5.3 World hydro output
Looking at Figure 4, which shows the changing world annual hydro output between 1900 and 2009, you can see that in 1900 world annual output had reached an estimated 3.7 TWh from an installed capacity of about 1.3 GW. However, despite two world wars and the depression of the 1930s, world capacity then rose very rapidly. As the upward curve shows, output was increasing at an annual rate of nearly 10% per year throughout the first half of the twentieth century, leading to an output in 1950 that was nearly a hundred times that of 1900.
A fairly constant year-on-year increase of 50 TWh in annual output throughout the second half of the century was maintained, but in 2001 output fell by about 5% for the first time, despite a further rise in installed capacity. The drop was attributed mainly to exceptionally dry conditions in the Americas, the source of about a third of world output. The next year, 2002, was mixed.
The years from 2003 to 2008 were strikingly different again, with world output increasing by a total of 600 TWh over the five-year period. Assuming that the average capacity factor remained at about 43%, this implies an increase of about 30 GW in hydro capacity. This period saw growing contributions from the world’s two largest hydro plants, Three Gorges in China and Itaipú in Brazil.
But what about hydro on a small scale? We’ll move onto that subject next.