effect. Direct current (DC) is produced by the PV effect based on the principle of photoelectric effect [12].
Solar cells or PV cells convert sunlight into DC electricity. But a large amount of electricity cannot be produced by single PV cell. Therefore, several PV cells are electrically connected to form a PV module or solar panel. Solar panels range from several hundred watts up to a few kilowatts and are also available in different sizes. Solar panels or modules produce current which is directly dependent on the incident light. Since most of the applications require AC power, the solar power system consists of an inverter too [13].
2.6.2 Photovoltaic Solar Power System
There are different types of PV systems:
PV direct system: This is the simplest type of PV system. Because they do not use batteries and not tied up to the grid, they power the load only when the sun is shining.
Off-grid system: This is also called as stand-alone systems which is independent of the power grid. When the sun is not available, batteries are used to store energy.
Grid connected system: Here solar PV systems are tied with grids so that the excess required power can be accessed from the grid. They may or may not be backed up by batteries.
2.6.3 Concentrated Solar Power System
In this type of solar power system, sun rays are focused on a small area by using mirrors or lenses. Due to this, a large amount of heat is generated at the focused area. This generated heat is used to heat the working fluid which, in turn, drives the steam turbine. There are three main types of concentrated solar power systems, namely, parabolic trough, power tower, and dish sterling system.
Advantages
Solar power causes no pollution.
Renewable energy resource and can produce clean power throughout the year.
Return on investment unlike paying for utility bills.
In case of grid connected excess power can be sold back to power company.
Helps the economy by creating jobs for solar manufacturers and installers.
Less safety risks.
Disadvantages
Initial cost is high for installation and material.
Requires additional equipment like inverter to convert dc to ac.
Efficiency is generally low.
Cloudy days do not produce as much energy.
Size of the solar panels varies depending on the geographical locations for the same power generation.
Large battery bank is needed to store the power.
Government Initiatives: Since solar energy has started to light up the lives of millions of peoples. Government has taken various initiatives to enable an increase in solar power at a subsidized energy cost. There are some top government initiatives which is listed below:
Solar park scheme [13].
Viability Gap Funding scheme (VGF).
Government Yojana solar energy subsidy scheme.
Ujjwal Discom Assurance Yojna scheme (UDAY) [13].
Rooftop scheme.
Jawaharlal Nehru national solar mission.
2.6.4 Major Solar Parks in India
1 Kurnool Ultra Mega Solar Park: It covers a total area of 5,932.32 acres in the Gani and sakunala villages and utilizes 4 million solar panels with capacities of 315 and 320 Watts. This solar park is able to generate more than 8 million KWh of electricity, which is enough to meet the total demand in Kurnool district.
2 Kamuthi Solar Power Park: It is the world’s sixth largest solar park and covers a total area of 2,500 acres in Kamuthi, Ramanathapuram district. This solar park is able to generate 648 MW at a single point [14].
3 Gujarat Solar Park: It covers a total area of 5,384 acres in the Charanka village, Patan district and installed capacity is 274 MW. It has also capacity to generate 100 MW of wind power. So, this is the biggest solar-wind hybrid park in the world.
4 Pavagoda Solar Park: It covers a total area of 13,000 acres in Pavagada Taluk, Tumkur district and planned to have a capacity of 2,000 MW at the end of 2018 and will be the world’s biggest solar park.
5 Punjab Solar Park: It is located in Bhatinda village, Punjab and installed capacity is 5 MW. The new concept of solar plus organic farming was introduced in this park.
6 Ujjain Solar Park: It is located in Ujjain, Madhya Pradesh and can able to generate 75 MW of solar energy [14]. Panel cleaning is done through the rain water harvesting.
7 Uttarakhand Solar Park: It is located in Maheswari village, Haridwar district and can able to generate 5.5 MW.
8 Ananthapuram Ultra Mega Solar Park: It covers a total area of 7,924.7 acres in Nambula Pulakunta, Ananthapuram district and has a capacity to generate 750 MW.
2.7 Wind Energy
Mankind has always been fascinated by the power of wind. Wind energy is one of the most exploitable forms of energy. From time immemorial, wind power is used for mechanical applications such as water pumping and milling. Professor James Blyth was known to be the first person to successfully produce electricity from wind power in 1887. As of 2019, the total installed capacity of wind power has grown to 651 GW [15].
The kinetic energy in the wind is used to rotate the blades of the rotor which is then used to rotate electrical generators to produce electrical power. The power contained in the wind is proportional to the cube of wind velocity. Therefore, if the wind speed is reduced by 2 percent then there will be an 8% reduction in the power output of the windmill. The place with strong wind is ideal for wind power plants. Generally, the wind speeds increase in fraction as the height increases. Not all the power in the windmill can be converted in to electrical power. Wind turbines are usually place at height of 400 ft. Wind energy is a low quality energy. Theoretically, one extracts a maximum of 16/27th of the total power contained in the wind irrespective of type of wind turbine. This limit is called the Betz limit or Betz coefficient.
Individual wind turbines have an average rating of 3 MW. Many individual wind turbines are connected to form a wind farm. A farm may contain few wind turbines to a large number of wind turbines built over a vast area both onshore as well offshore. Gansu wind farm of china is the largest of its kind in the world. India with an installed capacity of 37.5 GW stands fifth in the world wind power and second in the Asian countries.
Muppandal wind farm spread over Kanyakumari district of Tamil Nadu is the second largest wind farm in the world with 3,000 wind turbines to generate nearly 1,500 MW of electrical power. Tamil Nadu is the leader in wind power installation in India with installed capacity of 7,633 MW which account for 29% of India’s total wind energy installations. Gujarat has the highest wind energy potential of 142.6 GW.
The Government of India is keen in enhancing the wind energy sector. National Institute of Wind Energy is established under the aegis of Ministry of New and Renewable Energy sources which carry out activities like wind energy resource, testing, and certification.
Like solar, wind is a highly intermittent source of energy. This poses challenges in grid operation. Mostly, wind energy sites are located far away from the load site which necessitated the establishment of a complex transmission network. The tall structure is visually blocking the aesthetic of the area. Noise pollution is also caused by its blades.
Adequate investment in