Device for utilizing hydrothermal energy

Abstract

Device for utilizing hydrothermal energy with at least one first well (20) arranged adjacent to a body of water (10) and equipped for pumping bank filtrate, and a heat pump (30) connected to the at least one first well (20) by means of at least one source supply line (QVL), which is connected to at least one consumer by means of at least one consumer supply line (VVL) and at least one consumer return line (VRL), characterized in that the at least one first well (20) is arranged at a distance from the body of water (10) such that the course of the seasonal temperature fluctuations of the bank filtrate pumped from the at least one first well (20) is offset from the course of the seasonal temperature fluctuations of the body of water by at least three and at most nine months.

Description

[0001] The invention relates to a device for utilizing hydrothermal energy with at least one first well arranged adjacent to a body of water and equipped for pumping bank filtrate, and a heat pump connected to the at least one first well by means of at least one source supply line, which is connected to at least one consumer by means of at least one consumer supply line and at least one consumer return line.

[0002] The global transformation of all forms of energy production to sustainable processes without the use of fossil fuels also affects all forms of heat production. For domestic, institutional, commercial, and industrial heating needs requiring temperatures between approximately 40 and 90 °C, heat pumps of all types will likely play the most significant role. Heat pumps extract heat from a natural medium (water, air, ground, etc.) using electricity. This process cools the medium according to the laws of thermodynamics, and the resulting heat is then transferred to another medium, usually water in the supply line of a district heating network, raising it to a higher temperature.

[0003] A key aspect of all these processes is the temperature level of the starting medium: the higher this temperature, the more heat can be extracted from the medium itself and the more thermal energy (kWh) can be recovered.Wärme ) can be generated per kWh of electricity consumed by the heat pump. This transformation efficiency in kWh Wärme The energy output per kWh of electrical energy consumed by a heat pump is referred to as the "Coefficient of Performance" (COP) and ranges from 1 to 9, depending on the pump type, medium, and temperatures of the source and target media. A COP of 1, for example, is achieved when an electric heating element is immersed in water; then 1 kWh generates el approx. 1 kWh Wärme , the worst possible COP from an economic standpoint. The highest COP values ​​are achieved with water as both the input and output medium and small temperature differences between these two media.

[0004] It follows directly from this that it would be economically advantageous if the starting medium had as high a temperature as possible: this would result in a high COP and correspondingly little medium would be consumed.

[0005] The use of water bodies of all kinds as a medium for heat extraction is now being investigated and implemented in many projects worldwide, e.g. Rhine water near Mannheim and North Sea water near Esbjerg in Denmark, where the water is extracted directly from the water body or via very close bank wells directly on the water body.

[0006] It is also known from DE 196 25 116 A1 to convey the heat or cold energy of a surface water body via an infiltration area using the infiltration water into the groundwater aquifer and to extract and use it via a well.

[0007] However, in temperate climates, where heating demand is much higher in winter than in summer—in Germany, for example, the demand for residential and hot water heating is approximately five times higher in winter than in summer—the problem arises that almost all natural media have lower temperatures in winter than in summer. In particular, the annual temperature profile of bodies of water and nearby wells is precisely the opposite of the annual heat consumption. This problem is addressed by achieving extremely high water flow rates through heat pumps in winter, since only temperature differences of 1°C to 4°C are usable in winter, as cooling the water below 3°C is rarely, if ever, possible for both ecological and thermodynamic reasons. However, the significant disadvantages of low COPs and extremely high, and therefore ecologically problematic, water flow rates remain.

[0008] The Bad Reichenhall municipal utility company has partially mitigated these disadvantages by using a groundwater heat pump supplied with groundwater from the Saalach River. At a depth of approximately 40 meters, about 50 liters of water per second are extracted from the groundwater stream and, after cooling, reintroduced about 100 meters downstream via an injection well. At the point of extraction, the water maintains a temperature of approximately 10°C to 12°C year-round, thus partially smoothing out the temperature fluctuations of the Saalach. When it is reintroduced, the temperature is between 4°C and 6°C. The heat extracted in this process can be used by the heat pump to raise the temperature to approximately 85°C. This is precisely the temperature that is intended to reach the district heating customers.

