Thermal Imaging For Solar Inspection
A Guide for professionals responsible for solar facilities and the application of Thermal Imaging in improving solar inspections and operational performance.
Table of contents
- Thermal Imaging For Solar Inspection
- A New Solar Panel Communication Model
- The Origins Of Thermal Imaging
- Intro To Industrial Thermal Imaging
- Solar Farm Industrial Thermal Imaging
- The Technological Shift Solar System Thermal Imaging Needed
- Get The Benefits Of Thermal Inspection In Your Solar Business
- 1. Initiate a Thermal Analysis Process for your solar operation
- 2. Define your Goals and Expectations
- 3. Decide whether To Contract or Do It Yourself
- 4. Ensure The minimum documentation required
- 5. Incorporate into your Preventive Maintenance Program
- 6. Train and certify your internal and external resources
- 1. Initiate a Thermal Analysis Process for your solar operation
- Get Thermal Imaging Right
- Conducting Solar Facilities Thermal Inspections
- Ensuring Safe Thermal Inspections.
- Selecting Thermal Imaging Inspection and Analysis Equipment
- Infrared Thermal Camera Settings
- What is Spot Size in thermal analysis?
- How does distance affect a solar thermal analysis?
- Why use Reference Photos in thermal imaging?
- Environmental impacts on thermal inspection
- Current Loading
- Ensuring Safe Thermal Inspections.
- Evaluating Results
- Complementary Technology
- Helpful Operations Hints
- Frequently Asked Questions
- What Market Leaders Say About Aerial Solar Inspections
- Science Of IR Thermography
- General technology background
- What are Thermograms?
- What are the Targets and Target Signatures?
- How does one Detect Thermal Anomalies?
- Radiation Implications
- What is Path Radiance and Atmospheric Transmittance?
- How do Atmospheric Transmittance and Atmospheric Absorption affect thermal analysis?
- What is a Blackbody?
- What is Emissivity?
- How does reflectivity affect thermal inspections?
- How does transmissivity affect thermal inspections?
- General technology background
- Resources And References
- A Word About Drone Inspection Services
- What Should You Do Now?
What would happen if your solar panels could talk to you?
What if the solar panel could tell you that it had a hidden defect destroying the ability to capture the solar energy?
What if your solar panel system could tell you it’s stressed and on the verge of a breakdown?
That communication would dramatically change the way we get power from those panels. It would revolutionize the maintenance process and save more equipment and labor costs.
Good news. Your solar panel equipment has always been talking to us. We just did not know how to listen and understand what these essential assets were saying to us.
Now we do!
A New Solar Panel Communication Model
Just like our immune system tell us there is something wrong by changing temperatures, you get a chill or a fever when there is an infection, so too do solar panels and equipment radiate temperature differences when things are awry. And we can read those temperatures with thermal imaging.
We use thermal imaging technology to visualize and measure temperature variations from the norm. And in the hands of solar farm maintenance crews, thermal imaging analysis leads to early detection, corrective action, and costly maintenance and repair avoidance.
So, what are the origins of thermal imaging?
The Origins Of Thermal Imaging
Thermal imaging dates back over 200 years when astronomer Sir Frederick William Herschel discovered the existence of infrared (1800).
He was curious about the thermal difference between the various colors of light, so he created a simple experiment using a glass prism. With sunlight directed to the prism, Herschel created a light spectrum and measured each color’s temperature. He found that the temperatures varied by color, and increased from the violet to the red part of the range.
His curiosity was piqued.
After noticing the color temperature pattern, Herschel decided to measure the temperature beyond the red part of the spectrum in an area without visible sunlight. Imagine his surprise when he found that this area had the highest temperature.
Thus was born the principle of measuring temperature based on visible and invisible light color, now called thermal imaging.
Intro To Industrial Thermal Imaging
Infrared thermal imaging is a passive technology. That is, the inspected object does not need illumination with a strobe or other external light source. Instead, the sensor measures infrared energy emitted naturally by the subject.
Today we cannot understand the health of individuals without using a thermometer. It is a vital instrument and ubiquitous in homes, clinics, and hospitals.
We expect Thermal Imaging to become a regular part of the solar equipment health diagnosis toolkit.
The fact is that infrared thermal imaging has become an essential tool for facilities and equipment maintenance, HSE (Health, safety, and environment) and quality assurance personnel at commercial and industrial facilities.
It’s no longer a question of if you need thermal imaging for these disciplines. It’s more a question of how often and when you need to conduct a thermal imaging survey.
The simple reality is that the longer your system faults go undetected, the more severe and costly they are to repair.
A thermal camera or thermal imager is a robust, non-contact tool for monitoring and diagnosing the entire solar power system’s condition. These thermal imaging cameras help your management teams identify problems earlier rather than later, document the issues immediately, and prioritize your efforts based on criticality.
With medicine, we are comforted in the knowledge that “prevention is better than the cure.” So too, in the solar energy management discipline. With Thermal Imaging, the prevention (diagnostic), costs are far lower than the cure (late catastrophic failure).
The benefits of thermal imaging extend beyond diagnostics and early prevention. Additionally, your thermal imaging scan is a non-destructive method to pinpoint energy losses in a solar panel system. Pair a thermal imaging camera with a visual analysis system used in evaluating panel effectiveness, and you can speed up inspections dramatically.
The same is valid for surfaces. The thermal imaging camera is an incredibly reliable method for scanning and visualizing temperature variations on entire surfaces accurately and quickly.
Solar Panel Thermography inspection programs are contributing to substantial cost savings around the world.
Your solar thermography inspection program will save you money too!
Infrared thermography is the art of transforming an infrared image into an image with temperature measurements. This type of image, referred to as a radiometric one, allows us to measure temperature value from the image. Every pixel in the radiometric image converts into a temperature measurement via complex algorithms incorporated in the camera’s software. A properly calibrated IR camera can provide accurate non-contact temperature measurements of the objects it records.
IR (infrared radiation) behaves just like visible light. Just like how we manipulate light using cameras, you focus IR using a lens and, more importantly, you detect IR by electronic sensors. Thermal imaging systems are primarily digital cameras tuned to respond to infrared radiation rather than visible light.
Manufacturers use IR cameras to boost preventive maintenance effectiveness and find defects in their assembly processes.
As a parent, you know that it is a sure sign of infection when your child has a fever. Similarly, industrial engineers and operators know that a temperature spike in a roller bearing is a sure sign that it’s about to fail.
Thermal imaging cameras used in solar panel inspection system:
- Are similar to a consumer video recorder or a digital camera, and just as easy to use.
- Deliver a comprehensive overview of the situation.
- Provide a detailed view of the situation.
- Identify and isolate problems.
- Measure temperatures and temperature differences.
- Document the findings and store that information.
- Clarify what needs repair.
- Highlight small issues before they grow into more significant challenges.
- Saves the user valuable time and money.
A typical solar farm has hundreds of points on the panels, trusses, connections, and even junctions providing information about system health. Traditionally, one would survey a Solar Panel system visually, or with an IR thermometer or a contact-measurement tool. That method is incredibly time-consuming and just like walking around blindfolded: you can only find trouble spots through trial and error. The risk of the inspector missing a small fault that’s affecting the entire system is very high.
Using a thermal imaging camera, an operator quickly locates and traces the source of energy leaks or loss from a solar system. The broken or less effective panels appear differently compared to the rest of the groups. Visually, you see a thermal trail of temperature differences.
And thermal imaging also applies to your operating equipment.
A quick inspection of operating equipment with a thermal imaging scan tells you more than you knew about the health of those systems. In general, operating equipment tends to heat up as they begin to fail. Use a thermal inspection to find stressed components or check overloaded electric circuits and see if there is overheating anywhere in the system. Potential electrical shorts show up as hot circuits or hot fuses.
A solar farm inspection with a thermal imaging camera can help:
- Visualize cracks that cause energy loss
- Detect missing, defective or even broken lenses
- Find moisture trapped in panels.
