Ocean Thermal Energy Conversion (OTEC) is an alternative energy source that uses temperature differentials between warm surface water and cooler, deeper waters to generate mechanical energy, which in turn is converted to electricity. OTEC works best in tropical areas where there is at least a 20 degrees Celsius temperature differential, since the energy requirements of OTEC are fairly steep. OTEC was conceived by Jacques Arsene d’Arsonval in France in the latter half of the 19th century.
Although there have been some experimental applications of OTEC, never has a large-scale generating plant been constructed. An O’ahu firm, Ocean Engineering & Energy Systems, is looking to change that. Ocean Engineering and Energy Systems was founded in 1988 as a consulting firm. Over the past two decades the firm has become an advocate for and an innovator in OTEC.
About a year ago OCEES submitted a plan to the Hawaiian Electric Company (HECO) to build a 100 megawatt generating plant three miles off the coast of O’ahu. The electricity would be routed via cable to the island and would eliminate the need to build a traditional fossil fuel or bio-diesel plant at Campbell Industrial Park. OCEES’s power plants (they are in different stages of planning and building several around the world) utilize relatively recent innovations in temperature differential energy conversion to increase the efficiency of OTEC and make it more practical and profitable.
Hans Krock, professor emeritus in Ocean Engineering at the University of Hawai’i-Manoa and president of OCEES, says that he already has financing lined up for the estimated $500 million plant and that construction could begin immediately and be complete within 18-24 months. All that remains is for HECO to agree to buy the electricity from OCEES.
‘HECO has admitted that this is a viable technology, but it is not proven at the scale we are proposing,’ says Krock.
‘There is no basis for saying it’s an unreliable technology,’ he adds. ‘All of the components have been proven and the process is in place and generating electricity on land in places like Iceland, where geothermal differentials are used.’
Krock says that his plant would provide electricity for at least 30 years and that since the ocean is the source of power, the fuel is free. Moreover, according to the OCEES president, the plant would decrease consumers’ electric bills.
‘It would save hundreds of millions of dollars over its lifetime,’ he says. ‘Over the past 15 years HECO has averaged a 4 percent annual increase in price. Our prices would never increase.’
What about environmental impacts? Krock says, ‘We have zippo negative environmental impacts, but we do have benefits.’
There are very few moving parts in an OTEC plant, and nothing more hazardous than ammonia, which is used in countless other industrial operations. According to Krock, there is no danger to birds or whales, and the intake pipe used to suck up cold water could easily be made safe for ocean plants and animals.
‘There is no discharge into the air. It’s low profile [over the surface of the ocean]. Nothing is moving. It is low pressure and generates very little noise. It’s so simple that it could be operated remotely,’ Krock says, adding that Coast Guard regulations would require a human presence at all times.
So why aren’t there any OTEC plants now? Krock explains that until now OTEC has been dismissed as uneconomical. ‘When the last feasibility study was done in Hawai’i, oil was around $9-$12 a barrel and interest rates were 15 percent. Now interest rates are at 4.8 percent and oil is $59 a barrel. There has been a 500 percent fluctuation in the price of oil over the past few years. In terms of future reliability, HECO is on a very thin reed.’
In addition to producing electricity, an OTEC system could create free hydrogen molecules for use in fuel cell engines, helping to overcome one of the greatest obstacles to hydrogen-powered automobiles. Hydrogen could be transported on ships to the mainland. Krock says he already has a deal in the works with General Motors and the state of California to supply hydrogen. In addition, the cold water used in an OTEC system could be utilized in air conditioning and for cold-water aquaculture, including lobster farming.
Krock is obviously thinking big. ‘This is the only resource on earth that is big enough to replace oil,’ he says. ‘It is 10,000 times greater than our energy requirements, and it does it without air pollution. Imagine OTEC power plants scattered throughout the tropical equatorial zones where there is very little wind.’
He adds, ‘This is going to be the biggest thing to come out of O’ahu.’
Ocean Engineering and Energy Systems