Those giant power station towers are breathing out mostly water vapour
The huge waisted towers beside power stations look like smokestacks, and many people assume they pour out fumes. What rises from them is almost entirely water vapour. Their job is to shed waste heat: water that cooled the steam from a turbine trickles down inside, some of it evaporates, and the rest returns chilled for reuse.
The idea grew out of 19th-century steam engines. Condensers use cool water to turn exhausted steam back into liquid, which lowers back pressure, saves fuel, raises power and recycles boiler water. On ships water is endless, but on land a condenser needs a steady supply, so by around 1900 plants without enough water began recycling it by evaporation, using cooling ponds where land was plentiful and towers in cramped cities. A 1911 American textbook pictured one as a squat, widened chimney in which water dribbled down over wooden slats or wire mesh.
Two Dutch engineers, Frederik van Iterson and Gerard Kuypers, patented the familiar curved shape, a hyperboloid, on 16 August 1916. A year later the first reinforced concrete version went up at a Dutch State Mines site in Heerlen, and Britain's first followed at a Liverpool power station in 1924, both serving coal-fired plants. Such towers can reach 200 metres tall and 100 across; the tallest, at the Pingshan II station in Huaibei, China, stands 210 metres. Most cooling towers, though, are modest boxes on rooftops rejecting heat from office air conditioning.
The water numbers are striking. A typical 700 megawatt thermal coal plant with a tower circulates about 71,600 cubic metres an hour and tops up roughly 5 percent of that, around a cubic metre every second. Without a tower, drawing river or lake water once through, it would need about 100,000 cubic metres an hour. Big intakes trap millions of fish and larvae on their screens each year, and returning hot water can overheat a river and encourage pests like zebra mussels. A tower instead releases heat into the air, where wind spreads it widely.
Engineers keep looking for savings. In 2021 researchers showed that plume vapour could be charged with an ion beam and caught on an oppositely charged mesh, yielding water clean enough to meet American drinking standards.
Source: Cooling tower
