Renewable Energy

 

Sources of Energy

An energy sources are something that can produce energy, either energy that can be directly used or through the conversion process first.

Energy sources are divided into two groups:

• Renewable
• Non-Renewable

Renewable energy

Renewable energy sources are energy that comes from nature and sustainable (never runs out), and can be replenished on a human timescale. The major types of renewable energy sources are:

• Biomass (wood, biogas, ethanol, biodiesel, etc)
• Hydro power
• Geothermal energy
• Wind energy
• Solar energy

Nonrenewable energy

The sources of non-renewable energy are the opposite of renewable energy. Although both come from nature, non-renewable energy sources are not sustainable (one time can run out), and takes a very long time to millions of years for replenished. The four major non-renewable energy sources are:

• Coal
• Natural gas
• Nuclear (Uranium)
• Oil and petroleum products (gasoline and diesel fuel)

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Focus on Solar Energy

Solar energy is created from radiant light and heat of the Sun. This energy can be harnessed using a range of ever-evolving technologies. Photovoltaics (PV) and solar thermal collectors are two current technologies that effectively can convert solar energy that can be used directly.

Photovoltaic (PV)

This technology converts sunlight directly into electricity using photovoltaic cells.

Solar Thermal Collectors

As renewable energy technology, solar thermal collectors capture and retain heat from the sun and transfer this heat to a liquid. This converts sunlight into thermal energy (or heat), which in the past has been used mainly for space heating or to heat water. Currently solar thermal collector has been used for a wider range of applications.

Two important physical principles govern the technology of solar thermal collectors:

• Any hot object ultimately returns to thermal equilibrium with its environment, due to heat loss from the hot object. The processes that result in this heat loss are conduction, convection and radiation. The efficiency of a solar thermal collector is directly related to heat losses from the collector surface (efficiency being defined as the proportion of heat energy that can be retained for a predefined period of time). Within the context of a solar collector, convection and radiation are the most important sources of heat loss. Thermal insulation is used to slow down heat loss from a hot object to its environment.
• Heat is lost more rapidly if the temperature difference between a hot object and its environment is larger. Heat loss is predominantly governed by the thermal gradient between the temperature of the collector surface and the ambient temperature. Conduction, convection as well as radiation occur more rapidly over large thermal gradients.