5 Measures to Prevent a Decline in Power Generation | Solar Power Improvement Points

Table of Contents

• Isolating causes is important to prevent declines in power output

• Countermeasure 1: Check power output data by time of day and by equipment unit

• Countermeasure 2: Manage dirt and deposits on panel surfaces

• Countermeasure 3: Minimize shading from weeds, trees, and nearby structures

• Countermeasure 4: Do not overlook abnormalities in strings, connection points, and power conversion equipment

• Countermeasure 5: Manage drainage, terrain, and inspection records to prevent recurrence

• Operational cycle to prevent power output decline

• Summary

To prevent a decrease in power generation, it is important to isolate the cause

To prevent declines in solar power output, rather than scrambling to respond after output has already fallen, it is important to identify the factors that lead to declines early and take action before generation losses become large. For operational personnel who want to increase or maintain output, the first concept to grasp is that, in solar power generation, you cannot increase the amount of solar irradiance itself on site. On the other hand, you can manage the received irradiance to convert it into electricity with as little waste as possible. In other words, measures to prevent generation decline are about maintaining a state in which no electricity that could be generated is lost.

The causes of reduced power generation are not limited to a single factor. Dirt on the panel surface; deposits such as bird droppings and fallen leaves; shading from weeds or trees; faults at connection points; cable damage; shutdowns of power conversion equipment; output curtailment; temperature rises; poor drainage; and site conditions that make inspection difficult—multiple factors can combine to lower power generation. Even if there appears to be no problem visually, checking generation by time of day or by individual unit may reveal that only some units have dropped significantly. Conversely, even if generation appears low, taking weather and solar irradiance conditions into account may show that it is not an equipment fault.

In practical work to prevent a drop in power output, it is essential to sequentially narrow down the causes of the decline. If generation is low only in the morning, consider shadows on the east side; if it is only low in the evening, consider shadows on the west side. If the midday peak fails to reach expected levels, soiling, temperature, or equipment-side limitations may be involved. If performance becomes unstable after rain, check for moisture ingress at connection points and the drainage condition. If only a specific string is low, partial shading, poor connections, or cable damage may be suspected. By reading the pattern of power loss in this way, the locations that need to be inspected on site can change significantly.

Also, to prevent a decline in power generation, it is important not to treat countermeasures as a one-time effort. Even if you clean, dirt will return; even if you remove weeds, grass will grow back; trees will grow; and equipment and wiring will change condition with age. As outdoor facilities, solar power plants are constantly affected by the seasons, the weather, and the surrounding environment. Therefore, it is necessary to record power generation data, on-site photos, inspection results, and work history, and to use them for the next inspection and for improvement decisions. From here, we will explain five measures that should be prioritized in practice to prevent a decline in power generation, following a workflow that is easy to verify on site.

Measure 1: Check power generation data by time of day and on a per-equipment basis

The first step to prevent a decline in power generation is to establish a proper method for checking generation data. If you only look at monthly or daily generation totals, you cannot tell when or where generation losses are occurring. Monthly generation is heavily influenced by the weather, so months with many cloudy or rainy days will show lower output even if the equipment is operating normally. Conversely, even if the monthly total does not appear to indicate a major problem, generation losses may persist during specific hours on sunny days or in some equipment.

When checking by time of day, pay attention to the shape of the generation curve. If morning generation is low, shadows from trees on the east side, slopes, nearby structures, or adjacent equipment may be involved. If it is low in the evening, check for shadows on the west side and the influence of surrounding topography. If the midday peak does not develop, candidates include dirt on the panel surface, temperature rise, capacity limitations of power conversion equipment, output curtailment, or equipment shutdowns. If there is a sudden drop in the generation curve even on clear days, it is important to correlate the times with stoppage histories and alarm logs.

Comparisons at the equipment level are also essential. If you only look at the plant’s total power generation, some anomalies can be obscured by the average. Compare units with the same orientation, the same tilt, a similar number of panels, and the same shading conditions, and check whether any particular unit is consistently lower. If only one unit is lower compared with units under similar conditions, it is more likely a site-related cause rather than the weather. Suspect soiling, shading, poor connections, cable damage, or equipment faults, and raise the priority of on-site inspection.

