DISTRICT HEATING AND COOLING
District Heating And Cooling
District energy, both heating and cooling, tie together the energy generating sources in a city with buildings and facilities having a need of heating and/or cooling. Instead of each building having its own heating or cooling system, the energy is delivered to several buildings in a larger area from a central plant. The water-based distribution system guarantees that heat and cooling arrive safely to the end users. With district heating, energy is saved overall, as it takes advantage of resources that would otherwise not be have been used, making it an efficient and sustainable solution to satisfy the local heat and cooling demand in a city.
DISTRICT HEATING
District heating is the most widespread of the two types of district energy; heating and cooling. To transport heat efficiently, the district heating distribution infrastructure comprises a network of insulated pipes, delivering heat in the form of hot water, from the generation site to the end user. Networks can measure from a few hundred meters to covering entire large cities. End users range from residential buildings to offices and industrial facilities. The network’s coverage can easily be extended by laying more pipes, often in combination of adding more points of generation.
GENERATION AND FUELS
Heat is usually generated in two types of plants. The basic one is a heat generation plant with a boiler that only generates heat. The second type is a cogeneration plant, often called combined heat and
power plant
(CHP). As it generates both heat and electricity, it benefits from considerable economies of scale. Upon generating electricity by incineration, the steam from the boiling water that drives the turbines is lead to also heat the water in the closed circuit district heating system. It can also be used as steam in industrial processes. DISTRIBUTION INFRASTRUCTURE
After the heating process in the central plant, the hot water is transported through isolated pipes under high pressure and the water’s temperature remains between 70 and 120 degrees Celsius (160-250°F), depending on the season and weather. Upon arrival, the building’s heat exchanger uses the district heating system’s hot water to heat its own water system for tap water and radiators in the building. Smart metering and control systems give customers the opportunity to adjust their own heat consumption.
DISTRICT COOLING
The district cooling system in Stockholm was implemented on a larger scale during the 1990’s. It is based on the same distribution principle as district heating, and can be generated by different fuel sources and techniques. Free water cooling is a common technique, using sea or lake water in order to cool the water in the system. Heat pumps, generating both heating and cooling, as well as cooling machines can also be used. Another way is to use the heat energy from the district heating in cooling sorption machines.
Compared with a traditional air conditioning system, this network:
- consumes 35 % less electricity,
- emits 50 % less CO2,
- greater than 50 % energy efficiency,
- 65 % less water consumption.
