Four measures to increase power generation explained by season

When you want to increase the power output of solar power generation, the same measures year-round are not always sufficient. Power output varies with seasonal conditions such as solar irradiance, temperature, solar altitude, shading, soiling, fallen leaves, snow accumulation, growth of trees and plants, typhoons, and prolonged rain. In spring, pollen and yellow sand (Asian dust); in summer, high temperatures and shading from vegetation; in autumn, fallen leaves and soiling after typhoons; and in winter, long shadows and snow accumulation tend to cause drops in power output. This article explains four seasonal measures to increase power output for practitioners searching for "how to increase power generation".

Table of Contents

• Why consider seasonal approaches to increasing power generation

• Spring measures: check for pollen, yellow sand, and post-winter dirt

• Summer measures: check for high temperatures, shading from vegetation, and output drops after intense solar irradiation

• Autumn measures: check for fallen leaves, post-typhoon effects, and dust accumulation

• Winter measures: check for low solar altitude, long shadows, and snow accumulation

• Validate seasonal measures using power generation data

• Decisions to avoid when implementing seasonal power-generation measures

• Summary

Reasons to Consider How to Increase Power Output by Season

To increase the power output of solar power generation, you must first understand how output changes by season. Solar power systems do not produce a constant amount of electricity throughout the year. Factors that raise or lower output vary by season—periods with high solar irradiance, periods of high temperatures, periods with short daylight hours, and periods with snow or fallen leaves all affect generation in different ways.

It's premature to immediately conclude an equipment malfunction when power generation falls. Low generation in winter is largely due to shorter sunlight hours and a lower sun angle. In summer, while solar irradiance is greater, increased panel temperatures can sometimes reduce output. In spring, pollen and yellow sand can have an impact, and in autumn, fallen leaves and dirt after typhoons can affect performance. In other words, the causes of reduced power generation vary by season.

Also, measures to increase power generation vary by season. In spring, checking for surface dirt becomes important; in summer, temperature losses and shadows from vegetation become challenges. In autumn, inspections for fallen leaves and after typhoons are necessary; in winter, responding to long shadows and snowfall is indispensable. Considering ways to increase power generation by season reduces unnecessary cleaning and unneeded equipment interventions, making it easier to choose measures that effectively boost power output.

For operations personnel, it's important to distinguish between seasonal variation and abnormal declines. If you judge based on a single month's low power generation, you may mistake a natural seasonal fluctuation for a fault. Conversely, if you assume it's just seasonal variation and leave it unaddressed, the actual cause could be shading, soiling, or equipment malfunction.

Therefore, to increase power generation, you need to analyze monthly generation, generation by time of day, comparisons with the same month in the previous year, and comparisons with simulation values to identify what is reducing generation in each season. Seasonal generation countermeasures are not merely annual maintenance but practical management methods to stabilize generation.

Spring measures: Check for pollen, yellow sand, and post-winter dirt

Spring is one of the seasons when solar power generation tends to increase. Daylight hours are longer than in winter, and temperatures are not as high as in summer, so under favorable conditions stable generation can be expected. However, in spring pollen, yellow sand (Asian dust), fine dust, and dirt left over from winter can easily adhere to panel surfaces and may cause a reduction in power output.

If power generation in spring doesn't increase as much as expected, the first thing to check is the condition of the panel surface. Pollen and yellow sand are fine and may not be noticeable to the eye. Even a thin accumulation on the panel surface can reduce the amount of sunlight reaching the panels and lower power output. Panels located near unpaved land, farmland, roads, or construction sites are also more likely to become covered with soil dust and other particulates.

Also, dirt that accumulated during the winter can remain until spring. In snowy regions, mud and dust can be left on panel surfaces after the snow melts. Leaves, branches, and bird droppings can also remain attached through the winter. Because spring is a season when power generation tends to increase, checking for surface dirt makes it easier to recover the power output that should be achievable.

As part of spring measures, compare monthly power generation with the same month of the previous year and with simulated values. If generation is not increasing even on sunny days, check for dirt and the condition of the equipment. If only a particular roof surface or panel row shows low output, check whether that surface faces a direction prone to pollen or dust, or whether there are trees or exhaust outlets nearby.