Declines in power output can occur suddenly or progress gradually. Sudden drops may be related to equipment shutdowns, wire breaks, poor connections, or the emergence of obstructions. Gradual declines may be related to the accumulation of dirt, the growth of weeds or trees, age-related deterioration, or worsening site conditions due to poor drainage. By understanding the pattern of decline, you can narrow down the locations that should be inspected on site.

Checking power generation data is itself the work of increasing power output. If you walk the site without looking at the data, inspections become broad and shallow and you may overlook important causes. If output is low in the morning, check for morning shadows; if it does not rise at noon, check for soiling, equipment issues, and temperature; if it is low in the evening, check for shadows on the west side—this way you can clarify the focus of inspections. To prevent declines in power generation, first separate generation data by time of day and by equipment unit, and visualize where generation losses are occurring.

Measure 2: Manage dirt and deposits on panel surfaces

Surface dirt and deposits on panels are a common cause of reduced power generation. Because solar panels generate electricity by receiving sunlight at their surface, adhered dirt reduces the light reaching the cells. The way panels become soiled varies greatly with the site environment, including soil dust, pollen, yellow sand (Asian dust), bird droppings, fallen leaves, tree sap, dust from nearby construction, road-derived dust, and salt-containing contamination common in coastal areas. Even a thin layer of dirt can affect power output if it spreads over a wide area, and localized deposits can act as a strong shadow even over a small area.

Particular attention should be paid to banded dirt that remains on the lower edge of panels and around the frames. It is often assumed that rain will wash it away naturally, but in reality the flow of rainwater can collect dirt at the bottom edge and leave it there. On gently sloped panels, water does not drain well and dirt tends to accumulate. Even dirt that is not noticeable from a distance can affect power generation if it covers part of a cell. During on-site inspections, you should carefully check not only the overall coloration of the panels but also the condition of the lower edge, the corners, and the areas around the frame.

Deposits such as bird droppings and fallen leaves should not be overlooked. Unlike uniform soiling, these accumulate heavily in specific spots and create partial shading. If only some equipment shows reduced power generation, inspect the panel surfaces in that area. Rows near trees, around structures where birds are likely to perch, downwind rows, and areas close to unpaved walkways tend to experience more soiling and deposits. If the area showing a drop in generation data overlaps with areas where fouling is visibly prominent on site, the cleaning priority should be high.

When cleaning, it is practical to prioritize areas that have the greatest impact on power generation. Rather than cleaning all panels at the same frequency, focus on rows where dirt is concentrated, equipment where a drop in generation has been confirmed, areas where lower-edge dirt is conspicuous, and locations with frequent bird damage or falling leaves. Comparing photos and power generation before and after cleaning makes it easier to determine how much the dirt at that site was affecting power output.

However, cleaning must be carried out in a way that does not damage the equipment. You should avoid vigorously scrubbing with hard tools, performing sudden work during periods when the panels are at high temperatures, or working without confirming the electrical safety of the equipment. Cleaning to prevent a decrease in power generation is not merely a cosmetic task to make things look clean, but a maintenance operation to restore the light-receiving condition and to enable long-term, stable use of the equipment.

When addressing soiling, it is important not only to remove dirt but also to understand the causes that make soiling likely to occur. Check whether dust is easily raised from unpaved walkways, whether fallen leaves or sap are likely from surrounding trees, whether there are structures that tend to attract birds, or whether the panel tilt makes it difficult for rainwater to drain. If you can identify locations where soiling repeatedly occurs, you can more easily adjust cleaning frequency and inspection timing, and more easily prevent a decline in power generation.

Measure 3: Reduce shadows from weeds, trees, and surrounding structures

Managing shade is extremely important to prevent a decrease in power generation. Because solar panels generate electricity from sunlight, even partial shading on a panel can reduce output. Causes of shading include weeds, trees, fences, utility poles, surrounding buildings, mounting racks, adjacent rows of panels, monitoring equipment, and other factors. Shadows move with the time of day and season, so the absence of visible shading at the time of inspection does not necessarily mean there is no problem.

