District cooling is a sustainable and energy-efficient solution for cooling buildings and communities. Centralized production plants with large, highly efficient equipment produce and distribute chilled water to supply buildings through an underground insulated piping system. The cold water enters the buildings, where it flows through a heat exchanger and absorbs the heat from the building space after which it recirculates back to the centralized plant through a closed look return line.
What is district cooling?
District cooling is a centralized cooling system that provides chilled water or other cooling sources from a central plant to multiple buildings or facilities within a specific area or district. It works similarly to district heating but focuses on delivering cooling instead of heat. District cooling systems are often used in urban areas to improve energy efficiency, reduce environmental impact, and provide reliable cooling to multiple buildings.
Reduce energy consumption and carbon emissions
District cooling systems can reduce energy consumption and carbon emissions compared to traditional cooling methods by centralizing the production and distribution of chilled water. Not only does this combat climate change, but it also leads to cost savings for building owners and residents.
Replacing air conditioning
In urban areas globally, district cooling plays a crucial role in energy systems by reducing the pressure on the power grid due to the rising air condition needs. Air conditioning usually consumes a significant portion, typically 50-70% of peak electricity demand. District cooling combines the cooling requirements of multiple buildings, creating an economy of scale that boosts efficiency, evens out the load on the electric grid, and trims down fuel expenses.
Innovative district cooling technologies
Furthermore, the aggregation of district cooling systems enables the adoption of innovative technologies such as eco-friendly lake or ocean water cooling, greywater reclamation, treatment of sewage effluent, and thermal energy storage. These technologies help reduce costs and the environmental impact associated with air conditioning.
Central cooling plants also circumvent the sunk costs of oversized individual chiller plants and the capital expenses associated with chiller and cooling tower installations. This frees up valuable rooftop and building space. Alongside its numerous advantages, district cooling stands as an innovative solution gaining global momentum to meet the growing demand for cooling while preserving our planet.
Rising cooling demands: A looming energy challenge
It’s estimated that nearly 20% of the world’s total electricity consumption is dedicated to cooling, primarily through air conditioners and electric fans in buildings. Moreover, the electricity demand for cooling is expected to surge due to urbanization, industrialization, climate change, and rising global living standards, with some predicting a threefold increase in current cooling-related electricity demand. Additionally, the unregulated use of chillers can lead to peak cooling demands and the risk of power outages.
Unlocking the potential of district cooling
While district heating systems are broadly used worldwide, district cooling is less commonly employed for meeting cooling needs, providing only approximately 300 PJ/year globally. However, district cooling could offer a more efficient and cost-effective option for addressing cooling demands. It allows for natural cooling methods and greater flexibility in the operation of energy conversion units. Consequently, district cooling could facilitate better integration of renewable energy sources into the energy system and potentially connect with district heating systems.
District cooling worldwide
The global district cooling market is on the rise, with various regions experiencing significant growth in this energy-efficient cooling solution. In the United States, campus-based district cooling systems have been in operation for many years. Meanwhile, in the Gulf Region (GCC), investments in district cooling are increasing annually, leading to widespread adoption in the UAE and Saudi Arabia. Across Asia, the Chinese market stands as the largest, with notable growth in Southeast Asian countries like Singapore, Malaysia, and Thailand. India, although having a few operational district cooling projects, has plans for many more in the pipeline.
Even in colder parts of Europe, there has been a substantial development in district cooling, primarily for hotels and office buildings over the past decade. The highest district cooling penetration can be observed in Sweden at 18.4%, followed by Finland at 14.8%, and France at 11.2%. These systems draw from various sources, including waste heat from power plants, industrial processes, or incinerators, as well as renewable energy sources like solar thermal, geothermal, and biomass. Natural cooling sources such as seawater, lake water, or river water are also utilized.
Examples of district cooling systems in Europe
- Paris, France: The first significant European district cooling system was established in 1967 in the Courbevoie, Nanterre, and Puteaux areas, serving numerous office buildings in the La Defense area. The system, jointly operated by Enertherm and SOC, uses chilled water generated from a combination of compression chillers and free cooling from the Seine River, transmitted through pre-insulated underground pipes. Another initiative, the Climespace system, was formed in Paris city center in 1991, utilizing the Les Halles cooling plant from 1978 and incorporating the Seine River as a heat sink. This system has the highest annual cold delivery capacity among all European district cooling systems, nearly 500 GWh per year.
- Stockholm, Sweden: Established in 1995, the Stockholm district cooling system supplies cooling to more than 400 buildings, mainly using cold supply obtained from large heat pumps providing heat to the district heating system. It caters to both comfort and process cooling, employing various technologies, such as compression and absorption chillers, free seawater cooling, and waste cooling from heat pumps.
- Copenhagen, Denmark: The Copenhagen district cooling system, known as HOFOR DC, was established in 2010 and combines compression chillers with seawater cooling. It boasts a 52 MW cooling capacity for 62 large buildings, covering 1.1 million square meters of floor area. Seawater is the primary cooling source, supported by ammonia compression chillers and an absorption chiller during the warmer months.
- Helsinki, Finland: The Helsinki district cooling system, initiated in 1998, relies mainly on the Katri Vala heating and cooling plant for cold supply. The system has expanded to include 562 buildings and 90 kilometers of trench length. It utilizes a range of technologies, including heat pumps, absorption chillers, compression chillers, and seawater cooling, along with cold storage in rock caverns. This system demonstrates an intelligent energy approach, efficiently supplying both heat and cold in a sustainable manner through a set of versatile heat pumps. These heat pumps cool the return water from the district cooling network and provide heat to the district heating system.
Suggested reading for more information about district cooling:
The four generations of district cooling – A categorization of the development in district cooling from origin to future prospect (sciencedirectassets.com)
District Cooling Gaining Popularity in Copenhagen – DBDH
District Cooling – International District Energy Association