Sun is an abundant source of energy and it is inexhaustible.

• Solar energy supports all life on earth and is the basis for almost every form of energy we use. 
• The sun makes plants grow, which are burned as fuel or rot in swamps and are compressed underground for millions of years to become coal and oil.
• Heat from the sun causes temperature differences between areas, causing the wind to blow. 
• Water evaporates due to heat of the sun vapours are carried to high elevations, and when the water vapours condense it precipitate as rainfall.
• The water rushes down towards the sea through rivers, to turbines for generating electricity. However direct solar energy can be used as heat, light, and electricity through the use of solar cells. 
• Solar energy use can be classified as: 
  • Direct Solar Energy - Direct use of solar energy can be used by various devices through systems that may be 
    • Passive solar energy
      • Earliest uses of solar energy were passive in nature such as to evaporate sea water for producing salt and for drying food and clothes, which is still being used for these purposes.
      • The more recent passive uses of solar energy is for cooking, heating, cooling and for the day lighting of homes and buildings.
      • The effectiveness of passive solar energy depends on good building design; it requires no mechanical means.
    • Active use of solar energy
      • Active solar heating and cooling systems rely on solar collectors which are usually mounted on roofs. Such systems also require pumps and motors to move the fluids or blow air by fan in order to deliver the captured heat. The main application of these systems is to provide hot water, primarily for domestic use.
      • Active solar heating is extensively used in India, Japan, Israel, Australia and Southern United States having sunny climate.
    • Solar Cells or Photovoltaic Technology
      • Solar energy can be converted directly into electrical energy by photovoltaic (PV) cells commonly called solar cells. Photovoltaic cells are made of silicon and other materials. When sunlight strikes silicon atoms it causes electrons to eject.
      • A typical solar cell is a transparent wafer that contains a very thin semi conductor. Sunlight energizes and causes electrons in the semiconductor to flow, creating an electrical current.Solar cells can provide electricity to remote villages.
      • India is the world’s largest market for solar cells. 
  • Indirect Solar Energy - (a) Wind energy, (b) Tidal energy, (c) Hydroelectric energy (d) Biomass energy

Advantages of Solar Power 

• Solar energy is a clean and renewable energy source. 
• Once a solar panel is installed, solar energy can be produced free of charge.
• Solar energy will last forever whereas it is estimated that the world’s oil reserves will last for 30 to 40 years.
• Solar energy causes no pollution. 
• Solar cells make absolutely no noise at all. On the other hand, the giant machines utilized for pumping oil are extremely noisy and therefore very impractical. 
• Very little maintenance is needed to keep solar cells running. There are no moving parts in a solar cell which makes it impossible to really damage them. 
• In the long term, there can be a high return on investment due to the amount of free energy a solar panel can produce, it is estimated that the average household will see 50% of their energy coming in from solar panels.

Disadvantages of Solar Power

• Solar panels can be expensive to install resulting in a time-lag of many years for savings on energy bills to match initial investments. 
• Electricity generation depends entirely on a countries exposure to sunlight; this could be limited by a countries climate.
• Solar power stations do not match the power output of similar sized conventional power stations; they can also be very expensive to build. 
• Solar power is used to charge batteries so that solar powered devices can be used at night. The batteries can often be large and heavy, taking up space and needing to be replaced from time to time.