Weeds are a common cause of power generation losses at sites. Even if there is no problem in winter or immediately after installation, they can grow rapidly from spring through summer and cast shadows on the lower edges of panels or the front rows. Even if the vegetation does not touch the panels, low sun angles in the morning and evening cause shadows to extend a long way. Furthermore, when weeds become dense, ventilation deteriorates, inspection pathways become blocked, and it becomes difficult to check around equipment. Because this affects not only power output but also maintainability and safety, weed management is a basic measure to prevent decreases in power generation.

Shadows from trees are a factor that tend to become problematic during long-term operation. Trees that had little impact at the time of installation can grow over several years and reduce power generation. Trees located to the south, east, and west in particular cast shadows on panels depending on the time of day. At power plants near forests or slopes, the height of the terrain combined with the height of the trees can create long shadows in winter. If generation is low only in winter, or there are large drops in the morning and evening, it is necessary to check the trees and the terrain together.

When checking shadows, aligning power generation data with the times of on-site inspections makes it easier to find the cause. If power output is low in the morning, check the on-site conditions in the morning; if it’s low in the evening, look at the evening shadows. Even if a noon inspection shows no problems, large shadows can appear in the mornings and evenings. Also, even if there are no issues in summer, shadows can lengthen in seasons when the solar altitude is lower. To prevent decreases in power generation, shadows must be managed not as a single moment but as something that changes with time and season.

When performing weeding or pruning, prioritize areas that have the greatest impact on power generation. Rather than merely tidying the entire site uniformly, focus on checking the area in front of the panels, around equipment, inspection pathways, and directions where shadows are likely to extend. After the work, record whether shadows have actually been eliminated, whether inspections have become easier, and whether ventilation has improved. Because shadow problems tend to recur, do not treat it as a one-time task; annual management that accounts for the growth of grass and trees is important.

Shadows from surrounding structures must not be overlooked. Adding new equipment within a power plant, or installing fences, signs, or surveillance poles, can create shadows at certain times of day. When carrying out renovations or additional construction, it is necessary to check in advance the impact on power generation. To prevent reductions in power generation, it is important not only to reduce existing shading but also to operate in a way that does not create new shading.

Measure 4: Do Not Overlook Abnormalities in Strings, Connection Points, and Power Conversion Equipment

To prevent declines in power generation, it is important to check for anomalies not only in the overall plant figures but also at the finest possible unit level. Even if the total generation does not appear to show a major problem, only some strings may be experiencing declines. Such partial drops, if left unaddressed, will continue to generate power losses over a long period. To increase generation, do not be reassured by the overall average; you need to find differences at the equipment unit or string level.

When comparing on a string-by-string basis, it is fundamental to compare units under the same conditions. If you simply compare systems that differ in panel count, azimuth, tilt, shading conditions, or connection configuration, you may misinterpret normal differences as abnormalities. Check whether any string is consistently lower compared with adjacent rows or installations with the same orientation. If only a particular string is low, possible causes include dirty panels, partial shading, poor connections, cable damage, or equipment-side issues.

Pay attention to how the anomaly appears. If it is consistently lower than the surroundings even on sunny days, dirt or connection problems may be suspected. If it is lower only in the morning and evening, check for shading effects. If anomalies tend to occur after rain, moisture ingress or the condition of the connections may be involved. If instability occurs during high-temperature periods, poor contacts or the temperature environment around the equipment are also possible causes. Combining the power output waveform with on-site conditions makes it easier to narrow down the cause.

Faults in connection points and cables are also a significant cause of reduced power generation. Many issues can impede the flow of electricity, such as loose terminals, poor electrical contact, damage to cable sheaths or insulation, moisture ingress, animal damage, damage during grass-cutting operations, and deterioration with age. Because these problems can be difficult to detect from appearance alone, it is important to narrow down the abnormal range using power generation data and make assessments by cross-checking with on-site photos and work records.

Don't overlook shutdowns of conversion equipment or output curtailment. If the equipment that converts generated electricity is stopped or its output is restricted, power output will not increase even when solar irradiance is sufficient. When reviewing shutdown logs, check which equipment stopped, when, and for how long. Even short shutdowns can cause large losses if they occur during daytime when generation is high. If stops and restarts are repeating during the day, it may not be noticeable in the monthly total, but you may actually be missing out on generated power.

