Juneau hydro developer has plan for clean, stable heat

  • Juneau District Heating’s system would take electricity from Juneau Hydropower’s Sweetheart Lake facility about 40 miles south of the city to power heat pumps in Gastineau Channel that “scavenge” the thermal energy in the seawater and transfer the heat to water in network of pipes used to deliver the heat to homes and businesses in Downtown Juneau. Images/Courtesy/Juneau Hydropower

Duff Mitchell is doing his damndest to get Alaska’s capital off of fuel oil.

The director of Juneau Hydropower Inc. announced plans for a seawater-sourced district heat system for Downtown Juneau Feb. 9 at the Juneau Economic Development Council’s annual Innovation Summit.

The science behind the renewable energy is nothing new; it’s already being used on a smaller, and cooler, scale to heat the Alaska Sealife Center in Seward and the Ted Stevens Marine Research Institute in Juneau.

Juneau District Heating’s system would take electricity from Juneau Hydropower’s Sweetheart Lake facility about 40 miles south of the city to power heat pumps in Gastineau Channel that “scavenge” the thermal energy in the seawater and transfer the heat to water in network of pipes used to deliver the heat to homes and businesses, Mitchell said in an interview.

It is essentially the same process used in large-scale refrigeration, except the heat is trapped as a valuable resource rather than being collected and dispersed as waste.

The City of Seward is also investigating the potential of sourcing its heat from Resurrection Bay.

At more than 180 degrees Fahrenheit, the district heat loop would run hotter than the systems used at the Sealife Center and Marine Research Institute, according to Mitchell. With two water lines, that hot water can simply be put hooked up to and replace a fuel oil-fired boiler system, which 78 percent of Juneau’s buildings, including Downtown state facilities, use for space heat, he said.

Mitchell estimated the cost to switch from fuel oil heat to the district heat system to be in the hundreds or low thousands of dollars — less than switching to natural gas.

“The conversion cost is low because you’re not ripping out your old system; you’re just supplementing it,” he said.

Adding a new space heat source adds redundancy, meaning a fuel oil boiler could be called back into use if need be just by turning a water bypass valve, Mitchell noted.

Water used in the loop would head back to be reheated at a temperature between about 120 and 140 degrees Fahrenheit.

The system does not sell an energy source; the end product is energy itself.

“We’re selling and monitoring (British thermal units),” he said.

Recent advancements in the compressors have improved the efficiency of the technology to upwards of 300 percent, making the system more feasible on a larger scale, according to Mitchell.

“There’s nothing more efficient than a heat pump,” he said. “In fact, we’ve gone to saying heat pumps are to heating what LED lights are to lighting.”

Juneau’s would be the first ocean-sourced district heat system in the country, but Mitchell said the coastal city of Drammen, Norway, supplies heat to its 65,000 residents through the same system.

Alan Simchick, a regional manager for the heat pump manufacturer Emerson Climate Technologies, said the large-scale pump technology has been on the market for about eight years, a relatively short period in engineering time.

“We really see a bright future for (heat pumps) in a lot of different areas, not just district heating, but also in food processing plants and any areas where heating is needed on an industrial scale,” Simchick said.

He called it “one play” in reducing a community’s overall carbon footprint.

The end cost of heat to consumers will largely depend on how many homes and businesses sign up, he said, but district heat can compete at today’s oil prices and it offers another major benefit — price stability.

The seawater must be at least 37 degrees to maximize efficiency, according to Mitchell, and temperature records show Gastineau Channel has historically met the criteria.

Installing the pipe network can be done through directional drilling, eliminating the need to rip up Juneau’s already cramped streets.

Initial plans are to cover the city’s Downtown, Willoughby District and extend north to include Juneau-Douglas High School, Mitchell said. Expansion to include Douglas and the hospital areas is being analyzed.

The key to Juneau’s system will be the stable cost of electricity born from Sweetheart Lake hydro. About half of the 20 megawatts available will go to power the district heat pumps and the other half will go to the Kensington underground gold mine north of Juneau, he said.

Mitchell is developing both projects in concert with hopes have everything complete in 2018, he said.

Permitting for the projects should be wrapped up by the end of this year.

Combined, the work could inject upwards of $200 million into the region’s economy.

Because inexpensive electricity is paramount for an ocean-sourced district heat system, the technology could be extended to communities in Southeast with excess hydro capacity; however, the economics would likely be challenged in communities with fuel oil, or diesel-fired, electric generation, according to Mitchell.

Elwood Brehmer can be reached at elwood.brehmer@alaskajournal.com.

Updated: 
02/10/2016 - 2:55pm

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