6 Renewable Energy Resources
Dr. Dhanya M.S M.S
1. Introduction
The world is looking for alternate energy sources that can overcome the limitations of fossil fuels. Now a day’s renewable energy plays a very significant role. It gave a chance to us to reduce carbon emissions, clean the air and prevent global warming of planet earth.
The renewable energy is defined by US EPA as the resources that rely on fuel sources that restore themselves over short periods of time and do not diminish. These energy sources are also non – conventional sources of energy.
2. Characteristics of a renewable energy sources
Renewable energy sources are regenerated in natural processes It can be used indefinitely.
These are available in great amount or abundant in nature and It develops in a relatively short period of time.
These include solar energy; wind energy; ocean thermal power; wave and tidal energy; geothermal energy; hydropower etc. They are capable of solving the twin problems of energy supply in decentralized manner and helping in sustaining cleaner environment.
- Solar Energy
Among renewable energy sources, the easily accessible and most important is the solar energy. It can be used directly or indirectly for human welfare. The direct solar energy is the radiant energy whereas the indirect solar energy is the energy obtained from the materials such as biomass, in which sun’s radiant energy has been incorporated by the plants.
3.1 Direct Solar Energy. On global scale, 15 days of solar energy is roughly equivalent to the energy stored in all known reserves of fossil fuels on the earth. The continuous input of the energy from the sun is 1, 67,000 times greater than the current consumption. Solar energy can be used for direct heating. Alternatively, the heat can be converted into the electricity-the thermal electric generation. Photovoltaic cells-the solar cells or solar batteries covert direct solar energy into electricity. Other types of solar energy devices are solar power pumps and solar pond electric power plant. Thus the solar energy can be harnessed for domestic, commercial or industrial purposes.
In tropical countries like India, the use of solar energy could prove systems most suitable in the long run as sunlight is available in plenty, almost throughout the year. India has been one of the major producers of photovoltaic systems, currently used in Street Lighting (SLs), Domestic Lighting Systems (DLS), Community Lighting Systems (CLs), water pumping systems, small power plants, solar cookers etc. India installed largest solar steam cooking system for cooking food for 15,000 people per day at Tirupati Temple in Andhra Pradesh.
3.2 Indirect Solar Energy (Biomass) Biomass energy, where solar energy is utilised indirectly, has been the major source of energy to human beings throughout the history of civilization. Biomass energy is the outcome of the photosynthesis. It is bestowed in the materials such as live plant material and their dried residues; fresh water and marine algae; and agricultural and forest residues of plant and animal origin. Apart from these materials, biomass also includes biodegradable organic wastes from industries like sugar mills, breweries etc. Biomass fuel may be solid such as wood, animal dung, peat, charcoal etc. used for burning; liquid such as methanol or ethanol used in internal combustion engines of automobiles; or gas such as animal waste produced biogas: a mixture of gases mainly methane and some carbon dioxide produced in biogas digesters. Biogas is a clean anaerobic fuel of organic origin whose combustion produces fewer pollutants than other combustible energy sources. Although production of energy requires sufficient area of land and water, but in its various forms, biomass energy appears to have a bright future as a source of energy. At least half of the global population relies upon biomass as main s source of energy for domestic use. Firewood is most widely used biomass quite common fuel in the world.
- Hydro Energy or Water Power
Water power has been in use since the period of Roman Empire. Water falling from a height turns turbines at the bottom of dams to generate electricity. Presently water power is widely used all over the world and produces approximately one-fourth of the world’s electricity. Electricity produced by hydro-power is much cheaper than electricity produced by thermal power. Water power is a clean energy source as it does not cause environmental pollution and the electricity produced can be transmitted to long distances through wires or cables. But building a dam leads to several environmental problems such as submergence of plant and animal habitats and displacement of local inhabitants including tribals.
The hydrothermal energy is the largest source of domestic electricity production in Canada (60%), Brazil (84%), Switzerland (55%), Iceland (80%) and Norway (98%) (Darmawi et al., 2013).Countries like Norway, Canada and Brazil have all been utilizing more than 30% of their hydro potential while India ranks fifth in terms of exploitable hydro potential in the world. About 75 per cent of the total electricity consumed in South America is derived from hydro-power. Japan, US, Russia and many other European countries have trapped most of their water sources and harnessed energy to generate electricity.
In India, generation of hydroelectric power was emphasised in the First Five Year Plan when a number of multipurpose projects such as Bhakra Nangal project on river Sutluj, Bokaro in Panchet and Talaiya in Damodar Valley and Hirakund, Rihand, NagarjunaSagar, Kosi, Koyana were launched to generate hydroelectric power, apart from their use for irrigation and other purposes.
- Wind Energy
Wind power has been in use since Chinese and Persian civilization. Wind has propelled ships and driven wind mills to grind grain and pump water in Netherlands during early days. Now, wind is used to generate electricity in various countries. Harvesting wind energy is possible only in the areas that receive fairly continuous winds such as islands, coastal areas and mountain passes.
When gigantic fans, raised on tall towers, are rotated by the wind, its energy can be used for generation of electricity. Since wind power has the potential to give tremendous energy, the day is not far away when the destructive force of air currents of cyclones, typhoons and fierce gales would be tamed.
India occupies the fourth, after China, USA and Germany in wind power generation. Wind mills are used in Rajasthan to draw subsoil water for irrigation. Recently two wind farms of 10 MW each have been established in Tamil Nadu and Gujarat with international cooperation from Denmark.
6. Ocean Energy
The ocean forms a vital source of energy. Ocean energy is obtained in various forms such as ocean tidal and wave energy, ocean thermal energy conversion etc.
