Solar battery

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Solar-powered battery for an electric fence that is independent of the mains

Solar batteries , also known as solar accumulators or solar accumulators for short , are customary names for accumulators that have been specially developed for use in photovoltaic systems or are simply used for this purpose. They are used especially in stand-alone systems to store the energy obtained with solar modules and as buffer batteries when operating larger consumers. The term is often used generally for batteries built into solar power applications, even if they are not specified for this.

The term solar battery also refers to a large number of solar cells arranged over a large area that convert solar energy into electrical energy. These are also known in connection with artificial earth satellites, whereby solar sails that can look similar on the surface and are used for propulsion are generally not solar cells.

Used accumulators

The most common type of battery used for solar batteries in the past was the lead-acid battery . The low price per storable amount of energy, the achievable freedom from maintenance, the low self-discharge and the comparatively high efficiency of around 80% spoke in favor of its use . The losses in lead-acid batteries can be partly explained by the outgassing of oxyhydrogen gas during the charge. The outgassing is reduced with maintenance-free lead-gel batteries.

Solar lead accumulators differ in their internal mechanical structure from other lead accumulators; they are optimized for a particularly long service life, cycle stability and behavior in the event of deep discharge. Typical are cycle numbers of 1200 (with a discharge depth of approx. 80%) up to a remaining capacity of 80%, since from then on a battery is considered defective. Maintenance-free lead-gel batteries have the advantage that no or only a minimal acid stratification is formed, but they only allow a significantly lower number of cycles of 400 to 600. An additional circulation of the acid completely prevents the acid stratification in lead batteries. This is particularly important in stationary operation.

In some cases, so-called forklift batteries are also used, which are rechargeable batteries that are usually used as traction batteries in forklifts . These are also lead-acid batteries, but with 1500 charging cycles and a favorable price-performance ratio.

Lithium-ion accumulators have recently also been used as solar batteries, which is due to the sharp fall in the prices of lithium-ion batteries (see also battery prices ). In addition, lithium-ion batteries sometimes have a very high cycle stability of more than 10,000 charge and discharge cycles and a long service life of up to 20 years. In particular, lithium iron phosphate accumulators are also used, which are characterized by high cycle stability, high safety and low price and are also used as traction batteries . In the fourth quarter of 2015, 90 percent of all supported storage systems in Germany were lithium batteries.

Used batteries from electric cars can also be used as solar batteries , which no longer have enough capacity for their original purpose, but are still sufficient as solar batteries. Such batteries often still have 70 to 80% of their original capacity, but are significantly cheaper than brand-new solar batteries.

In Germany, solutions have also been implemented in which homeowners with solar systems use the battery of their own electric car to store electricity. The green electricity supplier Lichtblick connects the solar batteries of its customers to a swarm battery, which is then controlled centrally. The customers receive money for the provision of their storage.

PV Magazin and CARMEN eV each created a market overview of the available electricity storage systems.

Funding programs for solar batteries

In German-speaking countries there are currently some regional funding programs for the purchase of solar batteries and in Germany there is a nationwide program. These funding programs are presented below.

Federal program in Germany (discontinued)

The funding program 275 “Renewable Energies - Storage” of the state credit institute for reconstruction (KfW) supported the use of stationary battery storage systems in connection with a photovoltaic system, which are connected to the electrical network, through low-interest loans from the KfW and through repayment grants. The funding program ran from May 1, 2013 to December 31, 2018. The aim was for owners of solar systems to rely more on their own consumption of solar energy. The starting volume was 25 million euros. The subsidy program only subsidized newly built solar systems (up to 30%, a maximum of 600 euros per kWh) or subsequently installed solar batteries for the electricity produced by the solar system.

By August 2018, around 100,000 solar batteries had been put into operation across Germany. At the end of 2017 there were a good 80,000 solar batteries in Germany, the increase in 2017 was more than 30,000 systems. According to BSW-Solar, the costs for solar batteries were halved within 4 years. From 2014 to 2016 costs fell by around 40%, and further cost reductions of the same size are expected.

State funding program in the Free State of Saxony (discontinued)

In Saxony, decentralized energy storage systems for renewable energies have been subsidized with up to 75% up to a maximum of 50,000 euros since October 1, 2013. The corresponding funding program of the SAB - Sächsische Aufbaubank was called "Innovative decentralized power generation and storage". Funded were decentralized electricity storage systems, which stored the electricity produced by a solar system, as well as model projects in which the solar electricity was not remunerated via the EEG, but instead aimed at marketing outside the EEG. The amount of funding was between 50% and 75%. At least 60% of the self-produced solar power had to be consumed and the solar battery had to have a storage capacity of at least 2 kWh. For the minimum requirement of 50%, a maximum of 40% of the solar power produced could be fed into the public power grid. The solar battery had to have a capacity of at least 2 kWh and the performance data of the solar battery had to be made available to the Saxon Energy Agency for three years. This subsidy was increased to 60% if an innovative control was also used, with which an intelligent control of electrical consumers is possible. At least 10% of the annual electricity consumption at the investment site had to be controllable. If the data was collected every five minutes instead of 15 minutes and the data was made available to third parties on the Internet for at least three years, then 70% of the costs of the solar battery were eligible. The maximum funding amount for decentralized electricity storage was 30,000 euros. A 75% subsidy of up to 50,000 euros was given to model projects for the independent operation of photovoltaic systems. For this purpose, in addition to the previously mentioned requirements, a concept had to be developed through which an innovative improvement in the grid integration of the solar system and the solar battery was achieved. In addition, the feed-in tariff from the EEG had to be waived and an exchange of electricity with the public power grid had to be guaranteed (no support for self-sufficient solar island systems).

