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Wind Energy

December 18, 2021
Paul Gipe

Another Long-Forgotten Wind Turbine--This Time on the Isle of Man

The research for an article on the history of early wind turbines took me down one fascinating rabbit hole after another. Previously, I mentioned Dimitri Stein and his Nordwind turbine on the Island of Neuwerk in the Wattensee. Another long-forgotten wind turbine I’d never heard of before was off the west coast of England on the Isle of Man.

Installed a decade after Stein’s Nordwind, the Isle of Man turbine was more modern in many respects and presaged wind turbines that would come decades later. The Isle of Man turbine—there’s no good shorthand for this machine—was connected to the grid, not to a remote diesel system. It also located the generator and gearbox at the top of the tower like modern machines instead of transmitting mechanical power to ground level as in the Nordwind turbine. And it drove an induction (asynchronous) generator like later wind turbines rather than a DC dynamo in the case of Nordwind or a synchronous alternator like that in the Smith-Putnam machine in Vermont.

The Isle of Man wind turbine was the most successful of the three experimental British wind turbines of the 1950s. It’s also the least well known. Why that is so, remains a mystery. I certainly had never heard of it. Many of the sources I’ve used in my research seldom ever mention it. And there’s little published record of it. Yet, the wind turbine was operated for The Isle of Man Electricity Authority and remained on site for at least five years, far longer than either the Enfield-Andreau pneumatic wind turbine or the John Brown turbine in the Orkneys. The fate of the latter two machines is well known. They either performed poorly or hardly at all.[1]

Installed in 1959 west of South Barrule, the 15.2-meter (50-foot) diameter wind turbine used three fixed-pitch blades upwind of the tower to drive the wind turbine at 100 kW at a wind speed of 18.3 m/s with a rotor speed of 75 rpm.[2]

The site at South Barrule had been identified by Britian’s Electrical Research Association (ERA) as a good location with an annual average wind speed of 10.1 m/s.[3] Where the turbine was actually installed is unclear.

One of the few sources we found on the turbine was a paper by D.E. Elliott titled simply Economic Wind Power.[4] Elliott says the site had a “moderate” wind regime, suggesting it was not located on the summit of the hill. Nevertheless, the turbine produced some 230,000-240,000 kWh per year when it was in full operation.[5] If true, such performance was exceptional for the day (1,250 kWh/m²/yr) and wouldn’t be seen again until the Danish wind revival of the 1980s was in full swing.

In comparison to the other two turbines in the British research program, the Isle of Man machine was crude. It used a fantail to orient the rotor upwind of the tower rather than a mechanical yaw system as in the John Brown turbine. It was ungainly. The rotor was mounted directly on an integrated gearbox, possibly a forerunner of American and some Danish designs 20 years later. There was no nacelle at all, unlike the streamlined nacelle, blades, and tower faring on the Andreau turbine. The blades were not cantilevered like that on the Andreau turbine or John Brown design. The Isle of Man turbine used struts and stays to brace the rotor not unlike that seen on Juul’s Gedser machine a few years earlier.

Like the Gedser turbine, the Isle of Man turbine used blades with constant chord. They were not tapered or twisted. Unlike the Gedser blades, the blades on the Isle of Man turbine were extruded out of aluminum.

The Isle of Man turbine was designed by Irwin and Partners of London, and the turbine was built by R. Smith of Crawley in Surrey.[6]

The designers opted specifically for two features intended to cut costs. They chose to use fixed-pitch blades to eliminate what they deemed the costly blade pitching mechanisms used in the John Brown and Andreau designs. They also chose a blade with a constant chord so they could use cheap extruded aluminum blades. The latter decision “led to far greater savings than originally expected.”[7]

Ironically, the designers cut corners further by recycling the 100 kW generator from the failed John Brown turbine on Orkney. Their economic modeling originally suggested a rotor of 13 meter diameter, but they opted for 15.2 meter diameter instead. They initially considered running the rotor downwind of the tower, but decided to “adopt the conventional upstream running position.”[8]

Like the earlier Smith-Putnam turbine, the Isle of Man design called for mounting the nacelle on a pintle rather than a turntable. This later proved to be a mistake.

