Renewable Energy

Securing Future with Clean and Green Technologies

Generation of energy

All the energy we consume is generated by using the three fundamental interactions of nature : gravity, electromagnetism and the nuclear reaction to create force, fission and fusion. Most forms of terrestrial energy can be traced back to fusion reaction inside the Sun. Geothermal energy is believed to be generated primarily by radioactive decay inside the Earth. Radioactive decay energy is generated by both the nuclear and electromagnetic force. Tidal energy comes from the gravity energy and kinetic energy of the Earth / Moon system.

The Concept

The contemporary non - conventional sources of energy like wind, tidal, solar etc. were the conventional sources until James Watt invented the steam engine in the eighteenth century.

In fact, man travelled around the world using wind - powered ships. The non - conventional sources are available free of cost, are pollution - free and inexhaustible. Man has used these sources for many centuries in propelling ships, driving windmills for grinding corn and pumping water, etc. Because of the poor technologies then existing, the cost of harnessing energy from these sources was quite high. Also because of uncertainty of period of availability and the difficulty of transporting this form of energy, to the place of its use are some of the factors which came in the way of its adoption or development. 

The use of fossil fuels and nuclear energy replaced totally the non - conventional methods because of inherent advantages of transportation and certainty of availability; however these have polluted the atmosphere to a great extent. In fact, it is feared that nuclear energy may prove to be quite hazardous in case it is not properly controlled.

In 1973 the Arab nations placed an embargo on petroleum. People began to realise that the fossil fuels are not going to last longer and that remaining reserves should be conserved for the petro-chemical industry. But unfortunately, both nuclear and coal energy pose serious environmental problems. The combustion of coal may upset the planet’s heat balance. The production of carbon - dioxide and sulphur - dioxide may adversely affect the ability of the planet to produce food for its people. Coal is also a valuable petro - chemical and from long term point of view it is undesirable to burn coal for generation of electricity. The major difficulty with nuclear energy is waste disposal and accidental leakage (e.g. leakage at Chernobyl nuclear power plant, Ukraine).

As a result of these problems, it was decided by almost all the countries to develop and harness the non - conventional sources of energy, even though they are relatively costlier as compared to fossil-fuel sources. It is hoped that with advancement in technology and more research in the field of development of non-conventional sources of energy, these sources may prove to be cost-effective as well. The future of wind, solar, tidal and other energy sources is bright and these will play an important role in the world energy scenario.

Renewable energy sources also called non - conventional energy are sources that are continuously replenished by natural processes. For example, solar energy, wind energy, bio - energy and fuels grown sustainably, hydropower etc., are some of the examples of renewable energy sources

A renewable energy system converts the energy found in sunlight, wind, falling-water, sea-waves, geothermal heat, or biomass into a form, we can use such as heat or electricity. Most of the renewable energy comes either directly or indirectly from sun and wind and can never be exhausted, and therefore they are called renewable.

However, most of the world's energy sources are derived from conventional sources - fossil fuels such as coal, oil, and natural gases. These fuels are often termed non - renewable energy sources. Although, the available quantity of these fuels are extremely large, they are nevertheless finite and so will in principle 'run out' at some time in the near future.

Renewable energy sources are essentially flows of energy, whereas the fossil and nuclear fuels are, in essence, stocks of energy

Various forms of renewable energy :

Solar energy

Solar energy is the most readily available and free source of energy since prehistoric times. It is estimated that solar energy equivalent to over 15,000 times the world's annual commercial energy consumption reaches the Earth every year.

 

Wind energy

Wind energy is basically harnessing of wind power to produce electricity. The kinetic energy of the wind is converted to electrical energy. When solar radiation enters the earth's atmosphere, different regions of the atmosphere are heated to different degrees because of earth curvature. This heating is higher at the equator and lowest at the poles. Since air tends to flow from warmer to cooler regions, this causes what we call winds, and it is these airflows that are harnessed in windmills and wind turbines to produce power.

