Renewable Revolution

April 25, 2016

Megan Treacy (@mtreacy) Technology / Clean Technology 

Located in Seward, Alaska about 125 miles south of Anchorage, the Alaska SeaLife Center does important work researching and promoting awareness of the wildlife that resides along the coast of Alaska. The center serves as an aquarium, but also operates as a marine research center and wildlife rescue and rehabilitation center.

The size of the center and its location so far north meant that it has required several electric and oil-fired boilers to heat the buildings. Back in 2011, the center decided to take advantage of a resource right outside its doors and try to cut down on its reliance on fossil fuels and save some money in the process. The center began building a heat pump system that uses energy from the sea water in Resurrection Bay.

The heat pump system was initially effective enough to cover hot water heating and radiant floor heating, but they were still relying on the boilers for baseboard heating. In December, they added a new, much more effective system and the center now meets 98 percent of the its heating needs through renewable energy and has eliminated the use of most of the boilers.

Resurrection Bay is more than 900 feet deep. Through the summer, the water in the bay absorbs solar heat that warms the water through October. The water below the surface remains warmer than the air temperature through winter, which means the bay acts as a sort of heat storage.

sealife center heat pump tech (graphic at link)
© Alaska SeaLife Center

In the new system, seawater is pumped through a heat exchanger, which warms a water and glycol mix. (Seawater is corrosive, and it would freeze, so the glycol antifreeze is needed.) When liquid refrigerant (in this case CO2) comes in contact with the warmish water, it evaporates, which pulls heat out of the water the way melting ice pulls heat out of your drink – changing from a liquid to a gas absorbs energy.

The CO2 then is compressed to 2000 PSI, which raises its temperature to 194°. The hot compressed gas then goes to a condenser, where it turns into a liquid, releasing all the heat that it had stored when it was turned into a vapor.

The old system used a synthetic refrigerant that was not only less effective, but also posed a greenhouse gas risk if they were to leak from the system. The carbon dioxide refrigerant also poses a risk, but to a much lesser degree and the amount of fossil fuel use it's offsetting is significant  . The center estimates that with the new system they are avoiding 1.24 million pounds of carbon emissions.

The SeaLife Center is saving $15,000 a month in heating costs, a savings that can be redirected to its conservation and research programs.

The system will have a complete return on investment in only 13 years.    

The center hopes this shows the potential for this type of heating system throughout the state of Alaska, which has more coastline than the rest of the country put together.

http://www.treehugger.com/clean-technology/alaska-sealife-center-replaces-fossil-fuels-sea-water-power.html