Many hurdles to harnessing the tides boundless energy

Written by ASHOK B SHARMA | Updated: Aug 27 2008, 04:18am hrs
Generation of power from ocean tides holds out the promise of helping to meet Indias burgeoning energy needs. Oceans store renewable energy in the form of temperature gradients, waves, tides and ocean currents, which can be used to generate electricity in an environment-friendly manner, if the aspects of coastal ecology are carefully considered Countries like France, Russia, China, Canada, the UK and Korea all make use of tidal energy on a commercial basis. According to one estimate, around 30-lakh mw of power is continuously dissipated through the motion of tides across the globe. However, we have still managed to tap only a small fraction from this source.

The first large-scale modern tidal electric plant of 240 mw was launched on November 26, 1966 at La Rance in France and is reported to be operating successfully. China has set up some small-capacity tidal plants. Canada has set up a 20 mw tidal power plant. In the UK, a major tidal power plant is being envisaged in Wales, where extensive technological, environmental, sediment dynamics and other aspects of associated problems have been investigated for more than a decade.

According to one estimate Indiawhich is bounded by seas on three sideshas the potential to harness10,000 mw of energy from ocean tides. Ideal sites are the Gulf of Kutch, Gulf of Cambay and the Ganga delta (the Sunderbans) in West Bengal. Preliminary studies indicate a tidal potential of 6,000 mw in the Gulf of Cambay and 1,000 mw in the Gulf of Kutch. The Sunderbans of West Bengal have a potential for smaller tidal power plants of 1-10 mw.

One of the main reasons for the slow pace in tidal power generation is the extremely high cost of exploration and exploitation. Extensive investigations on technological, environmental and sediment dynamics are needed before setting up a power plant. However, harnessing tidal power is more economical in the long run due to the perpetual nature of this abundant energy source.

Though India has yet to see a single tidal power station, some preliminary techno-economic feasibility studies have been conducted. The Central Electricity Authority (CEA) completed one such study in 1988 to set up a 900-mw station in the Gulf of Kutch. The irrigation & power department of the Orissa government completed a preliminary survey in 1983 on the tidal power potential of the Panchapada river in Balasore district. The CEA in 1992 conducted a preliminary survey to assess the techno-economic feasibility of generating tidal power around the Andaman & Nicobar Islands.

The Union ministry of new & renewable energy sources supports the setting up of a 3.65-mw demonstration tidal power at Durgaduani Creek in the Sunderbans in West Bengal through the West Bengal Renewable Energy Development Agency. The main objective of the project is to supply power to 11 villages in Gosaba and Bali Bijaynagar islands in South 24-Parganas district. A detailed project report is under consideration.

Tidal power is created by the periodic rise and fall of ocean waters, which leads to differences in water levels, thereby creating water pressures that can drive turbines. A tidal power plant involves construction of a relatively long barrage across an estuary to create a large basin on the landward side. The basin is filled during high tide through a number of sluices.

Turbo-generators capable of efficient generation at low heads and consequently handling large flows are installed in the tidal barrage.

Energy can be produced during ebb tide (falling tide) or rising tide or in both phases if compatible turbines are installed. Single-basin single-effect, single-basin double-effect and double-basin single-effect are the possible options that are engaging the attention of experts worldwide.