hat would harness wind energy from heated air in the Australian outback.
Catching some rays
Using solar power to
generate electricity has been considered since Victorian times and
clever building designs that use it to regulate temperature
have been around for millennia. Today solar power is used in several ways. In thermal solar power,
sunlight directly heats water in rooftop panels for household supplies, while
sunlight can also be converted to electricity
using photovoltaic cells,
which use semiconductors to turn photons into electricity.
Both types of power are
intermittent sources, as they can only work in good light. Photovoltaic cells have
been too expensive for widespread use, but are already popular for supplying
electricity to remote locations and filling gaps in
ramshackle electricity grids. Solar panels often power spacecraft too,
and solar cars and aeroplanes.
New cheaper versionsof
photovoltaic cells could mean more energy is generated from solar
than nuclear power by 2020.
In the future we may
generate solar power using flexible coverings that
"clothe" both buildings and people. There is even a
scheme for an orbiting solar power station.
Running on empty
When oil runs out what will
we fuel our cars with? This question, plus the fact the exhaust fumes are one
of the greatest contributors
to greenhouse gas emissions, means the race is on to find a
new solution to getting around.
Biofuels have been around since the internal
combustion engine. Ethanol is added to
petrol in the US, and millions of cars in Brazil are run on it
too. Vegetable oils are
already used in Europe to produce biodiesel. Soya oil could be used
for aviation too. Biofuels such as
fast-growing elephant grass or saplings could be used
to provide heat and electricity. Even sewage is being
considered as a biofuel.
Hydrogen fuel cells have enormous potential if
technical problems can be solved. Essentially a kind of battery that can be
continuously refilled, fuel cells chemically
react hydrogen with oxygen - producing just electricity and water.
This is a far more
efficient process than burning fuel, as much less energy is wasted as heat. See
how it works here. But it's not just
useful in cars: hydrogen could also be used in power stations and electronic and portable gadgets too.
Miniature fuel cells may one day oust batteries.
The problem is that catalysts and membranes have been expensive until recently.
Other problems include making tanks of pressurised flammable hydrogen safe
enough for cars and creating an entire fuelling station infrastructure.
Combining traditional engines with fuel cells
could be step in the right direction. A new $10 million prize has
been offered to help solve these problems.
Fuel cells can also use
natural gas, methanol or coal - but these
produce carbon dioxide. Hydrogen is not yet a completely clean either, as
electricity - currently derived from fossil fuels - is needed
to"crack" water to produce the hydrogen. Some cities, such as
Reykjavik, already use hydrogen to power buses. But
Iceland gets some electricity and over 80% of its heating and hot water
from geothermal energy sources, and can produce the hydrogen
emission-free. Other countries need to find ways to produce the hydrogen sustainably.
Some argue that the
"hydrogen economy" is a distraction from
meeting future energy needs and slowing climate change, and
that we need to focus on more immediate solutions.
Making social change might be
more difficult than solving technical problems.
Solutions that could be put
in place right now include filtering carbon
dioxide out of emissions and burying it in oil seams
or under the sea. The US
is among 6 nations that have turned their back on
the Kyoto protocol to curb climate change and are focusing instead on "clean energy" from
Increasing efficiency in energy production could also
yield massive savings, as it did during the oil crises of the 1970s. Methods
vary from reducing the friction
of trains to lowering speed limits
Producing combined heat and power
with small generators at home,
makes use of a lot of the energ