6 Shade Mitigation Strategies to Increase Power Generation｜Solar Improvement Points

Table of Contents

• Visualize where shadows occur to increase power generation

• Shadow countermeasure 1: Check the time periods when shadows appear using power generation data

• Shadow countermeasure 2: Manage weeds and the grass height in front of the panels

• Shadow countermeasure 3: Check for shadows cast by trees, slopes, and surrounding structures

• Shadow countermeasure 4: Conduct inspections with seasonal solar altitude in mind

• Shadow countermeasure 5: Record locations where shadows occur to prevent recurrence

• Shadow countermeasure 6: Also check for other causes of performance decline besides shading

• Operational approach to translate shadow countermeasures into power generation improvements

• Summary

To increase power generation, visualize where shadows occur

When you want to increase the output of a solar power system, one of the first causes to check is shading. Solar panels generate electricity by receiving sunlight, and even if only part of a panel is shaded, the power output can drop. Shadows may seem like an obvious cause, but in real-world conditions they are often overlooked. This is because shadows move with the time of day and the seasons, and are frequently not visible at the moment of inspection.

To increase power generation, you cannot increase the amount of solar radiation at the site itself. However, you can bring the system closer to a state in which the incident solar radiation is converted into electricity with as little waste as possible. Shading mitigation measures are precisely the practical improvements for that purpose. Weeds, trees, slopes, fences, support poles, surrounding buildings, adjacent rows of panels, racking, inspection equipment, and so on—the causes of shading are varied. When these cast shadows on the panels, generation is lost during time periods when the panels would otherwise be producing electricity.

For practitioners searching for "how to increase power generation", the important thing is not to judge shadows by appearance alone. Even if you check the site at noon and find no shadows, long shadows can extend in the morning or evening. A problem that is hard to see in summer can become apparent in winter when the sun's altitude is lower, causing the same trees or slopes to cast longer shadows. Trees that posed no problem at the time of installation can grow over a few years and reduce power generation. In other words, when addressing shading, it is essential to understand not only "the shadows you see now" but also "when those shadows occur."

To reduce power generation losses due to shading, it is necessary to link generation data with on-site inspections. If generation is low only in the morning, suspect shading on the east or southeast; if it is low only in the evening, check for shading on the west or southwest. If generation drops only in winter, look at seasonal changes in solar altitude and shadows from surrounding trees. If only some rows, rather than the entire plant, show lower output, check the front and surroundings of those rows for local shading. In this way, reading the directionality of shadows from the data and finding the source on site is the first step to improving generation.

Also, measures against shading are not finished once carried out. Weeds grow back, trees grow, and fallen leaves and vines occur seasonally. If new structures or equipment are installed nearby, new shadows may be created. To steadily increase power generation, it is necessary to detect shading, take countermeasures, check changes in power output, and keep records that can be used in the next inspection. From here, we will explain six practical shading countermeasures you should understand to increase solar power generation.

Shading Countermeasure 1: Identify the times when shading occurs using power generation data

The first step in addressing shading is to check the power generation data before visiting the site. Because shading occurs at certain times of day, looking only at monthly or annual generation makes it difficult to determine whether shading is the cause. Even if the result is low generation, the suspected causes differ depending on whether output is low in the morning, the midday peak does not develop, or it falls in the evening. To find generation losses caused by shading, you must first look at the shape of the generation curve.

If morning power generation is low, shadows from weeds, trees, slopes, or nearby structures on the east or southeast side may be involved. If power generation is low in the evening, suspect shadows from trees, fences, adjacent equipment, or terrain on the west or southwest side. If a similar drop occurs at the same time every day, it may be due to fixed shadows rather than weather. Conversely, if power generation fluctuates greatly only on cloudy or rainy days, this is due to cloud shadows and should be distinguished from shadows caused by equipment or weeds.

