Going green for power generation

Written by ASHOK B SHARMA | Updated: Oct 15 2007, 19:55pm hrs
India intensifies its search for technologies to tap large-scale renewable energy from new sources like tidal currents and geo thermal reservoirs, reports Ashok B Sharma.

Imagine powerful tidal currents from the Oceans being used to generate renewable, emission-free electricity. Or geothermal power generated by mining the Earths heat. Sounds incredible but extraordinary times demand extraordinary solutions, especially in meeting global needs to provide large-scale, firm, renewable energy.

Failing to achieve the target for power generation from the existing operational renewable sources in the country, the government is in search of new sources like tidal energy and geothermal energy for meeting the energy requirements. At present, renewable energy contributes only about 3% of total energy consumption and 6% of the total power generation capacity. This is despite the fact that India is fourth in the world in generation of wind energy, seventh in generation of solar photovoltaic power and second in the world in biogas and biomass gasifier sectors.

Says SK Chopra, principal advisor and special secretary in the Union ministry for new and renewable energy, India is deficit in energy and the total import of primary and commercial energy increased from 18.85% in 1991 to 30% of the total primary commercial energy supply in 2004-05. We need to make a quantum jump in power generation from renewable sources not only for our energy security, but also for sustainable and eco-friendly means of energy generation. Generation of power from renewable sources is also necessary for electrifying remote villages that cannot be connected through power grid, he adds.

In this direction, the setting up of a tidal power project at Durgaduani, West Bengal has been conceived. A study has also been undertaken to explore the feasibility of another tidal power project in Gujarat.

The government is also exploring the potential for tidal power generation in other regions like Andaman & Nicobar Islands. Typically, for harnessing tidal energy, a barrage is created to tap water during high tide. At the time of a low tide, water flows back to the seaen route it passes through turbines connected to generators that produce electricity. Though with the present status of Ocean energy technology, it is possible to harness tidal energy for large-scale power generation, the ministry of earth sciences is in search of new technologies to effectively tap energy from tidal waves and ocean currents.

Then, geothermal energy is another source where the government has planned a major initiative.

This form of energy is derived from natural heat contained inside the Earth. Accordingly, as per global norms, geothermal reservoirs are classified. Those reservoirs having temperatures exceeding 150 degree Celsius are suitable for power generation, while those having temperatures less than 150 degree Celsius can be used for space heating and in greenhouses.

The government has already assessed the existing geothermal energy potential at Tattapani in Chhattisgarh and Puga Valley in Ladhak. Initial studies reveal the presence of geothermal fields in the Himalayan range, North Eastern and North Western India.

All geothermal fields and prospects are located in the vicinity of plate tectonics boundaries. A suite of exploration techniques, namely, geological, geochemical, geophysical, airborne survey and remote sensing are deployed. Assessment and exploitation of geothermal resources includes drilling, reservoir physics and engineering and production technology. Basic concepts of heat transfer and quantitative relations for heat flow for some geometrically simple bodies are defined. Geothermal energy development, therefore, draws experts from diverse traditional disciplines like geology, geophysics, engineering and investment study.

While India has just commenced plans to tap geothermal energy, Italy began tapping energy from geothermal steam at Larderello way back in 1904. In fact, this was the worlds first geothermal project. Today, more than 20 countries make direct use of geothermal energy. For several small countries, such as Iceland and the Philippines, geothermal energy constitutes a significant percentage of total electricity generation.

As of now, globally, the installed capacity for geothermal power generation is over 8,000 MW per year and indirect use of geothermal energy is over 15,000 MW. The Cerro Prieto geothermal field in Mexico, with an installed capacity of 720 MW, is among the three largest producing geothermal fields in the world.

The government has drawn up a roadmap for the period till 2030 and has proposed an increase in the renewable power installed capacity to 15%, solar cell efficiency to 30%, generation of 30 million tonne of bio-fuel per year and use of hydrogen, bio-fuel and fuel cell as alternate fuels.

Also, the ambitious National Hydrogen Energy Road Map was approved a year ago for energy generation. This, by means of clean coal gasification technologies, biological routes, from solar energy by use of electrolysis, photolytic, photo electro-chemical and thermal splitting processes.

Hydrogen storage was stipulated in hydrates and carbon nano-structures. Fuel cell is an electrochemical device in which hydrogen and oxygen combine in the presence of electrolyte to produce electricity and water. The use of hydrogen in motorcycles, three-wheelers, power generating units, catalytic combustors and air conditioning has also been successfully demonstrated.