Earlier this month, I arranged to visit the wind research teams at Sandia National Lab and the National Renewable Energy Lab’s National Wind Technology Center, both of which are relatively nearby here in the southern Rockies.  I’ve been following the work of many of these researchers for the past year or so—it was central to my 2012 Renewable Energy World conference paper and presentation on efforts to quiet turbines—and was very interested in learning more about their past, current, and future studies.  

In particular, the Sandia team has recently built a Scaled Wind Farm Testing (SWiFT) facility, at which they’ll be studying wake interactions between turbines, and they’ve long been on the forefront of developing new materials and experimental active systems to reduce load strains caused by inflow turbulence.  They’re also leading the development longer blades, which may have important noise implications. Their most exciting forward-looking project is a 5-year effort to re-activate development of vertical axis turbines, with the goal of moving toward 5-10MW scale vertical axis turbines for use offshore (this will be a 10-20 year project, if the first phase shows promise).  Meanwhile, at NREL’s NWTC, lots of research has looked at the pinpointing the sources of sound on turbine blades, as well as advanced modeling of sound propagation in various atmospheric conditions.  Researchers there have quantified the power-production trade-offs caused by wake interactions within wind farms, and are on the leading edge of new technology that might allow individual turbines to monitor incoming air flows and adapt their operations to minimize loads and noise.  All of this research has intrigued me, because of the likely role of wakes and atmospheric turbulence in wind turbine noise levels, and in creating some of the more intrusive sound qualities that neighbors find hard to live with.  My hope was to sit down with these researchers and learn more about their work, as well as draw on their experience to see whether they thought the turbulence factors they study to reduce stress on turbines may indeed also have an effect on the sounds.  

As it turns out, they were also intrigued by such a dialogue, and both labs asked me to present their teams with a seminar on what I’ve been learning about community responses to turbine sound.  Much of what I shared was new to them, and we had some great discussions.  One of the central take-aways from both teams was that very little research has really looked at the acoustic effects of inflow turbulence, and there was universal agreement that this is an important area for future study (as a start, the SWiFT facility will incorporate some acoustic measurements).  Many of them were especially interested in the varying sound quality of turbines, and the ways that this may trigger negative responses among neighbors; there was much speculation about the potential to identify the conditions that create the troublesome knocking, banging, thumping sounds, and perhaps adapt turbine operations to minimize or eliminate them.  As I’ve long found in my interactions with academic and agency researchers, there was an easy openness and curiosity in both rooms, with many questions tossed around, and an excitement about studies they hadn’t seen before. 

Read or download my presentation: The possible role of turbine, wake and shear effects on community response to wind farm noise  (This is the “director’s cut,” including a few slides deleted for length from the final version, along with some additional slides from the REW conference presentation that cover related topics) 

Community Response to Wind Farm Noise: The possible role of turbulence, shear, and wake effects by jimcummings

Planners have long recognized what they call a “demographic shift” in areas near new or expanded airports and highways: in the years after construction of the new noise source, some proportion of nearby residents move away, seeking a return of the quiet they desire.  Since about half the population is very noise tolerant, buyers who don’t mind the moderate noise are usually found. Sometimes homes must sell at a discount, and in other cases, the price isn’t significantly affected; rarely, homes with especially severe noise exposures cannot find a buyer at all.

An article in South Coast Today gives a sense of how this is playing out in Falmouth and Fairhaven, where dozens of families within a half mile or so of turbines have been struggling with noise.  As is often the case, the takeaways are ambiguous.  Two residents near the Fairhaven turbines are quoted, both of whom are reluctantly moving from their homes.  One, who’s been sleeping in his living room because the noise in the bedroom keeps him awake, has found a buyer who’s paying just 7% below his asking price.  The other, whose kids and their mom have already moved away because their 8-year old was having trouble sleeping, had his house on the market at a low-end price, and after “watching buyers come by, look at the turbines and drive away” for several months, he’s now hoping to find renters.  Likewise, a local realtor speaks of a house around a half mile from the turbines that’s been on the market for two years: “They ask about the noise, they ask about the flicker, and then they don’t put in an offer,” she says, noting that the asking price has dropped from $389,000 to $244,900.