- Locate thermal bridges
- Find disruptions in district connections.
- Locate infiltration in panels
- Detect panel or system failures
Thermal imaging cameras are versatile, affordable tools that can help you ensure your solar farm’s effectiveness and the safety of the people who inspect and maintain the system.
Solar Farm Industrial Thermal Imaging
What is Infrared Thermography?
Infrared thermography is in simple terms using a thermal imager to detect radiation (heat) emanating from an object, converting it to temperature measurement, and visualizing the object along with the temperature distribution. The sensed temperature distribution images are called thermograms and are used to see the heat production on objects that would otherwise be invisible to the naked eye.
So, Infrared Thermography starts with the collection of an infrared image. It then converts the image into a radiometric one, allowing technicians to generate temperature value readings from the image.
The camera essentially converts every pixel in the radiometric image into a temperature measurement. It does so by using sophisticated algorithms in the camera’s software. Thus, a calibrated IR thermal imaging camera provides accurate temperature measurements of the objects it records without actually touching it.
What is Thermal Analysis as it relates to Solar equipment?
Thermal analysis is a non-intrusive method of using temperature and thermal characteristics or thermal patterns of solar plant equipment and solar farm structures to detect anomalies or inefficiencies.
The thermal analysis intends to detect abnormal thermal conditions or temperature changes that may indicate problems in their nascent stages.
Different technologies can be used in thermal analysis to detect dynamic changes in heating; however, using thermal imaging cameras is among the most effective.
What is a Solar Farm Thermal Inspection?
The preventative maintenance discipline is analytically rooted in the principle that early detection means more effective maintenance planning and managed downtime than unplanned outages.
A solar farm thermal inspection using thermal analysis is like giving superpowers to an operations maintenance team. They can see previously invisible problems.
A Thermal Inspection is also known as a “scan” or “survey.” This Thermal Scan takes place with solar equipment in service and working under load; thus, you avoid disrupting production, and outages are not needed to conduct the inspection.
In cases where service continuity is paramount, infrared thermal inspection advantages over other methods are insurmountable.
What do experienced players tell us about the use of Thermal Inspections?
National Fire Protection Association (NFPA) Standard 70B, Recommended Practice for Electrical Equipment Maintenance, lists suggested practices. NFPA 70B, section 11.17.5 states:
“Routine infrared inspections of energized electrical systems should be performed annually. . . More frequent inspections, for example, quarterly or semiannually, should be performed where warranted by loss experience, installation of new equipment, or changes in environmental, operational, or load conditions.”
NFPA 70B also recommends performing an inspection using instruments that use a scanning technique to produce an image of the inspected equipment, a capability inherent in every proper thermal inspection.
The US Government Department of Interior, Bureau of Reclamation, runs some of the most extensive, most complex facilities where continuity is essential. They are responsible for many dams in the United States, and you may know them as they hydropower, or the water guys. They have publicly acknowledged that thermal inspections have improved their effectiveness in identifying, solving problems, and reducing outages.
While the Facilities Instructions, Standards, and Techniques (FIST) of the Bureau of Reclamation discuss other equipment used to perform thermal analysis of equipment, it should be noted they conclude that Thermal Imaging is the most effective. They note that:
“Other technologies used to perform thermal inspections often yield less reliable results and only should be used when the use of thermal imaging equipment is not feasible, typically due to safety issues.”
In the words of the Reclamation:
“IR thermography returns approximately $4 in savings to every $1 spent on IR thermography. Savings result from:
- Avoiding forced outages resulting in revenue loss.
- Reducing severe damage caused by equipment failing catastrophically.
- Reducing costly, time-based preventive maintenance by predictive analysis of equipment condition”
In simple terms, infrared thermal inspections allow maintenance teams to see moisture intrusion, missing insulation, heat loss, stressed equipment, even a roof leak, and a host of other typically invisible facility problems in real-time.
While all of these issues are not directly related to solar operations, the processes and benefits are directly translatable.
There is no doubt that Solar System Thermal Inspections based on Thermal analysis, and explicitly using IR thermography, is a successful method for improving maintenance effectiveness and reducing maintenance costs.
A Thermal Inspection will do the same for you in your solar business.
The Technological Shift Solar System Thermal Imaging Needed
Mounting an Infrared Thermal Imaging camera to an unmanned aerial vehicle (UAV) may have the most potential to make Infrared technology the inspection system of choice.
Essentially, this approach allows surveyors to fly a thermal drone (IR enabled) overhead of and throughout a solar farm to get a bird’ s-eye view of the system. You can get pictures and measures of your equipment or facility that you may not have seen before, or you may have only measured infrequently due to the difficulty in accessing those viewpoints.
There are numerous ways IR inspection by unmanned aerial vehicle (UAV) is complementary to even the best foot infrared scans, surveys, or inspections. First, Unmanned Aerial Systems (UAS) offer an increased vertical resolution that would otherwise be impossible or too expensive to obtain due to the need for specialized rental equipment. Having higher vertical resolution ensures you have a more comprehensive view of how your entire facility is operating.
Don’t forget surveyor safety – UAV improves on this, too. Just as conventional thermal imager shortens the list of “difficult to monitor” (DTM) and “unable to monitor” (UTM) zones, drone-based thermal imagers make this list shorter yet – and that means less danger for workers than even the best first-generation IR solution.
The real attraction to drone-based infrared monitoring – the thing that’ll get nearly every solar system onboard – is how often you can do screenings. Because drone-based monitoring is so fast, it offers the option to have far more frequent tests – even weekly, if required. Remember that critical equipment can start showing stress at any point. If screenings detect them within a few days of starting, that results in a far more proactive response and an earlier return to higher efficiencies.
True, running thermal imaging UAV does require a skilled drone pilot to manage the equipment in a safe manner, which could raise operational costs slightly at first. But even after considering the initial equipment investment and operator budget lines, researchers have estimated that these costs are recouped in short order by making it far easier to find and repair previously unseen problems.
So while infrared inspections on foot are great, aerial inspection using infrared-detecting UAV is much better because they’re making it easier and cheaper than ever for even smaller companies to use sophisticated preventive maintenance solutions.
Viper Drones IR solar farm inspection solutions and drone inspection services have been built with industry leaders FLIR and raptor maps. It combines the infrared detection advantages of the most accurate and capable thermography technology with a professional flight platform chosen explicitly for thermal imaging missions.
It is safe, reliable, and simple to integrate into your solar asset inspection procedures or preventive maintenance program. It is equipped with high-end FLIR thermal sensors calibrated precisely to look for specific temperatures, palettes, and emissions profiles. With this kind of equipment, it becomes possible for operators of all sizes to purchase and manage their IR drones so that it’s even realistic to conduct weekly inspections.
However, especially when the overhead perspective is only needed infrequently, and given the regulatory uncertainty and challenges around managing a commercial drone inspection program, we recommend in those cases partnering with commercial drone service companies with industrial inspection domain experience.
Whether an operator needs more frequent testing, requires higher resolution, or is just looking for a cost-effective way to achieve greater efficiencies, industrial inspection drone services, or drone-deployed IR solutions are likely the preferred solution.
Understanding the difference – Comparing Manual Electric Testing to Drone Thermal Imaging PV Inspections.
The Manual Approach
Manual electrical testing is the de facto method of inspecting PV systems. The test, known as IV Curve Tracing, is the current industry standard for examining and evaluating a solar array performance. It requires trained, highly skilled technicians using hand-held testing kits.
Ideal environmental conditions such as dry, relatively-clear weather with little to no wind are necessary for conducting these tests.
For the test to be valid, panels must reach a certain irradiance level, and then the panel must meet a minimum and defined watt per square meter.
Each string or row of panels scheduled to be tested must be unplugged from the array and plugged into the manual electrical testing device.
But it’s not just a scale problem. Technicians manually interpret test results to determine the health of the field. This manual testing process takes hours or days for a small site and significantly more time for a sizeable 100-acre array.
