Storage power plant

A storage plant referred to in the context of electrical engineering and the power generation a large energy storage , in which electrical energy can be cached. Storage power plants convert electrical energy, depending on the type of power plant, into potential energy (position energy), kinetic energy , chemical energy or thermal energy , which can be stored in this form for a certain period of time and converted back into electrical energy when required.

During storage and recovery, there is a loss of energy, depending on the type of power plant and the duration of the storage, from which the average efficiency of a plant can be determined.

Tasks of storage power plants

Electric power grids cannot store energy. Since there are fluctuations in both the consumption and the provision of electricity, storage power plants serve to provide control power and demand reserves within the framework of grid regulation . This includes:

• Compensation of fluctuations in consumption and peak loads depending on the time of day ( load profile )
• Compensation of temporal and meteorological fluctuations in electricity generation by solar systems and wind turbines . Absorption of excess electricity.
• Compensation in the event of network disruptions or the failure of individual power plants.
• Avoiding power outages and making it easier to start up power plants after a power outage . Many storage power plants are black start capable .

Storage power plants are technically designed so that they can deliver electrical power as required in the shortest possible time. Battery storage power plants and flywheels can provide energy within milliseconds. Compressed air and pumped storage power plants are ready for use within a few minutes. Depending on the system, the power range is from a few kilowatts to a few 100 MW, the duration of the provision can be between a few minutes or several hours.

Significance for the energy transition

With the increased expansion of wind and solar energy as part of the energy transition , the feed-in of which is dependent on the weather, an expansion of storage power plants is necessary. While below a share of 40% renewable energies in annual electricity generation, compensation through thermal power plants and a slight curtailment of generation peaks from renewable energies are an efficient way of compensating for this, above this threshold more storage capacity is required. For Germany, it is assumed that further storage systems will be required from 2020 at the earliest. Up to a share of approx. 40% renewable energies in annual electricity production, a more flexible mode of operation of the existing conventional power plants is the most advantageous way of integrating renewable energies; additional storage power plants are only needed above this. Instead, storage facilities that are built beforehand enable lignite power plants to be better utilized at the expense of less environmentally harmful power plants (hard coal and natural gas) and thus increase CO ₂ emissions.

Power plant types

The different storage power plants primarily differ in the storage medium with which the energy is stored. Physical methods, such as storage with the help of heat, potential or pressure differences, as well as chemical methods are used here.

Layer energy storage (potential energy)

The following types use the potential energy (positional energy) of a storage mass as a form of energy for intermediate storage:

Water storage power plant

→ Main article : Water storage power plant

In the case of a water storage power plant, the water of a river is dammed up into a reservoir , from which it can flow off in times of increased energy demand and generate electricity in a hydropower plant. Due to the natural inflow, the reservoir fills up again by itself. However, no electrical energy from the power grid can be used to fill the water storage power plant. Hydropower plants in which the running water is used continuously are called run-of-river power plants .

In Norway, hydropower plants are a cornerstone of the energy supply. Around 1250 hydropower plants deliver more than 120 TWh of electricity annually.

pumped storage power plant

→ Main article : Pumped storage power plant

Water basin for the Goldisthal pumped storage plant in Thuringia

Pumped storage power plants function like water storage power plants. In addition, excess electrical power from the power grid can be stored. For this water is from a low position with pump pumped to the higher reservoir. The efficiency is approx. 70% to 85%.

In Germany, pumped storage power plants are of great importance for the provision of control power for controlling the electricity network. There are around 30 pumped storage power plants across Germany with a total output of 7 gigawatts and a storage capacity of 40 GWh.

Ball pump storage

→ Main article : Ball pump accumulator

As of 2017, spherical pump storage is a special type of pumped storage power plant, in which hollow concrete spheres with a diameter of approx. 30 m are installed under water at a maximum depth of 700 m. If there is a surplus of electricity (e.g. from an offshore wind farm ), the water is pumped out of the hollow sphere; when electricity is required, water is allowed to flow back into the hollow sphere, driving a turbine with a generator. A sphere 30 m in diameter would weigh 10,000 tons and could store 20 MWh. The efficiency would be between 75% and 80%.

Lift storage power plant

→ Main article : Lift storage power plant

Lift storage power plants store electrical energy in the form of potential energy (position energy). Instead of water, solids are used as storage mass. The technology for this has basically been tried and tested from numerous other applications (for example the cuckoo clock ), but so far there are hardly any systems for large-scale use.

The completion of a system near Pahrump (USA) is planned for 2019: An automatically controlled electrically powered train is to travel up and down an eight-kilometer-long track with a height difference of 600 m in order to store the energy from local solar and wind systems and to release them again via regenerative braking . The wagons are weighted down with cast concrete forms, each weigh 272 t and should generate an output of 48 MW with an efficiency of 80% on the descent.

A test system is currently (as of early 2020) being built in the canton of Ticino .