Wind power is not a new development as this power, in the form of traditional windmills - for grinding corn, pumping water, sailing ships - have been used for centuries. Now wind power is harnessed to generate electricity in a larger scale with better technology.

Bio energy

Biomass is a renewable energy resource derived from the carbonaceous waste of various human and natural activities. It is derived from numerous sources, including the by - products from the wood industry, agricultural crops, raw material from the forest, household wastes etc.

Biomass does not add carbon dioxide to the atmosphere as it absorbs the same amount of carbon in growing as it releases when consumed as a fuel. Its advantage is that it can be used to generate electricity with the same equipment that is now being used for burning fossil fuels.

Biomass is an important source of energy and the most important fuel worldwide after coal, oil and natural gas. Bio - energy, in the form of biogas, which is derived from biomass, is expected to become one of the key energy resources for global sustainable development.

Hydro energy

The potential energy of falling water, captured and converted to mechanical energy by waterwheels, powered the start of the industrial revolution.

Wherever sufficient head, or change in elevation, could be found, rivers and streams were dammed and mills were built. The turbine will spin when water under pressure flows through it. The Turbine is connected to a generator, which produces electricity. In order to produce enough electricity, a hydroelectric system requires a location with the following features:

Change in elevation or head : 20 feet @ 100 gal / min = 200 Watts.

100 feet head @ 20 gal / min gives the same output.

Geothermal energy

The word geothermal comes from the Greek words geo (Earth) and therme (heat). Geothermal energy is heat from within the Earth.

Geothermal energy is generated in the Earth’s core, almost 4,000 miles beneath the Earth’s surface. The double - layered core is made up of very hot magma (melted rock) surrounding a solid iron centre. Very high temperatures are continuously produced inside the Earth by the slow decay of radioactive particles. This process is natural in all rocks.

Surrounding the outer core is the mantle, which is about 1,800 miles thick and made of magma and rock. The outermost layer of the Earth, the land that forms the continents and ocean floors, is called the crust. The crust is three to five miles thick under the oceans and 15 to 35 miles thick on the continents.

The crust is not a solid piece, like the shell of an egg, but is broken into pieces called plates. Magma comes close to the Earth’s surface near the edges of these plates. This is where volcanoes occur. The lava that erupts from volcanoes is partly magma. Deep underground, the rocks and water absorb the heat from this magma.

We can dig wells and pump the heated, underground water to the surface. People around the world use geothermal energy to heat their homes and to produce electricity.

Geothermal energy is called a renewable energy source because the water is replenished by rainfall and the heat is continuously produced deep within the Earth. We won’t run out of geothermal energy.

Wave and tidal energy

Tidal Energy

Tidal electricity generation involves the construction of a barrage across an estuary to block the incoming and outgoing tide. The head of water is then used to drive turbines to generate electricity from the elevated water in the basin as in hydroelectric dams.

Barrages can be designed to generate electricity on the ebb side, or flood side, or both. Tidal range may vary over a wide range (4.5 - 12.4 m) from site to site. A tidal range of at least 7 m is required for economical operation and for sufficient head of water for the turbines.

Ocean Energy

Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. Ocean energy draws on the energy of ocean waves, tides, or on the thermal energy (heat) stored in the ocean. The sun warms the surface water a lot more than the deep ocean water, and this temperature difference stores thermal energy.

The ocean contains two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves.

Ocean thermal energy is used for many applications, including electricity generation. There are three types of electricity conversion systems : closed - cycle, open cycle, and hybrid.

Closed cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a low boiling point, such as ammonia. The vapour expands and turns a turbine. The turbine then activates a generator to produce electricity. Open - cycle systems actually boil the seawater by operating at low pressures. This produces steam that passes through a turbine / generator. The hybrid systems combine both closed - cycle and open - cycle systems.

Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. A barrage (dam) is typically used to convert tidal energy into electricity by forcing the water through turbines, activating a generator.

