Basic Principles and 7 Practical Items for Strong Wind Measures in Solar Power Plant Construction

In solar power plant construction, countermeasures against strong winds, along with snowfall and drainage, are crucial themes that determine equipment safety and long-term stable operation. Since photovoltaic generation equipment is installed outdoors, it is vulnerable to strong winds and heavy rain; the Ministry of Economy, Trade and Industry (METI) has reiterated the importance of prior preparedness, noting that accidents can occur not only from large typhoons but also from relatively small typhoons. ([turn711552vi Ministry of Economy, Trade and Industry ))

In fact, METI’s 2026 compilation shows that, for photovoltaic generation equipment with output of 50 kW or more, the majority of accidents fall under “damage to electrical work,” which includes module and racking scattering due to strong winds and damage to PCS. Furthermore, among property damage incidents, cases where modules were blown outside the site and damaged houses and other structures account for more than half, indicating that strong wind measures are not only an internal equipment issue but also critically important for preventing third-party damage. ([turn711 Ministry of Economy, Trade and Industry ))

Also, the ground-mounted design and construction guidelines summarize wind damage cases such as collapse and scattering of racking due to insufficient joint strength of members or insufficient pile bearing capacity, fracture of aluminum members due to insufficient strength, and cases where piles did not have enough resistance on soft ground causing damage in central arrays. In other words, wind measures are not simply a matter of “making the racking stronger”; they require an integrated approach covering understanding site conditions, checking foundations and ground, construction quality of joints, and post-completion inspection and operation. ([tu NEDO ))

Therefore, what truly makes a difference in construction practice is, after understanding the design conditions, knowing which points on site to focus on for inspection, where to ensure construction quality, and how to link that to the inspection regime after handover. This article organizes strong wind countermeasures for solar power plant construction into seven items following the flow of design, construction, and operation preparation. It summarizes the basics practitioners should grasp from a practical perspective, applicable not only to sites in high-wind regions but also to regions where wind damage is normally less of a concern. NEDO )

Table of Contents

• Why strong wind countermeasures are important in solar power plant construction

• Item 1: Confirm the reference wind speed and ground surface roughness category together with site conditions

• Item 2: Don’t assume the same wind load at edges, corners, and center

• Item 3: Consider pile, foundation, and ground bearing capacity together with wind pressure

• Item 4: Make racking joints and fastener management the center of construction quality control

• Item 5: Alter wind exposure by height, spacing, and layout planning

• Item 6: Consider PCS surroundings and combustible material management through to post-scattering accidents

• Item 7: Decide pre- and post-typhoon inspections, emergency responses, and restart conditions in advance

• Common points of sites that tend to fail at wind countermeasures

• It is important to connect from construction stage to maintenance management

• Easier location sharing on large sites helps wind response

Why strong wind countermeasures are important in solar power plant construction

Strong wind countermeasures are important because wind does not act uniformly across the entire facility. Not only the wind speed itself but also factors such as the roughness of the ground surface around the site, distance from coasts or lakeshores, proximity to slopes or cliffs, array height, row arrangement, and whether a location is at the edge or center will change the loads actually received by racks and modules. Even current ground-mounted guidelines use ground surface roughness categories I–IV in wind pressure calculations and indicate the idea of setting mean wind speed distribution coefficients and gust effect factors. (NEDO 1] (Ministry of Land, Infrastructure, Transport and Tourism 2view4]())

Also, wind damage is likely to occur not only from deficient design values but from construction quality issues and misreading of site conditions. The current guideline’s damage cases include racks collapsing and scattering by gusts, piles being pulled out by typhoons, and racks scattering due to insufficient member or foundation strength; thus the cause is not simply “it broke because the wind was strong,” but involves joint strength, pile bearing capacity, and the ground conditions at the damaged locations. (NEDO 921734view4]())

Furthermore, wind countermeasures cannot stop at protecting the equipment itself. METI’s compilation shows that module scattering has caused damage to houses and other property, making prevention of third-party damage a major safety concern. If wind measures are lax during construction, the scope that post-completion maintenance can recover is limited. Therefore, understanding design conditions, ensuring construction accuracy, and post-completion (METI turn711552view3)