When checking for shading, use the power generation curve from a clear, sunny day as the reference whenever possible. On cloudy days, power output fluctuates irregularly due to the movement of clouds, making shading features harder to discern. On a sunny day, it's easier to verify whether drops in power output occur at the same time each day. If the generation curve's morning rise is delayed, suspect morning shadows; if the evening decline occurs early, suspect shadows on the west side; if there is a dip during part of the midday, suspect local structures or inter-row shading.

It is also useful to compare equipment within the same power plant. If installations with the same orientation, the same tilt, and a similar number of panels show lower output only in certain rows in the morning or evening, there may be a source of shading around those rows. If the entire plant shows similarly low output, weather or solar irradiance conditions may be the main factor; however, if only parts are low, you should check for on-site causes such as localized shading, soiling, or connection faults.

If you identify time periods when shadows are suspected from power generation data, it's important to schedule on-site inspections to match those times. Inspecting the site at noon will not reveal shadows that occur in the morning or evening. If output is low in the morning, take on-site photos in the morning; if it's low in the evening, check the shadows in the evening. Recording the time shadows occur, their sources, and the equipment they fall on makes it easier to decide on weed control, pruning, or revising equipment placement. Countermeasures against shading to increase power generation are more accurate when you start from the power generation data.

Shading Countermeasure 2: Manage Weeds and Vegetation Height in Front of Panels

The most fundamental measure against shading is managing weeds and the height of vegetation in front of the panels. At solar power plants, weeds can grow rapidly from spring through summer. Even areas that showed no problems immediately after installation or during winter can see grass reach the lower edge and front of the panels within a few weeks, casting long shadows during times of low sun angle in the morning and evening. Even if the vegetation does not touch the panels directly, power generation will decrease if shadows reach the panel surface.

What’s important in vegetation height management is not to aim solely to make the entire site uniformly tidy. Of course, maintaining pathways and the overall site is necessary, but the areas that have the greatest impact on power generation are the fronts of the panels, the areas near the lower edges, between rows, around equipment, and inspection walkways. In particular, if grass is growing in front of a row that has been shown to have decreased output in the generation data, it should be addressed as a priority. Even if you tidy areas that are less likely to affect generation first, if the grass in front of the panels that actually creates shadows remains, the improvement will be limited.

When mowing, care must be taken to avoid contacting cables and connection points. In areas where weeds are overgrown, the condition of cables, conduits, connections, and under the mounting racks can become difficult to see. Working under those conditions risks accidentally damaging cables. Weed-control measures intended to increase power generation must not cause other power generation problems. Before starting work, it is important to check the locations of cables, the areas around equipment, and the condition under the racks, and to avoid attempting work that is unsafe.

Additionally, weeds also affect ventilation. When vegetation proliferates under panels or around equipment, airflow can become restricted and heat can become trapped. While solar power generation is generally easier when sunlight is stronger, higher panel and equipment-area temperatures can reduce output. Even if weeds are not casting direct shade, they can affect energy production and maintainability by causing poor ventilation or making inspections more difficult.

To continue managing grass height, it is important to record the locations and times when grass tends to grow quickly. If there are patterns—such as grass growing in the same spots every year, the same areas becoming overgrown after rain, or grass height tending to increase below slopes or where water collects—you can adjust future inspection timing and weed-removal areas. Shade mitigation to increase power generation is not a one-time mowing; it is an operational approach to maintain grass heights that are less likely to cause generation losses.

Shading Measure 3: Check the shadows cast by trees, slopes, and nearby structures

The causes of shading are not limited to weeds. Trees, slopes, nearby structures, fences, support poles, adjacent equipment, surrounding buildings, and the like can also lead to reduced power generation. In particular, shadows from trees and slopes may not appear problematic at the time of installation but can have a significant impact after several years. To increase power generation, it is necessary to check not only the weeds in front of the panels but the entire surrounding environment of the power plant as potential sources of shading.

Shading from trees is a factor that can easily become problematic over long-term operation. Trees that were small at the time of installation can grow and, after a few years, reduce power generation in the mornings, evenings, and during winter. Trees located on the south, east, and west sides in particular cast shadows on the panels depending on the time of day. At plants near forests or sites where trees outside the premises are close by, it is necessary to regularly check for branch overhang and changes in tree height. Because tree shading can recur even after countermeasures are taken, it is important to keep inspection records and manage it continuously.

