JP5401248B2 - Geothermal heat collection system - Google Patents

Description

  The present invention relates to a geothermal heat collection system, and more particularly to a geothermal heat collection system capable of continuously collecting geothermal heat.

  In the background of so-called global environmental problems, a system that collects and uses geothermal heat has recently begun to be adopted as a form of natural energy utilization. As a technique for collecting ground heat, there is a method in which a ground heat collecting pipe through which a fluid heat medium flows is buried in the ground and heat is exchanged between the heat medium and the ground. When collecting geothermal heat with such a technique, the temperature difference between the heat medium and the ground becomes smaller as the collection of geothermal heat proceeds, and eventually a state of thermal saturation where geothermal heat cannot be collected may occur. . In order to prevent the ground heat from becoming impossible due to this thermal saturation, the groundwater around the underground heat collection pipe is pumped up and discharged above the underground heat collection pipe to obtain the underground heat collection. There is a geothermal heat collection system in which groundwater around a heat pipe is made to flow (see, for example, Patent Document 1).

JP 2007-24342 A (FIG. 9 etc.)

  However, in the above-described geothermal heat collection system, although the groundwater flow is initially good, it may eventually be thermally saturated.

  In view of the above-described problems, an object of the present invention is to provide a geothermal heat collection system capable of continuously collecting geothermal heat.

  In order to achieve the above object, the geothermal heat collection system according to the first aspect of the present invention has a groundwater above the original groundwater surface S0, which is the groundwater surface before pumping, as shown in FIG. A first pumping well 11 that pumps Gw, and a first lowered water surface S1 that is a groundwater surface that has been lowered by pumping groundwater Gw from the first pumping well 11, and a first groundwater surface S0 that is surrounded by the first groundwater surface S0. A first geothermal heat collection pipe 12 mainly disposed in the groundwater depletion region T1, wherein the first geothermal heat collection pipe 12 flows a heat medium Hm that exchanges heat with the ground heat. A first geothermal heat collecting unit 10 having: a second geothermal heat collecting unit 20 provided outside the first groundwater depleted region T1 as viewed from the ground surface, which is more than the original groundwater surface S0. From the second pumping well 21 that pumps the groundwater Gw upward and the second pumping well 21 Arranged mainly in the second groundwater depletion region T2 (see, for example, FIG. 3) surrounded by the second lowered water surface S2 (for example, see FIG. 3) and the original groundwater surface S0, which is the groundwater surface that has been lowered by the pumping of the groundwater Gw. A second geothermal heat collecting pipe 22, which is provided with a second geothermal heat collecting pipe 22 through which a heat medium Hm that exchanges heat with the ground heat flows. A thermal unit 20; first discharge pipes 13, 33, 14 for guiding the groundwater Gw pumped from the first pumping well 11 to the outside of the first groundwater depletion region T1 when viewed from the surface; and a second pumping well The second discharge pipes 23, 33, and 24 guide the groundwater Gw pumped from 21 to the outside of the second groundwater depletion region T <b> 2 (see, for example, FIG. 3) when viewed from the ground surface.

  When comprised in this way, when the amount of heat exchanged between the heat medium and the underground in the first underground heat sampling pipe decreases, the groundwater around the first underground heat sampling pipe is removed from the first pumping well. By pumping the water and guiding it to the outside of the first groundwater depleted region as seen from the ground surface, new groundwater can be guided to the first groundwater depleted region, and again the heat medium in the first underground heat collecting pipe The amount of heat exchanged with the ground can be increased, and heat exchange between the heat medium and the ground is performed in the second ground heat collection pipe until the first groundwater depleted region is filled with new groundwater. And can continue to collect geothermal heat.

  Moreover, the geothermal heat collection system which concerns on the 2nd aspect of this invention is a 1st pumping well in the geothermal heat collection system which concerns on the said 1st aspect of this invention, for example, as shown in FIG. There are a plurality of 11, and a first underground heat collecting pipe 12 is disposed between the plurality of first pumping wells 11 </ b> A and 11 </ b> B.

  If comprised in this way, it will become possible to expand further the deep part side of a 1st groundwater depletion area | region by pumping groundwater from several 1st pumping wells simultaneously, The 1st geothermal heat collection pipe circumference The groundwater can be replaced more reliably.

  Moreover, the geothermal heat collection system which concerns on the 3rd aspect of this invention is in the geothermal heat collection system 1 which concerns on the said 1st aspect or this 2nd aspect of this invention, for example, as shown in FIG. A seepage water tank 25 provided outside the first groundwater depletion region T1 when viewed from the ground surface above the original groundwater surface S0, and comprising an seepage water tank 25 for infiltrating the introduced groundwater into the ground; One end of the carry-out pipe 14 is connected to the permeate tank 25.

  With this configuration, the groundwater head introduced into the seepage water tank can infiltrate the groundwater into the ground, and the groundwater is returned to the ground, which suppresses adverse effects such as ground subsidence caused by pumping up the groundwater. can do.

