The Sea Water Air Conditioning (SWAC) system permits to save about 42% of energy comparing to a conventional AC system. It uses the temperature of the deep ocean to cool an AC loop, releasing the sea water back to the ocean with no impact.
In tropical environments especially, demand for air conditioning is high all year round. This typically comes at high energy cost, which is in turn typically produced from non-renewable sources. In certain industries and buildings, such as hotels for tourism or hospitals for healthcare, air-conditioning is frequently the largest single usage of energy, representing up to 40% of total consumption. The SWAC solution developed by Pacific Beachcomber aims to drastically reduce the amount of energy consumed to produce air conditioning, while using a renewable natural source of cold.
The solution can be implemented anywhere with suitable bathymetry and easy access to deep ocean water and strong AC needs. The concept of the solution is to give the opportunity to have cool air when needed, while considerably decreasing the energy consumption and our carbon footprint.
This system has been implemented for Pacific Beachcomber properties in French Polynesia in 2 locations: at the InterContinental Bora Bora Resort & Thalasso Spa in 2006 and at The Brando in Tetiaroa in 2014.
The solution works with two main parts:
- A typical chilled-water AC system cold water loop sends chilled fluid throughout the building and to the various fan units which blow air over the chilled fluid pipes to provide cool air into the various spaces. The fluid is propelled through a closed loop using typical electric pumps. These pumps require electricity to function, but a fraction of the electricity required to run a compressor in a typical AC system. The pumps run the fluid through the loop, which includes passing through a heat exchanger. Most of this is typical of a chilled water AC system, however as our solution relies on using sea water for a secondary loop, a non-corrodible material such as titanium is preferable for the heat exchanger. This component provides the interface between the fresh water loop and the salt-water loop from which the cold is absorbed.
- To produce the cold needed to chill the fresh-water loop, rather than use a typical compressor system, the heat-exchanger interfaces with an open sea water loop. A pipe connects from the heat exchanger to a source of naturally cold water, namely the deep ocean. In the case of the Bora Bora SWAC, the pipe is 400 mm diameter and goes down to a depth of 915m. In Tetiaroa the demand for cold is even higher, such that the pipe has a 450 mm diameter, and goes to a depth of 960m, where sea water is stable between 4-5°C. Small suction pumps are necessary to raise the deep-sea water (head losses) up to the surface level heat exchanger, and these pumps will also require electricity. But the pumps are the only use of electrical consumption for the SWAC system. The water is pumped up from a depth of 900m, run through the heat exchangers where the cold sea water chills the water in the close loop, which is then in turn carried throughout the targeted facility.
After passing through the heat exchanger, the seawater typically reaches a temperature of 7°C and is sent back to the ocean at a depth between 30 to 40m. Depending on the size of the application and corresponding length of the fresh water loop, the fresh water loop might start at 7°C and reach up to 12°C.
The coefficient for French Polynesia to convert 1KWh Fuel to CO2 emissions per KWh is 0.891 (in kgs), given the remoteness of the different locations where the solutions are installed, the compensation of cold brought by the SWACs would be done through fuel. In consequence,
- the SWAC on Bora Bora is saving the equivalent of 1,614 Tons of CO2 emissions per year,
- while the SWAC on Tetiaroa is saving the equivalent of 1,980 tons of CO2 emissions annually, it avoids each year 660 000 Liters of gasoil on the island.
The two current hotels (InterContinental Bora Bora Resort & Thalasso Spa and The Brando) using this technology are saving respectively $560,000 and $1,515,000 a year in electricity consumption compared with a no SWAC usage scenario.
In 2021, this solution was awarded the Solar Impulse Efficient Solution Label, a label created to shed light on existing Solutions that are both clean and profitable. The Label is awarded to products, services, and/or processes that combine credible environmental and economic performance, while outperforming the mainstream options in its market.
It was also recognized in the 2021 Tech4Islands Awards organized by the French Tech Polynesia association. Tech4Islands Awards 2021 is the one and only international competition innovation BY and FOR the islands in order to bring out innovative Tech For Good solutions that are ecological, sustainable and resilient, “Good for the islands and therefore good for the planet”.