Thursday, 15 March 2012


Back in university, I looked into a process called Ocean Thermal Energy Conversion, or OTEC. This process, in my opinion, is pretty incredible and not only does it provide renewable energy, but one of its by-products is fresh water. It has an initial expensive insertion cost, but apart from that is relatively cheap to run and is pretty much guaranteed. I strongly believe it should be further researched and taken seriously as a renewable energy source.

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:


- 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


- 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!

Water, water everywhere, but not a drop to drink..

So this week we have been told that, despite it only being March, we are facing a water ban. Currently set at a hosepipe ban, however some "experts" are predicting we may face furthers restrictions.

We are being told that this is due to rain shortage and the fact that water companies don't know how use the snow which fell only very recently. The papers also printed pictures of rivers across the U.K which have run dry. Some people reacted with outrage; how much water is being used for the Olympic stadiums? What are water companies doing to prevent the leakages they encounter from which masses amounts of water seeps? How come countries across the world, mainly Europe, don't suffer from the same situation?

Well, I can't answer the first 2 questions, but with regards to the latter, it seems that countries all over the world are encountering low water resources. The EEA (European Environmental Agency) has admitted that pressure is mounting and it has called for further legislation on water usage to prevent further wastage.

Many are blaming dry seasons for our water shortage, but personally, I don't think this is the main cause. Our population is dramatically increasing and this will automatically lead to a greater water usage. And it's good to remember; it's not just our water which will be lost, but our fish stocks will suffer too - less water will ultimately mean less fish. Something which we are already struggling with.

So how does a government tackle this problem? What suffers through lack of water? If harsher restrictions are placed upon water usage, there are bound to be businesses that will suffer, should a country already in huge financial trouble be entertaining this idea? Are we REALLY using everything to our advantage? The technology we have available could lead to some relief on our resources, so why are some of these technologies still being ignored? Why hasn't reverse osmosis been pushed further? And there is Ocean Thermal Energy conversion (OTEC) which is, in my eyes, an incredible invention. It could lead to a reliable source of renewable energy AND fresh water as a by-product.

So why are we still ignoring it?