So what is OTEC?
As I have already mentioned, OTEC means 'Ocean Thermal Energy Conversion'. Is laments terms, this is a process which uses the thermocline to produce energy. In the sea, the water column has varying temperatures. The bottom of the water column will be cooler than the water at the top. OTEC uses this variation in temperature to produce electricity.
The idea of OTEC is by no means a recent one. It was first proposed in the 1880s by a French physicist, D'Arsonval. However it was a student of his, Georges Claude, whom built the first OTEC plant in Cuba, which produced around 20kW of electricity. Today, there are various governments around the world who are heavily researching and testing the technology, with Hawaii leading the way.
Okay, so how does it work?
Well, I am not going to get too complicated. I know that most people who read my blog aren't scientists and nor am I, so I will keep it pretty simple!
There are two types of OTEC systems; open cycle and closed cycle. Closed cycle OTEC uses a rotating turbine, powered by a type of fluid (i.e, ammonia, as it has a low boiling point). This fluid will be vaporized by warm seawater being pumped through a heat exchanger. At the same time, another heat exchanger will have cold water flowed through it, which will condense the vapour into liquid. This will all be recycled. Still with me? The diagram below may help! (Borrowed from the NREL website, many thanks to them)
Open Cycle OTEC works a little differently. This cycle works without a fluid and uses warm surface water. This is poured into a low pressure container, which causes it to boil, causing the steam to have the ability to power a turbine which can is linked up to a generator. This is an excellent way or doing it, because the salt will have been left behind in the container, along with any other water contaminants, which means is produces a by-product of clean water. Clean water, which is suitable for drinking. Imagine all those who could benefit from this?
Both of these cycles can be combined, to form a sort of hybrid. This uses ammonia, but will also produce fresh water.
Another good point about an OTEC system is that it can be built at various locations; land based, shelf based and floating versions have all been built. a floating plant is currently running off the coast of India.
So far so good, right?
Alright, what are the cons of Ocean Thermal Energy Conversion?
Well, I'll do a table of both pros and cons, because I haven't actually mentioned all the pros so far:
PROS
- It's completely clean. OTEC does not pollute air, land or sea.
- It's reliable. Unlike wind energy, it is always there.
- A by-product is fresh water
- A plant can double up as a good artificial reef
- It can provide air conditioning!
- As mentioned, it can be built at various sites
CONS
- It can be costly. This is its biggest problem. Construction can be pricey so can transporting the electricity and the clean water.
- It still needs research. Again, this costs money.
- Not many people know about it
So far, those are the only cons I have come across. This is why the fact that we are not using seems so insane to me. We need our governments to push further with this. Our current energy resources are finite. And with a world getting busier every day, we need to search further afield to keep ourselves afloat. We need more research into OTEC and to discover economical ways of getting the energy transported out. We can't let this just slip by!
