How a forgotten Scottish inventor gave the world air conditioning

But a certain Scottish invention that would have a global impact and go on to be visible to many of us even now as we go about our daily lives, would fall off the radar.

And instead, credit for inventing air conditioning would go to an American, overlooking entirely the Clydeside electrical engineer whose brilliant Thermotank revolutionised life at sea and on land.

While his other ingenious invention – the exotically named Punkah Louvre – would become commonplace but its Glasgow origins also long forgotten.

Now there are efforts to ensure the name of Glasgow’s forgotten pioneer, Alexander Stewart, is given its rightful place in the list of great Scottish inventions.

Cunard liners RMS Queen Elizabeth and RMS Queen Mary were both fitted with Alexander Stewart's innovative air conditioning system (Image: Contributed)

Researcher Ian Johnston, whose book about Alexander and his Thermotank will form the basis of a talk next month at Govan’s Fairfield Heritage centre, says his groundbreaking air conditioner has been overlooked for too long.

“It was one of these great inventions that happened on the Clyde that we don’t really know about,” he says.

“The device Alexander created, the Thermotank, was a massive hit and was hugely successful.”

The system he devised in 1898 was not unlike an early version of an air source heat pump, capable of ventilating and maintaining a constant temperature in a ship’s compartment irrespective of outside temperature.

Although the expression “air conditioning” did not come into use for many years, Ian says that’s precisely what his Thermotank did.

“It was the start of air conditioning and before long every major ship in the world was equipped with these devices.

“But if you look at history of air conditioning on Wikipedia, it tells you an American, Willis Carrier, invented it in 1902. That’s not strictly true: it was invented four years earlier than that by Alexander Stewart.”

Alexander Stewart was working for Clydebank-based James & George Thomson & Co in the late 19th century when he developed a system that would alter the nature of heating and ventilation at sea and lay the foundation for air conditioning.

Drawing office staff at J&G Thomson's yard in 1892, in front of HMS Ramillies (Image: Crown Copyright, National Records of Scotland)

The Thomson yard had built many of the vast, well-appointed passenger steamers of the age, among them the Inman Line steamers, the City of New York and the City of Paris, which were among the largest, fastest and most comfortable of their kind in the world.

But ventilation below decks relied on little more than a porthole and the limited air flow was provided by large trumpet-shaped ventilators on ship's decks which drew in air as the vessel moved forward.

As liners became grander and faster, passenger comfort was as important as speed, and crucial for ship operators seeking to stand out from the crowd.

Alexander would have been acutely aware of the aware of the discomfort that came with travelling at sea in poorly ventilated compartments and the inadequacies of the deck-mounted cowls, adds Ian.

A Thermotank air conditioning unit installed on warship HMS Commonwealth (Image: Contributed/Ian Johnston)

“At this time, mechanical means such as open fireplaces, hot water or steam pipes and radiators or electric heaters and stoves had many limitations. Heating and ventilation on board ship was thus rudimentary,” he explains.

“Alexander is working on great ocean liners and seeing first-hand how they are heated and cooled, how inadequate it is and thinks he can come up with something much better.”

His mechanical Thermotank system worked by drawing air in, circulating it around steam heated pipes to warm it or water filled pipes cooled by refrigeration plant to chill it.

Diagram of Thermotank unit designed to keep warships cool (Image: Contributed)

Not a million miles away from today’s air source heat pumps, it used fans to deliver the warm or cool air directly to a ship’s compartment via a network of trunking.

The result would be a constant temperature, irrespective of whether the ship was in the tropics or the chill of the North Atlantic.

Patented in 1898 – four years before American inventor Willis Carrier installed what is considered the first modern electrical air conditioning unit in a New York building – the Thermotank was revolutionary.

First fitted on board the Russian Volunteer Fleet vessel, Kostroma, it soon featured on two of the most famous liners in the world, RMS Lusitania and Mauretania, and all of White Star’s Olympic Class liners used it.