  According to the present invention, when the amount of heat exchanged between the heat medium and the ground in the first underground heat sampling pipe decreases, groundwater around the first underground heat sampling pipe is removed from the first pumping well. By pumping the water and guiding it to the outside of the first groundwater depleted region as seen from the ground surface, new groundwater can be guided to the first groundwater depleted region, and again the heat medium in the first underground heat collecting pipe The amount of heat exchanged with the ground can be increased, and heat exchange between the heat medium and the ground is performed in the second ground heat collection pipe until the first groundwater depleted region is filled with new groundwater. And can continue to collect geothermal heat.

It is a schematic block diagram which shows the state which the groundwater surface by the side of one underground heat collection unit of the underground heat collection system which concerns on embodiment of this invention fell. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the component of the geothermal heat collection system which concerns on embodiment of this invention, (a) is a top view of a geothermal heat collection unit, (b) is a perspective view of a geothermal heat collection pipe, (C) is a see-through | perspective perspective view of the underground heat collecting pipe which concerns on a modification. It is a schematic block diagram which shows the state which the groundwater surface by the side of the other geothermal heat collection unit of the geothermal heat collection system which concerns on embodiment of this invention fell. It is a partial schematic block diagram of the geothermal heat collection unit which comprises the geothermal heat collection system which concerns on the modification of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, with reference to FIG. 1, the underground heat collection system 1 which concerns on embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of a geothermal heat collection system 1. The geothermal heat collection system 1 includes a first heat collection unit 10 as a first geothermal heat collection unit, a second heat collection unit 20 as a second geothermal heat collection unit, and a first First discharge pipes 13 and 14 constituting a carry-out pipe, second carry-out pipes 23 and 24 constituting a second carry-out pipe, a common carry-out pipe 33, a first water tank 15 and a second water tank 25 are provided. ing. The common carry-out pipe 33 serves as a part of the first carry-out pipe and a part of the second carry-out pipe. In the present embodiment, the first heat collecting unit 10 and the second heat collecting unit 20 have the same configuration.

  The 1st heat collecting unit 10 has the 1st pumping well 11 as a 1st pumping well, and the 1st heat collecting pipe 12 as a 1st underground heat collecting pipe. The first heat collecting unit 10 is installed in the ground below the ground surface Gs. In the present embodiment, the first pumping well 11 and the first heat collecting pipe 12 are embedded in the aquifer. The aquifer is a permeable layer that has a large gap between the particles forming the formation and is saturated with groundwater. The groundwater is pressurized groundwater or free groundwater depending on the geology (stratum). In the present embodiment, the original groundwater surface S0 exists in the ground. The original groundwater surface S0 is a groundwater surface before the groundwater Gw is pumped through the pumping well. The first heat collecting unit 10 of the present embodiment has one first pumping well 11 and a plurality of first heat collecting tubes 12.

  The first pumping well 11 includes a pumping pump 11p and a pumping pipe 11v connected to the pumping pump 11p in a sleeve 11s. The sleeve 11s is typically a cylindrical member and is disposed such that its axis is vertical. The sleeve 11s typically has slit-like pores formed on the side surface through which the groundwater Gw passes but does not pass through the soil, but the pores may be omitted. The inside of the sleeve 11s is filled with groundwater Gw without entering soil, and the original groundwater surface S0 appears. In the present embodiment, the upper end of the sleeve 11 s is closed by the bottom surface of the first water tank 15. The pumping pump 11p is installed in an aquifer deeper than the original groundwater surface S0, and is installed, for example, at a depth of 30 m to 60 m from the original groundwater surface S0. One end of the pumping pipe 11v is connected to the discharge side of the pumping pump 11p, and the other end penetrates the bottom surface of the first water tank 15.

  In the present embodiment in which there is one first pumping well 11, when the groundwater Gw is pumped by starting the pumping pump 11 p, the groundwater surface around the first pumping well 11 is lowered and the first pumping well 11 is An inverted conical groundwater surface with a certain point at the top appears. The groundwater surface that has been lowered by pumping the groundwater Gw from the first pumping well 11 is referred to as a first lowered water surface S1 (hereinafter referred to as “first lowered water surface S1”), the original groundwater surface S0 and the first lowered water surface S1. The area surrounded by is referred to as a first depletion area T1 which is a first groundwater depletion area. The original groundwater surface S0 and the first lowered water surface S1 do not appear at the same time but appear with a time difference. However, the original groundwater surface S0 in the concept of the first depletion region T1 is considered to be before the start of pumping. The first depletion region T1 appears due to the pumping of the groundwater Gw from the first pumping well 11, and does not appear before the pumping.

  The first heat collecting pipe 12 is a member that flows a heat medium Hm that conveys underground heat to a use place, and is typically disposed mainly in the first depletion region T1 with its axis line directed vertically. Yes. “Mainly disposed” means a state in which at least half of the surface area is present in the first depletion region T1, preferably 70% or more, more preferably 90% or more. The entire first heat collecting tube 12 may exist in the first depletion region T1 (that is, 100% of the surface area exists in the first depletion region T1).

