The potential to replace conventional air-conditioning with a renewable and less cost-intensive technology based on seawater air-conditioning (SWAC) was demonstrated by an international research team. This cooling approach entails pumping seawater from ocean depths of around 700 m to 1200 m at temperatures of 3° C to 5° C to the coast, where it exchanges heat with a district cooling system and returns the warmer water to the ocean.

The analysis considers design, performance and economic requirements for a SWAC system, including thermal energy storage, a cold seawater inlet, a warm seawater outlet, a seawater pump excavated at a reasonable depth to allow a future increase in flowrate without cavitation, a heat exchanger and refrigeration systems or Diagram of a SWAC system heat exchanger. Source: Julian David Hunt et al.Diagram of a SWAC system heat exchanger. Source: Julian David Hunt et al.district cooling systems. A computational model was applied to estimate the cost of cooling with SWAC in different regions and to assess possible use of the technology as an alternative for energy storage from wind, solar and other variable renewable energy sources.

Just 1 m³ of seawater in a SWAC plant can provide the same cooling energy as that generated by 21 wind turbines or a solar power plant the size of 68 football fields. Higher initial investments incurred by SWAC versus conventional HVAC systems could be offset by lower operational costs. For some coastal areas and islands, cooling costs could fall by 77% of the normal cooling costs associated with conventional air-conditioning.

SWAC district cooling systems can benefit high cooling demand sectors such as airports, data centers, hotels and resorts, and governmental and military facilities.

Researchers from the International Institute for Applied Systems Analysis (Austria), the Federal University of Espírito (Brazil), De Profundis (France), Electric Power Research Center (Brazil), Getulio Vargas Foundation (Brazil), the Federal University of Rio Grande do Sul (Brazil) and São Paulo University (Brazil) contributed to this study, which is published in Energy Efficiency.

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