Geoscience Reference
In-Depth Information
Renewable energy from the environment
APPLICATIONS
Energy is vital to sustain civilization. Energy in some form is required whether it is in the home, at work or getting
from one place to another using transport rather than on foot. Demand for energy is still increasing, with coal, oil
and gas being the main sources, contributing about 90 per cent of the global total primary energy supply (2002).
Such sources are classed as non-renewable, as on the human time scale they are not replaced.
As indicated in this chapter Earth receives energy from the sun. We also have flows of energy as wind in the
atmosphere, water flowing downhill on the lithosphere and tides in the oceans. Attempts have been made to extract
energy from these sources. Whilst being technically possible, their use is not always cost-effective and subsidies
have been required to sustain them.
The most widespread method of energy production from renewable resources is hydropower. In its earliest days
the power was usually generated by flowing water causing a wheel to turn but the amounts of energy produced
were small. More effectively, energy can be extracted where water is at different levels, as in a dam, or between
high-level lakes and a lower-level river. Often this is linked with pumped storage where water is used to generate
electricity during high peak demand and is then pumped back to the higher level at times of lower demand, using
energy generated by fossil fuel systems where it is more difficult to stop and start generation.
Much energy is received from the sun. It has been estimated that, on a global scale, ten weeks of solar energy are
equivalent to all the fossil fuel reserves on Earth. However, it is effective only during daylight hours and cloud can
reduce the quantities considerably. In sunny climates, energy from the sun can be converted into heat by a solar
Wind is also a potential source of energy, often in areas where solar energy potential is less. It has been used from
historical times when windmills ground corn or pumped water, but now large-scale wind 'farms' have appeared to
utilize the energy from moving air. They are most effective where winds are steady and of moderate strength. In
Britain they are usually sited on high ground to take advantage of the higher wind speeds there, but in the North Sea
offshore towers have been built for electricity generation. Shortage of land sites and the significantly higher and
steadier speeds over the sea are reasons for this movement. At present most power generation by wind is in the
United States (mainly California), Germany, Denmark and India. The use of wind power does have some environmental
problems as well as visual impact but in the right areas there is the potential to increase energy generation by this
method.
and lakes, and from the soil involves the conversion of
thermal or radiant energy to kinetic and potential energy
as the water is again raised from its original position and
carried to higher levels in the atmosphere.
Landscape transfers
Many of these transfers influence landscape processes, for
the movement of water through the landscape is one of
the main ways Earth's surface is altered and moulded.
The potential energy possessed, for example, by boulders
on a slope is a product of the erosion of the valley by the
water and ice. Potential energy is also derived from earth
movements, for mountain building lifts the rock to leave
it higher than the surrounding Earth surface. Since these
mountain-building processes are powered by heat energy
within Earth, they represent the transformation of heat
Photo: Peter Smithson