Item 1: Confirm the reference wind speed and ground surface roughness category together with site conditions

The first thing to check is which reference wind speed and ground surface roughness category are assumed for the site. The current guidelines, based on JIS C 8955:2017, organize that the reference wind speed V0 references the Ministry of Construction Notification No. 1454 of 2000, and they indicate the approach of setting usage coefficients assuming a design recurrence period of 50 years for ordinary photovoltaic systems and 200 years for extremely important systems. As a construction practitioner, don’t just look at the numbers written on the design drawings; confirm what those numbers are based on. (NEDO turn641653, NEDO, turn641653view0)

Attention is also required regarding ground surface roughness categories. The current guidelines classify ground surface roughness into I–IV, and treatment varies depending on distance from the coastline or lakeshore and the degree of urbanization. Also, JIS C 8955:2017 removed the previous exclusion provision that allowed not applying roughness category II for array heights of 13 m (42.7 ft) or less; now, even for heights of 13 m (42.7 ft) or less, it is necessary to apply roughness category II depending on ground surface conditions. It is important not to take low heights lightly. (NEDO, Ministry of Land, Infrastructure, Transport and Tourism, turn711552view4)

Even if a site looks like a flat vacant lot, wind conditions can actually be severe if it is close to the coast with few obstructions, if terraces or valley topography concentrates wind, or if it is near cliffs or slopes. The current guidelines require preliminary surveys to include document research, on-site surveys, ground investigations, and surveys of land use and surrounding environment to grasp terrain and ground features. The starting point for strong wind measures is to confirm whether the design assumptions truly match the site conditions. (NEDO turn921734view0)

Item 2: Don’t assume the same wind load at edges, corners, and center

The second item is to not assume that edges, corners, and the center receive the same wind exposure. The current guidelines state that for the wind force coefficients on the plane of ground-mounted photovoltaic arrays, the central array may use the prescribed formula values multiplied by 0.6 when windward and 0.7 when leeward; conversely, this means that edge arrays must be evaluated under stricter conditions than the central arrays. In construction practice, it is necessary to inspect foundations, members, fastenings, and support more carefully. (NEDO turn641653view0)

It is important not to oversimplify by thinking only the edges need reinforcement. Damage cases show examples where piles were pulled out not at the windward edge where wind pressure is largest but in the central array; the presumed cause was that the ground at the damaged location was soft and pile resistance was insufficient. Thus, it is important to determine not only the magnitude of wind loads and whether the ground or foundation is weak, but also which blocks under what conditions are vulnerable. (NEDO turn921734view4)

In practice, there are places on site that receive wind differently than general areas shown on drawings—near fences, close to slope shoulders, at transition zones of earthworks, along temporary roads, or the end rows in the long-edge direction. The edge/corner/center concept is a structural calculation partition, but in construction management, overlaying that concept onto the site’s terrain and earthwork conditions is more important than merely knowing load partitions. (NEDO, turn641653view0, turn921734view0)

Item 3: Consider pile, foundation, and ground bearing capacity together with wind pressure

The third item is to consider pile, foundation, and ground bearing capacity together with wind pressure. When thinking of wind damage, one tends to imagine modules and the racking upper parts first, but in reality, foundations and ground are often the weak points. Current guideline damage cases show rack collapse due to insufficient joint strength and pile bearing capacity, and typhoon-induced cases are presented. Strengthening only the superstructure cannot ensure overall safety if the ground side cannot withstand it. (NEDO turn921734view4)

Therefore, preliminary investigation before construction is extremely important. The current guidelines, as part of site surveys, require confirming the site’s formation based on geological maps and old maps to grasp terrain and ground characteristics, and further recommend sounding or boring to assess bearing capacity, soft ground, liquefaction determination, groundwater distribution, and lateral distribution of ground constants. It is dangerous to treat foundation specifications uniformly across a site assuming the entire site has the same ground conditions. (NEDO turn921734view0, turn921734view1)

