District cooling

The use of waste heat is growing considerably in importance, representing an alternative way to supply environmentally sensitive cooling.

Stay cool despite climate warming

District heating represents a gain for the environment, a gain for you and guarantees a future-proof supply of energy to your property. In twenty years, experts believe that Europe will need almost as much cooling energy as heating energy. On the other hand, energy consumption should be cut to slow down climate change. If you have any questions now about how this should work – there is an environmentally friendly and economic solution: District cooling.

Smart technologies from Wien Energie

Refrigeration centre at the Vienna Main Railway Station (Hauptbahnhof)
Copyright: Wien Energie/Ian Ehm
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Vienna has been paving new ways to generate cooling energy for several years now. The focus here has been on waste heat that is produced in power plants and when waste is incinerated – a concept that has been working well for district heating for decades. In the case of district cooling, refrigeration machines generate cooling energy from waste heat, for instance.

 

A better air-conditioning unit – ideally suited to your location

Wien Energie’s district cooling is better that cooling buildings in the conventional way – saving space and protecting the environment. With two solutions that fit exactly to your needs:

  • Decentralised solution: Here Wien Energie installs a refrigeration centre directly at the customer.
  • Centralised solution: This concept uses a refrigeration centre that supplies several customers at the same time via a district cooling network.

District cooling – cool in an environmentally friendly way

In order to ensure a pleasant room temperature in office buildings, restaurants and shops, air-conditioning units have become a necessity. This is pleasant for us but not always for the environment as many cooling systems harm our environment due to the amount of electricity they consume.

Primary energy factor of district cooling compared with electricity-generated cooling
Copyright: Wien Energie
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This results in more fossil fuels being consumed, producing much higher levels of emissions. (Fig. 1)

 

It is for this reason that Wien Energie sets store by a sustainable and environmentally friendly cooling method: district cooling.

 

 

District cooling compared to conventional cooling
Copyright: Wien Energie
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It uses much less primary energy (Fig. 1) and electricity compared with conventional cooling production, and thereby cuts CO2 emissions significantly (Fig. 2). In recognition of its achievement, Wien Energie has been given the City of Vienna’s environment award.
 

Two types of district cooling concepts

Decentralised

In the decentralised district heating concept, Wien Energie installs a district cooling centre directly in the customer’s building: the refrigeration machines in the cellar and the heat exchanger on the roof. District heating is transported to the absorption refrigeration machine via the district heating network, where the heat is used to power the machine.

This solution is offered in areas where there is no district cooling network available or planned in the foreseeable future. An example of such a system entered operation on Renngasse at the end of 2013 – surrounded by listed buildings in the city centre.

Centralised

The second concept uses a large refrigeration centre that supplies customers via a connected district cooling network. It is used when the local demand for cooling is sufficiently high.

The individual buildings that are cooled receive a transfer station. This comprises a heat exchanger, including control engineering and cold-air metering.

Turning heating into cooling

Heat is an unavoidable by-product of waste incineration plants and when producing electricity. During the cold period of the year, this is used as district heating with the help of co-generation technology, serving to heat buildings and provide hot water. During the warmer half of the year, people no longer heat but waste heat continues to be produced. As a consequence, this available waste heat is used in the production of district cooling.

How does district heating become district cooling?

District cooling is produced mainly in absorption refrigeration machines in so-called refrigeration centres. The unique aspect here is that waste heat is used instead of electricity to power the machines.

This is how district cooling works.
Copyright: Wien Energie_Pablo Spitzer
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District cooling requires three water circuits: the hot water from waste incineration, the cold water supplied to the customer and the cooling water. Wien Energie obtains cooling water from the river Danube of from the cooling towers, for instance.
 

Absorbers in the centres produce cooling water which is used to cool the building. Another benefit conferred by the absorption cooling process is that no harmful coolants (HFCs) are needed. This also means that fewer harmful greenhouse gases are produced.

The water cooled to seven degrees Celsius is then transported to the customers along pipelines. The water temperature rises to around 16 degrees Celsius during the cooling process. The warm water is returned to the refrigeration centre in a closed circuit, where is then cooled again.

Complex terms explained in short

  • Absorption refrigeration machines
    produce cold air from heat. Heat is used instead of electricity to power the machine, cutting electricity consumption and greenhouse gas emissions. At Wien Energie, the lion’s share of cooling energy comes from absorption refrigeration machines. This technology is primarily used to meet base load requirements.
  • District cooling pipelines
    are insulated steel pipes or PE pipes that allow virtually no energy to escape, making transportation highly efficient.
  • Compression refrigeration machines
    represent the common technology used to produce cold air and are comparable to the cold-air generation system of a conventional refrigerator. They are powered by electricity. At Wien Energie, this technology is used to cover peaks in demand for cooling for our customers.