Design for all climates

High in the Swiss Alps, a PV module may encounter intense irradiation reflected from snow while operating at temperatures well below freezing. Thousands of kilometers south, a module in the North African desert will be confronted with heat, dust, UV exposure and sandstorms. A continent away, in Singapore, installations must endure a combination of heat, persistent humidity, heavy rainfall and biological growth.

All three locations can offer attractive conditions for solar generation, but each harbors its own difficulties. This becomes increasingly relevant as more PV is deployed in deserts, high-latitudes and tropical environments.

The challenge for developers is no longer only whether PV can be deployed in these environments, but how systems should be designed to be reliable and economically viable under their specific climatic stresses.

Environmental stresses affect not only energy yield, but also degradation, component lifetime, operations and maintenance (O&M) requirements and project economics. The environmental stresses the system will face over its lifetime should be understood at an early stage for component selection, system design and financial planning. 

For example, a recent IEA PVPS Task 13 report describes the impact of local conditions on a PV system installed at Wildkogel, Austria. Every winter, wind-driven snow formed a large snow roll that covered the PV fields, caused severe damage, and forced the relocation of the plant. This is an extreme illustration of a broader principle: a mitigation strategy designed after construction may be more expensive and less effective than designing around the environmental risk from the outset.

Alpine trade-offs

Cold climates make a good illustration of the way climate optimization is all about trade-offs. On the plus side, low temperatures improve module efficiency and slow many chemical degradation processes. At high altitudes, PV can also benefit from strong irradiation and high snow albedo. Measurements have recorded irradiance of up to 1,700 W/m² at the highly elevated Jungfraujoch in Switzerland, and other studies have shown snow can reflect 80% to 90% of radiation in the UV range.

But those conditions introduce another set of risks. Snow and ice impose mechanical loads on modules and mounting structures, and these are also often uneven and concentrate stress toward the lower part of modules. Low temperatures also make polymer materials stiffer, which reduces their ability to absorb mechanical stress and potentially increases stress on cells and interconnections. Repeated thermal and freeze–thaw cycling adds another source of fatigue.

Alpine designs have to involve so much more than merely choosing a module with a favorable temperature coefficient. High tilt angles and sufficient ground clearance can promote snow shedding and prevent snow from accumulating in front of the modules. Snow fences and simulations of snow transport can help control drifting. Mounting structures may require stronger foundations and adaptation to local terrain and soil conditions. “The whole system needs to be designed with snow risk in mind, including adequate clearance and somewhere ploughed snow can be pushed,” said Ruth Prieto, engineering manager at Sonnedix.

When it comes to module construction, mechanical resilience can be improved with thicker glass, appropriate frame geometries, flexible encapsulants and cell interconnection designs with greater resistance to microcracking.

There are trade-offs to consider, such as how frameless modules may shed snow more easily but are less mechanically stable. Even inverter sizing may need reconsideration, as high irradiance combined with low cell temperatures can produce unusually high currents that must be considered against the inverter’s maximum short circuit current capacity.

“Generation budgets are harder to put together because predicting snowfall, and therefore the associated production losses, is difficult,” according to Prieto. “One challenge is estimating how much snow there is, because your site is often far away from the snow sensor, and the models or maps are not always accurate. It’s not just about knowing how much snow there is, but also what kind of snow it is – whether it’s heavy, wet or sticky – which can affect whether the snow slides off the module or freezes.”

Desert conditions

High irradiation makes hot and dry regions obvious candidates for PV, but high operating temperatures reduce output and accelerate degradation. UV exposure can damage polymers and other module materials, while wind brings mechanical loading. Heavy soiling accumulation can also occur because of abundant airborne dust and infrequent rainfall. Sandstorms can also reduce direct normal irradiance by as much as 80% to 90% during an event and can substantially increase dust deposition on module surfaces.

Expected soiling should be assessed and its energy losses and mitigation costs incorporated into the business case. Cleaning budgets based on generic assumptions can leave O&M contractors trying to maintain performance with insufficient resources. The intended cleaning strategy can also influence plant design, for example, through requirements for access and the space needed for cleaning equipment.

At Sonnedix’s projects in Chile, water availability is another consideration. “Water for cleaning is scarce, and when available it must be demineralized; otherwise, the minerals leave a layer on the module glass,” Prieto said. “We use soiling sensors distributed throughout the plant and contractual clauses with O&M contractors requiring cleaning once a maximum soiling percentage is exceeded.”