[0009] This problem will be briefly illustrated using the average water temperatures compiled in Table 1 for the Treene River in the Schleswig-Holstein village of Oeversee and for wells located near the riverbank over the course of a year (based on data from 1970 to 2008 interpolated with a temperature increase of 0.5 °C per decade). Table 1 shows the average temperatures of the Treene (A) and the water temperature of the wells near the riverbank (B) over the course of a year. It is clearly evident that the course of the seasonal temperature fluctuations in the wells near the riverbank (B) largely corresponds to the course of the seasonal temperature fluctuations of the river (A):

[0010] If the temperature drops from 5 °C to 3 °C in February, per m² 3Only 0.13 times the amount of heat energy that can be extracted in February is higher than in July when the temperature drops from 18 °C to 3 °C. This results in a discrepancy factor of 1 / 0.13 = 7.7. Furthermore, the municipal heat demand in February is at least five times higher than in July. Therefore, there is an extreme winter problem, both in terms of the potential heat extraction (with a total discrepancy factor of 7.7 x 5 = 38.5) and the low COP in winter.

[0011] The object of the invention is therefore to create a device for utilizing hydrothermal energy that enables a uniform water withdrawal throughout the year and the operation of a heat pump with the highest possible "Coefficient of Performance" (COP).

[0012] This problem is solved by the device for utilizing hydrothermal energy with the features of claim 1. The dependent claims describe advantageous embodiments of the invention.

[0013] The basic idea of ​​the invention lies in particular in realizing the water extraction from bank filtration wells in such a way that, purely in terms of heat, an approximately 6-month extraction delay is achieved, so that the temperatures of the summer warm water from the body of water only arrive in the well at the beginning of winter with as little heat loss as possible, and at the same time the entire groundwater-conducting soil area including this water between the body of water and the wells exhibits the elevated summer temperatures at this time and persists until the end of winter.

[0014] The design according to the invention leads to a course of seasonal temperature fluctuations of the well water that is opposite to the course of seasonal temperature fluctuations of the flowing water - as shown in Table 2.

[0015] In particular, Table 2 shows the average temperatures of the Treene (A) and the water temperature of the wells near the bank (B) as well as the water temperatures in wells located approximately 400 m from the bank of the Treene (C) over the course of the year: Table 2

[0016] It is clearly evident that the course of seasonal temperature fluctuations in the wells located 400 m from the banks of the Treene River is delayed by approximately 6 months compared to the seasonal temperature fluctuations of the Treene itself, thus allowing for the advantageous use of a high temperature level for operating a heat pump throughout the winter. This 6-month temperature offset between C and A only occurs with the embodiments according to the invention.

[0017] According to the invention, a device for utilizing hydrothermal energy is proposed, comprising at least one first well arranged adjacent to a body of water and equipped for pumping bank filtrate, and a heat pump connected to the at least one first well by means of at least one source supply line, which is connected to at least one consumer by means of at least one consumer supply line and at least one consumer return line, wherein the at least one first well is arranged at a distance from the body of water such that the course of the seasonal temperature fluctuations of the bank filtrate pumped from the at least one first well is offset from the course of the seasonal temperature fluctuations of the body of water by at least three and at most nine months, wherein at least one second well arranged adjacent to the body of water is provided, which is equipped for pumping bank filtrate.wherein the at least second well is arranged at a distance from the water body such that the course of the seasonal temperature fluctuations of the bank filtrate extracted from the at least one second well corresponds to the course of the seasonal temperature fluctuations of the water body, wherein the at least one second well is connected to the heat pump by means of at least one further source supply line, wherein the consumer return line has a consumer return loop arranged in a near-shore area of ​​the water body, which transfers heat to the bank filtrate extracted from the at least one first well, and wherein the heat pump is connected to a source return line that supplies water to the water body.

