In 2022, the Swiss Parliament introduced a temporary amendment to the Energy Act, allowing for a one-time subsidy of up to 60% of the investment costs for large photovoltaic systems. Subsidies are subject to technical requirements such as a minimum power yield of 500 kWh/kWp in the winter season (October to March), a level typically only achieved by PV systems in the Alpine region of Switzerland. The amendments to the Energy Act were limited until 2025.
The introduction of the new subsidy scheme initiated a lot of alpine photovoltaic projects. However, the realization of alpine PV plants faces a special challenge compared to plants on the Swiss Plateau. In the Alps, wind loads are higher, snow drifts occur, temperature cycles are faster, temperature amplitudes are larger, and at the same time, the irradiation of energy-rich UV light is increased. This results in additional requirements for the module design, the supporting structure, the system technology, the maintenance and the operational management of such systems.
Due to the lack of knowledge and the time pressure for realizing the alpine projects, the objective of this project was to support implementation partners by collecting all available data, bringing together the information, making the information available at one point and answering open emerging research questions.
In the project numerous discussions with implementation partners took place, for instance about the best suited modules, possible new degradation effects, about the requirements for the sub-constructions, and the effect of high irradiance levels on the safety and longevity of the system. It has been found that the successful realization and operation of alpine PV systems depend not only on the correct selection of PV components, but above all on the way the project is carried out and organised. Close collaboration and information exchange between different implementation partners, authorities, and research partners is of high importance.
High upfront costs (e.g. mounting systems, logistics, grid connection, and evolving documentation requirements) often must be incurred before a construction decision is made, creating financial risk and leading to potential project cancellations. Ongoing uncertainty about whether projects will proceed has weakened cross-project collaboration, shifting the focus from cooperation toward minimizing planning costs.
In this project, a webpage (https://alpine-pv.ch/) was created for a fast dissemination of knowledge around alpine PV systems featuring a map section showing all alpine PV plants in Switzerland, including those in the planning stage, under construction, or discarded [1]. The most important technical data and photos were collected from various public sources, such as press releases.
This webpage allows statistical analyses of project status and costs and provides a comprehensive collection of knowledge on alpine PV systems, including results generated within the project.
As part of the project, workshops were organised with implementation partners, which contributed to an exchange of information and were well received by the participants.
The realization of alpine PV systems seems feasible, when high investment costs are accepted. However, some technical challenges and questions remain. The high UV radiance in the alps is expected to result in a higher degradation rate compared to systems in the Swiss Plateau, and short-term high irradiation values that exceed the usual values by far may lead to inverter failures or possible safety risks under certain circumstances.
Main findings/results («Take-Home Messages»)
- The key point of the project is that a broad variety of information concerning alpine PV-Systems is provided at one single point with the webpage https://alpine-pv.ch/. Moreover, the implementation of alpine PV systems was supported by technical discussions bringing in the joint expertise in photovoltaics of the four involved Universities of Applied Sciences and all the actors contacted during this project. Even though the focus was not on technical research, new technical findings have been accomplished within the framework of this project, for instance concerning module requirements for alpine systems.
- In principle, the technical challenges posed by alpine facilities can be overcome; however, in some cases at very high cost. Typical costs for the alpine systems are in the range of 2500 to 5000 CHF/kWp. It remains to be seen whether the facilities will be durable under alpine conditions and how high the maintenance costs will be.
- Due to the high costs and the resulting low returns, uncertainties in project development are particularly critical. There are reports of certain projects, particularly during the planning phase, where changing and growing requirements on the part of the authorities have led to projects being abandoned for risk reasons.
- The increased irradiation and UV levels in the Alps, compared to the Swiss Plateau, highlight the importance of UV resistance of PV modules and their materials. UV ageing tests conducted in this project reveal that current alpine-related modules exhibit significant UV-induced degradation of solar cells. While an outdoor observation supports these results, additional outdoor performance studies are necessary to strengthen the laboratory outcomes.
- Bifacial irradiation reaches up to 2.4 kW/m². None of the plant operators contacted take this into account in their inverter design. This systematically violates installation and safety standards. At this point in time, it is not yet possible to say whether the standards are too strict or the plant design is incorrect. The issue has been raised in the relevant standards committee (IEC TC 82) and will be discussed in the future.
