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Rejected Wind Turbines

We investigated numerous turbines, and decided to run some tests.

AIR-403

We liked the AIR-403 from Southwest Windpower (SWWP), because of the high power output for its size (rated at 400 watts), and the ability to throw a “stop” switch and greatly slow the unit. Unfortunately we found the machine to be unacceptably noisy, and there were stirrings of a neighborhood rebellion.

As well, we placed a couple AIR-403’s several feet back on some south-facing roof dormers for architectural reasons—only to see the dramatic results of turbulent air. The turbines swung wildly around in the “dirty” air. It was obvious that because of its loud sound the AIR-403 would not work in a residential neighborhood. It was also obvious that regardless of the turbine we used we needed to make sure it was located in a zone of smooth airflow.

A much better location was identified on the west main roof of the house, which placed our prospective turbines in smooth air.

AMPAIR

With smooth air in mind we next tested the Ampair Pacific 100 generator, considered to be exceptionally quiet and ruggedly built.



This turbine proved to be much more quiet than the AIR-403, though not very powerful at a rated 100 watts, and without the ability to significantly slow the turbine in high winds if we wished.

After some weeks of testing it was felt that the Ampair was still not quite quiet enough for this neighborhood. We also found that the vibration from the turbine into the structure was unacceptable, and sought to rework the mounting system.

AIR-X

After hearing about the new AIR-X from SouthWest Wind Power, we decided to try this unit. We were encouraged by the SWWP web site, and the suggestion of a SWWP technician that the AIR-X was substantially more quiet than the AIR-403, which we had tried earlier. At low to moderate wind speeds the unit seemed as noisy as the AIR-403. We had heard that the noisy high-speed “flutter” had been eliminated from this unit, but we ruled this machine out immediately because of a loud "swishing-whooshing" sound heard throughout the neighborhood. In a residential setting this unit was unacceptably loud, even before we reached higher-winds. It is far from the "neighbor friendly" that SWWP advertises, and sounds rather like an electric "weed-eater."

RUTLAND 503

In our search for a quiet turbine we decided to run a couple Rutland 503 turbines as "placeholders" on the poles until we could find a quiet and more powerful machine.



The Rutland 503 is a small marine turbine that produces very little power (maximum of 50-60 watts in high winds, and we saw around 15 watts in the modest summer winds). These units are exceptionally quiet, though they still reminded us of the vibration issue (see the section on wind turbine mounts).

PROVEN WT600

We continued to look for a more powerful wind turbine that was quiet. After reading an article titled "Choosing a Wind Generator" in the August/September Home Power Magazine, and examining company literature we were encouraged. This unit, the Proven WT600, produces approximately 600 watts at a little over 22mph, and would have harvested significant energy at this location.



We heard that the machine was heavy and solidly built. We also noted that the turbine turned more slowly than many other units, which suggested a long life and more quiet operation. Since the sound level of turbines at this residential site was very important we were encouraged.

The Proven literature describes the sound of this turbine, saying "The only sound produced is the quiet swish of the blades turning in the wind. To give an idea of this sound it is easily drowned by a car passing in the distance." We were getting excited about this machine, and expected that the oceanfront location would mask much of whatever sound we would hear. After all, the ocean waves are far more loud than the sound of a distant passing car!

We eagerly awaited the arrival of the units, and were pleased that they arrived ahead of schedule. The units did seem well-constructed, and were quite heavy. It took considerable effort to mount the turbines high on the poles, though the process went fairly smoothly. The industrial-strength control box was wired into our system, and we were ready to see how the first unit performed.



The electrical brake (which works very well) was released, and our enthusiasm was suddenly dampened as the turbine started making a noise we were surprised to hear. There were suddenly several sad faces.

We set out to attempt to find out what might be wrong:

Was the system put together correctly? We think so, as a careful examination of the installation looked good.

Was the unit producing the expected power at a given wind speed? Yes, we seemed to be on the power curve, as when the wind popped up to the upper teens we measured over 300 watts.

Was the noise related to a specific wind direction, possibly suggesting that the shape of the roof or turbulence might be causing the noise? The South turbine (the unit that had been fully installed and wired) made the same sound, from two almost opposite directions, the SSW, the cleanest flow onto the unit, and from the N, where we might expect more turbulence.

Was the noise at a specific wind speed? We noticed that the noise could just be heard at around 8mph, grew to be unacceptable 40' away at about 10-12mph, and became louder into the teens. Those on-site when the unit was into the low 20's turned off the turbine with the brake switch to avoid neighborhood complaints.