6.1 Ocean Tidal and Wave Energy: Ocean tides, produced by gravitational force of sun and moon, contain enormous amount of energy. The high tide and low tide refer to the rise and fall, respectively of the water in the oceans. Tidal energy is harnessed by construction of a tidal barrage. Darns built across the mouth of a river confluence with oceans, permits sea water to flow through small opening filled with propellers, connected to electric turbines. During high tide the sea water flows into the reservoir of barrage and turns the turbines which in turn produces electricity by rotating the generators. During low tide, when the sea level is low, the sea water stored in the barrage reservoir flows out into the sea and again turns the turbines.
Power of ocean waves, which operates on the principle of oscillating water column, has not been exploited to its full potential except as power supplies for navigational aids. India has initiated the wave energy project off the Vizhinijam Fishery Harbour near Trivandrum in Kerala as an indigenous effort. It was expected that on the completion the project would be able to derive an energy output of 4.45 lakhs units per year. The project resulted in a strict reality in 1991 when it started generation of electricity to be fed to the grid of Kerala State Electricity Board.
6.2 Ocean Thermal Energy Conversion (OTEC): The sun warms the oceans at the surface and wave motion mixes the warm water downward to depths of about 100 meters and this mix layer is separated from the deep cold water formed at a high latitudes, by a thermocline. This boundary is sometimes marked by an abrupt change in temperature, more often the change being gradual. Thus, the resulting temperature distribution consists of two layers separated by an interface with temperature differences between them ranging from 10°C to 30°C. The higher values are found in equatorial waters. And these two enormous reservoirs in some oceanic regions, provide the heat source and heat sink required to operate heat engine. The engine using this energy is referred to as OTEC which makes use of the difference in temperature between the two layers of the sea to harness energy which in turn is used to drive turbines for generating electricity. OTEC can also be used to desalinate water, support deep water mariculture and provide refrigeration and air conditioning facilities and can prove as an aid to mineral extraction.
The concept of OTEC was first demonstrated in 1979 when a small plant mounted on a barge off Hawai, USA produced 50 KW gross power. India possesses a huge potential of OTEC which could be of the order of about 500,000 MW, about 150 per cent of the present total installed power generating capacity of the country. Some of the best global OTEC sites are situated off the Indian mainland and near the islands of Lakshadweep, Andaman and Nicobar. In India, an ocean energy cell has been developed at IIT, Chennai to keep pace with the international developments in this area. A US company, M/S Sea Solar Power Inc., is promoting the use of OTEC and the world’s first plant in India is proposed off the coast of Tamil Nadu capacity of 100 MW.
- Geothermal energy
The natural heat from the interior of earth can usefully be converted into energy. This natural heat comes from the fission of radioactive material present in the rocks in the interior of the earth. The idea of harnessing geothermal energy, utilizing dry steam, was developed in Italy as early as in 1904. Natural internal heat of the earth was harnessed by geo-hydro-thermal conversion, hot igneous and geo-pressured systems. Presently, there are several geothermal plants working successfully in USA, New Zealand, Russia, Japan, Mexico and California. Heated groundwater flowing upwards as hot water stream and hot springs-the nature’s geysers, can be used to turn turbines and generate electricity.
In India, natural geysers are common in Kullu and Manali, Manikarn, Sohana and some other places. Assessment of geothermal energy potential of selected sites in Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Jharkhand and Chhattisgarh is being undertaken. Some more field investigations, including deep drilling at potential geothermal sites, would be required before these site can be taken up for development for geopower generation.
- World status of renewable energy consumption
Renewable energysupplies 18% of the world’s total energy consumption (Fig. 1) from traditional biomass, large hydropower and ‘‘new’’renewables (small hydro, biomass, wind, solar, geothermal,and biofuels). Traditional biomass and hydropower represents about 71% and 16% respectively of total renewable energy. In terms of total energy share biomass and large hydropower represents 13 % and 3% respectively (Kumar et al., 2010)
- Indian Scenario of Renewable Energy Consumption:
Importance of renewable (non-conventional) energy sources was recognized in the country in the early 1970s. Today, India has large programme for renewable energy. The activities cover all major renewable energy sources, such as biomass (biogas), solar, wind, ocean, small hydro power plants and other emerging technologies. Several renewable energy systems and devices are now commercially available. The Department of Non-conventional Energy Sources, set up in 1982, has been raised to the Ministry of New and Renewable Energy Sources (MNRE) – the nodal Ministry of Government of India for all matters relating to renewable systems and devices.
India’s commercial energy consumption has been growing fast in recent years keeping pace with high economic growth rate. In India total renewable energy production is 48,069 MW (Ministry of New & Renewable Energy November, 2016). Out of that 46,653.53 MW is Installed Grid Interactive Renewable Power Capacity and 1403.70 is off-grid/ captive power. Total installed capacity and target up to 2022 of Installed Grid Interactive Renewable Power Capacity in India as shown in Table 1.
Table 1-Installed Grid Interactive Renewable Power Capacity in India
Ministry of New & Renewable Energy, November 2016
These renewable energy sources are newer and fast developing which is managed by the Ministry for New and Renewable Energy. In addition to that India had 43,112.43 MW of installed large hydro capacity, which comes under the ambit of Ministry of Power. Apart from Installed Grid Interactive Renewable Power Capacity, off-grid/ captive renewable power capacity in India is 1403 MWEQ as shown in Table 2.
Table 2-Off-grid/ captive renewable power capacity in India
Conclusion
India has the immense potential of renewable energy sources such as solar, wind, geothermal, tidal, biomass, etc. The technologies developed for efficient utilization of these energy sources may help in energy sufficiency of the country