Ocean Thermal Energy Conversion (OTEC) uses the temperature difference between the ocean surface layer and lower layer. It is like a gigantic heat pump.

Ocean Heat Exchange

Source: TU Delft

In Monaco a big part of their cooling and heating is done with over eighty (80) ocean heat exchangers. Since 1963 Monaco has been using the Mediterranean Sea as a source of energy. It has been the first nation to do so.  Today Monaco produces about 20% of its national energy needs this way. The advantages of this energy are obvious – heat pumps produce three to four times more energy than they consume, which helps efforts to reduce greenhouse gases.  This could be done in NZ and the Pacific Island nations as well. 

Near the equator or where you have sufficient temperature gradient between the surface and lower ocean layer OTEC makes sense. Leaders in OTEC are Japan, India. There are some installations on Island nations. 

Orange suitable for OTEC

Source: Bluerise BV, now AllSeas

For more information on OTEC check out