4 Steps to Conduct Emergency Inspections of Solar Power Plants Using Drone Surveying

After typhoons, heavy rain, strong winds, earthquakes, lightning strikes, snowfall, nearby construction, or the discovery of abnormalities during patrols, solar power plants need to ascertain on-site conditions as quickly as possible. However, plant sites are extensive, and it is not easy to inspect slopes, embankments, drainage channels, along fences, behind panel rows, beneath mounting racks, and other hard-to-access areas in a short time. One effective measure is drone surveying of solar power plants.

Here, drone surveying refers to a means of on-site inspection that includes aerial photography, records with geolocation information, and cross-referencing with orthophotos and drawings. When used for emergency inspections, it allows confirmation from above of areas that are difficult to see from the ground, making it easier to organize the locations of damage and anomalies. However, simply flying a drone does not mean all anomalies will be detected. Pre-flight safety checks, clarifying inspection objectives, setting the imaging coverage, managing location data, and combining drone data with on-site verification are important. This article explains 4 practical steps for conducting emergency inspections of solar power plants using drone surveying.

Table of Contents

• Step 1 Clarify the objectives and priority scope of the emergency inspection

• Step 2 Check safety conditions and determine whether flight is possible, and avoid attempting unsafe flights

• Step 3: Photograph the anomalous area from above and associate it with location information

• Step 4: Cross-reference images with on-site inspections to inform restoration decisions

• Precautions When Using Drone Surveying for Emergency Inspections of Solar Power Plants

• Summary

Step 1 Organize the purpose and priority scope of the emergency inspection

The first thing to do in an emergency inspection of a solar power plant is not to fly a drone, but to clarify what the inspection is intended to confirm. After a disaster or the occurrence of an anomaly, there is a tendency to try to quickly survey the entire site, but flying with an unclear purpose can result in missing areas that need to be captured or spending extra time later locating positions. In an emergency inspection, it is important to set priorities within the limited time and check the highest-risk areas first.

For example, after a typhoon or strong winds, check for uplifted panels, deformation around the mounting structures, flying debris, fence damage, and fallen surrounding trees. After heavy or torrential rain, it is important to look for clogged drainage channels, standing water, slope failures, sediment inflow, scouring/erosion, muddy conditions, and whether roads and maintenance access ways are passable. After an earthquake, focus on tilted racks, ground level offsets, cracks around foundations, displacement around cable racks and junction boxes, and deformation or damage to internal site roads. If lightning strikes or a sudden drop in power generation is suspected, rather than relying only on visible damage, first narrow down the affected systems or sections so you can determine the inspection/photography scope efficiently.

Drone surveying is well suited to getting an overview of large sites. In particular at solar power plants, where it can be difficult to grasp the whole picture by ground patrol alone, aerial images make it easier to understand the distribution of anomalies. It is a major advantage that you can clearly identify which ranges of panel rows have soil and debris washed in, which direction drainage is backing up, where fallen trees are located along the fence, and which parts of the access paths are impassable. In emergencies, before examining individual faults in detail, understanding what is happening across the entire site becomes the starting point for recovery planning.

On the other hand, inspections of solar power plants often require electrical checks and close-up visual inspections. Even if drone surveys capture images from above, it is not possible to determine the condition of all equipment. For example, the condition inside junction boxes, details of wiring connections, the state of protective devices, insulation-related assessments, and small loose bolts require on-site verification based on appropriate qualifications and procedures. Therefore, a realistic approach is to have drone surveys handle overall situational awareness and location mapping for emergency inspections, while combining on-site verification for detailed equipment diagnosis and recovery work.

When organizing the objectives of an emergency inspection, it is easier to proceed if you divide the site into several areas. Dividing it into the panel area with the power generation equipment, the vicinity of the receiving/transforming and collection equipment, drainage facilities, slopes and retaining walls, fences and gates, management roads, and areas near boundaries with adjacent land will reduce missed photographs. At large-scale solar power plants, organizing the inspection scope so it can be cross-referenced with section names on the drawings, panel rows, road names, and equipment numbers will also make later reporting and restoration instructions easier.

