Wind energy storage technologies - Wind Power Generation and Wind Turbine Design - page 662

or by a storage system. Wind energy is inherently intermittent, variable and
non-dispatchable (cannot be switched on 'on demand'). Consequently, the need
for such backup sources of power increases as the proportion of wind generation
on the system increases. To reduce fuel demands, it is desirable that the backup source
is a storage facility rather than further primary generation. In this chapter we will dis-
cuss the various options for electricity storage including both large-scale centralised
storage and smaller-scale distributed storage.
Storage systems such as PHES have been in use since 1929 [1], primarily to level
the daily load on the electricity network between night and day. As the electricity
sector is undergoing a lot of change, energy storage is becoming a realistic option [2]
for: restructuring the electricity market; integrating renewable resources; improving
power quality; aiding the shift towards distributed energy; and helping the network
operate under more stringent environmental requirements. In addition, energy stor-
age can optimise the existing generation and transmission infrastructures whilst also
preventing expensive upgrades. Power fl uctuations from renewable resources will
prevent their large-scale penetration into the network. However energy storage
devices can manage these irregularities and thus aid the amalgamation of renewable
technologies. In relation to conventional power production, energy storage devices
can improve overall power quality and reliability, which is becoming more important
for modern commercial applications. Finally, energy storage devices can reduce
emissions by aiding the transition to newer, cleaner technologies such as renewable
resources and the hydrogen economy. Therefore, Kyoto obligations can be met (and
penalties avoided). A number of obstacles have hampered the commercialization of
energy storage devices including: a lack of experience - a number of demonstration
projects will be required to increase customer's confi dence; inconclusive benefi ts -
consumers do not understand what exactly are the benefi ts of energy storage in terms
of savings and also power quality; high capital costs - this is clearly an issue when
the fi rst two disadvantages are considered; responsibility for cost - developers view
storage as 'grid infrastructure' whereas the Transmission System Operator (TSO)
views it as part of the renewable energy plant.
However, as renewable resources and power quality become increasingly
important, costs and concerns regarding energy storage technologies are expected
to decline. This chapter identifi es the numerous different types of energy storage
devices currently available. The parameters used to describe an energy storage
device and the applications they fulfi l are explored fi rst. This is followed by an
analysis of each energy storage technology currently available indicating their:
operation and the advantages; applications; cost; disadvantages; future; and
fi nally, a brief comparison of the various technologies is provided.

2 Parameters of an energy storage device

Below is a list of parameters used to describe an energy storage device. These will
be used throughout the chapter:

• Power capacity is the maximum instantaneous output that an energy storage

device can provide, usually measured in kilowatts (kW) or megawatts (MW).