Shadows from slopes and terrain are also often overlooked. At power plants located close to slopes, the slope itself can cast shadows when the solar elevation is low. Even if there is no problem in summer, shadows can extend much longer in winter and reduce power generation in the morning and evening. Because shadows caused by terrain are often not as easy to remove as weeds, it is important to compare them with power output data to determine which times of day and which areas are affected.

Check for shadows caused by nearby structures. Fences, signs, monitoring poles, wiring support components, adjacent equipment, and so on can cast long, narrow shadows at certain times of day even if they are small structures. If power generation changes after adding new equipment, check whether the addition is casting a shadow. If the panel surfaces are clean and the grass has been mowed but output drops only during specific times of day, shadows from structures may be involved.

When checking the sources of shadows, it is important to record not only photos but also the time. The same shadow can have different impacts on power generation and different priorities for countermeasures depending on whether it occurs in the morning, at midday, or in the evening. If you record the equipment affected by the shadow, the source, the time, and the season, you can use that information for the next inspection and for deciding on countermeasures. For shadow mitigation aimed at increasing power generation, it is important not only to find the shadows but also to determine how much they affect power generation.

Shading Measure 4: Inspect with Seasonal Sun Angles in Mind

A common pitfall in shadow mitigation is deciding there is no problem after only a single on-site inspection. The sun's position changes with the seasons, and shadow length and direction change accordingly. Even sites that present no issues in summer can experience much longer shadows in winter because the sun's altitude is lower, causing shadows from trees, slopes, fences, and nearby structures to extend further. To increase power generation, inspections need to account for seasonal changes in shading.

Winter is a season when generation losses due to shading become more apparent. Because the sun's altitude is low, shadows from surrounding trees and slopes are more likely to reach the panels. Morning and evening shadows also lengthen, which can affect the ramp-up of the generation curve and the evening decline. If winter generation is lower than expected, you need to check not only seasonal variations in solar irradiance but also the impact of shading. If a particular row is low only in winter, shadows from the surrounding environment may be involved.

In summer, pay attention to weed growth and rising temperatures. Because the sun’s altitude is high, shadows from trees and slopes may not be as long as in winter, but weeds can grow rapidly and cast shadows on the lower edge and front of the panels. Also, if grass proliferates beneath the panels and around equipment, ventilation can worsen and the thermal environment may be affected. During summer inspections, it is important to check not only shadows but also grass height, ventilation, and the condition around equipment.

From spring through the period around the rainy season, weeds begin to grow and require attention. Even if vegetation height was not a problem at the previous inspection, it can increase rapidly after continuous rain. If power output drops after the rainy season ends, check the condition of the vegetation in front of the panels, on slopes, and along fences. In autumn, check for fallen leaves, remaining vines, and overhanging tree branches. In this way, the causes of shading to check change with each season.

To make seasonal inspections effective, it is important to combine historical power generation data with on-site records. If power generation decreases in the same row at the same time of year every year, seasonal shading may be involved. Recording the time the shading occurs, the affected equipment, the season, and taking photos allows you to anticipate inspections and countermeasures in subsequent years. Shading countermeasures to increase power generation should be implemented not as a temporary check but as management that takes seasonal changes into account.

Shadow Countermeasure 5: Record Shadow Locations to Prevent Recurrence

To connect shadow mitigation to improved power generation, it is essential to record where shadows are found. Even if shadows are observed on site, unless the location and time are shared accurately, they cannot be used for subsequent inspections or countermeasures. This is especially true at large power plants, where similar rows and equipment are lined up and photos alone can make it difficult to identify the location. Recording the shadow location, the cause of the shadow, the time, and the affected equipment makes it easier to confirm recurrence.

