Discover how heat from a rubbish tip is being used to heat and cool homes through ‘absorption cooling’

The Spittelau waste to energy plant in Austria
Absorption cooling is used in the Spittelau waste to energy plant in Austria (Image credit: Getty Images)

It seems burning rubbish could be the future to keeping our houses warm (and cool) as a waste incinerator plant in Vienna, Austria, is doing just that.

The plant uses the heat it generates to power district cooling  – where towns and cities are serviced by large and energy-efficient central air conditioning systems.

Burning rubbish at the Spittelau waste-to-energy plant powers an absorption chiller, which uses a thermodynamic process called absorption cooling that allows water to be chilled and distributed for heating, ventilation and air conditioning (HVAC) needs.

Energy firm Wien Energie Fernwärme now plans to install further capacity in Spittelau because of demand and also to build up new schemes. We explain how it works, its benefits and how likely it is we will see a similar scheme come to the UK.

How does absorption cooling work?

Heat can be used to power absorption chillers using a thermodynamic process that allows water to be chilled and distributed for HVAC needs.

It uses water mixed with either ammonia or lithium bromide, with lithium bromide the more common choice because it is not toxic.

This mixture is pumped through the heat exchanger to the generator tank and the waste heat separates the lithium bromide and water.

The water gradually becomes vapour and rises to the top, where the condenser is located, and the lithium bromide sinks to the bottom and flows back to the absorber. The vapour goes through a cooling tower and becomes colder water again as the air pressure decreases. This water is then distributed to properties via pipes to use for heating.

What are the benefits of absorption cooling?

Individual air conditioning units for each building or home consume a lot of electricity on hot days, which can overload energy grids and contribute to the triggering of blackouts, to say nothing of the financial and environmental cost of the energy.

Absorption cooling, such as that seen in Spittelau’s use of waste heat in absorption systems, reportedly delivers CO2 savings of about 79% when compared to conventional building air conditioning systems, which could provide great energy saving tips for those looking to lower their bills.

The cooling is delivered to customers via district cooling pipelines with only minor efficiency losses. Additionally, customers no longer need their own cooling plants for the system, reducing maintenance costs.

A bunch of garbage outside a waste management facility

Waste management facilities can burn rubbish for absorption cooling and make CO2 savings of about 79% when compared to conventional building air conditioning systems (Image credit: Getty Images)

Is it available in the UK?

The global district cooling market size is projected to grow from £23billion in 2023 to £36.27billion by 2030, at a compound annual growth rate of 6.72% during the forecast period, according to Fortune Business Insights.

British homes are generally not designed to cope with heat for obvious reasons, but as temperatures creep upwards many of us will be looking at investing in air conditioning.

District cooling powered by absorption chillers fired by waste energy or geothermal energy could make sense in the UK as part of its push to reduce energy bills. 

Sam Webb

Sam is based in Coventry and has been a news reporter for nearly 20 years. His work has featured in the Mirror, The Sun, MailOnline, the Independent, and news outlets throughout the world.  As a copywriter, he has written for clients as diverse as Saint-Gobain, Michelin, Halfords Autocentre, Great British Heating, and Irwin Industrial Tools. During the pandemic, he converted a van into a mini-camper and is currently planning to convert his shed into an office and Star Wars shrine.