8 On-Site Improvements to Increase Power Generation | Reducing Solar Power Loss Factors

Table of Contents

• On-site improvements to increase power generation start with identifying loss factors

• On-site improvement 1: Check the time periods when generation is decreasing using power generation data

• On-site improvement 2: Narrow down the range of decline by comparing with equipment under the same conditions

• On-site improvement 3: Reduce dirt and deposits on panel surfaces

• On-site improvement 4: Reduce shading from weeds, trees, and structures

• On-site improvement 5: Check for abnormalities in strings, connection points, and cables

• On-site improvement 6: Review shutdowns, curtailment, and the temperature environment of conversion equipment

• On-site improvement 7: Improve drainage, terrain, and inspection routes

• On-site improvement 8: Prevent recurrence using inspection records and location information

• Operations to translate on-site improvements into increased power generation

• Summary

On-site improvements to increase power generation begin with identifying loss factors

When you want to increase the power generation of a solar PV system, the first thing you need to do is not to add more equipment but to confirm whether the existing equipment is delivering its intended generation capacity. In solar power generation, you cannot increase the amount of solar irradiance on site. You cannot increase the number of sunny days or change the sun’s altitude by season. However, you can move closer to a state in which the received irradiance is converted into electricity with as little waste as possible. In other words, in practical terms, increasing generation means identifying the loss factors that cause you to miss out on power that should be generated, and reducing those losses through on-site improvements.

There is not a single cause for a drop in power generation. Dust on the panel surface, pollen, bird droppings, fallen leaves, soiling at the lower edge, shading from weeds or trees, faults at connection points, cable damage, stoppage of conversion equipment, output curtailment, temperature rises, poor drainage, and insufficient inspection records are some of the multiple factors that can combine to reduce power output. Moreover, these loss factors do not necessarily manifest as major failures. They often show up as small changes, such as a slightly depressed generation curve on sunny days, lower output in only part of the same equipment group, or output dropping only in the morning and evening.

For practitioners searching for "how to increase power generation", it is important not to decide on countermeasures based only on problems noticed on site. Cleaning panels because they are dirty, removing weeds because vegetation has grown, or suspecting the equipment side because the devices look old—such judgments are necessary in some situations. However, if the main cause of the power generation decline lies elsewhere, those actions will not lead to sufficient improvement. Even if you clean the panels, power generation is unlikely to recover if morning and evening shadows remain, and even if you remove weeds, daytime generation will not increase if the inverters continue to experience brief intermittent shutdowns.

To effectively carry out on-site improvements, it is necessary to link power generation data, site photos, inspection results, and work history to isolate the causes. Check when generation is low, which equipment is underperforming, whether there is a difference compared with equipment under the same conditions, whether it is low even on sunny days, and whether it becomes unstable after rain. Based on that, review soiling, shading, connections, power conversion equipment, drainage, and inspection routes. A low generation result alone does not tell you where to start. Finding loss factors for each site and improving them in order of their impact on generation will lead to long-term increases in power output.

Site Improvement 1: Use power generation data to identify time periods with decreased output

The first step in on-site improvement is to check the power generation data before visiting the site. If you only look at monthly or annual generation, you can't tell when the output drops. Even when generation is generally low, the causes to suspect differ depending on whether it's low only in the morning, the midday peak fails to develop, it drops only in the evening, or there's a sudden dip during the daytime. To increase generation, it is important to look at generation curves by time of day rather than at aggregate totals.

If the morning ramp-up is slow, suspect shadows from trees, slopes, weeds, nearby structures, or adjacent equipment on the east or southeast side. If generation falls early in the evening, check shadows on the west or southwest side, surrounding topography, and tree growth. If the midday peak does not extend, candidates include dirt on the panel surfaces, temperature rise, limits of power conversion equipment, output curtailment, equipment shutdowns, and string-level anomalies. If the generation curve suddenly drops midway, it is necessary to cross-check the stop history and alarm history of the power conversion equipment with the timestamps.

When examining power generation data, use the generation curve from sunny days as a reference whenever possible. On cloudy or rainy days, power output can fluctuate greatly due to cloud movement, making it difficult to determine whether the cause is equipment malfunction or weather. If you see a drop at the same time period on sunny days every time, you should suspect fixed shading or restrictions on the equipment side. Conversely, if the entire plant shows a similar decline, it is more likely that solar irradiance conditions or the weather are having a major impact.