What Are Technicians Identifying?
Testing technicians manually inspect for five different symptoms of impairments:
- SERIES LOSSES: Series losses are caused by excessive resistance in the circuit. This resistance can be due to degradation in a particular component, or the wiring between them. The increased resistance can lead to further deterioration and permanent damage.
- SHUNT LOSSES: A shunt causes power losses by providing an alternate current path and short-circuiting a module or cell. Such a diversion causes significant heating of the affected component.
- MISMATCH LOSSES: Mismatch losses occur due to the interconnection of solar cells or modules that do not have identical properties or experience different conditions.
- REDUCED CURRENT LOSSES: Soiling, shading, and degradation lead to reduced current losses. They may reduce the current, but not necessarily the voltage. This measurement is particularly susceptible to human error, such as incorrect model inputs, irradiance sensor orientation, or transient weather conditions.
- REDUCED VOLTAGE LOSSES: Reduced voltage losses are due to the increased temperature of the module, degradation, or the reduced contribution of a group of cells (e.g., due to shading), or due to a shorted bypass diode.
How Drone Thermal Imaging Helps PV Inspections
Drone thermal imaging for PV inspections, also known as aerial thermography, is increasingly required in contracts for PV system commissioning and maintenance. That is due to the speed and level of detail that the technology package can provide. It complements and enhances manual electrical testing.
Whereas the manual inspection of a small PV system may take hours or days, a drone thermal imaging inspection of hundreds of acres, including panel cell-level defect analysis, can be accomplished in a single day.
Longwave infrared (LWIR) cameras allow them to “see” in total darkness and through obscurants such as fog and smoke, measure temperature, and accurately detect anomalies.
Aerial thermal imaging cameras make it easy to quickly inspect a significant target area and pinpoint solar panel problems. They streamline the completion of qualitative analysis by allowing the operator to promptly see heat differentials across a solar field and identify possible impairments. While an aerial RGB (red, green, blue) or visible-light, camera helps detect non-electrical issues like soiling, shading, bird excrement, and animal nesting.
A thermal-only payload could potentially lead to false positives by misidentifying these same issues as electrical anomalies. So pairing thermal cameras with RGB cameras in a drone sensor suite provides both the required visible awareness and context to spot anomalies in the field effectively and accurately.
Moreover, a solar panel inspection drone system can be used effectively and bring value to operators in the solar industry. The drone solution can be used throughout the solar project cycle, from the permitting process, during the solar installation, during regular inspection and energy production. Visual images can be included in the permit application to support permitting. The same system and process ensure proper solar panel installation, PV inspection or solar cell inspection, and system-wide solar energy system inspection.
Simply put, the solar panel inspection drone system is the best way to conduct a solar inspection.
Get The Benefits Of Thermal Inspection In Your Solar Business
The well-experienced users of prevention maintenance disciplines and early adopters of thermal analysis and Infrared thermal inspections have publicly shared many of their experiences. We have relied heavily on the records available and our expertise in providing the following best practice guidelines for incorporating thermal inspection as part of your solar management process:
- Initiate a Thermal Analysis Process for your solar operation
- Define your goals and expectations
- Decide whether to contract or do it yourself
- Ensure the minimum documentation required
- Incorporate into your preventive maintenance program
- Train and certify your internal and external resources
1. Initiate a Thermal Analysis Process for your solar operation
Establish a standard policy for Thermal Analysis of all your facilities. Include optional variations allowing tailored practices that vary by the risk and nature of the facility.
Each local facility should adopt and tailor the global policy for local implementation.
2. Define your Goals and Expectations
Integrate Thermal analysis as a critical element of the overall maintenance program.
Use it as a supplement, not as a replacement for visual inspection.
For each facility, define the role of thermal analysis inspection. Is it a scan, a survey, an overview, or a detailed inspection.
Remember that there are situations where thermal imaging cameras are not adequate on their own to analyze the entire system. In these cases, implement other supplementary technologies to document the temperature variations on the specific equipment or area.
An effective thermal analysis inspection process uses various state-of-the-art thermographic imaging equipment, from drone-enabled to hand-held and including contactless thermometers, heat dots, or heat tape one-time applications, or thermal paint.
Each technology selected has benefits and limitations. Ensure you have defined the scope of use for each technology defining criteria for applicability and the associated practices around monitoring that application.
Create an internal process to collect and evaluate thermal measurement data, make maintenance decisions based on the analysis, and document and learn from the results.
Thermal analysis is a suitable predictive maintenance tool and a tool to augment any enterprise preventive maintenance (PM) practices. We recommend the following steps:
- Conduct qualitative inspections to identify problems.
- When you find a problem, create a followup action for a more in-depth thermal examination. Include a quantitative review using thermal imagers to quantify the magnitude of the problem.
- Apply your severity criteria to establish the appropriate corrective action.
- Follow up after the corrective action with a qualitative inspection to validate the problem resolution.
3. Decide whether To Contract or Do It Yourself
We recognize that one of the critical decisions every facility or operational owner faces is what to do inside versus outside.
Choices include doing it all in-house, doing it all with contract partners, or a combination based on the analysis of your specific operating characteristics.
In making the decision, you must understand and evaluate the breadth of thermal analysis inspection techniques, their respective value, and implementation requirements.
Operating characteristics that lean towards specific approaches require evaluation of the following:
- How critical is the equipment or facility to the mission of the enterprise or location?
- What are the potential benefits associated with maintenance savings from incorporating thermal inspections into an enhanced PM practice?
- What latencies and costs trade-offs are impacted by the approach selected?
Prioritize a minimum level of accuracy and consistency when weighing the economics and effectiveness of your implementation choices.
We recommend explicitly identifying which parts of the process to conduct with internal resources, and which are better delivered using external contract partners.
This sourcing decision is a critical point in developing your solar thermal analysis strategy and implementation, as all subsequent thermal analysis activities are affected by the ultimate choice.
Even when choosing to develop a complete thermal analysis and inspection process in-house, one may consider renting or leasing state-of-the-art thermographic systems for quantitative analysis, which can be expensive.
Thermographic inspection and analysis is an evolving technology landscape with new products and techniques emerging rapidly. Regardless of your chosen approach for implementing thermal checks, we recommend ongoing education and advisory relationships, which keep you updated.
4. Ensure The minimum documentation required
Document your local thermal analysis process for clarity and continuity. At a minimum, your documentation should include:
- The specific Goals of your thermal analysis and inspection process.
- Responsible employees, external resources, and their roles.
- Training strategies.
- A detailed listing of Plant equipment to inspect.
- Thermal analysis equipment minimum acceptable specifications.
- Equipment calibration requirements and records.
- Critical Inspection tools and processes. Ensure there is consistency in analysis and reporting.
- Any specific Inspection or Analysis guidance.
- Safety considerations, including the requirements for any job hazard analysis.
- Recordkeeping practices.
5. Incorporate into your Preventive Maintenance Program
For maximum benefit, tightly integrate thermal analysis inspections into the local PM program.
After identifying the specific plant equipment or areas of the facility where thermal analysis is beneficial, create a separate PM and job plan for the thermal analysis.
In the thermal analysis job plan, identify which devices and methods you use for thermal measurements. If there are site-specific issues, such as locating the camera or best angle of use, annotate those in the job plan details.
The thermal analysis PM and job plan should identify any allowed adjustments to the job plan, and PM frequency required.
We recommend incorporating thermal analysis inspections, such as annual drone-enabled solar thermal scans, throughout the facility under one PM. The periodic approach is more effective than performing thermal analysis inspections on equipment in a piecemeal fashion for PM purposes.
Recordkeeping is an integral part of the PM program and must include the details required for that process at a minimum. To optimize thermal analysis benefits, you should extend recordkeeping to include details specific to the thermal inspection process since comparison to past inspections is essential and valuable.
We encourage developing a benchmarking procedure along with practices on documenting subsequent inspections.
Benchmarking should include:
- Equipment to inspect.
