Renewable Energy is an energy source that can be defined as having a source which is able to reproduce itself and is therefore infinite. The main sources of renewable energy are the sun, the wind, water and the earth itself.

SOLAR ENERGY
Solar power is energy from the sun; more specifically solar power refers to technologies that convert sunlight into electricity or mechanical power.
Solar energy generates electricity without producing any emissions of greenhouse gases and its operation is silent. New applications of solar panels can also look aesthetically pleasing, keeping the environmental impact of this technology low. Photovoltaic equipment has no moving parts and as a result requires minimal maintenance.

PhotoVoltaic Panels

	A Solar Panel converts Photons to Electrons
	Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon (Si), which is currently the most commonly used. When light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely, thus creating electricity.
	A Solar Cell will absorb about 15 percent of the sunlight's energy.
	Energy loss occurs for a number of reasons: one is due to the material, other reasons are due to construction e.g. normally there is a conductive grid over the Silicon which blocks out some of the light.
	A typical Solar Panel consists of a sandwich of Glass, Semiconductor, metal grid glued together with adhesive and various protective coatings.

	Monocrystalline cells (obtained from monocrystalline silicon ingots)
	Polycrystalline cells (obtained from the casting of silicon blocks)
	Amorphous cells (obtained by cathodic deposition of silicon atoms onto glass or other appropriate supports)

WIND ENERGY
Wind is also renewable and infinite in its availability and is another important resource in the renewable energy arena.

Wind turbines generally have 3 blades and they rotate at 10-30 revolutions per minute. The blades face into the wind, the wind forces them to go round, which then spins a shaft inside the turbine, which is connected to a generator which produces the electricity.

Wind power enables electricity to be produced in an environmentally friendly way since the turbines don't produce chemical or radioactive emissions.

The ground on which the turbines are positioned can still be used for agricultural purposes.

GEOTHERMAL ENERGY
Geothermal simply means 'Earth's heat'. The centre of the Earth is extremely hot, current estimates are 5,500C at the core just over six and a half thousand kilometres below the crust meaning that even the upper 3 metres of the earth's surface stay at a nearly constant 10-16C throughout the year.

Additionally heat is collected on the surface of the earth through radiation from the heat of the sun.

The main application of geothermal energy in residential and commercial buildings is through the use of Geothermal Heat Pumps. This system comprises of a piping system which are located in the ground to collect the heat and then transfer to the home or business using the Geothermal Heat pump which is located inside the building. Through compression, heat pumps can ‘pump up’ heat at low temperature and release it at a higher temperature so that it may be used again.

HYDRO ENERGY
We have been using water as an energy source for generations with mills and machinery for being prime examples. More recently hydro electric plants have been built which use a reservoir and a dam to store a mass of water which is then released and passes through turbines at great speed to product electricity. This is a clean and pollution free way to generate electricity however there aren’t many sites left that haven’t been explored for this usage so other forms of hydro electricity are being developed including tidal and wave power.