Patent Application
20180112930
The invention relates to an energy storage device, a power plant with such an energy storage device, and a method for operating the same.
Due to the increasingly scarce stocks of fossil fuels, the use of renewable energy sources has been greatly expanded in recent years. An increase in the use of renewable energy sources is also predicted for the coming decades, since, in addition to rising raw material prices, which will make the use of fossil fuels less economical, the negative effects on the global climate connected with the accumulation of carbon dioxide in the atmosphere is also being considered in energy policy.
Various renewable energy sources are known from the general state of the art, including, for example, the use of solar radiation, wind power, or biomass. However, the first two sources mentioned in particular are associated with the known drawback that their use depends on external factors, such as available solar radiation or available wind, but such factors are not correlated with actual energy consumption. In order to remedy this situation, several possibilities are known; on the one hand, rapidly activatable power plants, which are typically based on fossil fuels, are kept available, which power plants are able to compensate for the emerging supply gap in the short term, and, on the other hand, efforts are being undertaken to create efficient energy storage that are able to temporarily store energy from renewable sources electrically or mechanically and, if necessary, are able to be introduced into a power grid.
An example of the mechanical storage of energy is provided in DE 10 2011 050 032 A1. For the generation of electricity in wind power plants and pump storage plants, the combination of such plants is proposed in such a manner that a water storage tank is installed in the interior of a tower of one or several wind power plants, which tank serves as an upper water reservoir of the pump storage plant.
DE 2 926 610 A1 discloses a storage device for providing the input heat energy at a low temperature level for heat pump systems, which absorb this energy and release it again at a higher temperature level, whereas a water basin is designed in such a manner that, through wall sloping and corresponding surface area and reinforcement, its water content is able to freeze without damaging the basin, and that a heat exchanger system located on the basin floor or embedded into the basin floor enables the cooling and freezing heat of such basin to be supplied to the cold side of a heat pump.
Furthermore, DE 10 2010 037 474 A1 discloses a storage tank device for an energy storage device system, comprising at least one storage tank and at least one first heat exchanger medium, whereas the storage tank features a housing containing a storage medium and at least one first heat exchanger arrangement in contact with the storage medium, whereas the at least first heat exchanger arrangement features a first heat transfer medium. Within the housing, at least one second heat exchanger arrangement is arranged with a second heat exchanger medium, whereas the second heat exchanger medium is essentially gaseous.
Thus, there is a need in the state of the art for an energy storage device that can easily form a renewable energy generation plant and that, in particular, can also be supplemented by a pump storage power plant.
Therefore, it is a task of the invention to provide an energy storage device that can work in combination with renewable energy sources and can improve the overall yield of such a plant. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
This task is solved by the characteristics of the embodiments described herein, wherein such embodiments can be combined with each other in a technologically sensible manner. The description, in particular in connection with the drawing, further characterizes and specifies the invention.
In accordance with the invention, an energy storage device is provided, which features a heat exchanger that is arranged in a floating manner on a lower basin formed as a lake and preferably able to be filled with water via a first supply line, whereas, via a second supply line, water can be supplied from the lower basin and, via a third supply line, coolant of a heat pump penetrating the heat exchanger can be supplied in separate circuits, such that energy can be extracted from the lower basin while freezing of the water of the lower basin or in the form of sensible heat from the water of the lower basin, and can be passed on to a consumer for heat dissipation and/or for cold dissipation.
Accordingly, the energy storage device is provided on the surface of a lake, which can be designed, for example, as a lower basin of a pump storage unit. Thus, the lower basin is provided with an additional possibility of energy extraction, which is utilized in the form of latent heat. By means of ice formation in the lower basin, the latent heat can be utilized and re-dissipated via the heat exchanger, for example for heating buildings at a consumer's premises. In addition, the sensible heat present in the water of the lake can also be extracted from the lower basin. For this purpose, the lake can preferably be filled with water without a natural inlet and via a first supply, such that solar radiation causes an increase in temperature of the water in the lake. The energy is extracted by means of a heat pump, which is preferably supplied with electrical energy from an energy source that is renewable or carbon dioxide-neutral. In particular, the heat pump can also be fed by a generator of the pump storage unit. Thawing typically occurs based on the prevailing environmental conditions, such as solar radiation or temperature of the atmosphere. In other embodiments, it may also be provided that thawing of the ice is effected through the utilization of the cold in the ice, for example for air conditioning during the spring or summer. In accordance with the invention, the actual heat accumulator is the lower basin. With this, the formation of ice is a possibility for the utilization of the latent heat arising from the heat accumulator formed as a lower basin.