Was the noise from the wind whistling through the blade spring components? We taped all these components to eliminate air gaps. No change.

We positioned the lift machine to attempt to locate where the noise was coming from, and it was clearly originating from the outer portion of the blades. Interestingly the sound is most loud directly upwind and directly downwind of the turbine. If the blades are edge-on to the listener there is very little sound.

We consulted with the manufacturer, and lightly sanded small imperfections in the trailing edge of the blades. No change.

We applied electrical tape around the outer trailing edge of the blades. No change until the tape peeled off, making its own noise.

We removed the set of blades, and mounted the set from the second turbine. No change.

We adjusted the spring tension on the blades. No change.

The suggestion was made to try the second machine, which was not wired. We felt that by this time, though, we had expended considerable time and money (the lift machine alone is quite costly per day), and we had tried almost everything. We knew that the machine was on the power curve, that the noise was from the blades, that we heard it from multiple directions, that we had used two sets of blades, and so forth.

Here is a video/audio clip of the Proven WT600 wind turbine we installed. This clip was taken at a wind speed of about 10mph. The warbling, higher-pitched sound you hear gives you an idea of what we heard (though it is louder in real-life).

This was to be an installation of a system that we expected to work. We didn't have a controlled test environment and sound-testing equipment, so we can't publish specific sound measurement numbers. Ultimately this is a subjective evaluation, based on the experience of installing and listening to the WT600.

It is possible that there is a defect in both sets of the blades we tried, or that there is some additional testing and experimentation we could do to learn more.

Based on our experience with the Proven WT600 our opinion is that this turbine is too loud for a residential area. Based on what we had read we expected otherwise.

We were ultimately able to return the Proven turbines to a U.S. distributor, less significant expenses for crating and shipping both ways, and a distributor fee to make the units in "like new condition."

We encourage readers to listen to any wind turbine they are contemplating installing, or at least to have firsthand information from a non-interested party. We wish we had been able to listen to the WT600 first, but were told that the nearest installed unit was off the coast of Nova Scotia. That's why we depended on what we read.

It is the installers opinion that the manufacturer should be more conservative in the claims they make (in this case regarding noise), and in particular should be more responsive to customer problems.

RUTLAND 913

We next decided to install Rutland 913 turbines, as we had heard that these units were very quiet. Though the 913's were small machines we felt that they might be the largest turbines we could currently use at this site that were not unacceptably loud.

We were pleased with how quiet the 913's were.



We were soon to experience a major defect in the Rutland 913's. On the morning of December 27, 2002 we had one of our many Oregon coast winter storms. The Rutlands violently flew apart, scattering parts for many blocks and doing major damage to our PV array and the roof.

The winds we experienced were not unusual for the Oregon coast or notably strong. Our weather instrumentation recorded winds in the 40 MPH range, with gusts in the 60 MPH range. We experienced a peak gust of 63 MPH around the time the machines came apart, and a peak gust of 68 MPH after the machines had disintegrated.

The Rutland units, like any reputable wind turbine, are designed to take winds over 90 MPH, at least for a short period. The winds we experienced were reasonably lower than this, and we are puzzled as to why the Rutland's failed. At this time we are engaging in a dialogue with the manufacturer, and we will report on our findings.

SUMMARY

All the wind turbines were tested under load (connected to a battery system), and most experienced a range of wind conditions. While we found some of the units, especially the AIR-403, AIR-X, and Proven WT600 to be unacceptably loud in this location we feel that they have their place—but not in residential neighborhoods!

We hope that Southwest Windpower, Proven, Marlec/Rutland and other wind turbine manufacturers, put more of their resources into evolving solidly built units that are truly "neighbor friendly." This turbine must be reasonably quiet and solidly built. We believe that such a turbine would be much in demand, and could allow more wind machines to sprout in residential neighborhoods.

Interestingly the three turbines we have found to be most quiet, the Ampair Pacific 100, Rutland 503, and Rutland 913 all have six broad blades with stubby tips. We're not wind turbine designers, but we can't help wondering what a larger, well-constructed, many-bladed design could yield.

At this point we have tested 6 different wind turbines. None of these units meets our criteria for a quiet and well-constructed unit that provides more than just a trickle of power. We have decided that there is currently no wind turbine available that will work in this location, and have suspended our wind experiments for now.