Insights from the first construction season

^{Created by M.L., OST, on 07.01.2026}

According to the initial regulations of the “Solarexpress”, 10 % of the planned PV-installation must be connected to the grid by the end of this year (2025)¹. Therefore, the constructions had to begin this summer. So far, 4 sites are under construction and partially connected to the grid:

• Madrisasolar
• Sedrun Solar
• Nalp Solar
• Sidenplangg

Based on these sites, first experiences were made in the field and valuable insights gained for the next building seasons. The aim of this article is to summarize this information and share some of the lessons learned. To do so, the persons in charge of each construction site were contacted and an interview could be arranged with most of them [1], [2], [3]. In addition to the sites under construction, the projects of Tschingel (discarded) and MontSol (first instance licence granted) were contacted [4], as well as Solaranlage Vorab (legally authorized) [1]. As can be seen in the paragraphs below, several topics are common challenges to all alpine projects, and the found solutions hence generally relevant, while others are site-specific.

Note: All interviews were held in German, and some citations translated to be quoted here.

¹The Parliament adapted the regulations during their Spring session: This requirement was lowered to having publicly submitted the building application by the end of 2025.

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Common challenges & solutions

Costs & structural integrity of construction

The harsh environment of the Alps sets a high standard regarding robustness of the installation. The modules and the construction they are built on need to be designed to withstand strong winds, large snow accumulations and other events for at least 60 years. At the same time, it should blend into the scenery, interfere as little as possible with the local fauna and flora, and built so that they can be fully dismantled at their end of life, leaving no traces. All these factors lead to increased costs, especially since little experience is available, and a lot of pioneering work needs to be performed.

Next to natural hazards, snow drift represents one of the main challenges towards the structural integrity of the construction. Since steel is one of the main costs drivers for alpine PV-installations [5], designing the mounting structure as lean as possible is one of the main levers to reduce costs. The following optimizations have been made by the different projects:

• Sedrun Solar, Sidenplangg and Madrisasolar all use the Alpin Quattro® system from ZENDRA. It was optimized over the past years thanks to the insights gained from several test sites, as the one from Sedrun Solar. Notably, the legs were inclined such as to be able to remove the cross struts, which revealed to be problematic for birds; the connection between the legs and the ground piles improved to allow more flexibility for adaptations; and various options for cable management tested and improved [3], [6]. These findings could be directly transferred to Madrisasolar and Sidenplangg, which did not need test sites, reducing the overall costs of these projects, despite a payment of license fees [1].
• In Nalp Solar, various types of tables were developed, adapted to the local stress zones within the building site. To assess the latter, an interdisciplinary exchange between various partners and experts, including the SLF, was set up early on, such as to analyze the local snow loads and drifts, and adapt the constructions accordingly. Moreover, a test site was built to gain further insights regarding mechanical stability and construction possibilities. Analyzed questions were, for example, how precise the drilling for the ground piles needs to be, which tolerances can realistically be achieved, and what practical solutions could be implemented to perform the wiring 4-5 m above ground [2].
• Due to hollows on the site of Vorab, the snow accumulations can locally reach up to 8 m of height. Therefore, the wire mounting system Solar Wings from Bartholet was chosen for this site, allowing to span wires with the modules attached across these hollows [1].
• Other mounting systems developed by various alpine projects are presented in a separate article. Next to the options presented above and applied in the sites under construction, the “fir trees” by Helioplant and Turn2Watt, and the table with a “folding mechanism” by BKW are addressing the issue of snow accumulation in innovative ways. The latter is built such that the lower part of the construction can “fold up” in case of a 30-year event (snowfall/drift) predicted by simulations. This allows to decrease the required ground clearance by 1 m [4]. As for the “fir trees”, their cross structure creates wind currents that keep them clear of snow, as explained on their website.

A second major factor affecting the costs are the connections to the road and electricity networks. Being close to existing infrastructure will reduce these costs significantly, while often also helping to get acceptance by the local population [1]. In general, the choice of the building site is the key element regarding most aspects, as well technical issues (natural hazards, connection to grid), as environmental (impact au fauna and flora) and social/political (acceptance by public, permits).

