WO2020125868A1

WO2020125868A1 - Method and device and system for stabilizing an electricity grid

Info

Publication number: WO2020125868A1
Application number: PCT/DE2019/101103
Authority: WO
Inventors: Peter Volkmer
Original assignee: Peter Volkmer
Priority date: 2018-12-17
Filing date: 2019-12-17
Publication date: 2020-06-25
Also published as: CN113424393A; DE112019006240A5

Abstract

The invention relates to a method, a device (1) and a system for stabilizing an electricity grid, wherein the grid is stabilized by equalizing the generation and consumption of electrical energy by withdrawing excess electrical energy from the electricity grid (DSN), converting same into a storable energy source and storing same, on the one hand, and reconverting the stored energy source and feeding said energy into the electricity grid (DSN), on the other hand. According to the invention, in the event of the electrical energy generated being greater than consumption, the energy is converted and stored in chemical form as at least one hydrocarbon, as a storable chemical energy source, using carbon dioxide (CO₂), formed in a preceding cycle by reconversion, wherein the at least one hydrocarbon is synthesized using the carbon dioxide (CO₂) and hydrogen (H₂) which is obtained by electrolysis from water (H₂O) using the electrical energy to be stored.

Description

Method and device and system for stabilizing a power grid

The invention relates to a method and a device for stabilizing a power grid, the stabilization by balancing the generation and consumption of electrical energy by removing excess electrical energy from the power grid, converting it into a storable energy carrier and storing it, and converting the stored energy carrier back into electricity and feeding into the power grid on the other hand. The invention also relates to a system for stabilizing a power network. A facility for the transmission and distribution of electrical energy is referred to as a power network.

With the energy turnaround, electrical power generation will be completely switched to generation from renewable energy sources without further emitting C0 ₂ . This electricity generation is volatile in terms of time of day, weather and season. There is currently a certain daily electricity consumption and a certain amount and generation capacity must be available for this.

Hourly or daily situations arise in which the generation of electricity from renewable energy sources cannot meet the demand (e.g. during dark drafts, wind drafts or technical disruptions in generation). There are also times when too much electrical energy is generated, so that generating plants have to be curtailed to reduce their output, which worsens the efficiency of the generating plants and may also result in compensation costs for electricity that is not generated.

In order to achieve a more stable supply, the consumption of intelligent power grids and intelligent consumer devices can also be adjusted according to the current power supply. But that is not enough to e.g. B. to bridge dark doldrums.

The physical storage z. B. in pumped storage plants is an efficient option, especially with storage lakes in Norway and the Alpine countries, but the suitable locations are only available to a limited extent. There are also possibilities for chemical storage of electrical energy in accumulators, also known as batteries. Implemented as large buffer storage units, however, they cannot solve the tasks at hand, since the storage volume required to stabilize the power grid cannot even be approximately achieved with them. You will find their suitable use at necessary short-term regulation in the power grid. For short-term storage, high-capacitance capacitors, also known as super-caps, are increasingly being used. These cannot even begin to meet the storage volume required for a fundamental stabilization of the power grid.

It is also planned to contribute to stability via high-performance power lines in Germany or with neighboring countries (e.g. NordLink with Norway) by exchanging renewable electricity. The exchange provides for the transfer of surpluses and the takeover of electricity to cover supply gaps in Germany. Such a system is very expensive due to cable lengths of up to 500 km and the real overall storage efficiency is only 50%.

The above-mentioned technical solutions are not sufficient, because in order to secure the stabilization of the electricity supply through storage to the required extent, forecasts assume a storage requirement of approx. 40% of the annual consumption, i.e. approx. 60 TWh, with a required peak generation capacity of 30 GW . Large-volume storage is therefore essential.

Therefore, preference is to be given to methods with which electrical energy can be stored in the form of chemical energy in large quantities. The starting point is the production of hydrogen as an energy source, but storage and transport are complex and involve risks. The specific energy density of hydrogen in comparison z. B. to methane is very low. The large hydrogen storage facilities required for this currently and in the future do not exist.

Processes that are based on the hydrogen obtained from electricity and synthesize methane or other methanol or other hydrocarbons using C0 ₂ using the Sabatier process, represent a sustainable, targeted solution for storing electrical current.

A method for storing electrical energy is known from the publication DE 10 2012 105 736 A1. The proposed solution is designed to store electricity from renewable energies in a chemical energy source using C0 ₂ from the exhaust gases of a lignite-fired power plant. Ultimately, however, this does not take place in connection with the stabilization of the power grid, but to reduce the specific CO ₂ emissions of the lignite-fired power plant. This procedure for Storage of electrical energy in a hydrocarbon using carbon dioxide formed in a technical system is characterized in that, in addition to the technical system, at least one hydrocarbon, in particular methane, is synthesized using carbon dioxide, water and electrical energy. Electrical energy is stored in chemical form with the hydrocarbon. But when it is burned in the process described, fossil CO ₂ is ultimately released, albeit less on the balance sheet. A disadvantage of this solution, however, is that the technical system as a C0 ₂ source for the function of the proposed method is absolutely necessary. The C0 ₂ is created in the technical system from the combustion of fossil fuels. Other noteworthy C0 ₂ sources are not available and, in particular, the extraction from the ambient air is not a technically sensible and energetically and economically efficient alternative due to the extremely low content of C0 ₂ and the resulting high expenditure. In the course of switching the power supply to renewable Such technical systems that burn fossil fuels will no longer be part of the energy supply system.

