Taking seawater heat to the next level

By Heidi Zemach for SCN-

Seawater district heating idea suggested by Andy Baker. Heidi Zemach photo.

Seawater district heating proposal suggested by Andy Baker. The yellow lines are for heated sidewalks. Heidi Zemach photo.

Conditions are excellent for Seward to become the first city in America to create its very own seawater heating district. It would have the effect of lowering local dependence on fossil fuels, slashing high energy bills, and growing the economy. With Resurrection Bay glimmering just off Seward’s waterfront, just waiting to provide a free, clean, abundant supply of solar-heated water to homes and downtown businesses, Andy Baker, owner of YourCleanEnergy LLC, in Anchorage, is eager to point out its great potential.

Andy Baker, owner of YourCleanEnergy, addresses the Ports and Harbor Advisory Committee May 21, 2014. Heidi Zemach photo.

Andy Baker, owner of YourCleanEnergy, addresses the Ports and Harbor Advisory Committee May 21, 2014. Heidi Zemach photo.

Baker discussed the concept of a seawater heating district at a Seward Ports and Harbors Advisory Committee (PACAB) work session Wednesday May 21st. He designed the 180-ton seawater pump exchange system that now heats the Alaska Sea Life Center, an imposing 120,000-square foot aquarium building perched on the edge of the bay, at the southern end of town. The system began replacing the center’s oil-fired boilers in December 2012. It saved the center $120,000 in fuel bills 2013, although the electricity needed to run the new equipment increased by about a third. The project also avoided 440,000 pounds of Co2 emissions from being released into the atmosphere.

The basic concept of sea water-generated heat pump system at ASLC is that the raw sea water comes into the system from an intake pipe in the bay at temperatures ranging from 38F to 55F. It is pumped through a heat exchanger containing 90 percent fresh water and 10 percent propylene glycol, a vegetable-based antifreeze in common use in commercial and residential heating systems. Then the water is pumped through an electric powered compressor, where it is further heated to 120F, and finally it goes through looped pipes to heat the facility and its outdoor pavements.

Darryl Schaefermeyer, Alaska SeaLife Center’s facilities director arranged for the project to be created and built for the Alaska SeaLife Center in 2011, with $713 thousand in financing from federal and state energy grants. The center received another $200 thousand from MJ Murdock, to connect the outdoor sidewalk heat, which improved its performance and efficiency. This year, the center received another half a million in state money to install four additional heat pumps with Co2 refrigerant.

Darryl Schafermeyer and Andy Baker discuss how the Alaska Sealife Center's seawater heat pump works. Heidi Zemach photo.

Darryl Schafermeyer and Andy Baker discuss how the Alaska Sealife Center’s seawater heat pump works. Heidi Zemach photo.

Using an energy recovery formula engineers typically apply to heating units to measure their efficiency, ASLC discovered that the pump is now producing a coefficient greater than three, which means that every unit of electricity put into running the pump yields greater than three units of energy in return, making this a cost effective and efficient method, Schaefermeyer said. ASCLC’s heat pumps have reached COP efficiencies at times of 4.0.

The system’s success has answered the question of whether the resource would work in Seward, and provides clues to what fuel savings might be realized. Once a group of local energy experts and members of PACAB had toured the facility last week with Baker and Schaefermeyer,  they were enthusiastically on board, and eager to learn how take its promise to the next level.

In district heating, large seawater heat pumps would supply seawater from an intake pipe in the bay to buildings along a buried insulated loop pipe that would be tapped to serve customers along the route. These customers would use their own commercial heat pump systems to lift the warm source water temperature to up to 140 F for building heat and domestic hot water.

A seawater heat pump district from an intake pipe placed in Resurrection Bay could fuel the residences and businesses throughout the lower portion of downtown Seward, or actually anywhere near the coastline, thus lowering heating fuel bills, promoting conservation, and creating good jobs in the alternative energy industry, and new building and marine construction, Baker said. With more reasonable heating prices, more businesses could afford to stay open year-round. In fact, Seward could become word-famous as the first city in the U.S. with its own seawater heating district, thus spurring increased tourism and bringing in related businesses throughout the winter months.

