An assessment of ocean thermal energy conversion resources and climate change mitigation potential.

Ocean thermal energy conversion (OTEC) is a renewable energy system that harnesses the thermal gradient between surface and deep waters. Many multi-century simulations with a fully coupled climate-carbon cycle model are presented to explore the amount of extractable energy and the climate change mitigation potential from the widespread implementation of OTEC. The sustainability of OTEC power generation was assessed for present and possible future climate states. A warmer climate reduced the sustainable power potential of OTEC. OTEC could briefly produce over 35 TW of power and, depending on the climate state, maximum power production rates of 5 to 10 TW were found to be sustainable on multi-millennial timescales. Over 500 years of simulation, with a high emission scenario (equivalent to RCP8.5), the power from OTEC deployments, with peak power generation ranging from 3 to 15 TW at the year 2100, resulted in cumulative emission reductions equivalent to 36% to 111% of historical carbon emissions from 1750 to 2023 relative to the scenario without OTEC. Such significant emissions reductions coupled with sustained OTEC-induced mixing led to globally averaged atmosphere temperature decreases of up to 2.5 ºC by the year 2100 and up to 4 ºC by the year 2500 compared to a scenario without OTEC. While caution is required, and the engineering challenges would be large, early indications suggest that the large-scale implementation of OTEC could make a substantial contribution to climate change mitigation.