This results in a considerable problem for all concepts that are aimed at storing excess electrical energy from fluctuating sources in the form of a hydrocarbon, in particular methane gas, since C0 ₂ sources are used, of which emissions of C0 ₂ from combustion are still present run out of fossil raw materials.

To avoid this problem, there are also concepts for circulating the C0 ₂ , as described, for example, in the publication US Pat. No. 5,711,770 A. There, C0 ₂ , separated from the flue gas of an incineration plant, is used to subsequently synthesize methane with hydrogen from an electrolysis plant. The incinerator uses a hydrocarbon to generate electricity. The methane generated in this way is then used again to generate energy, from the combustion of which then clean exhaust gas, which, however, contains fossil CO ₂ , is emitted.

It is therefore an object of the present invention to offer a method and a device or a system of such devices for the efficient and cost-effective stabilization of a power grid, the stabilization taking place by balancing the generation and consumption of electrical energy. The object is achieved by a method for stabilizing a power grid, the stabilization being to take place by means of compensation, in that current is drawn as needed in the event of overcapacity and fed in after a temporary storage in the event of a shortage. On the one hand, surplus electricity that was generated by electricity producers in excess of demand or consumption is taken from the power grid and converted into a storable chemical energy source. According to the invention, a hydrocarbon, primarily methane, is provided as the energy source. It is stored in a simple manner and without additional investment in the receptive, already existing natural gas network, which functions as a large storage facility. On the other hand, in the case of electricity requirements which can no longer be covered by the existing producers because of underperformance or increased demand, this is done by feeding in electricity obtained by reconversion from the stored chemical energy source from the large store. The emission of C0 _{2 is} avoided.

According to the invention, the conversion and storage of the electrical energy, the electricity, takes place in chemical form as at least one hydrocarbon using carbon dioxide (C0 ₂ ), which was formed in a previous cycle by back-conversion and, if necessary, has been temporarily stored or supplied. Back-conversion is a process of combustion of the hydrocarbon with the aim of generating electricity. When the current is converted into the chemical energy carrier, the at least one hydrocarbon, the chemical energy carrier, is synthesized using carbon dioxide (C0 ₂ ) and hydrogen (H ₂ ). The hydrogen (H ₂ ) is obtained from water (H ₂ 0) in an electrolysis process using the excess electrical energy to be stored.

According to an advantageous further development, the oxygen (0 ₂ ) which is equally produced in the electrolysis process in addition to the hydrogen (H ₂ ) is stored and used in the staggered combustion process of the re-conversion into air instead of air from the environment in the combustion air supplied to the combustion process. Advantageously, the device according to the invention further comprises a conditioning system for carbon dioxide (C0 ₂ ), which from the Back-conversion power plant for the generation of electrical energy from the hydrocarbon. According to a further advantageous embodiment, the device according to the invention comprises a separation and conditioning system for the hydrocarbon generated in the synthesis device and a hydrocarbon store for its temporary storage, in particular before the combustion in the reconversion power plant when electricity is required. A device is also provided for supplying at least the hydrocarbon and synthesized oxygen (0 ₂ ) from the electrolysis to the reconversion power plant, which is suitable for burning the hydrocarbon formed using the synthesized oxygen (0 ₂ ).

According to a further advantageous development, a device for recycling a portion of the carbon dioxide (C0 ₂ ) to replace the corresponding portion of nitrogen (N ₂ ) in the combustion air for the combustion of the stored hydrocarbon in addition to the oxygen (0 ₂ ) is provided in the reconversion power plant. A proportion of C0 _{2 is} added to the combustion air, so that in a particularly advantageous case it only consists of oxygen (0 ₂ ) and carbon dioxide (C0 ₂ ). The proportion is chosen so that it is favorable for the incineration plant used to ensure the functioning. The C0 ₂ is circulated in the incinerator by separating it from the exhaust gas and adding it to the incineration process. With this artificial C0 ₂ combustion air, the required separation of C0 ₂ from the combustion exhaust gas is made considerably easier in terms of energy and equipment. The replacement of nitrogen otherwise present in the combustion air with over 70% by volume by C0 ₂ has the advantage that the atmospheric nitrogen is no longer part of the combustion air and only C0 ₂ , H ₂ 0 and other slightly present combustion gases are present in the flue gas. The separation system for the C0 ₂ can then be carried out much more simply because of the absence of foreign gases (e.g. no NO _* ) and will then probably only have about 1/10 of the investment required compared to that which works with the natural nitrogen content of the air.

The reason for the very simplified C0 ₂ deposition process technology is that the C0 ₂ partial pressure is almost 100% after the condensation of H ₂ 0 vapor. With normal combustion using ambient air there is a very high one Partial pressure of nitrogen of up to 70% in the flue gas, that of C0 _2, however, only of about 20%.

