Have you ever considered in detail the systems by which American households are heated and cooled at the flip of a switch? For many of us, knowing that we can cool down in the midst of a triple digit heat spell, and conversely, become quite toasty on a frost-ridden day, is enough. Yet here we are, in the 21st century, dealing with an energy crisis and undeniably more formidable, greenhouse gas .2 Enter, district heating and cooling. This technological concept has been adopted by many countries around the world, including the United States. Pioneered by a number of European countries, this system is much more energy efficient than that of conventional heating and cooling, and it also reduces polluting emissions. Furthermore, district energy has promising potential to lead progressive conversation surrounding future sustainable energy policies, both domestic and international.
Conventional Heating and Cooling Systems
The average American household has on-site, central heating and cooling units that are connected to a network of transmission pipelines that convey, most commonly, fossil fuels.4 Typically, heating systems burn fuel such as natural gas or fuel oil, while air conditioners use electricity. Each house has a localized boiler, furnace, and/or air conditioner that use a single distribution system to circulate air, and are controlled by a thermostat, or a device that regulates the temperature of your home.
Heating systems, such as a furnace or heater, consume fuel, creating heat as a byproduct, which then travels through the distribution system—ducts, pipes, or wires—and heats the living space. Whereas heating systems generate heat to warm an office building or house, air conditioners remove heat from the air. Air conditioners are powered by electricity and cool warm air that comes into contact with its cooling coils. In the cooling coils is a gas that is cooled to its liquid state that subsequently cools the passing warm air. The cooled air is then distributed throughout your house using the same network of ducts or pipes through which heated air is distributed.5
As aforementioned, this conventional heating and cooling system is largely inefficient as only 80%, or less, of the energy source being used, whether it be natural gas or oil fuel, is converted into useful heat.6 The rest is considered “reject heat,” which is lost through venting systems that effectively channel exhaust gases composed of nitrogen, soot , carbon monoxide, nitrogen oxides and sulfur oxides; all of which can be harmful to the environment and to human health. There are actions that can be taken, however, to improve efficiency of your home heating and cooling systems, such as:
- Maintaining the mechanical equipment – replacing old, inefficient systems can cut utility costs by up to 50 percent by improving fuel efficiency.
- Regular maintenance and repair of the distribution system to minimize loss through poor insulation.
- Minimizing use of system altogether.
- Ensure that venting systems and chimneys align with building code regulations so as to maintain energy efficiency, indoor air quality, and fire safety.7
District Heating and Cooling
Otherwise known as district energy, this technology can be found in major cities and college campuses throughout the world.8 Rather than relying upon individual household furnaces or air conditioners, district energy production is confined to a central energy plant. This system produces steam, hot water, or chilled water that is then transported to buildings and households through an underground network of pipes—rendering individual furnaces, boilers, and air conditioners useless. Often times, district energy systems operate in tandem with a combined heat and power (CHP) plant, also known as a cogeneration plant. Cogeneration plants produce electricity, as well as heating and cooling, and are able to convert more than 80% of energy into useable forms by recycling the “reject heat,” generated from the burning of fuels, to heat or chill water.9 The steam, hot water, or chilled water is 100% efficient.10
District and heating systems achieve economies of scale in staffing, energy sources, technology, and equipment.11 Because district energy systems recycle surplus heat, less energy is used and emissions are significantly cut. These plants are able to invest in state of the art technology that “reduce[s] the amount of energy lost up the smokestack”12 and are subject to more stringent emission regulations than individual buildings.13 Additionally, district energy systems have greater fuel flexibility, in that they are able to use any conventional fossil fuel that is most competitive at the time, or more appealing, they are able to use a variety of geothermal heat , hydrothermal, solar thermal, biogas, and municipal solid waste.14 This also adds to the energy efficiency that is characteristic of district energy systems.
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Lastly, district energy is more convenient for the customers. Maintenance and operation of household heating and cooling units are no longer necessary, and district energy is always ready to use. Technicians are available around the clock to guarantee proper functioning of the system at all times. Much like the conventional system, thermostats are used to regulate room temperatures and modern heat meters or allocators measure the amount of energy each household consumes and thusly pays for.16 Lastly, district cooling greatly reduces peak electricity loads during the summer, as air conditioners are no longer needed, thus reducing consumer costs.17
All in all, district heating is easy, convenient, efficient, and environmentally friendly! Many cities have already begun to implement this system, as it is one of many catalysts of change in energy and climate change policies, bringing us one step closer to fighting the phenomenon that is global warming .
