Feed Laws

Large Wind Turbines

April 16, 1998
Paul Gipe

Zond Claims Questioned on Z16 at Waverly Light and Power


Note: The following material describes an incident that happened in 1993. This note was originally posted to Glenn Cannon presented a paper on the performance of the Z16 at the AWEA conference in Bakersfield in May, 1998. This is a cautionary tale about inflated power curves and consultants who should have been paying attention.

On 14 June 1993 Glenn Cannon announced in Cedar Falls, Iowa that Zond had won a competitive bid to install a wind turbine for Waverly Light and Power. Glenn's presentation included a summary of the bids by Wind World/Minnesota Wind Power, Zond, Atlantic Orient, and Windway Technologies (used Wind-Matics).

According to Glenn's summary, Zond's bid offered the least cost of energy, $0.0927/kWh, while Wind World/Minnesota Wind Power offered $0.1181/kWh. Zond's winning bid was more than one-fourth less than Wind World's bid.

However, Glenn's summary also included installed cost and projected net generation. The cost of energy is largely determined by installed cost and net generation. Boost net generation relative to installed cost and the cost of energy declines. Or, boost net generation and you can charge more for your turbine relative to the cost of energy.

Zond's Z16 was bid installed at $129,000 or $1,350/kW. Wind World bid $143,000 or $1,000/kW.

Glenn's summary showed that an 80 kW Z16 (a uprated Vestas V15) would produce nearly as much as a 120 kW, 21-meter diameter Wind World. This oddity was privately called to Waverly Light and Power's attention with the suggestion that the bids be reopened. Waverly declined to do so but did ask for a clarification from Zond.

Waverly's energy projections were derived from power curves submitted by Zond as part of Zond's bid. Zond at first insisted that the projections from the power curve were correct and that, indeed, the turbine could produce this much energy. At the time, Zond was operating hundreds of the Vestas V15 and hundreds of later derivatives. The power curves for these turbines were well known and widely available.

However, Waverly insisted that there may be an error in Zond's Z16 power curve. Zond eventually relented and concluded that, yes, there was a problem and they would correct the power curve. The corrected power curve resulted in substantially lower energy estimates.

Waverly then renegotiated the bid with Zond to lower the installed cost to that reflected in their original bid. That is, they renegotiated the installed cost to a more reasonable sum in light of the inflated energy projection.

In the final report for the project 13 January 1995 Waverly Light and Power continued to insist that Zond's Z16 was selected because it proposed the lowest cost of energy. Waverly also noted that Zond had "limited operating experience" with the blades used on the Z16 and that an "accurate turbine power curve had not been measured for this turbine. . . To account for the lack of an accurate measured power curve, a conservative estimate was made based on theoretical calculations and preliminary test data. This estimate was used as the basis for negotiations with Zond on the final turbine cost."

To summarize, Zond won the bid using an erroneous power curve and had to cut the price of its turbine so that all parties could save face and avoid re-opening the bids.

Zond's inflated energy projection was detected by someone without an engineering degree, and without the aid of a computer. The error and its relative amount were calculated with a simple back-of-the-envelope technique used by nearly everyone working in the field of wind energy.

My apologies to Dan Juhl and Wind World for not making this information available at the time.

My thanks to Glenn Cannon and Waverly Light and Power for being so forthright. Unlike other companies and institutes in the wind energy and eletric power field, Glenn has always been prompt in sharing data on the performance of his wind project.

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