The energy storage device features a wide range of possible applications and operating modes, such that, depending on the ambient temperature or the solar radiation that influences the energy that can be extracted as sensible heat arising from the lower basin, and depending on the energy demand according to the season or projected for a consumer, the energy storage device is either filled or emptied, whereas whether sensible or latent heat is to be supplied to the consumer via the heat pump can be selected at the time of extraction. By choosing the option when extracting energy, an adjustment to the location and demand conditions can be created.
The operation of the energy storage device in the seasonal cycle preferably takes place in such a manner that, during the energy input by solar radiation (that is, in northern latitudes, typically from spring to autumn), a temperature spread takes place. This reduces the radiating power of the surface of the lower basin by cooling the water located therein. Herein, the temperature spread relative to the ambient temperature is approximately in the range from 5° C. to 10° C. A cooling phase of the water in the lower basin to a temperature of approximately 0.5° C. commences, in order to enable an ice-free transition phase at the end of autumn (i.e., when the heating by solar radiation is abating). During the winter time, the energy is extracted through freezing on the surface of the lower basin. With this, continuous heat generation can be achieved through a sufficiently large selected volume of the ice due to the high energy content for the crystallization of water to ice. During the spring months until the early summer, the ice continues to melt on the heat exchanger with a simultaneous reduction in energy extraction, and the water temperature is further increased through solar radiation. An important point is that, in certain weather conditions, the ice layer formed after freezing can isolate the water surface of the lower basin relative to the atmosphere, such that its radiating power is thereby reduced.
Thus, in an advantageous manner, the concept described above can be used for the supply of households with heat energy through the supply of district heating, whereas approximately 40,000 m3 of ice must be provided for approximately 2000 to 4000 households, such that a natural lake would be adequately dimensioned as a lower basin.
In accordance with one embodiment of the invention, the heat exchanger is formed by pipes through which coolant flows.
Compared to surface elements, the provision of the heat exchanger as pipes has the advantage that, at the beginning of the formation of ice, the position of the crystallization point can be selected through the positioning of the cold water inlet. Accordingly, the initial freezing can be adjusted to the mechanical requirements of the heat exchanger in order to, for example, avoid or greatly reduce mechanical stresses compared to uncontrolled freezing.
In accordance with an additional embodiment of the invention, the pipes are arranged in the form of a ring spiral.
A ring spiral can be adjusted in shape and size to the shore line of the lower basin, which is formed as a natural lake, in order to make good use of the surface of the lower basin. With a circular or nearly circular lower basin, the ring spiral may be bounded by a circular outer line. However, elliptical or rectangular outer lines are also possible.
In accordance with an additional embodiment of the invention, radially arranged struts support the pipes arranged in the form of the ring spiral.
Such an approach enables a stable, yet material-saving arrangement of the ring spiral of the heat exchanger. This is also important, as the heat exchanger is arranged in a floating and mobile manner on the water surface, such that the heat exchanger is exposed to changing forces when changes in the water level occur, whereas the heat exchanger is to, for example, also withstand extreme situations such as flooding in the case of high water.
In accordance with an additional embodiment of the invention, the heat exchanger is surrounded by an outer wall that surrounds the heat exchanger along its outer circumference in the form of a vertical partition, such that a ring-shaped body is formed.
In order to separate the heat exchanger with the ice that may be present therein from the water of the lower basin, in accordance with the invention, it is not provided to form a closed volume, as is the case with known energy storage device systems based on the crystallization of water. In accordance with the invention, it is quite advantageous to leave the upper side and the lower side of the heat exchanger uncovered, as will be explained further below.
In accordance with an additional embodiment of the invention, the ring-shaped body has a diameter of approximately 50 m to 200 m, preferably approximately 100 m.