All interviewees mentioned the key role of close exchange with the other projects under construction to exchange experiences and know-how, as well as close collaboration with experts of various fields, such as PV-module manufacturers, environmental engineers and other companies involved in alpine photovoltaics/constructions. Each of these projects is doing pioneering work in a highly complex environment and setting, with still many open questions and challenges. And since they are subsidized up to 60 % by public funds, there is a good reason to share and collaborate with each other, as Mr. Deplazes aptly phrased it [3].

Political uncertainties, for example regarding which exact regulations apply for these pioneering projects, as well as locally varying regulations, sometimes even in conflict with national ones, further add financial risks to the projects. In the case of Madrisasolar, for example, one of the first projects to be submitted, the decision to apply requirements regarding a durability of 100 years for production facilities and 300 years for transformer stations led to the need for massive structures and, consequently, a substantial increase in costs compared to the initial design. To improve the economic planning security of the project, EKZ joined Repower AG and the municipality of Klosters as third partner, allowing the project to be continued [1].

Logistics & agile management

In all interviews, the need for carefully planned logistics and highly agile management was highlighted. The remote locations, often scarce infrastructure and the steep terrain pose challenges to the routing of materials; the long winters, during which building is not possible, further increase the time pressure; and the harsh and unpredictable weather conditions demand high flexibility and security precautions. In addition, the aforementioned pioneering aspect of these projects, combined with a tight time schedule, further increase the need for agility.

Since little experience with such building sites is available, and many challenges are site-specific, on-the-flight adjustments were necessary. The mounting procedure needed to be optimized during the first weeks of construction. In the case of Sedrun Solar, for example, the daily output rose from 5-10 tables per day in the beginning to 20-25 (and a record of 40) by the end of the season, highlighting the steep learning curve of these projects. Next to workflow optimizations, adaptations made were for example increasing the size of the assembly-platform at the arrival of the cable car, or adjusting the rope length between helicopter and freight for efficient and safe placement of the elements [3].

The unpredictability of the weather conditions leads to further need for flexibility. Helicopters can’t fly if there is fog or strong winds. On top of general weather trends, there are also local phenomena, such as strong winds in the afternoon on the site of Sedrun, for example [3]. The daily and hourly work to be performed therefore must be adapted short-term to the actual situation. High flexibility, clear priorities and excellent coordination between the various actors is primordial [2]. To achieve this, the process flow is divided into several stages: drilling and placement of the ground piles, assembly and placement of the legs (primary construction), assembly and placement of the PV-tables (secondary construction), wiring [3]. Some of these require good weather, and therefore need to be prioritized if the conditions are met, while others can also be done in suboptimal conditions.

A further challenge is the uneven terrain. In the case of table-mounted systems, this leads to individualized mounting structures. Hence, the routed materials need to be prepared accordingly, properly labeled and delivered on time. Much time was invested into careful planning of such logistics, which is now paying off [3]. All processes must mesh like clockwork, and early coordination with partners on capacities and practical feasibility were key [2]. Obviously, such a supply chain is quite sensitive. For instance, the corona-pandemic and the war in Ukraine led to unexpected steel supply shortages, creating a bottleneck in the workflow. Luckily, the situation stabilized quickly, but a lesson learned was not to underestimate potential issues in the supply chain [3].

The harsh climatic conditions in the Alps, as well as the terrain and the increased risk for natural disasters not only impacts the requirements towards the construction, but also towards the security of the workers on site. In this field too, collaborating with external experts has proven to be effective: in collaboration with them an occupational safety and health concept was developed, whose implementation is overseen on site by a designated responsible person and supplemented by spot checks conducted by the external company; and so far, no major accidents were reported [3].

A further lesson learned was, that since adaptations during the construction phase are likely, the building application should be submitted in a form that allows for subsequent adjustments [4]. Obviously, this is only possible to a certain extent, but investing some time in this matter is definitely worth it.

Time pressure

The high time pressure was mentioned as a critical point by all project leaders, and alleviating it would have allowed to avoid many errors and reduce costs.

