With a population of over 600 million people, tropical island nations are in a difficult position when it comes to electricity. Stuck with outdated generation powered by fossil fuels, these countries are subjected to high import costs, delays and interruptions, which results in an insecure energy system. And considering that tropical islands are among the most vulnerable to climate change, particularly to severe weather such as storms, hurricanes and natural phenomena like El Niño, the transition to renewable, cheaper and more reliable sources of power is more than urgent.
Extracting clean energy from the ocean, which is their largest natural resource, is a great pathway for the islands’ renewable transition. The 60 million square kilometres that comprise the tropical area of the ocean present a significant temperature difference between surface and sub-surface layers. And when warm surface seawater and cold deep water reach a contrast of at least 20°C, Ocean Thermal Energy Conversion (OTEC) becomes suitable. Just to have an idea of the potential that OTEC has, in one single day the tropical area of the ocean absorbs one quadrillion megajoules of solar energy, that is not being harnessed. To release the same amount of energy through fossil fuels, 170 billion barrels of oil would need to be burned, a high economic cost and even bigger for our environment.
OTEC can decrease energy charges and stabilise the price of electricity, reducing the frequency of blackouts and preventing economic shocks from political events while helping islands meet the UN’s Sustainable Development Goals (SDGs). OTEC can also provide baseload power, which is the minimum amount of electricity that a power grid must have at all times. This is extremely important for tropical islands, which often have a high demand for electricity during the day. And all of this with zero CO2 emissions.
While other clean energy sources require the use of the scarce land of islands and depend on adequate weather to operate, OTEC is based offshore and can generate electricity 24/7, as the surface seawater remains warm day and night, all year round. Also, every 1 MW of OTEC installed generates the equivalent of 5 MW of solar power or 10 MW of wind power.
With projects around the world that have proven the concept, OTEC is now advancing to the commercial scale. The UK-based company Global OTEC has developed the First-Of-A-Kind 1.5MW OTEC platform, already set to be installed on the African island of São Tomé and Príncipe, in the Gulf of Guinea, by 2025. Named Dominique, the structure has been awarded recently an Approval in Principle (AiP) by Lloyds Register, and acknowledgement that the platform can meet the necessary requirements for providing a structural basis for the OTEC technology.
Earlier this year, the company also achieved its first Certificate of Approval, from the Marine Warranty Surveyor company ABL Group for the methodology of installation of a Cold-Water Riser. This approval was particularly important given the technical challenges faced by OTEC installations in the past, and the long history of OTEC’s unsuccessful implementations, meaning the Global OTEC’s technology can overcome these challenges.
Dominique is the starting point for a renewable transition that will allow tropical islands to access clean, cheaper and more reliable electricity. There are over 100 territories around the world with access to ocean waters where the technology can work. “Our first of a kind is a significant step towards unlocking the 8,000 GW of OTEC technical resource which has been identified”, highlights Dan Grech, Founder and CEO at Global OTEC.
How does OTEC work?
- The barge draws in warm surface seawater (of around 26°C) which has been heated by the sun’s rays
- This warm water is used to evaporate a working fluid with a low boiling point
- This produces a vapour which spins a turbine to produce electricity using a generator
- At the same time, cold deep water (of around 4°C) is drawn up through a pipe from the depths of the ocean
- The cold water cools the vapour, turning it back into a liquid which can then be immediately reused
- The cycle runs continuously whilst the power generated is transmitted to the grid using a sub-sea cable.