The dimensioning according to this embodiment enables the formation of several tens of thousands of cubic meters of ice, which would enable several thousand households to be supplied. The energy stored in this volume of ice corresponds to a heat output of some GWh. Here, the exact dimensioning can be selected or adjusted accordingly, taking into account the boundary conditions such as area needs, energy needs and available electrical power for operating the heat pump.
In accordance with an additional embodiment of the invention, the heat exchanger can be connected by means of an anchoring to a base of the lower basin.
With this, preferably in the center of the heat exchanger, an attachment option is provided along a post-like anchoring that is fixed to the base of the lower basin, whereas the heat exchanger is axially displaceable on the anchoring as a function of the water level in the lower basin. In addition to or in place of the post-like anchoring, the heat exchanger can be held at the base of the lower basin or in the area of the embankment through suitably prestressed tensioning cables, which are preferably attached to the aforementioned spokes or the outer wall.
The prestressing of the tensioning cables or the position of the heat exchanger on the post-like anchoring can also be adjustable by means of an external control.
In accordance with an additional embodiment of the invention, an ice layer forms in the heat exchanger radially from the inside to the outside, and, if applicable, subsequently increases in thickness.
The stability of the floating heat exchanger is increased through the radial formation of the ice layer from the inside to the outside, such that no or little complicated additional measures have to be taken for the balancing of the heat exchanger during the freezing on the lower basin. For this purpose, the cooling medium is supplied from the heat pump into the middle of the heat exchanger. Accordingly, the radial formation of the ice layer initially takes place, in order to obtain a closed ice layer. Subsequently, the thickness of the ice layer above and below the pipes of the heat exchanger is increased. With this, forming the ice layer approximately up to 1 m on each side of the pipes is provided. The ice layer serves, on the one hand, to provide a cold accumulator for cooling in the summer, in order to be able to carry out cold extraction. However, as already described above, the formation of ice is also an option for extracting heat from the water of the lower basin.
In accordance with an additional embodiment of the invention, the heat exchanger features an upper inlet, through which, during freezing, water can be introduced into the heat exchanger on the resulting ice layer, such that the ice layer is located below the water surface of the lower basin.
This approach makes it possible to, when the ice layer is present, provide an additional load, such that the heat exchanger sinks in the lower basin, and the ice layer comes to lie below the water surface of the lower basin. This ensures that, despite an ice layer, even when exposed to sunlight the water temperature in the lower basin is not kept unnecessarily low, but can in fact increase, since the solar radiation is absorbed in the area of the water surface as the temperature of the water near the surface increases, such that only a small energy input is introduced into the ice layer.
In accordance with an additional embodiment of the invention, an insulating layer is arranged between the ice layer and the cold water that is able to be supplied.
This results in a decoupling from the ice layer to the environment, which in particular reduces the heat exchange, such that the ice layer is retained for a longer period of time.
In accordance with an additional embodiment of the invention, an air cushion can be formed below the ice layer and on the side of the ice layer turned away from the water surface.
This results in a decoupling from the ice layer relative to the water of the lower basin, which in particular reduces the heat exchange, such that the ice layer is retained for a longer period of time.
In accordance with an additional embodiment of the invention, a multiple number of superimposed ice layers can be formed independently of one another.
As a result, a larger volume of the ice layer can be formed, whereas the individual ice layers can also serve individually as energy carriers, and can be used separately, depending on the requirements of the consumers for the supply of district heating. Furthermore, in a multi-layer system, the uppermost layer may constitute a type of “rapid freezing.” That is, a thin layer of ice can be rapidly formed in the uppermost layer. This can be formed approximately up to 10 cm on each side of the cooling pipe. Such layer can cover power peaks, but also be used to isolate the lower basin from the atmosphere. The idea with rapid freezing is that, for example, an ice layer is formed overnight in order to isolate the lower basin from the atmosphere, while water is pumped over the ice during the day in order to absorb solar radiation and melt the thin ice layer. Thus, if the energy balance is positive (for example, during the day), the rapid freezing is to serve as a solar collector and, if the energy balance is negative (for example, a cold night), the rapid freezing is to serve as insulation. As a result, “warm” water is quickly obtained in the collector, and a high degree of efficiency is obtained at the heat pump. At night, due to the insulation little energy is lost to the atmosphere.
