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Renewable Energy

  • Renewable energy is useful energy collected from renewable resources, which are naturally replenished on a human timescale, including carbon-neutral sources like sunlight, wind, rain, tides, waves, and geothermal heat. The term often encompasses biomass as well, whose carbon neutral status is under debate.
  • They are a viable source of clean, limitless energy, cause less emission, and are available locally. The use of renewable energy greatly reduces all sort of pollutions vis-a-vis nonrenewable energy. Most of the renewable sources of energy are fairly non-polluting and considered clean. But biomass through a renewable source is a major contributor to indoor pollution.

➤ Renewable energy comprises of

  • Solar energy - energy generated from the sun 
  • Hydel energy - energy derived from water 
  • Biomass – energy from firewood, animal dung, biodegradable waste and crop residues, when it is burnt. 
  • Geothermal energy- energy from hot, dry rocks, magma, hot water springs, natural geysers, etc. 
  • Ocean thermal - energy from waves and also from tidal waves. 
  • Co-generation - producing two forms of energy from one fuel. 
  • Fuel cells are also being used as a cleaner energy source.
  • Electricity is the flow of energy or current and is one of the most widely used forms of energy.


  • Primary source - renewable energy like solar, wind, geothermal Secondary source - nonrenewable energy generated through the conversion of coal, oil, natural gas etc. The Government has up-scaled the target of renewable energy capacity to 175 GW by 2022, including 100 GW from solar, 60 GW from wind, 10 GW from biopower and 5 GW from small hydropower.

➤ Installed power generation capacity in India

  • The total installed capacity in India from renewable energy in April 2016 is 42,800 MW. Majority of the total capacity is developed by the State sector accounting for about 39 per cent (app.) followed by Private sector for about 31 per cent (app.), and Centre hold about 29 per cent (app.) each.

Solar Energy

India is one of the few countries naturally blessed with long days and plenty of sunshine. There are two ways we can produce electricity from the sunlight:

  • Photovoltaic Electricity – uses photovoltaic cells that absorb the direct sunlight to generate electricity. 
  • Solar-Thermal Electricity – uses a solar collector with a mirrored surface that reflects the sunlight onto a receiver that heats a liquid. This heated up liquid is used to make steam that produces electricity.

➤ Photovoltaic Electricity

  • Solar panels are attached to an aluminium mounting system. Photovoltaic (PV) cells are made up of at least 2 semiconductor layers - a positive charge, and a negative charge. As a PV cell is exposed to sunlight, photons are reflected, pass right through, or absorbed by the solar cell. When the photovoltaic cell's negative layer absorbs enough photons, electrons are freed from the negative semiconductor material.
  • These freed electrons migrate to the positive layer creating a voltage differential. When the two layers are connected to an external load, the electrons flow through the circuit, creating electricity. The power generated - Direct Current (DC) is converted to Alternate Current (AC) using inverters.

➤ Concentrated Solar Power (CSP) or solar thermal technology

  • It utilizes focused sunlight and converts it into high-temperature heat. That heat is then channelled through a conventional generator to produce electricity. Solar collectors capture and concentrate sunlight to heat a fluid which in turn generates electricity.
  • There are several variations in the shape of the collectors. The most commonly used are parabolic troughs. Parabolic trough power plants use a curved, mirrored trough that reflects the direct solar radiation onto a glass tube containing a fluid. The fluid gets heated due to the concentrated solar radiation, and the hot steam generated is used to rotate the turbine to generate electricity. Commonly used fluids are synthetic oil, molten salt and pressurized steam. The power generated - Direct Current (DC) is converted to Alternate Current (AC) using inverters.

➤ Potential of solar energy in India

  • India has the potential to generate 35 M W/km2 using solar photovoltaic and solar thermal energy. 
  • Solar energy of about 5,000 trillion kWh per year is incident over India's land area with most parts receiving 4-7 kWh per sq. m per day. Hence, both technology routes (solar thermal and solar photovoltaic) for converting solar radiation into heat and electricity can effectively be harnessed, providing huge scalability for India's solar power. 
  • The states with very high solar radiation are Rajasthan, northern Gujarat and parts of Ladakh region, Andhra Pradesh, Maharashtra and Madhya Pradesh.

➤ Installed capacity – India

  • The current installed capacity of solar in grid-connected power crossed 10,000 MW, as on 2017, as per MNRE estimates. A major initiative called 'The National Solar Mission' was formulated by the Government of India and its state governments.
  • One of the main features of the Mission is to make India a global leader in solar energy and the mission envisages an installed solar generation capacity of 100 GW (revised target) by 2022.

