7 Seasonal Measures to Increase Power Generation | Tips to Prevent Declines in Summer and Winter

Table of Contents

• Seasonal measures to increase power generation require anticipating the causes of decline

• Seasonal measure 1: Use annual power generation data to identify periods prone to decline

• Seasonal measure 2: Check for contamination from spring pollen, yellow sand, and dust

• Seasonal measure 3: Manage weeds and shading early from the rainy season through summer

• Seasonal measure 4: Prevent output declines caused by high summer temperatures and poor ventilation

• Seasonal measure 5: Check for soil, fallen debris, and inadequate drainage after typhoons and heavy rain

• Seasonal measure 6: Reassess autumn leaf fall and tree shading

• Seasonal measure 7: Check for declines caused by low winter solar altitude, frost, and snow accumulation

• Record keeping to sustain seasonal measures

• Summary

Seasonal measures to increase power generation require anticipating the causes of decline

When considering increasing the output of a solar power system, it is important to manage it with seasonal variations in mind. Solar power systems are outdoor equipment and are continuously exposed to solar irradiance, ambient temperature, rain, wind, vegetation growth, fallen leaves, frost, snowfall, and changes in the surrounding environment. The soiling that tends to become a problem in spring, the high temperatures and weeds that tend to become problematic in summer, and the shading and frost that tend to become problematic in winter each have different causes and countermeasures. If you repeat the same inspections year-round, you may overlook season-specific generation losses.

For practitioners searching "how to increase power generation", it is important not to attribute declines in power generation solely to the weather. Certainly, generation falls during periods with many clouds or heavy rain. In winter it is more affected by shorter sunlight hours and lower solar altitude, and in summer high temperatures can make it difficult for output to increase. However, even within natural seasonal variations there are generation losses that can be reduced through site management. Dirt on panel surfaces, shadows from weeds, growth of trees, poor drainage, inadequate ventilation around equipment, and the accumulation of sediment or fallen leaves are examples that can potentially be improved through on-site inspection and countermeasures.

A common pitfall with seasonal measures is scrambling to respond only after power generation has declined. If you wait until dirt has accumulated in spring to think about cleaning, until grass has grown in front of panels in summer to remove it, until after a typhoon when output has fallen to inspect the site, or until shadows lengthen in winter to notice the impact of trees, generation losses will occur first. To increase power generation, it is important to anticipate the causes likely to arise each season and check them before output drops significantly.

Also, for seasonal measures, combining power generation data with on-site records is essential. If you only look at monthly generation figures, it becomes difficult to distinguish whether the variation is a natural fluctuation due to weather or a site-related problem. By checking generation curves on sunny days, comparisons with systems under the same conditions, time-of-day drops, on-site photos, and work histories together, it becomes easier to identify the causes of seasonal declines. Seasonal measures to increase power generation involve grasping trends in generation losses throughout the year and implementing the necessary actions at the necessary times.

Seasonal Measure 1: Identify periods when output is likely to decrease using annual power generation data

The first step in seasonal countermeasures is to review the annual power generation data to identify which times of year generation tends to decline. Because generation varies by season, simply comparing with the previous month can lead to incorrect conclusions. There are periods when output naturally falls due to solar irradiance and weather, but if only certain equipment shows declines at the same time every year, seasonal, site-specific factors may be involved.

For example, if power generation tends to be suppressed in spring, pollen, yellow dust, particulates, bird droppings, or dirt from nearby construction may be adhering to the panel surface. If some installations are underperforming from around the rainy season into summer, weed growth or shading in front of the panels may be involved. If the midday peak does not increase on sunny summer days, check for rising temperatures, poor ventilation, and the equipment’s surrounding environment. If output declines in autumn, inspect for fallen leaves, tree branches, or debris accumulated after typhoons. If there are large drops in the morning and evening during winter, suspect shading caused by the lower sun angle, frost, snowfall, or the influence of surrounding terrain.

When reviewing annual data, check not only the entire plant but also at the equipment level and the string level. If the whole plant is low, weather may be a major factor, but if only certain rows or certain pieces of equipment are low at the same time each year, a local cause is more likely. If a specific area is lower compared with equipment that has the same orientation, the same tilt, and a similar number of panels, you should prioritize on-site inspection.