A particularly advantageous effect of the proposed method is based on the fact that the substitute air containing CO ₂ , which is fed to the combustion process, has a cooling effect due to the CO ₂ content. The combustion temperature can thus be set via the C0 ₂ component in such a way that it does not exceed the permissible value for the combustion technology used in each case. While a combustion with oxygen alone requires a special and expensive plant technology that can withstand the elevated temperatures in the combustion chamber, the invention enables the use and the connection with conventional combustion technology that cannot be used for high combustion temperatures, such as those used in the Combustion with almost pure oxygen (oxyfuel process) may occur.

The reconversion power plant advantageously has a plant for combined heat and power. The plant for combined heat and power is preferred as a gas and steam power plant, an internal combustion engine such. B. a gas engine or a gas turbine for use in a combined heat and power plant for the combustion of natural gas and generation of electricity heat or is designed as a fuel cell device.

The hydrocarbon to be stored is advantageously in gaseous form and the hydrocarbon store is designed as a gas storage arrangement. In this context, it has proven to be particularly advantageous if the gas storage arrangement comprises an existing natural gas network NGN with associated, existing natural gas stores, to which at least methane gas is supplied. A portion of hydrogen (H ₂ ) that comes directly from the electrolysis could also be added. It is therefore appropriate for a particularly advantageous energy storage with large capacity and without essential technical additional devices, the existing, widespread NGN natural gas network connected to gas storage (e.g. caverns) as an energy storage for the chemical energy carrier formed according to the invention, advantageously synthetic methane SNG to use. In comparison to other energy stores, the NGN can store a considerably larger amount of energy. The currently available storage capacity of the NGN can with simple means can even be expanded considerably. With a pressure increase of a few mmWS in the existing gas storage facilities, additional amounts of energy in the range of an energy equivalent in the amount of a few TWh can be stored. The synthesized gaseous methane SNG, which is synthesized from hydrogen (H ₂ ) and carbon dioxide (C0 ₂ ) that is available in the storage system, is therefore preferably used as the energy source for storage. The hydrogen (H ₂ ) comes from the electrolysis, which is operated with the excess electricity. Furthermore, the carbon dioxide (C0 ₂ ) from the time-shifted necessary re-conversion of natural gas or in the future increasingly synthesized gaseous methane SNG will be used in gas power plants. The carbon dioxide (C0 ₂ ) is temporarily stored in the combustion process so that there are no C0 ₂ emissions, because NG is currently fossil in the NGN natural gas network to a large extent. Only later, at least partially and increasingly, can carbon dioxide (C0 ₂ ) also originate from renewable energy sources. The method according to the invention contributes to “decarbonization” because no further CO ₂ from the technical processes concerned will get into the atmosphere. Another aspect of the present invention relates to a device for

Stabilization of a power grid, the stabilization by balancing the generation and consumption of electrical energy by removing excess electrical energy from the power grid and converting it into a storable one

Energy carriers and their storage on the one hand and a re-conversion of the stored energy carrier and feed into the power grid on the other hand are provided. According to the invention, for the conversion of electrical energy into a hydrocarbon, an electrolysis device for at least the production of hydrogen (H ₂ ), a synthesis apparatus, preferably designed as a plant for methane synthesis, for the production of at least one hydrocarbon, preferably methane, using the Hydrogen (H ₂ ) and carbon dioxide (C0 ₂ ) provided. Furthermore, a re-generation power plant is provided for generating the electricity, which is fed into the power grid to stabilize it if necessary. An advantageous embodiment of the device according to the invention further comprises a conditioning system for carbon dioxide (C0 ₂ ) from the Back-conversion power plant for the generation of electrical energy from the hydrocarbon, a separation and conditioning system for the hydrocarbon produced and / or a hydrocarbon storage NGN. Furthermore, a device is provided for supplying at least the hydrocarbon and synthesized oxygen (0 ₂ ) to the reverse power generation plant suitable for combustion of the hydrocarbon formed using the synthesized oxygen (0 ₂ ).

According to a further advantageous embodiment, a device for recycling a portion of the carbon dioxide (C0 ₂ ) to replace the corresponding portion of nitrogen (N ₂ ) in the combustion air for the combustion of the hydrocarbon is provided in addition to the oxygen (0 ₂ ) in the re-generation power plant. The hydrocarbon storage NGN is preferably designed as a gas storage arrangement. In particular, methane is provided as the hydrocarbon and the reconversion power plant has a plant for combined heat and power. The plant for cogeneration is particularly preferably designed as a gas and steam power plant, a combined heat and power plant for the combustion of natural gas or a fuel cell device. It has also proven to be advantageous if the gas storage arrangement comprises an existing NGN natural gas network with existing natural gas storage, to which at least methane is supplied.

The system according to the invention for stabilizing a power grid represents a further aspect of the present invention and comprises a large number of devices for stabilizing a power grid, each of which comprises the power storage unit SSE and the back-conversion power unit RSE. The system according to the invention thus consists of the combination of flatly distributed elements of the electricity storage SSE and associated elements of the reverse electricity generation RSE, which are integrated into a power network, for example the Germany-wide power network DSN, which is also internationally linked with other countries, and to that NGN natural gas network, which is also internationally linked to the natural gas networks of other countries.