Also in emergency inspections, it is as important to record "where you looked" as it is to record "where you could not look." By documenting areas that could not be flown over due to strong winds, areas with poor visibility because of trees or terrain, areas that were off-limits, and areas that could not be filmed due to poor communications, you can hand this information off to subsequent ground inspections. If inspected areas and unconfirmed areas remain mixed, stakeholders can easily misunderstand the situation. Especially in emergency response, clearly separating judgments such as "confirmed," "needs reinspection," "entry prohibited," and "recovery priority" helps prevent secondary damage and improves work efficiency.

Before flight, collecting past drawings, the power plant layout, management partition maps, patrol records, timestamps of anomalies, power generation monitoring data, and information from on-site personnel enhances the effectiveness of drone surveying. What is important here is not simply pursuing the numerical accuracy of survey results, but gathering, without excess or omission, the information required for emergency inspections. If you identify locations with a high likelihood of damage in advance, it becomes easier to decide the flight route, shooting altitude, and shooting direction. Conversely, if you aimlessly photograph the whole site without organizing anything, you will need to review a vast number of images later, which will slow down emergency response.

Emergency inspections at solar power plants require quick decisions on many matters, such as whether power generation has stopped, whether access restrictions are necessary, the priority of restoration work, and the preparation of materials to share with stakeholders. Drone surveying is an effective means of gathering the information for those decisions, but it only demonstrates its value when the objectives and priority scope are defined. First, clarify the purpose of the inspection and decide whether to prioritize obtaining an overall understanding, verifying anomalies in specific sections, or preparing restoration work plans, then proceed to the next safety checks.

Step 2: Check safety conditions and flight feasibility to avoid attempting unsafe flights

In emergency inspections, the desire to see the site quickly tends to take precedence. However, the highest priority in drone surveying of solar power plants is safety. At sites immediately after a disaster or immediately after an abnormal event, the risks are higher than usual. In situations where strong winds remain, rain continues to fall, slopes have loosened, drainage is not keeping up, there are fallen trees or flying debris, there are abnormalities around electrical equipment, or access roads have collapsed, attention is required not only for the flight itself but also for the positions of the pilot and assistants.

First, check the weather and wind conditions. Drones are easily affected by wind aloft, and even if conditions seem fine on the ground, local wind disturbances can occur due to changes in site elevation, valley topography, slopes, buildings, and trees. Solar power plants may be installed in mountainous areas, developed land, coastal zones, or open hilly terrain, and the way wind hits a site can vary greatly. During emergency inspections, it is important not to operate under conditions close to the drone’s flight limits just to rush filming. If there are concerns about aircraft stability or sudden gusts are expected, decisions such as restricting the flight area, changing the timing, or prioritizing ground checks are necessary.

Next, confirm the safety of the takeoff and landing area. At power plants after a disaster, maintenance walkways may have been washed with soil and branches, and puddles or mud may have formed. If the takeoff and landing area is unstable, it can lead to the aircraft tipping over or foreign objects being drawn into the propeller area. Also, attempting to take off or land near solar panels or electrical equipment increases the risk of equipment damage in the event of contact. The basic rule for choosing a safe takeoff and landing area is to select a place with few people or obstacles nearby, stable ground, and where the operator can easily see the aircraft.

When deciding whether flight is permissible, you must check laws and regulations, operator rules, local safety standards, and permission from relevant parties. Even for emergency inspections, you must not omit checks regarding no-fly zones or flight procedures. If there are houses, roads, railways, power lines, communications equipment, airport-related areas, or public facilities nearby, a more cautious judgment than usual is required. Even if you plan to fly only within the premises of a solar power plant, you need to consider the possibility of drifting outside the site due to wind or of communications becoming unstable.

Also, during emergency inspections multiple stakeholders may gather on site. The power plant manager, the chief electrical engineer, maintenance personnel, civil engineering staff, restoration contractors, security personnel, and liaisons with local governments or landowners, among others, may all be operating at the same time. If the flight area, flight time, takeoff and landing locations, no-entry zones, and emergency contact procedures are not shared before flying a drone, there is a risk that the aircraft and ground workers will come into close proximity. In particular, people inspecting between panel rows or beneath racking can be difficult to see from above. It is advisable to schedule drone surveying at times that do not interfere with ground work.

