Renewable Energy Definition

Renewable energy is a term used for forms of energy which are not exhausted by use over time. It means that the renewable resources can be regenerated or renewed naturally in a relatively short time scale. The forms of energy include chemical (energy of chemical reactions), electromagnetic (energy associated with electrical or magnetic forces), heat (kinetic energy of particles inside the bodies), light (radiant energy), mechanical potential energy (energy of gravitational field), mechanical kinetic energy (energy of moving mass) and nuclear (or mass) energy.

The sources of renewable energy can be derived from the sun’s energy (direct solar radiation, biomass, wind, hydropower), earth’s interior (geothermal) and tidal energy (wave, tidal, Oceanic Thermal energy Conversion). The availability of these sources would vary,  depending on their attractiveness to the end user.

Criteria for Energy Source to be Renewable Energy

The criteria for energy sources to be renewable energy include;

(i)                  To be replenished

(ii)                The rate of being used should not exceed the rate of renewable energy re-generated

(iii)               Unlimited supply of energy source

Solar energy is a result of radiation from the sun. The amount of solar radiation generated can be affected by climate and the cloud cover, latitude of the site and time.

Biomass resources suitable for energy production covers a wide range of materials, from firewood collected in farmlands, Solid Municipal Waste (SMW) and natural woods to agricultural and forestry crops grown. It is the energy derived from photosynthesis process and is essentially a chemical solar energy storage. During application of energy resulted from biomass, some energy can be escaped in any forms of energy especially radiation energy which can be used during photosynthesis process to create plant’s food.

Wind is caused by movement of air from high pressure (North/South poles) to low pressure areas (Equator). Due to the west east earth’s rotation caused wind to curve to the west toward equator creates – trade wind (0⁰- 30⁰ N or S of the equator) and polar easterlies wind types (60⁰-90⁰N or S from the equator) and also causes wind to blow away from equator to curve to the east - prevailing westerlies wind type (30⁰-60⁰ N or S from the equator). Also wind can be caused by unequal amounts of solar energy received at different latitudes.

Geothermal energy refers to heat stored beneath the surface of the earth. It originates from the

earth’s molten interior and the decay of radioactive materials. Waves store energy from the wind and can be caused by friction between wind and water surfaces such as in the ocean. Tides are caused by the gravitational attraction of the moon and the sun acting upon the oceans of the rotating earth, caused the surface of the oceans to be raised and lowered periodically which energy can be extracted. Ocean Thermal Energy Conversion (OTEC) is a means of converting into useful energy with only adequate temperature difference of 20⁰C between surface water of oceans in tropical and sub-tropical areas.

By definition, renewable energy should provide a continuous and unlimited supply of energy. However, technical difficulties, the intermittent nature of some of the renewable energy resources, as well as other constraints still pose limits to their wider deployment. For instance the non renewable energy (Fossil fuel) can be a renewable energy if the rate of fossil fuel to be re-generated in specified time is direct proportional to the rate of  extract and use it.