Also, when working with annual data, comparing clear-sky days with each other is important. In months with a lot of rain or cloud cover, power generation drops even if the equipment has no fault. Therefore, choose clear-sky days whose weather conditions are as similar as possible and compare the shapes of the generation curves. Whether the morning ramp-up is slow, the midday peak fails to extend, or the evening drop-off comes early will reveal the likely direction of the cause. For seasonal countermeasures, looking at time-of-day generation curves rather than monthly totals is the starting point for improving power output.

Checking the annual power generation data makes it easier to plan inspection schedules. You can decide seasonal inspection items—for example, check for dirt in spring, weeds before summer, ventilation and temperature in summer, drainage and fallen debris after typhoons, fallen leaves in autumn, and shadows and frost in winter. Rather than responding after power generation has declined, inspecting before periods when generation is likely to fall makes it easier to minimize power generation losses.

Seasonal Measures 2: Check for soiling from spring pollen, yellow sand, and dust

Spring is a season when you should pay attention to dirt on panel surfaces. Pollen, yellow sand, soil dust, ambient dust, bird droppings, and the like can accumulate, making it easy for thin, widespread surface dirt and buildup at the lower edges of panels to occur. It is often assumed that rain will wash them away naturally, but in reality the flow of rainwater can gather dirt at the panel lower edge and leave it there. On panels with a gentle tilt, water does not drain easily, and banded dirt can potentially affect power generation.

Spring dirt may be inconspicuous from a distance. Even if the whole surface only looks slightly whitish, widespread deposition can reduce the amount of light received. In particular, the lower edges of panels, areas near the frame, and corners tend to retain dirt, so they should be carefully checked during inspections. Local deposits such as bird droppings can act as strong shadows even over a small area, so if only some equipment shows reduced power output, inspect those areas more closely.

When judging whether to clean, it's important to look not only at whether they appear dirty but also at the relationship with power generation data. Even if generation is sluggish in spring, it may simply have been due to bad weather. Compare days with clear skies as much as possible, and check whether only specific rows or installations under the same conditions are producing less. If the low-producing equipment coincides with areas where dirt is conspicuous, you can more confidently expect improvements from cleaning.

When cleaning is performed, it is essential to choose methods that do not damage the equipment. Avoid vigorously scrubbing with hard tools, rubbing while sand or small stones remain, carrying out sudden work during periods when the panels are at high temperatures, or skipping safety checks for electrical equipment. Cleaning to increase power generation is not a cosmetic task to make the panels look clean, but a maintenance operation to restore their light-receiving condition and ensure long-term, stable use of the equipment.

With spring soiling countermeasures, records before and after cleaning are also important. If you keep records of the cleaning scope, the types of soiling, before-and-after photos, changes in power generation, and weather conditions, you can determine how much spring soiling affected power output at that site. If the effect is visible, you can inspect at the same time the following year; if the effect is small, you can check for shading or equipment-related causes. For seasonal measures, it is important not to treat spring soiling as a one-off cleaning, but to incorporate it into the inspection plan for the following year.

Seasonal Measure 3: Manage Weeds and Shade Early from the Rainy Season into Summer

From the rainy season through summer, you need to be mindful of shadows caused by weed growth. Even in locations that posed no problem in winter or early spring, periods of continuous rain can suddenly accelerate grass height, creating shadows at the lower edge or front of the panels. Even if the grass does not touch the panels, shadows can extend far at the low sun angles of morning and evening and may reduce power generation. To increase power generation, it is important to manage the vegetation before shadows appear, rather than waiting until the grass has fully grown.

In weed control, rather than just uniformly grooming the entire site, prioritize locations that are likely to affect power output. Pay particular attention to the area in front of the solar panels, near the lower edges, between rows, at the base of slopes, along fences, around equipment, and inspection walkways. If power output data shows declines in the morning or evening, check for grass in the directions that would cast shadows at those times. Inspecting the site only at noon may cause you to overlook shadows that extend in the morning and evening.

During grass-cutting work, pay attention to contact with cables and connection points. In areas where weeds have grown thick, the condition of cables, conduits, junction boxes, and beneath the mounting racks becomes difficult to see. Working under those conditions can lead to accidentally damaging cables. To ensure that weed-control measures intended to increase power generation do not cause other power-generation problems, it is important to check cable locations and the areas around equipment before starting work.