An assessment with PV radar cleaning optimization software illustrates how strongly the optimal strategy depends on local conditions and costs. A 30 MW plant in southern Spain experiences average annual soiling losses of just 1.3%, although losses can reach 10% in August in particularly dry years. At a cleaning cost of €750 ($855)/MW, cleaning only in particularly dry years – roughly once every five years – was the most economical option. At €250/MW, however, cleaning once or twice a year became worthwhile.

Conditions in the Negev Desert in Israel require different tactics. With extremely scarce rainfall and much higher soiling losses, the assessment found that investing in three tractors for dry cleaning was the optimal solution. This reduced the cost each time the installation was cleaned compared with external services, and allowed the equipment to be used all year round.

“The main difficulty in reaching an optimized cleaning strategy lies in the uncertainty of certain parameters, such as how much soiling actually accumulates on the panels each day – spatial and temporal heterogeneity may be significant,” said Julien Chapon, senior technical project manager at TotalEnergies. “Many sensors exist, but their accuracy is not as good as what we get from irradiance or electrical measurements – and the same goes for the models.”

Beyond soiling, hot and dry climates require several other adaptations. Modules and materials can be selected for greater resistance to heat, UV exposure and thermal cycling, and mounting structures and trackers need to withstand potentially high wind loads. Automated stow strategies can protect trackers during extreme winds, although a 2024 survey of PV plant owners by the International Energy Agency Photovoltaic Power Systems Programme (IEA-PVPS) found that around half of respondents had experienced tracker or module damage due to inadequate tracker response to extreme weather.

Local soil hardness and corrosivity also need to be considered when designing foundations. Another big issue is the thermal management of electrical equipment, because high ambient temperatures can cause inverter derating or shutdown. “The financial model includes equipment replacements due to these extreme conditions,” said Sonnedix’s Prieto.

Humidity impact

Hot and humid regions frequently combine high temperatures with high relative humidity, heavy rainfall and high irradiation. Moisture can accelerate corrosion, delamination and other degradation processes. The combination of heat, humidity and high system voltage can increase susceptibility to potential-induced degradation (PID).

The module’s bill of materials (BOM) therefore becomes particularly important, as the choice of encapsulants, glass, frames and other components can influence the resistance to moisture-related degradation. The Task 13 report highlights particular moisture sensitivities in newer n-type technologies such as heterojunction and TOPCon. Appropriate encapsulation and packaging can help mitigate these risks, although the optimal solution depends on the cell technology and module design. More generally, corrosion-resistant frames, high-IP-rated junction boxes, moisture-resistant connectors and UV-stable materials can provide further protection in hot and humid environments.

Optimization is not only about the selection of modules and components. “We advise clients to prioritize ventilation wherever the site allows, since airflow is one of the few levers available at installation,” said André Nobre, managing director of PV Doctor. “In this climate, components simply fail more often, so continuous monitoring is essential, not just to catch failures, but to isolate how much of the yield loss is actually soiling, rather than other causes.”

System geometry can also help mitigate soiling accumulation. Although very low tilt angles maximize incident irradiation in those locations close to the equator, they also encourage dirt accumulation. “Near the equator, roofs and mounting structures are often installed at shallow tilt angles to match the site, which lets rainwater pond on the glass,” continued Nobre. “That ponded water bakes dirt onto the surface, leaving permanent staining that ordinary rain or cleaning can’t remove.” For this reason, in Singapore, for instance, systems can be installed at higher-than-optimal tilt angles to improve rain cleaning. “Where ponding is a risk, we recommend drain clips as a simple, effective fix,” said Nobre.

Even orientation can challenge conventions: since mornings in Singapore tend to be sunnier than afternoons, east-facing modules in one study received more irradiation and generated 1% to 2% more energy than north- or south-facing modules. Some tropical environments present an additional soiling challenge. Warm, humid conditions can also promote biological soiling, which, unlike dust, can persist despite rainfall and may require more intensive cleaning. For example, in 2015, a University of São Paulo study reported biofilm development on PV modules within six months of installation in Brazil, leading to an 11% decrease in cell efficiency over 18 months.

Beyond efficiency

Current approaches to comparing potential module energy yield do not account for degradation and therefore provide no direct indication of long-term reliability. Degradation depends on the bill of materials, manufacturing quality and environmental exposure, and measured climate-specific performance-loss rates cited in the report range from around 0.3% to 2.5% per year.

That difference can have major implications for lifetime yield and project revenues. It also exposes one of the remaining gaps in PV optimization: the industry has become increasingly sophisticated at predicting initial energy yield, but linking those predictions to climate-specific long-term degradation is much harder. Climate optimization also has practical limits. A module better suited to a particular climate may cost more, be unavailable at the required scale, or fall outside existing procurement agreements.

The post Design for all climates appeared first on pv magazine Global.