  Here, the details of the first heat collecting tube 12 will be described with reference to FIG. FIG. 2 is a view for explaining the periphery of the first heat collecting pipe 12 that is a component of the geothermal heat collecting system 1. FIG. 2A is a plan view of the first heat collecting unit 10, and FIG. It is a see-through | perspective perspective view when it assumes that the heat pipe | tube 12 is transparent. First, the planar arrangement of the first heat collecting tubes 12 will be described with reference to FIG. In the present embodiment, eight first heat collecting tubes 12 are arranged so as to surround the square first water tank 15 when viewed from the ground surface (in plan view). A first pumping well 11 is disposed at the center (intersection of diagonal lines) of the first water tank 15. The distance L1 between the adjacent first heat collecting tubes 12 is preferably equal to or longer than the distance that does not affect the heat exchange between the heat medium Hm and the ground in the adjacent first heat collecting tubes 12. In addition, the distance between the first pumping well 11 and the first heat collecting pipe 12 is such that the surface area of the first heat collecting pipe 12 is first depleted in view of the fact that the first lowered water surface S1 (see FIG. 1) has an inverted conical shape. It is preferable to limit the distance to exist as much as possible in the region T1 (see FIG. 1). Considering these circumstances, in the present embodiment, the distance L1 between the axes of the adjacent first heat collecting tubes 12 is 4 to 5 m, and the radius L2 centered on the first pumping well 11 is 7.1 m. The first heat collecting tubes 12 are arranged in such a manner that the axes of all the first heat collecting tubes 12 are included in the inside. The distance L1 can be adjusted as appropriate according to the thermal conductivity of the geology (for example, if the thermal conductivity is small, the interval is narrowed), and the radius L2 can be adjusted accordingly.

  As shown in FIG. 2 (b), the first heat collecting pipe 12 includes an outer pipe 12s in contact with the ground, an introduction pipe 12c disposed in the outer pipe 12s and introducing the heat medium Hm into the outer pipe 12s, A lead-out pipe 12d connected to the upper side wall of the outer pipe 12s and leading out the heat medium Hm in the outer pipe 12s to the outside of the first heat collecting pipe 12 is provided. In the present embodiment, the introduction pipe 12c is disposed coaxially with the outer pipe 12s. The introduction pipe 12c is a lower part in the outer pipe 12s and has a lower end opened slightly above the bottom surface of the outer pipe 12s, and an upper end is a lid (not shown) provided on the upper end of the outer pipe 12s or the outer pipe 12s. Is extended to the outside of the outer tube 12s. The outer pipe 12s may be a steel pipe that is a material having a relatively high thermal conductivity from the viewpoint of improving the heat transfer coefficient with the ground. The introduction pipe 12c is preferably a resin pipe from the viewpoint of suppressing heat transfer between the heat medium Hm inside and outside the introduction pipe 12c, but a steel pipe may be used from the viewpoint of improving the strength. As shown in the plan view of FIG. 2A, each of the plurality of first heat collecting pipes 12 has an upper end of the introduction pipe 12c connected to the introduction branch pipe 41c, and a lead-out pipe 12d connected to the lead-out branch pipe 46d. Yes. Each introduction branch pipe 41c is connected to the first outgoing pipe 41, and is configured such that the heat medium Hm is distributed from the first outgoing pipe 41 constituting one flow path to each introduction branch pipe 41c. Each lead-out branch pipe 46d is connected to the first return pipe 46, and is configured such that the heat medium Hm from each lead-out branch pipe 46d gathers in the first return pipe 46 constituting one flow path. The heat medium Hm is typically water, and the system of the heat medium Hm is configured not to mix with the underground groundwater Gw.

  In addition, like the 1st heat collection pipe | tube 12A which concerns on the modification shown in FIG.2 (c), the derivation | leading-out pipe | tube 12e equivalent to the derivation | leading-out pipe | tube 12d in the 1st heat collection pipe | tube 12 (refer FIG.2 (b)) is 12 s of outer tubes. Instead of being connected to the side wall, it may be arranged side by side with the introduction pipe 12c in the outer pipe 12s. At this time, it is preferable that the lower end of the outlet pipe 12e is opened above the lower end of the introduction pipe 12c, typically at the top of the outer pipe 12s as much as possible. Further, the upper end of the outlet tube 12e extends through the outer tube 12s to the outside of the outer tube 12s.

  Returning to FIG. 1 again, referring to FIG. 2 as appropriate, the description of the configuration of the geothermal heat collection system 1 will be continued. The first water tank 15 is an osmotic water tank that allows the introduced groundwater Gw to penetrate into the ground. The first water tank 15 has, for example, a water-permeable sheet and a permeation hole on the surface in contact with the ground, and is configured so that the internal ground water Gw can permeate into the outside ground. The structure which can permeate may be employ | adopted. The first water tank 15 is installed above the original groundwater surface S0. In the present embodiment, the entirety including the bottom surface of the first water tank 15 is installed above the original groundwater surface S0. If comprised in this way, the position head at the time of diffusing internal groundwater Gw to an aquifer can be taken large. As described above, the sleeve 11 s is in contact with the bottom surface of the first water tank 15, but the pumping pipe 11 v penetrates the bottom surface of the first water tank 15 and is disposed in the first water tank 15. It is connected to the.