[0018] According to a first preferred embodiment of the invention, the course of the seasonal temperature fluctuations of the bank filtrate extracted from at least one first well is offset from the course of the seasonal temperature fluctuations of the water body by four to eight months, particularly preferably five to seven months, and most preferably six months, specifically six months ± two weeks. This embodiment ensures that the temperatures of the warm summer water from the water body are only available in the wells during the winter with minimal heat loss and can then be used there.

[0019] The first well, at least one of which, primarily extracts bank filtrate, is hereinafter also referred to as a bank filtration well. In Germany, approximately 20 million people receive their drinking water from bank filtration wells along rivers, such as the Rhine, Havel, and Spree, from which the water is essentially drawn in reverse. As it passes through the sandy / gravelly soil layer between the watercourse and the well, the water is filtered free of particles, and any remaining contaminants are biologically / chemically removed. These specific requirements for bank filtration wells for the supply of drinking water, as well as the much smaller quantities of drinking water involved, contrast directly with the requirements of the invention for hot water in winter, where particles and contaminants are not a concern.

[0020] Furthermore, the device according to the invention is designed such that the heat pump is connected to a spring return line that supplies water to the body of water, particularly in the case of a flowing body of water downstream of at least one first well, wherein this water is preferably cooled to 4 °C throughout the year. This open circuit ensures the most natural and environmentally friendly use of the water and is to be considered a very positive, gentle cooling effect from both an ecological and climatic perspective.

[0021] Furthermore, the heat pump is connected to the consumer on its output side via a consumer return line, so that a closed circuit with the consumer supply line is created - as with all heat networks.

[0022] The aim of the present invention is to ensure that at the beginning of the sharply increasing heat demand in autumn in temperate climate zones, sufficient warm water arrives in the bank filtration wells for the required heat generation. The background is that: 1. The annual heating requirements can fluctuate quite significantly from year to year due to weather conditions, and 2. The water levels and corresponding groundwater levels (and thus the total heat storage volume) can fluctuate from year to year, and 3. The annual temperature profiles of the waters can fluctuate by up to + / - 4 °C per month due to weather conditions.

[0023] Therefore, water extraction from at least one primary well should be regulated accordingly. Consequently, the possibility of decoupling this regulation from the summer / early autumn extraction for heat production during these periods must be created. For this purpose, dedicated test wells, hereinafter also referred to as at least one secondary well, are preferably constructed between the bank filtration wells and the water body. These wells are used to record the temperature profiles and the elevations of the actual, current groundwater layers. From this data, it can then be directly determined whether the extraction volumes from the wells need to be increased compared to the requirements for heat generation (reductions are irrelevant). No heat is extracted from these increased extraction volumes (which are set manually or automatically using a suitable algorithm). Instead, this heat is discharged directly back into the water body.

[0024] This ensures that sufficient warm water for the required heat generation in the bank filtration wells arrives at the beginning of the sharply increasing heat demand in temperate climate zones in autumn.

[0025] Another goal is to ensure that the supply of hot water continues throughout the winter until the demand for heat drops sharply again in the spring.

[0026] The background is, in turn: 1. The annual heating requirements can fluctuate quite significantly from year to year due to weather conditions, and 2. The water levels and corresponding groundwater levels (and thus the total heat storage volume) can fluctuate from year to year, and 3. The annual temperature profiles of the waters can fluctuate by up to + / - 4 °C per month due to weather conditions.

[0027] Therefore, the consumer return line is designed to include a consumer return loop located near the bank of the water body. This loop transfers heat to the bank filtrate extracted from at least one initial well. In other words, the consumer return line (which otherwise terminates directly from the district heating network back at the heat pump) features a consumer return loop located near the bank of the water body. This loop transfers heat to the groundwater flow towards the bank filtration wells. Specifically, the consumer return loop is an uninsulated pipe laid along the water body (at most the length of the bank filtration well row) in the groundwater zone. This pipe is supplied with heat from the return flow of the district heating network. This return flow has a temperature of approximately 45–50 °C, and up to 20 °C of heat can be extracted from it.This additional heat is continuously absorbed by the groundwater flowing from the shore towards the bank filtration well.

