Power of the sea

Scaled OTEC structure design (Screenshot Video by Global OTEC)

A technology now being tested that harnesses seawater to produce electricity could address some of the Pacific Islands’ problems with power outages.

Under the Project for Ocean Thermal Energy Conversion (OTEC), a Pan-European consortium of seven companies is working to build a structure capable of withstanding the severe weather effects of the tropical area of the ocean.

Global OTEC Founder and CEO, Dan Grech, said: “Combining the developments of PLOTEC [the name given to the consortium] with the OTEC power demonstration facilities around the world, this ocean energy technology is a great fit for tropical islands, as other renewables have a more sensitive structure to severe weather or depend on sunny and windy days to generate electricity.

“As the surface seawater in the tropical area of the ocean remains warm throughout the year, OTEC can generate electricity 24/7. By adding it to a storm-resistant structure, the technology becomes the potential permanent solution to power outages in the Pacific, while also being renewable and with zero CO2 emissions,” he said.

“The PLOTEC structure will be a cost-effective floating platform that can hold out in the 100-year storm. This will be tested via computational simulations, using data from tropical storms, learning from the most severe weather conditions in the North Sea, and built with similar resistant materials.

“The design allows disconnection in the case of severe weather so that the structure can be taken to a safe harbour during the most severe storms and reconnected straight after; this is crucial, particularly when electricity is needed during storm recovery.”

The European Union-funded project cost €3.5 million to develop. It uses materials such as steel for the hull, which has the high density and durability usually used in offshore applications and is likely to last more than 25 years, as well as marine-grade plastics. So how does this technology work?

Grech explains: “In order to operate, an OTEC system requires warm surface seawater, found during the whole year in the tropical area of the ocean, and cold deep water, found in depths of 1000 metres. It doesn’t depend on seasons, windy days, or even good-weather days, as the temperature in this area doesn’t change much.”

He adds, “This all makes OTEC much more reliable as it can produce power 24/7, 365 days a year, without severe interruptions. Also different from wind or solar, OTEC doesn’t require the use of land as it is based offshore, which helps preserve the natural beauty and ecosystems of tropical islands.”

Currently, the team is working towards determining the maximum hurricane force conditions that the structure can withstand, and so far they have conducted computer simulations and a physical scaled test in a tank in London as a trial.

“The next milestone is the installation of a larger scaled structure off the coast of Northwest Africa. Once finished, this design can be implemented in over 100 territories around the world across the tropics where there is a need for a storm-resistant structure to allow energy production with minimum interruption,” Grech said.

According to Grech, back in the 1980s, a land-based OTEC plant was demonstrated in Nauru, but it was destroyed by a tropical storm.

He said, “This highlights the importance of the PLOTEC team’s mission to develop a suitable structure. All Pacific islands located within the tropics and with access to deep waters (around 1000 metres) can use OTEC for power generation.

“At Global OTEC, we designed the first-of-a-kind OTEC commercial platform set to be installed on the African island of Sao Tome and Principe. This project can be easily adapted to the needs of the Pacific Islands, including the ones that are more vulnerable to storms and hurricanes.”

The team has identified 100 countries where OTEC can be used for power generation, and countries can contact them directly. The technology is set to be installed in 2025 in both Sao Tomé and Principe.