5 Things to Check Before Increasing Power Output | Tips for Identifying Causes

Table of Contents

• Why identifying the root cause is necessary before increasing power output

• Check item 1: Review generation data by time of day and by equipment

• Check item 2: Isolate weather, solar irradiance, and seasonal variations

• Check item 3: Confirm the impact of panel surface soiling and shading

• Check item 4: Inspect for abnormalities in connectors, cables, and conversion equipment

• Check item 5: Look for recurrence factors from drainage, terrain, and inspection records

• How to proceed to turn root cause identification into power output improvements

• Summary

Why Identifying the Cause Is Necessary Before Increasing Power Output

When you want to increase the energy production of a solar power system, the first thing you should do is not to immediately start cleaning or repairs. Even if you feel that generation is low, not increasing as expected, or lower than the previous year, the cause may not be a single one. Dirt on the panel surface, shadows from weeds or trees, faults in connection points, stoppage of inverters or other conversion equipment, output curtailment, temperature rise, poor drainage, lack of inspection records, and so on — multiple factors may be combining to reduce generation.

For practitioners searching "how to increase power generation", it's important to consider the idea of increasing power generation as an effort to reduce generation losses. In solar power generation, you cannot increase the solar irradiance itself on-site. However, you can move closer to a state in which the solar irradiance received is converted into electricity with as little waste as possible. In other words, improving power generation means finding where the power that should be generated is being lost and reducing those wastes.

If countermeasures are taken without identifying the cause, the priority of tasks can be misplaced. For example, even if panels appear dirty, if the main cause of reduced power generation is shading in the morning and evening, cleaning alone will not lead to sufficient improvement. Conversely, even if there seems to be no major visible abnormality, a close look at the power generation data may reveal that only some strings are consistently underperforming. Such partial anomalies are easy to overlook if you only look at the overall monthly power generation.

Before trying to increase power output, what you should check is when, where, and how the output is falling. Whether it is low only in the morning, only in the evening, the midday peak isn't reaching expected levels, it becomes unstable after rain, only specific equipment is underperforming, or the entire plant is underperforming, the causes you should suspect will differ. The more accurately you can identify the cause, the easier it becomes to determine which of cleaning, weeding, repairs, equipment inspections, or drainage measures should be prioritized.

Also, identifying the cause is not something you do just once. A solar power plant is an outdoor facility, and its condition changes with the seasons, weather, surrounding environment, and equipment aging. Even if you clean it, dirt will return; even if you remove weeds, they will grow back; trees grow; and drainage paths change. Therefore, to consistently increase power generation, it is necessary to operate in a cycle of assessing the current situation, isolating causes, implementing countermeasures, verifying effectiveness, and updating records.

Check Item 1: View power generation data by time period and by facility

Before attempting to increase power generation, the first thing you should check is the power generation data. If you only look at monthly or annual power generation figures, you won’t know when or where generation losses are occurring. Even if nothing looks abnormal on a monthly basis, there may be periods during sunny days when output drops, or certain pieces of equipment may consistently underperform. The starting point for improving generation is not the overall total but examining how declines occur by time of day and by individual equipment.

Checking by time of day makes the direction of the cause easier to see. 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 or effects from surrounding terrain. If the midday peak does not reach expected levels, candidates include soiling of the panel surface, temperature rise, limitations of power conversion equipment, output curtailment, or equipment shutdowns. If, even on clear days, the generation curve suddenly drops during the day, it is necessary to cross-check shutdown and alarm histories with the timestamps.

When comparing at the equipment level, it is important to compare units under the same conditions. If you simply compare equipment that differ in orientation, tilt, number of panels, shading conditions, or connection configuration, you may mistake normal differences for abnormalities. If a specific area is consistently lower compared with adjacent rows or equipment with the same orientation, suspect localized soiling, partial shading, connection faults, cable damage, or equipment-side faults.

Pay attention to how the power output declines. If it drops suddenly, possible causes include equipment shutdown, wire disconnection, poor connections, or the appearance of obstructions. If it decreases gradually, accumulation of dirt, growth of weeds or trees, worsening site conditions due to poor drainage, or aging of the equipment may be involved. Reading the pattern of the decline lets you narrow down the locations that should be checked on site.

