From the website, “The International Hydropower
Association and the International Energy Agency estimate the world’s total
technical feasible hydro potential at 14 000 TWh/year [6.4 kWh/d per
person on the globe], of which about 8000 TWh/year [3.6 kWh/d per per-
] is currently considered economically feasible for development. Most
of the potential for development is in Africa, Asia and Latin America.”


There are several places in the world with tidal resources on the same
scale as the Severn estuary (figure 14.8). In Argentina there are two sites:
San Jos´e and Golfo Nuevo; Australia has the Walcott Inlet; the USA &
Canada share the Bay of Fundy; Canada has Cobequid; India has the Gulf
of Khambat; the USA has Turnagain Arm and Knik Arm; and Russia has

And then there is the world’s tidal whopper, a place called Penzhinsk
in Russia with a resource of 22 GW – ten times as big as the Severn!

Kowalik (2004) estimates that worldwide, 40–80 GW of tidal power
could be generated. Shared between 6 billion people, that comes to 0.16–
0.32 kWh/d per person


We can estimate the total extractable power from waves by multiplying the
length of exposed coastlines (roughly 300 000 km) by the typical power per
unit length of coastline (10 kW per metre): the raw power is thus about
3000 GW.

Assuming 10% of this raw power is intercepted by systems that are
50%-efficient at converting power to electricity, wave power could deliver
0.5 kWh/d per person.


According to D. H. Freeston of the Auckland Geothermal Institute, geo-
thermal power amounted on average to about 4 GW, worldwide, in 1995 –
which is 0.01 kWh/d per person.

If we assume that the MIT authors on p234 were right, and if we assume
that the whole world is like America, then geothermal power offers
8 kWh/d per person.

Solar for energy crops

People get all excited about energy crops like jatropha, which, it’s claimed,
wouldn’t need to compete with food for land, because it can be grown on
wastelands. People need to look at the numbers before they get excited.