What should be recorded is not only the places where shadows appear. The source of the shadows, the equipment affected by the shadows, the time the photo was taken, the season, and the relationship with power generation data are also important. If grass casting a shadow is observed in front of a system that shows low power generation in the morning, record the location of the grass, the grass height, and the time the photo was taken. If the shadow of a particular tree is extending in winter, record the tree’s position, the rows affected by the shadow, and the season. Having this information makes it easier to verify measures afterwards and to prevent recurrence the following year.

After weeding and pruning, record the work area and changes in power generation. If morning and evening power generation improves after the work, it is likely that shadows were the main cause of the generation loss. If there is no improvement, you need to check for other causes such as dirt, connection points, equipment shutdowns, or output curtailment. To evaluate the effectiveness of shadow mitigation, it is important to be able to compare power generation and on-site photos from before and after the work.

At sites without records, the same issues have to be checked from scratch every time. When staff change, it becomes unclear which grasses are likely to cast shade, which trees will affect the site in winter, and at what times shadows appear. With records, it becomes easier to decide which areas to prioritize during the next inspection, allowing countermeasures to be taken before power generation drops significantly. Shade countermeasures should not rely solely on field experience; it is important to shift to reproducible record-keeping.

Also, combining location information and photographs improves the accuracy of shared shadow data. If installations showing a decline in power generation in the power generation data can be linked to the positions of shadows photographed on site, it becomes easier to share the scope of countermeasures among stakeholders. By clarifying weeding areas, branches to be pruned, rows that should be inspected, and the timing when rechecks are necessary, duplicated work and overlooked checks can be reduced. For shadow mitigation measures aimed at increasing power generation, record-keeping itself is an important improvement.

Shading Countermeasure 6: Also check for causes of performance decline other than shading

If measures against shading do not sufficiently improve power generation, it is necessary to check for causes other than shading as well. The cause of reduced power generation is not necessarily a single factor. Even if shadows from weeds or trees are removed, power output may not fully recover if issues remain such as dirt on the panel surface, faults in connections, cable damage, inverter or converter stoppage, output curtailment, temperature rise, or poor drainage. Shading measures are important, but it is crucial to position them as part of the overall power generation improvement.

First, check for dirt and deposits on the panel surface. Even if you remove shadows, if a band of grime remains along the lower edge of the panel or bird droppings or fallen leaves are attached, the amount of light received will decrease. In rows close to trees, not only shadows but also fallen leaves, sap, and bird droppings tend to accumulate. If the midday peak does not increase even after shadow mitigation, dirt and equipment-related factors should also be considered.

Next, inspect the strings and connection points for abnormalities. If a particular string is performing lower than equipment under the same conditions, not only shading or dirt but also poor connections or cable damage may be involved. If power generation becomes unstable after rain, suspect moisture ingress or the environment around the connections. When checking electrical equipment, prioritize safety, record the affected equipment, time of occurrence, changes in power output, site photographs, and the surrounding environment, and, if necessary, arrange for a professional inspection.

It is also necessary to check for shutdowns or output curtailment of power conversion equipment. If the power generation curve suddenly drops midway, the top flattens and plateaus even on sunny days, or only the range connected to a specific piece of equipment is low, check the equipment history. Even if shadows are removed, power output will not recover if equipment-side shutdowns or restrictions remain. Correlating the time of the drop in power generation with the equipment history makes it easier to isolate the cause.

Drainage and topography must not be overlooked. Locations where weeds—the cause of shading—repeatedly grow may have underlying issues such as standing water, easy inflow of sediment, or pathways that become easily waterlogged. If you only address the shading, the same power generation losses will recur as long as the conditions for recurrence remain. To increase power generation, it is necessary not only to eliminate shading but also to create site conditions that make shading less likely.

Operational Approaches to Linking Shading Countermeasures to Power Generation Improvements

To link shading countermeasures to improvements in power output, it is important to compare power generation before and after the measures. After carrying out weed control, pruning, reviewing the placement of structures, and removing fallen leaves, check how power generation has changed. It is difficult to completely remove the influence of weather, but by comparing sunny days with each other or comparing against systems under the same conditions, you can grasp certain trends. If power generation in the morning and evening has improved, the shading measures may be having an effect.

