Brattleboro Thermal Utility, Inc.
Marlboro College Technology Center, 1st Floor
28 Vernon Street
Brattleboro, VT 05301, USA
What is District Energy?
District energy systems produce steam, hot water, or chilled water centrally and distribute it to multiple buildings through a network of buried, insulated pipes. Buildings connected to that network use this thermal energy for space heating, domestic hot water heating, or air conditioning instead of having separate heating or cooling equipment.
What is Combined Heat and Power (CHP)?
Thermal power plants producing only electricity operate at a thermal efficiency of about 30% with the remainder rejected as heat into the atmosphere. Combined Heat and Power (CHP) utilizes both the heat and the power, significantly boosting plant efficiency and reducing air emissions. District energy systems can use CHP - also called cogeneration - as a low-cost source of thermal energy.
Where are systems like this being used now?
District energy systems are used very widely in northern Europe. In Denmark and Sweden, for example, more than half of all homes are heated with district heating systems. There are hundreds of wood-fired CHP plants that provide heat to district energy systems in Europe.
In December, 2007, BTU Board member Alex Wilson traveled to Sweden, where he toured several cutting-edge district heating plants, including those in the award-winning cities of Vaxjo and Kristianstad. Read his photo-rich blog here: Notes from Sweden #4 - CHP and District Heating
In the United States, there are about 6,000 district heating systems using old technology (including steam instead of hot water as a heat-transfer medium). Most serve university campuses, hospital complexes, military bases, and downtown areas of large cities, although a handful serve smaller communities. Wood chips are currently used fairly widely in Vermont for heating schools and a few downtown areas. For example, a wood chip boiler heats Brattleboro Union High School and Middle School, and the Windham County Career Center, but it provides heat only, not electricity. There are a small number of woodchip-fired CHP district systems across the country, ranging from Mount Wachusett Community College in Massachusetts to the City of St. Paul, Minnesota where a 25 MW wood-residue CHP plant serves the largest hot-water district energy system in North America, and one of the only examples of a technology that is now commonplace in northern Europe.