- Loading equipment when checked. Ideally, perform the benchmark when the equipment is carrying a full load.
- Location of thermal analysis instrumentation relative to the target equipment. Frequently, there is the best spot or angle for setting the instrumentation to monitor the equipment. Document if multiple locations, perspectives, or distances are thermally analyzed or identify the best scanning and surveying position in the benchmark records.
- Specific Thermal measurement inspection equipment used.
- There are differences between cameras, angle of the lens, long-wave infrared (LWIR) or mid-wave infrared (MWIR), and any other relevant metrics.
- If you used hand-held radiation thermometers to collect data, then identify their Make, model, and emissivity value.
- If you use tapes and paints to determine temperatures, record the manufacturer and expiration date, and keep copies of the material safety data sheet (MSDS).
- Include thermographic images and visible photographs when possible.
- Try to collect a digital record of the component measurement when possible. If it’s not available, then keep written and compiled records.
- Whenever possible, record measurement conditions such as the distance from the target, any abnormal conditions at the facility, or other salient observations.
- Equipment temperature. Whenever possible, we recommend you record and include the equipment temperature in a trending program.
Make your benchmarks records available for comparison to all subsequent thermal analysis surveys. When inspectors identify significant temperature variations from the benchmarked temperatures, that variance should trigger further investigation.
6. Train and certify your internal and external resources
Do not expect benefits without the requisite training and certifications, whether using in-house teams or external resources.
Of course, training and certification depend on the complexity of the selected technologies and the precision required to achieve your goals.
Many cameras are relatively easy to use and need very little training to ensure proper, qualitative analysis. Even when using a hand-held basic radiation thermometer, for example, an IR temperature gun, the distance from and emissivity of the target can significantly affect the accuracy of the measurement. In some ways, there is an argument to be made that the more expensive technologies help ensure consistency and reduce the technical skill required of the operator.
At a minimum, training must include on-the-job training from a skilled operator. We recommend operators become familiar with the camera or other instrument manual and other technical resources and attend classroom training.
Keep in mind that qualitative thermal analysis equipment does not require certification, whereas quantitative measurements do.
Favor less complicated systems. The more straightforward to use, the system, the more likely the facility embraces the solution. And frequent use and experience with the technologies and techniques directly impact the use, results, and benefits within the facility.
We recommend requiring a certified operator to perform a quantitative review of problems identified by un-certified operators. The more critical the operation, equipment, or area of the facility, the more valuable the certified operators’ oversight. Ensure that you perform an accredited operator review before making critical decisions on outages and repair strategies.
Operator certification is essential when the results are for official records such as those pertaining to contract performance. Certification enhances the consistency and credibility of your operator or contract resource.
Get Thermal Imaging Right
How to Select and Maintain Thermal Analysis Hardware and Software?
Your choice of thermal analysis technology, technique, and software depend on the nature of your solar operation and local goals.
For most solar facilities, we find that measuring relative temperatures using qualitative inspection techniques, such as a drone-enabled overview, or facility scan, is sufficient for annual inspection purposes. This inspection process identifies most anomalies—cold or hot spots, loose connections, among others — to the degree necessary to inform further detailed investigation and, ultimately, any correction.
The systems used for qualitative inspections are less expensive, easier to use, and require less stringent certifications than hardware and personnel for quantitative inspections.
For qualitative inspections, a thermal imager that shows temperature gradients but does not calculate specific temperatures may be good enough. However, for quantitative thermal reviews, you need a radiometric imager which calculates spot temperatures at each pixel.
Consider the type of inspection, the accuracy required, and how the examination supports documentation needed when selecting the appropriate technology.
A hand-held thermometer provides a spot temperature reading but does not provide a thermal image which can be saved and compared visually. A thermal imager provides visual feedback, but no specific, measurable temperatures, while radiometers offer accurate measurements and visual feedback.
Tune your selection based on your specific requirements and the effectiveness/cost trade-offs implied.
IR thermographic equipment or systems are measurement systems. For consistency and accuracy, as with all essential measurement systems, we recommend you periodically recalibrate the imager or radiometer to ensure valid results. Do not undertake quantitative thermal analysis or inspection without a properly calibrated system.
Consider the calibration requirements and challenges when selecting your thermography equipment. For example, if the equipment must be sent to the supplier for calibration each year, you incur additional costs and lower equipment utilization. Factor in the calibration costs into the total cost equation.
The high-accuracy IR thermal analysis systems’ up-front purchase price is quite high, but so are misdiagnosis costs in a mission-critical environment.
Regardless of the solution selected, if you manage the process with your internal resources, the system used is only as good as the training provided to your operators. Do not skimp on training.
Given the variety of variables at play, from the training required for accuracy and maintenance costs, we recommend a total cost approach to understand the difference between various technologies and strategies.
When selecting an approach (in-house versus contract) or a system, consider the value of accurately determining a quantitative temperature, reducing the diagnostic and repair cycle time, and the financial risk of unplanned outages when you miss a faulty component.
Take a life-cycle total-cost approach to weighing the benefits and costs of each solution. A system that is pricier up-front may be the most cost-effective over time.
Cheaper solutions are not affordable if they fail catastrophically.
What are the essential features in selecting your thermal imager?
To maximize your camera’s value, make sure to choose a brand and model that fits your needs – from features to service and support. Your job keeps you on the move all day, taking you up ladders, into crawl- spaces, and through a rugged work environment. An excellent thermal imaging camera should offer you:
- Ruggedness – This camera is a tool, just like everything else in your toolbag. It needs to be rugged enough to withstand a drop from one or two meters up. It should also be easy to carry in one hand, with user- friendly buttons and menus.
- Resolution – Thermal imaging that is impossible to interpret won’t do you any good. Choose an infrared camera with enough resolution to create clear, crisp images that you can enlarge. For example, FLIR cameras offer Multi-Spectral Dynamic Imaging (MSX®), which embosses visual details onto the full resolution thermal image. MSX® adds perspective to the scene and allows you to read text and labels.
- Reporting – Once you’ve surveyed a problem area, you need to generate a report so you can plan the necessary repairs. FLIR pairs its cameras with FLIR Tools+, an image editing, and reporting software. You can use this program to instantly generate reports with information on the problem type, location, and steps needed to resolve it. Many cameras fit these needs available on the market.
Which infrared camera brand should you choose?
A well-established brand should be able to offer you:
- Variety – Different users have different needs. The manufacturer must provide you with a full range of thermal imaging cameras, from affordable entry models to advanced high-end models, to choose the one that best fits your needs.
- Accessibility – Whatever your application, you need to view and share thermal images quickly, and have the software to analyze and report your findings. Choose a thermal imaging camera that works with the correct software for your application.
- Service – While most thermal imaging cameras for facilities maintenance applications are as good as maintenance-free, accidents can happen. Your camera may also need occasional recalibration. Rather than having to send your camera half-way around the world, make sure the manufacturer offers a local repair center. That way, you’ll get the camera fixed and back at work as fast as possible.
- Accessories – Make sure you have a system that can grow with your needs. The manufacturer you choose should offer different types of lenses, displays, and other accessories.
- Training – There is more to thermal imaging than just knowing how to handle the camera. Select a manufacturer that offers proper training and application support when needed.
What affects your ability to measure temperatures with thermal imaging cameras accurately?
Some of the most critical factors influencing thermal measurements are:
- Thermal conductivity – Different materials conduct heat differently and have different thermal properties. For example, insulation material warms up slowly while metal objects warm up quickly.
- Emissivity – Emissivity is the power of a surface to emit heat by radiation. It is the most critical factor for correct thermal measurement.
- Reflection – Some materials are more reflective and reflect thermal radiation, just like a mirror reflects visible light.
- Indoor and outdoor temperatures – To detect missing, damaged, or inadequate insulation using thermal imaging cameras require a noticeable difference between inside and outside temperatures, usually around 10°C.
- Building material influences – Direct sunlight affects thermal measurements, but indirect sunlight can also have long-lasting effects.
