The Juneau District Heating is comprised of two main elements – The District Energy Plant and The District Heating Loop which are described below and depicted in the diagram below. The essential process is that heat energy is converted from the Gastineau Channel at the District Energy plant in downtown Juneau and is transferred at a high temperature to the freshwater District Heating Loop.  The power that is needed to run the pumps and machinery is supplied from the Sweetheart Lake Hydropower Facility.

Juneau District Heating – The District Energy Plant

The District Energy Plant will be located across from the Centennial Hall of Juneau and will help inspire and contribute to the downtown Juneau Renaissance that started with the state of the art State Library and Archives Museum along with the upcoming new Juneau Arts and Humanities Center (JAHC) and the Juneau’s Alaska Ocean Center that will also be located on Willoughby Avenue. The Juneau District Heating Plant will be located on the Juneau sea walk and will inform visitors of how Juneau is leading the Nation with it’s innovative and sustainable heating system. The District Energy plant will house the seawater heat exchangers and heat pump equipment used for taking in the heat from seawater and transferring it to the freshwater District Heating Loop along with offices, retail shops and apartments.  Ample parking will assist events taking place downtown.

The District Energy plant will house the seawater heat exchangers and heat pump equipment used for taking in the heat from seawater and transferring it to the freshwater District Heating Loop. The heat is exchanged between the salt and freshwater, but the water supplies are not actually mixed.

The District Energy Plant is designed to provide heating year round with maximum heat generation in the winter. The basic operation of the District Energy Plant is to take in seawater at about 100 feet in depth from the Gastineau channel where the water is warmer than at the surface.  The seawater heat pump system operates by drawing in this relatively warmer water from the Gastineau Channel into the District Energy Plant where a network of heat exchangers and the innovative Emerson Seawater Heat Pumps (SWP) transfer the heat to create high temperature freshwater above 180° F . This high temperature freshwater will supply heat to the buildings in Juneau, which include State owned, commercial businesses (hotels, banks, office buildings, hospital, schools, restaurants, etc.), and even home residences.  After heat is extracted at each location, a return pipe returns the colder water back to the District Energy Plant for reheating and process begins all over.

The colder salt water is returned back to the Gastineau Channel with no harmful environmental effects.

Juneau District Heating – The District Heating Loop

The District Heating Loop will consist of the “hot” (above 180°F) fresh water piping that leaves the District Heating Plant to be circulated and transferred to customer locations via an on-site energy transfer station (ETS). After the customer receives their heat from the water, the now slightly cooler freshwater will return via piping along a parallel path back to the District Energy Plant, where it will be reheated and recirculated again and again.  The main hot delivery and colder return piping is to be constructed in parallel paths throughout the district. The ETS systems will be connected to the customer building hydronic heating systems.

With the use of the Emerson Seawater Heat Pump technology there is no need for an expensive building hydronic system piping “rip and replace” retrofit. The connection to the district heating supply simply adds an energy transfer station on the building premises that connects to the building hydronic system. The facility provides hot water heat on one side and discharges colder water on the other side that is returned to the district energy plant for reheating. A Btu meter monitors the amount of Btu’s that is used by the customer.

The City and Borough of Juneau (CBJ) stongly supports the creation of a Juneau District Heating. The broad public support from Juneau citizens and  many potential customers to reduce the energy costs and make Juneau a more sustainable city is overwhelming.