  In the present embodiment, the second heat collecting unit 20 is configured in the same structure as the first heat collecting unit 10 as described above. Specifically, the second heat collecting unit 20 has a second pumping well 21 and a second heat collecting pipe 22 as a configuration corresponding to the first pumping well 11 and the first heat collecting pipe 12 of the first heat collecting unit 10. doing. The second pumping well 21 includes a pumping pump 21p, a pumping pipe 21v, and a sleeve 21s corresponding to the pumping pump 11p, the pumping pipe 11v, and the sleeve 11s of the first pumping well 11, respectively. The second heat collecting tube 22 has an outer tube 22s, an introducing tube 22c, and an outlet tube 22d corresponding to the outer tube 12s, the introducing tube 12c, and the outlet tube 12d of the first heat collecting tube 12, respectively. When the second heat collecting unit 20 and the first heat collecting unit 10 have the same structure (including symmetrical arrangement) including the capacity of the pumps 11p and 21p, the size of the permeate tank, and the like, the design becomes common, Construction is also easy.

  As will be understood with reference to FIG. 3 as well, in the second heat collecting unit 20, as a concept corresponding to the first lowered water surface S1 and the first depleted region T1 in the first heat collecting unit 10, There is a lowered water surface S2 (a groundwater surface that has been lowered by pumping the groundwater Gw from the second pumping well 21, and hereinafter referred to as a “second lowered water surface S2”) and a second depleted region T2 that is a second groundwater depleted region. To do. The second depletion region T2 is a region surrounded by the original groundwater surface S0 and the second lowered water surface S2. A second water tank 25 is installed above the original groundwater surface S0 above the sleeve 21s. The sleeve 21s is in contact with the bottom surface of the second water tank 25, but the pumping pipe 21v passes through the bottom surface of the second water tank 25 and is connected to the second carry-out pipe 23 disposed in the second water tank 25. Yes. Further, when viewed from the ground surface Gs (in plan view), the first heat collection unit 10 is provided outside the second depletion region T2, and the second heat collection unit 20 is provided outside the first depletion region T1. ing.

  In the present embodiment, eight second heat collection tubes 22 are mainly arranged in the second depletion region T2 so as to surround the square second water tank 25 in a plan view, typically with the axis line oriented vertically. It is installed. In each of the plurality of second heat collecting tubes 22, the upper end of the introduction pipe 22c is connected to the introduction branch pipe 42c, and the lead-out pipe 22d is connected to the lead-out branch pipe 47d. Each introduction branch pipe 42c is connected to the second forward pipe 42, and is configured such that the heat medium Hm is distributed from the second forward pipe 42 constituting one flow path to each introduction branch pipe 42c. Each lead-out branch pipe 47d is connected to the second return pipe 47, and is configured such that the heat medium Hm from each lead-out branch pipe 47d gathers in the second return pipe 47 constituting one flow path.

  The first carry-out pipe 13 that has passed through the first water tank 15 is connected to the common carry-out pipe 33 and the second carry-out pipe 24. The other end (terminal) of the second carry-out pipe 24 opens in the first water tank 15. The second carry-out pipe 24 is provided with an on-off valve 24v capable of blocking the flow path of the groundwater Gw flowing inside. The other end of the common carry-out pipe 33 is connected to the second carry-out pipe 23 and the first carry-out pipe 14 on the second water tank 25 side. The other end of the first carry-out pipe 14 opens in the second water tank 25. The first carry-out pipe 14 is provided with an on-off valve 14v that can block the flow path of the groundwater Gw flowing inside. By opening the on-off valve 14v and closing the on-off valve 24v, the groundwater Gw pumped from the first pumping well 11 can be caused to flow into the second water tank 25, and the on-off valve 24v is opened to close the on-off valve 14v. The groundwater Gw pumped from the two pumping wells 21 is configured to flow into the first water tank 15. At this time, since the common carry-out pipe 33 serves as both the first carry-out pipe and the second carry-out pipe, the initial cost can be reduced and the construction can be simplified.

  The underground heat collection system 1 also includes a heat pump chiller 51 as a heat source device. The heat pump chiller 51 is a device that adjusts the temperature of the cold / hot water CH using the heat medium Hm as a heat source. The cold / hot water CH typically circulates between the heat pump chiller 51 and the heat use place where cooling or heating is performed via the secondary side pipe 49. The cold / hot water CH is transported to and used by the start of the secondary pump 49p, and returns to the heat pump chiller 51 after the heat is used. In addition to the secondary side pipe 49, the main pump pipe 43 that leads out the heat medium Hm and the main return pipe 48 that introduces the heat medium Hm are connected to the heat pump chiller 51. The main return pipe 48 is provided with a heat medium pump 48p for flowing the heat medium Hm. The heat pump chiller 51 used in the geothermal heat collection system 1 may be a general-purpose product.

  A first outgoing pipe 41 and a second outgoing pipe 42 are connected to the other end of the main outgoing pipe 43. The first outgoing pipe 41 is a pipe that mediates between the main outgoing pipe 43 and each introducing branch pipe 41c, and the second outgoing pipe 42 is a pipe that mediates between the main outgoing pipe 43 and each introducing branch pipe 42c. The first forward pipe 41 is provided with an on-off valve 41v capable of blocking the flow path of the heat medium Hm flowing inside. The second forward pipe 42 is provided with an on-off valve 42v capable of blocking the flow path of the heat medium Hm flowing inside. A first return pipe 46 and a second return pipe 47 are connected to the other end of the main return pipe 48. The first return pipe 46 is a pipe that mediates between the main return pipe 48 and each outlet branch pipe 46d, and the second return pipe 47 is a pipe that mediates between the main return pipe 48 and each outlet branch pipe 47d. The first return pipe 46 is provided with an on-off valve 46v capable of blocking the flow path of the heat medium Hm flowing inside. The second return pipe 47 is provided with an on-off valve 47v capable of blocking the flow path of the heat medium Hm flowing inside.