From the rainy season through summer, weeds also affect ventilation. When vegetation becomes overgrown beneath panels and around equipment, airflow can be impeded and heat may become trapped. Although solar power generation is easier with stronger solar radiation, higher panel and equipment temperatures can make it harder for power output to increase. Even if weeds are not casting direct shade, they can still impact energy yield and maintainability by causing poor ventilation and making inspections more difficult.

To sustain weed control, record the locations and times when vegetation tends to grow. If you notice patterns—such as weeds growing in the same spots every year, the same areas becoming dense after rain, or plant height increasing only below slopes and in places where water collects—you can anticipate future inspections and weeding schedules. For seasonal measures to increase power generation, it is important not only to cut weeds but also to manage vegetation height so as to maintain heights that are less likely to cause generation losses.

Seasonal Measure 4: Preventing Power Output Decline from High Summer Temperatures and Poor Ventilation

Although summer often brings stronger solar radiation and thus higher expected power generation, attention must be paid to output reductions caused by high temperatures and to deterioration of the environment around equipment. Solar power generates electricity from sunlight, but when panel temperatures rise, output may fail to increase as much. If, despite clear skies, generation does not reach expected levels, the midday peak is muted, or only certain installations perform worse in summer, you should check the temperature conditions and for poor ventilation.

On-site in summer, check the ventilation conditions beneath the panels. If weeds are overgrown, debris has accumulated under the panels, or grass is dense between rows, airflow can be impeded. Even if the weeds are not directly casting shadows, poor ventilation can cause heat to build up and potentially affect power generation. For summer measures, it is important to consider grass height management and ensuring ventilation at the same time.

The environment around power conversion equipment is also important. If there is grass, fallen leaves, soil or debris, or other obstacles around the equipment, visual inspections can become difficult and ventilation and heat dissipation may be affected. If output becomes unstable during times when the equipment tends to heat up, alarms or shutdowns occur frequently, or the power generation curve plateaus during the daytime, check the equipment history together with the surrounding environment. Improving not only the equipment itself but also creating an environment in which the equipment can operate stably leads to increased power generation.

In summer, output curtailment and equipment capacity limits can also affect the power generation curve. If the top of the generation curve appears flat, it does not necessarily indicate a fault. Multiple causes can be considered, such as output limitation, temperature rise, insufficient input, panel soiling, shading, and measurement anomalies. It is necessary to compare sunny days and check differences against equipment under the same conditions, equipment history, and the on-site environment.

Summer heat countermeasures are not measures to completely lower the ambient temperature. On-site actions can reduce unnecessary heat buildup and enable earlier detection of abnormalities. Managing the grass under panels, improving visibility around equipment, keeping walkways clear, removing accumulated debris, and checking the power generation curve and equipment history are practical improvements. To increase summer power generation, it is important not to overlook temperature and ventilation, precisely because solar radiation is stronger during this period.

Seasonal Measure 5: Check for landslides, fallen objects, and drainage failures after typhoons and heavy rain

After typhoons or heavy rain, the causes of reduced power generation can increase all at once. Fallen leaves and branches from strong winds, flying debris, inflows of soil and sediment, changes to drainage routes, puddles, moisture around cables, and dirt on panel surfaces are more likely to occur. If power generation is low after a typhoon or heavy rain, it is necessary to check for abnormalities remaining on site, not just assume it was simply due to bad weather.

First, what I want to check is the condition of the panel surfaces and lower edges. If fallen leaves, small branches, dust, or mud splashes carried by strong winds adhere to the panels, the amount of light they receive may decrease. Dirt can also accumulate at the lower edges after rainwater flows. In rows close to trees or in locations exposed to wind, leaves and branches can concentrate. If power generation data shows a decrease only in specific rows, focus on inspecting the panel surfaces in that area.

Next, check drainage and topography. Places where puddles remain after heavy rain, where sediment flows in, pathways prone to becoming muddy, and slopes likely to collapse can be recurring causes of reduced power generation. Areas where water accumulates tend to promote weed growth, which can later lead to shading and poor ventilation. If sediment builds up around cables, inspections become more difficult and there is a risk of overlooking damage or abnormalities.

After a typhoon, also check the condition of surrounding structures and trees. Branches may have broken and be casting shadows, fences or supports may have tilted and created new shadows, and fallen leaves may be blocking drainage paths. Even if there is no obvious damage on site, if there is a sudden drop in the power generation curve or a decline in specific equipment, it is necessary to check for flying debris, shading, and the condition of connections.

