Storelectric, a UK start-up, intends to bring to market a compressed air energy storage (CAES) technology that the developer claims is capable of efficiencies of 70%, or more, for bulk storage applications.
CAES systems convert electrical energy into high-pressure compressed air that can be used at a later time for electricity generation. Potentially, CAES systems complement large-scale renewables such as wind by storing excess electricity produced when the wind is blowing and releasing it for electricity generation at times of peak demand.
The 290 MW Huntorf facility in Germany built in the late 1970s, and one of only two utility-scale CAES plants in operation, uses nuclear plant-generated night-time power for compression and produces peak power during the day.
Huntorf makes use of two underground salt caverns, which are filled up over several hours and when electricity is needed. The compressed air is released and is heated by combusting natural gas to get the air to expand to drive a huge turbine that generates electricity for two hours, before the process can start over again.
Like the Huntorf facility, Storelectric (www.storelectric.com) will exploit disused underground salt caverns to store the air, of which there are many in Britain. For CAES to be really economic, developers in the field have been focused on increasing the efficiency of CAES by holding onto and reusing the stored thermal energy to heat the air for expansion, rather than waste this energy and burn fuel, which adds to the cost of the recovered electrical energy and makes the sustainable benefits of such a storage technique questionable.
Storelectric’s technology, on paper, could potentially increase CAES efficiency for bulk storage applications from 42-50% to 70-85%. The company has identified two potential methods, which it is in the process of patenting, of storing the thermal energy and re-combining it with the air by applying known and reliable technologies from other industries and has also identified from other industries existing equipment, proven and in production, that will turn the compressed air efficiently into power. The firm has identified two fields of salt caverns that are suitable in the UK, Preesall and the Cheshire Basin.
The company is looking to raise public funding for a prototype, potentially under the Department Energy and Climate Change’s (DECC) energy entrepreneurs fund, for low carbon technologies.
By mid-2015 Storelectric wants to construct a pilot plant 25-40 MW in size that would cost in the region of £28 million, using off-the-shelf equipment, on a part-used cavern, focusing on the connections and links between subsystems and the control systems, and making these scalable for a plant upgrade to 250-500 MW. The company has been in talks with a range of companies, including owners of salt assets such as Ineos and British Salt and engineering services businesses such as Costain and as well as multinational players in power generation and large-scale energy storage such as Siemens and Bosch.
The UK’s Electricity Storage Network (ESN) advocates that energy storage will have a crucial role to play in Britain’s power networks in the provision of an economic and secure supply of power. The ESN proposes a minimum of 2 GW of new network connected electricity storage by the year 2020 for the UK. To reach this target would require installing about 300 MW of new storage each year. According to the ESN (www.electricitystorage.co.uk) director Anthony Price: ‘There is the opportunity for different types of storage technologies in the system from lots of individual small-scale distributed storage, supplemented with some large-size, bulk storage such as CAES. However, until we have a strategy that recognises storage as part of the mix in the UK, then all developers, regardless of technology, face the same challenge.’
The lack of market mechanism makes investing in energy storage in the UK a prospect that many potential investors are not prepared to risk financing. Policies, targets and subsidies, which have been critical in the UK’s adoption of renewable energy generation, would also provide confidence for energy storage developers and potential investors.