The Sun has been worshiped as a life-giver to our planet since ancient times. The industrial ages gave us the understanding of sunlight as an energy source. India is endowed with vast solar energy potential. About 5,000 trillion kWh per year energy is incident over India’s land area with most parts receiving 4-7 kWh per sqm per day. Solar photovoltaic power can effectively be harnessed providing huge scalability in India. Solar also provides the ability to generate power on a distributed basis and enables rapid capacity addition with short lead times. Off-grid decentralized and low-temperature applications will be advantageous from a rural application perspective and meeting other energy needs for power, heating and cooling in both rural and urban areas. From an energy security perspective, solar is the most secure of all sources, since it is abundantly available. Theoretically, a small fraction of the total incident solar energy (if captured effectively) can meet the entire country’s power requirements.
There has been a visible impact of solar energy in the Indian energy scenario during the last few years. Solar energy based decentralized and distributed applications have benefited millions of people in Indian villages by meeting their cooking, lighting and other energy needs in an environment friendly manner. The social and economic benefits include reduction in drudgery among rural women and girls engaged in the collection of fuel wood from long distances and cooking in smoky kitchens, minimization of the risks of contracting lung and eye ailments, employment generation at village level, and ultimately, the improvement in the standard of living and creation of opportunity for economic activities at village level. Further, solar energy sector in India has emerged as a significant player in the grid connected power generation capacity over the years. It supports the government agenda of sustainable growth, while, emerging as an integral part of the solution to meet the nation’s energy needs and an essential player for energy security.
National Institute of Solar Energy (NISE) has assessed the country’s solar potential of about 748 GW assuming 3% of the waste land area to be covered by Solar PV modules. Solar energy has taken a central place in India’s National Action Plan on Climate Change with National Solar Mission (NSM) as one of the key Missions. NSM was launched on 11 th January, 2010. NSM is a major initiative of the Government of India with active participation from States to promote ecological sustainable growth while addressing India’s energy security challenges. It will also constitute a major contribution by India to the global effort to meet the challenges of climate change. The Mission’s objective is to establish India as a global leader in solar energy by creating the policy conditions for solar technology diffusion across the country as quickly as possible. This is line with India’s Nationally Determined Contributions (NDCs) target to achieve about 50 percent cumulative electric power installed capacity from non-fossil fuel-based energy resources and to reduce the emission intensity of its GDP by 45 percent from 2005 level by 2030.
In order to achieve the above target, Government of India have launched various schemes to encourage generation of solar power in the country like Solar Park Scheme, VGF Schemes, CPSU Scheme, Defence Scheme, Canal bank & Canal top Scheme, Bundling Scheme, Grid Connected Solar Rooftop Scheme etc.
In order to achieve the above target, the Government of India has taken several steps for the promotion of solar energy in the country. These include:
Now, India stands 5th in solar PV deployment across the globe at the end of 2022 (Ref. REN21’s Global Status Report 2023 & IRENA’s Renewable Capacity Statistics 2023). Solar power installed capacity has reached around 70.10 GW as on 30-06-2023.
Solar energy is the most abundant & cleanest energy resource on earth. The amount of solar energy that hits the earth’s surface in an hour is almost the same as the amount required by all human activities in a year. Solar energy can be used mainly in three ways one is direct conversion of sunlight into electricity through PV cells, the two others being concentrating solar power (CSP) and solar thermal collectors for heating and cooling (SHC). India is endowed with abundant solar energy, which is capable of producing 5,000 trillion kilowatts of clean energy. Country is blessed with around 300 sunny days in a year and solar insolation of 4-7kWh per Sq. m per day. If this energy is harnessed efficiently, it can easily reduce our energy deficit scenario and that to with no carbon emission. Many States in India have already recognized and identified solar energy potential and other are lined up to meet their growing energy needs with clean and everlasting solar energy. In near future Solar energy will have a huge role to play in meeting India’s energy demand.
b) SOLAR PV TECHNOLOGYSolar Photovoltaic (PV) cells convert solar light directly to electricity. Photovoltaic can literally be translated as light-electricity.; Crystalline Silicon Crystalline silicon (c-Si) is the oldest technology for solar PV modules. C-Si modules are subdivided in two main categories:
i) single crystalline (SC-Si) and
ii) multi-crystalline (mc-Si). Thin Film A thin film is a newer technology in comparison to the crystalline silicon.