[0028] This process step is preferably activated in the months of July to November. This ensures that elevated target temperatures can be reached in the return loop area until November (and not just until the end of August) (e.g., 22 °C instead of 7.7–17 °C) and that the heat flows from the water body towards the bank filtration well, thus ensuring that sufficient heat reaches the bank filtration well even at the end of the winter period (March and April).

[0029] Alternatively and / or additionally, this extra heating can also be achieved using solar collectors.

[0030] This additional heating results in the temperature profiles in the wells (C) shown in Table 3, in the form of a desired increase and extension of the heat storage capacity (compared to the values ​​from Table 2):

[0031] Although relatively cold water is drawn from the wells in summer—namely, water from the previous winter—the COP would be correspondingly low. However, this water must be drawn to ensure sufficient warm water reaches the wells in winter. To counteract this disadvantage, the following decoupling is proposed: In addition to at least one primary well, at least one secondary well will be constructed close to the watercourse to cover summer heating needs. During the entire period in which the water in this secondary well is warmer than in the more distant primary well (see Table 3: months May to October), water for the heat pump will be drawn from this secondary well. Completely independently of this, the precise amount of water required to guarantee hot water for the heat pumps at the beginning of the cold season in November will then be drawn from the more distant primary wells.

[0032] According to the invention, at least one second well arranged adjacent to the water body, which is equipped for pumping bank filtrate, is provided, wherein the at least second well is arranged at a distance from the water body in such a way that the course of the seasonal temperature fluctuations of the bank filtrate pumped from the at least one second well corresponds to the course of the seasonal temperature fluctuations of the water body, wherein the at least one second well is connected to the heat pump by means of at least one further source supply line.

[0033] In this context, a control system is also provided for supplying water to the heat pump from at least one first well and at least one second well. Specifically, a control system is provided for supplying water to the heat pump from at least one first well and at least one second well, which communicates with a sensor that measures the water temperature in each well. The control system is configured to supply the water with the higher temperature to the heat pump. The control system is specifically designed to ensure that the body of water from which water is extracted via the (shore filtration) wells and into which the cooled water flows back does not suffer any ecological damage as a result of these measures. On the contrary, the body of water should benefit ecologically from the measure through an improvement in the oxygen balance and also climatically insofar as greenhouse gas emissions from this body of water are reduced.

[0034] To achieve this goal, measuring stations are preferably installed in or on the water body for the preferably continuous recording of water volumes, temperatures, and oxygen content. In addition, online oxygen measurement of the water drawn from the wells is preferably carried out. If the flow rates and oxygen concentrations in the water body, as well as the oxygen concentrations in the well water, fall below relevant target values, oxygen enrichment of the cooled water flowing back into the water body is most preferably carried out automatically.

[0035] As mentioned above, preferably at least one third well ("test well") is provided between the body of water and the at least one first well. This test well is designed to determine the temperature of the water flowing from the body of water to the first well, with the flow rate of water extracted from the second well being determined by the water temperature measured in the third well. During operation of the device, this at least one third well serves the function of ensuring that, depending on the water temperature measured in this third well, more water is drawn from the first well during the summer months so that sufficient warm water reaches the first well at the beginning of winter.

[0036] Ultimately, the body of water in question is primarily a flowing body of water.

[0037] The advantage of the invention lies in the fact that, in temperate climates, at the beginning of the sharply rising heating demand in autumn, sufficiently warm water already arrives at the bank filtration wells, and the inflow of this warm water continues until the heating demand drops sharply again in spring. This also allows relatively warm water to be used by the heat pump in summer. Finally, the body of water, for example, a stream, a river, a gravel pit, a lake, etc., from which the water is extracted by means of the bank filtration wells and into which the cooled water flows back, does not suffer any ecological damage from this measure; on the contrary, it benefits ecologically from the measure due to an improvement in the oxygen balance and also climatically insofar as greenhouse gas emissions from this body of water are reduced.

