District Energy
ASHRAE Technical Committee 6.2

The ASHRAE Handbook is published in a series of four volumes, one of which is revised each year, ensuring that no volume is older than four years.  The Handbook can be purchased at the ASHRAE Bookstore by clicking on this link.

This TC is responsible for the following chapter in the HVAC Systems & Equipment Volume :

ASHRAE HVAC SYSTEMS & EQUIPMENT: District Heating & Cooling
District heating and cooling (DHC) or district energy (DE) distributes thermal energy from a central source to residential, commercial, and/or industrial consumers for use in space heating, cooling, water heating, and/or process heating. The energy is distributed by steam or hot- or chilled-water lines. Thus, thermal energy comes from a distribution medium rather than being generated on site at each facility. Whether the system is a public utility or user owned, such as a multibuilding campus, it has economic and environmental benefits depending somewhat on the particular application. Political feasibility must be considered, particularly if a municipality or governmental body is considering a DHC installation. Historically, successful DHC systems have had the political backing and support of the community.

The ASHRAE HVAC SYSTEMS & EQUIPMENT HANDBOOK may be purchased from the on-line bookstore by clicking on the highlighted text.

Comment on the Handbook: ASHRAE welcomes your comments on the Handbook or a specific Handbook chapter.  To submit a comment about any aspect or part of the Handbook series, you can use the Handbook Comment Form.

Review a Handbook Chapter: To provide your feedback about a specific Handbook chapter, you can answer the brief survey questions on the Handbook Chapter Review Form.

Technical committees develop and sponsor technical sessions at the winter and annual conferences. Information about their future technical program is discussed at each TC meeting and at the TC’s Program Subcommittee meeting

ASHRAE publishes papers and transactions from presentations at its conference events. In addition, ASHRAE records most of the seminar sessions from its conferences on DVD. These DVDs are ideal for use at chapter meetings, in university courses, or company lunch and learns. Products available from the most recent conference may be found here.

Technical Committees are responsible for identifying research topics, proposing research projects, selecting bidders, and monitoring research projects funded by ASHRAE. Information about their specific research program is discussed at each TC meeting and at the TC’s Research Subcommittee meeting.

ASHRAE writes standards for the purpose of establishing consensus for: 1) methods of test for use in commerce and 2) performance criteria for use as facilitators with which to guide the industry. ASHRAE publishes the following three types of voluntary consensus standards: Method of Measurement or Test (MOT), Standard Design and Standard Practice. ASHRAE does not write rating standards unless a suitable rating standard will not otherwise be available. ASHRAE is accredited by the American National Standards Institute (ANSI) and follows ANSI's requirements for due process and standards development. Standards may be purchased at the ASHRAE Bookstore.

ASHRAE Technical FAQs are provided as a service to ASHRAE members, users of ASHRAE publications, and the general public. While every effort has been made to ensure their accuracy and reliability, they are advisory and provided for informational purposes only, and in many cases represent only one person’s view. They are not intended and should not be relied on as an official statement of ASHRAE. Technical questions not addressed may be submitted to the ASHRAE Technical Services department at tse@ashrae.net.

The following FAQs used courtesy of the International District Energy Association (IDEA).

What is district energy?

District energy is not a new technology. It is not a technology we have to wait to test or to research. It is here today, it works today, and it holds great promise for our nation.

District energy systems produce steam, hot water or chilled water at a central plant and then pipe that energy out to buildings in the district for space heating, domestic hot water heating and air conditioning. Individual buildings don't need their own boilers or furnaces, chillers or air conditioners. A district energy system does that work for them.

Why district energy?

The beauty of a district energy system is that since it serves so many customers from one location, it can accomplish things individual buildings usually cannot. For instance, district energy systems can use a variety of conventional fuels such as coal, oil and natural gas, whichever fuel is most competitive at the time. And because of a district energy system's size, the district energy plant can also transition to use renewable fuels such as biomass, geothermal, and combined heat and power.

Buildings connected to district energy systems also have lower capital costs for their energy equipment because they don't need conventional boilers and chillers. They save valuable upfront dollars they can invest elsewhere. Plus, they save building space that can be used for other more valuable purposes.

Is district energy reliable?

Building owners and managers can count on district energy systems since energy professionals operate around-the-clock and have backup systems readily available. Most district energy systems operate at a reliability of "five nines" (99.999 percent). To IDEA's knowledge, there have been no rolling "heat-outs" related to district energy systems!

Why haven't I heard of district energy?

You may not have heard of district energy, yet these systems operate in nearly every major city in the United States, from Manhattan to Seattle, and on most of our university campuses.

Many people may not be familiar with district energy because it quietly does its job - with rarely a crisis to report. Plus, the pipes that deliver the steam, hot water and/or chilled water are usually buried underneath the streets, so most people don't know they are there.

What is combined heat and power?

Combined heat and power - also known as cogeneration - is a way to increase the efficiency of power plants. Standard power plants effectively use just 40 percent of the fuel they burn to produce electricity. Sixty percent of the fuel used in the electric production process ends up being rejected or "wasted" up the smokestack.

Combined heat and power uses this reject heat to heat buildings in a surrounding area through a district energy system. Combined heat and power is only possible when there is an area near the plant that has a need for the heat - a downtown area, a college campus or a industrial development.

If one of our nation's energy challenges is lack of power, what if we doubled the efficiency of as many power plants as possible and got more energy for every gallon of oil or ton of coal they burn? Combined heat and power can help us do just that - and even help the environment in the process since less heat and fewer emissions will be rejected into the atmosphere.

Why is district energy good for our cities?

District cooling systems, in particular, displace peak electric power demand with steam-based cooling, district cooling, and storage using ice or chilled water. This benefits the local power grid by reducing peak power demand and alleviating power congestion due to power transmission limitations in cities. So district energy not only helps heat and cool cities, it helps alleviate the challenges posed by high electric consumption.