Wind energy storage technologies - Wind Power Generation and Wind Turbine Design - page 667

world - roughly 3% of the world's global generating capacity. Individual facilities
can store up to 15 GWh of electrical energy from in plant with power ratings from
30 to 4000 MW [2].
4.1.1 Applications of PHES
Similar to large storage capacities, PHES also has a fast reaction time, making
it ideal for load levelling applications, where the plant can vary its effective load
on the system from the full name plate rating in the positive direction (pumping)
to the full name plate rating in the negative direction (generating) (see Fig. 3).
Facilities can have a reaction time as short as 10 min or less from complete shut-
down (or from full reversal of operation) to full power [3]. In addition, if kept on
standby, full power can even be reached within 10-30 s.
Also, with the recent introduction of variable speed machines, PHES systems can
now be used for frequency regulation in both pumping and generation modes (this
has always been available in generating mode). This allows PHES units to absorb
power in a more cost-effective manner that not only makes the facility more useful,
but also improves the effi ciency by approximately 3% [3] and extends the life of the
facility. PHES can also be used for peak generation and black starts (start generating
without access to a main frequency set by other units on the grid) due to its large
power capacity and suffi cient discharge time. Finally, PHES provides a load for
base-load generating facilities during off-peak production, hence, cycling these units
can be avoided which improves their lifetime as well as their effi ciency.
4.1.2 Cost of PHES
Cost ranges from $600/kW [2] to upwards of $2000/kW [3], depending on a number
of factors such as size, location and connection to the power grid.
Figure 3: Output from a pumped-hydroelectric storage facility [ 5 ].