Significant increase in green energy generation, solar in particular, is observed in recent times. Though this energy transition is extremely important from the environmental prospects, some challenges were encountered while increasing the renewable penetration in the modern grid. This article not only discusses the recent trends of India’s energy transition, but also the constraints of renewable energy sources are discussed to draw the conclusion.
During the last couple of decades, there is a considerable rise in the installation of renewable energy sources throughout the globe. According to the International Renewable Energy Agency (IRENA), China is leading the race with the installed capacity of 695.831 GW in the year 2018. In contrast, the installed capacity of renewable energy sources in the USA is 244,740 MW. India is ranked fifth in the list with the installed capacity of 117.955 GW. The top 10 countries of highest renewable energy installation setup with their respective installed capacity in the year 2018 is given in Figure 1. The top five countries of renewable energy generation from different sources are given in Table 1. According to the data of IRENA, hydropower, wind, solar and bioenergy are the few energy sources, which are extremely important areas of renewable energy in India.
According to the ministry of power of GoI, the total installed capacity of energy sources is 3,68,690 MW as on 31/01/2020. The thermal units comprising coal, lignite, gas and diesel units are responsible for aggregating 62.8% of the total power installation. Nuclear power constitutes 1.9% of the total power installation. The remaining installed power sources of 1,31,720 MW is contributed by hydro and other renewable energy sources. The renewable energy sources contribute the maximum portion (more than 60%) of this green energy. While analysing the renewable energy generation over the last five years, the increase in the contribution of renewable energy can be clearly observed. The percentage of renewable energy generation was 16.02% during 2015-16, which gradually increased to 19.1% in 2018-19.
Renewable Penetration in the Indian Grid
According to the annual report of 2018-19 issued by GoI’s Ministry of New and Renewable Energy (MNRE), a capacity of 78.32 GW is already installed by March 2019, which constitutes 21.95% of total installed capacity. Though 63.4% of the installed capacity comprises thermal sources, several initiatives were taken by the government to reduce the percentage in the future. Several initiatives were also taken by the GoI to increase hydroelectric generation through small and micro generating units. According to the annual report of MNRE, over 1100 small hydropower projects of capacities more than 4.5 GW were set up in various parts of the country and 116 projects of about 650 MW are in various stages of implementation. Actions were also taken to extract the maximum benefits of solar radiance, biomass, and the available wind energy. During the period of 01/01/2018 and 31/03/2019, a total of 15.45 GW of renewable power has been added to the grid, distribution of which is given in Figure 2.
It is clear from the discussions so far that – more than 70% added power to the grid during January, 2018 and March, 2019 is based on solar energy. According to the study of National Institute of Solar Energy (NISE), the solar energy potential of India is 748.98 GWp, which is much more than the total installed capacity of the national grid, which is about 368 GW at the end of December, 2019. According to NISE, the list of states with highest estimated solar energy potentials is given in Table 2. The table also includes the list of states with highest solar energy installations till March, 2019. From the table, it is clear that there are some states like Jammu and Kashmir, which although have a high potential of solar power, only a small amount can be extracted so far (14.83 MW out of 111.05 GWp). Therefore, it is possible to increase solar generation in the future through several schemes like Viability Gap Funding (VGF) scheme under the second phase of Jawaharlal Nehru National Solar Mission (JNNSM), Atal Jyoti Yojna etc. Several initiatives were also taken by the GoI to increase the use of solar energy for agricultural purposes like running irrigation pumps by using PV systems.
Wind energy is an intermittent and site-specific source of energy and therefore proper assessment must be required for the selection of potential sites. Over 900 monitoring stations were installed throughout the country by National Institute of Wind Energy (NIWE) to issue wind potential maps at 50 m, 80 m and 100 m. The process of assessing wind potential at 120 m above ground level is under progress. The state wise distribution of wind power in India to achieve gross wind power potential of 302 GW (at 100 m) is given in Figure 3. From the analysis of wind potential map, it is clearly visible that only few regions in India have prominent wind energy throughout the year. Based on the survey of NIWE, different wind farms were installed in the appropriate places to feed the wind energy to the electrical grid. As on 31/03/2019 the installed capacity of grid-interactive wind power in India is 35.62 GW of which more than 50% farms were situated in Tamil Nadu, Gujarat and Maharashtra. The energy generated by wind (in MUs) over the last few years is given in Table 3, which clearly indicates that some attempts were made by the GoI to increase the generation of this renewable source as well.
In order to recover energy from biomass including bagasse, agricultural residues and wood, ‘Biomass Power and Bagasse Cogeneration Programme’ is promoted by MNRE. In India, the total estimated potential for biomass power is about 26 GW of which 18 GW from agricultural and agro-industrial residues and remaining from bagasse cogeneration in sugar mills. Till March 2019, more than 500 biomass power and cogeneration projects with aggregate capacity of 9.1 GW were installed in different states of India. Some of the states with high generation capacity from biogas or bagasse power plants and their installed capacity are given in Table 4.