When viewing power generation data, it is important, whenever possible, to use clear-sky days as the baseline. On cloudy or rainy days, power output can fluctuate greatly due to moving clouds, making it difficult to distinguish such variability from equipment faults. With the generation curve from a clear-sky day, features such as shading, shutdowns, curtailment, and string faults are easier to identify. When identifying causes before attempting to increase output, it is important not only to note that output is low, but also to carefully examine the timing, extent, and persistence of the decline.

Checklist Item 2: Separate weather, solar radiation conditions, and seasonal differences

When you feel that power generation is low, the things you should check before suspecting equipment failure are the weather, solar irradiance conditions, and seasonal variations. Because photovoltaic power generation is strongly affected by the amount of sunlight, during periods with many cloudy or rainy days the power output will drop even if there is no problem with the equipment. If you compare only the monthly generation with the same month in the previous year or with the previous month and immediately conclude that the equipment is faulty, the main cause may actually have been differences in weather.

At the same time, you must avoid overlooking a real anomaly by attributing it to weather. If the entire plant is declining uniformly in line with regional weather, it is likely that solar irradiance conditions are having a significant effect. However, if only part of the plant is underperforming while other equipment in the same plant is operating normally, or if there is a clear difference compared with equipment under similar conditions, weather alone cannot explain it. In such cases, you should check for dirt, shading, poor connections, equipment shutdowns, output curtailment, and so on.

To separate causes related to weather from those related to equipment, it is effective to compare sunny days with other sunny days or with days that have similar weather. Cloudy or rainy days have large fluctuations in power generation, making it difficult to discern the characteristics of anomalies. By selecting and checking power generation curves from sunny days, you can more easily identify the impact of shadows that cause drops at the same time every day, string anomalies that show lower output only on specific equipment, and equipment shutdowns that cause drops for only a certain period.

Seasonal differences are also an important consideration. In winter, the sun’s altitude is lower, causing shadows from nearby trees and terrain to stretch farther. In summer, although solar irradiance is stronger, panel temperatures and the temperatures around equipment rise, which can make it harder for output to increase. During periods of heavy rain, monthly power generation tends to be lower, and after strong winds or heavy rain you should pay attention to fallen leaves, sediment, deposits, poor drainage, and the condition around cables.

The key to identifying causes is to separate natural weather-driven variability from generation losses that can be corrected on site. When you find a day with low generation, check not only that day’s weather but also differences from equipment under the same conditions, the generation curve by time of day, on-site photos, and equipment history. By understanding the impact of weather and focusing on causes that can be improved, you can more easily reduce unnecessary work.

Inspection Item 3: Confirm the effects of dirt and shadows on the panel surface

Before increasing power output, it is essential to check the effects of dirt and shadows on the panel surface. Because solar panels generate electricity by receiving sunlight on their surface, dirt and deposits reduce the light reaching the cells. The way panels become soiled varies with site conditions and includes soil dust, pollen, yellow sand, bird droppings, fallen leaves, sap, dust from nearby construction, road-derived dust, and salt-containing deposits that tend to adhere in coastal areas.

Particular attention should be paid to band-like dirt that remains along the lower edge of panels and near the frame. It's often assumed that rain will wash it away naturally, but in reality the flow of rainwater can collect dirt at the lower edge and leave it there. On panels with a shallow slope, water does not drain easily and dirt tends to accumulate. Even dirt that is not noticeable from a distance may affect power generation if it covers part of a cell.

Local deposits such as bird droppings and fallen leaves should not be overlooked. Unlike dirt that spreads thinly across the entire surface, these locally cover specific areas more heavily and hinder power generation by creating partial shading. If only some installations show reduced output, focus inspections on the panel surfaces around those installations. Rows near trees, around structures where birds tend to perch, rows that are often downwind, and areas near unpaved walkways are more likely to accumulate dirt and deposits.

Also important to check at the same time are shadows caused by weeds, trees, and structures. Sources of shading include weeds, trees, fences, utility poles, surrounding buildings, mounting racks, adjacent panel rows, monitoring equipment, and other items. Because shadows move with the time of day and the seasons, the absence of visible shading during an inspection does not necessarily mean there is no problem. If power generation is low in the morning, check the on-site conditions in the morning; if it is low in the evening, check for evening shadows.

