Besides solar, wind and biomass, there are other eco-friendly and renewable sources from which energy can be tapped for varied applications. MNES is sponsoring various R&D programmes to develop the technologies for exploitation of above sources. These are

1. Chemical Sources of Energy– Fuel Cells
2. Hydrogen Energy
3. Alternative Fuel for Surface Transportation—Battery operated Vehicles
4. Geothermal Energy
5. Ocean and Tidal Energy
6. Bio-fuels

Fuel Cell

Fuel cell is an electrochemical device that converts the chemical energy of a fuel directly and very effectively into electricity (DC) and heat, without combustion. The most suitable fuel for such cells is hydrogen or a mixture of compounds containing hydrogen. A fuel cell consists of an electrolyte sandwiched between two electrodes. Oxygen passes over one electrode and hydrogen over the other, and they react electrochemically to generate electricity, water, and heat.

Fuel cells are capable of converting 40% of the available fuel to electricity. This can be raised to 80% with heat recovery. The fuel cell has no moving parts, therefore it is highly reliable source of energy.

Fuel cell system efficiency is independent of the rated power above 100 kW, unlike oil, gas or coal burning power plants, where the efficiency is constant only at the megawatt power level. Even at the 40% of the rated load, a fuel cell has almost the same efficiency as that of the full load. They are also able to respond in fast load changes, because the electricity is generated by a chemical reaction and are eco-friendly with little or no air pollution.

Fuel cells are classified primarily by the kind of electrolyte they employ. This determines the kind of chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors. These characteristics, in turn, affect the applications for which these cells are most suitable. There are several types of fuel cells currently under development, each with its own advantages, limitations, and potential applications. A few of the most promising types include

1. Proton Exchange Membrane (PEM)
2. Phosphoric Acid (PAFC)
3. Solid Oxide (SOFC)
4. Alkaline (AFC)
5. Direct Methanol (FMFC)
6. Molten Carbonate (MCFC)

Hydrogen Energy

Hydrogen can be used to combine with the oxygen in the air, converting it into water while producing the heat and electricity. It is like a battery, except that a fuel cell does not run down or require recharging like a battery. It recharges itself while you are drawing power. Hydrogen is commonly available in fuels like propane and natural gas. Fuels that contain hydrogen include:

1. Methanol
2. Ethanol
3. Natural gas
4. Gasoline
5. Diesel fuel

Hydrogen energy is a clean and abundant energy source. When used in a fuel cell, the only emission created is water - no burning or combustion therefore no pollutants. The water can be electrolyzed to make more hydrogen which supplies more fuel.

Hydrocarbons, water and oxygen are processed through a fuel processor (also called a reformer) to produce hydrogen, carbon dioxide and carbon monoxide.

Water is added and carbon monoxide is converted to carbon dioxide plus hydrogen. The hydrogen produced is then ready for conversion in the fuel cell itself which consists mainly of two electrodes, the negative anode and the positive cathode, separated by an electrolyte - in this case a polymer electrolyte membrane (PEM). The electrodes are coated on one side with a catalyst that helps the process. The catalyst is a special material that facilitates the reaction of oxygen and hydrogen.

Pressurized hydrogen fuel enters the anode side and air enters the cathode side. Helped by the catalyst, the hydrogen molecule splits into two protons and two electrons. The hydrogen has a negative and positive charge like a battery, As the hydrogen molecules enter the negative electrode, they split in two forming protons and electrons.

The hydrogen enters the fuel cell where the electrons (negative charge) flow out of the fuel cell as electricity. The protons (positive charge) travel across the PEM and combine with oxygen from the air. This chemical reaction creates molecules of water that leave the fuel cell and generate heat from this process, as well as supply the positive side needed to complete the electrical circuit.

Battery Operated Vehicles

Battery operated Vehicles run by an electric motor, powered by a pack of rechargeable tract ion batteries positioned in the vehicle Itself. The power transmission takes place through conventional gear box and differential gear box. The speed is controlled by an Electronic Chopper Controller and gear changing. In all other respect such as steering braking, gear box and clutch arrangements etc. Electravans are similar to conventional diesel or petrol vehicles. Therefore they need no extra training to drive.