They are subdivided into three main families:
i) amorphous (a-Si) and micro morph silicon (a-Si/µc-Si),
ii) Cadmium-Telluride (CdTe), and
iii) Copper-Indium-Diselenide (CIS) and Copper-Indium- Gallium-Diselenide (CIGS).Emerging technologies encompass advanced thin films and organic cells. The latter are about to enter the market via niche applications.
Concentrator technologies (CPV)
Concentrator technologies (CPV) use an optical concentrator system which focuses solar radiation onto a small high- efficiency cell. CPV technology is currently being tested in pilot applications. Novel PV concepts aim at achieving ultra-high efficiency solar cells via advanced materials and new conversion concepts and processes. They are currently the subject of basic research.
Solar energy is used as heat source for heating purposes for direct use and to generate steam for generating electricity through turbines. Different technologies for solar thermal power plants making use of concentrating solar energy systems are:
i) Parabolic troughs
Parabola has the property of focusing the incoming radiation as its focus. Working on this principle, linear concentrators of parabolic shape are coated with highly reflective material and can be turned in angular movements towards the sun position and concentrate the incoming solar radiation onto a long-line receiving absorber tube. A working fluid is used to transfer the absorbed solar energy, which is then piped to an exchanger or a conventional conversion system. Parabolic trough systems cannot make use of diffused radiation as they use only direct-beam sunlight and require tracking systems to keep them focused toward the sun and are best suited to areas with high direct solar radiation. Most systems are oriented either east-west or north-south with single-axis tracking during the day.
ii) Solar Tower (Central Receiving System)
Central receiver systems use heliostats to track the sun by double axes mechanisms following the azimuth and elevation angles with the purpose to reflect the sunlight from many heliostats oriented around a tower and concentrate it towards a central receiver situated atop the tower. This technology has the advantage of transferring solar energy very efficiently by optical means and of delivering highly concentrated sunlight to one central receiver unit, serving as energy input to the power conversion system. In spite of the elegant design concept and in spite of the future prospects of high concentration and high efficiencies, the central receiver technology require more development for further up scaling plant performance. Its main attraction consists in the prospect of high process temperatures generated by highly concentrated solar radiation to supply energy to the topping cycle of any power conversion system and to feed effective energy storage systems able to cover the demand of modern power conversion systems. Different receiver heat transfer media that have been successfully used are water/steam, liquid sodium, molten salt, ambient air, oil. Solar Tower plants have the good long-term perspective for high conversion efficiencies and for use of very efficient energy storage systems by utilization of high temperatures in order to enlarge the solar capacity or solar share.
iii) Linear Fresnel
The Linear Fresnel technology uses long, flat or slightly curved mirrors to focus sunlight onto a linear receiver located at a common focal point of the reflectors. The receiver runs parallel to and above the reflectors and collects the heat to boil water in the tubes, generating high-pressure steam to power the steam turbine (water/direct steam generation, no need for heat exchangers). The reflectors make use of the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length. This reduces the plant costs since sagged-glass parabolic reflectors are typically much more expensive. Since the optical efficiency as well as the working temperatures are considerably lower than with other CSP concepts, saturated steam conditions have to be considered for this technology. Development is now heading from demonstration plants to bigger, commercialized projects. The receiver is stationary and so fluid couplings are not required (as in troughs and dishes). The mirrors also do not need to support the receiver, so they are structurally simpler. When suitable aiming strategies are used (mirrors aimed at different receivers at different times of day), this can allow a denser packing of mirrors on available land area.
Floating solar photovoltaic (PV) installations open up new opportunities for scaling up solar generating capacity, especially in countries with high population density and competing uses for available land. They have certain advantages over land-based systems, including utilization of existing electricity transmission infrastructure at hydropower sites, close proximity to demand centers (in the case of water supply reservoirs), and improved energy yield thanks to the cooling effects of water and the decreased presence of dust. The exact magnitude of these performance advantages has yet to be confirmed by larger installations, across multiple geographies, and over time, but in many cases, they may outweigh any increase in capital cost.
The general layout of a floating PV system is similar to that of a land-based PV system, other than the fact that the PV arrays and often the inverters are mounted on a floating platform. The direct current (DC) electricity generated by PV modules is gathered by combiner boxes and converted to alternating current (AC) by inverters. For small-scale floating plants close to shore, it is possible to place the inverters on land- that is, just a short distance from the array. Otherwise, both central or string inverters on specially designed floats are typically used. The platform, together with its anchoring and mooring system, is an integral part of any floating PV installation.
The following fund and non-fund based schmes are available in Solar (Ground-Mounted, Rooftop Sectors) :
