Technology Options for Renewable Energy
Both IEA forecast and WEC’s world energy scenarios of 2050 show that fossil fuels will still play a crucial role for both power generation and transport. Coal is going to play an important role in the long run especially for power generation in China and India...
- Ajit Kumar, Dr A.P. Dash
Modern energy services are crucial to human well-being and to a country’s economic development; and yet globally over 1.3 billion people are without access to electricity and 2.6 billion people are without clean cooking facilities. More than 95% of these people are either in sub-Saharan African or developing Asia and 84% are in rural areas. Commercial energy at affordable price with sustainable means is required to uplift this huge population.
The world is not on course for a sustainable energy future. World needs energy, both for power and non-power applications like building, industry and transport rely heavily on fossil fuels. CO2 emissions have increased by more than 20% over the last decade. Indeed, if the future is in line with present trends, CO2 emissions and oil demand will continue to grow rapidly over the next 25 years. This is after taking account of energy efficiency gains and technological progress that can be expected under existing policies. Extrapolating this beyond 2030 shows that these trends are likely to get worse. In the Baseline Scenario of IEA, CO2 emissions will be almost two and a half times the current level by 2050. Surging transport demand will continue to put pressure on oil supply. The carbon intensity of the world’s economy will increase due to greater reliance on coal for power generation – especially in rapidly developing countries like India and China with huge domestic coal reserves.
Both IEA forecast and the WEC’s World Energy Scenarios to 2050 show that, in 2050, fossil fuels will still play a crucial role for both power generation and transport. Coal is going to play an important role in the long run, especially for power generation in China and India, the two most rapidly growing demand centres up to 2050. Natural gas, especially from unconventional sources, will play an increasing role and gain more importance in the energy share. An example is the transport sector where heavy transport will depend on fossil fuels for decades to come. Oil will continue to remain dominant for transport, an increase in importance of unconventional sources – in particular oil sands, and oil shale – is expected. No renaissance of nuclear energy is anticipated in the next decade. In the Symphony scenario, the WEC anticipates a large increase of non-CO2 technologies globally, including hydro, other renewables such as solar PV and wind, nuclear and carbon capture and storage (CCS).
Classification of Present power generation options
Of the 1.4 billion people of the world who have no access to electricity in the world, India accounts for over 300 million. The IEA estimates India will add between 600 GW to 1,200 GW of additional new power generation capacity before 2050. As per WEC projections, primary energy supply needs to be increased four to five times and electricity generation supply by six to seven times up to 2030/31 (as compared to 2003/04). The technologies and fuel sources India adopts, as it adds this electricity generation capacity, may make significant impact to global resource usage and environmental issues.
As per many estimates, India is expected to become world’s largest economy by 2050 overcoming China and USA. It is anticipated that this will lead to widening gap between domestic energy resources and demand, especially for coal, oil and natural gas. This scenario requires that India shall harness and deploy renewable energy heavily.
India is one of the lowest GHG emitters in the world on a per capita basis. The country is vulnerable to climate change and has a strong interest in having a fair and equitable global agreement for minimising the risk of climate change. India has announced its intention to reduce the emissions intensity of its GDP by 20–25% over the 2005 levels by the year 2020.
India is entering an era of unprecedented change in the way we produce and use energy. The conventional thinking about how energy is extracted, converted, and consumed is being challenged by growing concerns about the environmental impacts of power generation on land, water, air quality, and climate. Although the long-term opportunity to reshape our energy infrastructure is promising, the current reality is that fossil energy remains the backbone of the Nation’s energy economy.
Currently, about eighty two percent of our electricity is generated by fossil‐fired plants (Thermal), comprising about seventy percent of our installed capacity (CEA report April to Dec 2014). These fossil fired power plants are responsible for almost all of the carbon emissions from the power sector. There is a growing concern to address ways to reduce emissions through a change in the fundamental energy supply structure. These concerns are driving the thrust for solar and other renewable power generating options.
In view of above GOI has set an ambitious target of adding 175GW of renewable power by 2022. Out of this target, it is proposed to add 100 GW through Solar ( utility scale, distributed, off-grid/ mini grid), 60 GW through Wind ( utility scale),5 GW through Small hydro and 10 GW through Bioenergy. Various technology options available for these sources have to be deployed to achieve this target.
Considering these targets, renewables will account for approx. 40 % of total installed capacity and 19 5 of total generation by 2022.
