Drone solar inspections are a niche job that require specialized skills and knowledge. In 2021, the Federal Aviation Administration reported that there are 244,568 licensed drone pilots in the U.S. Energy is the top industry for commercial drones (according to this annual drone report), so it comes as no surprise that a need for qualified drone pilots is growing in the solar industry.
Inspecting solar panels for heat irregularities using a drone is one common job for a drone pilot in the solar industry. How can a solar company determine whether or not a drone pilot is qualified for this specialized job? And how can drone pilots secure solar clients and build their client’s confidence that their drone services will produce beneficial and accurate results?
Becoming aware of common mistakes made during a drone solar inspection can help drone pilots know what not to do during an inspection and avoid tarnishing their professionalism. Also, solar clients who are aware of these common mistakes will be better able to ask candidates the right questions about their flight procedures when looking to hire a drone pilot.
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7 Drone Solar Inspection Mistakes You Must Avoid
These are seven mistakes to avoid if you want to achieve a successful drone solar inspection:
1. Improper Camera Angle
Improperly angling the visual camera and thermal sensor gimbal can ruin the images captured during an aerial solar inspection. At the wrong angle, solar panels’ reflective surfaces can point back into the camera and distort the data. To avoid this drone mistake, the camera and thermal sensor must be either angled perpendicular to the tilt of the panels or straight down 90° (NADIR).
Here are examples of what the camera angle should look like:
Here are examples of what the camera angle should NOT look like:
If you’re experiencing a disruptive glare, it’s acceptable to deviate your camera and sensor angle up to 20 degrees. Glare is a common issue during solar panel inspections and can be exaggerated by weather conditions and the time of day.
There are additional considerations to make if you’re inspecting a dual tilt solar system or system with tilt trackers. While inspecting a dual tilt solar system, use a nadir gimbal pitch (90° angle, straight down). If the system has tilt trackers, the panels will move throughout the day to stay angled toward the sun. In this scenario, you have to be ready to compensate for panel movement, adjusting the gimbal pitch in response to any changes in panel tilt throughout the day.
2. Not Verifying Data in the Field
It’s a rookie mistake to leave an inspection site without verifying the quality of the images you collected. We commonly see inexperienced drone pilots conclude their inspection and head back to the office to begin analyzing their images only to discover blurred images, missed panel sections, or corrupted data.
This is why it’s super important to verify your images while still in the field. The last thing a professional drone pilot wants to do is inform their client that they have to return to the site for a refly and that their solar report is delayed, costing the client time and money.
The solution to this solar drone inspection mistake is to spend time on site checking your images. Bring your laptop, use your phone as a hotspot, and upload the images for a quick review. You can also offload the images from the SD card onto the computer when changing batteries too. It’s just another good practice to ensure a successful inspection from start to finish.
What's included in YOUR GUIDE...
Techniques for Exposing Warrantiable Items on Your PV Sites.
A Proven Roadmap for Successfully Implementing Drones in Solar.
Strategies for Identifying DC Losses and Avoiding Downtime.
3. Not Using a Solar Irradiance Meter
A solar irradiance meter, like the General Tools DBTU1300, measures the amount of solar power the panels have collected from the sun. With a reading from a solar irradiance meter, you can confirm that your infrared camera will be able to capture high quality thermal data during the inspection. The minimum level of irradiance recommended for drone thermography is 600 watts per square meter. To reach a high enough irradiance, there must be enough sunlight reaching the surface of the solar panels. When irradiation levels are too low, it becomes more difficult to locate anomalies on the panels. This can occur during certain weather conditions, like an overcast day.
Example of good solar irradiance
Check the irradiance throughout the inspection as well because weather conditions can change dramatically in just a short time span. Learn how to use a solar irradiance meter and get into the practice of checking the readout every 15-30 minutes. You can set a timer as a reminder and document the readout by taking a picture with your phone or tablet. The photos will save to your device in chronological order and provide a timestamp of when it was taken so you can track the changes.
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4. Flying While Overcast
As mentioned in the previous section, performing your inspection in overcast conditions can negatively impact the quality of your thermal data. It’s best to perform drone solar inspections on a clear day—or a day with a minimum cloud cover of 2/8 Oktas. ‘Okta’ is a meteorological term used to describe the amount of cloud cover. The scale ranges from 0 Okta (completely clear skies) to 8 Okta (full overcast).
