Belles_Modern Energy Review 01/03/2010 17:08 Page 33
Stockpiling Electrons
Other storage devices that look a little like batteries, although they are
Figure 1: Energy Storage Technologies Span a Wide Range of Capacities,
actually very different, include ultracapacitors and superconducting
Power Outputs and Degrees of Technological Maturity
magnetic energy storage (SMES) devices.
Compressed air
Ultracapacitors use electrodes made from nanoscale carbon to
Metal air
Flow batteries
batteries
store electricity directly, rather than converting it to chemical energy,
Hours
Pumped storage
as batteries do. They are ideal for delivering large currents over
Sodium–sulphur batteries
short time-scales and, unlike batteries, they can operate for millions
Advanced batteries
of cycles. SMES devices store energy in the form of magnetic
fields. They are robust and can deliver large amounts of power for
Lead–acid batteries
short periods. Supercapacitors
Energy management
Maximum discharge
High-energy flywheels
Spinning reserve
Flywheels
and grid stabilityMinutes
Modular compressed air
Spinning flywheels that store kinetic energy offer robustness, high
efficiency and an operating life measured in millions of cycles, says Power quality and back-up power
Damien Scott of UK company Williams Hybrid Power. Made from
carbon fibre composite loaded with magnetic particles, Williams’
Low-energy flywheels SMES
Seconds
flywheels spin in a vacuum at up to 40,000rpm, associated with
large-scale use of batteries in power systems.
10MW 100MW1MW
0kW 10kW 100kW
Power rating
“I do not think static batteries will be economical in the foreseeable
Source: Electricity Storage Association.
future,” says Aksel Hauge Petersen of Danish power company DONG
Energy “Within a few years we expect to have half a million electric problems for the grid, not solve them,” says Henrik Vikelgaard from
vehicles in Denmark. Just 100,000 vehicles at 20kW each would give Vestas. “Feeding power from electric vehicles back to the grid would
20GW, which is more than Denmark’s entire generating capacity. certainly be useful, but the current distribution grid is not built for
Combined with an intelligent grid, DONG Energy believes this is the that.” Since battery life is limited to a certain number of
answer to energy storage.” Others are less optimistic. “If we are not charge–discharge cycles, car owners would have to be compensated
careful, charging electric vehicles overnight will create capacity for the reduced life, he points out. n
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