[0038] The invention will be explained in more detail below with reference to a particularly preferred embodiment illustrated in the accompanying drawings. The drawings show: Fig. 1 a first preferred embodiment according to the invention; Fig. 2 a second particularly preferred embodiment according to the invention; and Fig. 3 a third most preferred embodiment according to the invention.

[0039] Fig. Figure 1 shows the schematic structure of a first preferred embodiment according to the invention. In particular, it shows Fig. 1 This configuration is a particularly preferred device for utilizing hydrothermal energy, comprising a plurality of first wells 20 arranged parallel to a flowing body of water 10 and designed to extract water from the flowing body of water 10, and a heat pump 30 connected to the plurality of first wells 20 by means of at least one source supply line QVL, which is connected to at least one consumer by means of at least one consumer supply line VVL and one consumer return line VRL. According to the invention, the wells 20 are arranged in an area away from the flowing body of water in which the course of the seasonal temperature fluctuations of the well water is offset from the course of the seasonal temperature fluctuations of the water by at least three and at most nine months.

[0040] The total winter heating demand necessitates a specific heat storage volume at the bank filtration wells, based on an average winter temperature and the target cooling value. Given the known thickness of the aquifer, this determines the required surface area (and thus heat storage volume) between the water body and the bank filtration wells.

[0041] For example, the winter heating demand from mid-November to mid-April is 10,000 MWh. Wärme The well water temperature, as well as the entire groundwater-bearing layer between the body of water and the wells, averages 17 °C at this time. Cooling to 4 °C with a heat pump requires approximately 1.35 × (17 - 4) = 17.6 kWh. Wärme / m 3 Well water produced.

[0042] The average thickness of the groundwater-bearing layer is 3 m and the average heat capacity of this water-gravel layer is 0.68 kWh.Wärme / (m 3 × °C).

[0043] This results in the required area between the body of water and the wells being 10,000,000 / (3 × 0.68 × 17.6) = 245,000 m² 2 The area should be 24.5 hectares. With a chosen distance of 400 m between the well and the body of water, the required length of the well row is approximately 612 m.

[0044] This means that to produce 10,000 MWh Wärme (the heat difference between the VVL and VRL multiplied by the winter water volumes) exactly as much water has been taken from the 10 wells in winter until the heat capacity of the 24.5 hectares is exhausted.

[0045] Furthermore, it can be seen that the heat pump is also connected to a source return line QRL, which returns heat-depleted water (usually 4 °C all year round) downstream of well 20 into the flowing water 10.

[0046] Fig. Figure 2 shows the schematic structure of a second, particularly preferred embodiment according to the invention. This second embodiment extends the one described in Figure 2. Fig. The structure shown in 1 essentially comprises a consumer return line VRL leading from the consumer back to the heat pump 30, which has a consumer return loop VRLS arranged in a near-shore area of ​​the flowing water 10, onto which the bank filtrate pumped from at least one first well transfers heat.

[0047] Specifically, the consumer return loop (VRLS) is an uninsulated pipe laid along watercourse 10 (up to 600 m) in the groundwater zone, which is supplied with heat from the return flow of the district heating network. This return flow has a temperature of approximately 45–50 °C, from which up to 20 °C of heat can be extracted. This additional heat is continuously absorbed by the groundwater flowing from the bank towards bank filtration well 20.

[0048] This process step is preferably activated between July and November, as described above. This ensures that higher target temperatures (e.g., 22 °C instead of 17 °C) can be reached downstream of the consumer return loop until November (and not just until the end of August), thus guaranteeing sufficient heat in the wells even at the end of winter.

