District Energy: Pike Place Market

October 16, 2013

By Duncan Thieme

Pike Place Market is the oldest farmers market in the country and the most popular destination in Seattle. More than a marketplace, Pike Place is a dense and varied urban neighborhood, home to many office tenants, social service agencies and hundreds of residential tenants at all income levels. SRG's recently completed renovation included a comprehensive district energy system that exchanges energy between the heating, cooling and refrigeration loads through the bulk of this historic campus.

Prior to renovation, the Market's tenants managed their own heating, cooling and refrigeration systems with mixed success. It was common for some parts of the campus to be spending energy making heat while other parts were using energy to create cooling. In the new system, all of the energy is shared, and the central plant only supplies heating or cooling based on the aggregate demand of the whole campus. A central mechanical system exchanges energy through the campus condenser water loop that is heated or cooled as needed.

The central system circulates a loop of condenser water through the campus, which is then hooked to a series of heat pump systems. These heat pumps can either add heat to the loop or take it away, creating cooling or heating as needed in various spaces throughout the campus. The main loop itself is controlled within a temperature range that's near a typical room temperature, which is nice because the loop does not need to be insulated when it's indoors. If it needs to be heated or cooled, central fluid coolers and boilers located at the garage do the job. The heat drawn off the large refrigerators and freezers for the various markets and restaurants is enough to heat the interior spaces of the buildings through all but the coldest days of winter. This is already proving to be very efficient.

In two locations, where the concentration of small retail tenants is the greatest, we placed banks of water-to-water heat pumps connected to the condenser loop. They use the same basic system to transfer energy, but use smaller loops of hot and chilled water, which are then distributed around the buildings. They are hooked up to small fan coil systems that are used to heat and cool small retail tenants. Some of the tenants are hooked into the system, but others are not. For the latter case, we've left easy points of connection for future hookups, should there be a need to extend or adapt the system.

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Duncan Thieme

AIA, LEED AP

Principal