Monitoring of pilot projects

^{Created by M.L., OST, on 08.04.2025}

During the planning phase, an off-grid pilot project is often implemented, to test the chosen solutions in real conditions and gather further information on the building site. Hence, compared to the monitoring of an operational power plant, where optimization of production is the main focus, the monitoring of such pilot plants has a more experimental approach.

The different measurements methods are detailed here. In this article, we explore the specific challenges linked to pilot sites (such as the frequent absence of grid connection, for example), as well as insights gained by various operators on their alpine pilot sites and/or power plants.

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One of the main challenges is to develop a mounting system which is robust enough to withstand the harsh conditions of the alpine environment, has minimal impact on the local biodiversity, can be fully dismantled, and is yet economical. Therefore, most pilot projects test several options: a selection of modules is installed on different version of the mounting system. However, this leads to an additional issue: One would like to keep a pilot site small, such as to reduce costs and impact on the site; but to get as close as possible to the real conditions, one would like it as large as possible.

Parameters which are impacted by the size of the installation are for example:

• Wind flow, and with it snow drift and accumulation.      
  The amount of snowfall and peak wind speeds to be expected are highly site dependent and can be measured on site or retrieved from meteorological data. While the snow height at the test site in Mattwald, for example, are usually around 0.5 m, they reach 4 m at the test site in Gries, despite both of them being at roughly the same altitude [1]. However, the local influence of the PV installation on wind flow, snow drift and snow accumulation can be huge, and is difficult to measure on a small site. Hence, simulations are required. Enalpin did wind simulations for Mäsweide with meteotest [1], and the spacing and geometry of the PV “trees” for Gondo Solar were designed to create vortexes keeping them snow free [2].
• Albedo at the center or edge of the PV filed, or outside of it; as well as bifacial yield and row to row shadowing.
  The value of the albedo can also vary locally, depending on snow accumulation for example. Moreover, the amount of irradiation on the back side of the panels depends strongly on the exact surroundings, such as the position and tilt of the next row of PV panels, obstacles and topography. Here too, advanced simulations are required, pushing many tools to their limit [3]. According to several testimonials, Sunwell has proven to be a reliable partner for such simulations [2]. Placing several albedometers throughout the pilot site, and placing a webcam such as to track the shadowing, are methods employed to compare simulations with field results [4–6]. Pilot sites typically have 3 rows of modules, so that the middle ones become representative of a larger installation. According to the results from ZHAW, the upscaling from such an installation is possible with good measurement data. However, having 5-6 rows would allow for more precise computations in the case of low sun positions [7], and precise simulations are required to take into account the complex topography of the Alps [8].

As mentioned, a further challenge often faced is the absence of connection to the electric grid. All monitoring equipment hence has to rely on power from the PV modules and battery storage, rendered even more difficult due to the low temperatures. Many pilot sites rely on lead or lithium batteries within an insulated container [5,9], while others have the privilege to be grid connected [7], or limit themselves to a mechanical test of their solution without power consuming monitoring [1]. The need for heating of the batteries or the whole container has to be determined on a case by case study, depending on the number and the quality of the equipment. In the case of the test site in Davos, for example, the temperature in the container rarely drops below 0 °C, thanks to 15 cm of insulation layer and about 500-1000 W of waste heat from the inverters, computers, over 40 energy meters and further equipment [7]. Hence, no further heating is required, since all the equipment is designed to operate in these temperature range. In order to protect the batteries from freezing temperatures, one could develop an insulated and heated casing for them, or use commercially available salt batteries (for example from Inesco Energy) withstanding temperatures as low as -40 °C [10,11]. The latter actually applies the suggested principle, keeping the temperature of the cell at 250 °C, and emitting roughly 120 W as heat radiation [11]. On top of storage capacity, smart power management allows to extend the autarchy of the system: generally optimizing the power consumption of devices and gradually turning off the heating of less critical devices in case of prolonged periods without sunshine. Webcams can in general go unheated. As for pyranometers, turning off the heating leads to loss of data accuracy, mainly in the early hours of the day, when the dome may be covered by snow, dew or frost. In this case, having the pyranometer within the field of vision of the webcam allows to assess whether its data is accurate or not [2]. To address low temperature challenges while considering power consumption, it is essential to use pyranometers with versatile features. Environmentally innovative pyranometers like the SMP12 are particularly valuable in this regard. With an integrated ring heater and minimal power consumption, the SMP12 ensures maximum data availability at all times [6]. It is recommended to get support from experienced manufacturers to design and build such alpine monitoring systems. For example, Ott HydroMet have access to a wide range of high quality equipment, experience with alpine weather stations, and offer case-by-case advice and project support [6]. On their side, Gantner Instruments have developed an off-grid cabinet monitoring solution, livestreaming the data with a resolution below the second, with an autonomy of more than 5 days and an uptime above 98 %. Their solution also performs I-V measurements, and can usually be delivered within 8-12 weeks, depending on the number of customized adaptations to be made [5].

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References

1. Schmidhalter F. Interview about alpine PV: Enalpin 2025.
2. Cattin J, Bloch L. Interview about alpine PV: Planair, Lac des Toules 2025.
3. Wild M, Anderegg D, Bernhard L, Strebel S, Rohrer J. Comparing measurements and simulations using an adjustable high-alpine photovoltaic array. Solar Energy 2025;287:113228. https://doi.org/10.1016/j.solener.2024.113228.
4. Hügli A. Alpine untility scale PV: Challenges of Constructability and Operations 2025.
5. Sutterlüti J. Interview about alpine PV: Gantner Instruments 2025.
6. Shabani B. Interview about alpine PV: Ott HydroMet 2025.
7. Strebel S. Interview about alpine PV: Test installations of ZHAW (in Davos) 2025.
8. Frischholz Y, Schilt U, Sharma V, Kahl A, Strebel S, Anderegg D, et al. Confirmation of the power gain for solar photovoltaic systems in alpine areas and across scales. Front Energy Res 2024;12:1372680. https://doi.org/10.3389/fenrg.2024.1372680.
9. Knödel B, Müller-Duss S. Interview about alpine PV: BKW, Tschingel 2024.
10. Heinz M. Interview about batteries in cold climate: EMPA 2025.
11. Ursin M. Interview about batteries in cold climate: Inesco Energy 2025.