Rotating mass storage (kinetic energy)

→ Main article : Flywheel storage power plant

In a flywheel storage power plant , a flywheel is driven by an electric motor and the energy is stored in the form of rotational energy for short storage times in the range of minutes. Modern flywheels work at high speeds with low friction losses due to magnetic bearings and vacuum . When drawing electrical energy, the flywheel is braked by an electrical generator. Typical applications are the stabilization of power grids and the recovery of braking energy in rail traffic and industrial applications. There are plants worldwide in the power range up to a few MW, e.g. B. at the Max Planck Institute for Plasma Physics in Garching for the ASDEX Upgrade experiment , in which the current heats the plasma in fractions of a second.

Chemical storage

Combustion gases can be generated with the help of electricity ( power-to-gas concepts), gas pipelines and buffer tanks can be used as storage

Since accumulators store electricity, it is planned to use the fleet of parked electric cars as variable electricity storage ( vehicle-to-grid system)

Battery storage power plant

Batteries for the emergency power supply of a data center

→ Main article : Battery storage power plant

In the case of relatively low power outputs (up to 300 MW), accumulators are used in battery storage power plants to stabilize the grid. As of 2016, battery storage systems with a capacity of 1.5 GW were installed worldwide, and the trend is rising.

Redox flow battery

→ Main article : Redox flow cell

The redox flow battery is a special form of the accumulator: the two energy-storing electrolytes circulate in two separate circuits, between which the ions are exchanged in the galvanic cell by means of a membrane. The tank size with the electrolytes is easily scalable. It is considered possible that flow cells based on environmentally friendly lignin with a storage efficiency of 90% will have storage costs of approx. 3 ct / kWh in the future. Compared to a lithium-ion battery, the energy density of a redox flow cell is many times lower.

Thermodynamic energy (pressure and heat)

Compressed air storage power plant

→ Main article : Compressed air storage power plant

In a compressed air storage power plant, compressed air is used in caverns in former salt domes to store energy. There are currently only a few plants that also have to be operated with gas. When the air expands, it cools down considerably, so that the turbines would freeze up without additional gas firing. Test systems, so-called adiabatic compressed air storage power plants, which can be operated without the additional use of gas, are being planned.

Instead of storing them in caverns, there has also been a prototype since 2015 in which balloons are filled with compressed air underwater: The Canadian company Hydrostor has installed a test facility on the bottom of Lake Ontario, 2.5 km from the coast at a depth of 55 meters. Underwater at a depth of 50 to 100 meters, huge balloons made of nylon fabric are attached to the bottom. If there is an excess of electricity, air is pumped into the balloons. The compressed air comes from compressor systems on land, which are connected to the balloons with pipes. The air is strongly compressed by the water pressure, so that a large amount of air has space in the balloons without the balloons being heavily loaded. When electricity is required, the air from the balloons is allowed to flow through the pipes on land through a turbine that drives a generator. In this way, the stored energy is converted back into electricity. When the air is compressed, heat is generated which is stored in a heat exchanger and is returned to the air when it flows back and relaxes.

Thermal storage power plant

Heat storage power plants are energy stores for small to medium amounts of energy in the form of a heat-storing medium with the highest possible thermal heat capacity, temperature resistance and reserve amount. The process of heat storage takes place conventionally via an electric heater or a heat pump , while the energy is dissipated via a conventional steam power plant . Solid stone granules or liquid heat transfer media come into consideration as possible media , which, depending on the design, can be heated to a few hundred to a thousand degrees Celsius.

As part of the energy transition and the coal phase-out planned in Germany by 2038, tests are currently being carried out to determine whether the conversion of coal-fired power plants into heat storage power plants will be effective. Here, pilot systems with the storage media volcanic rock and molten salt are in operation or planned.

Heat storage systems are also used in the context of cogeneration in order to be able to guarantee the supply of thermal energy regardless of the current generation of electricity.

Cryogenic energy storage

→ Main article : Cryogenic energy storage

In this process, air or nitrogen is cooled down to −195 ° C using the Linde process and can be stored in a vacuum vessel at atmospheric pressure. When converting to gas, the associated sharp increase in volume and pressure is used to drive a turbine to generate electricity. The technology is already being used in pilot operation in a British power station.

Comparison of storage power plants

The following list contains some exemplary storage power plants and is intended to give an overview of tried and tested and new technologies.

Surname	Type	Energy form	status	country	completion position	Lifespan in years	Power in MW	Capacity in MWh	Wirkungs- degree	Investment in millions of euros	Response time in minutes
Goldisthal pumped storage plant	pumped storage power plant	Position energy	Commercial operation		2003	30-100	1,060	8,500	80%	623	1.63
McIntosh Power Plant	Compressed air storage power plant	Air pressure	Commercial operation		1991	28 so far	110	2,860	54%	?	14th
Hornsdale wind farm	Battery storage power plant	Lithium-ion	Commercial operation		2017	?	100	129	90-98%	100	<1
Hamburg-Altenwerder heat storage facility	High temperature heat storage	Heat in 1000 tons of volcanic rock	Pilot project		2019	?	?	130	22%; 45% targeted when ready for the market	?	a few minutes
M partner SWM	Flywheel storage power plant	Flywheel DuraStor	Pilot project		2010	20th	0.6	0.1	85-90%	?	<1
Rail Energy Storage Project	Lift storage power plant	Electric powered train	Pilot project		2018	30-40	50	12.5	80%	50.05	?

