RENEWABLE energy is a hot topic these days with bold targets set to boost the amount of electricity we generate from devices like wind turbines and biomass-fuelled heating and power-generation systems. The five renewable sources used most often are biomass, hydro-power, wind, solar and geothermal.
Biomass is organic material made from plants and animals. Biomass contains stored energy from the sun. Plants absorb the sun’s energy in a process called photosynthesis. The chemical energy in plants gets passed on to animals and people that eat them.
Biomass is a renewable energy source because we can always grow more trees and crops, and waste will always exist. Some examples of biomass fuels are wood, crops, manure and some forms of rubbish.
Of the renewable energy sources that generate electricity, hydropower is the most often used. As much electricity is generated this way around the world as nuclear power.
It is one of the oldest sources of energy and was used thousands of years ago to turn a paddle wheel for purposes such as grinding grain. The first industrial use of hydropower to generate electricity happened in the late-1800s.
Because the source of hydropower is water, hydroelectric power plants must be located on a water source. Therefore, it wasn’t until the technology to transmit electricity over long distances was developed that hydropower became widely used.
The word, geothermal, comes from the Greek words, geo (earth) and therme (heat). So geothermal energy is heat from within the Earth. We can use the steam and hot water produced inside the Earth to heat buildings or generate electricity. Geothermal energy is a renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the Earth.
People around the world use geothermal energy to heat their homes and to produce electricity by digging deep wells and pumping the heated underground water or steam to the surface. Or we can make use of the stable temperatures near the surface of the Earth to heat and cool buildings.
Since ancient times, people have harnessed the wind’s energy. More than 5,000 years ago, the ancient Egyptians used wind to sail ships on the Nile River. Later, people built windmills to grind wheat and other grains. The earliest known windmills were in Persia (Iran). These early windmills looked like large paddle wheels. Centuries later, the people of Holland improved the basic design of the windmill. They gave it propeller-type blades, still made with sails. Holland is famous for its windmills.
The oil shortages of the 1970s changed the energy picture for the world. It created an interest in alternative energy sources, paving the way for the re-entry of the windmill to generate electricity. In the early-1980s, wind energy really took off in Europe and California, partly because of government policies that encouraged renewable energy sources.
Support for wind development is now widespread, with Europe leading the way.
The sun has produced energy for billions of years. Solar energy is the sun’s rays (solar radiation) that reach the Earth.
Solar energy can be converted into other forms of energy, such as heat and electricity. In the 1830s, the British astronomer, John Herschel, used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun’s energy for lots of things.
Solar energy can be converted to electricity in two ways:
