DE102011106040A1 - pumped storage power plant - Google Patents

Abstract

Storage power plants for electrical energy nowadays either require a very large space with a low level of efficiency (with gas-based storage systems) or a height difference that can only rarely be realized in the landscape (with water-based storage systems). The invention is a combination of liquid-based energy generation and a volume of gas which efficiently stores energy even when there is no difference in height. This has the two advantages that the height difference is no longer required and the losses in relation to pure gas-based storage systems are low due to the relatively low gas expansion and the buffering of thermal energy in the liquid during operation. In addition, this construction can be used as a heat store to B. to use stored heat in summer for building heating in winter or to temporarily store process heat all year round. The design is also suitable for separating the power grid and consumers, combined with short-term buffering in the event of fluctuations in supply.

Description

Pumped storage power plants are usually used for intermediate storage of electrical energy and take in view of the increasing importance of renewable energy sources, such as wind and sun, which produce discontinuous energy, an increasing importance to ensure a continuous power supply.

Previous concepts are often based on water, which is usually passed from a high-altitude reservoir in a lower reservoir to generate electricity and pumping in times of energy abundance water in the higher reservoir. Since suitable geological formations are limited in many regions available, further development of such storage is not easily possible. Alternatively, compressed-air underground reservoirs are shortlisted for energy storage. There is also the idea to raise a weight with water and recover the stored energy again using water turbines. Here are above all sealing and friction problems that prevent such a large scale construction. The achievable pressures by weights are also rather low. Advantage of such a design is the constant pressure, which is not possible with compressed air-based systems.

For gas storage there are several problems z. As possible losses due to leaks of the most natural memory, large losses in the compression and relaxation of the gas and due to the relatively low energy content of compressed air, a large volume or very high pressures. In addition, under underground storage possible effects of the occurring during operation pressure changes on the rock, which in the worst case have a destruction of the memory result.

It is now important to realize an energy storage, which is not necessarily dependent on large differences in height and has a high storage capacity with relatively little space and good efficiency.

• i) einen teilweise flüssigkeitsgefüllten ersten Hohlraum H₁ mit einem darin vorhandenen Gas unter einem Druck P₁ oder
• ii) einen zeitweise teilweise bis vollständig flüssigkeitsgefüllten ersten Hohlraum H₁ und einen damit verbundenem Hohlraum H₂ mit einem Gas unter einem Druck P₁ oder
• iii) eine Entnahmestelle unter einem Druck P₁ in einem Flüssigkeitsreservoir R₁.

This is achieved by claim 1

• i) a partially liquid-filled first cavity H ₁ with a gas present therein under a pressure P ₁ or
• ii) a temporarily partially completely filled liquid first cavity H ₁ and a cavity associated with H ₂ with a gas under a pressure P ₁ or
• iii) an extraction point under a pressure P ₁ in a liquid reservoir R ₁ .

Here, the first cavity H ₁ or H ₁ and H ₂ or the reservoir R _{1 is} connected to a further cavity H ₃ or in the case of a cavity H ₁ or H ₁ and H ₂ with a reservoir R ₂ , which under a lower pressure P ₂ is. Between the first cavity H ₁ or H ₁ and H ₂ or reservoir R ₁ under pressure P ₁ and the cavity H ₃ or reservoir R ₂ under the pressure P ₂ is a mechanically driven by the liquid and the pressure difference P ₁ > P ₂ Generator for electrical energy, as well as serving as a pressure generator component that may be identical to the electrical energy-generating component.

The basic principle of the storage power plant according to the invention with a liquid as a working medium is the utilization of a pressure difference in the absence or only slight difference in height of a system of two containers or a container and a reservoir. This pressure difference is much higher, d. H. at least 50% higher than achievable by any height difference of the system. This is achieved by means of a gas pressure on a liquid or with a container that is in the gas-filled state under a lower pressure than the ambient pressure, which is then given by the liquid at the same or almost the same height level. Especially with the latter method can be efficiently stored in deep waters without significant intervention in the landscape energy, in open waters without affecting the water level in the water.

