District cooling is the cooling equivalent of district heating. Working on broadly similar principles to district heating, district cooling delivers chilled water to buildings like offices and factories needing cooling. In winter, the source for the cooling can often be sea water, so it is a cheaper resource than using electricity to run compressors for cooling. Alternatively, District Cooling can be provided by a Heat Sharing Network which enables each building on the circuit to use a heat pump to reject heat to an ambient ground temperature circuit.
Applications
Finland
The Helsinki district cooling system uses otherwise wasted heat from summer time CHP power generation units to run absorption refrigerators for cooling during summer time, greatly reducing electricity usage. In winter time, cooling is achieved more directly using sea water. The adoption of district cooling is estimated to reduce the consumption of electricity for cooling purposes by as much as 90 per cent and an exponential growth in usage is forecast. The idea is now being adopted in other Finnish cities.
Sweden
The use of district cooling grows also rapidly in Sweden in a similar way.
United States
's Lake Source Cooling System uses Cayuga Lake as a heat sink to operate the central chilled water system for its campus and to also provide cooling to the Ithaca City School District. The system has operated since the summer of 2000 and was built at a cost of $55–60 million. It cools a 14,500 tons load.
Switzerland
Working since 1985, the system of the École Polytechnique Fédérale de Lausanne combines, depending on the needs, cooling and heat extraction. This allows for a higher overall energy efficiency of the 19 MW system. In 2009, a district cooling system was installed in the United Nations area of Geneva, drawing water from Lake Geneva. The system is in the process of being expanded to other areas of Geneva.
In August 2004, Enwave Energy Corporation, a district energy company based in Toronto, Ontario, Canada, started operating a system that uses water from Lake Ontario to cool downtown buildings, including office towers, the Metro Toronto Convention Centre, a small brewery and a telecommunications centre. The process has become known as Deep Lake Water Cooling. It will provide for over 40,000 tons of cooling—a significantly larger system than has been installed elsewhere. Another feature of the Enwave system is that it is integrated with Toronto's drinking water supply. The Toronto drinking water supply required a new intake location that would be further from shore and deeper in the lake. This posed two problems for the utility that managed the city's drinking water supply: 1. the capital cost of moving the water intake location and 2. the new location would supply water that was so cold it would require heating before it could be distributed. The cooperation of the district cooling agency, Enwave, solved both problems: Enwave paid for the cost of moving the water intake and also supplied the heat to warm the drinking water supply to acceptable levels by effectively extracting the heat from the buildings it served. Contact between drinking water and the Enwave cooling system is restricted to thermal contact in a heat exchanger. Drinking water does not circulate through the Enwave cooling systems.
United Arab Emirates
Tabreed currently delivers over 1 million refrigeration tons of cooling, across 72 plants located throughout the region, cooling iconic infrastructure projects such as Sheikh Zayed Grand Mosque, Cleveland Clinic, Ferrari World, Yas Mall, Aldar HQ, Etihad Towers, Marina Mall, World Trade Center in Abu Dhabi featuring the Burj Mohammed Bin Rashid, Dubai Metro, Dubai Parks & Resorts, and the Jabal Omar Development in the Holy City of Mecca, alongside several other hotels, hospitals, residential and commercial towers. In January 2006, PAL technology is one of the emerging project management companies in UAE involved in the diversified business of desalination, sewage treatment and district cooling system. More than 400,000 Tons of district cooling projects are planned. The Palm Jumeirah utilises district cooling supplied by to provide air conditioning for buildings on the trunk and crescent of the Palm. The Dubai Metro system, inaugurated in 2009, is the first mass transit network in the world to use district cooling to lower temperatures in stations and trains.
Netherlands
In 2006, a district cooling system came online in Amsterdam's Zuidas, drawing water from the Nieuwe Meer
India
India's first district cooling system is operational in GIFT City. Currently ~10,000 TR capacity is operational which has capacity to upgrade up to 50000 TR. Gujarat International Finance Tec-City in Gujarat.
Qatar
On November 9, 2010, The world's largest district cooling plant opened at The Pearl-Qatar. This plant is owned and operated by Qatar District Cooling Company. It is capable of cooling a load of 130,000 tons. The Plant was Built by C.A.T. group, a Lebanese-International general contractor with vast experience in District Cooling. The Lusail City district cooling system will supply chilled water to end users through an integrated network with a connected cooling of 500,000 Tons of Refrigeration by utilizing multiple chiller plants which are Marina, Wadi, West and North. This will be one of the largest district cooling systems in the world.
Kuwait
A project started in 2012 in Kuwait for the Sabah Al-Salem University City with district cooling. It is capable of cooling a load of 72000 TR and it has two central utility plants with 36 chillers, 36 cooling towers and 2 TES tanks.
Germany
In Germany, amongst :de:Fernkälte#Anwendungsbeispiele|other projects, Munich established a rapidly growing system in 2011 with its core below the Karlsplatz, drawing water from the underground Stadtgrabenbach. There's a 24 km network, currently supplying 16 larger organizations. In 2011, the estimated total thermal power output of all district cooling systems in Germany was 160 Megawatt distributed over 90 km.
Cold storage
If the other renewable alternatives are too warm during the summer or too expensive, cold storage can be investigated. In large scale applications underground and snow storage are the most likely alternatives. In an underground storage the winter cold is heat exchanged from the air and loaded into the bedrock or an aquifer by one or more bore holes. In a snow storage frozen water is saved in some kind of storage. The cold is utilized by pumping melt water to the cooling object, directly in a district cooling system or indirect by a heat exchanger. The lukewarm melt water is then pumped back to the snow where it gets cooled and mixed with new melt water. Snow cooling works as a single cold source but can also be used for peak cooling since there is no relevant cooling limit. In Sweden there is one snow cooling plant in Sundsvall, built and owned by the county. The cooling load in Sundsvall is about 2000 kW and 1500 MWh/year.
Dehumidifying
Especially in subtropical regions not only cooling, but dehumidifying of the air becomes important. Liquid desiccant cooling allows to generate remotely and efficiently a moisture absorbing liquid. This liquid can be pumped or transported long distances without energy loss.
