District energy
District energy refers to a centralized system that distributes thermal energy, such as heating and cooling, to multiple buildings from a single source or a network of sources. This approach allows for efficient energy generation and management, typically utilizing technologies and fuel sources that are impractical for individual buildings. Commonly found in densely populated areas, district energy systems can adapt to various fuel types and often incorporate waste heat from electric generation processes, enhancing overall efficiency and reducing environmental impact.
The economic advantages of district energy are notable; by eliminating the need for individual heating and cooling systems in each building, occupants can save on equipment, maintenance, and energy costs. Particularly in regions with high population density, such systems can be more cost-effective and less wasteful, as they reduce energy losses during transmission. While district energy is prevalent in Europe—especially in Nordic countries—its usage in the United States remains limited, primarily serving institutional facilities. The historical roots of district energy date back centuries, with examples such as a geothermal system in France operating since the 14th century and modern systems emerging in the U.S. since the late 19th century.
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District energy
Summary: District energy refers to the distribution of thermal energy to multiple buildings from one or more sources. District energy systems range in size from small systems serving a few buildings to large systems that can supply thermal energy to an entire city or region.
The idea behind district energy is simple. Rather than generating thermal energy in individual buildings using whatever fuels and equipment might be available, district energy plants can utilize technologies and fuels that would not be feasible in smaller applications. District energy systems can usually utilize multiple fuels, allowing the flexibility to meet changing energy market conditions.
The benefits of district energy can be significant, and center principally on economics, fuel savings, environmental protection, and reliability. Because heat is generated at a central site and transmitted to other buildings, those buildings do not need to have their own furnaces, boilers, or air conditioners, saving occupants money on equipment, maintenance, and energy costs. District energy plants often use the waste heat from electric generation, known as cogeneration or combined heat and power. This increases the efficiency of the thermodynamic process and can provide an additional source of revenue to the plant operator.
Because of this greater efficiency, district energy systems are kind to the environment. District energy systems are typically smaller than regular power plants, which means that they can be located closer to the buildings and people they serve, reducing the losses inherent to electricity and heat transmission. That is, more of what’s produced at a district energy plant actually gets used by consumers, rather than wasted during transmission. Their smaller size also allows for a greater flexibility in fuel type. For instance, some district energy facilities in Europe run on the solid waste generated by city residents. In this example, district energy helps the environment, not only by producing electricity and heat for local consumption, but also by preventing garbage from entering landfills. Finally, like regular power plants that run around-the-clock, district energy facilities can be extremely reliable, reducing the threat of both electricity shortages and loss of heating or cooling in buildings.
A major determining factor in the success of district energy systems is the density of the buildings that need to be heated and cooled. For instance, it might not make much economic sense to install a district energy system in a farming community where the homes are quite far apart from each other, because the costs for extending the pipe network over such great distances would outweigh the heating and cooling benefits. District energy systems are at their most efficient when serving densely populated areas, where the costs of installing the pipe system are much lower per person or per building.
After World War II, district energy systems were pursued aggressively by the forerunners of today’s European Union. As a result, district energy has become quite common in Europe, particularly in northern European and Scandinavian countries like Iceland, Denmark, Poland, and Sweden. In Denmark, more than 60 percent of all households use district heating, and in Iceland more than 90 percent of buildings are connected to geothermal district heating networks. In Stockholm, Sweden, for instance, a district energy system serves almost the entire city, producing hot water that can be used for both heating and cooling purposes. A separate seawater cooling system distributes chilled water to buildings in the center of the city. The cities in these cold-climate countries are relatively dense, so district energy makes both environmental and economic sense.
The oldest operating district energy system has provided heat from a geothermal source to the village of Chaudes-Aigues in the Cantal region of France since the 14th century. The first modern commercial system was built by American inventor Birdsill Holly in Lockport, New York, in 1877. He formed a company that established district steam systems in many communities, including one in Denver, Colorado, that began service on November 5, 1880, and another in New York City that began March 1882, both of which remained active into the twenty-first century. Most district heating systems in the United States still rely on steam, compared to the nearly universal use of hot water in Europe. District energy is widely used by institutions in the United States, but only makes up a small fraction of the American energy market.
Bibliography
Casten, Sean. “District Energy 101.” Grist, www.grist.org/article/district-energy-101. Accessed 30 July 2024.
Harvey, Leslie Daryl Danny. A Handbook on Low-Energy Buildings and District-Energy Systems: Fundamentals, Techniques and Examples. London: Routledge, 2006.
International District Energy Association. “What Is District Energy?” www.districtenergy.org/what-is-district-energy. Accessed 30 July 2024.
Proctor, Darrell. "District Energy Embraces Innovation." Power, 17 Feb. 2024, www.powermag.com/the-power-interview-district-energy-embraces-innovation/. Accessed 30 July 2024.