RENEWABLE ENERGIES

| Main | Photovoltaics | Hydrogen |

Renewable energies capture their energy from existing flows of energy, from on-going natural processes, such solar energy, wind energy, water power, biological processes and geothermal heat flows. Therefore, renewable energies are virtually inexhaustible by human activity.

Most renewable forms of energy, other than geothermal and tidal power, ultimately come from the sun. Some forms are stored solar energy such as rainfall and wind power which is considered short-term solar-energy storage, whereas the energy in biomass is accumulated over a period of months, as in straw, or through many years as in wood.

Of all renewable energy sources, Photovoltaics has the biggest growth potential, since the sunshine provides 10,000 times more energy than mankind uses.

Obviously the sun does not provide constant energy to any spot on the Earth. However, energy supply and demand often do not coincide. If they do, consumers can use the electric energy directly, if not, Solar cells are often used to power batteries ( indirect use ) or other applications would require a secondary energy source, to cope with outages. Some homeowners use a solar system which sells energy to the grid during the day, and draw energy from the grid at night; this is to everyone's advantage, since power demand for air conditioning is highest during the day. In this case, the grid is seen as a big storage.

When energy demands are low, additional energy is stored for the use at a later time or in another location. This is where Hydrogen comes into play as an energy storage and transport medium of the future.