National Theatre using visitors’ body heat to save energy costs

Like many cultural institutions, the National Theatre in Prague is struggling with growing energy costs and increasing demand to operate in a more sustainable way. It has recently installed innovative new heat recovery technology – using the body heat emitted by audience members.

Photo: Zuzana Machálková,  Czech Radio

The historical building of the National Theatre in the centre of Prague accommodates nearly 1,000 people. A new technology that was recently installed there captures the body heat emitted by visitors and the heat radiated by spotlights, reusing it to heat or cool down the venue.

The exhaust air is passed through heat exchangers, which capture some of the pre-heated air and send it to back to the audience, explains Jan Míka from the theatre’s technical and operations department:

Jan Mika | Photo: Zuzana Machálková,  Czech Radio

“Previously, this heat was completely dissipated to the outside environment. The heat recovery system allows us to recover some of the heat. The fresh air is then used to ventilate the auditorium and the dressing rooms.”

The heat recovery technology is not the only cost and energy saving measure adopted by the National Theatre. It has also installed solar panels on the roof of the operating building and on the adjacent New Scene.

The small power plant only provides around one percentage of the theatre’s annual energy consumption. Nevertheless, the energy produced would be sufficient to cover the consumption of five to 10 households.

Photo: Zuzana Machálková,  Czech Radio

The National Theatre also uses a small heat pump to extract heat from hydraulic oil. The oil is used in the hydraulic system employed to raise the curtain or move the theatre sets. As it operates, the oil heats up and must be cooled.

Previously, the National Theatre used drinking water to do that, which then ended up in the sewers. Thanks to the heat pump, cooling the oil has become much cheaper, says Mr. Míka:

“We use the heat we get to preheat the non-potable water, so that we don’t have to heat it only with gas. But it also saves our drinking water consumption, which previously cost a considerable amount of money. I would say we save some 16 swimming pools of drinking water a year.”

In addition, the National Theatre also has a large pump using water from the nearby Vltava River. It makes it possible to use the heat extracted from some parts of the building to be used elsewhere.

Photo: Zuzana Machálková,  Czech Radio

“The north facade is cold and we have to heat it, because the sun doesn’t shine there. However the southern facade is sunny and without cooling, it has over 30 degrees. That’s why we have to cool the offices and rooms facing the south.”

Thanks to all the adopted measures, the National Theatre can save hundreds of thousands of crowns a year. In order to operate even more sustainably, it plans to make better use of old costumes and set decorations in the future.

Authors: Ruth Fraňková , Zuzana Machálková
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