When performing cleaning, safety must be the top priority. Work on roofs is hazardous, so you should avoid trying to handle it in-house. You should also avoid cleaning methods that could scratch panel surfaces or otherwise adversely affect the equipment. Spring cleaning should be limited to what is necessary after confirming the relationship between soiling and any reduction in power output.

Spring is an important season for boosting annual power generation. By not overlooking the effects of pollen and yellow dust and by checking the condition of the panels after winter, you can take the first step toward increasing power output.

Summer countermeasures: check for declines from high temperatures, vegetation shade, and after intense solar radiation

Summer is often regarded as a period when solar power generation tends to increase because solar irradiance is high. However, there are summer-specific issues to watch for. The main factor is a drop in output caused by rising panel temperature. Even if solar irradiance is strong, generation efficiency can decrease when panel temperatures rise. Therefore, when summer generation does not increase as expected, it is necessary to check for losses due to high temperatures.

For panels installed on roofs, roofing materials tend to retain heat, and if ventilation behind the panels is poor, heat can become trapped. On flat roofs, using low mounting racks or having many rooftop installations nearby that disrupt airflow also makes panel temperatures more likely to rise. Even for ground-mounted installations, if grass grows and obstructs airflow it can affect the temperature environment.

In preparing for summer, check not only monthly power generation but also power generation by time of day on clear days. If output fails to reach expected levels around midday—when solar irradiance should be high—or if generation is more stable in spring and autumn, temperature-related losses may be involved. It is important to check airflow around the panels, the condition of nearby vegetation, and the equipment’s installation environment.

Also, summer is a period when vegetation tends to grow readily. Trees and plantings that cast little shadow in spring may leaf out and create shade in summer. Especially in the morning and evening, when the sun’s angle is low, tree shadows can cast long. Vegetation growth can lead not only to shading but also to impacts from fallen leaves and birds. If vegetation can be managed on-site, pruning and maintenance will be considered while monitoring their impact on power generation.

During periods of intense sunlight, also check the equipment installation environment. If power conversion equipment is located in places prone to high temperatures, you need to check the condition of the equipment and the ventilation. If power generation suddenly drops, output levels off during certain times of day, or there are differences between systems, check not only the panel surfaces but also the equipment and the wiring.

To increase summer power generation, it is important not to rely solely on high solar irradiance but to check temperature, ventilation, vegetation, and the equipment environment. While summer is a season when generation tends to increase, it is also a season in which you can easily lose potential generation due to temperature-related losses and changes in the surrounding environment.

Autumn measures: Check for fallen leaves, post-typhoon debris, and dust accumulation

Autumn is a season when the high temperatures of summer subside and power generation conditions tend to stabilize. At the same time, it is a season in which fallen leaves, post-typhoon dirt, debris blown in by strong winds, and the accumulation of dust can easily cause a decrease in power output. To increase power output, it is important to check for autumn-specific surface obstructions and changes in the surrounding environment.

Fallen leaves are a factor that deserves particular attention on roofs and land with trees nearby. Dry leaves can be blown away by the wind, but when wet from rain they can stick to panel surfaces. When they accumulate at the lower edges of panels or around the frames, they not only block sunlight but also lead to the buildup of dirt. On roofs, fallen leaves can also collect in drains and cause poor drainage.

After typhoons or strong winds, fallen leaves, branches, sand and dust, and airborne debris can remain on panels and roofs. Even if they do not directly cover the panels, their accumulation around drains and inspection walkways can affect building management and maintenance work. If electricity generation in autumn is lower than expected, check whether site conditions have changed after typhoons or strong winds.

Autumn can bring sites that are prone to the accumulation of dust and sand. On unpaved land, farmland, construction sites, and locations near roads, fine dirt can adhere to panel surfaces due to dry winds. Dirt that accumulated during the summer may remain into autumn. If rain does not completely wash the dirt away, power generation may gradually decrease.

For autumn measures, we review power generation data together with on-site conditions. If only a particular side shows low generation, check whether leaves or other debris tend to accumulate on that side. If generation drops suddenly after a typhoon, inspect the panel surfaces, wiring, equipment, and surrounding facilities. It's also important to check for any abnormalities after strong winds.

When performing cleaning or inspections, prioritize safety. Forcibly removing fallen leaves or debris blown onto the roof can be dangerous. First, assess the condition within the range that can be safely checked, and, if necessary, carry out cleaning and inspections with an appropriate team and arrangement.

