7 Ways to Improve Solar Power Generation Output｜How to Prevent Efficiency Decline

Table of Contents

• Improving solar power generation begins with identifying the causes of efficiency decline

• Item 1: Check generation data by time of day and by individual equipment

• Item 2: Separate solar irradiance conditions from weather variations

• Item 3: Manage panel surface soiling and deposits

• Item 4: Reduce shading from weeds, trees, and structures

• Item 5: Check for abnormalities in strings, connection points, and cables

• Item 6: Review stoppages, curtailment, and temperature conditions of power conversion equipment

• Item 7: Organize drainage, site topography, and inspection records to prevent recurrence

• Operational points for continuing improvement of solar power generation

• Summary

Improving Solar Power Generation Starts with Identifying the Causes of Efficiency Decline

When you want to improve solar power generation output, the first thing you need is not to add more equipment but to check whether the existing equipment is performing at its intended capacity. In solar power generation, you cannot increase the amount of solar irradiance on-site. However, you can get closer to a state in which the received sunlight is converted into electricity with as little waste as possible. In other words, in practical terms, improving generation output means finding the causes that are letting potentially producible electricity slip through the cracks and taking steps to prevent efficiency losses.

There is not a single cause for reduced power generation. Dirt on panel surfaces, deposits such as bird droppings and fallen leaves, shading from weeds and trees, abnormalities at the string level, faults at connection points, cable damage, shutdowns of conversion equipment, output curtailment, temperature increases, poor drainage, site conditions that make inspection difficult, and other factors often combine to lower power output. Even when there appears to be no obvious problem visually, checking power generation data by time of day or by individual equipment can reveal that only certain parts are continuously underperforming.

For practitioners searching for "how to increase power generation," the important point is not to judge solely by the result that generation is low. Depending on whether it is low only in the morning, only in the evening, the midday peak fails to rise, it becomes unstable after rain, or only specific equipment shows low output, the causes to check will differ. Whether you should clean, remove weeds, inspect connections, check equipment history, or review drainage and topography should be decided by combining data with on-site conditions.

Also, improving power generation is not something that can be completed with a single action. Even if you clean, dirt will return; even if you remove weeds, grass will grow back; trees will continue to grow; and drainage routes will change due to sediment. Equipment and wiring also change condition over time. Therefore, to improve power generation, it is important not only to remove causes temporarily but to establish a management system that prevents the same declines from recurring. Below, we explain seven items effective for improving solar power generation, presented in a sequence that is easy to check on site.

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

The first step in improving solar power generation is to examine the generation data in detail. If you only look at monthly or annual output, you won’t know when, where, or how generation losses are occurring. Even if nothing looks abnormal on a monthly basis, there may be cases where output drops only during certain hours of sunny days, or where a particular piece of equipment continues to produce lower output than its surroundings.

Checking by time of day makes it easier to identify the likely direction of the cause. If power generation is low in the morning, shadows from trees on the east side, slopes, surrounding structures, or adjacent equipment may be involved. If it is low in the evening, check for western shadows and the influence of surrounding topography. If power generation does not increase around noon, candidates include soiling of the panel surface, temperature rise, limitations of conversion equipment, output curtailment, or equipment shutdown. If there is a sudden drop in the power curve even on a clear day, it is necessary to cross-reference shutdown history and alarm history with the time.

When comparing equipment units, it is important to compare installations under the same conditions. If you simply compare systems with different numbers of panels, orientations, tilts, shading conditions, or connection configurations, you may mistake normal differences for abnormalities. If only a portion is consistently lower compared with adjacent rows or installations with the same orientation, it is more likely that the cause is on-site rather than the weather. Suspect soiling, shading, poor connections, cable damage, or equipment-side faults, and raise the priority of on-site verification.

There are sudden drops and gradual declines in power output. Sudden drops may be related to equipment shutdowns, line breaks, poor connections, or the emergence of obstructions. Gradual declines may be related to the accumulation of dirt, the growth of weeds or trees, environmental deterioration due to poor drainage, or the aging of equipment. By interpreting the pattern of decline, you can narrow down the locations to inspect on site.

If you walk the site without looking at power generation data, inspections tend to be broad and shallow. If output is low in the morning, focus on morning shadows; if it doesn’t rise at noon, focus on dirt, equipment, and temperature; if it’s low in the evening, focus on shadows on the west side—this improves the accuracy of inspections. Improving power generation doesn’t start with cleaning or repairs; it starts with using data to identify where generation losses are occurring.