“This was the start of air conditioning,” insists Ian, who researched Stewart’s invention for a new book, Blowing Hot and Cold. “The system became a huge hit and every major ship in the world was equipped with these devices.”

As well as passenger and crew comfort, air conditioning protected ships’ cargoes from ‘ship sweat’, the condensation created when a vessel moved from a cold to hot climate.

And it would be invaluable as a means of cooling magazines in battleships, gunboats and torpedo destroyers where cordite and other high explosive ammunition for gunnery were at risk in below deck temperatures that could soar to 100 degrees Fahrenheit.

Alexander Stewart (right) inspects his first Thermotank unit on board Russian Volunteer Fleet vessel Kostroma in 1898 (Image: Contributed)

Although originally for ships, it would also become incorporated into buildings around the world helping shops, factories and offices to regulate their temperature.

Before long, Alexander and his two brothers had set up their own Thermotank business with huge manufacturing premises in Helen Street, Govan.

“By the 1930s and 40s there are Thermotank systems everywhere from South Africa to Toronto,” adds Ian.

A Thermotank system was even fitted in the Cabinet War Rooms at Westminster to keep politicians and military advisors comfortable during the Second World War – the trunking can clearly be seen in photographs of the historic rooms.

Temperature was regulated in the war cabinet rooms in Whitehall using the Thermotank system. The trunking network that distributed the air can be seen just below the ceiling (Image: Central Press/Getty Images)

But the decline of shipbuilding in the 1950s saw the beginning of a series of mergers that would eventually wipe out the Thermotank name.

“Today, there’s nothing at all left of the company in Glasgow, and it is part of Daikin Industries based in Osaka, Japan,” says Ian. “It is the largest manufacturer of air conditioners in the world, it employs 100,000 people worldwide.”

Demand for Daikin’s low-carbon heating and cooling solutions means it has recently seen its turnover grow by 20%, bringing it to 5.2 billion Euros.

“They probably don’t know the origin for their business is Clydebank,” adds Ian.

These days, anyone who has stood at a shop till or in any number of other large premises and looked up to see a network of trunking above their head will be looking at an air conditioning system which has its origins in Clydebank.

But that wasn’t Alexander’s only great invention.

In the early 1920s, he also gave the world the Punkah Louvre, the small overhead gadget that directs refreshing air into the compartments of the world’s planes and trains, and which millions of travellers will recognise.

Alexander Stewart's other invention was the Punkha Louvre (Image: Contributed)

His Punkah Louvres and Thermotank air conditioning featured in the Cunard liners Queen Mary and Queen Elizabeth, the French liner Normandie and dozens of other famous liners and prominent buildings.

Alexander’s invention made him and his brothers wealthy men. One nephew, Sir Ian Maxwell Stewart, became a leading Scottish industrialist who, with Sir Jackie Stewart and Sir Sean Connery, formed the Scottish International Educational Trust which continues to support some of the country’s brightest young people.

A cabin on board SS Chitral with Punkah Louvres in ceiling (Image: Fairfield Heritage)

Ian, who will present a talk on the Thermotank and Alexander’s inventions at Fairfield Heritage centre on Friday, 16 August, says Alexander is overdue proper recognition.

“We watched the decline of shipbuilding and all these industries on the Clyde and Glasgow and it’s almost as if we’re embarrassed and ashamed that we let them go,” he says.

“We need to look back and celebrate these huge achievements.”

The dining room of SS Mongolia with its ceiling air conditioning (Image: Fairfield Heritage)

As well as the talk and his book, Ian has created a Wikipedia page that tells the story of Thermotank and the foundations of air conditioning.

“Glasgow had fantastic industry and an engineering past of breakthroughs, and this is part of that story,” he adds.

“We need to remind ourselves of this history.”

Tickets for Ian Johnston’s talk at Fairfield Heritage are available here