Autumn is also an important time for inspections before the start of winter. If fallen leaves and dirt are left in place when winter arrives, they can combine with snow and long shadows to cause a significant reduction in power generation. By checking the surface of the panels and the area around the roof in autumn, you can more easily prevent a decrease in power generation during the winter.

Winter measures: check low solar altitude, long shadows, and snowfall

Winter is a season when photovoltaic power generation tends to decline. With shorter sunlight hours and a lower solar altitude, even under the same sunny conditions it may generate less than in summer. In addition, shadows from surrounding buildings, trees, and rooftop equipment tend to extend farther, and in snowy regions snow on panels can create periods when generation is impossible. To increase winter output, it is necessary to correctly identify the winter-specific factors that cause this reduction.

Winter shadows are a major cause of reduced power generation. Obstacles that didn’t cast shadows in summer can create long shadows in winter. In the morning, shadows lengthen to the east and in the evening to the west, and even around midday the shadows of rooftop structures, equipment, or trees can fall on the panels. If power generation is significantly lower only in winter, check not only the shorter daylight hours but also the extent and timing of the shading.

In snowy regions, power output is greatly reduced when snow covers the surface of panels. Not only the time during which snow is falling, but also the time that snow remains after a snowfall affects power output. If the panels have a low tilt, snow may be less likely to slide off. After snow slides off, it can accumulate at the bottom or in front of the panels and create additional shading.

As part of winter measures, check how much power output recovers after snowfall. If output does not return even when it is sunny, suspect residual snow on the panels, shading from piled snow, or dirt accumulation. Forcible snow removal is dangerous and can damage equipment, so decisions must prioritize safety. It is important to identify surfaces where snow tends to remain, where snow will fall off, snow storage areas, and inspection routes.

In winter, also check the condition of equipment and devices. Temperature fluctuations, snowfall, and strong winds can place stress on wiring, connection points, and the areas around equipment. If power output suddenly drops, check not only for snow or shading but also for equipment shutdowns and faulty connections. If per-system data are available, checking whether only part of the system has declined makes it easier to narrow down the cause.

Winter power generation tends to be naturally lower during the year. However, it is important to distinguish between natural declines and declines that can be improved. By checking winter shading, snowfall, lingering snow, and equipment condition, and by taking necessary measures, you can mitigate reductions in winter power generation.

Verify seasonal measures using generation data

Seasonal measures are not finished once implemented. To increase power generation, you need to check the generation data after measures are taken and verify whether there was an actual improvement. Simply having cleaned, managed trees, removed fallen leaves, or inspected equipment is not enough to determine the effect on power generation.

For verification, compare power generation before and after the measures. However, because power output is affected by weather and season, simply comparing it with the previous or following day is insufficient. Comparing it with similar sunny days, the same month of the previous year, generation during the same season, simulated values, and time-of-day generation curves makes it easier to assess the effect of the measures.

If cleaning is performed in spring, check whether power generation on sunny days has recovered after cleaning. If vegetation management or ventilation improvements are undertaken in summer, check the power output around midday in summer and the condition of the equipment. If fallen leaves or post-typhoon debris are removed in autumn, verify whether the power output of specific roof surfaces or panel rows has improved. If checks for shading or snow accumulation are carried out in winter, confirm the time periods when shading occurred and the recovery status after snowfall.

Also check not only power generation but also on-site consumption. Even if a measure increases generation, if the additional output is not used within the facility and simply becomes surplus, the improvement in implementation effectiveness will be limited. This is especially important for corporate facilities, factories, and retail stores—confirm whether there is demand during the hours when generation increases.

Keeping records of the effectiveness of seasonal measures helps with management in subsequent years. If you can identify which seasons and causes tend to reduce power generation and which measures were effective, it becomes easier to plan inspections and cleaning. Records should include the date and time of the measures, weather, on-site photos, locations inspected, changes in power generation, and soiling and shading conditions.

To increase power generation, it is important not to treat seasonal measures as a one-time effort but to continuously improve them based on data. By accumulating generation data and on-site records, you can reveal site-specific patterns of generation decline and choose more appropriate countermeasures.

