Palmer Putnam to Herman Drees Letter Reveals Emphasis on Swept Area

By Paul Gipe

Wally Thompson forwarded to me some fascinating correspondence from Palmer Putnam to Herman Drees of Pinson Cycloturbine fame.

Thompson is an old wind hand who was a co-founder with Rick Katzenberg of Natural Power in 1974 which built wind monitoring and controls. (I used Natural Power’s wind-run recorders in a project I did for DOE in the late 1970s. See Pennsylvania Adopt An Anemometer Program 1980.)

Putnam was alerted to Drees’ work with Pinson by Putnam’s colleague Richard Heckscher who also worked on the Smith-Putnam project.

Of significance, is Putnam’s request for performance data “relative to swept area.” This request shows Putnam’s grasp of the essential design characteristic of a wind turbine. While this may seem intuitive today, especially to European wind engineers, this wasn’t always so on this side of the Atlantic.

Early Danish designers of the modern era and their German counterparts often reported progress in terms relative to swept area. Unfortunately, it would be decades before this concept was more readily adopted here. During the early days in North America, there was an overriding emphasis on rated power. This was largely due to tax subsidies and the competition for who had the highest power rating, regardless of swept area.

For the original document see Palmer Putnam – Herman M. Drees Correspondence 1979.

Herman M. Drees, President
Pinson Energy Corp.
Box 7
Marstons Mills, MA 02648

Dear Mr. Drees:

12 November 1979

J. G. Richard Heckscher has written me of his serendipidous [sic] visit to your offices the other day and I’ve also received, with your card, three copies of your Fact Sheet on your CYCLOTURBINE.

Vertical axis configurations have always appealed to me and your cyclicly-pitched three-bladed solution is particularly interesting . May I ask if you have measured the efficiency of extraction over the area swept, compared with the theoretical maximum? And the power extracted per pound of rotating structure?

Although I’m no longer active in wind power I would appreciate receiving word of any test results you feel free to release.

With all good wishes.


Palmer Putnam