The tight schedule led to risky decisions, as there wasn’t enough time to gather enough data/experience for a founded conclusion. For example, Mr. Maurizio mentioned that they did not have enough time for a detailed geological survey, which now leads to additional expenses. Moreover, they decided to build the transformer stations on an elevated steel construction, to allow passive cooling and protect the soil. Finally, it turned out the required foundations are only marginally smaller than if the whole construction was built directly on the concrete. These additional costs could have been avoided with more time [1]. Or in the case of Sedrun Solar, the number of transformer stations was reduced from 7 to 6 in the course of the project, which also led to additional expenses, which would not have been needed if more time had been available in the early planning phases [3]. In general, various details had to be determined early on, as to submit the building application in time. Unfortunately, once the building permit is issued, the implementation of optimizations thanks to new insights becomes difficult, as they can be considered as deviations from the approved project [4].

Axpo also mentioned that the overlap of various phases, which should be sequential, led to additional expenses. The submission process had to start, before all details were planned, leading to subsequent cumbersome adjustments during the construction phase; planning and execution often had to run in parallel; and additional contracts for transitional solutions had to be set up. In future projects, lower time pressure would allow for a more streamlined process and hence significantly reduce costs and expenses: “In addition to specific adjustments in follow-up projects, the team considers reducing time pressure to be the most important measure. The building application should only be submitted after detailed planning has been completed, and the construction phase should only start after the implementation planning has been finalized. This would allow sufficient time to plan and optimize processes step by step, consider all details in advance and coordinate them with the companies. In this way, costs and expenses – for example, for official applications, contracts or logistics – could be significantly reduced” [2].

Bottom-up approach

A final point mentioned in all interviews was the advantages of a bottom-up approach, involving locally rooted businesses, and collaborating closely with the local governments and population early on. On the one hand, building in alpine regions requires specific know-how and expertise. Local companies are more likely to have this, and can also acquire missing data or experience more quickly, as they are on site. On the other hand, the support of local stakeholders and the population are crucial for the success of such a project. The following procedures were implemented by the various projects:

• Repower had the advantage of already being locally anchored thanks to previous water projects. They also deliberately chose a bottom-up approach during planning, reaching out to the municipality at the start and moving upwards from there, to foster trust and local acceptance. Moreover, a total of 15 businesses, most of them local, are listed on the construction site billboard. Hence, the project has broad support and combines the know-how and expertise of many actors. Internally, an environmental expert played a key role in liaising with authorities and nature conservation organizations, particularly during the approval phase. [1]
• Axpo also deliberately involved the canton and environmental associations early on, which paid off. They also did comprehensive stakeholder consultations, which created acceptance and enabled to resolve conflicting goals early on. In addition, they collaborated with external experts, such as the SLF or PV-module specialists, as building on mountains requires specific expertise in snow, alpine conditions and structural loads. [2]
• Energia Alpina, on their side, are a local company, and the living proof that a small team can achieve great things. They emphasized the importance of collaborating with partners that know the local conditions: building on a mountain or in the lowlands are two completely different challenges. ZENDRA was mentioned as an example of such a small local company, bringing precious competences to the table. Mr. Deplazes also spoke enthusiastically of the good collaboration with local authorities and companies in general, which is greatly appreciated by all project partners. [3]
• For the discarded project of Tschingel, opposition on various levels was one of the factors that led to it being abandoned. Lessons learned are to consider local support (from companies, politics, “Alpschaften” and the population) during the site selection phase; as well as involving partners more into the project. [4]

Open questions

The pioneering aspect of all these projects involves many questions still being open for the time being. Besides practical questions regarding building and structural integrity, two other topics of more general and scientific nature stood out.

The first one being the study of the impact of alpine PV power plants on the local fauna and flora. Many studies have already been performed, others are still ongoing, and further ones will have to be conducted. However, in the current stages, many questions remain open, especially regarding the long-term impacts. In the case of the discarded project, this was particularly relevant, as further studies were requested by the authorities, before deciding on the building permit, which increased the cost and the overall risk of the project [4]. The biodiversity is carefully monitored at the sites under construction, and first results indicate that it could even benefit from these PV fields [7]. Moreover, webcams installed on the test sites took many images of various animals within and around the installations [8]. Cattle seems to even appreciate it, to find shade and shelter, or to scratch against the feet of the construction, as was observed during a project by Zendra and the Plantahof. In the case of the Alpin Quattro® table system, improvements were made specifically to reduce impact on the fauna, such as the removal of the cross struts, which revealed to be problematic for birds [3]. Currently, the “Vogelwarte Sempach” is conducting a broad study on the impact of alpine PV power plants on wildlife and birdlife [2]. Further similar studies would provide valuable data for founded decision-making.