Inspections of the aircraft and peripheral equipment are also essential. Before flying, check battery levels, the condition of the propellers, communication status, the status of position information acquisition, camera settings, available capacity on recording media, and whether spare equipment is available. In emergencies you may want to shorten preparation time, but mistakes in aircraft or recording settings can lead to missed shots or the need to re-fly. If re-flying becomes necessary, it actually takes more time and increases on-site risk. Complete any preparations that can be done before arriving on site so you can focus on safety checks and final settings at the location, which is more efficient.

Specific considerations unique to solar power plants include reflections from panel surfaces, changes in the radio environment caused by mounting racks and fences, the distance to transmission and communication equipment, and issues with altitude perception on slopes. Even if imagery seen from above appears flat, there can actually be significant elevation differences. When using automated flight or shooting at a fixed altitude, it is important to set a safe flight altitude with sufficient margin for the terrain. There may also be obstacles not shown on drawings, such as trees, power lines, guy wires, lightning protection equipment, poles for surveillance cameras, and meteorological observation devices.

It is also important to establish in advance the criteria for aborting a flight. If the wind strengthens, rain begins, the aircraft’s behavior becomes unstable, communications are disrupted, third parties approach the area, birds fly nearby, or the operator has difficulty maintaining visual contact, prioritize safety even during an ongoing shoot. In emergency inspections, preventing accidents or secondary damage is more important than avoiding leaving areas unphotographed. Areas that could not be photographed should be recorded as unconfirmed and supplemented by ground inspections or reflight on a later date.

When checking safety conditions and whether flight is permissible, you should assess not only whether it can fly but whether the necessary information can be obtained safely by flying. If most items cannot be judged even from above, it may be better to prioritize on-site verification rather than forcing a flight. Conversely, when entry is dangerous or a wide-area overview is required, conducting drone surveys under appropriate conditions can gather information while reducing the risk to on-site workers. Even for emergency inspections, maintaining an approach that does not omit safety checks will ultimately lead to faster and more reliable responses.

Step 3: Photograph anomalies from the air and associate them with location information

When conditions for safe flight are met, actual aerial imaging is carried out. The purpose of using drone surveying for emergency inspections of solar power plants is not simply to take pretty pictures. It is important to record in a way that allows you to determine where anomalies are, how extensive they are, and how they will affect restoration work. To do this, it is necessary to link the captured images with location information so that relevant personnel can identify the same locations later.

Organizing photography is easier if you separate overall assessment from detailed inspection. First, take overview photos of the entire power plant or the target section to confirm the general distribution of damage and abnormalities. Then photograph any locations where abnormalities were found or priority inspection areas from a closer distance. Overview photos alone make it difficult to see details, and close-up photos alone make it hard to understand positional relationships. In emergency inspections, it is effective to keep a set of images showing the overall positional relationships together with images showing the condition of the abnormalities.

In solar power plants, rows of panels often repeat in similar patterns, so it is easy to mistake locations when looking at images alone. Especially at large-scale plants, the scenery can be so uniform that when images are reviewed later it may be unclear which row or which position is shown. To avoid this problem, it is helpful when photographing to include plot names, roads, fences, drainage channels, equipment numbers, access paths, and landmark structures in the shot. In addition, linking location information to the image data makes it easier to share locations in reports and recovery instructions.

There are anomalies to check during an emergency inspection that either have an extent or occur at a point. Inflow of sediment, puddles, slope failures, poor drainage, and fallen vegetation need to be understood as areas. Panel cracks, deformation of mounting structures, fence damage, flying debris, fallen trees, and subsidence of maintenance roads should be recorded as point locations. Because drone surveys make it easy to organize these on aerial images, they provide material for prioritizing restoration after an emergency inspection.

When photographing, we use not only overhead images but also angled images depending on the situation. Overhead images are suitable for grasping positional relationships and the extent of an area. Angled images can make it easier to understand the tilt of mounting structures, fallen fences, how slopes have collapsed, the apparent thickness of soil or sediment, and the condition of obstructions. When checking the surface condition of solar panels, adjust the shooting angle while considering reflections and shadows. However, because angled shots can make it harder to read positions, it is necessary to consciously keep separate images for positional reference and for condition assessment.

