Energy storage, both on domestic and industrial levels, is vital in enabling greater penetration
of renewable electricity generation and development of smart grids, and to reduce the need for
fossil fuel peaking plants. According to a Technology Innovation Needs Assessment (TINA)
by the Low Carbon Innovation Group published in Aug 2012, 27.4 GW of grid-connected
energy storage is needed to enable UK achieving its carbon reduction targets for 2050.
Realising this capacity is rather ambitious given today’s installed capacity being less than 3
GW, mainly dominated by large-scale pumped hydro storage (PHS). There is limited space to
expand PHS in the UK, so other options for storage need to be explored. Grid-connected
domestic energy storage (GCD ES) can offer an important contribution to realising 2050
targets, as much as 10 GW equivalent to two million household installations, predicted by
TINA.
The majority of GCD ES solutions are based on batteries and their associated AC-DC power
electronics inverters. Existing battery and inverter technologies are expensive and have low
efficiency, preventing widespread adoption of GCD ES. Commercially available inverters for
energy storage applications are made from Silicon-based Insulated Gate Bipolar Transistor (Si-
IGBT) devices, which are costly and have moderate efficiency. The inverter is a major
component of a GCD ES system and hence, its cost reduction and efficiency improvement
will directly affect the system economics and net ‘cost of energy’.
Zagres, spun out from Cambridge University Engineering Department, has developed a new
inverter technology based on Gallium Nitride High-Electron-Mobility Transistor (GaN
HEMT) devices, which promises significant improvements over Si-IGBT based inverters; its
exploitation can reduce the cost and size of energy storage inverters and increase power
conversion efficiency, contributing towards achieving more cost-effective energy storage
systems.