Ocean Thermal Energy Conversion
Sydney inventions streamline ocean-generated electricity
Technosearch is seeking industry partners to develop its innovative process of generating 24 hours a day, nil greenhouse gases electricity by using differences in temperature between layers of sea water.
Hundreds of millions of dollars are being invested internationally to realise the potential of ocean thermal energy conversion, or OTEC.
The principle of OTEC, generating nil greenhouse gases electricity by using differences in temperature between layers of sea water is well proven. Successful small pilot plants have been built and connected by submarine cables to power grids over the past several decades, but they have been plagued with structural and technical difficulties.
Technosearch managing director, Andy Karpisek, believes approaches to date are far too complex and expensive.
“As an example, experiments are being made with huge, one kilometre long pipes of several metres diameter suspended from ships into the depths of the oceans. This is to pump lower temperature water to the surface for essential cooling purposes on shipboard generating plants,” he said.
“We have patented a way of supplying the required cooler water close to the surface, meaning Technosearch has removed the need to suspend long, expensive pipe systems which are exposed to damage or loss to either current action or extreme surface waves.
“Our system also eliminates problems such as barnacle, algal and other build-ups within the system. It also minimises corrosion.
“Our approach also permits OTEC plants to be sited much closer to shore, allowing anchoring of generator platforms to the seabed to reduce the effects of wave damage, and greatly reducing the cost of cable links to power grids.”
Mr Karpisek said Technosearch’s approach would allow the generation of power using OTEC technology, currently limited to more tropical areas where there were greater temperature variations between surface and lower level water, in more coastal areas around the world.
He said the power output of OTEC installations would depend on their size, but a 13 megawatt plant is reportedly being built for the United States Department of Defence, while it is also reported that 100 megawatt-plus plants are now being designed.
OTEC systems are based on using a liquid with a low boiling point of about 20-25 degrees. As it boils it becomes a gas, which drives a turbine, which drives a generator, which produces electricity.
Then the gas must be cooled so that it returns to a liquid state and may be used again. The means of condensation to date have used heat exchange employing cooler water drawn from a kilometre below the surface.
“Our approach is to cool and condense the gas for re-use in a different manner”, Mr Karpisek said.
“It is already slightly cooled as it emerges from the turbine section of the process. Using our inventions it would then be passed through further cooling in a seawater heat exchanger and further compression before emerging again as a liquid.
“It is then ready for re-use in the upper-level generating section of the plant.”
The approach of the Technosearch variant of OTEC removes potential problems raised by environmentalists about adverse effects of drawing nutrient-rich water from the ocean deep and releasing it into surface level marine environments after it has been used in an OTEC plant.
Technosearch’s calculations suggest its approach would use one-twentieth to one-thirtieth of the volumes of water required to cool currently envisaged OTEC plants.
Mr Karpisek said one of the greatest difficulties for alternative, carbon-neutral power generation has been finding a means of generating and delivering power, or base load electricity, whenever it is demanded by consumers.
“The great attraction of OTEC has always been that temperature differentials in the oceans are always there, meaning power can be reliably generated 24 hours a day, every day,” he said.
Technosearch’s developments of OTEC technology are protected worldwide by a series of provisional patents.
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