During emergency inspections after flooding or heavy rain, recording water flow and areas of standing water is important. From above, it is easier to grasp the extent of puddles, blockages in drainage channels, the direction of sediment outflow, and the flow paths of turbid water. However, reflections on the water surface and turbidity make it difficult to judge depth, so care should be taken not to conclude from images alone whether it is safe to pass. Even after the water recedes, the ground may be loosened, or the ground beneath management roads may have been scoured. It is safer to use drone surveying to identify suspicious locations and, when necessary, follow up with on-the-ground inspections.

In inspections after strong winds or typhoons, broadly check for flying debris and disturbances in rows of panels. If branches or materials are lying on panels, they can not only affect power generation but also cause additional damage. Damage to fences or gates is also related to the risk of third-party intrusion. If obvious deformation of mounting structures or panels is found, do not approach; record their positions and condition from above and refer them to a specialist for assessment. Drone images are also useful materials for sharing the situation with stakeholders who are not on site.

In post-earthquake inspections, photograph with attention to ground offsets, cracks, the boundaries of embankments and cut slopes, displacements of drainage structures, and deformations of access roads. From the air, large changes to the ground surface and linear anomalies can sometimes be easier to detect. However, small cracks and internal damage to structures may not be visible. Therefore, a practical approach is to use drone surveys to extract locations that may have anomalies and narrow down the areas that require close-up ground verification. In emergency inspections, it is important to record anomalies that can be judged immediately separately from those that require additional confirmation.

When managing captured imagery, file names and folder organization are also important in practice. In emergencies, data from multiple flights and multiple operators tend to get mixed together. Organizing files so that the capture date, power plant name, section name, flight number, inspection purpose, and inspection target are all identifiable will reduce the time spent searching for images later. If the image storage location is unclear or the shooting order becomes unknown, valuable drone survey data will be harder to use for recovery decision-making. For emergency inspections, it is important to decide on the organization method at the time of capture.

Furthermore, if possible, perform an initial on-site check immediately after shooting. After retrieving the aircraft, briefly review the images to see if there are any missed shots, out-of-focus or improperly exposed images, or images with unclear location. If you notice insufficient coverage after leaving the site, a revisit or reflight may become necessary. Especially for emergency inspections, time is limited, so completing at least a minimal on-site check reduces downstream rework. It is important to ensure that the captured images clearly convey the location and condition to anyone who views them.

Images obtained through drone surveys become more valuable when they are organized by overlaying them with drawings and parcel information rather than viewed on their own. Being able to identify which parcel has which anomalies, which maintenance access routes provide access, whether recovery vehicles can enter, and where additional investigation is needed allows for a smooth transition from emergency inspections to recovery planning. To turn information captured from above into decision-making material usable on site, it is essential to be mindful of linking positional information from the imaging stage.

Step 4 Cross-check images with on-site verification to guide recovery decisions

After acquiring images through drone surveying, do not stop at merely looking at them; corroborate the images with on-site inspections and existing information to inform recovery decisions. In emergency inspections, the important thing is not only to find anomalies. It is to clarify whether the anomaly will affect continued power generation, whether it poses a safety issue, whether immediate action is required, whether monitoring over time is sufficient, or whether contacting specialists or stakeholders is necessary. Drone images should be used as supporting material for those decisions.

First, while reviewing the captured images, classify the abnormal locations. Divide them into places that are clearly dangerous, places where equipment damage is suspected, places that appear to have drainage or ground problems, places that could lead to third-party intrusion or affect the surrounding area, and places that cannot be judged immediately and require additional inspection. Once this classification is made, it becomes easier to decide the order of on-site inspections. For example, if there is a problem with the boundary to the outside due to a damaged fence or fallen trees, it is necessary to rush to secure safety in parallel with equipment restoration. If poor drainage continues, consider the possibility that damage could spread with the next rain, and early action may be required.

In on-site inspections, personnel actually approach the locations found in drone images to check their condition. However, in emergency inspection sites, it is a premise that hazardous areas should not be entered forcibly. If there are slope failures, ground subsidence, flooding, fallen trees, deformation of mounting structures, or abnormalities around electrical equipment, people with the appropriate scope of responsibility and qualifications must confirm safety before approaching. The advantage of drone surveying is that you can assess the situation from above before suddenly entering an area suspected to be dangerous. By estimating the level of danger from the images and considering the method of entry before moving to on-site confirmation, the risk to workers can be reduced.

