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US aquarium cuts fossil fuel for sea heat

Associated Press Associated Press 23/04/2016 Dan Joling

Thousands of people visit the Alaska SeaLife Center in Seward for a look at Steller sea lions or harlequin ducks.

What's in the basement is almost as interesting.

The centre, which combines aquariums with research and wildlife rescue, says 98 per cent of its heating and cooling requirements are no longer filled by fossil fuel.

The centre is using alternative energy: heat extracted from ocean water in Resurrection Bay.

The heat exchange system is saving money and fulfilling the centre's mission of sharing scientific knowledge to promote stewardship of Alaska's marine resources, said special projects co-ordinator Darryl Schaefermeyer.

It demonstrates that seawater is a potential heating source for Alaska, which has more coastline than the rest of the nation put together.

"Simple payback is estimated to be 13 years at the estimated annual savings on electricity of $48,000," he said.

"Since starting the system, we have averaged just over $US4000 ($A5170) savings on electrical energy cost per month."

It's used with a seawater system the centre installed in 2012.

The new system was designed by Andy Baker of YourCleanEnergy, an Anchorage consulting firm.

It uses equipment manufactured by a Japanese firm, Mayekawa, and relies on a complex system of pipes to heat some parts of the building and cool others.

"The trick is to getting all those loops to transfer heat at the correct rate," Baker said.

Resurrection Bay absorbs solar heat over summer months.

The water warms through late October and, below the surface, retains enormous amounts of heat throughout winter.

Heat exchangers are devices that transfer heat from one loop of liquid to another without mixing the liquids.

The centre's new system draws seawater and pumps it into a heat exchanger with non-corrosive titanium plates, where it heats a loop of water and 10 per cent glycol, an antifreeze.

The warmed water and glycol loop is passed alongside a loop of liquid carbon dioxide, causing the liquid CO2 to boil into a vapour.

A compressor squeezes the vapour, which raises its temperature.

The heated CO2 vapour is exposed to yet another loop: the water that circulates through the SeaLife Center's building.

The system has been operating since January 21.

On Seward's coldest nights, about two per cent of the time, the centre had to turn on an electrical boiler for more heat.

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