In the first two embodiments is in a closed container, a liquid under high pressure, which is generated by a compressed gas. This compensates for a missing or too small height difference and thus also enables the ground-level construction of an energy store. But it can also be the combination of a reservoir, in which there is a high pressure in the depth, and a lying at the same or almost the same level cavity can be used. This can be z. B. realize in combination of underground cavities next to lakes or the sea, but also on or near the bottom of lakes or flooded opencast mines. In the latter case, a cavity in the reservoir is sunk and anchored in the absence of a natural or easily realizable cavity in the rock.

As a result, if a high pressure of several atmospheres is set or prevails, two significant advantages, namely a relatively small footprint with a large amount of storage and the avoidance of large energy losses. The latter is due to the compression of the gas, since the resulting heat entered into the liquid and during the relaxation can be returned to the gas, and in addition, the expansion or compression of the gas is relatively low. In addition, one can also work with other gases than with the air mentioned in claim 3. Here are gases that are not or only slightly warm by compression and cool only slightly during expansion. So occurs z. B. according to claim 4 when using hydrogen or helium due to the very low inversion temperature of these gases, the opposite effect, since the gas is heated during expansion. Thus, in a closed container which has no appreciable gas losses and a different gas or gas mixture used as air and energy losses are minimized by the compression of the gas. It is advantageous to take precautions in the second volume to z. B. dissolved in the water and released there released gas. This may be an additive when using water according to claim 2, which reduces the gas solubility. This is already the case with salt water, and accordingly a salt addition or the use of seawater as a working medium can be advantageous.

There are several possibilities for the technical realization. Thus, a system of two interconnected containers can be used, between which z. B. water pumped back and forth or used for energy production and storage. The lower pressure part can also be a lake, sea or ocean, watercourse or an open basin. Also, in a not completely filled with water tank compressed air can be introduced, so the compression does not happen by pumping in water, but by the introduction of compressed air. So this is necessary at least during commissioning, if you want to come to significant operating pressures because z. B. in a configuration with 50% water and 50% gas filling only an overpressure of 1 bar would be achieved if you simply pumped the water. However, putting the half-filled system under an initial pressure of 100 bar, this corresponds to an initial height difference of 1000 m. The pressure would then reduce to about 50 bar when the water was completely drained. In this case, the gas reservoir can also be located next to the water tank and connected to this via a pipe. This would facilitate maintenance and the use of special gases, since in such a case, the water, if a separating slide between the containers is present, can be drained without pressure loss. After the maintenance, the water is simply refilled. Then it is then charged again with the pressure of the gas. It is important for the operation of a large line cross-section to keep friction between the containers low.

Due to the relatively small expansion of the gas by a factor of two, the heating and cooling of the gas during operation is relatively low. For a better transfer of heat to the liquid, it can be sprayed on introduction, for example according to claim 8, or initiated in such a way that it passes into the reservoir in free fall and finely distributed by the gas. When discharging the liquid or small parts thereof can be sprayed most easily in the gas space to dissipate the heat efficiently. Here, the advantage of a liquid also comes to bear, as it has a relatively high heat capacity per volume and can thus prevent a strong heating or cooling of the gas during compression and expansion.

Another possibility is according to claim 9, the combination of the claimed energy storage with a heat storage. Here, when using well-insulated reservoirs, the liquid can be used to store heat energy, which can be used for summer cooling and winter heating. This is especially interesting in the vicinity of houses or industrial plants, less if the memory near the place of power generation, eg. B. is erected with wind power, since they are usually at a distance to possible heat consumers.

In principle, the method can be implemented in many locations and configurations. Thus, the pressure vessel may be installed above as well as above according to claim 5 underground, the pressure-poorer reservoir also and the arrangement to each other, next to, above or below each other. The pressure vessel is ideally realized as a ball or cylinder with hemispherical ends. However, it can also have any other shapes. Especially if it is installed underground in natural cavities or artificial tunnels, the supporting rock must be sealed only by a thinner outer wall.

In addition to a solution underground, a storage system under water makes sense according to claim 6. Here, the expansion volume must be built pressure-resistant and under lower pressure than the surrounding water. Is such a gas container, ideally via a pipe in connection with the atmosphere, in a sufficient depth, z. B. 500 m deep, it can be filled with deep water, which is then under a pressure of about 50 bar, with generators can gain power. The pumping of the memory causes a filling with gas or outside air, which is accomplished in the latter case via the line to the atmosphere. In this case, the memory can also lie in the neighboring reason, which prevents problems with the buoyancy and a complex backup.

