Written By: Jeremy Feakins
With over a 20-year successful operational record at the Natural Energy Laboratory of Hawaii Authority (NELHA), Seawater Air Conditioning (SWAC) at the Keahole Point facility has demonstrated reliable eco-friendly air conditioning, reducing electricity consumption by 80%-90% compared to conventional air conditioning. Using the deep ocean cold water pipes from the successful 1990s Ocean Thermal Energy Conversion (OTEC) demonstration plant, the NELHA SWAC system exemplifies the advantages of utilizing deep cold seawater to replace energy-intensive central refrigeration methods with dependable, environmentally friendly and cost-saving air conditioning.
The technology and operation of a SWAC system is straightforward. First, water is extracted from the ocean at a depth that provides year-round chill water temperatures, often in the range of 42–46 degrees F (5.5-8 degrees C). The cold ocean water is then used to refrigerate a loop of freshwater, which in turn is distributed throughout the building’s air-conditioning system. Importantly, the chilled freshwater loop never comes into direct contact with the seawater loop, allowing the chilled freshwater to pass safely through the serviced building’s central air systems without harming existing components such as air handling units or coils.
But Why Do We Need a New Type of Air Conditioning?
For large buildings and hotels, particularly in tropical climates, air conditioning (AC) creates the biggest single demand for energy. According to research by the University of Hawaii Economic Research Organization (UHERO), conventional AC being used in Hawaiian hotels makes up an average of 42% of the hotels’ energy consumption. Moreover, companies regularly have expenses associated with replacing leaked coolants and safely containing and recycling them.
AC’s environmental footprint isn’t light either. According to Emerson Climate Technologies, energy consumed from refrigeration, air conditioning and heat pumps is responsible for 10% of global carbon emissions.
In comparison, Seawater Air Conditioning has been proven to deliver huge energy savings (up to 90%), potentially saving hundreds of millions of dollars in electricity costs over the lifespan of large SWAC systems in global regions with high electricity prices.
In addition to the lengthy successful record of the Hawaii SWAC system at NELHA, there are numerous other success stories for SWAC. Among them are Google’s data center in Finland, where the SWAC system uses cold water from the Baltic Sea to cool Google’s critical servers, and the InterContinental Hotel at French Polynesia Bora Bora, efficiently air-conditioned with an SWAC system using cold water from the Pacific Ocean.
Closely related to SWAC is Lake Water Air-Conditioning (LWAC), which is the same essential technology using cold deep lake water instead of seawater. Examples of long-term success with LWAC facilities also abound, such as the LWAC system that provides cooling for downtown Toronto, Canada, using cold water from Lake Ontario. Since the city’s LWAC operations began in 2004, over 30 offices and commercial centers have been air conditioned with 58,000 tons of cooling. After use in air conditioning, the fresh water is recycled and used as drinking water. Similarly, an LWAC system at Cornell University in New York has utilized the deep cold waters of nearby Cayuga Lake since 1999, reducing the campus’ energy demand for cooling by 80%.
Seawater Air Conditioning Reliability and Secondary Applications
With the temperature of deep, cold water changing little on a daily and seasonal basis, cold-water as a renewable resource is dependable all year round. With deep cold seawater being replenished continuously in the SWAC system, its reliability is virtually endless, helping tropical communities become less dependent on volatile fossil fuel prices.
SWAC systems also substantially reduce greenhouse gas emissions. A great example is Ocean Thermal Energy (OTE) Corporation’s 9,800-ton SWAC system now in process under an Energy Services Agreement for a luxury resort in the Bahamas. It has been estimated that this SWAC system will save over 60,000 barrels of oil from being burned annually, while preventing the release of 40,000 tons of carbon dioxide emissions.
Due to the SWAC’s looped system, under certain conditions the water can be reused for secondary applications, including desalination, aquaculture and agriculture. SWAC’s cold deep water is nutrient rich and virtually pathogen-free, providing the optimal environment for various forms of aquaculture including fish farming. Thus, its application to the aquaculture industry is incredibly attractive.
Currently using cold deep seawater for both mature and developing commercial aquaculture applications is the Natural Energy Laboratory of Hawaii Authority (NELHA). Here, micro-algae has been grown for pharmaceuticals and bio-fuels, alongside sustainable farming of numerous seafood products such as shrimp, lobster, oysters, abalone, tilapia, kampachi, flounder and salmon.
Global Applications of Seawater Air Conditioning
With water scarcity an increasing risk worldwide and countries now set on reducing their carbon emissions, vast commercial opportunities for SWAC exist immediately at a global level. SWAC systems can also benefit hot and humid countries where demand for air conditioning is extensive.
A 2009 study analyzed three forms of air conditioning: the SWAC system, the conventional air conditioning system and a hybrid of the two, for cost and effectiveness of cooling a new Egyptian tourist resort called Sahl-Hasheesh. Results from the study found that the SWAC system provided the shortest payback period, as well as the largest energy savings (80% compared to conventional). The SWAC systems also used 75% less energy than on-site chillers, while reducing the resort’s greenhouse gas emissions –an important focus for Egypt after ranking as the 27th largest producer of carbon dioxide emissions in 2006.
Ocean Thermal Energy Corporation: Leading the Global SWAC Market
In addition to the clean, energy-saving air conditioning that is produced by SWAC systems, Ocean Thermal Energy Corporation makes use of available deep water for ancillary industries such as sustainable fish farming and clean drinking water production -a necessity that nearly one billion people are lacking in the world today.
OTE’s subsidiary, selected in 2004 by the U.S Navy Public Works Command at Pearl Harbor to perform a feasibility analysis and design of a SWAC system for the Pearl Harbor and Hickam Air Force Base area, successfully demonstrated the substantial economic and environmental benefits of SWAC systems. Recognition of OTE personnel’s technical expertise by the United States Navy is a clear reflection of our company’s status as a global leader. OTE’s team of ocean scientists and engineers continues to deliver a wealth of expertise and excellence to all our current and future global projects.
Ocean Thermal Energy Corporation’s Atlantic, Pacific, and Indian Ocean-based projects for both SWAC and the related technology OTEC (Ocean Thermal Energy Conversion) signal the start of OTE’s globalization of its competitively priced, renewable-energy resources. Over 100 countries have been identified as suitable candidates to host OTEC and/or SWAC plants. With these OTEC and SWAC plants estimated to generate contractual revenues between US$400 million and US$800 million for OTE Corporation, the time has come for commercially attractive investments that can reap enormous global humanitarian benefits.
Among OTE’s current SWAC projects are agreements to build, own and operate a 9,800-ton SWAC plant for a world-class luxury resort in the Bahamas – which will become the world’s largest deep-ocean SWAC facility, and a SWAC plant in the Cayman Islands for the new Health City.
Globally commercializing SWAC and OTEC will provide hundreds of communities with the self-empowerment tools to shape a sustainable future and develop true long-term energy independence. It also provides enormous investment opportunities for business, satisfying the demands of the world’s core markets.