There’s precedence overseas. The first northern latitude application of sea water heat pumps was in Norway in 1981, followed by additional installations in Norway and in Stockholm, Sweden and Helsinki, Finland. British Columbia now employs several large installations, and in the Vancouver area, they heat a large convention center, Gulf Islands National Park Center, and Whistler Athletes Village.

Why is Seward, or even the Seward Municipal Industrial Center, so uniquely well-positioned to take advantage of this particular alternative energy resource?

Resurrection Bay is a basin of contained seawater more than 900 feet deep. The basin faces south, and is warmed by Alaska Coastal Currents, despite some cooling from glaciers and rivers that drain into it.  It receives a tremendous solar gain throughout the summer, from along the equator, delivered by ocean gyres to Coastal Alaska. The solar heat is stored in layers beneath its surface. Water temperatures and their fluctuations over time would lend themselves well to Seward’s building or sidewalk heating demands, Baker said. For instance by November, when winter cold starts to set in outdoors, the water temperature is at its highest, about 52F degrees. It doesn’t actually reach its lowest temperature ( 37 F) until April, when there’s generally a lower demand for heat.



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What would the system’s infrastructure look like?

A screened seawater intake pipe could be laid directly into the bay from along the waterfront at a depth of about 60 feet. The water would be pumped upwards and into a deep well located near a shore-side facility and then sent through a titanium plate heat exchanger  located on a building near the shore. The heat exchanger  transfers seawater heat to a separate loop of fresh water mixed with Propylene Glycol that condenses and boils it further. That liquid is circulated at 42-52 F through a closed system of underground pipes running into the buildings hooked into the system. Once the heat has been extracted from the seawater, the cooled seawater is immediately returned to Resurrection Bay through an outflow pipe. It never comes in contact with the glycol or fresh water. By lowering the center’s use of fossil fuels, and releasing used sea water into the bay that is a few degrees colder than the water coming into the intake pipe, the project is to a small degree helping to counteract ocean-warming, Schaefermeyer said.

The system also would require a standby heat pump, to be used as needed in order to maintain a minimum water temperature of 40 degrees, and a standby power generator to be used in the case of a city-wide power outage, to keep the water circulating.

To complete the process, building owners would need to purchase or convert their own home heat systems to radiant floor heat, and ideally they would also upgrade their own building’s efficiency.

There are many different types of energy grants and loans available to homeowners and businesses to help accomplish these things, Baker said. Municipalities also have access to energy conservation loans and grants.

But the project doesn’t have to start very out large. A heat pump district could begin small, and then later multiply outward like branches of a tree as people notice how their neighbors are doing, and decide to hook their own buildings into the system, Baker said.

The first step would be for the city to fund a technical and engineering study balancing the practicality and economics of creating such a project, Baker said.

He strongly suggested that the city run the project. But certain property owners or neighborhoods may also want to form their own sea water heat pump assessment district, or cooperative, and finance it themselves.

What more have we learned from the existing seawater heat pump?

One thing the engineers learned from running ASLC’s system is that seawater heat pump systems operate most efficiently when they work to their maximum-demand capacity, thus the more consumers using the system, the better they run. The system would therefore do well when handling high demands such as large commercial buildings, hotels, or government buildings.

When hooking the system up to heat ASLC’s sidewalks, they learned that the job of melting snow and ice is just the right type of demand for the system. They’d recommend that sidewalk heating be included in any district heating project, thus cutting down on city snow-plow activities.

They also tried using heat pumps in a hybrid collaboration with the existing oil boilers but discovered that they don’t work well together as the boilers had to idle for some of the time and then had to start up again, which consumed greater energy. It worked most efficiently when they shut the boilers down altogether, and let the heat pumps do all the work.

The 20 who attended the PACAB work session Wednesday, May 21st, including city officials and the electric department director, harbormaster and city mayor, and several business owners all seemed impressed by the idea, and eager for the city to undertake take the next few steps; a more in-depth economic study, and greater public education and involvement—perhaps even a town hall on the idea. Some suggested a comprehensive energy planning process be started soon for Seward, and that any  planned street and sidewalk improvement projects be postponed a while longer, so as not to have to dig up the streets or sidewalks again to install heat water pipes.

Baker and Schaefermeyer estimated that a seawater pump project could realistically be financed and underway within the next five years, based on their own experience.

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