  The operation of the underground heat collection system 1 will be described with reference to FIGS. 1 to 3. The temperature of the underground aquifer is stable at about 15 ° C to 18 ° C throughout the year. Below, the example which extract | collects cold from underground is demonstrated. Initially, the surface of the groundwater Gw is on the original groundwater surface S0, and the first pumping well 11 and the second water well 21 above the original groundwater surface S0 are empty, and the first water tank 15 and the second water tank 25 are empty. The interior of is empty. Since the 1st heat collecting pipe 12 and the 2nd heat collecting pipe 22 are closed flow paths which constitute the flow path of the heat medium Hm, the heat medium Hm is filled regardless of the water surface fluctuation of the groundwater Gw.

  First, the case where cold heat | fever is extract | collected from the 1st heat collecting unit 10 side is demonstrated. When the ground heat is collected from the first heat collecting unit 10, the on-off valve 41v and the on-off valve 46v are opened, and the on-off valve 42v and the on-off valve 47v are closed. When the heat medium pump 48p is started in this state, the heat medium Hm flows. At this time, the heat medium Hm of the heat pump chiller 51 flows through the first forward pipe 41 via the main forward pipe 43 and is distributed to each introduction branch pipe 41c. The heat medium Hm flowing into the introduction branch pipe 41 c flows into the introduction pipe 12 c of the first heat collecting pipe 12. At this time, the heat medium Hm is at a temperature higher than the underground temperature. The heat medium Hm flowing through the introduction pipe 12c flows out from the opening at the lower end into the outer pipe 12s and rises toward the outlet pipe 12d connected to the upper part.

  The heat medium Hm collects ground heat by exchanging heat with the ground when rising in the outer pipe 12s. Here, the temperature of the heat medium Hm decreases due to the heat exchange between the two, and the underground temperature increases. That is, the heat medium Hm here collects cold from the ground. The heat medium Hm whose temperature has been reduced by collecting the cold heat flows out from the first heat collecting pipe 12 through the outlet pipe 12d, flows through the outlet branch pipe 46d, and reaches the first return pipe 46. In the first return pipe 46, the heat medium Hm gathers from each outlet branch pipe 46d. The heat medium Hm flowing through the first return pipe 46 flows into the heat pump chiller 51 through the main return pipe 48. The heat medium Hm flowing into the heat pump chiller 51 cools a refrigerant (not shown) that performs a refrigeration cycle in the heat pump chiller 51, and the temperature of the heat medium Hm rises and is derived from the heat pump chiller 51. The heat medium Hm whose temperature has increased is transported to the first heat collecting pipe 12 in the above-described manner, and after being cooled by heat exchange with the ground, it is returned to the heat pump chiller 51 again. The refrigerant (not shown) cooled to the heat medium Hm in the heat pump chiller 51 is depressurized in a liquid state, exchanges heat with the cold / hot water CH, and takes away the latent heat when evaporating from the cold / hot water CH. To cool cold / hot water CH. The cooled cold / hot water CH is transported to a heat utilization place and used for cooling (including heat storage). Depending on the geology, geothermal heat is collected for about 1 to 5 days, about half a month if it is long, and about a month if it is longer.

  Now, when the heat medium Hm collects the cold in the ground in the above-described manner, the temperature in the ground gradually rises, and the temperature difference between the ground and the heat medium Hm becomes smaller, and as expected. It becomes impossible to collect the cold heat in the ground. Still, if geothermal heat is continuously collected, the ground will eventually be thermally saturated, and the heat medium Hm cannot be cooled by the cold in the ground. In order to avoid such inconvenience, in the geothermal heat collection system 1, when the exchange heat amount between the underground and the heat medium is decreased, the second heat collection unit 10 is used as the ground heat collection destination. Switch to thermal unit 20. The timing for switching the ground heat collection destination is provided with a temperature sensor (not shown) for measuring the temperature of the heat medium Hm flowing into the heat pump chiller 51, and the temperature measured by the temperature sensor (not shown) is below a predetermined temperature. Or when the predetermined time has elapsed since the heat medium pump 48p was started.

