District cooling making great strides in Helsinki
In the Pasila district of Helsinki work on subterranean artificial lake has been recently finished.
With a depth of more than 30 metres, and a width of 20 metres, the round pool holds 11.5 million litres of water from Lake Päijänne in central Finland, where Helsinki gets most of its city water from. The water has a temperature of about six degrees Celsius.
The pool has been set up to store the chill of the night. In the daytime, the cold is used to cool the air in Helsinki buildings.
Most of the buildings using this district cooling are business and office premises, as well as hotels and shopping malls. Large computer rooms also need to prevent overheating.
Eighty per cent of the output of the district cooling is based on energy that would otherwise go unutilised. Consequently, combined district heating and district cooling is a profitable business.
"We recycle waste energy from various users to where it is needed. We take heat and cold from the sea, and from waste water, for instance. This is not done on such a scale anywhere else", says Marko Riipinen, head of the heating operations of the municipally-owned energy utility Helsinki Energy.
Helsinki’s district cooling system has become the third-largest in Europe; only Paris and Stockholm are ahead of Helsinki.
The increase in demand for cold air has been greater in Finland than in other parts of Europe, and is expected to double in the coming three years.
"The popularity of district cooling has exceeded all expectations. In practice, we cool building space equivalent in size to 120 Houses of Parliament, and more is coming", Riiponen says. He says that entire city districts - Kalasatama, Jätkäsaari, and Ilmala, are to be served by district cooling.
Fewer than 1,000 private homes are served by district cooling, and almost all of the buildings that benefit from it are new ones.
Petri Pylsy, an energy expert from the Finnish Real Estate Federation, says that owners of old buildings are also showing interest in cold air.
Both Pylsy and Riipinen feel that the most feasible users of district cooling are buildings that contain business and office space that is rented out to tenants, as owners can charge more rent for office space that is air conditioned.
Cooling can also be retrofitted in existing residential buildings.
"If a building is to have its plumbing or ventilation systems rebuilt, it is worthwhile to include cooling in the planning of the project", Pylsy says.
Demand for cooling is growing so fast that not even the new Pasila cold water lake will be enough.
A tank of water twice as big is currently being excavated into the bedrock beneath Esplanade Park.
The cold water reservoir there will be long and narrow, and about 40 metres deep. It is to be taken into use in 2015.
"Soon we will have to come up with a place for a third pool - or then we will have to extend the pipes far out to sea, where there is no shortage of cold water", Riipinen ponders.
Last winter’s snow is (finally) water under the bridge (5.10.2010)
Heat from waste water to be used to heat Helsinki homes (11.1.2007)