OTEC: The Revolutionary Renewable Energy Technology

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sun and ocean


What if there were a technology that provided both renewable energy and water that was safe to drink?

Ocean Thermal Energy Conversion (OTEC) is that technology. OTEC plants provide sustainable, renewable energy using nothing more than the heat found in ocean waters of the tropics. There are no fossil fuels or emissions, and because of the design of the plants, it’s also possible to create potable water during the process.

Clearly, this is world changing technology.

The Need for Clean Water

Reports about the number of people who don’t have regular access to potable water are  alarming. Currently, according to the World Health Organization (WHO), there are 844 million people in the world without access to a basic safe water source. An additional 2 billion routinely use contaminated water, which transmits diseases such cholera, dysentery, and typhoid. In 30 years, the country of Ghana will not have enough water for its citizens.

WHO estimates that contaminated drinking water causes 502,000 deaths each year.

OTEC and the UN’s Sustainable Development Goals

More clean water and renewable energy aren’t just a whim; they are mandatory for the health of both people and the planet. In fact, it’s of such concern that the United Nations has named clean water and sanitation, as well as affordable and clean energy, as two of their 17 Sustainable Development Goals.

That’s why OTEC is vital. While not as well known as solar or wind, OTEC is a way to capture the solar energy stored in the ocean in tropical regions, and convert it to electricity.

boy drinking waterOTEC plants generate renewable energy by “harvesting” the heat in ocean water and using that heat to warm liquids with a low boiling point (such as ammonia) so that steam is produced. The steam is then pressurized so that it can turn a turbine and produce electricity. Cold ocean water  then cools the steam and the closed loop cycle continues.

This is a potentially revolutionary use of the Rankine Cycle, described above, because OTEC allows electricity to be continuously created — without the use of any fossil fuels and with little or no negative environmental impact.

The environmental impact of fossil fuels at both the extraction and the end use stage has been widely documented even as debate rages about the size of the impact.

An added bonus is the ability to use the same structure to desalinate the water that the system is already using — with no negative environmental impact and without the use of fossil fuels.

OTEC Works

The technology was proven, to a great extent, in 1999. The Natural Energy Laboratory of Hawaii Authority, at the time, was the leading site for OTEC research. By the mid-nineties, they had constructed a small, closed cycle, OTEC plant and a much larger open cycle plant. The research the lab did and the data they collected is invaluable. Applying this knowledge to current OTEC plant designs has propelled the technology forward…quickly.

That forward momentum is great news because not only is the need for more sources of renewable energy apparent, but with OTEC, there are significant financial, environmental, and social benefits.

Obviously, this solution works only where there is an ocean, and the ocean has to be warm enough (84 degrees °F is optimal) for the process to work. This means energy from OTEC plants will be generated, primarily, in the tropics.

However, given that 40 percent of the earth’s surface is tropical, OTEC is definitely more than a drop in the solution-bucket when it comes to reliable, renewable, energy.