Honolulu is expected to become the first city in the world to use sea water to cool parts of its region says William M. Mahlum, president of Honolulu Seawater Air Conditioning LLC.
The air conditioning company is managed by Renewable Energy Innovations, a unit of Ever-Green Energy of the US.
The system is expected to make big savings to its clients of about 20% in cooling costs. By making reductions in power by 77 million kilowatt hours a year, or 75%, it will also cut carbon dioxide emissions by approximately 84,000 tons, nitrogen oxides by 169 tons and sulphur oxides by 165 tons a year. It will also make reductions in the use of refrigerants such as HCFC-22, HCFC-123 and CFC-11/500.
How does it work?
A pipe measuring at 1.2 metre wide extends 6.4 km out to sea to a depth of 518 metre, and brings in 166,558 litres a minutes of water at 7 degrees Celsius. Once the water is ashore, the water goes through a conventionally powered chiller equipment that brings its temperature down to exactly 6.66 degrees Celsius through a normal heat exchanger with a closed-circuit freshwater system. It is released back into the sea at a depth of 60.96 metres at 13.3 degrees Celsius, the natural temperature at that depth.
Meanwhile, the cooled freshwater makes its way to the air conditioning units in the buildings, with cooling air passing over the coils in front of the fans, which were previously cooled using very energy hungry compressors.
The project has been in development for just over six years and about 80% of the design is now complete. It will cost US$245 million to implement and will be ready to start operation in October 2012, but the savings expected are more than worth while.
While the seawater air conditioning system is new and innovative, it is not revolutionary: the technology is already being used around the world in locations that have easy access to cold water in places including Toronto, Stockholm, Bora Bora and Hawaii’s Big Island.
“It takes a very special place to do a seawater air conditioning system because you need to have deep water that is very close to shore, you need to have a large air conditioning heat load to make the extra work feasible, and you need to have fairly high electricity rates,” said Dale Jensen. (Senior engineer)
As the world and it’s people demand a more comfortable environment all year round and the cost of energy also is on the increase, new and innovative ways for low cost and effective cooling will surely arise.