If you enter a site without checking the time of day, inspections become broad and shallow. If a site has low power generation in the morning, checking it only at noon will not reveal the morning shadows. If a site’s output drops in the evening, you may overlook the cause unless you observe the evening shadows and the surrounding terrain. Simply aligning the timing of on-site checks with the power generation data improves the accuracy of identifying loss factors. For site improvements aimed at increasing power generation, the starting point is to use data to clarify, “when is it low.”

On-site Improvement 2: Narrow the Range of Degradation by Comparing Equipment under the Same Conditions

To identify the causes of low power generation, the total value for the entire plant alone is not sufficient. Even if there appears to be no major anomaly at the plant level, power generation may be low only for certain rows, certain strings, or areas connected to particular power conversion equipment. Such partial generation losses are hard to notice in monthly totals, yet if they persist over long periods they can result in significant losses.

When making comparisons, it is important to look at installations under the same conditions. If you simply compare installations that differ in azimuth, tilt, number of panels, shading conditions, or connection configuration, you may mistakenly interpret normal differences as abnormalities. The purpose of comparison is to find locations that are consistently lower in output among installations that should have similar generation. If only a portion is lower compared with adjacent rows or installations with the same orientation, suspect localized soiling, partial shading, connection faults, cable damage, or abnormalities on the power conversion equipment side.

When comparing equipment under the same conditions, also verify whether the decrease is temporary or persistent. If the difference occurs on only one day, it may be caused by clouds, temporary shading, fallen leaves, or similar factors. If the same area is lower on multiple sunny days, it is more likely that there is a persistent issue on site. If the same string or the area connected to the same device is low every time, you should prioritize an on-site inspection.

Once you have narrowed the range of the drop, ensure the exact location can be identified on site. At sites where equipment numbers or row numbers are hard to read, even if an anomaly is detected in the data it can take time to find it on site. A photo alone may not convey the location. For improving power generation, enabling stakeholders to accurately share the location is as important as finding the anomaly. By narrowing the drop range with generation data and making sure the location can be verified on site, decisions about cleaning, weeding, repairs, and equipment checks can be made more quickly.

Workplace Improvement 3: Reduce Dirt and Deposits on Panel Surfaces

Dirt and deposits on panel surfaces are a common cause of solar power loss. Because solar panels generate electricity by receiving sunlight at their surface, soiling reduces the light reaching the cells. The type of soiling varies by site environment, such as soil dust, pollen, yellow sand, bird droppings, fallen leaves, sap, dust from nearby construction, road-derived dust, and salt-containing deposits that readily adhere in coastal areas. Even light soiling, if spread over a wide area, can affect power generation, and localized deposits can act as strong shading even over small areas.

Particular attention should be paid to the band-like dirt that remains along the bottom edge of panels and around the frames. It is often assumed that rain will wash it away naturally, but in fact the flow of rainwater can collect dirt at the lower edge and leave it there. On panels with a shallow tilt, water drains poorly and dirt tends to accumulate. Even dirt that is not noticeable from a distance can affect power output if it covers part of a cell. During on-site inspections, it is necessary to carefully examine not only the overall coloration of the panel but also the lower edge, the corners, and the areas around the frame.

Localized deposits such as bird droppings and fallen leaves should not be overlooked. Unlike dirt that spreads thinly over the entire surface, these cover specific areas more thickly and hinder power generation by causing partial shading. Rows near trees, around structures where birds tend to perch, leeward rows, and areas near unpaved walkways are more prone to dirt and deposits. If only some installations have lower power output, prioritize inspecting the panel surfaces around those installations.

When deciding whether to clean, check if the soiling corresponds to the area of reduced power generation. If equipment with low power output overlaps with areas where soiling is noticeable, cleaning should be given a high priority. Conversely, if soiling is visible but does not correspond with the area of decreased power generation, you need to check for other causes such as shading, connections, power conversion equipment, or temperature conditions. Carry out cleaning in a way that does not damage the equipment, and record photos before and after the work, the cleaned area, weather conditions, and changes in power generation to make it easier to assess how much the soiling affected power output.

On-site improvement 4: Reduce shading from weeds, trees, and structures

To increase power generation, suppressing the occurrence of shadows is essential. Because solar panels generate electricity by receiving sunlight, even partial shading of a panel can reduce power output. Causes of shading include weeds, trees, fences, support posts, nearby buildings, mounting frames, adjacent panel rows, monitoring equipment, and other factors. Since shadows move depending on the time of day and season, the absence of visible shading at the moment of inspection does not necessarily mean there is no problem.