Optional battery withdrawal arrangement is provided with facilities for removal of discharged batteries and fitting of charged ones within few minutes at the battery charging stations.

In view of the obvious advantages of Electravans, Ministry of Non-conventional Energy Sources, Government of India, gives a cash subsidy to the buyers. Electravan usage is being increasingly favoured to fight the menace of air pollution in urban areas, industries & institutions.

Advantages:

• Freedom from highly discomforting noise & vibrations so common in diesel vehicles.
• Recurring savings of petrol or diesel.
• Ideal vehicle to keep environment clean.
• Ideally suited as public transport in congested areas, hospitals, factories, wild life sanctuaries, airport, schools & places of historic Importance.

No engine related maintenance expenses & much lesser maintenance OPI chassis pails due to absence of vibrations.

The Central Electrochemical Research Institute (CECRI), Karaikudi is developing high-energy lithium polymer batteries of 1 ah capacity with a life cycle of 350 yrs for vehicular traction. CECRI has already synthesized and characterized LiCoO cathode active material and completed the optimisation of polymer electrolyte films and basic cell studies. The charge-discharge studies indicated cell efficiencies of more than 60%

The project sanctioned at the Center for Materials for Electronics Technology (C-MET), Pune, envisages the development of novel route synthesis, characterisation and electrochemical studies on high quality cathode materials for rechargeable lithium batteries for electric vehicle use. Lithium manganese oxide is one of the cathode materials for lithium batteries. C-MET has developed cathode materials and characterised by using different characterization techniques. Work is in progress for the development of prototype lithium cells and for optimisation of various parameters

The Ministry of Non-conventioanl Energy Source is implementing a programme on battery operated vehicles (BOVs) which includes battery operated passenger three wheeler and battery operated passenger cars, besides battery operated buses through State Nodal Agencies and Departments in the States and Union Territories. The programme provided subsidy for the purchase of these types of indigenously manufactured vehicles. Under this programme, a total of 21 BOVs were procured by different agencies through State Nodal Agencies during 2004-2005. The existing programme of battery operated vehicles has met its objectives and from fiscal 2005-06 will be replaced by the hybrid vehicle programme.This programme provides subsidy for the following types of Battery Operated Vehicles

• Central Subsidy is being provided for ten and more seaters Battery Operated Buses/Mini buses @ 33 per cent of the cost of vehicle (exclusive of excise duty, sales tax and all other levies) or Rs.3.50 lakh per vehicle;
• Eight and more seater Battery Operated Passenger Three Wheelers @ 33 per cent of the cost of the vehicle (exclusive of excise duty, sales tax and all other levies), or Rs.80,000 per vehicle; and
• Four seater Battery Operated Passenger Cars @ 33 per cent of the cost of vehicle (exclusive of excise duty, sales tax and all other levies), or Rs.75,000 per vehicle.

Geothermal Energy

Geothermal energy is energy coming out of the molten interior of the earth towards the surface. The average rate at which this heat emerges is about 0.05 W/m2, while the radial temperature gradient which causes this heat flow is about 0.03oC per metre. Thus, on an average, the temperature of the earth increases by 30oC per kilometer as one move inwards.

Because of non-homogeneities in the earth's crust, there are numerous local hot spots just below the surface where the temperature is in fact much higher than the average value expected. Ground water comes into contact with the hot rocks in some of these locations and as a result, either dry steam or wet steam and water are formed. A well drilled to these locations causes the dry or wet steam to emerge at the surface where it s energy can be utilized either for generating electricity or for space heating.

The first commercial geothermal power station was erected in Larde-rello in Italy in 1904. The capacity of the plant was increased in stages and was 406 MW in 1975. Other locations where relatively large plants are operating are in The Geysers, California, U.S.A. (600 MW) and in Wairakei, New Zealand (190 MW). The total installed capacity in the world in 1975 was about 1500 MW.