An emerging topic is the influence of UV-radiation on the longevity of PV modules, especially for modules using current dominant cell technologies such as TOPCon. This is particularly relevant for alpine installations, as they are submitted to higher UV radiation doses than their counterparts in the lowlands. Repower mentioned, that more detailed knowledge would be highly beneficial [1]. Studies are ongoing (see this article), but such experiments take a lot of time and effort and many questions remain open at the current stage.

Miscellaneous information

In this section, various considerations are listed, which might be relevant for other future projects.

• Repower decided against the use of central inverters: this has been tested in Italy, but maintenance was found to be complicated. Replacement of failed inverters took a long time (and would likely take even more in an alpine environment), leading to large energy yield losses. [1]
• For NalpSolar, a central air-conditioned technical building was built, containing all inverters and transformers. This presents the advantage of good protection of these components from frost, overheating and other environmental impacts. On the other hand, it leads to long DC-cables. [2]
• In Sedrun, the cable car was built on request of environmental organizations. It led to additional expenses, compared to transporting all materials from the valley by helicopter, but turned out to be a helpful tool. As it can run also in foggy or windy conditions, it provides additional flexibility, which is highly appreciated. [3]
• Simulations of wind patterns, snow drift and snow accumulation are highly complicated, especially, since the presence of the PV construction changes these dynamics. Therefore, measurement data from the sites under construction are looked forward to. So far, snow depth measurements performed by drone by Repower revealed quite homogeneous snow deposition on the site in Madrisa (2-3 m), while large variations were measured on the site in Vorab (1-8 m) [1]. Moreover, measurement on test sites have shown that snow depths and wind speeds inside the field were lower than outside/on its edges [8], [9].

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References

1. Fabio Maurizio, “Interview with Repower: Madrisasolar (under construction) and Solaranlage Vorab (legally authorised),” Oct. 27, 2025.
2. Axpo Solar Schweiz, “Interview with Axpo: NalpSolar (under construction),” Dec. 03, 2025.
3. Claudio Deplazes, “Interview with Provisio: Sedrun Solar (under construction),” Oct. 02, 2025.
4. Urs Guggisberg, “Interview with BKW: Schattenhalb Tschingel (discarded) and MontSol (first instance licence granted),” Sept. 26, 2025.
5. F. Elsener, “Life cycle assessment of a high-altitude photovoltaic power plant in the Swiss Alps,” ZHAW Zürcher Hochschule für Angewandte Wissenschaften, 2024. doi: 10.21256/zhaw-31261.
6. Dominik Schädler, “Challenges of alpine PV Solutions,” online, Oct. 29, 2025. Accessed: Dec. 12, 2025. [Online]. Available: https://alpine-pv.ch/wiki/online-workshop/presentation-slides/
7. Sedrun Solar AG, “Sedrun Solar: Über das Projekt.” Accessed: Dec. 12, 2025. [Online]. Available: https://sedrun-solar.ch/ueber-das-projekt/
8. Stefan Müller-Duss, “Results from the Alpine Testsite Tschingel,” online, Oct. 29, 2025. Accessed: Dec. 12, 2025. [Online]. Available: https://alpine-pv.ch/wiki/online-workshop/presentation-slides/
9. F. Gort, P. Toggweiler, P. Schwer, T. Szacsvay, A. Hügli, and J. Cattin, “Leitfaden zu PV-Kraftwerken in den Alpen,” Swissolar, Apr. 2025. Accessed: Apr. 25, 2025. [Online]. Available: https://www.swissolar.ch/01_wissen/fachwissen/photovoltaik/leitfaeden/250211_leitfaden_alpine-pv-kraftwerke.pdf