Juneau District Heating uses heat from the sea

The Juneau District Heating system takes in seawater 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 energy from the seawater to create a high temperature freshwater supply to heat the buildings in Juneau.



The SWP converts the existing Btu’s in “cold” seawater into useable energy at high temperatures. The system has a Coefficient of Performance (COP) above 300%, meaning that for every 1 Btu of electricity input into the system to run the system and move the water, 3 Btu’s of useful heat are delivered to the freshwater system.

The Emerson Climate Technologies patented system of compressors and high temperature heat pumps provide a viable alternative to power District Heating without requiring the burning of fossil fuels. Furthermore, the refrigerant used does not affect the ozone in any way. The entire process is 100% renewable because it uses the heat contained in seawater which is in abundant supply.

The heat energy source for the entire District Heating is harvested from the ocean where it was heated by the sun. In essence the ocean water is a solar collector with a zero carbon load. As long as there is sun and seawater, the District Heating District can produce the heat to warm the businesses and homes in Juneau.

Learn more about District Heating Design

Sweetheart Lake

Juneau District Heating – Powered by Sweetheart Lake

Juneau District Heating will be the first District Heating project in the US to use 100% renewable sources. Other District Heating in the US use the burning of fossil fuels to create the centralized heating supply and they receive electrical input from a variety of sources. A synergistic innovation of the District Heating project is that the electricity needed to run the pumps and compressors in the system will come from a completely renewable and non-polluting energy source – The Sweetheart Lake Facility. Sweetheart Lake generates electricity by the power of gravity. Water flows downhill from the Sweetheart Lake via a tunnel to turn a turbine coupled to a generator. There is no pollution. This process is self sustaining and a reliable catalyst to drive the Juneau District Heating system that converts the heat from seawater into a usable form for the residents and businesses in Juneau.