be built) terminating above the sea, with the sea being used as the lower

Thinking further outside the box, one could imagine getting away from
lakes and reservoirs, putting half of the facility in an underground cham-
ber. A pumped-storage chamber one kilometre below London has been

By building more pumped storage systems, it looks as if we could in-
crease our maximum energy store from 30 GWh to 100 GWh or perhaps
400 GWh. Achieving the full 1200 GWh that we were hoping for looks
tough, however. Fortunately there is another solution.

Demand management using electric vehicles

To recap our requirements: we’d like to be able to store or do without
about 1200 GWh, which is 20 kWh per person; and to cope with swings
in supply of up to 33 GW – that’s 0.5 kW per person. These numbers are
delightfully similar in size to the energy and power requirements of electric
cars. The electric cars we saw in Chapter 20 had energy stores of between
9 kWh and 53 kWh. A national fleet of 30 million electric cars would store
an energy similar to 20 kWh per person! Typical battery chargers draw a
power of 2 or 3 kW. So simultaneously switching on 30 million battery
chargers would create a change in demand of about 60 GW! The average
power required to power all the nation’s transport, if it were all electric, is
roughly 40 or 50 GW. There’s therefore a close match between the adoption
of electric cars proposed in Chapter 20 and the creation of roughly 33 GW

Figure 26.10. Lochs in Scotland with potential for pumped storage.
Figure 26.11. Okinawa pumped-storage power plant, whose lower reservoir is the ocean. Energy stored: 0.2 GWh. Photo by courtesy of J-Power.