In addition, the SSE and RSE are connected via a superordinate classic or Internet communication and actively participate in regulating the stability of the entire power grid. In each of the units, at least the hydrocarbon for storage in the can be from an excess of electrical energy Hydrocarbon storage, preferably designed as a natural gas network NGN, is generated or, if there is a need for electricity, at least stored hydrocarbon is removed from the hydrocarbon storage and electrical energy is generated therefrom for feeding into the power network.

The NGN is used as a large-volume storage. If there is a surplus of electricity, the DSN supplies the SSE to the NGN to store the electricity in the form of methane (SNG) synthesized from hydrogen (H ₂ ) and carbon dioxide (C0 ₂ ). When electricity is required in the DSN, electricity is generated from natural gas or SNG from the NGN by means of reconversion and fed into the DSN.

According to an advantageous further development, the network further comprises, at least in part, a CO ₂ gas network for transporting the carbon dioxide (CO ₂ ) from the reconversion power plant between the facilities of the network and / or a hydrogen gas network for transporting the hydrogen (H ₂ ) from the Electrolysis facility between the facilities of the network. Another advantageous further development provides, at least in part, a C0 ₂ storage and / or a hydrogen storage, where the gases can be stored before or after transport or at convenient locations on the transport route.

The preferred version of the RSE consists of the following basic elements:

A suitable connection at the NGN for the extraction of gas, natural gas or SNG,

A power plant for the generation of electricity from the use of gas from the NGN with a plant for the use of waste heat,

A system for separating H ₂ 0 and C0 ₂ from the exhaust gas from the power plant or the combustion,

A C0 ₂ memory with supply line to the SSE,

• a oxygen line for oxygen from the electrolysis from the SSE to the RSE, · a system for mixing the artificial combustion air from oxygen from the electrolysis and circulating C0 ₂ from the separation;

• A suitable feed connection for electricity to the DSN.

The preferred embodiment of the SSE consists of the following basic elements:

A suitable connection for drawing current from the DSN, A plant for water electrolysis,

A plant for methane synthesis with a plant for conditioning methane gas and a plant for extracting high-temperature waste heat for further use,

A buffer storage for hydrogen (H ₂ ),

A storage for oxygen (0 ₂ ) with supply line to the RSE,

A supply line of C0 ₂ from the C0 ₂ memory of the RSE to the SSE,

• A suitable SNG feed connection to the NGN. The RSE and SSE can be set up directly next to each other or spatially separated, connected by cables, to e.g. B. to supply the waste heat locally for use.

This stored hydrogen is used when methane is synthesized and stored in the large NGN storage facility. The operation of the interconnected SSEs and RSEs is controlled centrally in conjunction with the power grid regulation.

The aim of the control is

· To store electricity in the form of SNG through the connected SSE in the NGN,

• to store electricity in the form of SNG through the connected SRE in the NGN in the event of current surpluses,

• Feed electricity into the grid via the connected SRE via the conversion of SNG or methane from the NGN if required

• ensure that no C0 _{2 is} emitted when the SNG is converted back into electricity in the gas power plant.

The invention therefore represents a large-volume electricity storage system based on C0 ₂ with minimal or completely no C0 ₂ emissions into the atmosphere. The method according to the invention uses C0 ₂ for energy storage - without additionally emitting C0 ₂ . The process mimics natural plant processes in which C0 _{2 is used} as a working substance for energy storage. The central approach is on the one hand that with good availability of wind and sun by means of electrolysis, hydrogen gas as a raw material for the synthesis of methane gas will be produced. Carbon dioxide is added to the hydrogen gas; artificial, synthesized methane gas SNG is created as a very high-energy substance. On the other hand, the artificially synthesized methane is stored where the natural gas is already stored according to the state of the art: in the existing natural gas network. The natural gas network has such a large storage capacity that it can easily absorb a quantity of gas that can be converted back into a climate-neutral way in highly efficient, easily regulated gas power plants when the sky is calm and the sky is cloudy. In Germany, for example, this is enough to bridge at least two weeks of unfavorable weather that restricts or prevents the generation of renewable energy. And finally, C0 _{2 is} a working substance for energy storage, as in nature, that remains in the storage system according to the invention and does not have to be emitted or constantly added again.

Insofar as the proceeds from the stored electricity and from the use of heat are not sufficient to operate the storage system economically, the costs for the regulation and stabilization of the electricity networks possible with the system according to the invention are to be recognized. It is only through such regulation and stabilization that, despite fluctuating generation, renewable energy can meet demand even under different load conditions.

The following effects would have to be taken into account for an overall national accounts as the basis for an economic assessment:

• the economic need to stabilize power grids;

• Reduced load on power transmission lines or the elimination of new systems and the corresponding cost savings;

• The structural change effects: creation of new and preservation of existing industrial jobs, creation of industrial perspectives in the regions as a means against migration, development of a new export economy and last but not least

• recognizable government action to reduce increasing political disaffection.

Process losses occur in the form of heat that can be used for other purposes. The losses occurring in the process are therefore thermal. The generation takes place on the basis of electricity taken from the power grid, which is based on renewable energy sources.

