• Ocean thermal energy conversion (OTEC) uses the temperature difference between cool deep ocean water and warm tropical surface water to produce clean electricity on the oceans.  7 TW is an environmentally sustainable level.  Using electrolysis plus the Haber-Bosch process to generate ammonia as the safe liquid-fuel hydrogen energy carrier, it can provide 2.6 TW of dispatchable, storable, CO2-free electric power wherever needed on land. 

  • Recent climate modeling studies have shown that the upwelled cold water from this same level of OTEC, if discharged and retained at the surface, will also set off natural climate forces that will directly decrease the Earth’s Surface Atmospheric Temperature (SAT) by 1.08°C.  This is equivalent to taking 2,261 Gt of CO2 out of the atmosphere.

  • Together with the associated fossil-fuel replacement, OTEC used in this way can mitigate global warming by 1.70°C by itself.  If a modest amount of wind, wave, and solar power is added, global warming could be held to 1.5°C at fossil-fuel replacement levels close to the INDC commitments of the 2015 Paris climate talks (see graphical summary 1 below, point labelled "wOws 1.5C"). 

  • If the world is willing to eliminate 100% of CO2 emissions and include a maximum usage of OTEC, global warming could be held to 0.4C ("wOws 0.4C") and sea level rise could be held to 0.45m at year 2100 (0.75m less than the business-as-usual value) (see graphical summaries 1 and 2 below). 

  • Possible environmental effects have been examined, and there are no show-stoppers. 

  • The reduction in SAT allows negative carbon fees to be awarded by governments, which, based on financial modeling to date, could enable substantial reductions in required capital investment and could lower the levelized cost of energy (LCOE) to well below 100% wind, wave, and solar solutions (with their required storage and interconnects). 

  • The overall concept rests on known technical ingredients and experience, including small operational floating and land-based OTEC plants and many designs and cost estimates for large OTEC facilities.  

  • The method for retaining the upwelled cold water at the surface needs further development, the effect of this on the climate response needs further study, and the concept depends also on leveraging future advances in the various methods for utilizing ammonia for clean energy

  • Being rich in nutrients, the upwelled cold water can also increase primary production for Marine Permaculture concepts, with the OTEC platforms providing required infrastructure.

  • The cooler ocean surface would also assist the preservation of coral reefs.

  • With further development, this approach could provide the basis for CO2-free liquid fuel adjacent businesses, for example within large oil companies whose experience and assets on floating ocean platforms, chemical processing, and fuels transport by tanker and pipeline would be relevant, and whose future revenues from fossil fuels may be at risk as the world moves towards mitigating global warming.

Executive summary

© 2017 by Cool it, Earth! (LLC)