Ideal for long-term use is a gas-tight and watertight seal of the pressure vessel. This can be done with many materials, such. B. with a film material on a supporting surface or by means of synthetic resins. The latter can z. B. with carbon fiber mats realize a pressure-resistant container, which is possibly outside surrounded with another supporting and protective material. The former solution requires a carrier, this can, for. B. a stud and / or a reinforced concrete shell and / or a metal or composite solution such as fiber-reinforced materials. But also metal containers can be used. In another possible solution, a water reservoir sealed at the bottom is provided with a traction-absorbing roof, which either covers the surface or, by means of intermediate supports, absorbs the weight of the roof or the tensile forces resulting from overpressure. From a safety point of view, however, at high pressures spherical or cylindrical or consisting of such elements containers, unless the pressures are not z. B. be caught in the rock or other carrier, preferable.

It is also useful for safety reasons in pressure vessels to install a safety valve at a suitable location, which allows the outflow of the gas in a safe for humans and the environment direction. This is usually an outflow vertically into the atmosphere.

The invention is useful in principle as an air-water system up to a pressure of about 830 bar. In addition, the density of air reaches the same or higher value than water, and the energy content of the storage becomes comparably high, i. H. the use of water is redundant apart from the use as a heat reservoir for the expansion and compression process. Nevertheless, even at such high pressures, the expansion losses of the gas are significant and water as the carrier at an advantage. Since currently such large pressures can not be safely implemented, the combination of liquid-gas pressure and liquid-pressure gas by the higher efficiency is advantageous over purely gas-powered storage solutions.

Drawing 1a presents possible embodiments. So here are two adjacent memory H ₁ with pressure P ₁ 101 and H ₃ with pressure P ₂ 102 to see which by means of a pipe 103 and a unit for power generation or pumping 104 connected to each other. In addition, a control valve can be installed in this unit, but this is also elsewhere on the line 103 possible. The container 101 is closed, the container 102 with an opening 105 designed.

Drawing 1b is analogous to an embodiment with two containers 101 and 102 underground. Drawing 2a shows a possibility of superimposed arrangement. Here is the pressure vessel H ₁ with pressure P ₂ 201 above the container H ₃ with pressure P ₂ 202 arranged, using one or more elements 204 Energy is gained or stored in H ₁ .

Another embodiment is the construction of the memory around each other as shown in drawing 2b. Here is z. B. to the memory H ₁ with pressure P. ₁ 211 a second shell 212 as memory H ₃ with pressure P _{2 placed} at a greater distance and the liquid between the interior and exterior via one or more elements 214 pumped back and forth. So here is z. For example, in a spherical shape, the inner sphere is designed with a radius of about 20 m, the outer with a radius of about 25 m, to achieve the same volume in both areas.

Analogous to drawing 1, a store can also have two containers under high pressure, which, as already stated, offer advantages in terms of maintenance work. Thus, in drawing 3a, the reservoir H ₁ with pressure P _{1 is} a pure gas reservoir, supplemented by a liquid reservoir H ₂ with pressure P ₁ 301 , the z. B. via a line 303 and one or more power generators or storage elements allow the liquid to flow or pump to a further reservoir H ₃ with pressure P ₂ .

An analogous version is in drawing 3b, but here with an open natural memory in the form of a lake 306 , designed.

The advantage of a closed system is the prevention of contamination of the water, eg. B. by aquatic plants, branches or other occurring in natural waters objects.

Also, both containers can in principle be closed or shaped differently as shown in drawing 4. So can container or memory H ₁ 401 have a high pressure P ₁ (eg 100 bar) and container H ₃ 402 a low P ₂ (eg 1 bar). When generating energy through the liquid via lines 403 and energy exchanger unit 404 the pressure in vessel H ₁ drops (eg to about 50 bar) and rises in vessel H ₃ (eg to about 2 bar). This facilitates the use of specialty gases that minimize the potential temperature change during expansion or compression. Furthermore, the gas may be separated from the liquid by an elastic membrane or a balloon or balloon-like container according to claim 7, z. B. the diffusion of gas into the liquid and thus to minimize pressure losses.