When performing cleaning or weeding, prioritize locations that have the greatest impact on power generation. If equipment with low power output coincides with areas of dirt or shading, the priority for countermeasures should be high. Conversely, even if dirt or weeds are conspicuous, if the main cause of reduced power generation is equipment shutdowns or connection faults, cleaning or weeding alone may not lead to improvement. When identifying the cause, it is important to cross-check not only on-site visual observations but also power generation data.

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Checklist item 4: Check for abnormalities in connectors, cables, and conversion devices

Before trying to increase power generation, it is also necessary to check for abnormalities in the paths that carry the electricity out. Even if the solar panels are receiving sunlight normally, if there are problems with connections, cables, or power conversion equipment, the generated electricity cannot be fully extracted. String-level generation differences, loose terminals, poor contacts, damage to cable sheathing, moisture ingress, animal damage, equipment shutdowns, and output curtailment are important causes of reduced power generation.

When checking for string-level anomalies, it is fundamental to compare units under the same conditions. If you simply compare units that differ in number of panels, orientation, tilt, shading conditions, or connection configuration, you may mistakenly judge normal differences as abnormalities. Check whether any string is consistently lower compared with adjacent rows or installations with the same orientation. If only a specific string is low, candidate causes include panel soiling, partial shading, poor connections, cable damage, or equipment-side problems.

Signs that connection or cable faults are suspected include when only specific equipment shows low power output, when abnormalities tend to appear after rain, when power generation suddenly drops, or when output fluctuates unstably. Cables are easily affected by on-site environmental conditions, and in areas with heavy weeds it becomes difficult to inspect their condition. In locations with poor drainage, moisture and puddles can affect connection points. At plants where animals can easily enter, cable damage can also occur.

Also check the shutdown history and alarm history of the conversion equipment. If the equipment that converts the generated electricity has stopped or its output is being limited, power output will not increase even if solar irradiance is sufficient. Even short shutdowns can cause significant losses if they occur during daytime when generation is high. If the generation curve on clear days is plateauing, also check for output curtailment, equipment capacity limits, temperature rise, and measurement anomalies.

When inspecting electrical equipment, safety must be the highest priority. Even if you want to increase power output, on-site personnel should avoid forcibly touching connection points or probing inside equipment to make a judgment. Gather and organize which equipment is showing abnormalities, the time they occurred, changes in power output, on-site photographs, and the surrounding environment, and, when necessary, arrange for professional inspections. At the stage of identifying the cause, it is important to make clear where and what kind of anomaly is suspected.

Checklist Item 5: Identify causes of recurrence from drainage, topography, and inspection records

The final items to check before increasing power generation are drainage, terrain, and inspection records. Merely inspecting the panels and equipment may not reveal the root causes of reduced power generation. Locations where water tends to accumulate, where sediment flows in, paths that easily become muddy, slope failures, scour around the mounting racks, and places where cables are prone to exposure can directly or indirectly cause reductions in power generation. These are important factors that lead to soiling, weed growth, connection faults, and reduced accessibility for inspections.

In areas where puddles remain after rain, weeds are more likely to grow. When weeds grow, they cast shade, worsen ventilation, and make inspections more difficult. Muddy walkways can slow work and reduce the frequency of cleaning and weeding. Where sediment flows in, it can accumulate under panels and around cables, causing dirt and damage. If the same problems recur in the same places despite cleaning and weeding, drainage or topography issues should be suspected.

When checking topography and drainage, inspecting the site not only in fine weather but also after rain is effective. Determine where water flows in, where it accumulates, and where it drains out. Recording puddles, sediment deposits, dense vegetation, subsidence of pathways, and changes to slopes will reveal locations prone to recurrence. If drainage problems are left unaddressed, dirt and weeds will return, resulting in the same power generation losses occurring repeatedly.

Inspection records also help pinpoint causes. If you can check whether dirt has occurred in the same location in the past, whether grass has grown in the same row, or whether the same equipment has experienced shutdowns, you can narrow down the causes more quickly. When records are insufficient, you cannot learn the cause even if the same problem recurs, and responses tend to be ad hoc. To increase power generation, it is essential to accumulate inspection results as information that can be used for future improvements.

By investigating the factors that cause recurrence, measures shift from temporary tasks to continuous improvement. Rather than merely cleaning soiled areas, check why those locations become dirty easily. Rather than just mowing grass, look into why grass tends to grow in those spots. Rather than only repairing connection points, examine underlying factors such as moisture, drainage, and exposed cables. With this perspective, it becomes easier to sustain improvements in power generation over the long term.

