3.8. Fluctuations and storage http://www.ck12.org
Figure 26.5:How pumped storage pays for itself. Electricity prices, in £ per MWh, on three days in 2006 and 2007.
Britain has four pumped storage facilities, which can store 30 GWh between them (table, figure 26.6). They are
typically used to store excess electricity at night, then return it during the day, especially at moments of peak demand
- a profitable business, as figure 26.5 shows. The Dinorwig power station – an astonishing cathedral inside a
mountain in Snowdonia – also plays an insurance role: it has enough oomph to restart the national grid in the event
of a major failure. Dinorwig can switch on, from 0 to 1.3 GW power, in 12 seconds.
Dinorwig is the Queen of the four facilities. Let’s review her vital statistics. The total energy that can be stored in
Dinorwig is about 9 GWh. Its upper lake is about 500m above the lower, and the working volume of 7 millionm^3
flows at a maximum rate of 390m^3 /s, allowing power delivery at 1.7 GW for 5 hours. The efficiency of this storage
system is 75%.