Storm-proof renewable energy for tropical coastal regions.
By Hanna Perks
In tropical regions, the surface of the ocean is warmed by the sun year-round, while colder water lies deep below. This difference in temperature , called a thermal gradient, can be used as a source of renewable energy. Ocean thermal energy conversion (OTEC) involves harnessing this natural gradient to provide clean, renewable power year-round.
OTEC only works in regions where there’s enough of a temperature difference between warm surface water and cold deep water – usually a gradient of at least 25°C. That’s why OTEC is particularly suited to the tropics, where this condition is met year-round.
The system draws in warm seawater from the ocean surface, typically around 26°C, and uses it to heat a special fluid or “medium” that evaporates at a low temperature. This vapour turns a turbine connected to a generator, producing electricity. At the same time, cold seawater from deep below the surface, about 4°C, is pumped up to cool the vapour, turning it back into a liquid so it can be reused. This closed-loop process runs continuously, allowing for uninterrupted power generation. The electricity is then transmitted to land through cables, much like off-shore wind energy.
So, why isn’t this technology widespread in these regions? One reason is getting worse with climate change… tropical storms. Massive swells and high wind speeds can severely damage OTEC energy units deployed at sea. As a result, OTEC technology has struggled to take off. Another factor is high costs.
UK-based company Global OTEC wants to change that. Their mission is to use OTEC as a new category of renewable energy that can deliver affordable, reliable, and renewable electricity to tropical regions. To achieve this, Global OTEC has developed several systems and prototypes – but one in particular, known as the PLOTEC, could be a game-changer. What’s unique about the PLOTEC is its strength and durability - it has been built to be strong enough to endure even the most violent tropical storms.
OTEC has the potential to deliver a large impact in tropical regions. Unlike solar or wind energy, which are intermittent and weather dependent, OTEC provides baseload power – constant electricity 24 hours a day, 365 days a year. By using the ocean’s natural thermal gradient, OTEC could help to reduce reliance on fossil fuels, cutting greenhouse gas emissions and improving energy security for vulnerable nations, especially small island developing states (SIDS).
Fossil fuels are making storms worse… and those storms are making renewable energy harder to install. But PLOTEC shows that there might just be a way forward for small island developing states. If there is anything to be learned from Global OTEC, it’s that we need to build and invest in renewable technologies that are not only efficient and effective, but also durable and resilient – able to stand up to the worsening impacts of climate change they are designed to help prevent.