Correctly addressed, they are natural-draught, hyperboloid cooling towers. All the ones in these photographs date from the 1960s, when they were built to cool the superheated steam that drove the turbines in Britain’s colossal coal-fired power stations. Almost a third have already been demolished; within a generation, it is unlikely there will be any left.

Thousands of people came out at dawn last August to witness the demolition of Didcot’s three remaining cooling towers. Film footage taken from a safe distance shows them sinking down into the horizon, like ships descending into the sea, the sound of the explosion lagging behind the sight of the blast.

At the death, they fold like pastry, the disruption causing nearby pylons’ power lines to sag and sway. Plumes of concrete dust rise out of their throats, before drifting away in the watercolour grey sky above the Oxfordshire countryside. Only 16 years previously, they had been voted the third worst eyesore in Britain.

Standing 290ft wide at the base and 375ft tall, which is slightly higher than St Paul’s Cathedral, each standard hyperboloid cooling tower is the perfect exemplar of “form follows function”.

They work on the principle of evaporative cooling. Hot water from the power station is pumped into the cooling tower at a height of about 30ft, where it is sprayed through a series of nozzles (much like an office sprinkler system) on to a layer of dense latticework, which is called the fill. The hot water coats this honeycomb, trickling downwards.

Fiddler’s Ferry power station in Warrington, Cheshire, is due to be decommissioned
Fiddler’s Ferry power station in Warrington, Cheshire, is due to be decommissioned © Michael Collins

The base of the cooling tower sits on a plinth of 25ft-high concrete struts, which forms a massive natural draught intake. The warm air produced by the hot water rises inside the cooling tower, drawing in cold air from outside, which cools the water coating the fill. The inwardly sloping curve of the tower narrows to a diameter almost half the size of its base, arresting most of the vapour; only up to 5 per cent is lost to evaporation. The term for these clouds of vapour, which are erroneously presumed to be steam (or even smoke), is drift.

Hyperboloid cooling towers were invented in 1916 by Dutch engineer Frederik van Iterson. The first two companies that Van Iterson approached to construct his invention declined the commission, but he persevered and, working in collaboration with civil engineer Gerard Kuypers, saw his design vindicated.

Previously, cooling towers had been built of wood or steel — an unsatisfactory arrangement due to the risk of fire and problems with rot and rust. They were either straightforwardly cylindrical chimneys or shaped like the top half of a bottle. Van Iterson was an expert in reinforced concrete, or “concreted iron”, as it was dubbed back then. He chose the hyperboloid because it offered the greatest structural strength; the ratio of shell diameter to wall thickness is less than that of an egg.

The story goes that Van Iterson demonstrated the hyperboloid’s shape by twisting a cat’s cradle of yarns between his hands. To prove the structure’s strength, he made a model out of thin sheets of iron; the results exceeded expectations.

However, when it came to the first full-size hyperboloid cooling tower, it was said of Van Iterson that his plans were not “based on a calculation”, rather, “dimensions and reinforcement are intuitive and based on constructive discretion as an estimate, taking especially into account the influence of wind”. The Netherlands became known as the land of the cooling towers.

In 1924, Britain’s first hyperboloid cooling towers were built at Lister Drive Power Station in Liverpool. They were 120ft high, 100ft wide at the base, narrowing to 33ft towards the top. More flamboyantly shaped than their modern counterparts, they had the profile of a carafe, including a pronounced lip running along the rim. The maximum thickness of their concrete shell was 7½in, and at its thinnest, only 4½in.

When they were demolished in 1972, one of the two engineers in charge commented: “What impressed me most was the way each tower fell with a 20-degree twist, vortexing into itself for all the world like bath water going down the plug.” To which his colleague added: “They would have been good for years to come.”

The future of West Burton, near Gainsborough, Lincolnshire, is under review
The future of West Burton, near Gainsborough, Lincolnshire, is under review © Michael Collins

The early versions were built from the ground up on wooden scaffolding, following the specifications of Van Iterson’s prototype. A rival successfully designed a close alternative, the “cone toroid”; rather than one continuous structure, it was fabricated by joining two cones together with a ring.

The cone toroid was purportedly devised as a means of reducing costs, although a contrasting explanation suggested that the primary purpose was to avoid patent infringement. It was not until four decades later, in the middle of the construction boom for a new generation of power stations, christened “Hinton’s Heavies” after the Central Electricity Generating Board chairman, that the soundness of Van Iterson’s calculations — and those of his competitors — was rudely re-examined.

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On Monday November 1 1965 in West Yorkshire, three of Ferrybridge “C” Power Station’s eight cooling towers collapsed in 80mph winds. A “horrified” CEGB realised the original specifications had been taken for granted and that there were “other towers throughout the country in a much weaker state”, prompting it to stipulate thicker shells and double reinforcement. Significantly or not, the cooling towers at Ferrybridge were cone toroids rather than hyperboloids.

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From the start, the prospect of cooling towers looming over the countryside was viewed with consternation, earning the condemnation of bishops and eliciting such pejoratives as “Cinderella’s ugly sisters”. Although the Royal Fine Art Commission advised on the construction of power stations, the architecture budget was less than 2 per cent of the total investment.

As their size increased, so did the level of public disapproval. No longer able to mollify this rising discontent with ornamentation and flower beds, the CEGB brought in landscape architects to mitigate the presence of these behemoths with earthworks and woods. Seeking to “simplify and clarify the elemental geometry”, the architects arranged the cooling towers in diamond patterns and painted them in different colours.

Ratcliffe-on-Soar power station on Nottinghamshire is still in operation
Ratcliffe-on-Soar power station on Nottinghamshire is still in operation © Michael Collins

The highest point in a coal-fired power station is the incinerator chimney, otherwise called the stack. The panoramic view from the stack at Cottam Power Station overlooks the cooling towers and the landscape beyond. Behind them is the black wound of the coal stock ground. Operating at full capacity, the power station burnt five million tons of coal a year.

Cottam was built here because of the proximity of the Nottinghamshire coalfield and the river Trent, which winds past it to the east, supplying its water. Coal was once the future. Just over 50 years after its construction, Cottam ceased functioning at the end of September 2019.

Some of the plant’s engineers who helped me when I was photographing were based there all their working lives. When the plant was running, a single cooling tower could handle more than six million gallons of water per hour. As the cooled water poured down from the fill, it cascaded in a ring around the perimeter of the base, creating a 25ft waterfall. Now Van Iterson’s “wall of flowing shape” stands silent. What is to happen to the natural-draught, hyperboloid cooling towers? Not a single one is listed. Surely they deserve more.

michaelcollinsphotography.com

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Our carbon-intensive industrial heritage should be preserved / From Jonathan Aylen Salford, M28, UK

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