Answers to your questions about gardening, energy, homesteading and other sustainable living topics.
I've heard that most vertical axis wind turbines don't produce nearly as much power as the horizontal axis models, but there's lots of information out right now about the new Windspire. Is there any reason to think it performs better than other vertical turbines?
I contacted the manufacturer of the Windspire to find out why they felt their turbine might perform better than other vertical-axis wind turbines (VAWTs). They cited two key reasons:
1) The Windspire is designed as a complete system — rotor, generator, inverter, even structure all tied into one package. “Every component is optimized so that the overall system efficiency can be maximized.”
2) The Windspire has a larger swept area than other VAWTs — the Windspire 1.2-kilowatt (kW) turbine has 80 square feet of swept area.
Their reasoning is sound. Balancing system components could definitely create higher efficiency than using unmatched parts. And swept area, which is the effective size of the wind energy “collector,” is key to higher performance for any wind turbine, whether it’s a VAWT or a HAWT (horizontal axis).
However, across the small wind industry, performance of small wind turbines in the field has often fallen far short of optimistic projected performance figures from manufacturers. Engineering innovations always create lots of excitement and expectations, whereas independent standardized testing of wind turbines is the answer to providing real performance data — something that has long been at the top of the wish list for wind aficionados.
The lack of independent testing and certification of small wind turbine systems has been a barrier to the development of the small wind market. To address this need, the National Renewable Energy Laboratory and U.S. Department of Energy (NREL/DOE) Independent Testing project was started. The testing criteria follow standards set out by the International Electrotechnical Commission (IEC) and the American Wind Energy Association (AWEA). The testing covers areas of safety and function, power performance, noise, power quality and durability.
To the credit of Mariah Power, the company participated through a competitive solicitation process to have their 1.2 kW Windspire Giromill VAWT tested through NREL’s testing program. While the final results are not in and a full analysis report has not been posted, check out the preliminary results.
The final reports and documentation will eventually include explanations of the data and additional supporting data. However, the posted preliminary results show that the turbine did not perform at anticipated levels. A number of factors could have influenced the outcome, so I asked Mike Hess, the CEO of Mariah Power about the results. He attributed the poor results to a bad inverter, and also admitted “there have been lots of failures along the way that we have learned from, and that experience cannot be ignored.”
Choosing to participate in NREL’s rigorous testing is a great testament to the confidence Mariah Power has in their product and their sincere desire to provide accurate statistics about its performance. While Mariah Power may be disappointed with their initial test results, in light of their good faith effort to document their product and their honest assessment of their turbine’s performance history, I would wait and see what happens next before drawing any firm conclusions.
— Linda Pinkham, former managing editor of Home Power