Solar energy is produced in the form of light and heat from the Sun. It may be used to produce heat and electricity. The applications of solar energy may be classified as active, passive, or photovoltaic. Active solar energy applications are usually concerned with harvesting thermal energy through the use of solar collectors that employ mechanical components to collect and transport heat. Passive systems, typically associated with the built environment, collect and transport heat by non-mechanical means. Photovoltaics utilize solar energy to directly produce electricity (Hodge 2017).
Photovoltaic or Solar cell, is the most preferred technology for generating electricity using solar energy. The ‘photons’ from solar radiation are captured by photovoltaic cells, which dislodge electrons from a material inside the cell, thereby resulting in the flow of electrons producing an electric current. Semiconductor materials such as silicon act as the best substance for this conversion of photon energy to electric current (Maczulak 2010).
Classification of photovoltaic systems (Hodge 2017):
Stand-alone photovoltaic systems are not connected to the electric grid. These may be direct-coupled photovoltaic systems, or may be provided with battery storage to permit operations during night hours, or else they may be supported by a non-grid source of electricity such as generator driven by a prime mover (hybrid power system).
Grid-connected photovoltaic systems are integrated to the electric grid, thereby supplying electricity to the grid.
The solar energy potential is derived from the incident global horizontal irradiation (GHI), which determines the total solar energy including direct normal solar irradiation (DNI) as well as the diffused horizontal irradiation, incident at a given location during a year. Indian Space Research Organisation also provides estimate of GHI derived from the half-hourly observations at 8 km spatial resolution in optical and thermal infrared bands from the Indian geostationary satellites such as KALPANA-1 Very High Resolution Radiometer (VHRR). The data is available on VEDAS and MOSDAC web portals of ISRO. Solar Calculator on web and Android app can be used to assess solar energy potential at any site.
The total potential of solar power in India is estimated at 748,990 MW (MoSPI 2019). India has set an ambitious target of attaining 100 GW of installed capacity for harnessing solar energy (NITI Aayog 2015). The total installed capacity of grid-connected solar power in India has increased from 2.6 GW in March 2014 to 28.18 GW in March 2019 (MNRE, 2020). Illustration 1 shows the 2 GW Pavagadh Solar Park in Karnataka state.
Illustration 1: 2 GW Pavagadh Solar Park, Karnatakah
Hodge, B. K. 2017, Alternative Energy Systems and Applications, Second Edition, John Wiley & Sons, Ltd., Hoboken, NJ, USA.
Maczulak, A. 2010, Renewable Energy, Sources and Methods. Facts On File, Inc. New York.
MNRE. 2020, Ministry of New and Renewable Energy (MNRE), Available: https://mnre.gov.in/solar/solar-ongrid/, Accessed: July 22, 2020.
MOSPI. 2019, Energy Statistics 2019. New Delhi: Ministry of Statistics and Programme Implementation (MOSPI).
NITI Aayog. 2015, Report of the Expert Group on 175 GW RE by 2022. New Delhi: NITI Aayog.