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TECHNOLOGY: Ocean Thermal Energy Conversion (OTEC)


The vertical temperature distribution on the open ocean can be simplistically described as consisting of two layers separated by an interface. The upper layer is warmed by the sun and mixed to depths of about 100m by wave motion. The bottom layer consists of colder water formed at high latitudes.

The interface or thermocline is sometimes marked by an abrupt change in temperature but more often the change is gradual. The temperature difference between the upper (warm) and bottom (cold) layers ranges from 10oC to 25oC, with the higher values found in equatorial waters. These two enormous reservoirs provide the heat source and the heat sink required for heat engine. OTEC is a practical application is found in a system (heat engine) designed to transform the thermal energy into electricity.

APPLICATION: Electricity Production

DESCRIPTION:  OTEC energy generation is possible where a temperature difference of at least 20oC exist between deep and surface waters. A volatile fluid is evaporated in a heat exchanger through which warm water passes. The vapours provided by pressure is used to drive a turbine, which generates electricity. The exhaust vapours are condensed back into liquid in a heat exchanger through which cold water passes. OTEC systems convert this thermal energy into electricity, often while producing desalinated water. There are three types of OTEC systems, which are used to generate electricity.
•    Closed-cycle plants circulate a working fluid in a closed systems, heating it with warm seawater, flashing it to vapor, routing the vapor through a turbine, and then condensing it with cold water.
•    Open-cycle plants flash the warm seawater to steam and route the steam through a turbine.
•    Hybrid plants flash the warm seawater to steam and use that steam to vaporize a working fluid in a closed system.

OTEC systems are also envisioned as being land-based (or “inshore”), near-shore (mounted on the ocean shelf), or offshore (floating).

SPECIALIZED EQUIPMENT:

MANUFACTURER (S):

COUNTRIES WHERE TECHNOLOGY IS UTILIZED: USA, Japan

INFORMATION SOURCES

i.    Article(s):
ii.    Publication(s):
iii.    Internet site (s):
?    The Australia Renewable Website (Austria Greenhouse Office)


COSTS

i.    Capital or initial costs:
ii.    Operation and maintenance cost:
iii.    Fuel energy costs:

CAPACITY: <210kW

OUTPUT RANGE:

INPUTS / RAW MATERIALS UTILIZED TO PRODUCE:

ORGANIZATION (S) PROMOTING TECHNOLOGY:



Category/ies:Ocean Thermal Energy Conversion (OTEC).
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