The Hindu Business Line : Plumbing the seabed to tap raw energy reservoir

EVEN as they scan the Space to track down an assured source for supplying quality power to the mission-critical requirements of the digital economy, scientists are plumbing the depths of the sea in the hope of tapping an as yet untamed reservoir of `raw energy'.

Large reserves of methane hydrates contained in seafloor sediments and the Arctic permafrost are extensively being evaluated as a potential energy source for the future.

Some believe there is enough methane (the primary component of natural gas) in the form of hydrates (methane locked in ice) to supply energy for hundreds, maybe thousands, of years.

In the 1970s, hydrates were found in ocean sediments. Estimates on how much energy is stored in methane hydrates range from 350 years' supply to 3,500 years' based on current energy consumption.

"That reflects both their potential as a resource and how little we really know about them," says Mr N.T. Nair, Technical Advisor to the Energy Management Division of CMS Computers, Thiruvananthapuram.

In a presentation at a session organised here by the KSEB (Kerala State Electricity Board) Post-Graduate Engineers Association here, he explained that gas hydrates are clathrate compounds.

A clathrate is simply a structure in which water molecules under certain conditions bond to form an ice-like cage that encapsulates a gas molecule, known as a guest molecule. When that guest is a methane molecule, you have methane hydrate.

In fact, the name "clathrate" comes from the Latin word meaning "to enclose with bars." They form at low temperature and high pressure. Occurring naturally both in permafrost regions where cold temperatures persist in shallow sediments, and at ocean depths of 500 metres or more where high pressures dominate, these unique structures encase methane at very high concentrations.

In fact, a single unit of hydrate can release as much as 160 times its volume in gas when heated and depressurised. Hydrates are typically found a few metres below the ocean floor in layers a few hundred metres thick.

Energy for future: Natural gas is certain to take on a greater role in power generation in the near term due to increasing pressure for clean fuels and the relatively low capital and operating costs of new natural gas-fired power equipment. But methane hydrate offers itself as a seemingly inexhaustible source for the future.

The role of methane hydrates in a warming world is also a concern, though. Much of the gas hydrate in the world is close to melting and a slight temperature increase may induce a massive release of methane gas - a greenhouse gas 10 to 20 times more powerful than carbon dioxide.

Also, the enormous hydrate reservoirs are of little use unless economically profitable techniques are devised to extract the methane.

Unfortunately, the current level of technology and the market rate for gas from land-based reserves make extracting methane hydrates uneconomical.

Apart from the US and other developed countries, several resource-poor countries such as Japan and India have already begun researching methane hydrates. The Japan National Oil Company has invested $60 million on a hydrate research programme.

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