Warsaw is one of the first European cities to implement a pilot installation for recovering heat from the metro

Warsaw is one of the first European cities to implement a pilot installation for recovering heat from the metro using heat pumps to feed the municipal heating network. Expert Dr. Eng. Piotr Ziętek believes that heat recovery systems can play a significant role and improve the energy efficiency of technical installations.

Issues of heat recovery from underground metro infrastructure are currently being taken into account on two metro lines: M2 and the planned M3 – Anna Bartoń, spokeswoman for the Warsaw Metro, told PAP.

– On the second line, a pilot installation is to be installed at the Bemowo station. Currently, we are in the final stage of processing the contract between Metro Warszawskie and Veolia with the participation of the Infrastructure Office of the Municipal Office. Design work is underway for the M3 line and, in parallel, arrangements are being made for technical solutions regarding the future location of the installation, the spokeswoman said.

As told to PAP by Dr. Eng. Piotr Ziętek from the Faculty of Environmental Engineering at the Warsaw University of Technology, recovering heat from metro infrastructure most often involves using ventilation air from tunnels and metro stations to power air-water heat pumps. These devices – by implementing a thermodynamic cycle – are able to raise the temperature of the collected heat to a higher level and transfer it to the receiving installation.

– Building an installation to use heat from ventilation air from the subway to supply heat to nearby buildings is a very complex engineering task that uses innovative technologies, e.g. high-power heat pumps with ecological working fluids. This may contribute to reducing pollutant emissions by limiting the consumption of energy produced in a traditional way, emphasized Ziętek.

The expert noted that Currently, solutions are being sought to improve the energy efficiency of technical installations, including heat sources, and heat recovery systems can play a significant role in this.

For now, the idea of ​​recovering heat from the subway is not widely spread around the world, but – as the expert noted – its potential has been noticed. – Analyzes are ongoing and the first pilot and demonstration installations are being built in various countries, including: Germany, Scotland, Poland – he said.

An installation using heat from the subway to heat nearby buildings was carried out, for example, in London. – Bunhill 2 Energy Center uses heat from subway tunnels and supplies heat to, among others, 1,350 residential buildings and several public buildings – Ziętek said.

In the model being prepared in Warsaw, the heat generated by operating devices and ventilation systems in the Warsaw metro will be recovered using heat pumps and directed to the municipal heating network.

– The metro uses very large air streams, which are needed, among others, to ensure appropriate air quality for passengers, but also to receive heat gains generated by people, trains and other station and tunnel equipment – said Ziętek.

He noted that the air temperature in the metro is relatively stable and high throughout the year – in winter it does not drop below 10 degrees Celsius, and in summer, during hot weather, it can even exceed 25 degrees Celsius. – Thanks to this, the air from the metro is an attractive heat source for pumps, the efficiency and effectiveness of which increases with the increase in the temperature of the lower heat source – said the expert.

In his opinion Heat pumps are an ideal technology for recovering heat streams of different, often unusual temperatures and reusing them in another place.

– Low-temperature heat collected from the indoor air in the subway is transformed by heat pumps to a higher temperature level and thus becomes useful for heating purposes, e.g. for additional heating of the municipal heating network – said Ziętek. An additional benefit is that the cooled ventilation air, when properly distributed, can lower the temperature in the metro station, which is especially beneficial during the summer heat.

The implementers of the solution in Warsaw emphasize that the technology and method of heat recovery from the metro infrastructure will additionally reduce the temperature on the platforms – by up to 4 degrees C. According to an expert from the Warsaw University of Technology, this temperature is noticeable to metro users. – It should not cause significant discomfort in winter, and in summer it can certainly improve thermal comfort conditions at a given station – he said.

The Warsaw City Hall announced that new locations will be selected after the installation of heat pumps in Bemowoi.e. metro stations where preparations for the installation and launch of subsequent recovery installations will begin.

According to Ziętek, it is worth going in this direction “as long as there are appropriate technical conditions, including available technical space for the installation of heat pumps, the possibility of appropriately directing the ventilation air flow and the proximity of the heat recipient, e.g. in the form of a heating network or buildings to which the heat can be transferred.”

The heat recovery project from the Warsaw metro tunnels was created as part of the 3rd edition of the Innovation Competition at Veolia Energii Warszawa in 2021. The idea won the main prize – the Grand Prix and was included in the program of projects regarding heat recovery sources in the city.

Anna Mikołajczyk-Kłębek (PAP)

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