- Heating and ventilation systems – External influences such as HVAC affect indoor measurements, particularly of surface temperatures.
- Influences on the inside of the building -Accessories and furniture, such as Bookshelves, cabinets, and even hanging pictures, have an insulating effect and affect measurements.
- Reflections from the surroundings – When scanning reflective targets, you should try to minimize the reflections on the image by adjusting the camera angle you are using.
- Type of materials used in the construction – Some materials, such as concrete, are “thermally slow” or change temperature very slowly.
- Methods used in constructing the building – For example, when building outer walls with an air gap between the facade and the shell, you create a temperature differential.
A Thermal imaging inspection provides validation for a broad variety of industrial processes – heat staking, hot-plate plate welding, infrared welding, laser welding, plastic joining operations, ultrasonic welding, vibration welding, among many others. You can check the quality of your assemblies or monitor the condition of tooling using this fascinating technology.
Conducting Solar Facilities Thermal Inspections
Ensuring Safe Thermal Inspections.
Personnel safety is of utmost importance for all operations and maintenance personnel. That’s true for solar thermal inspection analysis and inspection resources, whether in-house or contracted, also.
Thermal inspections, scans, and surveys typically occur while the equipment or facility is operating under load, which are inherently risky. Besides, solar thermal inspections occur near equipment, which poses additional risks from electrical and mechanical energy and physical hazards.
Thermal inspections are primarily a touchless routine analysis of equipment or components easily accessed. When a more in-depth analysis of equipment behind protective panels is needed, you should consider other thermal analysis techniques, such as heat tape or heat paint. Thermal tapes and paints, avoid hazardous exposure to the inspector. Even if they do not provide precise temperature values, the analysis still provides valuable information to determine if additional maintenance is required.
When a thermal inspection includes exposing the thermographer to hazardous energy sources, proceed with caution, and ensure it is conducted with the highest industry recommended safety standards appropriate to those risks.
Keep in mind that safety concerns in an industrial setting are not exclusive to thermal inspections. Thus your safety protocol should, at minimum, include any standard plant maintenance safety practices and supplemented for additional characteristics unique to the solar thermal inspection technique and process.
Some Typical Safety concerns in an industrial setting include:
- Inspections may occur when protective barriers on electrical equipment are removed, resulting in exposure to arc flash hazards. We recommend that thermal inspectors wear all appropriate personal protective equipment (PPE) and comply with facility-specific and industry-standard arc flash protection processes.
- For enhanced safety around safety hazards and to minimize the exposure to hazardous energy, we recommend inspectors adopt a “Freeze and Leave” practice, recording measurements, capturing the image, and immediately leaving the area.
- When possible, we recommend telephoto lenses to maximize the separation of the employee from potential hazards.
- We also recommend the preceding practices in the vicinity of exposed energized electrical equipment.
- Thermal systems and accessories can be bulky and heavy. Analysts must practice situational awareness and exercise care when climbing or maneuvering tight spaces.
- The thermal inspector role requires attention to the system, the camera, the target, and the image. Experienced analysts are vigilant to ensure their focus does not make them ignore the risks around them.
- In higher-risk situations, we recommend an inspection team, an inspector accompanied by an assistant. The role of the assistant is to focus on protecting the thermographer from hazards specifically.
- We recommend inspectors adopt a “Stop and Look” practice and not be in motion when making a measurement or collecting an image.
- There are valuable reductions in some risks for drone-enabled thermal inspections due to increased separation between the inspector and the target. However, drones introduce other risks inherent with the use of UAS generally, and the use of drones in the specific environment. In these situations, we recommend following all risk reduction protocols for thermal imaging and drone inspection services. When there are overlapping standards, we recommend following the more stringent policy.
Selecting Thermal Imaging Inspection and Analysis Equipment
A variety of methods are available for conducting thermal analysis and inspections at a solar facility. These include a thermal imaging camera, hand-held radiation thermometers, heat-sensitive stickers, paints, or numerous other combinations.
Benchmark practitioners tell us from their experience that the thermal imaging method delivers the best combination of information and accuracy.
The simple reality is that a picture is better than a thousand words. And, one thermal image captures information on thousands of points of thermal measurements.
Inexpensive cameras generally have a thermal sensitivity of less than 0.2 °C, an accuracy of 2 °C. , and provide quality information enough to trend.
Most inexpensive hand-held radiation thermometers provide an average temperature of an object, cannot discern the location size of the measurement area, do not allow the user to adjust emissivity, and introduce new errors into the measurements. Take great care anytime using a hand-held radiation thermometer.
As the imager price increases, so too do the quality of the image and accuracy of the readings generally.
Infrared Thermal Camera Settings
The thermal inspector should ensure that the following settings on the camera are correct before and during the inspection:
- The Date and time
- Atmospheric temperature (ambient air temperature)
- Relative humidity (use a portable hydrometer or use plant’s hydrometer)
- Distance to target
- Emissivity of target
- The temperature of objects that are reflecting radiation off the target (background temperature)
- Desired temperature range (from optional camera ranges)
- The Focus
Although distance measurement is not as critical for qualitative inspections, most cameras allow you to assign a distance value. Whenever possible, distance to the target should be approximated or measured, and programmed into the camera. The practice of recording the approximate distance enhances the data trended over the equipment’s life.
When quantitative measurements are required, then a more accurate value for distance must be measured. The distance to the object is critical because the camera uses this value to estimate the attenuation of the infrared signal based on environmental conditions.
Just like with professional photography, camera settings are essential for an accurate inspection. Some aspects cannot be manipulated in the thermogram after capturing the image. Typically, distance to the target, focus, and temperature range are not manipulated in the software. Better to get the settings right, and the image right, than to be forced to redo an inspection.
Sophisticated thermal imaging software typically allows for ambient temperature, emissivity, relative humidity, and reflected temperature to be manipulated after the fact.
It is always a good practice for the thermographer to set values as accurately as they can in the camera before performing an IR inspection. Those adjustments improve consistency and speed up the process of diagnosing problems quickly. An experienced thermographer following these practices can make recommendations immediately following the survey.
However, the system’s ability to adjust parameters after inspection within the thermograms is typically used to improve the image’s quality, analyze data, and create reports. A user may modify settings to develop similar or reference pictures that can be trended over time or compared to similar equipment.
What is Spot Size in thermal analysis?
Thermal analysis equipment records the temperature of a “spot” in the image and displays this temperature. The spot’s size is critical because the temperature recorded is the average of the temperatures of the pixels in the spot.
If the spot is too large, then the average smooths out any hot spot pixels, giving a misleading impression that the temperature is higher (or lower) than a smaller spot size would show.
To minimize the smoothing effect, inspectors try to keep the spot size as small as possible. But eventually, you run into practical limits. The spot size is determined in part by the proximity of the device to the target. In some cases, you must stay further away for safety, or because of physical obstructions. In those cases, we recommend using a telephoto lens to reduce the spot size of distant targets.
How does distance affect a solar thermal analysis?
The distance from the target is a critical variable in determining apparent temperatures accurately. And the physical distance of the infrared thermal equipment from the target is one parameter that cannot be corrected after the image is recorded. That is why its standard practice to measure or estimate distance and enter the value into the camera.
For consistency and to make the process simpler, experienced inspection teams mark the floor in front of the equipment with their preferred position.
With drone-enabled operations, there are many more sophisticated methods to geospatially mark and replicate an inspection.
Why use Reference Photos in thermal imaging?
Experienced thermographers know the value of a reference photo when analyzing thermograms. As a standard practice, they capture a visual reference photo with a standard camera simultaneously and from the same point of view used in obtaining the thermogram.
The reference photo simplifies the identification of components that are not so obvious in the thermogram. Incidentally, hand-held radiation thermometers do not capture visual data, so reference photos and notes are the only way to document the location and temperature data properly.