Various sources of renewable power are Hydro, Wind onshore and offshore, Solar PV, Solar CSP, Biomass and Geothermal which have been tapped commercially and are discussed below:
India is endowed with economically exploitable and viable hydro potential assessed to be about 84,000 MW at 60% load factor. In addition, 6740 MW in terms of installed capacity from Small, Mini, and Micro Hydel schemes have been assessed. Also, 56 sites for pumped storage schemes with an aggregate installed capacity of 94,000 MW have been identified. It is the most widely used form of renewable energy. India is blessed with immense amount of hydro-electric potential and ranks 5th in terms of exploitable hydro-potential on global scenario.
The present installed capacity as of 31 March 2015 is approximately 41267 MW which is 15.18% of total electricity generation in India. The public sector has a predominant share of about 97% in this sector.
Pumped storage plants are perfect peaking power solution for the load management in the electricity grid. Pumped storage schemes would be in high demand for meeting peak load demand and storing the surplus electricity as the share of renewable, which is of intermittent nature grows and India graduates from electricity deficit to electricity surplus. Pump storage stations also produce secondary /seasonal power at no additional cost when rivers are flooding with excess water. Other alternatives to store electricity such as batteries, compressed air storage systems, etc. are costlier than pump storage system. India has already established nearly 6800 MW pumped storage capacity which is part of its installed hydro power plants.
A schematic view of a hydro power plant
As per report circulated by MNRE, hydro project cost is of the order of Rs 10.5 crores and 9 crores per MW for small and large scale respectively and predicted cost for the year 2020 based on analysis of available data is Rs 13.5 crores and 11.3 crores per MW for large and small scale respectively.
Another cheap renewable source, wind energy has already been exploited to a great extent and may continue to find greater deployment at remaining potential onshore and offshore sites.
It is estimated that with the current level of technology, the ‘on-shore’ potential for utilization of wind energy for electricity generation is of the order of 65,000 MW. India also is blessed with 7517km of coastline and its territorial waters extend up to 12 nautical miles into the sea. A total of about 23444 MW of commercial projects have been established until March 31, 2015. The unexploited resource availability has the potential to sustain the growth of wind energy sector in India in the years to come. The potential is far from exhausted.
A noteworthy feature of the Indian program has been the interest among private investors/developers in setting up of commercial wind power projects. Several companies have established themselves in wind technology manufacturing. In the years ahead, the prospects of wind electricity generation are bright due to its maturity, cost competitiveness and policy enablers in India.
As of 31 March 2015 the installed capacity of wind power in India was 23,444 MW, mainly spread across Tamil Nadu (7,253 MW), Gujarat (3,093 MW), Maharashtra (2,976 MW), Karnataka (2,113 MW), Rajasthan (2,355 MW), Madhya Pradesh (386 MW), Andhra Pradesh (916 MW), Kerala (35.1 MW),etc. East and North east regions have no grid connected wind power plant as of March, 2015 end.
No offshore wind power farm utilizing traditional fixed-bottom wind turbine technologies in shallow sea areas or floating wind turbine technologies in deep sea areas is under implementation. However, India is looking at the potential of offshore wind power plants, with a 100 MW demonstration plant being planned off the coast of Gujarat (2014).
The capital cost for wind power ranges between 5.0 crores to 7.5 crores per MW, depending up on the type of turbine, technology, size and location.
With about 300 clear, sunny days in a year, India's theoretical solar power reception, on only its land area, is about 5,000 trillion kilowatt-hours (kWh) per year (or 5 EWh/yr) The daily average solar energy incident over India varies from 4 to 7 kWh/m2 with about 1,500–2,000 sunshine hours per year (depending upon location), which is far more than current total energy consumption. For example, assuming the efficiency of PV modules were as low as 15%, this would still be a thousand times greater than the domestic electricity demand projected for 2015.
Utility scale solar plants require huge land. Land is a scarce resource in India and per capita land availability is low. Dedication of land area for exclusive installation of solar arrays might have to compete with other necessities that require land. The amount of land required for utility-scale solar power plants — currently approximately 4-5 acre per MW — could pose a strain on India's available land resource.
The architecture more suitable for most of India would be a highly distributed set of individual rooftop power generation systems, all connected via a local grid. However, erecting such an infrastructure, which does not enjoy the economies of scale possible in mass, utility-scale, solar panel deployment, needs the market price of solar technology deployment to substantially decline, so that it attracts the individual and average family size household consumer. That might be possible in the future, because PV is projected to continue its current cost reductions for the next decade and be able to compete with fossil fuel. Right government policies such as differential tariff can also encourage roof top deployment. Government may provide subsidies for the production of PV panels and this can lead to more usage of solar power in India.
