79th Anniversary of First Wind Turbine Interconnection with the Grid in North America

By Paul Gipe

On this date in 1941 an ungainly wind turbine atop Vermont’s Grandpa’s Knob fed electricity into the lines of Central Vermont Public Service Company. This was the first time in North America that a wind turbine fed electricity into the grid. Until then wind turbines had been used solely to charge batteries at remote homesteads in Canada and the United States.

It was as momentous an event as the wind turbine was a giant of pre-war engineering and American manufacturing prowess.

The story of the turbine’s creation—and demise—is told in detail by one of the chief protagonists, Palmer Putnam, in his book Power from the Wind. The 53-meter (175-foot) diameter, two-blade wind turbine drove a 1,250-kW synchronous generator like that used by electric utilities in conventional power plants. To design, build, and operate the wind turbine from scratch—without any prior experience in wind energy—Putnam and the team organized by S. Morgan Smith Company in York, Pennsylvania, had to overcome numerous technical and logistical problems. That they succeeded at all is a testament to their ingenuity and perseverance.

However, as wind engineers Marc Rapin and Jean-Marc Noël note, the flapping rotor and its heavy, complex hinges were not well adapted to the rigors of  commercial usage. In 1943 a blade bearing failed, causing the turbine to be shut down for two years because of wartime shortage of materials. Upon inspection, the blade spars were found to be undersized for the loads, so doubling plates were welded in place. Welding of heavily stressed components is often problematic, and in retrospect this probably was unwise. The rotor was then locked in place for the duration of the war. The turbine was returned to service in 1945, and cracks were soon found in the blade root at the strengthening welds. Operation continued in hopes of completing the test program. The Smith-Putnam turbine then operated continuously for several weeks until late March 1945 when the repair weld failed and the turbine threw a blade, ending the program. It was three decades before anyone attempted a wind turbine of this size again.

While a remarkable achievement for its day, the Smith-Putnam turbine was not the first wind turbine to feed electricity into a utility network. In 1919 the utility serving the area north of Copenhagen installed a wind turbine at Buddinge, Denmark and connected it to its lines—a first worldwide, a full two decades before the Smith-Putnam machine in Vermont. The Danish utility had just recently introduced alternating current (AC) for its distribution system.