Other supply-side ways of coping with slew

Some of the renewables are turn-off-and-onable. If we had a lot of renew-
able power that was easily turn-off-and-onable, all the problems of this
chapter would go away. Countries like Norway and Sweden have large
and deep hydroelectric supplies which they can turn on and off. What
might the options be in Britain?

First, Britain could have lots of waste incinerators and biomass inciner-
ators – power stations playing the role that is today played by fossil power
stations. If these stations were designed to be turn-off-and-onable, there
would be cost implications, just as there are costs when we have extra fossil
power stations that are only working part-time: their generators would
sometimes be idle and sometimes work twice as hard; and most generators
aren’t as efficient if you keep turning them up and down, compared with
running them at a steady speed. OK, leaving cost to one side, the crucial
question is how big a turn-off-and-onable resource we might have. If all
municipal waste were incinerated, and an equal amount of agricultural
waste were incinerated, then the average power from these sources would
be about 3 GW. If we built capacity equal to twice this power, making
incinerators capable of delivering 6 GW, and thus planning to have them
operate only half the time, these would be able to deliver 6 GW throughout
periods of high demand, then zero in the wee hours. These power
stations could be designed to switch on or off within an hour, thus coping
with slew rates of 6 GW per hour – but only for a maximum slew range of
6 GW! That’s a helpful contribution, but not enough slew range in itself, if
we are to cope with the fluctuations of 33 GW of wind.

What about hydroelectricity? Britain’s hydroelectric stations have an
average load factor of 20% so they certainly have the potential to be turned
on and off. Furthermore, hydro has the wonderful feature that it can be
turned on and off very quickly. Glendoe, a new hydro station with a capacity
of 100 MW, will be able to switch from off to on in 30 seconds, for
example. That’s a slew rate of 12 GW per hour in just one power station!
So a sufficiently large fleet of hydro power stations should be able to cope
with the slew introduced by enormous wind farms. However, the capacity
of the British hydro fleet is not currently big enough to make much con-
tribution to our slew problem (assuming we want to cope with the rapid
loss of say 10 or 33 GW of wind power). The total capacity of traditional
hydroelectric stations in Britain is only about 1.5 GW.

So simply switching on and off other renewable power sources is not
going to work in Britain. We need other solutions.

Pumped storage

Pumped storage systems use cheap electricity to shove water from a downhill
lake to an uphill lake; then regenerate electricity when it’s valuable,