District energy, a heating and cooling system that has existed for centuries, may be the ticket to making modern communities more energy efficient. While district heating systems have been used as far back as the hot water-heated baths and greenhouses of ancient Rome, use of this energy efficient system has been underutilized in recent history. District energy systems tap into a central source of thermal energy to pump steam, hot water, and/or cold water through heavily insulated pipes to either heat or cool nearby buildings. In essence, this system removes the need for individual building operators to retain their own heating or cooling unit, saving them both space and money. District energy systems are ideal for relatively dense built environments such as hospitals, military bases, college campuses, and compact downtown areas.

Currently, more than 30 percent of all U.S. energy consumption is used for thermal purposes – heating and cooling – and the majority of this energy comes from fossil fuels. However, district energy systems can use different energy sources to increase energy efficiency and reduce dependence on fossil fuels.

Most district energy systems are powered through a central plant, using a technology known as combined heat and power (CHP). CHP captures the “waste heat” from electricity generation that would otherwise be released into oceans, rivers, or the atmosphere. (A conventional non-CHP power plant wastes up to two-thirds of the energy in its fuel source through heat). District energy systems put this waste heat to productive use in surrounding heating and cooling systems.

Another heat source that can be used to displace fossil fuels are renewable thermal energy sources. Renewable resources such as water, solar, geothermal, and biomass energy can be applied to a district heating or cooling system.

St. Paul, Minnesota is one community with a successful district energy system which uses CHP and wood chips, natural gas, oil or coal. District Energy St. Paul heats more than 185 buildings and 300 single-family homes (31.1 million square feet) and cools more than 95 buildings (18.8 million square feet) in downtown St. Paul and adjacent areas. In June of this year, District Energy St. Paul received the System of the Year Award from the International District Energy Association for its ability to serve twice the square footage today with the same amount of energy input as when the system began operation in 1983, among other advancements. Customers of District Energy St. Paul enjoy stable rates and reliable and efficient heating and cooling services.

On Thursday, September 16, the Environmental and Energy Study Institute (EESI) will bring experts to Capitol Hill to give a briefing on how district energy systems can tap into local renewable thermal resources and waste heat to reduce our dependence on fossil fuels. Speakers will include Rob Thornton and Mark Spurr of the International District Energy Association, Ken Smith of District Energy St. Paul, and Neal Elliott of the American Council for an Energy-Efficient Economy. The event is free and open to the public, and the presentations will be posted at www.eesi.org/briefings following the event.