This report provides a summary of an investigation by the University of Hawai‘i Sea Grant College Program into the viability and effectiveness of installing a seawater air conditioning district cooling system in Waikīkī. Seawater air conditioning (SWAC) harnesses the cooling properties of cold seawater to provide cool air for air conditioning purposes. In doing so, SWAC reduces the amount of electricity needed for air conditioning. SWAC is particularly relevant to Hawai‘i for two reasons: first, the proximity of deep, cold, ocean water to areas of high population make Hawai‘i an obvious location for implementing the technology; and secondly, with approximately 90% of its electricity generated from fossil fuels, Hawai‘i is the most fossil fuel dependent state in the nation. Unlike the rest of the U.S., where coal, natural gas, and nuclear power are called upon to meet a substantial proportion of the electricity demand, Hawai‘i relies heavily on residual fuel oil (the by-product of refining crude oil for jet fuel, gasoline, and other distillates). As a result, Hawai‘i has very high electricity prices compared to the rest of the country. SWAC has the potential to both cut the cost of air conditioning and reduce the amount of harmful emissions that are released as a by-product of generating electricity from fossil fuels.
Seawater air conditioning works by pumping cold (44-45°F), deep (1,600-1,800 feet) seawater into a cooling station (Figure 1). Here, the cold seawater is used to chill fresh water flowing in nearby pipes. The chilled fresh water is then piped into hotels for cooling purposes while the seawater (slightly warmed to 53-58°F) is pumped back into the ocean at a shallower depth (120-150 feet).