In the same way, it is necessary to ensure economically efficient operation of the required storage. This can either be done by adjusting the gas prices for the stored SNG or the storage facilities are assigned to the electricity grid to be stabilized and a surcharge is added to the grid fee in order to ensure business feasibility. Network operators can reserve network equipment to ensure the security and reliability of the electricity supply system.

The economic situation can be further improved if the gas power plants that will also be switched off in the future and work with fossil natural gas are converted into re-generation plants for the process according to the invention. This would result in a considerable outlay for a new installation or costs, which represents the essential effect of the present invention. The method according to the invention alone makes it possible to convert gas power plants that work with fossil natural gas. The invention is explained in more detail below on the basis of the description of an exemplary embodiment and its representation in the associated drawing.

A forecast for the period 2017 to 2037 in Germany showed which electricity storage capacities are required to stabilize the DSN power grid with the current renewable energy producers with their fluctuating electricity supply. In 2037, the power storage must according to this forecast an output totaling 30 GW _ei power and 52 TWh _e a have capacity. This size can only be covered with the huge storage facility that the existing natural gas network represents.

If the method according to the invention for converting electricity into SNG is used because of the storage volume, an input volume of 76 GW _ei and a withdrawal capacity with a volume of 131 TWh _ei / a are likely to result. Using the example of a memory as part of an exemplary embodiment of the device according to the invention with 100 MW _ei output and a capacity of 1 GWh _ei the process is illustrated. A memory module consists of the two components RSE and SSE, which work at different times and, if necessary, also spatially separated:

Retrofit unit RSE for power supply, in particular designed as a retrofit power plant RVKW, for example in the form of a gas and steam power plant GuD, which is operated with the SNG stored in the natural gas network (currently on the balance sheet). A combined cycle plant uses gas turbines and subsequent steam turbines and thus achieves an efficiency for electrical energy generation of up to 60%. The RVKW uses the oxygen obtained from the electrolysis instead of air for combustion. The C0 ₂ separation from the flue gas is greatly simplified. The RVKW feeds electricity into the DSN power grid when stabilization is required. The separated C0 ₂ is stored in a 30 bar pressure accumulator for time-shifted use in methane synthesis. The storage volume depends on the size of the storage capacity.

Power storage unit SSE: The electricity to be stored is used to generate hydrogen and oxygen using electrolysis. The oxygen is stored in a pressure accumulator for time-shifted use in RVKW. Together with C0 ₂ from the RSE storage, the hydrogen generated is used to produce methane in a synthesis system at 30 bar and at 300 ° C. After conditioning, the methane is fed into the natural gas network as synthetic natural gas SNG.

In order to cover the total demand determined, devices 1 according to the present invention are installed distributed over a large area. In each of the two components RSE and SSE present in the facilities 1, non-fossil waste heat is produced to a greater extent. It can be used locally, which significantly improves the overall efficiency of the method.

1 shows the scope of equipment and the material flows of the 100 MW / 1 GWh electricity storage unit mentioned as an exemplary embodiment, the process engineering and apparatus engineering design of the example for a storage unit with 100 MW _ei installed power and 1 GWh _ei capacity occurs. In nature, the solar energy falling on the earth could not be stored without using C0 ₂ . The plants emit C0 ₂ for their metabolism maintain their functionality when the sun is not shining. However, so much solar energy is stored in the biomass with C0 ₂ that ultimately all of humanity is nourished with it. The life energy of mankind - and of course that for flora and fauna - comes about through the use of solar radiation with the participation of C0 ₂ .

The use of biomass for the design of the energy processes of people with ultimately C0 ₂ -based nutrition as well as for flora and fauna leads to C0 ₂ emissions, whereby the C0 _{2 is} then used again for the storage of solar energy in biomass. In the balance, however, this solar radiation C0 ₂ biomass process does not lead to an increase in C0 ₂ in the atmosphere.

The natural gas network is a large technical coal-hydrogen system, a storage system such as biomass in nature, in which methane synthesized from solar-generated electricity and C0 _{2 is} stored and removed when electricity is required. The C0 ₂ generated during the re-conversion is retained for reuse in the methane synthesis. The need for storage is evident. The electric current obtained from renewable energies such as B. solar radiation by means of photovoltaic systems, from wind by means of wind energy systems, from running water by means of hydropower plants is volatile or fluctuating. Generation is affected by the naturally occurring daily and seasonal as well as weather-related, overall considerable fluctuations in the performance of the respective renewable energy sources. The problem of an unstable power supply becomes more serious the further the share of electricity from renewable energies increases. Given the goal in Germany of at least 95% of all sectors by 2050, the problem is serious.

Germany had a gross electricity consumption of 654 TWh / a of its generation in 2017, of which 244 TWh comes from renewable energies, 148 TWh from lignite, 76 TWh from hard coal and 86 TWh from fossil gases. In 2017, power plants with installed capacities of 112,537 MW were renewable energies, of which 50,291 were wind power (onshore) and 42,339 MW were photovoltaics. Power plants of non-renewable energies had an output of 103,046 MW installed, including pumped storage power plants with 9,848 MW.