Weeds are a common cause of losses on site. Even if they are not a problem in winter or immediately after installation, they can grow rapidly from spring through summer and cast shadows on the lower edges of panels and on the front rows. Even if the plants do not touch the panels, low sun angles in the morning and evening cause shadows to extend far. Furthermore, when weeds become overgrown they impair ventilation, block inspection walkways, and make it difficult to inspect around equipment. Because this affects not only power generation but also maintainability, weed management is a fundamental part of on-site improvement.

Shadows from trees are also a factor that tends to become problematic during long-term operation. Even trees that had little impact at the time of installation can grow over several years and reduce power generation. Trees located on the south, east, and west sides in particular cast shadows on the panels depending on the time of day. At power plants near forests or on 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 is a large dip in the mornings and evenings, it is necessary to check the trees and the terrain together.

When checking shadows, it is important to inspect the site at the times when power generation data shows decreases. If output is low in the morning, check morning on-site conditions; if it is low in the evening, observe evening shadows. Even if there is no problem at noon, large shadows can appear in the morning and evening. Also, something that is not an issue in summer may cast much longer shadows in winter because the sun’s altitude is lower. Recording the times shadows occur, their sources, and which equipment they affect makes it easier to decide on measures such as weeding, pruning, or rearranging the layout.

On-site Improvement 5: Check for Abnormalities in Strings, Connectors, and Cables

Not only the panel surface and shading, but the electrical pathways that carry the electricity also have a major impact on power generation. Even if solar panels are generating properly, faults in strings, connection points, or cables can prevent the generated power from being fully extracted. Loose terminals, poor contacts, damaged cable insulation, moisture ingress, animal damage, damage during grass-cutting operations, and age-related deterioration can all lead to reduced power output.

When checking for anomalies at the string level, compare strings under the same conditions. If you simply compare strings that differ in panel count, orientation, tilt, shading conditions, or connection configuration, you may misinterpret normal differences as anomalies. Check whether any string is consistently lower compared with adjacent rows or strings with the same orientation. If only a specific string is low, possible causes include soiling, partial shading, poor connections, cable damage, panel defects, or issues on the inverter/power-conversion equipment side.

Pay attention to how power generation differences appear. If output is consistently lower than the surroundings even on sunny days, dirt, degradation, or poor connections may be suspected. If it is lower only in the morning and evening, check for the effects of shading. If abnormalities tend to appear after rain, moisture ingress or the condition around connection points may be involved. If it becomes unstable during periods of high temperature, poor contacts or thermal conditions are also possible causes. Combining the power output waveform with on-site conditions makes it easier to narrow down the cause.

When checking connection points and cables, prioritize safety above all. Even if you want to increase power generation, on-site personnel should avoid forcibly touching connection points or the interior of equipment to make judgments. First, organize the equipment suspected of being abnormal, the time of occurrence, changes in power output, on-site photos, and the surrounding environment. If necessary, arrange for a professional inspection so that the cause can be identified more easily while maintaining safety. Because abnormalities in cables and connections can be related to the surrounding environment—such as vegetation, drainage, and animal intrusion—it is important not to stop at repairs but to verify the conditions that could cause recurrence.

On-site Improvement 6: Review Shutdowns, Suppression Measures, and Thermal Environment of Conversion Equipment

The cause of low power output is not limited to the panels and wiring. If the equipment that converts the generated electricity is stopped or its output is being limited, power output will not increase even when solar irradiance is sufficient. For on-site improvements, it is essential to check the conversion equipment’s operating status, shutdown history, alarm history, and whether output curtailment is in effect.

When reviewing downtime history, confirm which equipment stopped, when it stopped, and for how long. Even short outages can cause significant losses if they occur during the daytime when generation is high. If stops and recoveries repeat during the day, they may not stand out in the monthly total but can still result in lost generation. Whether only a specific device has stopped or multiple devices have stopped simultaneously will change the suspected causes.

Also check for output curtailment and saturation. When the top of the power generation curve flattens during clear weather, candidates include output limits of the conversion equipment, equipment capacity ceilings, temperature rise, input-side insufficiency, and measurement anomalies. It is not necessarily equipment failure, but if it occurs during periods when generation output is significantly affected, it should be checked as a priority. Make a determination by combining historical records, the generation curve, and differences from facilities under the same conditions.

