Wind Turbines: So what’s all the noise about?

Over the past few years, regulatory scrutiny over noise from wind turbines has steadily increased in Ontario. According to the Canadian Wind Energy Association, over the last 2 years, Ontario has built over 1000MW of wind power, and is slated to add another 300 MW in the not-too-distant future. That translates to hundreds of turbines that will eventually dot the Ontario rural landscape. Given this large influx of wind energy, the Ontario Ministry of the Environment and Climate Change (MOECC) has been systematically increasing the scrutiny under which it puts wind energy projects when reviewing them for regulatory approval, or when dealing with complaints. This article focuses on the noise aspects – which tend to be quite contentious.

During the assessment stage, wind turbine projects are given added scrutiny by requiring that cumulative noise impacts from all nearby wind farms are to be included in the assessment. Outside of renewable energy projects, this requirement is not common with the MOECC. Because of this requirement, two projects vying for a permit in each other’s vicinity are always competing for the same cumulative noise allotment at a given dwelling – in this case it’s first come, first served! The advice to developers here is: be the first to stake your claim. Once your project has been crystalized, you’re ahead of the competition!

Once the approval is issued for a project, the next important step is reviewing the Turbine Supply Agreement with the manufacturer. Developers will want to minimize their risk by ensuring that they have the correct noise level guarantee language that protects them, and commits the manufacturer to what the MOECC has approved for the turbines in the project.

Once the project is constructed and has come online, the operator of the wind farm typically has to have a 3rd party complete two types of noise audits: Noise Emission tests and noise Immission tests. It’s less confusing to refer to these as: Turbine noise measurements, and Receptor noise measurements. Turbine noise measurements (emission) aim to verify that the turbines supplied by the manufacturer in fact produce the sound power the manufacturer’s claim. Measurements are carried out close to the turbines and follow the CAN/CSA 61400-11 or IEC 61400-11 measurement methodology. Receptor measurements (immission) aim to verify that the cumulative noise levels from all the turbines at a given dwelling are in compliance with the MOECC noise limits stipulated in the Renewable Energy Approval (REA). In this case, measurements are carried out near the worst affected dwellings, and follow the measurement protocol outlined in the MOECC publication “Compliance Protocol for wind turbine noise”.

Both the audit types mentioned above can be complicated. This post focuses on Noise Emission tests. Here are some pointers for developers wading through this process:

Wind Turbine Noise Emission Audit measurements

1.    Identify early if there will be problems on site. 

Some site conditions are not conducive to obtaining reliable data. For example, if there are large forested areas close to the turbine in question, they may interfere with the ability to deploy a microphone, or may cause an elevated ambient noise level during measurements, increasing the uncertainty of the measured data and ultimately reducing quality. Catching such locations early (preferably before finalization of the project REA approval) can save a lot of time and headache later).

2.    Work with a firm that you trust, and that the manufacturer trusts. 

As a developer, you’ve signed a Turbine Supply Agreement (TSA) that has hopefully included some noise guarantee legalese that stipulates how a noise warranty claim can be made, how the turbine noise emission shall be measured, by whom, in what time frame, and with what kind of notice to the manufacturer. In order to protect yourself in the case of turbine noise emission non-compliance, ensuring that you satisfy the terms of those clauses while doing the measurements can save time and money, and increase certainty that the manufacturer will take your claim seriously and remedy the situation. To that end, involving the right firm to coordinate and conduct the noise emission measurements is critical to this process. Most TSAs will stipulate that measurements be conducted by a third party that is accredited to complete such testing. The accreditation referred to is an international ISO 17025 lab accreditation which includes a scope of measuring noise from wind turbines to the CAN/CSA 61400-11 or IEC 61400-11 measurement standard. The accreditation should specify one of the above standards. As an example, here is Aercoustics’ certificate of accreditation hosted on the Standards Council of Canada’s website. This ensures a manufacturer that when they receive a test report from a measurement body, the measurement body has the right quality management systems and competence to conduct the measurements correctly and reliably. In other words: Can they trust the data? As an aside, if you are a measurement firm, here is an article about getting your organization accredited for measurements.

3.    Plan out the measurements well in advance. 

Although the measurements themselves can be completed in as short as 3 hours (our personal record) a big part is related to the planning that goes into the measurement process. The measurement process is a highly coordinated event between the measurement firm, the manufacturer, the surrounding landowners and mother nature. The measurement firm has to maintain equipment in a short term deployable state, the manufacturer often has to be present or involved in ensuring the measurement equipment can communicate appropriately with the test turbine, the land owner has to allow the placement of the microphone and anemometer gear on parts of their property, and the wind has to blow at all the right speeds and at appropriate directions! So the more planning goes into the measurement, the higher the likelihood of a successfully completed measurement

4.    Review the results in context.

The results of an IEC 61400-11 test provide the apparent sound power level of a wind turbine – which is the overall noise emitted by the machine, as well as tonal audibility of a wind turbine – which is a measure of the amount of tonal characteristics of the noise emitted. It also provides uncertainty values for each of the measurements. This value is related to the tolerance of the equipment, the measurement method and the variation of measured sound during the test. It is important to review the results of such a test in context of those uncertainties, to ensure that a technically sound conclusion can be made from a certain data set.

Unlike most other noise emitting sources, a wind turbine cannot be switched on and off at will. Because one has to wait for mother nature to cooperate, field measurements of wind turbines is a more complicated process than measurement of other noise emitters. However, with the proper planning and expertise, accurate and precise measurements of wind turbine noise emissions can be made consistently and reliably. For further insight, contact me directly at [email protected].