This estimate indicates that about 62500 MW could be generated for a period of 50 years. The geothermal is the heat stored locally at depths of 1 or 2 km in the earth's mantle in hot dry rocks with which water has not come into contact. Utilization of these sources required development of techniques for artificial fracture of the rocks, the injection of water into the fractures and subsequent recovery of the steam for driving turbines.

In India, geothermal resources in the form of steam and hot water are known to exist along the West Coast, in Ladakh, and in parts of Himachal Pradesh. However, no firm estimates of their potential are available.

Ocean and tidal Energy

Tides are generated primarily by the gravitational attraction between the earth and the moon. They arise twice a day. In mid-ocean, the tidal range is only a metre or less, but in some coastal estuaries, it is much greater. This is due to the amplification of the tidal wave as it moves up the narrowing channel of the estuary.

Basically, in a tidal power station, water at high tide is first trapped in an artificial basin and then allowed to escape at low tide. The escaping water is used to drive water turbines which in turn drive electrical generators.

Jeffreys has estimated that the rate of tidal energy dissipation for the world is about 3X106 MW. However, only a small fraction of this can be exploited since, for practical purposes, one needs a certain minimum difference of level between the high and low tides. In addition, the geography of a location has to be suitable from the point of view of the civil construction involved. Hubbert has compiled the available information on favourable locations and the tidal power which can be generated at each of them, and estimates that a maximum capacity of 63800 MW can be harnessed. Some of the major sites are in the Bay of Fundy in North America, in the White Sea in U.S.S.R., and in Mont Saint Michel in France.

The first commercial tidal power station in the world was constructed in France in 1965 across the mouth of the La Rance Estuary. It has a capacity of 240 MW. The average tidal range at La Rance is 8.4 m and the dam built across the estuary encloses an area of 22 km2.

In India, tidal power could probably be generated in Kutch and in the Hooghly river. In both these areas, an adequate head is known to exist. However, specific locations have not been identified and estimates of the amount of power which could be generated have to been made.

Wave energy arises because of the interaction of the winds with the surface of the oceans. It could therefore be considered as one of the indirect ways of utilizing solar energy. The energy available varies with the size and frequency of the waves. However, on an average, it is estimated that about 10 kW are available for every metre of wave front. Due to the wide fluctuations in frequency and amplitude at any location, wave energy is difficult to collect from a practical standpoint. In addition, devices built for the purpose have to transfer the collected energy ashore and have to be strong enough to cope with adverse weather conditions. In spite of these problems, research for utilizing wave energy is in progress in many countries and many experimental devices have been built. If this research is eventually successful, it is possible that these devices could help to meet the local needs of small coastal communities.

Biofuels

Biofuels are fuels derived from biomass - recently living organisms or their metabolic by-products. Agricultural products specifically grown for use as biofuels include corn, sunflower and soybeans. In India, the physic nut (jatropha curcas) and the Indian beech (pongamia pinnata) are favored for their drought resistance and ability to grow in marginal soils, thereby reducing demand on arable soils needed for food production.

Biofuels are used as a direct replacement for energy and industrial fuels such as HFO, or can be easily processed into biodiesel, an alternative to petroleum-based diesel fuel.

Biodiesel is a renewable fuel that can replace petro diesel in current engine specifications without alteration and can be transported and sold using existing infrastructure. Biodiesel is non-flammable, and in contrast to petroleum diesel it is non-explosive, with a flash point of 150°C for biodiesel as compared to 64°C for petro diesel. Unlike petro diesel, it is biodegradable and non - toxic, and significantly reduces toxic and other emissions when burned as a fuel.

Chemically, it is a comprised of a mix of mono-alkyl esters of long chain fatty acids. A lipid transesterification production process is used to convert the base vegetable oil to the desired esters and remove free fatty acids (de-gumming). The most common form uses methanol as an additive to produce methyl esters, though ethanol can be used to produce an ethyl ester biodiesel. A by-product of the transesterification process is the production of glycerol, which is traditionally used in the cosmetics and food industry.

After processing, unlike straight vegetable oil, biodiesel has very similar combustion properties to petroleum diesel, and can replace it in most current uses. However, it is most often used as an additive to petroleum diesel, improving the otherwise low lubricity of pure ultra low sulphur petro diesel fuel.