Small Hydro Power (SHP) projects having capacity up to 25 MW do not suffer from the problems like rehabilitation and resettlement which is associated with large hydel projects. It not only meets the power requirements of remote and isolated areas without disturbing the ecological balance of the areas, but also provides employment of the local people. In India, the estimated potential of small / mini/ micro hydel projects in the country is 21.13 GW through 7133 sites located in different states. Till March 2019, 1115 small hydropower projects (set-up both in public and private sectors) aggregating 4593.155 MW have been set up in various parts of the country. Some of the states with leading potentials of installing SHPs and the installed capacity till 31/03/2019 is given in Table 5.
Apart from on-grid renewable energy sources, there are several off-grid renewable applications. A total of 1536 water pumping windmills were installed in different states, particularly in Gujarat, Rajasthan, Kerala, Tamil Nadu and Bihar. A total of 3349.60 kW aero-generator small wind and hybrid systems were installed across different states and no more projects are sanctioned under this head. Some small projects were also developed under Biogas Power (Off-grid) Generation and Thermal Application Programme (BPGTP). BPGTP promotes biogas generation for decentralized applications like decentralized power generation (3 kW to 250 kW) and thermal energy applications having biogas generation capacity between 30 to 2500 cubic meters per day. Biomass Gasifier Program (BGP) is also promoted by MNRE under which electricity is produced locally by using biomass resources such as small wood chips, rice husk, arhar stalks, cotton stalks and other agro-residues in
Although solar generation is the most popular source of renewable energy in India, there are some constraints that limit its use. Generally, solar generation requires a larger area to install a solar farm. Approximately, one square kilometer of land will be required to generate a few tens of MW only and therefore availability of land is a big challenge in India. Due to the socio-economic condition, in India PV system installation is not popular among general people. Although subsidy is given by GoI, installation of PV systems is more popular in government and private organisations and big residential (or commercial) buildings only. Storage of generated energy is also a big challenge due to the higher cost and shorter life span of the batteries. Though the operating cost of PV systems is zero, high installation cost will result in higher per unit solar energy cost. There are also some environmental issues related with solar cell manufacturing as hazardous material like cadmium is used along with some non-biodegradable materials. Therefore, management of solar cell wastes after its lifetime will be a great challenge in the upcoming future.
The primary limitation of wind extraction in India is the limited number of available sites for installing the wind farms. Higher initial cost of installation of a wind farm is also a challenge, and therefore making per unit cost of generated energy higher. Initially, generation of noise was a problem with wind turbines, but with considerable technical advances, this problem has been reduced considerably. But the aesthetic impact and effect on wildlife is still a challenge for any wind turbine. There is a cut-in and cut-off wind speed limits for any wind turbine, which limits the energy generation region of the turbine. Similar to hydro energy sources, these farms are also often located at remote places, and therefore require a suitable power transmission network to deliver the generated energy to the grid.
Methane emission is highly probable in energy associated with biomass, which is harmful for the ozone layer. Large volume of water is required for such energy sources and therefore is more suited for the places where abundant water is available. The low efficiency of such energy systems is also a matter of concern. Careful production of biomass is highly desirable as deforestation may occur to increase the energy output. Although SHPs do not result in extensive damage in the ecosystem, they suffer from some limitations. Careful study must be done to select the suitable site for their installation, which is often remotely located. This in turn requires a power transmission infrastructure, thereby increasing the capital cost. Besides that their generation is fluctuating in nature and may reduce considerably during summer months due to reduced water flow.
From the discussions above, it is clear that India has an enormous potential of renewables – and the entire load requirement of the country may be met by the proper utilization of these energy sources. Although solar energy sources are more popular in recent times, projects were also carried out by the GoI, in particular for increasing the electricity generation by using wind energy, small hydel and biomass. ‘Ladakh Renewable Energy Initiative’ is a project implemented by MNRE since June, 2010, which focuses on the reduction of the dependence on diesel and kerosene in the Ladakh region by meeting the power requirement through the locally available renewable sources. The analysis of renewable energy sources clearly indicates a considerable difference between the energy potential and installed capacity of different renewable energy sources. Therefore, there is a considerable scope in increasing the renewable energy generation that can increase the per capita energy consumption without injecting the greenhouse gases in the environment. Uncertainty in generation is the major drawback of any renewable source due to their inconsistent nature. With increased penetration of renewable energy in the modern grid, accurate load forecasting becomes extremely difficult. Storage devices may be useful to overcome these fluctuations of renewable energy output. But they are not only costly and bulky in nature, their lifetime is comparatively smaller. Several works were carried out throughout the globe for minimizing the size and cost of storage devices. Some renewable energy sources like solar energy require different power electronic components for grid integration. Therefore, harmonics may be injected in the grid that may create problems in the electrical devices e.g. motors, transformers, alternators etc., connected to the system.
Dr. Subhra Jyoti Sarkar
He is an Asst. Prof. (NPIU), Dept. of Electrical Engineering, Parala Maharaja Engineering College, Berhampur, Odisha, India.
He is a student in the Dept. of Electrical Engineering, Parala Maharaja Engineering College, Berhampur, Odisha, India.
Prof. Sarat Kumar Sahoo
He is a Professor and HOD, Dept. of Electrical Engineering, Parala Maharaja Engineering College, Berhampur, Odisha, India.