[0049] Additionally shows Fig. 2. Essentially, a plurality of third wells (“test wells”) 40 are located between the bank filtration wells 20 and the water body 10. These wells are used to record the temperature profiles and elevations of the actual current groundwater layers. From this data, it can be directly determined whether the extraction rates from the wells 20 need to be increased compared to the heat generation requirements (reductions are irrelevant). No heat is extracted from these increased extraction rates (which are set manually or automatically using a corresponding algorithm); they are simply discharged back into the water body via a bypass BP.

[0050] This ensures that sufficient warm water for the required heat generation in the bank filtration wells 20 arrives at the beginning of the heat demand, which increases sharply in autumn in temperate climate zones.

[0051] Finally, it shows Fig. 3 the schematic structure of a third particularly preferred embodiment according to the invention, which has the schematic structure consisting of Fig. 2 extended by a plurality of wells 20' arranged along the watercourse 10, designed for the extraction of water from the groundwater accompanying stream of the watercourse 10, which are arranged in an area much closer to the watercourse than the wells 20, in which the course of the seasonal temperature fluctuations of the groundwater accompanying stream corresponds to the course of the seasonal temperature fluctuations of the groundwater accompanying stream, wherein the group of wells 20' is connected to the heat pump 30 by means of at least one further source supply line QVL'.

[0052] In addition to the majority of first wells 20, the majority of second wells 20' are located close to the banks of the watercourse 10 and serve to meet the summer heating demand. Throughout the entire period in which the water in these second wells 20' is warmer than in the more distant wells 20 (see Table 3: months May to October), water for the heat pump 30 is drawn from these second wells 20'. Completely independently of this, the exact amount of water required to guarantee hot water for the heat pump 30 at the beginning of the cold period in November is then drawn from the more distant bank filtration wells 20.

Claims

[1] Device for utilizing hydrothermal energy with - at least one first well (20) located adjacent to a body of water (10) and designed to pump bank filtrate and - a heat pump (30) connected to the at least one first well (20) by means of at least one source supply line (QVL), which is connected to at least one consumer by means of at least one consumer supply line (VVL) and at least one consumer return line (VRL), wherein - the at least one first well (20) is arranged at such a distance from the water body (10) that the course of the seasonal temperature fluctuations of the bank filtrate extracted from the at least one first well (20) is delayed by at least three and at most nine months from the course of the seasonal temperature fluctuations of the water body, - at least one second well (20') is provided adjacent to the water body (10), which is designed for pumping bank filtrate, wherein the at least second well (20') is arranged at a distance from the water body (10) such that the course of the seasonal temperature fluctuations of the bank filtrate pumped from the at least one second well (20) corresponds to the course of the seasonal temperature fluctuations of the water body (10), wherein the at least one second well (20') is connected to the heat pump (30) by means of at least one further source supply line (QVL'), - the consumer return line (VRL) has a consumer return loop (VRLS) arranged in a near-shore area of ​​the water body (10), which transfers heat to the bank filtrate extracted from the at least one first well (20), and - the heat pump (30) is connected to a source return line (QRL) that supplies water to the body of water (10). [2] Device according to claim 1, characterized by , that the course of the seasonal temperature fluctuations of the bank filtrate extracted from the at least one first well (20) is delayed by 6 months from the course of the seasonal temperature fluctuations of the water body. [3] Device according to claim 1, characterized by a control system supplying water from at least one first well (20) and from at least one second well (20') to the heat pump (30), which communicates with a sensor in each of the wells (20, 20') that detects the water temperature, wherein the control system is configured to supply the water with the higher water temperature to the heat pump (30). [4] Device according to any one of the preceding claims, characterized byat least one third well (40) arranged between the water body (10) and the at least one first well (20), which is equipped to determine the temperature of the water flowing from the water body (10) to the first well (20), wherein the delivery rate of the water extracted from the second well (40) is determined by the water temperature measured in the third well (40). [5] Device according to one of the claims, characterized by , that the body of water (10) is a flowing body of water.

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