Decisions to Avoid in Seasonal Power Generation Measures

What you should avoid in seasonal power generation measures is assuming a single cause for a drop in generation. If you simplistically conclude that low generation in spring is due to soiling, low generation in summer is due to temperature, and low generation in winter is due to snow, you may overlook the actual cause. While there are factors that tend to occur in each season, shading, soiling, equipment, wiring, and changes in demand can also overlap.

Also, you should avoid treating all seasonal variations as anomalies. A decrease in power generation in winter or a drop in generation during the rainy season is a natural fluctuation. You need to compare with the same month of the previous year and with simulation values to check whether output is low even after accounting for the weather. If natural variations are judged to be anomalies, unnecessary cleaning or inspections may be carried out.

Conversely, it is dangerous to simply assume it is unavoidable because of seasonal variation. Hidden within the drop in winter generation there may be issues such as shading or snow. The drop in summer generation may include temperature-related losses or equipment problems. Decreases in spring and autumn may sometimes be due to soiling or the effects of fallen leaves. It is important to separate natural variability from losses that can be corrected.

Even when carrying out seasonal cleaning and inspections, you must not neglect safety. Work on the roof, snow removal, leaf clearing, and panel cleaning all involve risks. You should avoid attempting work at height or cleaning in ways that could damage the panels just to increase power generation. Consider separately what can be safely checked and what requires professional handling.

Furthermore, it is important not to judge the effectiveness of measures solely by power generation. Even if generation increases, if only the surplus increases, the improvement in the effectiveness of the installation is limited. After implementing seasonal measures, also check self-consumption and surplus energy, and verify whether they align with the facility’s electricity usage time periods.

Seasonal measures for power generation should be carried out with an understanding of the local characteristics. Instead of simply applying generic seasonal measures, it is important to review generation data and on-site conditions and choose a management approach suited to that site.

Summary

When considering ways to increase power generation by season, the points to check differ for spring, summer, autumn, and winter. In spring, check for pollen, yellow sand, and dirt accumulated over winter. In summer, check for output reduction due to high temperatures, shading from vegetation growth, and high-temperature conditions of equipment. In autumn, check for fallen leaves, dirt after typhoons, and accumulation of dust and particulates. In winter, check for long shadows caused by the low sun angle, snowfall, lingering snow, and the condition of equipment during the winter.

An important point in season-specific measures is not to attribute reductions in power generation solely to the season. There are natural seasonal variations, but some causes within them may be addressable. Check monthly generation, generation by time of day, and generation by installation surface, and understand in which seasons, at which times of day, and over what range the generation is falling.

In spring, check the panels for surface dirt and perform safe cleaning and inspections as needed. In summer, check for temperature loss and shading from vegetation, and manage ventilation and the surrounding environment. In autumn, check for fallen leaves and conditions after typhoons, and carry out inspections before winter. In winter, check for long shadows and the duration of power generation stoppage due to snowfall, and consider countermeasures with safety as the priority.

After implementing measures, verify their effectiveness using generation data. Record how generation changed after cleaning, after shading countermeasures, after snowfall, and after equipment inspections, and use this information to inform measures for the next season. By checking not only generation but also self-consumption and surplus electricity, you can determine whether improvements in generation lead to practical operational benefits.

Furthermore, accurate on-site information is indispensable for precisely implementing seasonal power generation measures. If the installation area, rooftop equipment, obstructions, trees, site boundaries, orientation, slope, inspection access routes, and potential connection points can be accurately identified, it becomes much easier to organize seasonal issues such as shading, soiling, snow accumulation, ventilation, and maintainability.

If you want to accurately record on-site installation areas, obstacles, trees, rooftop equipment, site boundaries, orientation, slopes, inspection access routes, and so on, and advance measures to increase power generation by season, using LRTK, an iPhone-mounted GNSS high-precision positioning device, is effective. If you can obtain highly accurate local position information, it becomes easier to identify causes of shading, locations prone to dirt, areas where snow or fallen leaves tend to remain, feasible installation ranges, wiring routes, and maintenance access paths, and to proceed seamlessly from seasonal on-site checks and simulation comparisons to post-installation performance management. To put seasonal methods for increasing power generation into practice, it is important not just to rely on desk-based generalities but to accurately grasp the site and respond appropriately to the factors that reduce generation in each season.