Also, a reservoir in a body of water, as shown by way of example in drawing 5, is possible. As a result, when realized in or on the lake bottom only this or, if floating, only an area in the water through the memory 502 influenced, the memory remains invisible in the landscape. The memory is in this example the deep water in reservoir R ₁ under pressure P ₁ , which via an energy exchanger 504 enters the container H ₃ with pressure P ₂ , which in this example via a line 507 connected to the atmosphere, but can also be operated without such a line. This is advantageous for. B. in lake-rich shallow areas or in the open sea, where often generates a lot of wind energy, which is ideally cached for times of low wind. Another way to realize a system according to drawing 5, is the integration with a standing in the water wind turbine. So z. B. designed around the base of the wind turbine, a corresponding container, which is used as needed as a memory. In this case, the air can either be introduced or removed from the container via the windmill mast or directed via a separate feed. Depending on the design of the container, it can also exert a stabilizing effect on the wind turbine construction. In addition, with such a construction relatively easy access to the turbine of the memory, which can be achieved ideally via the mast or the mast foundation, possible.

The reservoirs can be realized underground, above ground, in or partly in a body of water or even partly under ground.

Also according to claim 10 is a compact memory that is continuously filled by a pump that is powered by the mains, and continuously generates electricity through a generator as a buffer for voltage fluctuations and dirty power, as well as short supply fluctuations as an energy buffer, as well as power failure as a buffer until the operation of an emergency generator. Since the pressure in the tank can remain virtually constant during normal supply from the power grid, an energy-efficient decoupling of the power grids and short-term buffering is thus easily possible. Due to the short pipelines low friction losses of the system are possible here. Only the respective efficiencies of the pumps and turbine unit are essential to the overall efficiency of the system, other factors are almost negligible.

In principle, the energy store according to the invention can be realized with all liquids and gases which have no undesired reactions with one another or with the container and generator. So you can in principle achieve a higher storage density at the same volume when using heavy liquid metals such as gallium, mercury or alloys such as Galinstan. However, these metals are expensive, sometimes toxic and currently difficult to use economically in large quantities.

The examples mentioned are only a few of a variety of design options and can usually be combined with each other. Thus, the number and type of power generators and pumps are diverse, as well as the number of containers and reservoirs and their placement. Also, liquid and gas mixtures can be used instead of pure liquids and gases.

Claims (10)

Pumped storage power plant characterized by i) a partially liquid-filled first cavity H ₁ with a therein gas at a pressure P ₁ or ii) H ₂ with a gas under a pressure P _{1 is} a partly partially to completely liquid-filled first cavity H ₁ and a related materiel cavity or iii) an extraction point under a pressure P ₁ in a liquid reservoir R ₁ . Here, the first cavity H ₁ or H ₁ and H ₂ or the reservoir R _{1 is} connected to a further cavity H ₃ or in the case of a cavity H ₁ or H ₁ and H ₂ with a reservoir R ₂ , which under a lower pressure P ₂ is. Between the first cavity H ₁ or H ₁ and H ₂ or reservoir R ₁ under pressure P ₁ and the cavity H ₃ or reservoir R ₂ under the pressure P ₂ is a mechanically driven by the liquid and the pressure difference P ₁ > P ₂ Generator for electrical energy, as well as serving as a pressure generator component that may be identical to the electrical energy-generating component. Pumped storage power plant according to claim 1 characterized by the use of water as the liquid medium. Pumped storage power plant according to claim 1 characterized by the use of air as a gaseous medium. Pumped storage power plant according to claim 1 characterized by the use of hydrogen, helium or other gas with an inversion temperature <500 ° C as a gaseous medium. Pumped storage power plant according to at least one of the preceding claims characterized by the partial or complete realization underground. Pumped storage power plant according to at least one of the preceding claims characterized by the partial or complete realization under water. Pumped storage power plant according to at least one of the preceding claims characterized by the spatial separation of the gas from the liquid through a membrane or by a balloon-like container for the gas. Pumped storage power plant according to at least one of the preceding claims characterized by the rapid temperature compensation between liquid and gas by spraying the liquid in the gas space, the blowing of the gas into the liquid and / or by heat exchanger lines to the container walls and / or in the gas space. Pumped storage power plant according to at least one of the preceding claims characterized by the additional use as a heat storage to store excess heat for later use. Pumped storage power plant according to at least one of the preceding claims characterized by the use as a separator, buffer and / or uninterruptible power supply between a power grid and a consumer.

Images