In accordance with an additional embodiment of the invention, directly adjacent ice layers are separated by insulating layers.
This results in a decoupling of the ice layer relative to the environment, which in particular reduces the heat exchange, such that the ice layer is retained for a longer period of time.
In addition, a power plant comprising a lower basin of a pump storage power plant that can be filled with water is specified, whereas the lower basin is connected to a pump via a first supply line and to an upper reservoir via a supply line that passes through the pump storage power plant and can be connected to the first supply line, whereas the lower basin is provided with an energy storage device described above.
This approach ensures a significantly improved energy balance since, in addition to the storage in the pump storage plant, energy storage is also carried out in any event for the pump storage plant in the already existing lower basin. At this, the required power of the energy storage device is provided by the pump storage plant.
In accordance with one embodiment, the upper reservoir is part of a wind power plant, whereas the pump can be driven by means of electrical energy generated by the wind power plant, in order to pump water from the lower basin into the upper reservoir.
In particular, the alternating power of the wind power plant due to changing wind conditions can be compensated to a certain degree by the pump storage plant, such that the pump storage plant can deliver power during periods of low wind and can store energy in the case of excess power of the wind power plant.
This approach ensures a significantly improved energy balance since, in addition to the storage of the alternating power of the wind power plant in the pump storage plant, energy storage is also carried out in any event for the pump storage plant in the already existing basin. At this, the required power of the energy storage device is provided by the pump storage plant.
Finally, a method for operating such an energy storage device is indicated; with such method, the heat pump is controlled as a function of ambient temperature, solar radiation and water temperature, such that the ice layer is formed on the heat exchanger when no energy can be extracted from the water temperature of the lower basin.
In accordance with one embodiment of the method, the lowering of the ice layer through water load can additionally be carried out, in order to protect the ice layer from solar radiation.
By controlling the water load via the upper supply line, the effect of solar radiation on the ice layer can be reduced. As a result, the solar radiation can be absorbed by the water, since, for the most part, ice reflects the solar radiation. As a result, the irradiated energy quantity in the lower basin increases considerably compared to a situation with an ice layer floating on it.
In accordance with an additional embodiment of the method, the energy storage device may feature a multi-layer structure, whereas the layer closest to the water surface is initially used to form an ice layer, which is preferably thin.
Accordingly, in a multi-layer system, the uppermost layer may constitute a type of “rapid freezing.” That is, a thin layer of ice can be rapidly formed in the uppermost layer. This can be formed approximately up to 10 cm on each side of the cooling pipe. Such layer can cover power peaks, but also be used to isolate the lower basin from the atmosphere. The idea with rapid freezing is that, for example, an ice layer is formed overnight in order to isolate the lower basin from the atmosphere, while water is pumped over the ice during the day in order to absorb solar radiation and melt the thin ice layer. Thus, if the energy balance is positive (for example, during the day), the rapid freezing is to serve as a solar collector and, if the energy balance is negative (for example, a cold night), the rapid freezing is to serve as insulation. As a result, “warm” water is quickly obtained in the collector, and a high degree of efficiency is obtained at the heat pump. At night, due to the insulation little energy is lost to the atmosphere.
Some embodiments are explained in more detail below on the basis of drawings. The following is shown:
In the figures, identical or functionally equivalent components are provided with the same reference sign.
Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.
In
Furthermore, the pump storage power plant KR features a generator GE, which is connected to the supply line LT and is formed in such a manner that water, which is fed from the upper reservoir OR via the supply line LT through the generator GE into a lower basin UB, can be converted into electrical power. In the opposite direction, water can be pumped from the lower basin UG to the upper reservoir via a first supply line ZU1 and a pump PU. The generator GE is connected to a power grid SN, such that the generated electrical energy can be fed.
Furthermore, the pump storage power plant KR features an ice layer EI in the lower basin UB, which, as will be explained in more detail below, is arranged on the surface of the lower basin UB filled with water WA, as indicated by the arrow PF in
In other embodiments, the lower basin UB can also be realized without a pump storage power plant KR; that is, for example, as a lake or generally as surface water.