In Falmouth, realtors speak about similar troubles finding buyers, with some homes being passed from realtor to realtor as they attempt to sell.  However, the director of Falmouth’s Assessor’s Office says that homes near the turbines have sold at “close to or more than” the assessed value.  At the end of last year, a couple that was one of the closest neighbors to the one privately-owned turbine in Falmouth abandoned the home they designed and built, and started over with a cheap fixer-upper; I have not heard whether it has been sold or not.

In the first town-wide vote on the question of what to do about noise issues around two town-owned turbines, Falmouth voters overwhelmingly defeated a measure that would have authorized the Selectmen to continue on their preferred path of dismantling the turbines.  The proposal carried a likely pricetag of about $800 per household, spread over ten years, largely to pay back loans and renewable energy credits that the town received in advance in order to buy and install the turbines.  The measure fell by a 2-1 margin, with about 40% of the town’s registered voters turning out.

Board of Selectmen Chairman Kevin Murphy said that the board will now begin looking at other ways to try to address the long-simmering dispute.  About 40 households have formally filed complaints, representing 15-20% of the homes within about a half mile. Since noise monitoring showed some violations of state noise limits, the two turbines do not run at night, so operate at a loss to the town, though they still produce carbon-free electricity for use at the town’s wastewater treatment plant.

For more on the Falmouth vote, see coverage in the Cape Cod Times and from the AP.
UPDATE, 5/25/13: Three neighbors respond to the vote in this local article.
UPDATE, 6/5/13: Neighbors emphasize that the vote was about funding the previous decision of the Selectmen to take the turbines down (not about whether the turbines should operate), and that the problems will need to be addressed by the incoming Board of Selectmen and/or the Board of Health.  They also say the state should step up with some financial help or forgiveness to lessen the burden on town taxpayers.
UPDATE, 7/5/13: The Board of Selectmen have begun discussing their options for resolving the turbine issue.  See local coverage of their first public discussion here and here. 

Across the bay in Fairhaven, the first results of noise testing were announced at a Board of Health meeting, marking a turning point not unlike one Falmouth encountered about a year ago.  Monitoring by the state Department of Environmental Protection has found that the two turbines in Fairhaven exceeded state noise limits in 5 of the 24 testing periods analyzed so far (more testing in varying wind conditions is ongoing).  All of the violations ranged from 0.7-1.5dB over the limit of 10dB above background ambient conditions.  Two to three decibels is considered the threshold of the human ear being able to hear an audible difference, so these noise levels are not perceptibly louder than sound just below the 10dB threshold; however, we once again see evidence that the 10dB-over-ambient standard is pushing the tolerance of neighbors.  As Fairhaven board of Selectman Chairman Charlie Murphy said, “Before, people didn’t believe the turbines were that loud at night, but now the study shows it,” adding that the results leave him more determined to “give our residents a good night’s sleep.”

As in Falmouth, where violations were also found in only some conditions and just over the limits, dozens of neighbors are complaining of lost sleep and other related health issues.  EPA standards developed in the 1970’s suggested that noise sources are fairly well tolerated when they remain within 5dB of existing ambient levels, and that at 10dB above ambient, “widespread complaints” are likely.  The detailed results from Fairhaven were not released, but the Falmouth report showed all locations exceeding 5dB, and most exceeding 7dB.  Some states still use 5-6dB thresholds, though many have moved to the 10dB used in Massachusetts, or refrain from the difficult task of regulating noise based on ambient conditions.  The Massachusetts measurement protocol has elements that may in part compensate for the larger 10dB threshold, and other elements that could counter that compensation: the standard compares the L90 sound level (quietest times) of ambient conditions with the absolute peak sound levels of noise from the turbines, rather than the average of each, which may somewhat increase the dB difference; however, the use of “slow” five-second time averaging, rather than “fast” one-second samples (closer to how the human ear perceives sound) likely results in lower peak measurements. Again, though, quibbling over exactly how the measurements take place can obscure the larger issue, which is that current standards appear to be insufficient to keep complaints to a minimum.

