# Does water need to pumped up from deep ocean?

OTEC (Ocean Thermal Energy Conversion) utilizes the temperature gradient between cold deep ocean water, and warmer water to do work. I understand the pressure in the depths may be as high as a couple of orders greater than surface atmospheric pressure.

I also remember, vaguely, that a fluid moves from an area of high pressure to low pressure; wouldn't a sealed pipe merely need valves at the top to control the flow? Does water need to be pumped up out of the deeps?

More context: OTEC is estimated to be viable with a ${\Delta}T$ of 20 Kelvin, so definitely the tropics, and predominantly the western Pacific. Unsurprisingly, Japan has been particularly active in OTEC. The global harnessable resource is estimated at $10^{13}W$, which is the same order of magnitude as total global energy consumption.