Absorption chillers: supplying Helsinki with cold energy for the last 20 years

Since the early 2000s, Helsinki has been using absorption chillers to convert residual heat from the urban network to cold energy to supply the city.

Results: high energy performance and positive ecological impacts.


Key figures for the project


Absorption units


Of cold energy produced for the city

0. 8

A high COP (coefficient of performance)

Absorption chillers produce sustainable cooling

The capital of Finland sees significant variations in seasonal temperatures: from -30° C to +30° C. An underground heating and cooling network, which runs over a distance of 60 km, provides heating energy in winter and air conditioning during the summer.

Absorption chillers, fed by the residual heat from the district heating system during summer, produce environmentally-friendly and energy efficient cooling.

10 chillers converting residual heat

10 units supplied by Entropie – whose heat pump activity joined CNIM Group in 2014 - have been supplying the network since 2003.

The chillers convert excess hot water from the heating network to cold energy. They have been specially adapted to the city's configuration and use Baltic Sea water as a coolant to remove the excess heat generated during the cooling process.

High performance levels

CNIM’s cooling system produces excellent results in terms of energy use. Each unit produces 3.5 MW of cold energy, the system as a whole providing 35 MW in total for the city. The COP is high: standing at 0.8 (the coefficient of performance is measured as the ratio between the energy consumed and the energy returned). The system is also profitable:

Cold energy is generated economically, the energy comes from residual heat recovery

explains Dominique Mailhot, Manager of thermal system operations at CNIM.


Positive ecological impacts

Constructed almost 20 years ago, the facilities are cited as excellent examples of good energy recovery and reuse. They economise on the use of primary energy by the recycling surplus heat during summer. They also actively help in the fight against climate change by limiting CO2 emissions (the system does not emit CO2).

Nor do the chillers produce chemical pollutants, water is used as the coolant.

Proven technology that is still the benchmark today

Materials such as titanium and alloys of nickel and copper (CuNi), enable CNIM’s chillers to resist corrosion by seawater.

CNIM guarantees that the system will have a long life-span using a line cleaning system

In conjunction with CNIM, Helsinki city is looking for ways to improve its performance in the future.

Discover CNIM Absorption Technology