Environmental impacts on thermal inspection
Weather significantly affects the timing and techniques of infrared inspections. Avoid or reduce the effects of weather, particularly when you want quantitative temperatures.
Wind is essentially forced convective cooling and dramatically affects thermographic inspection of buildings, roof inspection, and even electrical, and mechanical equipment inspection outdoors. Even indoors, wind from air conditioning, and ventilation rapidly cool a hot spot affecting accurate temperature measurements. Eliminate or reduce as many of these indoor factors as possible, especially when conducting quantitative inspections.
There are no currently recognized standard wind correction factors. By experience, wind speed of less than 15 miles per hour (mph) is probably adequate for qualitative inspection. For quantitative measurements, we recommend wind speed lower than ten mph and ideally less than five mph.
We recommend the following practices for conducting thermal inspections in wind conditions:
- Use an anemometer to measure prevailing wind speed.
- Perform quantitative inspections in as minimal wind conditions as possible.
- Turn off the ventilation system for indoor inspections, if possible.
- When performing inspections on indoor equipment, do so as soon as possible after removing any covers or doors to minimize natural convection or forced cooling.
- Measure the component temperature downwind of the hot spot, if possible. This approach produces a more accurate result.
Qualitative inspections are relative comparisons and are not as negatively affected by the wind.
As long as all components in a survey or scan are affected equally by the wind, thermal signatures are comparable.
High humidity and smoke reduce the transmittance of infrared energy, which reduces the effectiveness of an inspection. Avoid IR inspections in high humidity or smoky conditions.
Early morning, evening, or nighttime inspections provide more accurate infrared inspection results by minimizing sun or solar effects. If the facility is not operating at full load during your preferred inspection window, that has an opposing effect on the results’ usefulness. A proper inspection requires a balance of all those variables.
When possible, conduct IR inspections with equipment operating at or near full load, mechanically and electrically. There are no simple load correction factors, making it even more critical to measure at full load when performing quantitative inspections.
It is crucial to record the loading as part of the IR inspection, but care should be taken that it is the steady-state load. Wait 45 minutes after a load change before measuring.
Do not perform thermographic surveys at low load in windy conditions.
There are four possible outcomes in evaluating thermal analysis inspections:
- A True positive. That is when a problem can be found, and the problem actually exists.
- A False negative, when the problem is missed, and there is a problem.
- A False Positive occurs when a problem is diagnosed where no problem exists.
- A True Negative is when no problem is located because no problem exists.
Reliable thermal inspection processes and evaluations identify all problems of concern. There should be no errors, as in false negatives, and no false positives ideally.
IR inspection is an essential and valuable tool for solar preventive and predictive maintenance, but it does have limitations.
Complementary solutions, combined with thermal analysis inspection, enhance findings, making it possible to find the root cause of problems more effectively and rapidly.
Some complementary technologies to consider include:
- Ultrasonic Solutions: Ultrasonic detection identifies frequencies above the audible (sonic) level. High (ultrasonic) frequencies accompany problems that may cause temperature variations. But ultrasonic solutions are also useful in detecting issues without temperature emitting a high frequency.
- Vibration Analysis: Vibration analysis are a helpful complement in diagnosing mechanical problems.
- Motor Current Analysis: Motor current analysis complements thermal analysis and provides insight into electrical motor problems.
Helpful Operations Hints
Here is a list of helpful hints useful to perform a quality thermal imaging inspection, scan, or survey.
- Consider Circuit loading when inspecting electrical equipment. Whenever possible, Perform comparative inspections with a load similar to the last review.
- Prioritize Inspections during maximum possible loading. Try to avoid examinations when operating below 40 percent of the rated load of the inspected equipment.
- Delay inspections for 45 minutes following changes in loading to allow for temperature to stabilize, especially when reading temperatures indirectly.
- Use a front-surface mirror (i.e., one with the reflective surface on the Glass’s front surface) to inspect the backside of a component. Do not use everyday mirrors due to their internal reflections.
- It is a useful practice to compare one phase of a circuit to the other phases because
- their emissivities are similar,
- the heat generation and dissipation effects should be similar,
- all phases are an equivalent distance from the IR temperature device, and
- all phases are likely loaded equally.
- Unbalanced loads, may be a normal operating condition, and account for some temperature differences between conductors.
- Inspect Surge arresters and bushings at night to reduce daylight reflection errors.
- It is common for large vertical motors to show several vertical hot “stripes” on the casing side.
- Horizontal motors show characteristic hot spots on the middle of the casing in an even pattern.
- Keep in mind, the heating patterns on an enclosure are likely the result of indirect heating. The actual heat source is hotter than the temperatures recorded on the enclosure surface.
- On an enclosure surface, the heat might result from a heater, resistor, or transformer attached on the other side rather than a critical component.
- Paint on mechanical components affects their emissivity.
- Remember that merely removing a protective covering or even opening an enclosure door affects temperatures, giving a reading not typical of normal operating conditions.
Keep the following checklist with the camera and complete the necessary steps:
- Conduct a job hazard analysis before each inspection.
- Assemble and check your thermal analysis equipment.
- Inspect and wear any personal protective equipment, if required.
- Check that you have all the necessary accessories (batteries, lenses, storage media, tripods) with your camera and that they are working, and adequately charged.
- If your thermal analysis equipment does not have imaging capability, consider including an additional digital camera.
- Compile and review previous scan or survey results.
- Compile reference material.
- Follow appropriate safety procedures.
- If a quantitative measurement is required, check that the thermal analysis instrumentation calibration is current.
- Adjust the settings of your thermal analysis instrument as needed.
- Verify and Set the correct distance to the target.
- Set the correct emittance value.
- Set the proper background energy levels.
- Focus the camera.
- Set the temperature range in the camera.
- Keep a record of the environmental factors, including relative humidity and wind speed.
- Verify that the instantaneous field of view measurement (IFOV) of the instrument or spot size on a hand-held radiation thermometer is smaller than the target.
- Aim the instrument perpendicular with the target surface to reduce errors.
- Check for and reduce thermal reflections from other point sources near the target surface.
- Keep as far away as possible, and secure instruments from very hot objects and energized equipment.
- Maintain accurate records and trend data.
Frequently Asked Questions
Where can you purchase solar facility thermal inspection services?
One can easily find a foot-based, Hand-held, thermal inspection service provider. We recommend selecting the most capable and certified thermographic services company.
Drone-enabled thermal inspections are a newer capability combining two domain expertise, which is more difficult to find. Viper Drones has partnered with several certified and capable thermographic service companies to deliver consistent, cost-effective, reliable, and safe drone-enabled thermal inspections. Contact our solar facility thermal inspection services team for more information.
How risky is the solar facility’s thermal inspection Supply Chain?
The solar thermal inspection supply chain is relatively low-risk. Major categories of providers and their associated risks are as follows:
The Thermal Imager Supply Chain risk is low. Most commercial solutions are readily available and not subject to international sourcing concerns. At the very highest end, the technology may be export-controlled. However, this sub-segment is not typically in commercial applications.
Thermal Imaging Systems Applications Supply Chain risk is low. Commercial applications are readily available with multiple vendor choices.
Thermal Imaging Drones Supply Chain risk is low to medium based on your sourcing strategy. A multitude of drones is available to integrate thermal imaging solutions. However, the market-leading supplier of drones, DJI, is based in China and may represent a supply risk. We recommend a diversified set of UAS integrations.
The Supply Chain risk of your Solar Thermal Inspection Services Partner is low to medium based on your partners’ reliance on the above categories. We recommend diversified partners.
The Supply Chain risk for Solar Thermal Inspection Personnel is low. Training is readily available, as are third-party service providers.
Can a solar facility thermal inspection be completely automated?
Not yet. With the advent of the Internet of Things (IoT), we see many applications where monitoring devices can be attached to various components or areas of the facility. As technology gets better, smaller, lower cost, and more communicable, we expect more thermal inspection requirements to become automated. However, we do not anticipate complete automation for a very long time.
Do formal inspection bodies allow drone use in solar facility thermal inspections?
