Cryogenic energy storage
Cryogenic energy storage ( Cryogenic Energy Storage / CES , also Liquid Air Energy Storage / LAES ) refers to the use of low-temperature ( cryogenic ) liquids, such as liquid air or liquid nitrogen , as energy storage . Both cryogens are already used in vehicle drives. The inventor Peter Dearman originally developed a vehicle powered by liquid air, but then also used this technology for a network energy storage system . The technology is being piloted at a UK power plant.
history
Between 1899 and 1902, a liquid air powered vehicle called Liquid Air was developed. More recently, a liquid nitrogen powered vehicle has been built. Peter Dearman, a private inventor from Hertfordshire, England, first developed a vehicle powered by liquid air and then used this technology for a network energy storage system. The Dearman engine differs from previous nitrogen engines in that the nitrogen is heated in combination with the heat exchange fluid inside the cylinder.
Network energy storage
Procedure
In low-load phases, when electricity is particularly cheap (usually at night), this electricity can be used to cool air from the ambient temperature to −195 ° C using the Linde process and thus liquefy it. Liquid air only takes up a thousandth of the original volume and can be stored for a long time in a large vacuum vessel at atmospheric pressure . When there is a high demand for electricity, liquid air is pumped at high pressure into a heat exchanger that serves as a boiler. Air at ambient temperature from the atmosphere or hot water from an industrial heat source are used to heat the liquid and bring it back to its gaseous state. The associated strong increase in volume and pressure is used to drive a turbine to generate electricity.
Efficiency
Taken alone, the process achieves an efficiency of only 25%. However, this value can be increased significantly (to around 50%) if the process is combined with a cold store , such as a large gravel bed, to absorb the cold generated when the cryogen is evaporated. The cold can then be reused in the next cooling cycle.
To further increase the efficiency, the process can be used in conjunction with a power plant or another source of waste heat, i.e. with the supply of heat that would otherwise be released into the environment. Highview Power Storage estimates that a round trip efficiency (AC to AC) of 70% would be achievable if free waste heat at 115 ° C was available. However, this figure has not yet been verified or confirmed by independent institutions.
Currently, excess nitrogen gas is a by-product of the production of oxygen . This can be liquefied if necessary. The oxygen can be used in coal-fired power plants with oxygen combustion and enables CO2 capture and sequestration. The cryogenic distillation of air is currently the only commercially viable technology for oxygen production on a large scale.
Pilot plant
A cryogenic energy storage pilot system with 300 kW and a storage capacity of 2.5 MWh developed by researchers at the University of Leeds and Highview Power has been in operation at a biomass power plant in Slough, UK, since 2010. It uses liquid air, the energy store and waste heat to strengthen the thermal re-expansion of the air. Carbon dioxide and water were removed from the liquid air, as these would freeze at the storage temperature. The efficiency is currently less than 15 percent. But engineers reckon with an efficiency of approx. 60% for the next generation of LAES based on knowledge gained with the help of the existing system. The system is based on a proven technology that is safely used in many industrial processes. No rare raw materials or expensive components are required for production. "The system is based on common industrial components ..., lasts for decades and can be serviced with the simplest of means," says Tim Fox, Head of Energy at the Institution of Mechanical Engineers (IMechE).
Study "Liquid air in energy and transport applications"
On May 9, 2013, the Center for Low Carbon Future published a study with the original title "Liquid Air in the energy and transport systems: Opportunities for industry and innovation in the UK". a. Arup , Ricardo , the Messer Group , National Grid and leading UK universities contributed. In this study, liquid air is treated as a possible solution to the problem of energy storage and opportunities for industry in the field of energy and transportation systems.
Individual evidence
- ^ English description of the pilot project from Highview Power Storage . Retrieved July 8, 2013.
- ^ Report by BBC environmental analyst Roger Harrabin in English. Retrieved July 8, 2013.
- ↑ Description of the technology of the Dearman motor ( Memento of the original from October 22, 2012 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. in english. Retrieved July 8, 2013.
- ↑ Description of the procedure ( Memento of the original from June 24, 2013 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. on the website of Highview Power Storage (English). Retrieved July 8, 2013.
- ↑ Summary of the report ( Memento of the original from October 8, 2013 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. on the website of the Messer Group. Retrieved July 8, 2013.
- ↑ Download the full report "Liquid Air in the energy and transport systems: Opportunities for industry and innovation in the UK" ( Memento of the original from January 31, 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. (PDF; 4.5 MB). Retrieved July 8, 2013.
