In a large hall on the outskirts of Vienna, shiny pipes carry treated wastewater through three giant heat pumps, part of Austria's drive to reduce carbon emissions and its dependence on Russian gas, with more and more European cities eyeing this alternative. The plant - billed as Europe's most powerful one - is churning out district heat to up to 56,000 Vienna households, with operator Wien Energie planning to double its capacity to 112,000 households by 2027. "It is very clear that we have to restructure our energy system to become independent of fossil fuels or of different individual countries," Wien Energie manager Linda Kirchberger told AFP. Heat pumps work along the same principle as refrigerators, only it is the heat that is sought and not the cold. Household heat pumps have been enjoying surging interest, but they can also be implemented on a larger scale for city heating systems. Kirchberger said the plant was garnering a lot of interest from energy suppliers in other European cities, which are likewise in the process of installing pumps that extract the heat found in wastewater and use it to heat households. The Vienna heat pumps - which are fed by electricity from a nearby hydropower plant - are next to a sewage treatment facility. Since December, the steadily flowing stream of treated water from that facility is channeled through the pumps. They extract six degrees Celsius (11 degrees Fahrenheit) of heat from it before it flows back out and into the Danube. The lower temperature of water discharged into the river is an added advantage given the globe's warming waters, according to expert Florian Kretschmer. The extracted heat, in turn, is chanelled to Wien Energie customers in the form of hot water over a vast network of pipes for district heating, which with 1,300 kilometers (800 miles) is Europe's third largest, according to the company. "The technology itself (to extract heat) is nothing... |