In inspections after typhoons and heavy rain, recording on-site photos and location information is particularly useful. If you record places where water has pooled, where sediment has flowed in, where falling debris has concentrated, and where drainage is clogged, it will be easier to take countermeasures before the next heavy rain. For seasonal measures to increase power generation, it is important not only to check for abnormalities after disasters but also to identify recurrence factors so that the same problems do not repeat in the same locations.

Seasonal Measure 6: Reassess Fallen Leaves and Tree Shadows in Autumn

Autumn is a season to be mindful of fallen leaves and tree shadows. Even after summer weeds have died back, leaves from nearby trees fall and can accumulate on panel surfaces, lower edges, drainage paths, and walkways. Fallen leaves may seem temporary, but when wet from rain they can stick to panels or remain at the lower edge, causing soiling and poor drainage. In rows close to trees, fallen leaves and tree shadows can simultaneously cause a drop in power generation.

When fallen leaves land on the panel surface, they act as local shading and hinder power generation. They can be blown away by the wind, but if they stick after rain they tend to remain. When leaves accumulate at the bottom edge of panels or near the frame, it leads to a buildup of dirt and impairs water drainage. If, in autumn, only a particular row shows reduced power output, check the trees around that row, the wind direction, and how leaves are accumulating.

As the season moves from autumn toward winter, the sun's elevation gradually decreases and the shadows cast by trees and slopes become longer. Shadows from trees that caused no problems in summer may reach the panels from autumn onward. If power generation tends to drop in the mornings and evenings in particular, check for shadows from trees on the east and west sides. If you visit the site only at noon and conclude there are no issues, you may overlook morning and evening shadows.

For leaf litter management, it is important not only to perform cleaning but also to identify the sources. Determine which trees the leaves are coming from, which rows they tend to accumulate in, and where they flow after rain. If fallen leaves block drainage routes, they can lead to puddles and sediment buildup, which may encourage weed recurrence in the following season. During autumn inspections, check panel surfaces, panel lower edges, drainage routes, walkways, and the areas around equipment together.

Keeping a record of autumn measures makes management easier in subsequent years. If you can identify patterns—such as leaves accumulating in the same spots every year, the shadows of the same trees lengthening, or the same drainage routes becoming clogged—you can carry out inspections before power generation drops significantly. In seasonal measures to increase power generation, it is important not to regard autumn fallen leaves merely as a cleaning target, but to check them as factors that lead to shading, soiling, drainage issues, and the recurrence of weeds the following year.

Seasonal Countermeasure 7: Confirm reductions caused by low winter solar altitude, frost, and snow accumulation

Winter is a season when power generation tends to be lower because the sun's altitude is lower and daylight hours are shorter. However, if you attribute all winter declines in generation to natural seasonal variation, you may overlook generation losses that could be improved. Things to check particularly in winter are shading caused by the low sun angle, frost, snow accumulation, accumulated fallen leaves and dirt, and poor drainage.

Shadows tend to stretch longer in winter. Trees, slopes, fences, posts, and nearby buildings that had no impact in summer may cast shadows on panels in winter. If power generation is low in the morning or evening, check trees, terrain, and structures on the east and west sides. If only certain rows have reduced output in winter, seasonal shading may be involved. Winter shadows can be easily overlooked if inspections are done only at noon, so it is important to inspect the site during the times when generation is low.

Frost and freezing can also affect power generation. If the panel surface is covered with frost during the morning hours, the initial power output may be reduced. Frost often melts when exposed to sunlight, but it tends to remain in areas that are prone to shade or have poor ventilation. If power output is low only in the morning, check for the effects of frost or freezing in addition to shadows from trees and terrain.

In snowy regions, snow covering the surface of solar panels reduces power generation. In some cases the snow slides off quickly, but if it remains at the lower edge of the panel or around the frame it will affect power generation. After the snow has fallen, dirt may remain at the lower edge. Work after snowfall must give full consideration to safety, and risky or excessive work should be avoided. Check power generation data and on-site conditions to determine whether the issue will resolve naturally or whether inspection is necessary.

When preparing for winter, it is important to record shading, frost, snow accumulation, remaining fallen leaves, and deteriorating drainage. If power generation drops in the same location every winter, seasonal shading or frost may be involved. To increase winter power output, distinguish natural declines from declines that can be improved on-site, and continue tree management, leaf removal, drainage checks, and recording of shading.

