Swiss test facility determines very high winter yields of alpine solar power plants

An experimental plant operated by the Zurich University of Applied Sciences (ZHAW) at an altitude of 2,500 meters in the Swiss ski resort of Davos-Parsenn has produced electricity yields far above the Swiss average during five years of measurement operation. Especially in the winter half-year from October to March, up to three and a half times more electricity was generated than with plants at lower altitudes.
The measured annual yields of the south-facing modules differed significantly depending on the vertical inclination (30, 60 or 90 degrees) and module type (mono- or bifacial), but were consistently above average. While the average annual yield of a comparison system with monofacial modules and 20 to 30 degree tilt was 917 kilowatt-hours per kilowatt of power (kWh/kW) from January 2018 to December 2022, slightly below the Swiss average of 956 kWh/kW, the experimental system with bifacial modules and 60 degree tilt measured an annual average of 1,851 kWh/kW, twice as high. Other configurations were also well above average, ranging from 1,329 kWh/kW (90 degree monofacial) to 1,703 kWh/kW (90 degree bifacial). In the summer half-year, the alpine test plant achieved 615 to 975 kWh/kW, the comparison plant 670 kWh. The differences were even more significant in the winter half-year: The comparison plant achieved 247 kWh/kW, while the experimental plant achieved 580 to 885 kWh/kW.
In the view of the ZHAW research group, steep inclination angles have several advantages for alpine plants: rapid sliding of snow, good utilization of the solar radiation reflected from the surroundings (albedo) and high yields in the winter half-year. This could relieve the burden on hydropower plants, which are less productive at this time of year due to low reservoir levels.
In addition to the albedo, the ZHAW cites the scarcely existing impairment by high fog at this altitude as the main reason for the high yields. Until next year, the influence of the distances between the module rows in a solar power plant on the usability of the albedo will be investigated. It can be assumed that the yields in a real plant are lower than in the free-standing experimental setup.
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