Item 2: Separate solar radiation conditions from weather variability

When you notice that power generation is low, before immediately concluding there is an equipment fault you need to separate out solar irradiance conditions and weather differences. Solar power generation is heavily influenced by the amount of sunlight, so during periods with frequent clouds or rain output can decline even if there is no problem with the equipment. If you compare only the monthly generation with the same month of the previous year or with the previous month and simply judge it as a decrease, the actual main cause may have been differences in the weather.

On the other hand, you must also avoid overlooking genuine anomalies by attributing them to the weather. If the entire plant declines uniformly in line with local weather, the impact of irradiance conditions is likely significant. However, if other equipment in the same region or within the same plant is operating normally while only part is underperforming, the weather alone cannot explain it. In that case, you should check for soiling, shading, poor connections, shutdown of power conversion equipment, output curtailment, and so on.

To distinguish solar irradiance conditions, comparing clear-sky days with each other, days with similar weather, and generation trends within the same region is helpful. On cloudy or rainy days, generation fluctuates greatly due to moving clouds, making it difficult to separate from equipment anomalies. By selecting and comparing generation curves from clear-sky days, features such as shading, shutdowns, curtailment, and string faults become easier to identify. It is important not to look only at days with low generation, but to compare them with days under similar conditions.

Seasonality should also be considered. In winter, the sun’s altitude is lower, and shadows from surrounding trees and terrain tend to extend farther. In summer, although solar radiation is stronger, panel and equipment temperatures rise, which can make power output harder to increase. During periods of heavy rain, monthly generation tends to be lower, and after strong winds or heavy rain attention is needed to deposits, sediment, poor drainage, and the condition around cables.

As a countermeasure, you should record natural fluctuations due to weather separately from generation losses that can be improved on-site. For days with low generation, check the weather, the generation curve, comparisons with other facilities, and the on-site conditions together. Creating a system that, while understanding the impact of weather, does not overlook equipment-side abnormalities is fundamental to improving solar power generation.

Item 3: Manage dirt and deposits on panel surfaces

Contamination and deposits on the panel surface are a common cause of reduced efficiency in solar power generation. Because solar panels generate electricity by receiving solar radiation at their surface, when dirt adheres the light reaching the cells is reduced. Soil dust, pollen, yellow sand (Asian dust), bird droppings, fallen leaves, sap, dust from nearby construction, road-derived dust, and salt-containing deposits that readily adhere in coastal areas — the type and extent of soiling vary greatly depending on site conditions.

What you should pay particular attention to is the band-like dirt that remains along the lower edge of the panel and around the frame. It is often assumed that rain will wash it away naturally, but in reality the flow of rainwater can concentrate the dirt at the lower edge and leave it there. On panels with a gentle tilt, water does not drain easily and dirt tends to accumulate. Even dirt that is not noticeable from a distance can potentially affect power generation if it covers part of a cell.

Accumulations such as bird droppings and fallen leaves should not be overlooked. Unlike uniform soiling, these build up heavily in specific spots and create partial shading. If only some equipment is producing less power, inspect the surface of the panels in that area. Rows near trees, around structures where birds tend to perch, leeward rows, and areas near unpaved walkways tend to be prone to soiling and deposits.

When cleaning is carried out, it is practical to prioritize the areas that have the greatest impact on power generation. Instead of cleaning all panels at the same frequency, focus inspections on rows where soiling is concentrated, installations where a drop in power output has been confirmed, areas where soiling along the lower edges is noticeable, and locations with heavy bird droppings or leaf litter. Comparing photos and power output before and after cleaning makes it easier to understand how much the soiling at that site was affecting generation.

However, cleaning must be carried out in a way that does not damage the equipment. Avoid vigorously scrubbing with hard tools, performing sudden work during periods when panels are at high temperatures, or working without confirming the electrical safety of the equipment. Cleaning to improve power generation is not a cosmetic task but maintenance intended to restore the panels' light-receiving condition and ensure the equipment can be used stably over the long term.

When addressing soiling, it is important not only to remove dirt but also to understand the causes that make soiling likely. Check whether dust is easily raised from unpaved pathways, whether surrounding trees tend to shed leaves or produce sap, whether there are structures that attract birds, or whether panel slopes cause rainwater to drain poorly. If you can identify locations where soiling recurs, it becomes easier to adjust cleaning frequency and inspection timing and to prevent declines in efficiency.