➤ International Solar Alliance

  • International Solar Alliance (ISA) is launched at the CoP21 Climate Conference in Paris on 30th November as a special platform for cooperation among 121 solar resource-rich countries lying fully or partially between Tropic of Cancer and Tropic of Capricorn. The alliance is dedicated to addressing the special energy needs of ISA member countries. International Agency for Solar Policy and Application (IASPA) will be the International Solar Alliance's formal name. The ISA Secretariat will be set up in National Institute of Solar Energy, Gurgaon.

➤ Objectives

  • to force down prices by driving demand;
  • to bring standardization in solar technologies
  • to foster research and development. 
  • Prime Minister coined the new term "Surya Putra" for all the nations that fall between Tropic of Cancer and Tropic of Capricorn, which has been invited to join the alliance. The other term used for these countries is "Sunshine Countries".
  • IESS 2047 stands for India Energy Security Scenarios 2047 calculator launched by India to explore the potential of future energy scenarios for India.

Luminescent Solar Concentrators

A luminescent solar concentrator (LSC) is a device that uses a thin sheet of material to trap solar radiation over a large area, before directing the energy (through luminescent emission) to cells mounted on the thin edges of the material layer. The thin sheet of material typically consists of a polymer (such as polymethylmethacrylate (PMMA)), doped with luminescent species such as organic dyes, quantum dots or rare earth complexes.

➤ What is the need for LSCs?

  • The main motivation for implementing LSCs is to replace a large area of expensive solar cells in a stand-ard flat-plate PV panel, with a cheaper alternative. Therefore, both the cost of the module (£/W) and the solar power produced (£/kWh) are reduced.
  • A key advantage of over typical concentrating systems is that LSCs can collect direct and diffuse solar radiation. Therefore tracking of the sun is not required. 
  • LSCs are excellent candidates for building-integrated photovoltaics (BIPV) and for the cloudier northern climates.

➤ Ideal LSC

  • A broad absorption range to utilize the solar spectrum efficiently. 
  • 100% emission of light from the absorbing luminescent species. 
  • A large shift between the absorption and emission spectra to reduce absorption losses. 
  • Long term stability.

➤ Challenges for LSC

  • The development of LSCs aims to create a working structure that performs close to the theoretical maximum efficiency.

International Renewable Energy Agency (IRENA)

IRENA has 150 member nations with Headquarters in Abu Dhabi. The International Renewable Energy Agency (IRENA) is an intergovernmental organization supporting countries in their transition to a sustainable energy future. It serves as the principal platform for international cooperation, a centre of excellence, and a repository of policy, technology, resource and financial knowledge on renewable energy. IRENA promotes the widespread adoption and sustainable use of all forms of renewable energy, including bioenergy, geothermal, hydropower, ocean, solar and wind energy to pursue sustainable development, energy access, energy security and low-carbon economic growth and prosperity.

Wind Energy

Wind energy is the kinetic energy associated with the movement of atmospheric air. Wind turbines transform the wind's energy into mechanical power, further converting to electric power to generate electricity. Five nations – Germany, USA, Denmark, Spain and India – account for 80% of the world's installed wind energy capacity.

Wind farm

A wind farm is a group of wind turbines in the same location used to produce electricity. A wind farm can be located onshore and offshore.

  • Onshore wind farms: operate on land, where the wind tends to be the strongest. Onshore wind farms' turbines are less expensive and easier to set up, maintain and operate than offshore turbines. 
  • Offshore wind farms: Construction of wind farms in large bodies of water to generate electricity. Offshore wind farms are more expensive than onshore wind farms of the same nominal power.

Working of wind turbines

Wind turbines convert the kinetic energy in the wind into mechanical energy. This mechanical power can be used for specific tasks (such as grinding grain or pumping water), or a generator can convert this mechanical power into electricity. Most turbines have three aerodynamically designed blades. The wind's energy turns two or three propeller-like blades around a rotor connected to the main shaft, which spins a generator to create electricity. Wind turbines are mounted on a tower to capture the most energy. They can take advantage of the faster and less turbulent wind at 100 feet (30 meters) or more above ground.

➤ Three main variables determine how much electricity a turbine can produce

  • Wind speed: stronger winds produce more energy. A wind turbine generates energy at a speed of 4-25 metres per second
  • Blade radius: the larger the radius of blades, the more the energy produced. Doubling the blade radius can result in four times more power.
  • Air density: Heavier air exerts more lift on a rotor. Air density is a function of altitude, temperature and pressure. High altitude locations have low air pressure and lighter air, so they are less productive turbine locations. The dense, heavy air near sea level drives rotors faster and thus relatively more effectively.

