Cold deep-sea water, pumped to the surface, could provide innovative clean power and cheaper air conditioning, project backers say
In less than two years, Curacao may be using its ocean as a power plant. The island 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 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, 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.
HIGH COST
If the process is sufficiently cost effective – a huge question at this point - offshore OTEC plants could eventually provide energy for coastal communities located 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.
"In a report on renewable energy sources released this year, the Intergovernmental Panel on Climate Change said that the estimated installation costs of OTEC could range from $4.2 to $12.3 million per installed megawatt - potentially much more expensive than wind and solar. That has limited the technology’s appeal 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 ago when Curacao airport officials, looking for a way to set themselves apart from competitors in the region, began exploring using OTEC technology.
Becoming “a centre of excellence of renewable energy suits our vision,” said Simon Kloppenburg, development manager for the airport, which hopes to become a more important gateway in Latin America.
The airport team had looked at other renewables. But OTEC seemed an appropriate fit, Kloppenburg said.
AIR CONDITIONING FROM THE OCEAN
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 one megawatt OTEC power plant that could provide about one 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 five to 10 megawatt OTEC plants giving clean and reliable electricity to tropical islands around the world.
OTHER USES FOR COLD SEAWATER
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.
Santiago Ortega Arango is a Colombian engineer and freelance journalist interested in climate change and renewable power issues. He is an associate professor at the Escuela de Ingeniería de Antioquia and a Fellow in Global Journalism at the Munk School of Global Affairs at the University of Toronto.
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