Temperature conditions and ventilation should not be overlooked. While solar power generation is easier when solar radiation is stronger, higher panel temperatures or higher temperatures around equipment can sometimes make it harder for output to increase. If, on a clear summer day, generation does not increase as expected, the midday peak is muted, or systems become unstable during times when equipment tends to get hot, check the thermal environment. Conditions such as weeds growing under panels or around equipment, accumulated debris, or poor ventilation can affect power generation and the detection of abnormalities. Creating an environment in which equipment can operate stably is one on-site improvement that directly leads to increased power generation.

On-site Improvement 7: Organize drainage, terrain, and inspection routes

When implementing on-site improvements to increase power generation, it is necessary to look not only at panels and equipment but also at the plant’s overall drainage, terrain, and inspection routes. These may appear unrelated to power output, but in fact they are key factors that lead to soiling, weeds, connection failures, and reduced inspectability. Areas where water tends to accumulate, places where sediment flows in, paths that easily become muddy, slope failures, scour around mounting structures, and locations where cables are likely to be exposed can repeatedly cause reductions in power generation.

Areas where puddles remain after rain are prone to weed growth. When weeds grow, they cast shadows, reduce ventilation, and make inspections more difficult. In places where sediment flows in, dirt tends to accumulate at the lower edges of panels and around cables. If the same problems recur in the same places despite cleaning and weeding, it is necessary to check drainage and terrain issues.

When checking topography and drainage, on-site inspections after rain as well as during clear weather are effective. Determine where water flows in from, where it pools, and where it drains out. By recording puddles, sediment accumulation, overgrown vegetation, pathway subsidence, and changes to slopes, you can identify locations prone to recurrence. If drainage problems are left unaddressed, the same power generation losses will be repeated multiple times.

Maintaining inspection routes is also important. If grass has overgrown so you cannot pass, the ground is too muddy to approach, equipment numbers are hard to read, or photos alone do not convey the location, the detection and sharing of abnormalities will be delayed. Even if you identify low-output equipment from the data, if it is difficult to reach the corresponding location on site, corrective measures will be delayed. To increase power generation, keeping the power plant in a condition that makes inspections easy is also an important on-site improvement.

Improvements to drainage and inspection access routes may not immediately translate into increased power generation. However, over the long term they help reduce the recurrence of soiling, the proliferation of weeds, poor ventilation, overlooked cable abnormalities, and delayed inspections. By not only performing immediate cleaning and repairs but also creating a site environment that makes the same causes less likely to recur, it becomes easier to continuously reduce the factors that cause losses in solar power generation.

On-site Improvement 8: Prevent Recurrence with Inspection Records and Location Information

Maintaining inspection records is essential to continue site improvements that increase power generation. Even if dirt, shadows, anomalies, or poor drainage are found on site, if the exact location is not shared, it takes time to implement countermeasures or perform rechecks. This is especially true at large power plants, where similar rows and equipment are lined up and photos alone can make locations hard to identify. Linking inspection results to location information and managing them makes the practical work of site improvements easier to carry out.

What you should record are the locations of equipment with low power output, rows that are prone to soiling, spots where shadows occur, places where water accumulates, locations suspected of poor connection, points where conversion equipment has stopped, repaired areas, and the extent of cleaning or weeding carried out. Keeping photos, date and time, equipment numbers, work performed, details of abnormalities, response status, and whether reinspection is necessary will be useful for the next inspection. If you add too many items to record it will be hard to maintain in the field, so start by ensuring that, when reviewed later, it is clear where and what happened.

Linking power generation data with on-site photographs makes it easier to determine causes. If the locations of low-output equipment overlap with areas where shadows occur or where drainage is poor, the basis for countermeasures becomes clear. If power generation at a cleaned location improves, you can conclude that dirt had a significant impact at that site. If morning and evening generation improves after weeding, it is highly likely that shadows from weeds were the cause. Keeping records speeds up decision-making in future cases.

If insufficient record-keeping is left unaddressed, the same problems will recur. Even if there are patterns—grass growing in the same spot every year, dirt accumulating in the same row, the same passage becoming muddy after rain, or the same equipment experiencing stoppages—without records the next response will be improvised. In on-site improvement, instead of investigating the cause from scratch each time, it is important to use past records to narrow down where to check.