How to Turn Root-Cause Identification into Power Generation Improvements

To turn root-cause identification into power generation improvements, it is important to translate the information you have verified into a prioritized list of countermeasures. After finding underperforming equipment in the generation data, isolating weather and seasonal effects, and confirming on site the soiling, shading, connections, equipment, and drainage, the next step is to decide on measures in order of their impact on generation. Treating all issues with the same priority can increase workload and cause high-impact improvements to be postponed.

First prioritize the equipment and time periods where a decline in power generation can be clearly confirmed. For example, if only a specific row shows lower output even on sunny days and that row has concentrated soiling on the lower edge or bird droppings, give cleaning a higher priority. If generation is low only in the morning and shadows from trees or grass on the east side can be observed, prioritize shade mitigation. If only a particular string is low and no soiling or shading is found, proceed to inspect connection points, cables, and the equipment side.

After countermeasures are implemented, check how the power generation changed. After cleaning, weeding, repairs, equipment inspections, and drainage checks, record the power generation before and after the work, on-site photos, the scope of work, and the weather conditions. It is difficult to completely eliminate the influence of weather, but by comparing sunny days with each other or comparing with installations under the same conditions, you can identify consistent trends. Prioritize measures that had a large effect for future work, and if an effect is not apparent, consider other possible causes.

When multiple people are responsible for management, it is also important to be able to share the exact same location. In large power plants, similar rows and equipment are lined up, so photos alone can make it difficult to identify the location. By recording equipment numbers, location information, photos, and work histories together, field staff, managers, inspectors, and repair personnel can more easily confirm the same location.

The key to linking root-cause identification to improved power generation is not to treat the problems you find as one-off incidents. If you record locations prone to soiling, times when shadows are likely to occur, places where water accumulates, sections of walkways that are prone to deterioration, and equipment that tends to show abnormalities, you can check them before power generation drops significantly. To raise power generation consistently, it's important not only to respond after a decline but also to identify conditions that make declines likely in advance and take countermeasures.

Summary

Items to check before increasing power generation are: power generation data, weather and solar irradiance conditions, dirt and shading on panel surfaces, abnormalities in connections and conversion equipment, drainage and terrain, and inspection records. In solar power generation, you cannot increase the amount of solar irradiance at the site itself. However, you can improve power generation by bringing the system closer to a state that converts the received irradiance into electricity without waste. Therefore, it is important to first correctly identify the cause of any decline in power generation.

When you feel that power generation is low, rather than immediately performing cleaning or repairs, it is important to first separate and examine the data. Determine when it is low, which equipment is underperforming, and whether there is a difference compared with equipment under the same conditions. With that information, an on-site inspection will clarify where cleaning is needed, what area should be weeded, which connections should be checked, which equipment should be inspected, and which drainage or traffic routes should be reconsidered. The more accurate the cause identification, the less likely measures to improve power generation will fail.

Efforts to increase power generation cannot be completed with a single operation. Even after cleaning, dirt will re-accumulate; even after weeding, grass will grow back; trees will grow; and equipment and wiring will change condition with age. Comparing power generation before and after countermeasures, keeping on-site photos and work records, and using them for the next inspection will improve the accuracy of improvements. To raise power generation stably, it is essential not only to remove the causes but also to create a site environment and management system that make the same causes less likely to occur.

Especially at large power plants, a system for accurately sharing problem locations is important. If you record rows prone to soiling, locations where shadows occur, places where water accumulates, abnormal strings, repair locations, cleaning areas, and inspection photos together with location information, stakeholders can more easily confirm the same location. By combining power generation data with on-site location information, it becomes easier to explain the priorities for cleaning, weeding, and repairs, and it also streamlines confirmation of recurrence on subsequent inspections.

When you want to accurately identify causes based on on-site data before increasing power output, utilizing LRTK is also effective. As an iPhone-mounted GNSS high-precision positioning device, LRTK is useful for recording inspection points within solar power plants, areas prone to soiling, locations where shadows occur, areas with poor drainage, faulty equipment, repair locations, cleaning areas, and on-site photos together with high-precision location information. By keeping the results of cause identification with location data, it becomes easier to pursue power output improvements based on on-site data rather than relying on intuition.