In practical work, also confirm whether the design-stage investigation results align with the actual construction sensations. If penetration is lighter than expected, groundwater is locally high, behavior differs in fill areas, or the near-surface is soft, these are signs requiring attention. Wind safety depends greatly on whether you have identified locations where the racking and foundations may be vulnerable. (NEDO turn921734view1, turn921734view4)

Item 4: Make racking joints and fastener management the center of construction quality control

The fourth item is to place racking joints and fastener management at the center of construction quality control. Photos and accident cases of wind damage often highlight large-scale scattering, but the origin is frequently joint or fastening failures. The current guidelines state that when using bolts as friction joints, slip coefficients, introduced axial force and torque management, the relationship between bolt diameter and total thickness, clearance, relaxation, and the need for construction procedures should be defined. Moreover, by following construction manuals, the prescribed frictional force must always be reproducible and maintained during the service life. (NEDO turn685147view0)

Conversely, if torque management during construction is lax, the design strength cannot be reproduced on site. Even if the specified members are delivered as per drawings, ambiguous tightening torque control, undefined need for retightening, or inconsistent contact surface conditions will destabilize the resistance mechanism during strong winds. What really makes a difference in wind countermeasures is not so much the racking specification itself as whether the joints are reproduced on site according to the design intent. (turn685147view0)

Also, NITE’s 2025 materials report that on-site inspections found cases such as loosening of PV panel fixing fittings, which present risks of electrical accidents due to typhoons. The NITE website suggests that inspection systems to continuously maintain fastening conditions should be considered. It is important to connect tightening management during construction, pre-handover confirmation, and inspection items during operation as a single chain. (turn711552view1)

Item 5: Alter wind exposure by height, spacing, and layout planning

The fifth item is to change how wind is received by adjusting height, spacing, and layout planning. The current guidelines use the array plane’s mean height above ground H in calculating the mean wind speed distribution coefficient Er, and the gust effect factor is also determined by ground surface roughness category and mean height above ground. Therefore, height affects not only maintenance ease and clearance from the ground but the wind load itself. In layout planning, decisions must be made understanding how height impacts load conditions, not just generation output or constructability. (NEDO turn641653view1)

Moreover, row spacing and surrounding space are not solely matters of solar shading. The current guidelines require that structural design plans include layout plans, and forcing arrays too close to edges, or ignoring conditions with few obstructions near the coast, can increase post-construction risks even if the design is formally valid. (turn921734view5, turn641653view1)

Also, guidelines note that in coastal areas airborne salt and in snowy regions salt from de-icing agents are also factors to consider; wind is not only a pushing force but a factor that accelerates corrosion. Especially in coastal areas, consider equipment placement with attention to wind direction and ingress, corrosion protection at ground-level parts, and ease of maintenance inspections. Strong wind measures can be greatly affected by layout choices, so at the construction stage it is essential to read the site’s wind corridors. (NEDO turn921734view3)

Item 6: Consider PCS surroundings and combustible material management through to post-scattering accidents

The sixth item is to consider PCS surroundings and combustible material management, looking ahead to accidents that may occur after scattering or damage. When thinking about wind measures, attention tends to concentrate on preventing scattering of modules and racking, but accidents do not end there. METI’s 2026 compilation, in response to PCS damage cases, indicates that the technical standards for photovoltaic power generation equipment were revised on May 15, 2025, to explicitly require measures to prevent spread of fire to flammable combustible materials around machinery and equipment such as PCS that may ignite if they fail—examples include dried underbrush. (Ministry of Economy, Trade and Industry turn711552view3)

This revision highlights that, even if strong winds do not directly cause fire, damage, scattering, flooding, or malfunction after strong winds or typhoons can lead to fire. NITE’s 2025 materials also emphasize that it is important to consider these points. It can be read that one should check not only whether racking is standing but also equipment surface abnormalities, scattered debris around equipment, loosened fixing fittings, and flood susceptibility. (turn711552view1, turn711552view2)

In construction practice, place the PCS in locations where falling or scattered objects are less likely to accumulate, ensure that maintenance staff can quickly inspect after strong winds, and recognize that wind measures are not complete with structural safety alone; they become practically effective only when they also consider electrical accidents and fire spread prevention after scattering. Being mindful of this from the construction stage will greatly change the level of safety after handover. (turn711552view3, turn711552view1)