Yes. In the USA, the FAA and similar bodies in other countries regulate the commercial use of drones outdoors. Outdoor drone use for thermal inspections is allowed subject to following drone regulations in your jurisdiction.
The FAA does not regulate drone use indoors, so there are no bodies currently regulating the use of drones indoors. We recommend you follow the FAA regulations for outdoor use while flying drones indoors.
We recommend you review our SUAS Toolkit for guidance on incorporating drones into your enterprise.
Can a drone be used as a formal solar facility thermal inspection tool?
Yes, aerial drones are used as a formal solar facility thermal inspection tool. A drone serves as an extension of any foot-based formal facility thermal inspection process. Much like a ladder, it is a tool that helps you collect aerial data, and it provides a different perspective from which inspectors conduct thermal inspections.
What Market Leaders Say About Aerial Solar Inspections
FLIR Systems is the world’s largest commercial company specializing in thermal imaging cameras, components, and imaging sensors. Based in Wilsonville, Oregon, United States, and founded in 1978, the company makes thermal cameras and components for a wide variety of commercial and government applications.
“Solar farm management costs the industry an estimated $1 billion per year in labor costs. In order to avoid unnecessary and unexpected costs, routine inspections are important to ensure everything is in proper working order. While these inspections are a critical element of operational efficiency, they can be both hazardous and tedious. An end-to-end inspection can be so labor-intensive that it may take weeks to perform solely with hand-held test equipment. The secret lies in aerial thermal imaging kits provided by FLIR Systems.”
“As the necessity of photovoltaic operations and management (O&M) increases, stakeholders have turned to thermal imaging for inspections to find problems more quickly and efficiently. FLIR aerial thermal imaging kits make it easy to quickly inspect a large target area and pinpoint solar panel problems from the air. Solar panels that are not operating efficiently tend to have a different temperature signature than panels operating properly. Panels that are not operating at peak performance due to issues with inverters, combiners, string failures, module problems, trackers out of alignment, or even shading – become visible in seconds with thermal imaging.”
“Thermal imaging technology can help you detect hot spots instantly – transforming a half-day job into minutes. “Solar panel inspections that once took half a day can be completed now in just 10 minutes or so,” says an ENETECH manager who provides maintenance service for solar power generation systems.”
“FLIR aerial thermal imaging kits are capable of detecting hot spots from 50 meters above the ground at a 300 kW level power station. You can view thermal images taken from the sky on a tablet at hand. This enables you to promptly locate abnormal spots and respond to the heat-induced swelling of the junction box on the back of the panel. You can also locate cluster defects by looking for discolored parts on the screen to promptly identify abnormal power spots. Early discovery is important especially for cluster defects that may cause a 33 percent power reduction in a solar panel. Incorporating thermal inspections into your routine maintenance plan will reduce your solar panel inspection times from weeks to hours when using a FLIR aerial thermal imaging solution. You’ll work more safely during inspections by reducing your exposure to the elements, and it will help improve your overall efficiency.”
Raptor Maps is a Boston startup, founded in 2015. They build Artificial Intelligence enabled software that works with drone technology to allow efficient solar operations inspections. The software reviews and processes hundreds of thousands of aerial images. It then classifies and prioritizes 100% of all anomalies, and provides the exact onsite location of each anomaly to be addressed. The result is a detailed, precise, and actionable report which solar operators can use to identify energy production loss and optimize solar plant performance.
“Drones are the suggested method to conduct a commissioning inspection and have been used on sites ranging from 50 kW to 400 MW. There are multiple reasons why aerial thermography and software should be used to conduct the commissioning inspection. First off, drones can be used to perform quality assurance inspections. Drones are faster, more accurate, and cheaper than manual commissioning inspections. Aerial thermography inspections allow for submodule level data on every module in the site. This is because drones can perform inspections that follow IEC requirements, which provide extremely accurate temperature data on the module level.”
“Upon deciding to have a commissioning inspection of the PV system, there are IEC compliant best practices that should be followed. This will ensure the results will be accurate and trustworthy down to the cell level of each module throughout the site. To begin, the inspection should be performed by a trained, experienced, and licensed pilot who has performed a commissioning inspection before, read this for more information on how to properly qualify a drone service provider. It is not recommended that a company purchases a drone and tries to learn how to fly it to perform these inspections. The results will not provide teams with the true condition of the site and the baseline for future reference points will be inaccurate.”
Science Of IR Thermography
General technology background
Infrared energy (IR) is part of the electromagnetic spectrum, and it behaves similarly to visible light.
That means that IR can be absorbed, emitted, reflected, and refracted.
All objects radiate IR depending on their temperature. Warm objects radiate more IR light than cooler objects.
An object that is at absolute zero (-273.16 °C) emits almost no IR radiation.
IR radiation is not visible to the human eye.
Thermography technology measures IR radiation and produces a visible image of IR light emitted by objects. That visible image correlates to the temperature of the object.
The correlated temperature image is called a thermogram. And the thermogram is developed using false-color (or pseudo-color) images that, in turn, make interpretation of the thermal patterns easier.
What are Thermograms?
Thermograms are maps of objects and surfaces using various color hues representing the distribution of thermal energy radiating from that surface or object. The radiation includes light or IR energy emitted, reflected, and transmitted, and potentially modulated by the atmosphere around that object.
The simple purpose of a thermogram is to visualize the temperature difference of the target compared to a reference temperature. The reference temperature might be ambient temperature, the baseline temperature of the equipment or facility measured under normal conditions, or the temperature of similarly loaded equipment or phases.
Simple Thermograms are “qualitative.” They represent thermal energy without correction for variables like reflection. Thus, they represent an approximate temperature.
Even without accurate temperature values, qualitative thermograms are valuable for the wealth of information they provide and their ease of use.
Quantitative Thermograms correct for extant variables, resulting in near-exact surface temperature, and numerical representation. The numeric data captured in a quantitative inspection can be trended and benchmarked in a more “data-based” approach.
Qualitative thermograms require less complex systems, are easier to use, and take less time to create. In many cases, Qualitative thermograms provide enough information for comparison and for the operator to find the source of the problem.
Interpretation of qualitative thermograms is subjective and not detailed to understand complex problems; thus, the qualitative analysis is a diagnostic approach to finding problems that require thorough or quantitative investigation.
Many PM teams find qualitative thermograms are sufficient. The systems and required operator training for qualitative inspections are quite affordable and can quickly provide valuable information about the condition of your equipment and facilities.
Teams that wish to use a more data-based and detailed review of their equipment and facilities use quantitative thermograms.
Quantitative thermograms generate more accurate temperature data, which is collected and analyzed to enable trending, detecting the severity of a problem, or even implementing early-warning systems.
The quantitative approach does require more sophisticated technology, including integration to your systems, and increased thermographer training and experience.
We recommend the following minimum strategy for thermograms:
For Annual PM IR inspections
Use qualitative thermal examination to compare to similar equipment, and to detect simple anomalies.
For Troubleshooting suspected or known problems
Use a qualitative thermal inspection to identify a problem, or quantitative thermograms to find the root cause and determine the severity of the problem.
For Evaluating repair work, Proof testing new installations, or Evaluating condition for condition- problem-based maintenance program
Use qualitative thermal inspection to determine if a problem exists and quantitative analysis to define the problem.
What are the Targets and Target Signatures?
A target is an object, equipment, surface, or facility that is to be detected, identified, located, recognized, and measured.
Target signatures are the baseline size (spatial), wave band (spectral), and temperature (intensity) features that discriminate against the target from the background.
Thermographic systems highlight the intensity differences. The signatures, like fingerprints, are the characteristic patterns that the thermographer learns to identify.
How does one Detect Thermal Anomalies?
Remember that thermal analysis is touchless and does not measure temperature directly. Instead, it measures the radiation that seems to emanate from the target. The measured radiation, therefore, includes the target’s self-emission, transmitted radiation, and reflections, among other variables.
