The Ecology Book

303

reason why, unlike other forms

of renewable energy, they are not

classed as “alternative” sources.

Renewable, clean energy will

have huge long-term benefits for

populations and ecosystems. It

reduces pollution, mitigates against

global climate change, builds

sustainability, and increases the

energy security of countries. If it

can be provided cheaply enough,

it will also pull many people out

of poverty. In some 30 countries,

renewable energy now makes up

more than 20 percent of the supply.

Solar energy

The Sun’s power could supply the

world’s energy needs several times

over. The International Energy

Agency (IEA) believes that—in

the short term—it has the greatest

potential of all the renewables. Its

radiation can be converted directly

into electricity via photovoltaic cells

(as with solar panels on buildings)

or indirectly by using lenses or

mirrors to create heat, which can

be converted to electricity. This is

called concentrated solar power.

Solar panels on a roof can heat

domestic water. Sunlight can be

employed to desalinate water

through an evaporative process,

first adopted by 16th-century Arab

alchemists and used on an

industrial scale in Chile in the late

19th century. In the developing

world, solar disinfection is bringing

safe drinking water to more than

two million people; the process

involves using solar heat and ultra-

violet light to kill pathogens.

Wind power

For more than 2,000 years, people

have built windmills to pump water

and grind grain. Today, wind farms

onshore and offshore account for

around 9 percent of renewable

energy consumption. A wind

turbine’s huge blades turn around

a rotor attached to a main shaft,

which spins a generator to produce

electricity. Wind power is now the

leading area of energy growth in

Europe, the US, and Canada.

Almost 50 percent of Denmark’s

energy comes from the wind, and

in Ireland, Portugal, and Spain the

figure is 20 percent. Its global

potential is thought to be around

five times its present level.

It is only economic to build wind

farms where there is regular wind,

however, so the potential is not ❯❯

See also: Global warming 202–203 ■ Pollution 230–235 ■ Ozone depletion

260–261 ■ Depletion of natural resources 262–265 ■ Waste disposal 330–331

ENVIRONMENTALISM AND CONSERVATION

Artificial

photosynthesis

Since the early 1970s, scientists

have been working to develop

the technology to mimic the

process of photosynthesis and

create liquid fuels from carbon

dioxide, water, and sunlight.

All three are plentiful, so if the

process can be replicated it

could produce an endless,

relatively inexpensive supply

of clean fuel and electricity.

There are two crucial steps:

to develop catalysts that use

solar energy to split water into

oxygen and hydrogen, and

to create other catalysts that

convert hydrogen and carbon

dioxide into an energy-dense

fuel, such as liquid hydrogen,

ethanol, or methanol. Scientists

at Harvard University recently

used catalysts to split water

into oxygen and hydrogen,

then fed the hydrogen, plus

carbon dioxide, to bacteria.

The bioengineeered bacteria

converted the carbon dioxide

and hydrogen into liquid

fuels. The next challenge is

to transfer a successful lab

experiment into something

commercially viable.

This solar fuel generator mimics

the way plants turn sunlight and

carbon dioxide in the air into energy

and oxygen.

Solar energy is derived

from solar radiation.

Solar radiation can

be used to produce

energy on Earth.

The supply of this

energy will not stop

as long as the Sun exists.

Solar energy is

without limit.

US_300-305_Renewable_energy.indd 303 12/11/18 6:26 PM