  When switching the ground heat collection destination, the on-off valve 42v and the on-off valve 47v are opened, and then the on-off valve 41v and the on-off valve 46v are closed. Then, the heat medium Hm flowing out from the heat pump chiller 51 and flowing through the main forward pipe 43 flows through the second forward pipe 42 and is distributed to the respective introduction branch pipes 42c. The heat medium Hm flowing into the introduction branch pipe 42 c flows into the introduction pipe 22 c of the second heat collection pipe 22. The heat medium Hm flowing through the introduction pipe 22c flows out from the opening at the lower end into the outer pipe 22s and rises toward the top. The heat medium Hm exchanges heat with the ground while rising in the outer tube 22s, and the temperature of the heat medium Hm decreases and the temperature of the ground increases. The heat medium Hm whose temperature has been reduced by collecting the cold heat flows out from the second heat collecting pipe 22 through the outlet pipe 22d, flows through the outlet branch pipe 47d, and reaches the second return pipe 47. The heat medium Hm gathers from each outlet branch pipe 47d to the second return pipe 47, and the heat medium Hm flowing through the second return pipe 47 flows into the heat pump chiller 51 via the main return pipe 48. The heat medium Hm that has flowed into the heat pump chiller 51 cools a refrigerant (not shown) that performs a refrigeration cycle in the heat pump chiller 51, and the temperature of the heat medium Hm rises and is derived from the heat pump chiller 51. .

  As described above, by appropriately switching the ground heat collection destination from the first heat collecting unit 10 to the second heat collecting unit 20, the ground heat can be continuously collected. By the way, after switching the collection source of geothermal heat from the 1st heat collection unit 10 whose exchange heat quantity with the heat carrier Hm decreased as mentioned above to the 2nd heat collection unit 20 which can collect geothermal heat. It takes a considerable time for the underground temperature around the first heat collecting tube 12 of the first heat collecting unit 10 to return to the temperature at which the original underground heat can be collected (for example, 15 ° C. to 18 ° C.). There are many cases. If the underground around the second heat collecting tube 22 of the second heat collecting unit 20 is thermally saturated before the underground temperature around the first heat collecting tube 12 returns to a temperature at which the underground heat can be collected, it continues. It becomes difficult to collect ground heat. Therefore, in the geothermal heat collection system 1, an appropriate time (typically, the second heat collection pipe 22) after the geothermal heat collection destination is switched from the first heat collection unit 10 to the second heat collection unit 20. The following operation is performed at a timing when the underground temperature around the first heat collecting pipe 12 of the first heat collecting unit 10 is restored before the surrounding ground is thermally saturated.

  First, the open / close valve 24v is closed and the open / close valve 14v is opened, and then the pumping pump 11p is activated. Then, the groundwater Gw pumped by the pumping pump 11p flows through the first carry-out pipe 13 on the first heat collection unit 10 side, the common carry-out pipe 33, and the first carry-out pipe 14 on the second heat collection unit 20 side to be second. It flows into the water tank 25. Thereby, the water surface of the groundwater Gw gradually decreases from the original groundwater surface S0 around the first pumping well 11, and eventually becomes the first reduced water surface S1 as shown in FIG. In the present embodiment, the pumping pump 11p is operated at a flow rate that decreases from the original groundwater surface S0 to the first reduced water surface S1 over approximately one to two days. Although depending on the geology, since the groundwater content in the aquifer is generally 10 to 15%, the discharge flow rate of the pumping pump 11p is relatively small, and the pumping pump 11p of the present embodiment is 1.5 kW to 2. About 2kW is enough. Further, considering the flow rate of the groundwater Gw, the groundwater Gw for the first depletion region T1 is transported to the first water tank 15 over about 1 to 2 days. Although the groundwater Gw having a relatively high temperature flows into the second water tank 25 from the first carry-out pipe 14 by the activation of the pumping pump 11p, the flow rate of the groundwater Gw flowing into the second water tank 25 from the first carry-out pipe 14 is small. It does not affect the heat collection of the underground heat around the second heat collection tube 22.

  When the water surface of the groundwater Gw is lowered to the first lowered water surface S1, the groundwater Gw around the main portion of the first heat collecting pipe 12 is once removed, and the first depletion region T1 appears. At this time, since the second water tank 25 that is a destination of the groundwater Gw pumped by the pumping pump 11p is installed outside the first depletion region T1 in a plan view, the groundwater Gw pumped by the pumping pump 11p is There is no immediate short circuit to the first depletion region T1. When the groundwater Gw around the main part of the first heat collecting pipe 12 is removed, the pumping pump 11p is stopped. Then, the water surface of the groundwater Gw that has decreased to the first lowered water surface S1 tries to return to the original groundwater surface S0, and the groundwater Gw outside the first depleted region T1 flows into the first depleted region T1 due to pressure. At this time, a position head is added to the periphery of the second water tank 25 only by the water level in the second water tank 25, but since the pressure is generally larger than this position head, the groundwater Gw outside the first depletion region T1 is the first. 1 enters the depletion region T1. The groundwater Gw in the second water tank 25 approaches the underground temperature (for example, 15 ° C. to 18 ° C.) in the process of slowly diffusing into the surrounding ground, and eventually becomes the original underground temperature. Although the speed at which the groundwater Gw flows in the ground varies depending on the geology, in this embodiment, the surface of the groundwater Gw from the first lowered water surface S1 takes about 2 to 4 days after the pumping pump 11p is stopped. Return to the original groundwater surface S0. The newly introduced groundwater Gw around the first heat collecting pipe 12 has not been affected by the heat exchange performed around the first heat collecting pipe 12, and has returned to the original underground temperature. By exchanging the groundwater Gw subjected to heat exchange in this way, the underground temperature can be returned to the original temperature earlier than in the case where it is not exchanged.

