Tenaga Nasional Bhd has earmarked four sites to set up geothermal power plants which will utilise steam generated from hot springs to operate power turbines, said its engineer for renewable energy, generation asset development, Shahrina Abdullah.

The project is currently in the initial stage of phase two where geophysics and sub-surface analysis have been carried out, she said, without revealing the locations for the plants.

"At this stage, we are 60 percent confident the plants will take off," she said, adding that the next stage would include exploratory drilling which was similar to oil drilling and equally expensive.

Sharina said four medium-range sites have been identified and each geothermal plant would have the potential to generate more than two megawatts of electricity.

A large hot spring can generate up to 20 megawatts of power, she said during a recent media retreat on Pulau Tioman.

She pointed out that the hot springs can co-exist alongside the power plants and serve as a tourist attraction.

As for the technology, Shahrina said binary cycle power plants were the most recent development and can accept fluid temperatures as low as 57 degrees Calcius.

A secondary fluid will pass through the moderately hot geothermal water, at a much lower boiling point than water, causing the secondary fluid to emit vapour which will then drive the turbines.

Saying that the thermal efficiency of the plant was typically at about 10 percent, Sharina said, at present, this was the most common geothermal plant being built.

- Bernama