➤ Two types of wind turbines

  • Horizontal: axis design has two or three blades that spin upwind of the tower. A horizontal axis machine has its blades rotating on an axis parallel to the ground. 
  • Vertical: axis turbines has vertical blades that rotate in and out of the wind. The vertical axis turbine has its blades rotating on an axis perpendicular to the ground. This drag-type turbine turns relatively slowly but yields a high torque. It is useful for grinding grain, pumping water and many other tasks, but its slow rotational speeds are not optimal for generating electricity. Vertical-axis turbines do not take advantage of the higher wind speeds at higher elevations (100 feet and so) above the ground vis-a-vis horizontal axis turbines.

Potential of wind energy in India

The National Institute of Wind Energy (NIWE) has recently launched Wind Energy Resource Map of India at 100 meters above ground level (AGL) on online Geographic Information System platform. The wind energy potential in the country at 100 m AGL is over 302 GW. Gujarat has the maximum potential followed by Karnataka, Maharashtra, Andra Pradesh according to the resource map.

➤ Wind energy target

  • 60000 MW (60 GW) by 2022 
  • 200000 MW (200 GW) by 2022

➤ Capacity installed

  • Tamil Nadu – 7200 MW 
  • Maharastra – 4000 MW 
  • Karnataka – 2700 MW 
  • Rajasthan – 2700 MW

Andra Pradesh, Madhya Pradesh, Kerala are minor players with an installed capacity of less than 1000 MW

➤ National Offshore Wind Energy Policy, 2015

  • Under this policy, the Ministry of New & Renewable Energy (MNRE) has been authorized as the Nodal Ministry for the use of offshore areas within the Exclusive Economic Zone (EEZ) of the country and the National Institute of Wind Energy (NIWE) has been authorized as the Nodal Agency for development of offshore wind energy in the country and to carry out allocation of offshore wind energy blocks, coordination and allied functions with related ministries and agencies.
  • It would pave the way for offshore wind energy development including, setting up of offshore wind power projects and research and development activities, in waters, in or adjacent to the country, up to the seaward distance of 200 Nautical Miles (EEZ of the country) from the baseline.

The policy will provide a level playing field to all investors/ beneficiaries, domestic and international.

➤ National Wind Energy Mission (Proposed)

  • Initiated the process of establishing National Wind Energy Mission. The setting up of a Mission would help in
    (i) achieving the targets of 12th Plan and energy generation from renewable energy asset under NAPCC, and
    (ii) addressing the issues and challenges which the wind sector is faced with, such as precise resource assessment, effective grid integration, improvement in technology and manufacturing base, to maintain its comparative advantage in the wind sector.
The document Renewable Energy - (Part - 1) | Environment for UPSC CSE is a part of the UPSC Course Environment for UPSC CSE.
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FAQs on Renewable Energy - (Part - 1) - Environment for UPSC CSE

1. What is renewable energy?
Renewable energy refers to energy that is derived from natural sources that can replenish themselves over time. These sources include sunlight, wind, water, geothermal heat, and biomass. Unlike fossil fuels, which are finite and non-renewable, renewable energy sources are sustainable and do not produce harmful greenhouse gas emissions.
2. What are the benefits of using renewable energy?
Using renewable energy has several benefits. Firstly, it helps to reduce greenhouse gas emissions and combat climate change. Secondly, it is a clean source of energy, which means it does not produce harmful pollutants that can damage the environment and human health. Additionally, renewable energy can contribute to energy independence and security, as it reduces reliance on imported fossil fuels. It also stimulates economic growth by creating job opportunities in the renewable energy sector.
3. What are the different types of renewable energy sources?
There are several types of renewable energy sources. Solar energy harnesses the power of sunlight using photovoltaic cells or solar thermal collectors. Wind energy utilizes wind turbines to convert the kinetic energy of wind into electricity. Hydropower generates electricity by capturing the energy of flowing or falling water. Geothermal energy utilizes heat from the Earth's core to generate electricity or heat buildings. Biomass energy involves converting organic materials, such as agricultural waste or wood, into usable energy.
4. Are renewable energy sources cost-effective?
Renewable energy sources have become increasingly cost-effective over the years. While the initial installation costs may be higher compared to traditional fossil fuel-based energy systems, the operational and maintenance costs are generally lower. Moreover, technological advancements and economies of scale have led to significant reductions in the cost of renewable energy technologies. As a result, renewable energy is becoming more competitive with conventional energy sources and can provide long-term cost savings.
5. How can individuals contribute to the use of renewable energy?
There are several ways individuals can contribute to the use of renewable energy. Firstly, they can install solar panels on their rooftops to generate electricity from sunlight. Secondly, they can opt for green energy providers that supply electricity generated from renewable sources. Additionally, individuals can conserve energy by using energy-efficient appliances, practicing energy-saving habits, and reducing their overall energy consumption. By supporting policies and initiatives that promote renewable energy, individuals can also help create a more sustainable energy future.
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