When matching images with on-site inspections, be careful not to confuse locations. At solar power plants, rows of panels with the same shape and similar maintenance aisles can continue, so the anomalous spot in an image may be offset from the actual on-site location. Use multiple landmarks—section numbers, equipment numbers, fence corners, drainage branch points, road curves, surrounding terrain, etc.—to reduce misidentification. If the location is ambiguous from images alone, take additional photos on site and supplement the records so the location can be identified later.

In restoration assessments, we combine drone imagery, on-site photos, power generation monitoring data, past inspection records, design drawings, meteorological information, and interviews with local personnel. Even if drone images show anomalies in part of a panel row, the actual impact on power generation may not be determinable without electrical verification. Conversely, a decrease in power output may be observed while aerial images show no visible anomalies. Therefore, it is safer not to base conclusions solely on drone surveys but to make judgments in conjunction with other confirmation results.

In post-emergency inspection reports, it is important to organize the information so that stakeholders can immediately understand the situation. Including the inspection date and time, inspection scope, flight conditions, areas confirmed, areas unconfirmed, main anomalies, locations of anomalies, expected impacts, the need for additional checks, and the necessity of temporary countermeasures makes the report practical for field use. Because describing locations using text alone can be difficult to convey, organizing the information by mapping zone data and anomaly locations onto aerial images helps align the understanding of managers, on-site workers, and recovery personnel.

To move on to recovery work, priorities must be clarified. Items that affect human safety, those that have external impacts, those that could lead to further damage to power generation equipment, and those that may worsen with the next rain or wind require prompt attention. On the other hand, there are minor cosmetic changes that do not immediately affect power generation and items that can be monitored over time. When drone surveying reveals the distribution of anomalies, it becomes easier to determine where to start responding across the whole site.

Also, the results of emergency inspections can be used for subsequent inspections and preventive maintenance. If patterns emerge—such as water pooling in the same spot after heavy rain, debris frequently landing around a particular section of fence after strong winds, repeated soil erosion on part of a slope, or the same area of an access path becoming muddy—these can serve as material for considering permanent countermeasures. Recording emergency conditions with drone surveying not only supports temporary restoration but also helps improve the overall operation and maintenance quality of the power plant.

Storage of data is also important. Images and inspection records from emergencies may be used for insurance purposes, explaining to stakeholders, informing landowners and neighbors, confirming details with contractors, and as reference material for future comparisons. If captured data is left only on personal devices or stored in a way that makes its location unknown, it cannot be used when needed. It is desirable to organize and store files by power plant name, inspection date, disaster name or details of anomalies, section name, etc., in a format that makes them easy to search later.

Information obtained through emergency inspections only becomes actionable for operations once it is shared among stakeholders. Even if only on-site personnel know the situation, response will be delayed unless it is communicated accurately to managers and recovery contractors. Conversely, simply sharing images is not sufficient for decision-making unless it is clear where and what the problem is. The results of drone surveying directly inform recovery decisions when location, condition, priority, and next actions are shared together.

Finally, after an inspection it is important to review the response. Confirm whether the imaging coverage was appropriate, whether pre-flight preparations were sufficient, whether the organization of image locations was clear, whether coordination with on-site verification was smooth, and whether reporting did not take too long. Emergency inspections occur unexpectedly, but by standardizing the lessons from each experience into procedures, the speed and quality of future responses will improve. It is important not to treat drone surveying as a one-off imaging task, but to incorporate it into the operation and maintenance framework of the solar power plant.

Precautions when using drone surveys for emergency inspections of solar power plants

When using drone surveying for emergency inspections of solar power plants, you need to understand its limitations and points of caution, not just its convenience. Drones excel at wide-area visual checks, but they cannot automatically determine every anomaly. Anomalies that do not appear in images, anomalies that are difficult to see due to angle or lighting, problems with internal equipment, and electrical faults should be confirmed using other inspection methods in combination.

Especially at solar power plants, you must inspect both the generation equipment and the civil engineering structures. If you only look at the appearance of the panels and racking, you can overlook poor drainage or slope deformations, which may allow damage to expand later. Conversely, if you focus only on sediment and puddles, you may miss fence damage, flying debris, whether maintenance roads are passable, and the need to secure safety around equipment. In emergency inspections, it is necessary to take an integrated view that covers generation equipment, electrical equipment, civil engineering works, perimeter management, and access roads.