Item 4: Minimize shading from weeds, trees, and structures

Managing shading is essential for improving solar power generation. Because solar panels generate electricity by receiving sunlight, even a partial shadow on a panel can reduce its output. Causes of shading include weeds, trees, fences, utility poles, nearby buildings, mounting structures, adjacent rows of panels, monitoring equipment, and others. Shadows move with the time of day and the seasons, so the fact that no shadow was visible at the time of inspection does not necessarily mean there is no problem.

Weeds are a common cause of on-site power generation losses. Even if there is no problem in winter or immediately after installation, they can grow rapidly from spring to summer and cast shadows on the lower edge of panels or the front row. Even when vegetation does not touch the panels, shadows extend far at the low sun angles of morning and evening. Furthermore, when weeds become overgrown, ventilation worsens, inspection walkways get blocked, and it becomes harder to inspect around equipment. Because it affects not only power generation but also maintainability and safety, weed management is fundamental to improving power output.

Shadows from trees are a factor that easily becomes 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 located near forests or slopes, the terrain height and tree height can combine to create long shadows in winter. If power generation is low only in winter, or there are large drops in the mornings and evenings, it is necessary to check both the trees and the terrain together.

When checking shadows, aligning power generation data with the time of the on-site inspection makes it easier to identify the cause. If power output is low in the morning, check the on-site conditions in the morning; if it is low in the evening, inspect the evening shadows. Even if an inspection at noon shows no problem, large shadows can appear in the morning or evening. Also, even if there is no problem in summer, shadows can lengthen in seasons when the solar altitude is low. Shadows need to be managed not as a single moment but as something that changes with time and season.

When carrying out weeding or pruning, prioritize the areas that have the greatest impact on power output. Rather than uniformly tidying the entire site, concentrate on the area in front of the panels, around equipment, inspection walkways, and the directions in which shadows are likely to extend. After the work, record whether the shading has actually been eliminated, whether inspections have become easier, and whether ventilation has improved. Because shading problems tend to recur, do not treat the task as a one-time operation; annual management that assumes the regrowth of grass and trees is important.

Shadows from surrounding structures should not be overlooked. Adding new equipment within the power plant, or installing fences, signs, or surveillance poles can cast 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. Not only reducing existing shadows, but also operating in a way that does not create new ones is important to prevent efficiency loss.

Item 5: Check for abnormalities in strings, connection points, and cables

To improve solar power generation, it is important to check for abnormalities not only in the plant-wide figures but also at the finest possible unit level. Even if overall generation does not appear to have a major problem, only some strings may be underperforming. Such localized declines, if left unaddressed, will continue to cause generation losses over a long period. To increase output, do not be reassured by the overall average; you need to identify differences at the equipment unit or string level.

When comparing at the string level, it is fundamental to compare items under the same conditions. If you simply compare those with different numbers of panels, orientations, tilts, shading conditions, or connection configurations, you may mistake normal differences for anomalies. Compare with adjacent rows or installations with the same orientation to check whether any are consistently lower. If only a specific string is low, possible causes include dirty panels, partial shading, poor connections, cable damage, or equipment-side problems.

Pay attention to how the anomaly appears. If it is consistently lower than the surroundings even on sunny days, dirt or connection problems are suspected. If it is lower only in the morning and evening, check for the effects of shadows. If anomalies tend to appear after rain, moisture ingress or the condition of the connections may be involved. If it becomes unstable 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 connections and cables are also an important cause of reduced power generation. There are many factors that can impede the flow of electricity, including loose terminals, poor contact, damage to cable sheathing, moisture ingress, animal damage, damage during grass‑cutting operations, and age‑related deterioration. Because these can be difficult to detect from appearance alone, it is important to narrow down the abnormal range using power generation data and make a judgment by cross‑checking with site photos and work records.

Inspections of electrical equipment are carried out with safety as the top priority. Rather than having on-site personnel touch equipment unnecessarily to make a judgment, we document which equipment is showing abnormalities, the time of occurrence, changes in power output, on-site photographs, and the surrounding environment, and, when necessary, escalate to specialist inspections. Even if connection points are repaired, if conditions remain—such as water pooling in the same spot, overgrown vegetation, cables that are easily exposed, or easy access for animals—the issue may recur.

Even a small difference in power generation can lead to large losses if it continues over a long period. Furthermore, if poor connections or cable damage are involved, it can create risks not only to power output but also to safety. Rather than assuming there is no problem because the overall power generation hasn’t dropped significantly, management that detects localized abnormalities early is necessary.

