Bob, Muralidharan cites as his source the U.E.I Administration, Annual Energy Outlook 2009, with Projections to 2030, vol 383 no. April. Energy Information Administration, 2009. This data must be however based on projections since as you point out no OTEC plant of commercial size has ever been built although a Lockheed Martin effort and the DCNs plant Hops refered to below are works in progress. Much of the difference between today and Carter's time is experience gained from deep water drilling and the most productive regions you refer to are relative calm because cyclones do not form near the equator per the following.
As to my optimism it is based on the laws of physics. Trapped heat in tropical waters has to go somewhere. Currently it is going to the poles which will bring about the greatest problem associated with climate change; massive sea level rise. The deep ocean on the other hand is an even greater heat sink which has not been tapped. The same law of thermodynamics that says heat will move from hot to cold also says you can produce work through that movement. It is pretty hard to harness a cyclone as the heat moves to the poles but relatively easy to do this moving heat into the ocean abyss. Further this is an approach to OTEC that has never been tried even though it has the most environmental benefit. Cold water has always been brought to the surface and the amount of water entailed has been OTEC's greatest impediment and the main driver of cost. With the heat pipe you move the heat in about two orders of magnitude less fluid in an enclosed system about one order small than the cold water pipe and this systemt keeps dissolved CO2 in the depths and is not a threat to marine life.
Basicially I think the science is on my side and thus I have every reason to be optimistic because no other energy system will in effect cool the ocean (at least its surface) and this is what has to happen if we are to prevent runaway warming.