Notes: The service life of PSWs for turbines and pumps is 30–60 years; for reservoirs and dams at 80–100 years.

literature

• Michael Sterner , Ingo Stadler (ed.): Energy storage. Need, technologies, integration. 2nd edition, Berlin / Heidelberg 2017, ISBN 978-3-662-48893-5 .
• Florian Hannig et al .: Status and development potential of storage technologies for electrical energy - Derivation of requirements and effects on the capital goods industry . Short version of the final report BMWi contract study 08/28. BMWi , August 28, 2009 ( full text as PDF on bmwi.de).
• Renewable Energy Agency: Store electricity. Renews Special No. 29 (2010) ( Memento from October 25, 2010 in the Internet Archive )
• Adolf J. Schwab: Electrical energy systems: generation, transport, transmission and distribution of electrical energy . 2nd Edition. Springer, 2009, ISBN 978-3-540-92226-1 .
• Horst Völz : Storage as the basis for everything. Shaker Verlag, Düren 2019, ISBN 978-3-8440-6964-8 .

Web links

Wiktionary: Speichererkraftwerk  - explanations of meanings, word origins, synonyms, translations

Individual evidence

1. ↑ heise online: Tesla's giant battery in Australia is paying off. Retrieved May 24, 2019 . 
2. ↑ A. Moser, N. Red Ring, W. Wellßow, H. Pluntke: Additional needs for storing 2020 at the earliest . Electrical engineering & information technology 130, (2013) 75–80, p. 79. doi : 10.1007 / s00502-013-0136-2
3. ↑ Michael Sterner , Ingo Stadler: Energy storage - requirements, technologies, integration . Berlin / Heidelberg 2014, p. 95.
4. ↑ renewablesb2b.com: "The approximately 1250 Norwegian hydropower plants produce an average of 126.6 TWh per year (2000-2010) in years with normal rainfall.", Accessed on May 1, 2014
5. ↑ Pumped Hydro ( Memento from June 15, 2010 in the Internet Archive ), technical description, (English)
6. ↑ forschung-energiespeicher.info: Ball pump storage under water , accessed on February 27, 2016
7. ↑ ingenieur.de: Concrete balls in Lake Constance are supposed to store wind power , accessed on September 23, 2019
8. ↑ Train wagons store electricity ingenieur.de, May 30, 2016, accessed on September 23, 2019.
9. ↑ Peter Höllrigl: New super battery - Can this tower secure our energy future? In: srf.ch . January 3, 2020, accessed January 3, 2020 . 
10. ↑ Flywheel storage power plant in Hazle Township, Pennsylvania (USA), operator side beaconpower
11. ↑ Mitsubishi Installs 50MW Energy Storage System to Japanese Power Company In: globalspec.com. March 11, 2016, accessed January 28, 2017.
12. ↑ Study: The storage market is growing rapidly . In: IWR , August 25, 2016. Retrieved August 25, 2016.
13. ↑ Where can the green energy be parked? . In: Frankfurter Allgemeine Zeitung , May 21, 2019. Accessed May 21, 2019.
14. ↑ ingenieur.de: "Engineers store energy in giant underwater balloons", accessed on March 4, 2016
15. ↑ energyload.eu: "Hydrostor balloon energy storage: competition for batteries?", Accessed on March 4, 2016
16. ↑ pv-magazine.de : Dance on the volcano: Siemens Gamesa puts new electrothermal energy storage systems into operation in Hamburg , accessed on September 27, 2019.
17. ↑ energate-messenger.de : RWE plans heat storage power plant in the Rheinische Revier , accessed on September 27, 2019.
18. ↑ kraftwerkforschung.info : High-temperature heat storage for flexible combined cycle power plants , accessed on September 27, 2019.
19. ↑ Hamburg Energie: Siemens Gamesa puts innovative electrothermal energy storage systems into operation. September 16, 2019, accessed September 20, 2019 . 
20. ↑ BMWi: volcanic rock stores wind power. August 20, 2019. Retrieved September 22, 2019 . 
21. ^ Aachener Zeitung: Stadtwerke München market Jülich storage facility. November 9, 2015, accessed September 22, 2019 . 
22. ↑ ingenieur.de: This flywheel stores wind energy , accessed on September 23, 2019.
23. ^ ARES Nevada. Retrieved September 23, 2019 . 
24. ^ FfE: Expert opinion on the profitability of pumped storage power plants. September 1, 2014, accessed September 20, 2019 .