When output curtailment occurs, generation can plateau even on sunny days. If the top of the generation curve appears flat, check curtailment records and operational information. However, a flat curve does not necessarily indicate output curtailment. Similar shapes can result from equipment capacity limits, temperature rise, soiling, shading, or measurement anomalies. It is important not to judge based solely on the generation curve, but to isolate the cause by combining equipment records with on-site conditions.

Inspections of electrical equipment are carried out with safety as the top priority. Rather than having on-site personnel forcibly touch equipment to make a judgment, we organize information such as which equipment is showing abnormalities, the time the issue occurred, changes in power output, on-site photos, and the surrounding environment, and, when necessary, escalate to specialized inspections. To prevent declines in power output, it is necessary not only to respond quickly but also to safely identify the cause using the correct procedures and to review the environment so that the same anomaly is less likely to recur.

Measure 5: Organize drainage, topography, and inspection records to prevent recurrence

To prevent declines in power generation, you need to check not only panels and equipment but also the plant's overall drainage, terrain, and inspection access routes. Areas where water tends to accumulate, locations where sediment can flow in, paths that easily become muddy, slope failures, scouring around mounting structures, and spots where cables are likely to be exposed can directly or indirectly cause reductions in power output. Poor drainage and changes in topography may at first appear unrelated to power generation, but they are important factors that lead to soiling, weed growth, connection failures, and reduced accessibility for inspections.

In areas where puddles remain after rain, weeds tend to grow. When weeds grow, they create shade, reduce ventilation, and make inspections more difficult. Muddy walkways can slow work, which can lead to less frequent cleaning and weeding. In places where sediment flows in, it accumulates under panels and around cables, causing soiling and damage. To maintain stable power generation, it is important to manage not only the generation equipment but also the site environment.

When checking topography and drainage, on-site inspections after rain are useful as well as inspections in clear weather. Determine where water flows in, where it accumulates, and where it drains away. Recording puddles, sediment deposits, vegetation overgrowth, pathway settlement, and slope changes will reveal locations prone to recurrence. If dirt or vegetation repeatedly reappears in the same spot despite cleaning or weeding, you should suspect drainage or terrain problems rather than just surface-level issues.

Inspection routes also play a role in preventing declines in power generation. Locations that are difficult to inspect tend to delay the detection of anomalies. If weeds have overgrown and paths are impassable, if it is too muddy to approach, if equipment numbers are hard to identify, or if abnormal locations are difficult to share, on-site response takes longer. Even if low-output equipment is identified in the data, if it takes time to reach the corresponding location on site, improvements will be delayed.

Organizing inspection records is also important. Even if dirt, shading, anomalies, or poor drainage are found on site, if the exact location is not shared, implementing countermeasures or rechecking will take time. Especially at large power plants, where similar rows and equipment are aligned, it can be difficult to identify locations from photos alone. If you record the locations of equipment with low power output, spots where shading occurs, rows prone to soiling, places where water accumulates, locations with connection failures, repaired locations, and areas that have been cleaned or weeded together with location information, you can overlay power generation data with on-site conditions for verification.

As records accumulate, plant-specific weaknesses become apparent. If you can identify patterns—grass growing in the same spots each year, dirt accumulating on the same rows, the same walkways becoming muddy after rain, or the same equipment causing shutdowns—you can take preemptive measures before problems occur. To prevent a decline in power generation, it is important not only to respond after a drop but also to manage proactively by understanding the conditions that make declines likely and preventing them in advance.

Operational cycle to prevent decline in power generation

Measures to prevent a decline in power generation are not something you do once and then finish. Solar power plants are outdoor facilities, and the seasons, weather, surrounding environment, and equipment condition are constantly changing. Even if you clean, dirt will return; even if you remove weeds, grass will grow; trees will grow; and drainage routes will change due to sediment. Equipment and cables also change condition as they age. Therefore, to maintain power generation stably, it is necessary to establish a continuous operational cycle rather than rely on one-off work.

First, it is important to establish the criteria for checking power generation. Decide how frequently you will review generation data, what level of decline will trigger an on-site inspection, and to what equipment-unit level you will make comparisons; doing so will allow you to detect anomalies earlier. Relying solely on the intuition of staff can lead to oversights and inconsistent judgments. Standardizing the clear-sky power generation curve, comparisons with equipment under the same conditions, checks of shutdown history, and the recording of on-site photographs makes it easier to identify declines in power generation at an early stage.

