hankyoreh

which has a 350 ton pull up capacity and can drill 5km underground. A 450 ton capacity model is now being developed.

By Jung Dae-ha, Gwangju correspondent

Representatives from AltaRock Energy Inc. - a company whose investors include Google and the US Department of Energy - visited Gwangju on Jan. 22 to sign an investment agreement. That day, the city announced that the American company was planning to invest 82 billion won (US$76.83 million) in the construction of a 3.5MW deep geothermal power plant.

AltaRock is currently developing a power generation complex in Bend, Oregon, in the US, where it will generate electricity from deep geothermal energy.

Why would a company that is backed by Google (which has long invested in alternative energy projects) come to Gwangju? The reason is the “water hammer” drilling method developed by a local SME called Hanjin D&B. The water hammer method is a drilling technique whereby the injection well transmits strong water pressure to the drill bit, moving it up and down like a hammer.

Geothermal power generation is a way to produce energy by extracting geothermal heat at a depth of 4-5km or more below the ground. Deep geothermal energy refers to high-temperature geothermal energy that is found 1,000m or more underground, in contrast from the regular geothermal energy located 500m below the surface. As of 2010, geothermal power plants with a capacity of 10.7GW are operating in the US, the Philippines, and other parts of the world. Until now, drilling for deep geothermal energy has relied on the roller cone bit method (three interlocking bits that cut through bedrock) and the air hammer method. The downside is that both of these is their high cost.

In Aug. 2013, Hanjin D&B, which is based in the Hanam Industrial Complex in Gwangju, became the first company in the world to develop a water hammer technique, using water pressure to drill as deep as 3,502m underground. The water hammer method is not only faster than the standard roller cone bit method, but it is cheaper as well. In 2008, a project in Sweden managed to use water pressure to dig 608m underground, but there had been no further progress until now.

Hanjin D&B is regarded as a small but strong company with outstanding technological expertise, ranking as one of the top four developers of mineral extraction drilling machines worldwide. In 2013, the company succeeded at drilling 3,502m underground using the water hammer technique on a 992m2 lot at the Gwangju Environmental Corporation‘s wastewater treatment plant in Gwangju.

When it was being assessed by the Korea Institute of Industrial Technology (KITECH), the temperature of the geothermal heat was found to be 98 degrees Celsius. It is generally thought that commercial geothermal energy generation is possible when the maximum temperature is around 150 degrees at 5km below the ground.

“This company found a technological solution to the limitations of the water hammer method, which had not been able to transmit water pressure below 2-3km underground,” said Park Jun-sik, chief of Gwangju’s strategic industry department.

David Blackwell, a professor of geophysics at Southern Methodist University in the US and an expert on deep geothermal heat, was present at an international symposium on the topic that was held at the Kim Dae-jung Convention Center after the investment agreement was signed on Wednesday.

“Using Hanjin’s water hammer method, it will be possible to build deep geothermal power generators with a capacity of 50,000MW by 2050,” Professor Blackwell said. “That is enough to replace fifty nuclear power plants around the world.”

But if construction of geothermal energy plants employing the water hammer technology is to become a reality, geothermal energy needs to be added to the certification list of new and renewable sources of energy maintained by the Korea Energy Management Corporation (KEMCO).

“In order to promote the development of solar energy, wind energy, and other kinds of new and renewable energies at the 13 large power plants in South Korea, we are required to purchase new and renewable energy certification,” said Gwangju mayor Kang Woon-tae. “The problem is that geothermal energy is not listed as an eligible energy source.”

Furthermore, while the issue of drilling has been resolved, technology still must be developed for a plant that can convert deep geothermal heat to electricity.

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