Bio-mass Briquette / Eco-coal

Biomass briquetting is the densification of loose biomass material to produce compact solid composites of different sizes with the application of pressure. Briquetting of residues takes place with the application of pressure, heat and binding agent on the loose materials to produce the briquettes. 

The advantages of briquette

• This is one of the alternative methods to save the consumption and dependency on fuel wood 
• Densities fuels are easy to handle, transport and store 
• They are uniform in size and quality 
• The process helps to solve the residual disposal problem 
• The process assists the reduction of fuel wood and deforestation 
• Indoor air pollution is minimised 

The raw materials for biomass briquetting can be

• Agricultural residues (husks, cob, stalks, leaves, stems, shells, sticks) 
• Invasive plants (Banmara, Lantana camera, Euphorbia royalena, Congress grass) 
• Waste from bio-product industries like sawmills, plywood industries, furniture factories 

Briquettes a promising fuel 

Briquettes produced from briquetting of biomass are fairly good substitute for coal, lignite, firewood and offer numerous advantages.


The briquettes can be used for domestic purposes (cooking, heating, barbequing) and industrial purposes (agro-industries, food processing) in both rural and urban areas.

Indian Context

The oil shocks of 1970s led to spiralling crude oil prices in the world market which prompted planners to view energy security as an issue of national strategic importance. Energy security has an important bearing on achieving national economic development goals and improving the quality of life of the people. India’s dependence on crude oil will continue for most part of the 21st century. In addition, global warming, caused largely by greenhouse gas emissions from fossil fuel energy generating systems, is also a major concern. India needs to develop alternate fuels considering the aforesaid two concerns.

Fossil fuels supply most of the energy consumed today. They are relatively concentrated, pure energy sources, technically easy to exploit, and provide cheap energy. Presently Oil 40%, Natural gas 22.5%, coal 23.3%, hydroelectric 7.0%, nuclear 6.5%, biomass and others 0.7% provide almost all of the world's energy requirements.

However the reserves of fossil fuels are limited as under :

• Conservative predictions are that conventional oil production will last for another five decades
• The pessimists predict a peak for conventional gas production between 2010 and 2020
• There are today five decades of economically exploitable reserves of coal at the current rate of consumption
• The raw material for nuclear power i.e. uranium reserves will last for 50 years at the present rate of use

(Though there are other alternatives raw material such as thorium but this technology is yet to be developed)

Hence it is the need of the hour to explore and develop renewable energy sources to meet with ever growing demand of energy.

Renewable Energy Technologies (RETs) are increasingly being viewed as an equitable and environmentally sound way of addressing the energy concerns in the country - low per capita energy consumption, inequalities in access, supply constraints, growing dependence on imports, and high environmental costs.

Rural energy demand still to a large extent is met by non - commercial energy sources such as firewood, cattle dung and crop residues. The real cost of using these fuels - in terms of the time spent in collection, storage and preparation; the health implications of indoor air pollution caused by the use of these fuels; and potential environmental damage caused by deforestation and desertification - is extremely high.

Over the last few years, the technical, operational and economic viability of RETs has led to a surge of interest in their applications. RETs can contribute substantively towards meeting grid and off - grid energy needs. Several technologies for grid connected power generation such as using wind; small hydro and biomass are proven technologies which are in large scale application in the country. In addition, RETs offer possibilities of distributed generation in sparsely populated or far - flung areas where extension of the grid may be unviable. A niche area for RETs is a range of thermal applications both in rural and urban centres.

Applications such as solar air and water heating systems, solar cookers, solar buildings, as well as energy recovery from urban, industrial and agricultural wastes are becoming popular in urban, semi-urban and rural centres. Perhaps the most wide spread application potential of RETs is in rural areas for purposes of cooking, lighting, water pumping, agro and rural industries, where the growth of RETs also creates significant employment opportunities.

Useful Links :

Ministry of MNRE India

India’s 450GW renewable energy goal

Carbon Fiber - The future metal

The best advice on energy efficiency - Renewable Energy

Keywords: Renewable Energy, Solar Energy, Future Energy Solutions