Curacao looks at using ocean water for power

Costumed dancers perform a folk dance for tourists at a restored plantation in Curacao. The island nation in the southern Caribbean is considering using cold seawater drawn up from the ocean's depths to generate electricity. R. Norman Matheny/Staff/File

In less than two years, Curacao may be using its ocean as a power plant. The island nation in the southern Caribbean could use seawater to generate and save power, taking a major step toward innovation in clean energy, projects backers say.

A Dutch company called Bluerise B.V. and the company that owns Curacao's airport – Curacao Airport Holding N.V. – are exploring building a small 100-kilowatt marine power plant that will use the temperature of the seawater as a power source.

In the tropics, the sun heats the ocean surface and keeps it warm all year long. But at a depth of one kilometre (0.6 miles), sunlight can't reach and warm colder waters, circulated from the Arctic.

Ocean Thermal Energy Conversion (OTEC) works by deploying a pipeline in the ocean to pump cold, deep water to the surface and take advantage of the difference in its temperature with the warm surface water.

Cold and warm waters are used in a process to condense and evaporate ammonia, causing it to move inside a closed-pipe circuit. Evaporated ammonia powers a turbine that generates electricity, and then is condensed to continue the cycle.

The downside of the process is that the difference in temperatures is not very large, so the efficiency of the process – and thus the power production – is low when compared to conventional power plants. The bright side is that the energy resource is as abundant as the ocean itself.

"The ocean is an interesting resource to use, as it is always available," says Berend Jan Kleute, Bluerise's chief technology officer. He says OTEC might be used as one of the constant and reliable components of an integrated island energy system. Such a system could also include cheaper – but intermittent – renewable resources such as wind and solar power.

If the process is sufficiently cost effective – a huge question at this point – offshore OTEC plants could eventually provide energy for coastal communities on mainland areas, and any country with access to warm, tropical ocean waters, he said.

The plants could also use their electricity to create fuels such as hydrogen and ammonia, which would later be transported to shore.

According to Jan Kleute, the estimated installation costs of OTEC are around $12 million per installed megawatt – much more expensive than wind and solar. That has limited the technology's appear to potential investors.

Until recently, OTEC development costs were so high that a commercial project was unthinkable, but Bluerise and Curacao's airport may have found a way around this difficulty. The solution is using a fraction of the pumped cold water to run the airport's air-conditioning system.

The project began in 2010 when Curacao airport officials, looking for a way to set themselves apart from competitors in the region, began exploring using OTEC technology.

Becoming "a center of excellence of renewable energy suits our vision," said Simon Kloppenburg, development manager for the airport, which hopes to become a more important gateway into Latin America.

The airport team had looked at other renewables. But OTEC seemed an appropriate fit, Kloppenburg said.

Around 60 percent of the airport's energy consumption goes to air-conditioning, and the power demand is almost constant, Kloppenburg said. Utility costs in Curacao are expensive because energy has to be imported – a problem shared by other islands. The price per kilowatt-hour of imported energy is around 45 cents, Kloppenburg said, which can be 10 times as much as the cost of power in mainland areas of the region.

Bluerise proposed that the airport begin running its air-conditioning systems using cold seawater pumped from deep in the ocean – a change it claims could result in power savings of 90 percent. The airport gave the project the green light, financing preliminary and feasibility studies.

The seawater air-conditioning component is crucial for making the OTEC cost-effective, project officials say. The fuel savings from using seawater to run the airport's air-conditioning system could over time help repay the cost of construction of the deep-sea pipeline, which could then be used for both air conditioning and the OTEC pilot plant.

The aim is to have the pipeline – the most costly component of the system – in place and the OTEC plant working by 2014, project backers said.

If the concept works, Bluerise hopes to then build an additional 1 megawatt OTEC power plant that could provide about 1 percent of the reliable power generation needed on the island of 140,000 people.

Jan Kleute says he can imagine a future with floating offshore 5 to 10 megawatt OTEC plants giving clean and reliable electricity to tropical islands around the world.

The Curacao project potentially could be expanded beyond power and air conditioning. If they can find needed investment, Bluerise and the airport hope to develop an eco-park – an industrial complex for production and research – based on the use of leftover airport cold water.

Potential activities at the eco-park might include desalination, cooling soils to allow planting of different crops, growing fish from temperate waters, or growing algae for biofuels, Bluerise officials said.

A similar scheme is functioning in the National Energy Laboratory of Hawaii Authority, where a demonstration OTEC plant was constructed in the 1970s. In 1989 the laboratory began allowing other research activities to use the cold water. According to the laboratory's website, it today hosts more than 30 companies and generates about $40 million in economic benefits.

The total cost of the Curacao ocean power plant, air-conditioning effort, and eco-park would would be about $30 million; so far $1.2 million has been invested in environmental assessment and engineering studies currently under way, project officials said.