Alternative Energy Sources
Beginner's Guide to Environmentally-Friendly Renewable Energy
Simple definitions of the main sources of renewable energy including solar heat, the difference between fossil fuel and biomass; and a description of tidal power.
Solar Power
- Solar Panels for Hot Water : Solar panels are usually flat plates which are highly sensitive to the energy of the sun’s rays, absorbing this solar heat through a transparent cover. The energy is then collected through a transfer system which is used to heat water. The hot water is stored in a cylinder for use at any time.
- A more complex design is the evacuated tube system. With this system a row of glass tubes each contain absorber plates. The heat is collected and used to heat water in the same way.
Both systems are usually fitted to a southeast or southwest facing roof.
- Photovoltaic Cells : A Photovoltaic (pv) cell comprises semi-conducting material which, when exposed to daylight creates electrical charges. Groups of pv cells are joined together in modules so that sufficient output can be created. This is conducted away as direct current (DC) and can be used to run washing machines, fridges, computers and other electrical equipment. The solar energy generated through the photovoltaic process is clean, quiet and looks after itself.
Ground Source Heat Pumps
Pipes containing water and antifreeze are laid beneath the ground. The fluid moves through the pipes and absorbs heat from the earth. (The earth absorbs the heat of the sun and maintains an average temperature of around 12 degrees C.)
A heat pump moves the heat into a distribution system which then can be used by radiators or under floor heating. It can also be used to heat water. Ground source heat pump systems have been in use since the 1980s in Sweden, Germany and North America.
What is Biomass?
Fossil fuels are not renewable resources but currently are the most economically available source of power and include coal, oil and gas. They are derived from biological material that absorbed carbon dioxide from the atmosphere millions of years ago. To utilise their stored energy, fossil fuels are burned, releasing harmful substances. Mainly sulphur, nitrogen, and carbon, these combine with water vapour in the air to form compounds that create acid rain. The carbon dioxide that is released is considered a major influence in climate change.
A cleaner alternative to fossil fuels, is biomass, which takes carbon out of the atmosphere while it is growing, and returns it as it is burned. Examples include forestry wood, energy crops, and residues from agricultural harvesting. In domestic use, wood pellets are a compact form of biomass fuel used for heating. The pellets are carbon-neutral which means lower emissions than other heating fuels such as oil.
Tidal Power
Tidal power can generate hydroelectricity by damming the rising tide at the entrance to a river mouth or bay. When there is sufficient volume of water the dam opens and the water flows into a reservoir. This action turns the turbines and creates electricity. Water can be contained in the reservoir when the dam is closed. With the ebbing tide the reservoir water level is higher than the sea, and by opening the dam the water once again turns the turbines.
Wind Power
Wind turbines usually have 3 blades facing the wind which forces them to rotate. This movement turns a shaft inside the turbine which is connected to a generator, and produces the electricity.
Reference: A Solar World (David Elliot Green Books 2003)