Item 6: Review shutdown, suppression, and temperature environment of conversion equipment

The causes of low power generation are not limited to the panels and wiring. If the equipment that converts the generated electricity is stopped or its output is being limited, generation will not increase even if solar irradiation is sufficient. To improve solar power generation, it is essential to check the conversion equipment’s operating status, stoppage history, alarm history, and whether output curtailment is in effect.

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

If output curtailment is occurring, generation can level off even on sunny days. If the top of the power generation curve appears flat, check curtailment records and operational data. However, a flat curve does not necessarily indicate output curtailment. Similar patterns can result from equipment capacity limits, temperature rise, soiling, shading, or measurement anomalies. Do not judge based only on the generation curve; it is important to isolate the cause by combining equipment records with on-site conditions.

Temperature conditions are another item to review. Solar power generation is easier when solar irradiance is strong, but when panel temperature or the temperature around equipment rises, output tends to decrease. If generation does not increase as expected on a clear summer day, you need to check not only the irradiance but also the effects of temperature rise and poor ventilation. If weeds are thriving under the panels, there are grasses or obstructions around equipment, or dust and deposits are making heat dissipation difficult, these can affect the increase in power generation.

The area around power conversion equipment should be kept in a condition that is easy to inspect, allows airflow, and enables immediate confirmation of any abnormalities. If the area around the equipment is overgrown with grass, access paths are narrow, or there is a large accumulation of debris, both the operating environment and the ease of inspection are reduced. In practical work to improve power generation, it is important, along with checking the equipment itself, to prepare the surrounding environment so the equipment can operate stably.

Cross-checking drops in power generation with shutdown times is also essential. If the time when generation fell matches the time of an alarm or shutdown, it becomes easier to identify the cause. Conversely, if there are no abnormalities in the equipment records, suspect other causes such as solar panels, wiring, shading, soiling, or solar irradiance conditions. Choosing countermeasures based on generation data and equipment history, rather than on guesswork, is important to prevent an efficiency decline.

Item 7: Organize drainage, topography, and inspection records to prevent recurrence

To improve solar power generation output, it is necessary to check not only the panels and equipment but also the plant’s overall drainage, terrain, and inspection access routes. Areas where water tends to accumulate, locations where sediment flows in, pathways prone to becoming muddy, slope failures, scour around mounting structures, and places where cables are likely to be exposed can cause reduced power generation either directly or indirectly. Poor drainage and terrain changes may at first appear to be unrelated to generation output, but they are important factors that lead to soiling, weeds, connector faults, and deterioration of inspectability.

In areas where puddles remain after rain, weeds are more likely to grow. When weeds grow, they cast shade, reduce ventilation, and make inspections more difficult. Muddy walkways slow down work and can reduce the frequency of cleaning and weeding. 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 those carried out in fine weather. Identify where water flows in from, where it pools, and where it drains away. Recording puddles, sediment accumulation, vegetation overgrowth, path settlement, and changes to slopes will reveal locations prone to recurrence. If dirt or weeds recur in the same places despite cleaning or weeding, you should suspect problems with drainage or terrain rather than just surface-level causes.

Inspection routes also affect improvements in power generation. Locations that are hard to inspect tend to delay the discovery of abnormalities. If grass has grown so that you cannot pass through, if the ground is muddy and you cannot get close, if equipment numbers are hard to read, or if it is difficult to share the location of a fault, on-site response takes more time. Even if you identify low-performing equipment from the data, improvements will be delayed if it takes time to reach the relevant spot on site.

Organizing inspection records is also important. Even if dirt, shadows, abnormalities, or poor drainage are found on-site, if the locations are not shared accurately, it takes time to implement countermeasures or to re-check. Especially at large power plants, rows and equipment that look similar mean that photos alone can make it difficult to identify locations. If you record, together with location information, the positions of underperforming equipment, locations where shadows occur, rows prone to dirt, areas where water accumulates, spots where connection failures occurred, places that were repaired, and areas where cleaning or weeding was carried out, you can overlay power generation data with on-site conditions for review.

As records accumulate, weaknesses specific to each power plant become apparent. If you can identify patterns—grass growing in the same spot every year, dirt accumulating in the same row, the same pathway becoming muddy after rain, or the same equipment causing stoppages—you can take preventative measures before problems occur. To prevent declines in efficiency, it is important not only to respond after a decline has happened but also to manage proactively by understanding the conditions that make declines likely.

