present invention is used as a heat source for road snow removal will be described with reference to FIGS. 3 and 4.

The suction device 6 and the air collection device 1 are installed in the underground non-aquifer b to the extent that the lower part thereof is close to or reaches the groundwater table.
is dug deeply, and an air collection screen 7 is installed in the air collection device 1,
Air at a temperature of 10 to 15°C is collected from this air collection screen 7,
This warm air is sent to the heat exchanger 14 by the air pump 2, and the cold air after heat exchange is forced into the suction device 6 and circulated. A heat exchange fluid such as warm air or river water heated by a heat exchanger 14 is transferred by a pump 8 via a pipeline 12 to a porous medium 1 buried under the pavement 10 of a road 9, for example.
1 and heats the pavement 10 to melt accumulated snow, or sprinkles water directly onto the pavement 10 to melt the snow.

[0034] For roof snow removal, the hot air is sent into the air bag 15 made of a semi-breathable material such as nylon cloth spread on the roof 13.
It is possible to melt the falling snow by the warm air that slowly leaks upward from 5.

Further, a method of melting snow by disposing a hot air discharge pipe or other device for melting snow using warm air instead of the air bag 15 on the roof 13 may be adopted.

[0036]

Effects of the Invention As described above, the present invention allows the natural thermal energy stored in the non-aquifer above the underground aquifer to be forced to flow inside the non-aquifer by pressurizing or depressurizing it. It is characterized by extracting the air above the ground as a medium and using this air as a heat source, so it is extremely efficient and uses air as a medium to utilize the hot or cold heat of soil particles underground, which was previously difficult to utilize. Since it can collect air economically, it has the following features.

(1) Cold air is forced into the suction device, the air is forced to flow through the non-aquifer, and the air is collected from the air collection device to use the natural thermal energy in the non-aquifer as a medium. Because it uses a method that collects heat, there are no problems with groundwater, such as water drying up or ground subsidence due to excessive pumping.

(2) Since air is used as a medium, there is less problem of well clogging and maintenance is easy.

(3) The heat capacity per unit volume of air is:
Because it is smaller than water, a larger volume of air is required than groundwater to obtain the same amount of heat.

[0040] For this reason, the diameter of the air pump and the diameter of the blower pipe will be larger than in the case of underground water, but since air is light,
The power required for an air pump to obtain the same amount of heat as groundwater is approximately the same as the power required for a water pump to pump up groundwater with the same amount of heat.

[0041] Therefore, the running cost is approximately the same as when pumping groundwater as a heat source.

(4) Heat storage is performed artificially by forcing air to flow widely in a non-aquifer through forced air injection and forced exhaust, and collecting natural thermal energy underground using air as a medium. It also becomes possible.

When storing heat underground using water as a medium,
Clogging that occurs in aquifers when water is injected has become a major problem.

When air is used as a medium, for example, if an air filter is used in the warm air suction vertical hole, there will be no problem of clogging, and heat can be easily collected and stored. (5) The present invention is particularly effective in areas where the groundwater level has significantly decreased due to excessive pumping of groundwater, and has the advantage that as the groundwater level decreases, the thickness of the unsaturated zone increases accordingly, and the amount of collected air increases accordingly. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an air collection device of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between an air collecting device and a suction device of the present invention.

FIG. 3 is an explanatory diagram of an embodiment in which air in a non-aquifer is circulated using an air gathering device and a suction device of the present invention, and heat is transferred by a heat exchanger.

FIG. 4 is an explanatory diagram of an application example in which the present invention is applied to a snow removal device.

[Explanation of symbols]

a Aquifer b Non-aquifer

Claims (1)

[Claims] Claim 1: The natural thermal energy stored in the non-aquifer above the underground aquifer is extracted to the surface using air that is forced to flow inside the non-aquifer by pressurization or depressurization as a medium. , a method of utilizing underground thermal energy characterized by using this air as a heat source.