Major Ongoing Schemes

• Pradhan Mantri Kisan Urja Suraksha Evam Utthan Mahabhiyan (PM KUSUM)
  • PM-KUSUM scheme is one of the largest initiatives in the world to provide clean energy to more than 3.5 million farmers by solarising their agriculture pumps. 
  • PM-KUSUM scheme aims to install grid connected ground mounted solar power plants (up to 2 MW) aggregating to a total capacity of 10 GW under Component A; install 20 Lakh standalone solar pumps under Component B; and solarize 15 Lakh grid connected agricultural pumps under Component C. All components combined would support installation of additional solar capacity of 30.80 GW. 
• Roof Top Solar (RTS) Programme 
  • Rooftop Phase-I of this programme was launched on 30th December, 2015 in which incentives and subsidies were provided for residential, institutional and social sectors. For Government sector, achievement linked incentives were also provided.
  • Rooftop Phase-II was launched in February 2019 with a target of achieving cumulative capacity of 40,000 MW by the year 2022. Under rooftop solar scheme, Central Financial Assistance (CFA) of 40% for RTS systems up to 3 kW capacity and 20% for capacity beyond 3 kW and up to 10 kW is provided. For Group Housing Societies (GHS) and Residents Welfare Associations (RWA), CFA is limited to 20% for RTS plants for supply of power to common facilities. So far over 3.7 GW capacity of RTS capacity has been estimated to have been installed in the country and over 2.6 GW capacity is under installation in the residential segment.
• Solar Parks
  • The Ministry introduced the Solar Parks programme with the objective of facilitating solar project developers to set up projects in a plug-and-play model. The scheme for development of solar parks has a target capacity of 40 GW. All States and Union Territories are eligible for getting benefit under the scheme. Solar parks are being developed by agencies of Central/State Governments, Joint Ventures between agencies of Central and State Governments and also by private entrepreneurs.
• Green Energy Corridors
  • To facilitate evacuation of electricity from RE projects, Green Energy Corridor scheme was launched in 2015 for setting up of transmission and evacuation infrastructure. The Inter-State Transmission System (ISTS) component consisting of 3200 ckm transmission lines and 17,000 MVA substations has been completed in March 2020. 
  • The Intra-State Transmission System (InSTS) component has been sanctioned to eight RE rich states of Tamil Nadu, Rajasthan, Karnataka, Andhra Pradesh, Maharashtra, Gujarat, Himachal Pradesh and Madhya Pradesh for evacuation of over 20,000 MW of renewable power. The InSTS component is under implementation and is anticipated to be completed by year 2021. Out of the target of approx. 9700 ckm transmission lines and approx. 22,600 MVA capacity substations under the InSTS component, approx. 7362 ckm lines have been constructed and 9656 MVA substations have been charged.
• Greening of Islands
  • The Government intends to fully convert Andaman and Nicobar, Lakshadweep islands to Green Energy where energy needs will be met using RE sources. The Greening of Islands programme aims to deploy 52 MW of distributed grid-connected solar PV power projects by March 2021. The Ministry provides 40% capital subsidy for projects under the scheme. Projects of 20 MW SPV with 16 MW/8MWH BESS in Port Blair, South Andaman; and a project of 1.95 MW with 2.15 MWH BESS in 4 Islands of Lakshadweep, are e xpected to be commissioned by January 2022.

International Solar Alliance (ISA)

• It is a treaty based inter-governmental organization working to create a global market system to tap the benefits of solar power and promote clean energy applications. With 75 signatory countries in this global collective, the ISA creates a multi-stakeholder ecosystem where sovereign nations, multilateral organizations, industry, policymakers and innovators work in together to promote the common and shared goal of meeting energy demands of a secure & sustainable world. 
• The Paris Declaration that established the ISA states that the countries share the collective ambition to undertake innovative and concerted efforts to reduce the cost of finance and technology for deployment of solar generation assets.
• The ISA aims to pave the way for future solar generation, storage and technologies for Member countries’ needs by mobilising over USD 1000 billion by 2030. Achievement of ISA’s objectives will also strengthen the climate action in member countries, helping them fulfil the commitments expressed in their Nationally Determined Contributions (NDCs).
• Objective 
  • Parties hereby establish an International Solar Alliance (hereinafter referred to as the ISA), through which they will collectively address key common challenges to the scaling up of solar energy in line with their needs. 
• ISA’s vision to enable One World, One Sun, One Grid 
• The ISA plays a four-fold role in establishing a global solar market: it is an accelerator, an enabler, an incubator, and a facilitator