Shade mitigation is not something that can be completed in a single operation. Weeds will grow back, trees will grow, and fallen leaves occur seasonally. Adding new equipment or structures can also create new shade. Therefore, it is necessary to record locations, seasons, and times of day that are prone to shading and to ensure they are prioritized at the next inspection. Rather than responding after power generation has fallen significantly, it is ideal to first identify the conditions likely to cause shading and take measures.

When multiple people are responsible for management, it is also important to be able to accurately share the same location. In a large power plant, where similar rows and equipment are lined up, a shadow photo alone can make it difficult to identify the location. If you record the equipment number, location information, photos, the time the photos were taken, and the work history together, field personnel, managers, inspectors, and repair personnel will find it easier to confirm the same location. It is important to leave decisions about shading countermeasures as shared on-site data rather than relying on individual memory.

It is also necessary to clarify the priority order for shade mitigation. Treating all grasses and trees with the same priority increases the workload. Prioritize checking facilities that show clear drops in power generation data, shade that persists for long periods, weeds that are likely to recur, trees whose shadows extend longer in winter, and grasses that obstruct inspection walkways or areas around equipment. To increase power generation, it is practical to address shade in order from those causing the largest generation losses.

To embed shading countermeasures into operations, it is essential to continuously monitor on-site changes. Even in locations that showed no issues at the previous inspection, grass can grow, tree branches can spread, and fallen leaves can accumulate as the seasons change. By cross-checking changes in power generation data with on-site records and identifying spots prone to shading early, you can minimize generation losses. Improving power generation is not about eliminating shade once, but rather about continuing management that makes shading less likely to occur.

Summary

In shading countermeasures to increase power generation, it is important to accurately determine when, where, and on which equipment shadows occur. In solar power generation, the site cannot increase the amount of solar irradiance itself. However, you can improve power generation by bringing the system closer to a state in which received solar irradiance is converted to electricity without waste. To do that, you need to check the time periods when shading appears in the generation data and then, in order, inspect weeds, trees, slopes, surrounding structures, seasonal variations, and recurring locations.

To avoid failures in shading measures, it is important not to judge based solely on an on-site check at noon. Shadows lengthen in the morning and evening, and the sun’s altitude is lower in winter, so shadows that were not visible in summer can affect power generation. Perform on-site checks during periods of low power output and record the source of the shading, the affected equipment, the time the photo was taken, and the season; this will clarify the rationale for countermeasures. Tasks such as cutting weeds, trimming branches, and removing fallen leaves should also be carried out in conjunction with power generation data so that their improvement effects can be more easily confirmed.

Also, shadow mitigation is not something that can be completed in a single operation. Weeds will grow back, trees will grow, and fallen leaves occur seasonally. In areas with poor drainage, grass is more likely to recur, and if grass grows around equipment it can affect ventilation and ease of inspection. To stably increase power generation, it is essential not only to detect shadows and take countermeasures, but also to record locations where shadows are likely to recur and prioritize them during the next inspection.

Especially at large power plants, a system for accurately sharing where shadows occur is important. If inspection photos are saved with location information for rows where weeds tend to grow, areas where trees cast shadows, equipment where slope shadows appear, places where fallen leaves tend to accumulate, and areas where weeding or pruning has been carried out, stakeholders can more easily confirm the same locations. By combining power generation data with on-site location information, it becomes easier to explain the prioritization of shadow countermeasures and to streamline recurrence checks going forward.

If you want to continue shadow mitigation measures to increase power generation based on field data, utilizing LRTK is also effective. LRTK, an iPhone-mounted GNSS high-precision positioning device, is useful for recording high-precision location information together with the locations where shadows occur within a solar power plant, areas where weeds are likely to grow, the reach of shadows from trees and slopes, weeding areas, spots with poor drainage, and on-site photos. By leaving the results of shadow mitigation with location information, it becomes easier to pursue power generation improvements based on field data rather than intuition.