Item 7: Decide pre- and post-typhoon inspections, emergency responses, and restart conditions in advance

The seventh item is to decide pre- and post-typhoon inspections, emergency responses, and restart conditions from the construction stage. METI has called for inspections before and after typhoon approach and passage to reduce accident risks associated with typhoons accompanied by strong winds and heavy rain. In other words, strong wind countermeasures are not only about the performance of the finished product but largely about operations before and after weather events. (turn711552view2, turn711552view1)

What should be decided during the construction stage is which wind speed or warning levels will halt work, how to handle temporarily stored materials and unfixed members, and which items to prioritize for inspection. The current guideline’s structural design and construction planning flow also indicates proceeding with planning while considering regional and environmental characteristics, creating a maintenance plan at the design stage, and linking that to construction planning, stakeholder briefings, completion inspection, and pre-use self-inspection and self-confirmation. Wind response should be integrated into this flow. (turn921734view5)

Also, it is important not to leave restart conditions ambiguous. Do not resume work immediately after a typhoon simply because it has passed; check for module displacements, bolt looseness, scattered debris or flooding, damage to fences or cables, etc. On large sites, if you do not decide in advance how much needs to be checked to safely resume operations, judgments tend to become dependent on individuals. Strong wind countermeasures do not end with design values; in practice it is extremely important to decide in advance how to stop work and how to restart. (turn711552view1, turn921734view5)

Common points of sites that tend to fail at wind countermeasures

Sites that tend to fail at wind countermeasures share several common traits. In reality, the needs differ between edges and centers, between soft ground and compact ground, and between faces exposed to sea breezes and those that are not. Nevertheless, treating wind loads and ground conditions uniformly can make the design seem valid on paper while missing weak points on site. (turn921734view4, [turn9217 NEDO ))

Second, fastening management is insufficient. As the guidelines organize, at bolted joints it is important to manage introduced axial force, torque control, variability, relaxation, and preparation of construction manuals. Warnings are raised that loosening of fixing fittings can lead to typhoon-time accident risks, and merely having the designed components is not sufficient. (turn685147view0, Ministry of Economy, Trade and Industry )

Third, focusing only on racks without linking PCS, surrounding combustible materials, and post-typhoon inspections weakens overall safety. Recent compilations have made fire spread prevention measures for dried grass around PCS a concrete technical item, and safety after strong winds is a cross-cutting theme of structure, electricity, and maintenance. Sites that treat wind countermeasures as solely a structural matter tend to be weaker in post-completion operations. (turn711552view3)

Connect from construction stage to maintenance management

Wind countermeasures must proceed including confirmation of reference wind speed and ground surface roughness category, pile and ground bearing capacity, joint and fastening management, layout planning, fire spread prevention around PCS, and operational planning before and after typhoons. Looking at current design and construction guidelines and recent accident compilations, damages are not caused by a single factor but tend to grow when design assumptions, construction quality, ground conditions, and maintenance shortcomings overlap. The perspective to be maintained is not that it is sufficient for equipment to be standing at completion. Sites that read regional characteristics and site conditions, understand design assumptions, ensure quality to be reproduced during construction, and have a clear plan for how to inspect and confirm safety after a typhoon are more stable against strong winds. Wind countermeasures are not completed on drawings alone; they only work on site when construction and operation are connected. (turn921734view5, turn711552view2)

Easier location sharing on large sites helps wind response

After strong winds, it is important to quickly share which row’s which end has abnormalities, around which PCS scattering is concentrated, and which block’s ground is unstable. On expansive sites like solar power plants, even small misalignments in positional recognition can delay inspection and emergency response.

In such situations, using systems like LRTK (iPhone-mounted GNSS high-precision positioning devices) to make it easy to share equipment locations and abnormal points on iPhones helps advance initial inspections and recovery after strong winds. While the foundation of wind countermeasures is design and construction quality, on large sites the difference in response capability ultimately comes down to “how quickly you can share where and what happened.”