We detect the difference between normal and abnormal temperatures by comparing an object of known emissivity and operating characteristics (a benchmark) or by symmetry (balance) when using a thermal imaging camera.
Comparing the temperature or thermal pattern of one object to a similar object that is known to be properly operating is one way of detecting irregularities. The more similar (i.e., the same manufacturer, same load, equal emissivity, and same environmental conditions), the objects compared, the more critical any observed anomalies.
Objects operating under normal conditions tend to exhibit a balanced or symmetrical pattern. Asymmetric patterns are another indicator of potential irregularities.
In simple terms, operators using thermal analysis develop a pattern recognition experience enabling the ability to discern anomalies. The pattern recognition skill is either a qualitative observation or a quantitative numerical deviation from historical norms.
Thermal solutions detect radiated heat energy emitted, reflected, and transmitted from a surface.
The IR imager receives all three types of energy, which contribute to variations between measured and the core temperature at the target.
A fourth factor, the geometry of the surface or object, also contribute temperature differences from actual
Pay attention to and factor in all four contributors to the inspection to achieve accurate measurement and correlation of emitted radiation.
What is Path Radiance and Atmospheric Transmittance?
Path radiance refers to radiant energy that comes from the medium (typically air) that the target energy passes through on its way to the IR measuring device.
Path radiance effect is frequently small, especially when the distance to the target is short.
How do Atmospheric Transmittance and Atmospheric Absorption affect thermal analysis?
The atmosphere around us is composed of many different gasses, particles, and other matter. This matter can absorb, redirect, or reflect radiation from the target to the imager. That resulting reduction in emission from the target reaching the IR measuring device is attributed to atmospheric transmittance.
When viewing a target from a long distance, you must include atmospheric transmittance in the target temperature calculation.
Atmospheric absorption refers to the process by which radiant energy is naturally absorbed by the atmosphere. The further away the thermal imaging instrument is from the target surface, the more likely the IR signal reduction due to atmospheric absorption.
The level of signal atmospheric absorption depends on weather conditions. High humidity, or snow, rain, dust, and other airborne matter, can increase absorption and reduce signal strength.
For most thermal inspections performed indoors, or in relatively close distances to equipment, ignore atmospheric conditions (weather). Postpone outdoor inspection in unusual weather conditions.
What is a Blackbody?
A blackbody is often referred to as an “ideal body” that completely absorbs all the radiant energy striking it. A blackbody, therefore, appears perfectly “black” when measured at all wavelengths.
Blackbodies are used as a reference to calibrate IR measurement devices. The radiation “emitted” by a perfect blackbody has an emissivity of one. It has a reflectivity of zero at all wavelengths.
What is Emissivity?
Emissivity is the property of a material that compares its ability to radiate energy relative to a blackbody at the same temperature.
The higher the emissivity, the more efficient an object acts as a radiator of heat.
Reference tables are available which identify the relative emissivity of various materials. However, these tables are reflective of idealized measurement conditions and only approximate.
Experienced thermographers do not rely on emissivity tables when conducting quantitative temperature measurements. They prefer performing their checks to determine the emissivity for each target.
Emissivity values are measured on a scale ranging from zero to one. Keep in mind that emissivity is affected by a variety of factors, including surface characteristics such as age, dew, dirt, dust, paint, frost, chips, scratches, and weathering effects, among others. Generally, smoother surfaces produce lower emissivity, while rougher surfaces produce higher emissivity.
For the most accurate IR readings, the target’s emissivity should be as high as possible. The result is that most of the measured energy emits from the target itself rather than reflected.
When measuring the temperature of low emissivity surfaces or objects, it is critical to reduce interference, such as reflections. This seemingly minor interference could introduce errors due to the naturally low emissivity of the measured object.
The viewing angle and temperature also affect emissivity. An experienced operator points the IR imager as close to perpendicular to the target surface as possible.
One cannot know the precise emissivity of the target and surrounding environment, and it can be time-consuming and challenging to determine. Therefore, it is tough to determine accurate temperatures. As a result, thermal Inspections tend to be mostly qualitative.
When quantitative values are required, the certified and experienced thermographer uses a comparison method. They determine the emissivity by comparing an object with known emissivity to the target object. Then they record and adjust the target emissivity accordingly.
How does reflectivity affect thermal inspections?
Reflectivity is the property of a material that describes its inherent ability to reflect energy from another source on the same side of the target as the infrared measuring device.
The measuring device reads a combination of reflected energy and radiated energy from the target, and the amount of reflected energy overstates the measurement.
Objects with high reflectivity and low emissivity, are particularly susceptible to variances. Experienced thermal inspectors work to minimize reflectivity in these situations.
How does transmissivity affect thermal inspections?
Transmissivity is the property of a material describing its ability to convey energy from another source on the opposite side of the target from the infrared measuring device.
The IR measuring device detects a combination of transmitted energy radiant energy, and the measure results in a false or inaccurate target temperature. This misreading is particularly challenging when the targets are transparent to infrared energy.
However, the transmissivity variance is rarely a problem in an industrial application. Opaque objects do not transmit infrared energy. Keep in mind; we are not talking about visible light, we are talking about infrared. Glass and many plastics are transparent to and transmissive to visible light, but they are opaque to infrared and appear black in an IR camera viewfinder.
That said, infrared windows found in an electrical panel, cabinets or housings act as filters and attenuate infrared energy.
The experienced thermographer is aware of the effects of transmissivity. They make provisions to eliminate such effects to arrive at accurate temperatures.
Resources And References
- Academy of Infrared Training
- Infrared Training Center
- IR Information for the Real World
- Infraspection Institute
- SUAS Toolkit
A Word About Drone Inspection Services
You can’t just buy unmanned aerial vehicles (UAV), hire a pilot and operators, and suddenly be able to conduct inspection services.
Whether it’s a construction job site, cell towers, commercial properties, solar farms, storage tanks, or wind farms, all industrial inspection services are conducted in challenging environments. It does not matter whether we are collecting data for asset management, maintenance, or structural integrity inspections, Safety is of paramount importance in conduct on the job site. As a safety-conscious service provider, we start every project with a detailed scope and risk assessment to understand what exactly our service teams will inspect.
All our inspection services are conducted with a finely-tuned professional industrial drone equipped with highly accurate specialized sensors, such as the thermal imaging sensors from FLIR. Confined spaces inspections require specially designed unmanned aerial systems (UAS). The inspection applications and inspection processes are tailored for the specific industry, industrial setting, and client project requirements.
Before we conduct any drone flight our equipment and technology go through several safety checks. And, we conduct a visual inspection of the job site and surroundings before takeoff. Every piece of drone data including aerial images is secured as a valuable asset.
Bottom line – a UAS program for drone inspection will reduce costs, increase safety, and deliver data faster to your company. But in order for that drone program to be sustainable and consistent, you will need solutions (applications, processes, technology) and partners with industrial inspection domain expertise.
What Should You Do Now?
Talk to your maintenance team, your HSE team, your engineering team, your drone team. Find out what your approach has been to Thermal Imaging, Thermal Analysis and Inspections.
If you are starting out and don’t have a Thermal Analysis program. Contact us. We will evaluate your mission opportunities to determine how much an optimized program could contribute to your bottom line.
We will evaluate your thermal analysis opportunities to determine how much an optimized program could contribute to your bottom line, and help you implement it.
If you have an in-house Thermal analysis team, and they are in need of some targeted solutions, contact us. We will show your team how to cost-effectively leverage the new methods and technologies to quickly get your solution in place.
We will show your team how to cost-effectively leverage the new methods and technologies to quickly get your solution in place.
If you have outsourced your thermal analysis and inspection services, and your provider does not have an enterprise view on reaching your needs, contact us. We will show you or your outsource partner how to move forward most effectively.
We will show you or your outsource partner how to move forward most effectively.
Advisor, Entrepreneur, Strategist, & Transformation Agent
30 plus years focused on mission-critical technology and operations