by hvacman » Thu 19 Mar 2015, 17:31:24
OTEC has several fundamental technical/environmental/economic problems that will probably always keep it as a novelty item, "in the 'some day in the future" category.
1. Hostile environment - it's putting complex moving machinery out in the deep ocean, for crying out loud!
2. Distance from the utility grid. Power that will make a difference has to be transmitted from generator to the main grid. Undersea high voltage/high amperage conductors are $$$$$. Also a big factor with off shore wind.
3. Very low thermal efficiency - Thermal efficiency is proportional to the difference in the ABSOLUTE temperatures of the cold sink and hot sink. Assume the cold ocean bottom is 10 deg. C (283 deg. K) and the top is 25 deg. C (302 deg. K). Ideal thermal efficiency would be 15/283, or 5%. Figure losing 30% of that due to various process inefficiencies. One has to move a HUGE amount of water, with HUGE heat exchangers, to generate a LITTLE power.
4. Potential for environmental impacts large. Think about it. OTEC works by de-stratifying the ocean. All the ocean's life has evolved to live in various thermal layers within the ocean. If OTEC were to be placed in megawatt or gigawatt capacities, you're really going to turn a good chunk of the ocean upside down.
All off-shore energy-production systems, be they wind, wave, OTEC, have may of the same technical challenges as off-shore drilling, with a couple of orders of magnitude less potential extractable energy. Why bother? It is so much more simple/cost effective to use PV, close-shore or on-shore wind, combined with aggressive electric energy efficiency measures.