Operational Points to Continuously Improve Solar Power Generation

Improving solar power generation output cannot be accomplished with a single action. Solar power plants are outdoor facilities, and seasons, weather, the surrounding environment, and equipment conditions are constantly changing. Even if you clean them, dirt will return; even if you remove weeds, grass will grow back; trees grow; and drainage channels change due to sediment. Equipment and cables also change condition over time. Therefore, to achieve a stable improvement in generation output, it is necessary to establish ongoing operational practices rather than relying on one-off work.

First, the important thing is to establish criteria for checking power generation. Deciding how often to review generation data, what level of decline will trigger an on-site inspection, and down to which equipment unit comparisons should be made will enable earlier detection of anomalies. Relying only on staff intuition leads to oversights and inconsistent judgments. Standardizing the generation curve on sunny days, comparisons with equipment under the same conditions, verification of shutdown history, and the recording of on-site photos helps stabilize the accuracy of power output improvement efforts.

Next, compare conditions before and after the measures. After performing cleaning, weeding, repairs, equipment checks, and drainage checks, verify how the power output changed. It is difficult to completely eliminate the influence of weather, but by comparing sunny days with each other or comparing facilities under the same conditions, you can identify certain trends. Prioritize measures that produced large effects for future work, and if an effect is not apparent, consider other causes. By continuing such comparisons, you will see which measures tend to be effective at each site.

When improving power output, it's also important not to try to solve all issues at once. At a site there are many problems — soiling, shading, equipment, wiring, temperature, drainage, site access and workflow, and insufficient record-keeping. Treating everything with the same priority can increase the workload and cause high-impact measures to be postponed. First identify the causes that have the greatest impact on power generation, then address the factors that are prone to recur; proceeding in that order makes it easier to sustain the work in practice.

When you manage multiple power plants, it is also important to standardize your management methods. If each site has different ways of taking inspection photos, different notations for equipment numbers, and different formats for abnormality records, sharing information takes time. Managing power generation data, on-site photos, location information, and work histories with a consistent approach makes it easier for stakeholders to share the situation. Improving power generation is not only achieved through measures at individual sites but also leads to overall improvements in the quality of management operations.

For operations personnel aiming to improve solar power generation output, it is as important to avoid repeating the same causes as it is to identify them. By recording locations prone to soiling, time periods when shading is likely to occur, areas with poor drainage, and equipment that tends to develop anomalies, you can take measures before output drops significantly next time. Ideally, improving generation output should shift work from responding after declines to work that prevents those declines in the first place.

Summary

To improve solar power generation output, it is important to identify the causes of efficiency decline in sequence and reduce generation losses. 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 so, you need to check generation data by time of day and by equipment unit, separate irradiance conditions from weather differences, and sequentially review panel surface soiling, shading from weeds and trees, anomalies at the string level, faults in connections and cables, stoppages or output curtailment of power conversion equipment, temperature conditions, drainage and topography, and inspection records.

When you feel that power generation is low, rather than immediately considering major renovations, it is important to first separate and examine the data. Check when the output is low, which equipment is underperforming, and whether there is a difference compared with equipment under the same conditions. Based on that, an on-site inspection will clarify the places that need cleaning, the areas that require weeding, the connections that need inspection, the equipment to be checked, and the drainage or movement lines that should be reviewed. Improving power generation should be done by linking data with on-site conditions, not by intuition.

Also, improving solar power generation is not something that can be completed with a single operation. Even if you clean, dirt will return; even if you remove weeds, grass will grow back; trees will grow; drainage routes will change; and equipment and wiring will change condition with age. By comparing generation before and after measures, keeping on-site photographs and work records, and using them for the next inspection, the accuracy of improvements increases. To maintain generation stably, 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 is needed to accurately share problem locations. If you record the locations where shadows occur, soiling-prone rows, spots where water accumulates, abnormal strings, repair locations, and inspection photos along with their location information, stakeholders can more easily confirm the same sites. Combining generation data with on-site location information makes it easier to explain the prioritization of countermeasures and streamlines future inspections and checks for recurrence.

If you want to improve solar power generation with more accurate on-site records and location information, using LRTK is also effective. LRTK, an iPhone-mounted GNSS high-precision positioning device, is useful for recording inspection locations, locations where shadows occur, drainage failure locations, abnormal equipment, repair locations, and on-site photos within a solar power plant together with high-precision location information. For improving power generation, it is important to accurately identify causes and to manage so that the same locations can be continuously rechecked. By using LRTK, you can retain the seven items of verification as field data, making it easier to carry out practical improvement activities to prevent efficiency degradation.