The three large wind farms currently operating in Vermont have spurred enough noise complaints to trigger an investigation by the state Department of Public Service.  DPS Commissioner Chris Recchia said “I want to get to the bottom of this….It’s not what was expected.”  Recchia suggested that he’s considering asking the Public Service Board to reconsider their existing noise standards.

Since last fall, 105 formal complaints have been filed, by 23 different individuals living near the Sheffield, Lowell, or Georgia Mountain wind projects.  Annette Smith of Vermonters for a Clean Environment is also collecting confidential complaints, some from people who have filed formal complaints, and some from neighbors who have felt it to be futile to complain to the turbine operators and/or state.  

The DPS is hiring a noise expert to analyze the complaints, and comparing them to quarterly noise measurements made near each wind project.  After this analysis, the DPS has three options, and could recommend one or more: enforce standards if they find violations, create a more effective system for operators to respond to complaints, or ask the PSB to change the noise standards if necessary.

See this recent local news article for more, including details of a recent bad night for neighbor Kevin McGrath, whose house is pictured above.

On June 9, 2008, 26 common dolphins, 21 of them infants, stranded and died in river estuaries around Falmouth Bay, as several days of Naval exercises involving over 30 ships wound down (see AIEnews coverage at the time).  A four-year study (read it online) has  concluded that unspecified Naval activities are “the most probable (but not definitive) cause” of the strandings, which involved at least 60 animals in all, with most of the adults re-floated and guided back to sea.  

The study ruled out other common causes of cetacean strandings, including foraging for fish in shallows, attack by orcas, illness, algal toxins, recreational boats, and earthquakes.  However, the researchers also could not identify a likely trigger among the Naval activities taking place on the morning of the strandings or the day preceding the discovery of the struggling animals.  Press reports at the time suggested that locals heard some large explosions on the day before and day of the strandings, though the researchers did not find records to indicate such activity. Mid-frequency sonar transmissions ended four days earlier; that or other ongoing activity is thought to have driven the dolphins into the bay, with unknown further disruptions triggering the fatal strandings early on the 9th.  According to lead author Paul Jepson, “Eyewitnesses described their behaviour as swimming continuously in tight circles, being vocal, fluke-slapping, leaning sideways, and often with one or more individuals attempting to strand.” 

The lack of a clear cause for the final stranding event during a relative pause in Naval activity on the day before the early-morning discovery of the floundering dolphins adds a familiar ambiguity to the situation.  A Naval spokesman noted that they disagreed with the report’s conclusion and stressed their decades of similar exercises in the area without mass strandings, while conservation groups including the NRDC and the UK-based Whale and Dolphin Conservation called for exercises to be redesigned. While cetaceans can often move away from unwanted noise, it’s long been known that strandings can occur when animals become trapped in areas with no escape route, such as apparently happened here.

Despite Naval denials of responsibility, this event did spur some changes that have led to later exercises being temporarily suspended when dolphins appeared on the verge of being trapped in a similar situation.  As detailed in the new study:

Following this MSE (Mass Stranding Event) and recommendations from the organisations involved in the rescue of dolphins in the MSE, the UK Ministry of Defence initiated the Marine Underwater Sound Stakeholders Forum in the UK to regularly meet with all interested stakeholders (scientists, other Government Departments like Defra and a range of non-Governmental organisations) to discuss these issues in some detail. A direct line of communication was also established after the Falmouth MSE to facilitate rapid exchange of information between cetacean strandings/sightings organisations and Royal Navy Naval Command Headquarters to report groups of pelagic cetaceans seen unusually close to shore and potentially at increased risk of stranding. This was used to report a near-MSE of over 20 common dolphins in the Fal estuary in April 2009 that was seen 15 minutes after RN sonar trials were initiated in the region. The RN immediately modified the naval exercise (including use of active sonars) until the group of dolphins had returned to open sea several hours later. The need to alter training excercises due to the presence of dolphins has not subsequently occurred in this region.

According to the authors, “Such continual improvement of mitigation strategies by the military themselves is probably the best way to limit future environmental impacts of naval activities, including cetacean MSEs.”