Guidelines for wind turbine and weather radar siting
Recommended guidance for mitigation distances
Environment and Climate Change Canada's (ECCC) guidelines for wind turbine and weather radar siting are based on a general guidance statement developed by the World Meteorological Organization that suggests siting distances around weather radar within which wind farm proponents should not install wind turbines.
The distance between the wind turbine and the weather radar is one of the key factors when considering potential interference with the function of the radar. Additional factors that impact the weather radar include:
- the terrain on which the turbines are located
- the physical size of the turbines
- the spacing between the turbines
- the number of turbines located in close proximity to the radar
Many studies have determined that wind farm turbines erected within 50 km of a weather radar have the potential to interfere with the radar’s function. As such, the following guidance table has been developed as a tool for wind farm proponents:
Range | Potential Impact | ECCC Guideline |
---|---|---|
0–5 km | The wind turbine may completely or partially block the radar and can result in significant loss of data that cannot be recovered. | Definite impact zone: Wind turbines should not be installed in this zone. |
>5–50 km | Multiple reflection and multi-path scattering can create false echoes and multiple elevations. Doppler velocity measurements may be compromised by rotating blades. | Moderate impact zone: Proponents should consult with Environment and Climate Change Canada to assess potential impacts at the earliest development stage possible and develop mitigation measures. |
>50 km | Generally not observed in the data but can be visible in some conditions. | Low to Intermittent impact zone: Proponents should notify Environment and Climate Change Canada. |
Most importantly, wind turbines located within 5 km of a weather radar risk degrading the data for a wide range of area covered by the radar. Thus, proponents should not site turbines within the definite impact zone (0–5 km) as this could severely impact ECCC’s ability to gather critical weather information. Moreover, proponents who plan to build a wind farm located in the moderate impact zone (>5–50 km) should consult with ECCC and adhere to ECCC’s case-by-case recommendations on wind turbine siting to enable the wind farm and the weather radar to co-exist. While wind turbines located beyond 50 km generally do not pose negative impacts to the radar data, intermittent impacts could be possible in some atmospheric conditions, therefore, wind farm proponents should notify ECCC of all wind farm proposals at the earliest stage of planning (i.e. determining site location of wind farm).
Assessment process
Before undertaking any significant planning activities, wind farm proponents should contact ECCC on new wind farm development in writing through radarsmeteo-weatherradars@ec.gc.ca, submitting the following information:
- coordinates for proposed locations of turbine(s), which may be in latitude and longitude coordinates given in decimal degrees format (or UTM coordinates with zone reference)
- number of turbines in proposal
- hub/nacelle height (tower itself only – not including the length of the blades)
- turbine blade sweep diameter (or length of the blades)
- turbine base diameter (if known)
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For each submission, ECCC’s weather radar specialists will perform a preliminary analysis of the proposal in order to technically assess the likely impacts on the quality of products delivered by the Environment and Climate Change Canada radar network.
From this data, ECCC determines if there is potential for the wind farm turbines to interfere with the function of the weather radar (i.e. whether the main radar beam will intersect any tower or turbine blade).
If the preliminary assessment concludes that the proposed wind farm is either within an area that is already blocked from the view of the radar, and/or it is far enough away from the radar and below the radar horizon, then ECCC notifies the proponent in writing that it has no concern.
If the development is visible to the radar, ECCC considers the degree to which it will impinge on the radar beam at the various elevation and azimuth angles. This indicates the magnitude of negative contribution it will have on the radar data.
Once the impact has been determined, ECCC notifies the proponent and conducts further assessments of possible mitigation measures to eliminate or minimize the negative impacts. In cases where mitigation is required to enable the wind farm and weather radar to co-exist, ECCC and the wind farm proponent should work to reach an agreement to develop and implement agreed upon mitigation measures.
Potential mitigation measures
Based on experience in Canada thus far, the vast majority of wind farm proposals assessed as having the potential to impact an ECCC weather radar have been accommodated with some design adjustments or changes in scale. ECCC’s goal is to avoid significant interference that would hinder the timely and accurate production of watches and warnings of significant weather for populated areas or vulnerable infrastructure. In cases where mitigation is required, typically, the most effective mitigation measures are to site the turbines at ECCC recommended siting distances away from the weather radar or behind existing stationary obstructions (i.e. mountains) and out of the Radar Line-Of-Site (RLOS). Other mitigation methods vary in effectiveness, cost and scale, and could include:
- Decreasing the overall height of the proposed turbines, so that the blade tips will be below the base of the main radar beam to reduce the resulting frequency and impact of clutter
- Curtailing the use of the wind turbines during severe weather
- Radar software to recover weather data in the contaminated wind turbine regions
- Installing supplementary weather radar/instruments
Although these other mitigation methods could help reduce the negative impact of the wind turbines on the weather radar, they have cost implications for proponents and vary in effectiveness, and can be avoided by siting wind farms at the recommended distances away from a weather radar. For additional information on ECCC’s Guidance for Wind Turbine and Weather Radar Siting, please email radarsmeteo-weatherradars@ec.gc.ca.
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