Next, conduct a before-and-after comparison of the measures. After performing cleaning, weeding, repairs, equipment inspections, and drainage checks, confirm how power generation changed. It is difficult to completely eliminate the influence of weather, but by comparing sunny days with one another or comparing equipment under the same conditions, you can identify consistent trends. Prioritize measures that produced large effects for future work, and if an effect is hard to see, consider other possible causes. By continuing these comparisons, you will reveal which measures tend to be most effective at each site.

To prevent a drop in power output, it is also important to prioritize. On-site there are many issues such as soiling, shading, equipment, wiring, temperature, drainage, and access routes. Treating everything with the same priority increases the workload and can lead to highly effective measures being postponed. First identify the causes that have the greatest impact on power output, then address factors that are likely to recur; progressing in that order makes it easier to sustain the work in practice.

When managing multiple power plants, it is also important to standardize management methods. If each site differs in how inspection photos are taken, how equipment numbers are recorded, and the format of anomaly reports, sharing information becomes time-consuming. Managing power generation data, on-site photos, location information, and work histories under the same approach makes it easier for stakeholders to share the current status. Efforts to prevent declines in power generation lead not only to improvements at individual sites but also to overall quality improvements in management operations.

Also, when working to increase power generation, it is important to have the attitude of applying observations made on site to the next inspection. If you record places that are prone to dirt accumulation, areas where grass tends to grow, pathways where water pools, and equipment that is prone to shutdowns, you can prioritize those items at the next check. Drops in power generation can occur suddenly, but in many cases they emerge as the accumulation of small changes. By recording those small changes and addressing them early, you can reduce power generation losses.

Summary

To prevent a decline in power generation, it is important to identify the causes of generation loss in sequence and establish a management system that makes recurrence unlikely. In solar power generation, you cannot increase the amount of solar irradiance at the site itself. However, you can bring the system closer to a state in which the received irradiance is converted into electricity without waste. To do this, you need to check generation data by time of day and by equipment, and then sequentially review panel surface soiling, shading from weeds or trees, abnormalities at the string level, faults at connection points or in cables, shutdowns or output curtailment of inverters, drainage and terrain, and inspection records.

When you feel the power output is low, rather than immediately considering major renovations, it is important to first break down the data. Check when it is low, which equipment is underperforming, and whether there is a difference compared with equipment under the same conditions. Then, by inspecting the site, you can identify areas that need cleaning, the extent of vegetation removal required, connections that need inspection, equipment that needs checking, and drainage or access routes that should be reviewed. Improving power output should be done by linking data with on-site conditions, not by relying on intuition.

Moreover, efforts to prevent a decline in power generation cannot be completed with a single operation. Even if you clean, dirt will reaccumulate; even if you remove weeds, grass will regrow; trees will grow; drainage routes will change; and equipment and wiring will change with age. Comparing power generation before and after countermeasures, keeping on-site photographs and work records, and applying them to the next inspection will increase the accuracy of improvements. To maintain stable power generation, it is essential not only to eliminate the causes but also to create a site environment and management system that are less prone to decline.

In particularly large power plants, a system for accurately sharing problem locations is necessary. If shadowed areas, rows prone to soiling, places where water accumulates, abnormal strings, repair locations, and inspection photos are recorded along with location information, stakeholders can more easily verify the same spots. By combining power generation data with on-site location information, it becomes easier to explain the priority of countermeasures and to streamline future inspections and recurrence checks.

If you want to strengthen on-site management to prevent declines in power generation with more accurate records and location information, using LRTK can also be effective. LRTK, as an iPhone-mounted GNSS high-precision positioning device, is useful for recording inspection locations within solar power plants, shadow occurrence points, poor drainage areas, abnormal equipment, repair locations, and on-site photos together with high-precision location information. Preventing declines in power generation requires accurately identifying the causes and maintaining management that can continuously verify the same locations. By using LRTK, you can record improvement points for the solar plant as on-site data, making it easier to practically proceed with maintaining and improving power generation.