A coolant for forming the ice layer EI can also be supplied via a third supply line ZU3 through the heat pump WP to a heat exchanger WTA arranged in the lower basin UB. Through the extraction of sensible heat from the water WA of the lower basin UB or through the extraction of latent heat from the ice layer EI in the lower basin UB, the heat pump WP generates heat that can be supplied to a multiple number of consumers VR in the form of district heating FW.
The heat pump WP requires electrical power, which can be provided, for example, by the generator GE. The heat pump WP is preferably located within the pump storage power plant KR or is arranged immediately adjacent thereto. The pump PU is advantageously supplied with the electrical power emitted by the wind power plants WKA.
The lower basin UB, together with the ice layer EI along with the water WA present in the lower basin UB, forms, together with the heat pump WP, an energy storage device EN.
The lower basin UB forms a component of the pump storage power plant KR via the first supply line ZU1. Via the first supply line ZU1, water WA can thus be supplied to the lower basin UB or extracted from the lower basin UB, in order to be conducted via the pump PU into the upper reservoir OR. Furthermore, water WA of the lower basin UB is supplied via the second supply line ZU2 to the heat pump WP. The supply is indicated in
In a separately operating circuit of the heat pump WP, cooling liquid is supplied to the heat exchanger WTA via the third supply line ZU3. Here, the cooling liquid reaches the heat exchanger WTA via the supply line marked with the reference sign ZU3-H; in
A possible embodiment of the heat exchanger WTA will be described below with reference to
In
The embodiment of the heat exchanger WTA shown in
The upper supply line ZL is arranged above the ring spiral RS. With this, the outer wall AW is designed in such a manner that the ring spiral RS is completely covered with respect to its height, such that individual sub-areas, which are also components of the heat exchanger WTA, are provided above the ring spiral RS and below the ring spiral RS. In the sub-area located below the ring spiral RS, air can be directed into the heat exchanger WTA via an air supply LZ, which will be explained below.
In order to enable a floating arrangement of the heat exchanger WTA in the lower basin UB, a post-like anchoring (not shown in
The function of the heat exchanger WTA is explained in more detail below with reference to a first example.
The concept presented in
However, the embodiments explained in connection with
The operation of the energy storage device EN in the seasonal cycle takes place in such a manner that, during the energy input by solar radiation (that is, in northern latitudes, typically from spring to autumn), a temperature spread takes place. This reduces the radiating power of the surface of the lower basin UB by cooling the water WA contained therein through the heat pump WP. The temperature spread relative to the ambient temperature of the ambient air UL is approximately in the range from 5° C. to 10° C.
A cooling phase of the water WA in the lower basin UB to a temperature of approximately 0.5° C. commences, in order to enable an ice-free transition phase at the end of autumn (i.e., when the heating by solar radiation is abating).
During the winter time, the energy is extracted through freezing on the surface of the lower basin UB; that is, via the ice layer EI in the heat exchanger WTA. At this, continuous heat generation can be achieved via the heat exchanger WTA with the heat pump WP through a sufficiently large selected volume of the ice layer EI due to the high energy content for the crystallization of water WA to ice in the ice layer E.
During the spring months until the early summer, the ice of the ice layer EI continues to melt on the WTA heat exchanger with a simultaneous reduction in energy extraction, and the water temperature of the water WA in the lower basin UB is increased through solar radiation.
Thus, in an advantageous manner, the concept described above can be used for the supply of households with heat energy through the supply of district heating, whereas approximately 40,000 m3 of ice must be provided for approximately 2000 to 4000 households, such that a natural lake would be adequately dimensioned as a lower basin UB.
The existing ice of the ice layer EI can also be used for cooling at the premises of the consumer VR during times of high ambient temperatures.
The characteristics described above and the characteristics that are indicated in the claims and can be extracted from the figures can be advantageously realized both individually and in various combinations. The invention is not limited to the described embodiments, but can be modified in many ways within the scope of the skilled art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 104 909.0 | Mar 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/056808 | 3/29/2016 | WO | 00 |
