Renewable Sources

ENERGY RESOURCES:

         Energy sources can be classified into two types. They are renewable and non-renewable sources of energy.

Non renewable:

        Non renewable resources, such as fossil fuels and nuclear material, are removed from the earth and can be depleted. These resources have been the most used type of energy in the modern era.

i) Coal:

      Coal is a non renewable fossil fuel produced worldwide. It is formed when millions of years of pressure and heat turn the remains of prehistoric forests and swamps into coal. Coal is taken out of the earth either by deep mining(tunnelling underground) or strip mining(digging out layers of earth). It exists in different grades or qualities.

      Coal is used predominantly to produce electricity and to provide fuel for industries that require large amounts of heat. Production of steel, cement and paper all related on this industry. Coal traditionally has been used for heating many homes and businesses.

ii) Nuclear energy:

     Energy generated in a nuclear power plant is created when an atom of uranium is spilt and causes a chain reaction producing heat. This heat converts water to steam, which turns a turbine generating electricity. The water driving the turbine is cycled within an enclosed circuit, preventing any exhaust contaminated with radiation from escaping the system. The power of one uranium pellet in a reaction creates the same amount of energy as burning 150 barrels of oil.

iii) Bio energy:

      Bio energy is derived from biomass. Biomass is organic material which regenerated over time, such as wood, municipal waste, and alcohol fuels derived from agricultural crops. Energy is released by either direct burning or by creating a liquid-based fuel for transportation, such as ethanol and biodiesel. Uses for these fuels include generating electricity, fuelling transportation needs, and heating homes

Renewable:

     Renewable resources, such as wind, water, solar, and geothermal, come from sources that regenerate as fast as they are consumed and are continuously available. Some, such as biofuel produced from food crops and other plants, are replenished every growing season. In the early part of the twenty-first century, renewable sources have become more popular as non-renewable sources have begun to be depleted

Tidal energy:

    Tidal energy is produced through the use of tidal energy generators. These large under water turbines are placed in areas with high tidal movements, and are designed to capture the kinetic motion of the ebbing and surging of ocean tides in order to produce electricity. The tidal power has a great potential for the future power and electricity generation because of the massive size of the oceans

Hydro Power:

     Hydro power is energy created from moving water. Dammed water passes through a turbine that rotates a generator to create electrical power. This form of energy is relatively inexpensive and has various ranges of environmental impact depending on the facility size. Hydro power has supplied 28 million homes in the U.S with electricity, equalling 500 million barrels of oil.

Solar energy:

      The light and heat energy which is obtained from the sun is called solar energy. The sun radiates energy uniformly in all directions in the form of electromagnetic waves. It provides the energy needed to sustain life in our solar system. It is clean, inexhaustible, abundantly and universally available source of energy. The main drawback of solar energy is that not constant it varies consistently. The output of the sun is 2.8*10 ^23 kw/year. The energy reaching the earth is 1.5*10^18 kwh/year.

  

 The radiation from the sun when enters into the atmosphere it splits into the following categories:

a) Beam radiation:

    Radiation received from the sun to the earth without changing direction is called Beam radiation.

 b) Diffusion radiation:

   Radiation received from the sun, after being subjected to scattering in the atmosphere is called Diffusion radiation.

c) Global radiation:

   Sum of the beam radiation and diffusion radiation is called Global radiation

Measurement of solar Radiation:

Solar radiation data are measured mainly by the following instruments:

i) Pyranometer:

      A pyranometer is designed to measure global radiation, usually on a horizontal surface, but can also be used on an inclined surface. When shaded from beam radiation by using a shaded ring, a pyranometer measure diffuse radiation.

ii) Pyrheliometer:

      An instrument that measures beam radiation by using a long narrow tube to collect only beam radiation from the sun at normal incidence

iii) Sunshine Recorder:

      It measures the Sun shine hours in a day.

Solar energy can be utilized directly in two ways:

i) By collecting the radiant heat and using it in a thermal system or

ii) By collecting and converting it directly to electrical energy using a photovoltaic system

Wind energy:

     Wind energy is form of solar energy. Wind energy is the kinetic energy associated with the movement of large mass of air. These motions result from uneven heating of the atmosphere by the sun, creating temperature, density and pressure differences. It is estimated that 1 percent of all solar radiation falling on the face of the earth is converted into the kinetic energy of the atmosphere, 30 percent of which occurs in the lowest 1000m of elevation. It is thus an indirect form of solar energy. It is clean, cheap, and eco-friendly renewable source.

     Wind energy is harnessed as mechanical with the help of wind turbine. The mechanical energy thus obtained can either be used as such to operate farm appliances, and water pumping or converted to electric power and used locally or fed to a grid. A generator coupled to a wind turbine is known as the aero-generator. Very slow winds are useless, having no possibility of power generation. On the other hand, very strong stormy winds cannot be utilized due to the safety of the turbine. Moderate to high speed winds, typically from 5m/s to about 25m/s are considered favourable for most wind turbines