Wind turbines are getting bigger all the time. Do bigger wind turbines
change this chapter’s answer?

Chapter B explains. Bigger wind turbines deliver financial economies
of scale, but they don’t greatly increase the total power per unit land area,
because bigger windmills have to be spaced further apart. A wind farm
that’s twice as tall will deliver roughly 30% more power.

Wind power fluctuates all the time. Surely that makes wind less useful?

Maybe. We’ll come back to this issue in Chapter 26, where we’ll look
at wind’s intermittency and discuss several possible solutions to this problem,
including energy storage and demand management.

Notes and further reading

page no.

32Figure 4.1 and figure 4.6. Cambridge wind data are from the Digital Technology Group, Computer Laboratory, Cambridge
[vxhhj]. The weather station is on the roof of the Gates building, roughly 10 m high. Wind speeds at a height of
50 m are usually about 25% bigger. Cairngorm data (figure 4.2) are from Heriot–Watt University Physics Department

33The windmills required to provide the UK with 20 kWh/d per person are 50 times the entire wind power of Denmark.
Assuming a load factor of 33%, an average power of 20 kWh/d per person requires an installed capacity of 150 GW.
At the end of 2006, Denmark had an installed capacity of 3.1 GW; Germany had 20.6 GW. The world total was 74 GW
(wwindea.org). Incidentally, the load factor of the Danish wind fleet was 22% in 2006, and the average power it
delivered was 3 kWh/d per person.

Figure 4.6. Histogram of Cambridge average wind speed in metres per second: daily averages (left), and half-hourly averages (right).