Cliff the only place I used kW is in the number it takes to produce 1 kilogram of hydrogen. You are right I should have used kWh and have corrected that.
When you say introductory material, I assume you are taling about terawatts, which are the units Rajagopalan and Nihous use in their article as does Smalley. The data I used is sourced from Energy Information Administration data for 2006 which states the overall average was 15.8TW.
As to the hydrogen economy, most of the automanufacturers are working on it. One of the first turbine engines ran on it. The Russian's proposed its use in one of their bombers. The U.S. Navy set a record for keeping a drone aloft for over 48 hours on it. And Germany has a hydrogen fuel cell powered submarine.
Siemens on their website call it the Most Versatile Fuel and are working on an electrolyzer,
As to OTEC's environmental consequences, I agree with you that the cold water pipe design has many. These would be overcome however by the heat pipe design which moves heat internally in a close system that does not impact marine life. Further the counter-current system limits the amount of heat you have to move thus limiting the impact on the thermohaline and the ocean's overall capacity.
The climate-change benefits I claim elsewhere, including lessening thermal expansion and storm intensity derive from first the conversion of heat to work and second the movement of some of the surface heat to the depths where the coefficient of expansion is half that of the surface.
The Rajagopalan and Nihous paper makes clear that surface cooling would be the result of massive OTEC implementation and since it is this heat that drives storms that in turn move heat towards the poles I think it is a fair assumption to make that OTEC would in fact be beneficial.
It is the lingering technical problems that I and others have been working on the last number of years.
Unfortunately however, as in most cases, it is the status quo, which some of us believe is a technological dead end that is receiving the funding.
OTEC's greatest climate benefit is it is zero emissions energy, is renewable and has the greatest base load capacity.