The Ecology Book

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evenly spread around the globe.

Offshore wind is generally stronger

and more regular than onshore.

Floating turbines can generate

wind energy far offshore, unlike

seabed-anchored wind turbines,

which have to be sited in shallow

water close to the coastline.

Geothermal energy

The heat in Earth’s interior is

derived both from the original

formation of the planet and from

the radioactive decay of materials

within it. People have bathed in hot

pools, where geothermally heated

water reaches the surface, since

Paleolithic times. Ancient Romans

made use of it to heat their villas.

Today it is employed to generate

electricity in at least 27 different

countries, with the United States,

the Philippines, and Indonesia the

world’s leading producers.

Geothermal heat is also utilized

directly to heat homes and roads

in Iceland. Technology is now

being developed that will use

geothermal hot water to operate

desalination plants. The only

drawback of this renewable energy

source is that it is concentrated

near tectonic plate boundaries,

where Earth’s mantle heat rises

RENEWABLE ENERGY

China’s Three Gorges Dam, the

world’s largest hydroelectric dam, was

completed in 2012. Critics point to its

ecological impact on the Yangtze River’s

habitat and biodiversity, and the risk for

local people of flooding and landslides.

close to the surface. The potential

is much greater, but drilling for

deep resources is very expensive.

Water power

Since water is 800 times denser

than air, even a slow-moving flow

can yield considerable amounts of

energy if harnessed, for instance,

by dams or tidal barrages that drive

Natural rock fractures that bring

hot water to the surface from

deep underground have been

described as the “low-hanging

fruit” of geothermal energy

because they are easy to exploit.

However, they are rare in most

parts of the world. The vast

majority of geothermal energy

locked beneath Earth’s surface

is in dry, nonporous rock.

The enhanced geothermal

system (EGS), a similar process

to fracking for natural gas and

Hot-dry-rock energy oil, aims to overcome this

problem by fracturing rock

strata and injecting water into

it at a great depth. The water

is heated by contact with the

rock, then returns to the surface

through production wells.

Depending on the economic

limits of drill depth, the

technology might be feasible

across many parts of the world,

but there are risks. Like fracking,

EGS can cause small earth

tremors, so it should not be

conducted near populated areas

or power stations.

... the wind and the sun

and the earth itself provide

fuel that is free, in amounts

that are effectively limitless.

Al Gore

American environmentalist and

former US Vice President

US_300-305_Renewable_energy.indd 304 12/11/18 6:26 PM