In the case of oversupply with electricity from renewable energies, it can already be expected that, in spite of the existence of overarching, supranational electricity networks, there may be total short-term failures of the electricity supply. On the other hand, there may be an abundance of power generation in the

Wind turbines and photovoltaic systems are coming so that they have to be curtailed so as not to endanger the stability of the grid. Such a procedure is costly, as can already be seen, since unused electricity is remunerated on a legal basis.

The problems of temporary lack of generation by the renewable energy power plants are currently being compensated for by some pumped storage power plants, reserve or running coal power plants or gas power plants. The

In the future, fluctuations could also be dampened by more intelligent networks and coordinated, more intelligent consumers.

However, there is a demand that cannot be ignored with the energy turnaround towards renewable energies, parallel to the expansion of electricity generation from renewable energy sources, to provide the networks with large-volume, long-term electricity storage, especially of surplus and reserve electricity, and high-performance, high-volume electricity generation from these electricity storage facilities. A forecast for required electricity storage based on the 2017 figures and a rough balance sheet simulation of the design of the power supply for the 2017-2022-2027-2032-2037 series were carried out.

The electricity requirement remains at the value of 654 TWh. It can be assumed that the energy efficiency of the electricity application will increase by at least 50% and that the use of electricity will be available within this framework. The full load hours of all power plants, in particular the renewable energy power plants, from 2017 were then used consistently to map the ratio of generation to installed capacity. The situation can improve somewhat as the offshore share of wind turbines increases. Storage systems play an essential role in security of supply, which increasingly strengthens the stability of the electricity network (DSN) against the growing volatility of electricity generation must secure from renewable energies. Here, based on the storage facilities that already existed in 2017, rates of increase for the performance of the storage facilities were set in line with the required increase in generation from renewable energies.

Storage input capacities of 76 GW input and back-conversion gas power plants for 30 GW _ei output are forecast to be necessary to ensure an adequate and stable power supply. With 30 GW _ei memory-output current, the gaps are closed to secure the assumed consumption of 650 TWh / a, which comes only from the use of renewable energy sources, stable.

The only storage technology that can comprehensively secure this throughout Germany - here for the example of Germany - is the existing natural gas network as a storage facility for the SNG and from which it can be extracted throughout Germany for re-generation. It is able to store 80 TWh of SNG obtained from 130 TWh of storage electricity, for example from renewable energies. A basic conclusion - no matter what storage structure is involved - is that the electricity generation system must have higher generation capacities than would be needed for consumption to cover the storage losses.

For implementation in terms of process engineering, the systems according to the invention for storing electrical energy in a hydrocarbon comprise two essential components, the reverse-conversion unit RSE and the electricity storage unit SSE:

The RSE comprises a RVKW reconversion power plant, in particular a combined cycle gas and steam power plant, which uses SNG (in the balance sheet, practically with natural gas) to generate the storage output electricity from the re-generation and for feeding into the DSN power grid from the existing natural gas network storage . The CO ₂ required for methane synthesis is separated from the flue gas from the reconversion power plant.

The separation can be made simple if the RVKW is operated instead of combustion air from the environment with pure oxygen or preferably in the sense of the present invention with artificial air, a substitute air. The Replacement air consists of oxygen, mixed with C0 ₂ to be circulated. The oxygen for this comes from the electrolysis of the SSE described below.

The C0 ₂ is stored in the RSE in a pressure accumulator because of the reduction in volume and also because of the working pressure of 30 bar required for methane synthesis.

The SSE, the electricity storage system, consists of a pressure electrolysis system that generates hydrogen (and oxygen) at a pressure of 30 bar from the electricity to be stored. The hydrogen is used in the SNG synthesis plant (also as

Methane synthesis plant) was synthesized together with C0 ₂ from the storage of RSE methane and, after conditioning, was fed into the NGN natural gas network to the extent required. The SSE also includes a 30 bar pressure accumulator for the oxygen obtained, which is used in the RSE described above. There can also be an excess of oxygen K4.1 which is used for further technical use.

The RSE obtains its operating energy from the NGN natural gas network, which is used as a storage facility, feeds electricity into the DSN power network as required and can emit waste heat, especially if the RVKW is operated in a combined heat and power mode. When converting back into electricity, 40% (based on current state-of-the-art efficiency) of the electricity used for storage in the SSE can be recovered.

SSE and RSE can be installed together in one place or in close proximity. But in an alternative embodiment it is also sensible to set up the SSE separately from the RSE and to transport the C0 ₂ , preferably via a line, from the RSE to the SSE. Likewise, a 0 _{2 line} must then be routed from the SSE to the RSE. It must be decided on a project-related basis where the C0 ₂ memory should be in this case. Separation is particularly appropriate if the extensive waste heat from electrolysis (20 - 30% at low temperature) and from the exothermic synthesis (20 - 30% at 300 ° C) can be used well at the chosen location. This is of great advantage for economical operation of the system and also improved energy efficiency. In principle, there is a temporal separation of the operating times of RSE and SSE, which results in different operating cases. The most important operating cases are described below. The RSE comprises the main components K1 and K2, the SSE the main components possibly K2 and K3, K4 and K5 as shown in FIG. 1.