It's also important not to over-rely on drone survey results. Aerial images can make steps look smaller than they actually are, make it difficult to judge the depth of puddles, and allow cracks on slopes to be hidden by shadows. Reflections on panel surfaces can also change how damage or dirt appear. Therefore, rather than concluding something is safe simply because no anomalies are visible in the images, assess whether the inspection objectives have been adequately confirmed. If necessary, add ground-level photos, close-up visual inspections, verification with surveying instruments, and electrical inspections.

Careful attention must also be paid to the timing of flights. Immediately after heavy rain it is easier to identify water flows and areas of standing water, but if rain or wind remain the risk of flying increases. As time passes the water may recede and it may be safe to fly, but the conditions immediately after the event can become harder to assess. After strong winds you may want to inspect flying debris and equipment damage quickly, but it may be necessary to wait until the wind subsides. In emergency inspections, decide whether and when to fly by balancing the freshness of information with safety.

Also, drone survey data only becomes valuable when it is organized in a way that stakeholders can easily understand. Simply sharing a large number of images can leave recipients unsure where to look. Organizing information such as the location of anomalies, capture direction, priority, and whether additional inspection is required makes it easier for managers and recovery teams to make decisions. In emergency inspections, the speed of organizing and sharing the data after capture is often more important than the capture itself.

Advance preparation can also make a big difference. If you try to determine flight routes and inspection areas for the first time during an emergency, decision-making will take longer. By establishing during normal times a site layout map, candidate takeoff and landing sites, obstacles to watch for, priority inspection areas, disaster communication protocols, and data storage rules, you can act smoothly in an emergency. Drone surveying of solar power plants can be used not only after disasters but also for routine patrols and record keeping, so it is advisable to have operational procedures in place ahead of time.

In emergency inspections, it is necessary to treat the entire process—from on-site safety, verification of laws and rules, coordination with stakeholders, and data management, to recovery decision-making—as a continuous workflow. It is not something that can be completed by the person operating the drone alone; it is important to have a system in which personnel responsible for power plant management, maintenance, electrical work, civil engineering, and safety management can all view the same information and make decisions. Drone surveying is useful as a means of creating that shared information.

Summary

To conduct emergency inspections of solar power plants using drone surveying, it is important first to clarify the inspection objectives and priority areas, confirm safety conditions and whether flights are permissible, then photograph any abnormalities from the air and link them to location data. By cross-checking the acquired images with on-site verification and existing information and using them to inform recovery decisions, emergency responses can be more easily applied in practice.

Drone surveying is an effective means of quickly grasping the overall picture of a large solar power plant and of pre-inspecting locations that are difficult to access or suspected to be hazardous. After typhoons, heavy rain, earthquakes, lightning strikes, strong winds, and the like, it is necessary to check not only the power generation equipment but also drainage, slopes, fences, maintenance roads, and surrounding boundaries. Using aerial imagery makes it easier to share the distribution of anomalies and restoration priority areas, and helps align understanding among stakeholders.

However, drone surveying alone cannot be used to judge everything about a solar power plant. The area visible in images is limited, and there are situations that require electrical verification, close visual inspection, and civil/structural safety checks. Therefore, drone surveying should be used as an entry point for emergency inspections and combined with detailed inspections and restoration work. Especially in emergencies, avoid unsafe flights, prioritize safety, and clearly separate and record the areas that have been confirmed and those that remain unconfirmed.

If flight procedures, inspection scopes, data organization methods, and ways of sharing information with stakeholders are established during normal times, it becomes easier to respond calmly when disasters or anomalies occur. In the operation and maintenance of solar power plants, the initial response after an anomaly affects the speed of subsequent recovery. It is important to utilize drone survey data obtained during emergency inspections to understand site conditions, plan recovery, prevent recurrence, and support long-term maintenance.

If you want to make emergency inspections of solar power plants more efficient, it is essential to operate with a focus on acquiring survey data that is easy to handle on site, recording with location information, and sharing that information with relevant stakeholders. To ensure smooth on-site checks during emergencies, it is important to establish drone surveying as a system that supports safety checks, location management, on-site verification, and recovery decision-making—not merely as a photography task.