Operating silently and without any moving parts or environmental emissions, PV systems have developed from being niche market applications into a mature technology used for mainstream electricity generation. A roof-top system recoups the invested energy for its manufacturing and installation within 0.7 to 2 years and produces about 95 percent of net clean renewable energy over a 30-year service lifetime.
India is currently pursuing aggressive solar capacity addition program. Present solar capacity of 3743 MW is hardly 1.37% of total installed capacity as on 31 March 2015. Total renewable share is just about 13% of total generation. Intermittent nature of renewable generation is therefore not a big problem right now. However, the pace at which the solar generations is being added to the grid, we may reach the point very soon where the problems of huge intermittent renewable capacity will pose serious threat to stable grid operation and economical operation of conventional fossil fuel plants.
India is facing a perfect storm of factors that will drive solar photovoltaic (PV) adoption at a "furious pace over the next five years and beyond". The falling prices of PV panels, mostly from China but also from the U.S., has coincided with the growing cost of grid power in India. This coupled with Government support for 100 GW solar capacity by 2022 and ample solar resources have also helped to increase solar adoption.
Due to the exponential growth of solar photovoltaics, prices for PV systems have rapidly declined in recent years. However, they vary by market and the size of the system. Given the smaller system size, home installations are more costly than commercial or utility installations. However, by the end of 2014, residential rooftop PV system installed prices averaged $3.48 per watt, down from $3.83 per watt in the first three months of 2014, the sharpest absolute decline in recent times. Solar PV prices in India for roof top solar ranges from INR 30-60 per watt (approx. $ 0.5 to $1 per watt). Nowadays, solar PV modules account for less than half of the system's overall cost leaving the rest to the remaining BOS-components and to soft costs, which include customer acquisition, permitting, inspection and interconnection, installation labor and financing costs. The average cost of generation from grid connected solar plant is now in the range of Rs 5 to 5.50 per unit.
Concentrated Solar Power (CSP)
Concentrating solar plants (CSP) generate solar thermal electricity while producing no greenhouse gas emissions, so it could be a key technology for mitigating climate change. In addition, the flexibility of CSP plants enhances energy security. Unlike solar photovoltaic (PV) technologies, CSP plants use steam turbines, and thus can provide most needed ancillary services. Moreover, they can store thermal energy for later conversion to electricity. CSP plants can also be equipped with backup from fossil fuels delivering additional heat to the system. When combined with thermal storage capacity of several hours of full-capacity generation, CSP plants can continue to produce electricity even when clouds block the sun, or after sundown or in early morning when power demand steps up. Supplementing solar PV with storage technologies in an attempt to solve these challenges may disrupt the cost economics of solar PV in long run and the balance may shift towards CSP technology which is more suited to thermal storage and can provide cheaper alternative to Solar PV with storage.
Hybridization of solar thermal with conventional coal or gas based system is another alternative to reduce cost and to handle the problem of intermittency. NTPC has recently taken up a project at Dadri to integrate solar thermal with one of the conventional coal based unit.
It is expected that cost of CSP will drop drastically due to improvement in efficiency and also due mass production of equipment. Several experts believe that in 2-3 years the cost of CSP may drop below the cost of fossil based electric power.
India has 4533 MW of Installed capacity of biomass based power plants. In this system biomass, bagasse, forestry and agro residue & agricultural wastes are used as fuel to produce electricity. Nearly 750 million tons of non-edible (by cattle) biomass is available annually in India which can be put to use for higher value addition. India has been promoting biomass gasifier technologies in its rural areas, to use surplus biomass resources such as rice husk, crop stalks, small wood chips, and other agro-residues. The Largest Biomass based power plant in India is at Sirohi, Rajasthan having the capacity of 20 MW, i.e., Sambhav Energy Limited. In addition, gasifier systems are being installed at 60 rice mills in India.
Geothermal energy is thermal energy generated and stored in the Earth. India's geothermal energy installed capacity is experimental. Commercial use is insignificant. According to some ambitious estimates, India has 10,600 MW of potential in the geothermal provinces but it still needs to be exploited. Feasibility studies are being carried out for a 20 MW commercially viable power plant at Tattapani in Chattisgarh by NTPC .
Thus we can see that in future thrust for power generation will be on renewable technologies like solar, wind and nuclear although USC technologies will be deployed in large proportion as coal is going to be main stay for power generation. Thrust on renewable technologies will help to maintain environment issues to some extent.
Director (Commercial & Operation) PTC Delhi
Dr A.P. Dash
Sr Faculty, Power Management Institute, NTPC
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