Operating case 1 - power grid stabilization through power supply:

The course of the operation is shown in FIG. 1 by dashed lines. The RSE is running because there is a need for power feed-in in the DSN power grid. For this purpose, NG is taken from the NG network and 0 ₂ , which originates from the SSE and has been stored, is taken from the 0 ₂ memory K3. C0 _{2 is} separated from the flue gas of the CCG K1 and fed to the C0 ₂ storage K2, where it is stored under pressure for later use in the SSE. In this case, the SSE is not in operation. Alternatively, the C0 ₂ can first be added to the combustion in the RSE and circulated.

Operating case 2 - power grid stabilization by taking over surplus electricity:

There is an excess of electricity in the DSN power grid. The RSE is standing, the SSE is in operation. K4 0 ₂ and H _{2 are} obtained from the excess current by electrolysis in the main component. Methane is synthesized from the C0 ₂ memory K2 with the H _{2 obtained} in the SNG synthesis plant and stored in the NGN.

Operating case 3 - power grid stabilization through load transfer:

The course of this operation is shown in FIG. 1 by dash-dot lines. There is still no surplus of electricity in the DSN power grid, but there are signs that large customers will be shut down, or it is advisable to obtain cheaper renewable energy from abroad via the DSN power grid. The RSE is standing, the SSE is put into operation. Electrolysis 0 ₂ and H _{2 are} obtained from electricity, each of which can be temporarily stored in a buffer memory K2, K4.2. Methane is synthesized from the C0 ₂ memory K2 with the H _{2 obtained} in the SNG synthesis plant K5 and stored in the NGN.

For the devices 1 according to the invention for the stabilization of a power grid (DSN), existing gas power plants can be used as a recuperation power plant, which in a simple manner and while continuing to use the main units RSE would be expandable in the sense of the embodiment. For this purpose, the SSE would have to be built new so that a storage system according to the invention is created.

The devices 1 according to the invention for stabilizing a power network (DSN) should cover a larger area, eg. B. Germany, distributed and built with module sizes of up to 100 MW _ei power conversion. GW would be for a required storage capacity of 30 300 systems of the invention for storing electrical energy in a hydrocarbon, each of 100 MW _ei required. A number of these can be formed from already existing gas power plants, to which the electricity storage units SSE are provided in the sense of the invention or are erected elsewhere.

The following is a procedural description of the above previously mentioned embodiment with a module with 100 MW _ei Stromeinspeiseleistung and a capacity of 1 GWh:

For the RSE with an installed re-generation capacity of 100 MW _ei , the combustion calculation for a CCGT K1 with an efficiency of 62% results in a demand of 162 MW _therm / h, for which 14,600 Nm ³ / h natural gas are consumed. If the combined cycle is operated with oxygen from the electrolysis, the exhaust gas consists of 14,600 Nm ³ C0 ₂ / h and 29,208.27 Nm ³ / h H ₂ 0 steam, which can be condensed and reused for 23.5 m ³ / h water electrolysis is K4. The heat of condensation can be used in the process or for external heat consumers. It is intended to store the water in a condensed water storage K1.1 and to keep it ready for the aforementioned use.

The C0 ₂ separated from the combustion exhaust gas of the CCG K1 is compressed to the synthesis pressure of 30 bar and stored in the C0 ₂ memory K2, e.g. B. in a disc gas storage. At 30 bar the necessary intermediate storage volume of the C0 _{2 is} reduced to approx. 4,400 m ³ / h.

This stored C0 ₂ forms the basis for the synthesis of SNG. If the C0 ₂ storage K2 is designed for a feed capacity of 1 GWh, a total C0 ₂ storage volume of 44,000 m ^{3 is} required. The required C0 ₂ storage K2 would have an edge length of 35 m as a cube, a diameter of 44 m as a ball or a diameter of 40 m at a height of 35 m as a cylinder. The oxygen produced in the electrolysis K4 is used, for example, for a pure oxy-fuel combustion process or for combustion in a substitute air, which consists of a mixture of oxygen (0 ₂ ) with C0 ₂ , in the CCG K1. Above all, the C0 ₂ separation is greatly simplified compared to combustion with ambient air. With 100 MW _ei 14,600 Nm ³ / h 0 _{2 are also} required. The oxygen comes from the electrolysis plant K4, preferably configured as pressure electrolysis, and is under a pressure of at least 30 bar. A memory K3 for the oxygen that is as large as that for the C0 ₂ is therefore required. The main components K1 and K4 give off waste heat for further use.

List of reference symbols / list of abbreviations bar - excess pressure (1 bar = 105 N / m ² )

DSN - Germany-wide electricity network

GuD / GuD-KW - gas and steam power plant

GW _ei - GigaWatt electrical power (Giga = 10 ⁹ )

Ki, i = 1 ... 5 - main component

K1 - combined cycle power plant

K1.1 - condensed water storage

K2 - C0 ₂ memory

K3 - 0 ₂ memory

K4 - electrolysis

K4.1 - Excess oxygen

K4.2 - Hydrogen buffer storage

K5 - methane synthesis

mmWS - millimeter water column (pressure)

MW _ei - megawatt electrical power (Mega = 10 ⁶ )