Funding program of the state of Brandenburg

Since July 27, 2018, the state of Brandenburg has been promoting the acquisition, installation and delivery of electricity storage units with a usable capacity of 2.0 kWh as part of its 1,000 storage system . The 50% subsidy is granted to homeowners residing in Brandenburg with a grant amount of EUR 2,500 or more and can amount to a maximum of EUR 7,000. The residential building for which funding is requested may only be used by itself and for residential purposes. The sponsor of the program, which runs until December 31, 2022, is the Investment Bank of the State of Brandenburg, to which applications can be submitted using an electronic form or in writing. Funding is based on the reimbursement principle in the form of a non-repayable grant. The service must be paid for by bank transfer after the notification has been received, and proof of payment must be provided by invoice and bank statement.

The decentralized energy storage is eligible on condition that the solar generator connected to the storage does not feed more than 60% of its nominal output into the grid under standard test conditions . In addition, through the installation of the storage tank, the proportion of self-consumption related to the annual consumption and the degree of self-sufficiency must be at least 50%.

Promotion of solar batteries in Austria

Electricity storage is currently (as of May 2015) subsidized in Styria and Upper Austria. Electricity storage systems for the self-consumption optimization of photovoltaic systems in single and two-family houses are funded. The funding amounts to 500 or 400 euros per installed kilowatt hour of storage capacity. Up to a size of five or six kilowatt hours is supported.

economics

Whether the installation of a private electricity storage system is economically viable can be determined by comparing your own electricity costs with the sum of the generation costs for the solar electricity plus the storage costs. The amount of the storage costs depends on the investment costs per kWh storage capacity and the service life of the system (operating time in years). With the optimistic assumption of a service life of 20 years and favorable framework conditions, the use of a solar battery can make economic sense. See also network parity .

Alternative thermal storage

An alternative to storing solar power in accumulators is to store the energy in thermal storage . For this purpose z. B. solar power is used with a heat pump to heat domestic water, which is then stored in a thermal storage tank (similar to an insulating jug ). The thermal energy stored in this way is then not converted back into electrical energy, but fed into the heating system. The costs for useful heat can thus be reduced from around 8 cents / kWh to around 2 cents / kWh compared to oil and gas heating (see operating costs of heat pump heating systems ).

See also

literature

  • Philipp Brückmann: Autonomous power supply: Design and practice of power supply systems with battery storage . Ökobuch, Staufen near Freiburg 2007, ISBN 978-3-936896-28-2 .
  • Thomas Riegler: Using solar power efficiently: Everything about solar panels, solar batteries, charge controllers and inverters. Verlag für Technik und Handwerk, Baden-Baden 2008, ISBN 978-3-88180-847-7 (= radio technology consultant ).
  • E. Schoop: Stationary battery systems: Design, installation and maintenance , Huss, Berlin, 2nd edition from 2018, ISBN 978-3-341-01633-6
  • B. Riegel, W. Giller: Lead batteries as stationary application in competition with stationary lithium-ion batteries. In: E. Fahlbusch (Ed.): Batteries as energy storage: Examples, strategies, solutions , Beuth, Berlin / Vienna / Zurich 2015, ISBN 978-3-410-24478-3 , pp. 353–374