If the brake or the gearbox failed, overspeed protection was provided by tip brakes not pitchable blade tips or tip flaps. These “were in essence a flat plate at the end of the blade, normally at right-angles to the axis of the blades but which, on the operation of an overspeed trip mechanism, automatically flung themselves outwards to create enough drag to bring the rotor down to a low tip speed/wind speed ratio."[9]

ERA later suggested a modification to use a solenoid operated fail-safe actuator, in the event the induction generator was disconnected from the island’s grid. In this way, “no time would be lost waiting for the overspeed mechanism to trip." This was a wise precaution that was learned the hard way many years later on American-designed wind turbines resorting to tip brakes.

This may have been the first use of tip brakes for overspeed control. Not surprisingly, the turbine suffered losses at low wind speeds estimated to be as much as 30 kW due to the drag of the tip brakes in their closed position. Similar losses were also seen later in American designs of the 1970s and 1980s, notably in Enertech and ESI turbines.

Though the tip brakes worked, researchers concluded that "alternative forms of aerodynamic braking would be worth pursuing." Yet there was no mention that the designers were aware of Danish work with pitchable blade tips, such as at Gedser. Pitchable blade tips are a much more aerodynamic approach to overspeed control than tip brakes.[10]

Stall regulation performed as expected. The turbine’s peak power of 120 kW occurred at a wind speed of 22.5 m/s. Average output was 25% of the rated capacity, better than expected from the wind tunnel tests.[11]

Testing found very little power ripple (+/-5%), justifying the decision to mount the rotor upwind of the tower.

The test turbine experienced winds of more than 36 m/s in the standstill position without damage, “but after protracted unsupervised running, the machine ultimately failed, apparently by tilting about the pintle shaft to such an extent that one of the blades contacted the tower.

In a post mortem on the project, Elliott noted that . . . the combination of windmills with water storage to provide a measure of "firm" power would enhance the value” of the wind turbine’s electricity, making it economic." Britain would ultimately develop several large pumped storage projects, though not for firming wind. Similarly, “a unit running independently to provide electricity and/or heat for isolated communities” would obviously be more attractive than as a part of the main network “and appears to warrant further research.”[12]

Unfortunately, by this time ERA’s wind power committee had been disbanded and the machine was scrapped sometime around 1964, the economic case weakened by the prospect of cheap nuclear power with its promise of low fuel costs."[13]

Wind research in Britain fell, like that in France, to the spectral lure of the atom. A perfect example of an institution confusing "promise with performance" and succumbing to the "too cheap to meter" dream with no evidence that nuclear power could deliver.

The report on the Isle of Man wind turbine concluded that "The concept of a constant speed, self-regulating, fixed-blade windmill appears to be a practical way of achieving a rugged low cost windmill” with a low overall cost of generation.[14] Of course, it would await the Danes a few years after Elliott’s report was published to accomplish this task with just such wind turbines.

[1] “Costa Head Experimental Turbine.” Accessed September 23, 2021.; see the cover of Golding, E.W. The Generation of Electricity by Wind Power. Reprinted by John Wiley & Sons 1976. London: E. & F.N. Spon, 1955.

[2] “Windmills of The Isle of Man.” Accessed August 28, 2021.; and Golding, E.W. The Generation of Electricity by Wind Power. Reprinted by John Wiley & Sons 1976. London: E. & F.N. Spon, 1955, p. 323.

[3] Golding, p. 158.

[4] Elliott, D.E. “Economic Wind Power.” Applied Energy 1 (1975) (1975): pp 167-197.

[5] Elliott, p. 195.

[6] Elliott, p. 191.

[7] Elliott, p. 169.

[8] Elliott, p. 188.

[9] Elliott, p. 191.

[10] Elliott, p. 196.

[11] Elliott, p. 193.

[12] Elliott, p. 196.

[13] Elliott, p. 194; and “New Scientist 1974 Isle-of-Man.” New Scientist, June 13, 1974.          

[14] Elliott, p. 197.

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