Ocean
Thermal Energy Converter overview
Ocean Thermal Energy Converters (OTECs) use the temperature difference between
cold deep lying ocean water and tropical warm surface water to produce energy
with little impact on the surrounding environment. The distinctive feature
of OTEC energy systems is that the end products include not only energy
in the form of electricity, but several other synergistic products.
The
first bi-product is nutrient rich cold water from the deep ocean. The cold
"waste" water from the OTEC is utilised in two ways. Primarily
the cold water is discharged into large contained ponds where multi-species
mariculture is performed, producing harvest yields which far surpass naturally
occurring cold water upwelling zones, just like agriculture on land. The
cold water is also available as chilled water for either air conditioning
systems or more importantly for refrigeration systems, most likely linked
with creating cold storage facilities for preserving seafood. When the cold
water has been used it is released to the deep ocean.
The
second bi-product is fresh water. A small 1 MW OTEC is capable of producing
some 4,500 cubic meters of fresh water per day, enough to supply a population
of 20,000 with fresh water. OTEC-produced fresh water compares very favourably
with standard desalination plants, in terms of both quality and production
costs.
This
sounds too good to be true, doesn't it? A non-polluting, infinitely renewable
energy production system which has organically grown food and fresh water
as bi-products. Fortunately it is not to good to be true. At the Natural Energy Laboratory of Hawaii
(NELHA) there are two different types of OTECs in operation one of which
has been in use since 1993.