Web links

Individual evidence

  1. ↑ Solar battery for self-sufficiency ( Memento of the original from September 1, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed November 14, 2013. @1@ 2Template: Webachiv / IABot / ratgeber.immowelt.de
  2. ↑ solar-batterie.com ( Memento of the original from February 3, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. “We use armored plate batteries for energy storage, which are known from traction applications. According to DIN EN60254, these batteries have 1,500 charging cycles. ”(Sentence is from the start page), see also www.gabelstaplerbatterie.com to indicate that these are forklift batteries , accessed on March 13, 2014. @1@ 2Template: Webachiv / IABot / www.solar-batterie.com
  3. ↑ solarserver.de ( Memento of the original from April 11, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. "REM GmbH (Rottenburg) has launched a lithium-ion energy storage device for residential buildings and small businesses (...)", accessed on February 24, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  4. ↑ a b solarserver.de "(...) Frankensolar (Nuremberg) is breaking new ground in modern and efficient energy storage with an innovative product combination of Nedap PowerRouter and Sony" Fortelion "lithium-ion battery." and "Due to the Fortelion lithium iron phosphate technology, this battery is one of the safest batteries on the market: its insensitivity to external influences and various integrated safety mechanisms support a service life of up to 20 years." and "The technical data have so far been unmatched: Even after 8,000 loading and unloading, at 100% depth of discharge (DOD), 70 percent of the original capacity is still available", accessed on March 23, 2019.
  5. ↑ Marcel Wilka: Investigations of polarization effects on lithium-ion batteries and their influence on safety, aging and other application-relevant properties . Ulm 2014, doi : 10.18725 / OPARU-2637 (dissertation, Ulm University).
  6. ↑ solarserver.de ( Memento of the original from March 30, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. "The tests exposed the batteries to extreme loads. Over a period of 5 years with a depth of discharge of 60%, more than 10,000 equivalent full cycles were achieved." and "Simulations based on our laboratory results and those of our colleagues at ZSW show that, taking into account both aging processes, the batteries in the BPT-S 5 Hybrid can be used for up to 20 years", accessed on March 29, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  7. ↑ solarserver.de ( Memento of the original from June 9, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. "According to the manufacturer, the cells have an expected service life of 20 years and can be charged up to 15,000 times.", Accessed on March 29, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  8. ↑ solarspeicher-sonnenenergie.de ( Memento from April 9, 2014 in the web archive archive.today ) “Lithium-Iron-Phosphate Technology, LiFePO 4 ; 7000 charge cycles ", accessed on April 24, 2014.
  9. ↑ solarserver.de ( Memento of the original from May 20, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. "Mastervolt presents photovoltaic storage systems for residential buildings at Intersolar Europe", accessed on May 18, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  10. ↑ solarserver.de "The solar battery continues to rely on the safe and efficient lithium iron phosphate technology ...", accessed on June 3, 2014.
  11. ↑ pv-magazine.de "In Q4 2015, 90 percent of the systems supported had lithium batteries.", Accessed on March 18, 2016.
  12. ↑ Shijie Tong et al .: Demonstration of reusing electric vehicle battery for solar energy storage and demand side management . In: Journal of Energy Storage . tape 11 , 2017, p. 200–210 , doi : 10.1016 / j.est.2017.03.003 .
  13. ↑ manager-magazin.de electric car rebel Karabag: "Our electric car concept is cheaper than a conventional car"
  14. ↑ solarserver.de ( Memento of the original from August 19, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. LichtBlick integrates photovoltaic storage into the electricity market @1@ 2Template: Webachiv / IABot / www.solarserver.de
  15. ↑ www.pv-magazine.de/marktuebersichten/batteriespeicher/speicher , pv-magazine.de, accessed on June 26, 2018
  16. ↑ CARMEN - market overview for battery storage systems , carmen-ev.de, accessed on July 1, 2014
  17. ↑ KfW funding for solar batteries , accessed on May 30, 2014.
  18. ↑ 100,000. Photovoltaic storage system put into operation in Germany . In: PV-Magazine , August 28, 2018. Retrieved August 29, 2018.
  19. ↑ BSW-Solar: 80,000 storage tanks installed in Germany . In: PV-Magazine , March 16, 2018. Retrieved March 19, 2018.
  20. ↑ Number of installed memory rises to 50,000 devices . In: Renewable Energies. Das Magazin , March 13, 2017. Retrieved March 13, 2017.
  21. ↑ Funding of energy storage in Saxony by the SAB ( Memento of November 10, 2014 in the Internet Archive ), accessed on May 30, 2014.
  22. ↑ Up to 75% funding for electricity storage systems in Saxony , accessed on May 30, 2014.
  23. ↑ 1,000 storage program starts: Brandenburg supports private investments in electricity storage , accessed on August 7, 2018.
  24. ↑ 1000 memory program on ilb.de.
  25. ↑ pvaustria - Funding situation in Austria ( Memento of the original from May 18, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed on May 11, 2015. @1@ 2Template: Webachiv / IABot / www.pvaustria.at
  26. ↑ Hermann-Josef Tenhagen: Inexpensive batteries for the basement: This is how you store electricity - and make yourself independent of corporations . In: Spiegel Online . July 28, 2018 ( spiegel.de [accessed July 28, 2018]).
  27. ↑ Solar power on your own roof: This is how it works - financial tip . In: Ines Rutschmann (Ed.): Finanztip . July 9, 2018 ( finanztip.de [accessed July 28, 2018]).
  28. ↑ solarserver.de ( Memento of the original from April 14, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Photovoltaics and thermal energy storage, accessed on March 15, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  29. ↑ solarserver.de ( Memento of the original from May 24, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Bosch presents innovative solutions for photovoltaic systems in combination with electricity storage and heat pumps at Intersolar Europe 2014, accessed on May 24, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de
  30. ↑ solarserver.de ( Memento of the original from June 6, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ZSW simulates intelligent management of decentralized photovoltaic storage systems for higher self-consumption of solar power and grid optimization, accessed on June 3, 2014. @1@ 2Template: Webachiv / IABot / www.solarserver.de