  Thus, when the underground temperature on the first heat collecting unit 10 side has returned to the original state, when the amount of collected cold heat on the second heat collecting unit 20 side currently collecting the underground heat has decreased, By switching the medium heat collection destination from the second heat collection unit 20 to the first heat collection unit 10, the underground heat can be continuously collected. Then, in order to restore the underground temperature on the second heat collecting unit 20 side this time, the open / close valve 14v is closed, the open / close valve 24v is opened, the pumping pump 21p is started, and pumping is performed by the pumping pump 21p. The groundwater Gw is conveyed to the first water tank 15, and the water surface of the groundwater Gw is lowered to the second lowered water surface S2 as shown in FIG. 3 to temporarily remove the groundwater Gw around the main portion of the second heat collecting pipe 22. When the groundwater Gw around the main portion of the second heat collecting pipe 22 is removed, the pumping pump 21p is stopped, and the groundwater Gw outside the second depletion region T2 flows into the second depletion region T2, and the second The ground temperature on the heat collection unit 20 side is returned to the original temperature at an early stage. As described above, the geothermal heat can be stably and continuously maintained by appropriately switching the ground heat collection destination and replacing the groundwater Gw on the first heat collection unit 10 side and the second heat collection unit 20 side. It is possible to collect heat. In consideration of the replacement of the groundwater Gw, the timing for switching the ground heat collection destination is when the temperature measured by the temperature sensor (not shown) is equal to or lower than the predetermined temperature, or when the heat medium pump 48p is turned on. In addition to when a predetermined time has elapsed since startup, the pumping pump 11p (or pumping pump 21p) is stopped, and then ground heat is collected in the first depletion region T1 (or second depletion region T2). The time until the groundwater Gw is filled again to such an extent that it can be heated may be measured in advance.

  As explained so far, the geothermal heat collection system 1 according to the present embodiment of the present invention does not simply circulate groundwater around the geothermal heat collection pipe as in the prior art, but collects ground heat. Since the previous switching and the replacement of the groundwater Gw are appropriately performed on the first heat collecting unit 10 side and the second heat collecting unit 20 side, the underground heat can be collected stably and continuously. In addition, since ground heat is used through the heat medium Hm without directly introducing the groundwater Gw into the heat pump chiller 51, the pumping flow rate of the groundwater Gw and the introduction flow rate of the heat medium Hm into the heat pump chiller 51 are individually set. It is possible to control the temperature of the heat source device stably and to collect stable underground heat and to avoid introduction of water mixed with foreign matter into the heat pump chiller 51, thereby extending the life of the heat source device. it can.

  Although the case where cold heat is collected has been described above, it goes without saying that the present invention can also be applied when heat is collected. When collecting the heat, the temperature of the heat medium Hm flowing from the introduction pipes 12c and 22c into the outer pipes 12s and 22s is lower than the temperature in the ground, and the heat that has been raised by collecting the ground heat. The medium Hm gives heat to a refrigerant (not shown) that performs a heat pump cycle in the heat pump chiller 51, and the temperature of the medium Hm decreases.

  In the above description, the geothermal heat collection system 1 is provided with the first water tank 15 and the second water tank 25, but the groundwater Gw pumped from the first (second) pumping well 11 (12) is the first. If the 1 (second) depletion region T1 (T2) is led outside, the pumped groundwater Gw may be directly returned to the ground without providing the first water tank 15 and / or the second water tank 25. Alternatively, when it is not necessary to return the pumped groundwater Gw to the ground, it may be used as domestic water. Moreover, also when providing the 1st water tank 15 and / or the 2nd water tank 25, the pit of the building located in the outer side of 1st (2nd) depletion area | region T1 (T2) is made into 1st (2nd) water tank 15 (25, for example. ).

  In the above description, the sleeve 11s (21s) and the first (second) heat collection tube 12 (22) are arranged so that their axes are vertical, but the axes are diagonal or horizontal. It may be arranged. However, from the viewpoint of reducing the area of the groundwater removal part in the plane so that it is easy to remove the groundwater Gw around the main part of the first (second) heat collection pipe 12 (22) and underground heat collection From the viewpoint of reducing the installation area of the system 1, it is preferable that the system is disposed so that the axis is vertical.

  In the above description, the plurality of first heat collecting tubes 12 are installed in a square shape as viewed from the ground surface, but may be installed on the circumference of the radius L2 centered on the first pumping well 11, Alternatively, if a main portion is present in the first depletion region T1, heat contamination (here, one first heat collecting tube 12 is inhibited from heat exchange with the ground by another first heat collecting tube 12). May be installed at random within the range that does not generate.

  In the above description, the geothermal heat collection system 1 is provided with the heat pump chiller 51, but the cold or warm heat possessed by the heat medium Hm may be directly used. Further, although the heat source device is the heat pump chiller 51, other heat source devices such as a refrigerator may be used.