Record the power generation after countermeasures as well. After cleaning, weeding, repairs, equipment inspection, and drainage checks, record the pre- and post-operation power generation, on-site photos, scope of work, and weather conditions. Prioritize measures that had a large effect in future operations, and suspect other causes for measures that had little effect. Repeating this process provides the foundation for continuously reducing factors that cause solar power loss, rather than leaving power generation improvement as a temporary effort.

Operational practices to connect on-site improvements with increased power generation

To turn on-site improvements into increased power generation, it is necessary to operate inspections, countermeasures, performance verification, and record updates as a single continuous process. Find locations with low power generation using data, then check for dirt, shading, connections, power conversion equipment, and drainage on site and implement the necessary measures. After that, verify how power generation has changed and retain the results as records that can be used for future decision-making. Without this flow, cleaning, weeding, and repairs become one-off tasks, making it difficult to accumulate improvement effects.

First and foremost, it is important to prioritize on-site improvements. Rather than inspecting all locations at the same density, prioritize equipment where a drop in power generation has been confirmed, areas with output lower than comparable equipment under the same conditions, rows prone to soiling or shading, and connection points or areas around converters where anomalies are suspected. By checking locations that have a large impact on power generation first, it becomes easier to find causes that lead to improvements even within limited inspection time.

Next, verify the effectiveness of the countermeasures. If dirt was cleaned, compare the power generation and photos before and after cleaning. If shadows were removed, check whether the morning and evening power generation curves have improved. If ventilation around the power conversion equipment was improved, look for changes in shutdowns or alarms, or in the daytime power generation curve. If the effectiveness of the measures is clear, you can determine the priority of future inspections and work more accurately.

To maintain increased power generation, it is important not only to respond after output drops but also to identify in advance the conditions that are likely to cause drops. If you record rows that tend to accumulate dirt, times of day when shadows are likely to occur, places where water pools, spots where walkways are prone to damage, and equipment that is prone to abnormalities, you can inspect them before generation falls significantly. Ideally, on-site improvements should be carried out not as responses after a decline in generation, but as operations to prevent generation decline in the first place.

Summary

In on-site improvements aimed at increasing power generation, the important thing is to isolate the causes of solar losses in order and address them starting with the areas that have the greatest impact on output. In photovoltaic systems, it is not possible on site to increase the incident solar irradiance itself. However, you can improve generation by bringing the system closer to a state that converts the received irradiance into electricity without waste.

To do this, it is necessary to check in sequence the generation data, dirt on panel surfaces, shadows from weeds and trees, strings and connections, conversion equipment, drainage, and inspection records.

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 the output is low, which equipment is underperforming, and whether there are differences compared with equipment under the same conditions. By then inspecting the site, you will clearly identify where cleaning is needed, the extent of weeding required, which connections should be inspected, which devices need checking, and which drainage or access routes should be reconsidered. For improving power generation, it is crucial to base decisions on linking data with on-site conditions, not on intuition.

Also, site improvements cannot be completed in a single operation. Even if you clean, dirt will return; even if you remove weeds, grass will grow back; trees will continue to grow; and equipment and wiring will change condition over time. By comparing power generation before and after countermeasures, keeping on-site photos and work histories, and using them for the next inspection, the accuracy of improvements increases. To reliably raise power generation, 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.

In particularly large power plants, a system for accurately sharing problem locations is essential. If dirt-prone rows, locations where shadows occur, places where water accumulates, abnormal strings, spots suspected of connection faults, locations where power conversion equipment has stopped, cleaning areas, repair locations, and inspection photos are recorded together with location information, stakeholders can more easily confirm the same spots. By combining generation data with on-site location information, it becomes easier to explain the prioritization of cleaning, weed removal, repairs, and specialist inspections, and subsequent recurrence checks can be made more efficient.

If you want to continuously manage on-site improvements to increase power generation by each cause of solar power loss, using LRTK is also effective.

As an iPhone-mounted GNSS high-precision positioning device, LRTK is useful for recording inspection locations within a solar power plant, areas prone to soiling, locations where shadows occur, areas with drainage issues, abnormal equipment, connection points and areas around equipment, cleaning areas, repair locations, and on-site photos together with high-precision location information. By keeping the results of the eight site improvement measures with location information, it becomes easier to pursue power generation improvements based on field data rather than on intuition.