Record Management for Sustaining Seasonal Measures

Inspection and work record management are essential to turn seasonal measures into improved power generation. Spring dirt, summer weeds and high temperatures, sediment after typhoons, autumn fallen leaves, and winter shadows and frost can recur at similar times each year. Without records, you end up searching for the same problems from scratch every year, making it easier for generation losses to go undiscovered. To increase power generation, it is important to accumulate where issues occur each season and the results of countermeasures.

What should be recorded are the location of equipment with low power output, the time of occurrence, the characteristics of the power-generation curve, types of soiling, shading from weeds and trees, accumulation of fallen leaves, locations of puddles and sediment, ventilation conditions around the equipment, the scope of cleaning and weeding performed, and changes in power output after countermeasures. Because adding too many recording items makes it difficult to maintain in the field, initially aim to record just enough so that, on later review, it is clear where and what happened and how it was addressed.

When you link power generation data with on-site photographs, it becomes easier to assess the effectiveness of seasonal measures. If generation improves after spring cleaning, then spring soiling becomes an important maintenance item at that site. If morning and evening generation improves after summer weed removal, it is highly likely that shadows from weeds were related to generation losses. If, in winter, the shadows of certain trees coincide with drops in generation, those locations should be prioritized for inspection in the following years.

When multiple people are responsible for management, it is also important that they can share the exact same location. In large power plants, similar rows and equipment can make it difficult to identify a place from photos alone. If you record equipment numbers, location information, photos, and work history together, on-site personnel, managers, inspectors, and repair personnel will find it easier to confirm the same location. Seasonal measures become more accurate not by relying solely on the experience of staff, but by accumulating them as shareable on-site data.

We will also record the power output after countermeasures. After performing cleaning, weeding, pruning, drainage checks, and maintenance around the equipment, we compare power output before and after the work, along with site photos and weather conditions. Measures that proved highly effective will be prioritized going forward, and if an effect is not evident we will investigate other causes. Repeating this process makes it easier to prevent seasonal declines in power output.

Summary

For seasonal measures to increase power generation, it is important to identify the causes of decline that commonly occur in spring, summer, autumn, and winter, and to check them before power output drops significantly. In photovoltaic power generation, you cannot increase the amount of solar radiation at the site itself. However, you can improve power output by bringing the system closer to a state that converts the received solar radiation into electricity without waste. To do that, review annual generation data and check, in order, soiling in spring, weeds from the rainy season into summer, high temperatures in summer, soil and debris after typhoons, fallen leaves in autumn, and shadows and frost in winter.

To prevent summer declines in power output, it is important not to overlook shadows caused by weeds, poor ventilation beneath panels, high temperatures around equipment, and debris or inadequate drainage after typhoons. To prevent winter declines, check for shadows from trees and slopes caused by the lower solar altitude, morning frost, snowfall, and residual fallen leaves and dirt. By separating the natural seasonal variations in power generation from on-site losses that can be improved, it becomes easier to prioritize cleaning, weeding, pruning, drainage checks, and maintenance around equipment.

Seasonal countermeasures cannot be completed in a single operation. Spring grime reappears the following year, summer weeds grow back, autumn fallen leaves accumulate every year, and winter shadows change with tree growth and terrain conditions. Comparing power generation before and after countermeasures, retaining on-site photos and work records, and applying them to the next inspection will increase the precision of improvements. To steadily raise power generation, it is essential to record seasonal occurrence trends and have a management system that proactively schedules inspections.

At particularly large power plants, a system for accurately sharing seasonal problem locations is important. If you record rows that tend to get soiled in spring, areas where grass tends to grow in summer, places where sediment washes in after typhoons, areas where fallen leaves accumulate in autumn, equipment that casts longer shadows in winter, and places where frost or snow tends to remain, together with location information, stakeholders can more easily confirm the same locations. By combining power generation data with on-site location information, it becomes easier to explain the priority of seasonal countermeasures and to streamline subsequent recurrence checks.

If you want to continue seasonal measures to increase power generation based on field data, using LRTK is also effective. As an iPhone-mounted GNSS high-precision positioning device, LRTK is useful for recording inspection locations by season within a solar power plant, areas prone to soiling, places where weeds grow easily, locations where shading occurs, spots with poor drainage, ranges where fallen leaves or snow tend to remain, and on-site photos together with high-precision location information. By keeping the causes of summer and winter declines with location information, it becomes easier to pursue power generation improvements based on field data rather than on intuition.