Energy Resources and Renewable Energy

Topic: Introduction to Renewable and Non-Renewable Energy Sources

• Energy resources are the main sources of energy from which energy can be extracted and utilized for mankind.
• Energy is a key input in economic growth, and the growth of a nation largely depends on the availability of energy resources.
• Conventional energy resources (e.g., coal, wood, diesel, petrol, natural gas) are depleting and may last for only 5-6 decades.
• There is a need to find non-conventional energy sources (e.g., solar, wind, tidal, geothermal) to meet the major part of energy demand in the future.

Classification of Energy Resources

• Primary energy resources: resources available in nature in their raw form (e.g., fossil fuels, uranium, hydropower).
• Secondary energy resources: obtained from primary energy resources by processing (e.g., electricity, steam, hot water, petrol, diesel, LNG, CNG).

Conventional and Non-Conventional Energy Resources

• Conventional energy resources: energy resources that have been traditionally used for many years (e.g., fossil fuels).
• Non-conventional energy resources: alternate energy resources to conventional energy resources (e.g., solar, wind, tidal, geothermal).

Need for Renewable Energy

• Renewable energy sources (e.g., solar, wind, hydro, geothermal) produce minimal or no greenhouse gas emissions during operation, helping to mitigate climate change.
• Advantages of renewable energy sources:
  • Recur in nature and are inexhaustible.
  • No fuel cost, hence negligible running cost.
  • Low energy density, minimal pollution and ecological balance problems.
  • Can help save foreign exchange and generate local employment.
  • Flexible and modular technology, can be rapidly deployed.

Indian and Global Energy Resources

• The world's energy supply primarily comes from fossil fuels (87%).
• India's use of fossil fuels constitutes more than 90% of its total energy consumption.
• Importance of non-conventional energy resources:
  • Increasing demand for energy due to industrialization and population growth.
  • Conventional energy resources are depleting fast.
  • Conventional energy resources (fossil fuels) cause pollution, thereby degrading the environment.

Energy Policy in India

• Features of India's energy policy:
  • Accelerated exploitation of domestic conventional energy resources.
  • Intensification of exploration to achieve indigenous production of oils and gases.
  • Management of demand for oil and other forms of energy.
  • Energy conservation and management.
  • Optimum utilization of existing capacity in the country.
  • Development and exploitation of renewable sources of energy.

World Energy Status

• Conventional resources:
  • Fossil fuels (coal, oil, gas) are a major source of energy.
  • Hydro resources are renewable and non-polluting.
• Non-conventional sources:
  • Solar energy is a major source of power, with an estimated potential of 178 billion MW.
  • Wind energy is the most economical energy resource.
  • Biomass energy resources consist of wood, leaves, and forest industry waste.
  • Geothermal energy has a potential of about 7704 MW installed electrical power generating capacity.

Indian Energy Scenario

• India's energy scenario:
  • Enormous demand for electricity due to economic growth.
  • Government encouragement of New and Renewable Source of energy (NRSE) to meet growing demand.
  • Department of Non-Conventional Energy Sources (DNES) was set up to develop new non-conventional sources of energy.

Solar Radiation

• The sun is the largest member of our solar system.
• Solar energy is the radiated heat energy from the sun, providing energy needed to sustain life in our solar system.
• Irradiance: the rate at which radiant energy is incident on a unit surface area.
• Irradiation: the solar energy per unit surface area striking a body over a specified time.

Extra-terrestrial Radiation and Solar Constant

• Extra-terrestrial radiation: solar radiation incident on the outer atmosphere of the earth.
• Solar constant: defined as the energy received from the sun per unit time on a unit surface area perpendicular to the direction of propagation of solar radiation at the top of earth's atmosphere.

Terrestrial Radiation

• Terrestrial radiation: solar radiation that reaches earth's surface after passing through earth's atmosphere.
• Beam radiation: solar radiation along the line joining the receiving point and the sun.
• Diffuse radiation: solar radiation scattered by particles in earth's atmosphere.
• Total or global radiation: the sum of beam radiation and diffuse radiation.

Latitude and Longitude

• Latitude: the angle subtended by the radial line joining the place to the centre of the earth, with the projection of the line on the equatorial plane.
• Longitude: measures distance east or west of the prime meridian.

Basic Sun-Earth Angles

• Latitude: measures the angle subtended by the radial line joining the place to the centre of the earth, with the projection of the line on the equatorial plane.
• Longitude: measures the distance east or west of the prime meridian.### Solar Angles
• Declination Angle: the angle between the line joining the centers of the sun and the earth, and its projection on the equatorial plane, varying from +23.5° to -23.5°.
• Hour Angle: the angle through which the earth must be rotated to bring the meridian of the plane directly under the sun, equal to 150° per hour.
• Incident Angle: the angle between the beam of rays and the normal to the plane.
• Tilt Angle: the angle made by the plane surface with the horizontal.
• Zenith Angle: the angle between the sun's ray and the normal to the horizontal plane.
• Solar Azimuth Angle: the angle between the projection of the sun's ray to the point on the horizontal plane and the line due south passing through that point.
• Angle of Incidence: the angle formed between the direction of the sun ray and the line normal to the surface.
• Surface Azimuth Angle: the angle in the horizontal plane between the line due south and the horizontal projection of the normal to the inclined plane surface.

Local Apparent Time (LAT)

• LAT is the time used for determining the hour angle, depending on the longitude of the place.
• LAT can be calculated from standard time by applying two corrections:
  • Correction due to the difference between the longitude at the location and the longitude of the place whose standard time is used.
  • Time correction due to small fluctuations in the earth's orbit and rate of rotation.

Measurements of Solar Radiation Data

• Solar radiation consists of two components: direct solar energy and diffuse solar energy.
• Direct solar energy: energy reaching the earth's surface with the sun's beam, having high heat content and causing sunburn.
• Diffuse solar energy: energy formed due to atmosphere attenuation, scattering, and beam redirection, propagating uniformly in all directions.

Measuring Solar Radiation Data

• Global radiation: measured using a pyranometer.
• Diffuse radiation: measured using a pyranometer with a shading ring to stop direct beam radiation.
• Beam radiation: measured using a pyrheliometer.
• Sunshine hours: measured using a sunshine recorder.

Pyranometer

• A radiation energy measuring device designed to measure global or total radiation on a horizontal plane.
• Can be used to measure radiation on an inclined plane.
• Consists of a thermopile with a hot junction, a blackened circular surface exposed to radiation, and a cold junction shaded to prevent radiation.
• Has a voltage output of approximately 9 µV/(W/m²) recorded on a chart paper.

Pyrheliometer

• An instrument to measure beam radiation.
• Has a narrow long tube (collimator tube) to collect beam radiation from the sun at normal incidence.
• Has a tracker to keep the collimator tube continuously facing the sun rays.
• Three types of pyrheliometers are used: Angstrom compensation pyrheliometer, Abbot silver disc pyrheliometer, and Eppley pyrheliometer.

Sunshine Recorder

• An instrument used to measure the duration of bright sunshine hours in a day.
• Consists of a glass sphere mounted on its axis parallel to the axis of the earth, and a recording paper card.
• The card has a special coated paper that burns a spot wherever sun's rays fall on it.
• The length of the trace formed by the burn spots on the card paper is the measure of the duration of sunshine hours in a day.