There are several weather apps to choose from that will tell you the Okta, such as Weather Radar. You can view what the clouds will look like up to a few days in advance. Incorporate this step into your flight planning preparations and plan to fly when the forecast indicates clear skies or low Okta day. It is better to wait out bad weather than to rush an inspection when overcast conditions are expected in a few hours. The latter causes undue stress on the drone operator and can cause unnecessary mistakes.
5. Not Performing a Site Walk-Around
A site walkaround before you take flight can improve your efficiency and prevent accidents. During the walk-around, look for possible hazards/obstacles like power lines, trees, bird nests, etc. This will provide you with a better understanding of the layout of the PV system. This is a good time to establish the minimum obstacle clearance altitude (MOCA) you’ll need in order to set your return-to-home accordingly. Plus, you can also plot out secondary landing locations in case of an in-flight emergency.
Whether your operation site is a secluded solar farm surrounded by farmland or a busy warehouse with a rooftop system, skipping the site walkaround is a mistake. Pilots who skip the preliminary walkaround leave themselves vulnerable to crashes, lost drones, or damaged equipment. It is something many pilots don’t do, but it should not be overlooked.
6. Flying With Winds Over 15MPH
Here is another important weather variable to take into consideration for drone solar inspections: wind. You cannot fly a drone solar inspection when winds over 15 mph.
Flying with winds over 15mph is a mistake because it will cause a “cooling” effect across the panels and make it hard to locate the anomalies. Strong winds can also destabilize the drone, making the images blurry and depleting batteries faster.
To measure wind speeds, try out this handy device called an anemometer. An anemometer measures wind speed in real time, so you’ll know if it is too windy to perform the inspection. Also, keep in mind that the wind at ground level is often not as strong as it is at higher altitudes where the drone will be flying.
7. Flying at the Wrong Altitude
There are a few mistakes that drone pilots make when choosing how high to fly the drone during a solar inspection—calculating altitude incorrectly, flying too far from or too close to the panels, or not knowing their client’s requirements for GSD (ground sample distance).
There is not one set altitude for drone solar inspections. It varies based on factors such as the millimeter length camera you have, how much detail is required in the inspection, and what kind of solar system you’re inspecting.
By far, the biggest mistake drone pilots make when calculating their altitude is basing it from AGL (above ground level). This is incorrect because in a PV solar inspection, the altitude is based from the surface of the panels, not the ground.
This creates special considerations for elevated solar systems like rooftop and carports. For example, if we fly a ground mounted system at 100ft and then inspect a rooftop system, we are no longer flying at 100ft. Now we need to factor the height of the roof too. If the panels are located at the top of the roof which has a height of 50 ft, we will need to add them both together and fly at 150ft.
Flying too close or too far away from the panels can be a problem depending on your required GSD (ground sample distance). GSD represents the level of detail required for an inspection. It relates to the number of pixels that exist within a distance measured on the ground. A smaller GSD equates to more detailed imagery, which achieves higher quality data. A drone flying close to the panels can more easily locate and diagnose anomalies than a drone flying far away.
Knowing what GSD is required for the flight is another important step you must take to avoid any data quality mistakes. Discuss the inspection requirements with your client to get a better understanding of how much detail you need in your images. Plus, take into account the different requirements for the type of camera and lens you have.
Steps to Achieving a Successful Drone Solar Inspection
Using a qualified drone professional to conduct aerial thermography solar inspections is one major way solar companies can achieve maximum solar energy production. Solar companies are reporting an average of $1,254/MW cost savings and 98% increase efficiency when they use drones to complete solar inspections in place of manual methods.
Our team at The Drone Life offers simple steps to getting a drone professional on site to inspect your solar farm. Start by contacting us, and we’ll answer any questions you may have. We will provide all the details of what to expect, from the equipment we use, types of data we collect, and deliverables we provide.
Each drone service package is tailored to the client’s specific needs. All you’ll have to do is provide general information of your PV system including site name, size, and mounting type to receive a free quote tailored specifically for your project.
Using our best-in-class drone technology, our experienced pilots will conduct the aerial inspection. Discover the located fault types, number of modules affected, estimated affected DC, estimated annual loss in revenue, and more. Using a site map and geo-referenced photos, your O&M team will be able to easily locate and remediate all issues. This cost effective and time efficient process can revolutionize your solar site’s operation for maximum solar energy production.
What's included in YOUR GUIDE...
Techniques for Exposing Warrantiable Items on Your PV Sites.
A Proven Roadmap for Successfully Implementing Drones in Solar.
Strategies for Identifying DC Losses and Avoiding Downtime.