In the above description, the first heat collecting unit 10 is arranged so that one first pumping well 11 is surrounded by a plurality of first heat collecting tubes 12 when viewed from the ground surface (in plan view). The configuration may be as follows.
FIG. 4 is a partial schematic configuration diagram of a geothermal heat collection unit (hereinafter referred to as “first heat collection unit 10 </ b> A”) constituting a geothermal heat collection system according to a modification of the embodiment of the present invention. . The first heat collecting unit 10A is different from the first heat collecting unit 10 (see FIGS. 1 to 3) in that it includes two pumping wells having the same configuration as the first pumping well 11 (see FIGS. 1 to 3) ( 1st pumping well 11A, 11B) The point which the 1st heat collecting pipe 12 is installed between the two 1st pumping wells 11A, 11B. In FIG. 4, the number of the first heat collecting tubes 12 is one, but what is shown is the first heat collecting tube 12 that is installed at a minimum, and the first heat collecting tube 12 that is not actually illustrated is shown. Is also installed. At this time, typically, a plurality of first heat collecting tubes 12 are installed so as to surround each of the first pumping wells 11A and 11B, and at least one of the plurality of first heat collecting tubes 12 ( Typically, a plurality of) are the first heat collecting tubes 12 installed between the two first pumping wells 11A and 11B. The interval between the two first pumping wells 11A and 11B may be about 1.3 to 3 times, preferably twice the distance L1 (see FIG. 2A). The configuration of the first carry-out pipe 13 and the like other than the above is the same as that of the first heat collecting unit 10 (see FIGS. 1 to 3).

  In the first heat collecting unit 10A configured as described above, when the heat exchange amount between the heat medium Hm and the ground is reduced and the ground heat collecting destination is switched to the second ground heat collecting unit side. In addition, the pumps 11pA and 11pB included in the two first pumping wells 11A and 11B are simultaneously activated. When the groundwater Gw is pumped by both the pumps 11pA and 11pB, the surface of the groundwater Gw gradually decreases from the original groundwater surface S0, and eventually becomes the first lowered water surface S1A as shown in FIG. As shown in FIG. 4, the first lowered water surface S1A in the first heat collecting unit 10A has an upwardly convex arch shape between the two first pumping wells 11A and 11B. As is clear from FIG. 4, in the first heat collecting unit 10A, the first depletion region T1 between the two first pumping wells 11A and 11B is increased by the amount of the first lowered water surface S1A falling. Thereby, the part which removes the groundwater Gw around the 1st heat collecting pipe 12 installed in the said part can be enlarged, and it becomes possible to replace | exchange the groundwater Gw around the 1st heat collecting pipe 12 reliably. . The second underground heat collecting unit side may also be the second heat collecting unit 20A having the same configuration as the first heat collecting unit 10A.

  In the above description, the geothermal heat collection system 1 is configured so that the first heat collection unit 10 (10A) and the second heat collection unit 20 (20A) have the same configuration, but the first (second) ) Arrangement and number of pumping wells 11 (21) and / or first (second) heat collection pipes 12 (22), presence / absence of surrounding first (second) water tank 15 (25), first (second) The configuration and the like of the carry-out pipes 13 and 14 (23 and 24) may be appropriately changed so that the first heat collecting unit 10 (10A) and the second heat collecting unit 20 (20A) are different from each other.

DESCRIPTION OF SYMBOLS 1 Geothermal heat collecting system 10 1st heat collecting unit 11 1st pumping well 12 1st heat collecting pipes 13 and 14 1st carrying-out pipe 15 1st water tank 20 2nd heat collecting unit 21 2nd pumping well 22 2nd heat collecting pipe 23, 24 Second unloading pipe 25 Second water tank 33 Common unloading pipe Hm Heat medium S0 Original groundwater surface S1 First lowered water surface S2 Second lowered water surface T1 First depletion region T2 Second depletion region

Claims (3)

A first pumping well that pumps groundwater above the original groundwater surface, which is the groundwater surface before pumping,
A first ground mainly disposed in a first groundwater depleted region surrounded by a first lowered water surface that is a groundwater surface lowered by pumping groundwater from the first pumping well and the original groundwater surface. A first heat collecting pipe, which is a medium heat collecting pipe, and causes a heat medium to exchange heat with the ground heat to flow inside;
A first geothermal heat collecting unit having:
A second geothermal heat collecting unit provided outside the first groundwater depleted region as seen from the ground surface,
A second pumping well for pumping up groundwater above the original groundwater surface;
The second ground mainly disposed in the second groundwater depleted region surrounded by the second lowered water surface which is the groundwater surface lowered by the groundwater pumping from the second pumping well and the original groundwater surface. A second heat collecting pipe, which is a medium heat collecting pipe, and causes a heat medium to exchange heat with the ground heat to flow inside;
A second underground heat collection unit having:
A first discharge pipe that guides groundwater pumped from the first pumping well to the outside of the first groundwater depleted region as viewed from the ground surface;
A second discharge pipe for guiding the groundwater pumped from the second pumping well to the outside of the second groundwater depleted region as seen from the ground surface;
Geothermal heat collection system. A plurality of the first pumping wells, and the first geothermal heat collecting pipe is disposed between the plurality of the first pumping wells;
The geothermal heat collection system according to claim 1. An osmotic water tank provided outside the first groundwater depletion region as seen from the ground surface above the original groundwater surface, and comprising an osmotic water tank that permeates the introduced groundwater into the ground;
The end of the first carry-out pipe was connected to the permeate tank;
The geothermal heat collection system according to claim 1 or 2.

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