Use OTEC in any large quantities, such as would be required to replace existing energy generation, and it would likely have a more detrimental impact on the climate & weather systems than anything we have done to date.
Our climate, to a large extent, is determined by the ocean currents, which in turn are dependent on temperatures ........ interfere with that and expect the worst.
For localised use ...... seems to be a clean technology if the necessary safety requirements are adhered to of course.
I'm just curious here: Where do you get that OTEC has detrimental effects? Most all the published papers and articles I have read about it indicated that it acts to bring cool water from the deeps to the surface of the oceans at the equator in the process of producing power. This, in turn, causes algae blooms that can be cultured to provide foodstocks for humans, animals, fish, etc., or can be allowed to sink to the ocean floor as a form of carbon sequestration. (Hey! Cap-and-Trade just got a whole lot more affordable!)
As someone else pointed out, an estimated 3 - 5 Trillion Watts (Terra means a one with twelve zeroes after it) of power could be generated without significant change to the temperatures world wide, and those would start going down
after that, not up. We could eventually strike a balance that maintains the ocean's base temperatures in such a way that Earth's climate is affected positively, not negatively, while enjoying a vast supply of cleanly produced electrical energy.
I think it still beats the pants off anything nuclear, and I used to operate reactors for a living.