Variety of use for large lithium-ion batteries expands
By Dr Peter Harrop, chairman, IDTechExPower Supply / Management Engineering
Very large lithium-ion battery banks were largely unknown ten years ago. Now, it is tough to keep up with the variety of uses for them. On ships, where there were no such batteries, we are starting to see 1-5 MWh banks. Autonomous underwater vehicles, mining trucks and buses can sport ones of up to 350 kWh but it is in stationary applications that really big facilities have arrived. Here there is a multiplier effect with Li-ion gaining market share in growth markets.
In the case of the relatively new market for very large, ground-based lithium-ion battery packs for such things as grid peak shaving, weight is not a primary issues, volume can matter somewhat but life, cost over life, performance and reliability matter greatly. For example, Toshiba is serving this market with its titanium dioxide anodes conferring good Li-ion cycle life. The applications include balancing and emergency power supplies for grid outage.
20 MW giants
The UK is to test its first battery system to provide grid-frequency after a partnership between energy utility firm National Grid and UK based Renewable Energy Systems (RES) was announced in June 2016. The 20MW battery storage system, equivalent to up to 1000 pure electric cars’ batteries, follows six similar ones being installed in the US by REL. It will provide a dynamic frequency response service with a second of a deviation, either higher or lower than 50Hz, being detected. The work is a testbed to National Grid’s upcoming tender for 200MW of Enhanced Frequency Response in Great Britain.
RES is technology agnostic when it comes to selecting energy storage systems. However, having used lithium-ion for all of its 74MW projects currently operating, there is a strong possibility that lithium-ion will be used for this contract, says the company. This service and the forthcoming Enhanced Frequency Response service will support the network as the UK transitions to a generation mix with greater levels of low cost renewable energy. Competition for large land-based batteries for grid-based applications comes from vanadium flow batteries. Further down the line, Central Electrochemical Research Institute (CECRI) India will demonstrate a zinc bromide redox flow battery for grid level storage of renewable energy in 2019.
When it comes to large banks of energy storage alongside the railway track for grabbing regenerated electricity on braking, lithium-ion batteries are losing business to “fit and forget” supercapacitors that better harness the huge surges involved. For example, Meidensha took a $25 million order for part of the Hong Kong Railway regeneration using supercapacitors.
To a lesser extent, this is true of very fast charging of buses in transit using gantries at bus stops, whether the buses are propelled by lithium-ion batteries with supercapacitors to protect them or they simply use supercapacitors and are charged faster and more often. In both cases the land-based facility tends to use lithium-ion batteries with supercapacitors across them.
Lithium-ion success is ongoing
Despite all this the penetration of large lithium-ion battery packs into grid and even microgrid applications is inexorable. There is even talk of creating microgrids in parts of cities for those having a problem with the cost and reliability of the grid and reluctant to use diesel gensets with their pollution, cost noise and reliability problems. The global base of diesel gensets is at least 600 GW and the ecological agenda calls for them all to be replaced eventually, the alternatives including solar on buildings, in roads and in parking lot surfaces plus wind turbines and airborne wind energy in the form of autonomous kites and tethered quadcopters generating electricity.
All options are intermittent and energy storage essential. Though multiple harvesting, each part with different intermittency, balances things somewhat, reducing the amount of storage required, storage is still needed if only because the power is not always produced at the right time of day.
Storage time and bad lead
Batteries can store the generated electricity for a long time – supercapacitors less so. The growing intolerance of lead pollution helps lithium-ion, with lead acid battery banks increasingly unacceptable. For example India is seeking to replace lead acid in railways and elsewhere.