Ocean Based Renewable Energy

When most people think of renewable energy, they see solar panels and wind turbines. Given the country I am located in (Portugal), those certainly are a common sight. Honestly, you can’t drive down a road in this place without seeing either a bunch of solar panels or wind turbines, and quite often both. But this post is not about solar panels, or wind turbines floating on the sea. It’s about more than that. 

Jumping up a level from solar & wind, in the ocean environment, we find wave & tidal energy systems, both of which promise huge potential in energy returns. However both have significant downsides. For example, both require careful location. With wave energy, the waves can’t be too big, and the season matters. Tidal energy needs a very large volume flow to ensure the tidal range does not cause the unit to hit the bottom when the tide goes out. In other words, neither are constant, and only provide a variable output.

There is one other option available.

OTEC, or Ocean Thermal Energy Conversion. The ocean is a giant thermodynamic energy system with potential energy reserves far exceeding all other renewable resources currently available. Some estimates are suggesting up to 88 000 TWh/yr, which is more than the total energy output of the entire planet to date. For comparison, wind energy is estimated to have a potential to produce up to 36 000 TWh/yr, although these figures will most likely change as better data becomes available.

So what is OTEC? Simply put, it’s the temperature difference between the warmer surface water and the colder deep water. With a little bit of creative yet simple engineering, we can produce energy from the temperature differential.

Warm surface water is brought in to evaporate a low boiling point working fluid, usually ammonia, which evaporates. This turns into steam, which powers a turbine. The working fluid is then condensed back to a liquid with the cold deep water. The beauty of this system is it can run 24 hours a day, 7 days a week.

Some of the other benefits seen with OTEC are:

  • It is carbon neutral (negative if combined with CO2 removal);
  • No fuels are required, thus zero emissions and particulates; and
  • The discharged water is virtually identical to the ambient water.

Two working units are currently in operation: One on the island of Kumejima, Okinawa, Japan; and another in Kailua-Kona, Hawaii, USA. Both of these units are fairly small, proof-of-concept demonstration installations. Both output around 100kW of electricity. Both are also open to visitors!

OTEC is unique in the way it can be combined with other technologies to perform other functions, such as desalination of seawater, carbon capture, air conditioning, aquaculture, and even mineral extraction from seawater. These technologies combined with OTEC can help to reduce the initial high capital expenditure required for OTEC, by offsetting those costs with another revenue stream. This segues nicely into why OTEC is not being further utilised… yet.

The main roadblock to development is initial high capital cost and low profit with OTEC units smaller than 10MW output. As stated earlier, this can be offset by combining OTEC with one or more other technologies, to provide secondary revenue streams. While these combined technologies won’t necessarily drop the initial high capital cost, it will increase the profit streams for output products.

Next, is the lack of incentive to overcome the “Innovation Valley of Death”. This is another catch-22 situation: No one wants to pay for OTEC until after the development has been done, but OTEC cannot progress until investment in its development is suitably funded.

Finally, a lack of knowledge & understanding of OTEC in both the general populace, as well as government makes it difficult to sell to people. Simply put, policymakers don’t even know OTEC exists, so as a result, they cannot make policy to push for its development.

OTEC has huge potential to completely revolutionise how the world generates electricity. It can take us to a new level, one that no other method of power generation can match. There is no harmful waste, no emissions, no fossil fuels. Just clean energy. Combined with other technologies, it can even help to remove carbon from the environment, provide clean potable water to millions of people, and provide the rare earth minerals needed for electric vehicles (the ocean has an almost unlimited amount of lithium, just to name one of them!)

OTEC might even change the way we live. Unfortunately, until there is capital investment, OTEC is destined to be another unrealised technology no one even knows about. We need to make sure this does not happen by promoting OTEC as the technology that CAN change the way we live. With targeted promotion of OTEC, policymakers and investors can see its benefits, and not just as a means of producing clean renewable energy, but also clean drinking water, carbon removal, ocean mineral mining – the possibilities are as endless as the ocean itself.

Come join us at KCR and make this future of clean, sustainable energy abundance a reality.