NG - natural gas

NGN - natural gas network

RSE - power conversion unit

RVKW - reverse electricity generation plant

SNG - Synthetic Natural Gas

SSE - electricity storage unit

TWh _ei - terawatt hours of electrical energy (Terra = 10 ¹² )

Claims

1. A method for stabilizing a power grid, the stabilization by a

Balancing the generation and consumption of electrical energy by taking excess electrical energy from the power grid, converting it into a storable energy carrier and storing it on the one hand, and a

Back-conversion of the stored energy source and feeding into the power grid on the other hand, characterized in that with an increased consumption compared to the generation of electrical energy, the conversion and storage in chemical form as at least one hydrocarbon as a storable chemical energy source using in a previous cycle by back-conversion Carbon dioxide (C0 ₂ ) is formed, a synthesis of the at least one hydrocarbon using the carbon dioxide (C0 ₂ ) and hydrogen (H ₂ ) obtained in an electrolysis process from water (H ₂ 0) using the electrical energy to be stored is done.

2. The method according to claim 1, wherein at least the oxygen (0 ₂ ) obtained in the same way in the electrolysis (K4) is added in a combustion process of the re-conversion into electricity, so that the corresponding proportion of nitrogen (N ₂ ) in the combustion air through the oxygen (0 ₂ ) is at least partially replaced.

3. The method according to claim 1 or 2, wherein a recirculation of a portion of the available carbon dioxide (C0 ₂ ) is provided in the process of converting electricity and through the carbon dioxide (C0 ₂ ) the corresponding proportion of nitrogen (N ₂ ) in the combustion air, which in addition to the Oxygen (0 ₂ ) is present, which is necessary for the combustion of the hydrocarbon for reconversion, is completely replaced.

4. The method according to any one of the preceding claims, wherein the combustion of the hydrocarbon for reconversion into a gas and steam power plant (K1) or in a fuel cell device.

5. The method according to any one of the preceding claims, wherein during the synthesis and / or in a flue gas cleaning and / or the deposition of carbon dioxide (C0 ₂ ) water obtained from the flue gas is used in the electrolysis and / or in process steps of conditioning.

6. The method according to any one of the preceding claims, wherein the gaseous hydrocarbon is directly mixed with hydrogen (H ₂ ) from the electrolysis device (K4).

7.Installation for stabilizing a power grid, the stabilization being provided by balancing the generation and consumption of electrical energy by removing excess electrical energy from the power grid and converting it into a storable energy source and storing it, and on the other hand re-converting the stored energy source into the power grid are characterized in that for converting the electrical energy into a hydrocarbon an electrolysis device (K4) for at least the production of hydrogen (H ₂ ), a synthesis apparatus (K5) for the production of at least one hydrocarbon using the hydrogen (H ₂ ) and the Carbon dioxide (C0 ₂ ) are provided, with a back-conversion power plant (K1, RVKW) for generating electrical energy from the hydrocarbon being provided.

8. The device of claim 7, further comprising a conditioning system for

Carbon dioxide (C0 ₂ ) from the reconversion power plant (K1), a separation and conditioning system for the hydrocarbon produced and a

Hydrocarbon reservoirs (NGN) are provided, with a supply of at least the hydrocarbon and synthesized oxygen (0 ₂ ) to the re-conversion power plant (K1, RVKW) suitable for burning the hydrocarbon formed using the synthesized oxygen (0 ₂ ).

9. The device according to claim 7 or 8, wherein further recycling of a portion of the carbon dioxide (C0 ₂ ) to replace the corresponding portion of nitrogen (N ₂ ) in the combustion air for the combustion of the hydrocarbon in addition to the oxygen (0 ₂ ) in the reconversion power plant ( K1, RVKW) is provided.

10. Device according to one of claims 7 to 9, wherein the hydrocarbon is gaseous and the hydrocarbon storage (NGN) is designed as a gas storage arrangement.

11. The device according to claim 10, wherein methane is provided as the hydrocarbon and the reconversion power plant (K1, RVKW) has a plant for cogeneration.

12. The device according to claim 11, wherein the plant for cogeneration is designed as a gas and steam power plant (K1), a combined heat and power plant for the combustion of natural gas or a fuel cell device.

13. The device according to claim 12, wherein the gas storage arrangement comprises an existing natural gas network (NGN) with existing natural gas storage, to which at least methane is supplied.

14. System for stabilizing a power network, characterized in that a plurality of devices (1) for stabilizing a power network (DSN) according to one of claims 7 to 13 are linked in such a way that in each of the devices (1) at least the hydrocarbon for storage in the hydrocarbon storage (NGN) is generated from an excess of electrical energy, or at least stored hydrocarbon is removed from the hydrocarbon storage (NGN) when electricity is required and electrical energy can be generated therefrom.

15. The system of claim 14, wherein the composite at least partially further a C0 ₂ -

Gas network for the transport of carbon dioxide (C0 ₂ ) from the

Back-conversion power plant (K1, RVKW) between the devices (1) of the network and / or a hydrogen gas network for transporting the hydrogen (H ₂ ) from the electrolysis device (K4) between the devices (1) of the network.

16. The system of claim 14 or 15, wherein at least partially a C0 ₂ storage (K2) and / or a hydrogen storage (K4.2) are provided.