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However, there were concrete reasons why we still wanted the project. At almost 2500m asl, the productivity of solar plants per unit area is about 50% higher than on the Swiss Plateau. PV systems on the Swiss Plateau only generate a quarter of their output in winter whereas about half of the potential Muttsee production occurs in the winter half-year - when electricity demand is high. The reasons for this are the numerous hours of sunshine in the fog-free mountains in winter, the additional yields due to the reflection of light from the snow present here, and the lower temperatures as panel efficiency is temperature- dependent. It was thus foreseeable that such alpine systems could become very attractive in the longer term – as soon as the assumed electricity shortage in winter would be reflected in electricity prices and as soon as the construction of large PV systems in the Alps would become legally possible.


A changed environment Much faster than anybody thought, the environment


for alpine solar installations is changing. Prices are high and the Swiss parliament seems to be ready to relax the conditions for installing panels in the Alps. PV on infrastructure (such as in the Muttsee case) should be supplemented with PV near existing grid and road infrastructure (near hydropower plants, ski areas and the like). The lack of profitability of the specific project, but good prospects for follow-up projects and the desire to gain experience had already led Axpo to cooperate with IWB, the utility of the city of Basel. It was Planeco, IWB’s PV subsidiary, which built the plant together with the subcontractors. The two investors were joined by the Swiss discounter Denner, which secured the entire production over 20 years in a power purchase agreement.


Once the cooperation between IWB and Axpo, the supply contract with Denner and the work contract with Planeco were in place, and Axpo and IWB had approved the investment, we could begin. Due to the extreme weather conditions and the large amounts of snow, construction can only be carried out in summer and autumn until the snow has fallen. The spring of 2021 was very snowy and then the weather afterwards often rainy. So, what exactly is it that makes working in the high mountains really demanding? The main answer is the snow that interrupts construction activity in winter. It can cover the panels (hence the steep arrangement and the free space at the base of the wall) and cause frost damage by thawing and freezing of snow and ice. A second point is access, which was only possible here by helicopter.


However, that was not the reason for the delays in construction. These were caused by pandemic- related delivery difficulties in obtaining materials, such as the primary substructure of the plant, which fixes the panels at a distance of 1.5m in front of the wall. As a result, the site had to be winterised towards the end of 2021 and the work completed in the summer of 2022.


Future projects Hydropower is the most important pillar of Swiss


electricity generation, with photovoltaics likely to become number two in the longer term. While, from


Muttsee AlpinSolar - Overview Location


Place Exposure Slope Distance


Technical data Installed capacity


Expected yield


Surface area Modules Inverters


Transformers Technical centre


Muttsee dam (lake max. 2474 m above sea level), Glarus South, Canton Glarus, Switzerland


South-southeast to south-southwest


Wall: 90° at top, 51° at bottom Panels: 65° at top, 51° at bottom


Distance between wall and panels: 1.5m (variable in the upper area)


Area without panels at the base of the wall: approx. 5 m (due to snow accumulation)


2.184MWp


4116 modules of 460 and 756 modules of 385Wp 3.3 GWh/yr


Specific yield of 1500KWh/kWp, radiation conditions as in southern Europe


Approx. 10,000 m2


Bifacial glass-glass modules Mono HiR Half-cut (Megasol) 23 units, rated power / max. power 99.9 / 105 kVA (Kaco) 2 units, 1250kVA each (Rauscher & Stöcklin)


Inverters, transformers, switchgear, etc. in new technical centre (new building next to an existing structure of the hydropower plant)


Economic data Investment volume Approx. CHF 8 million Owners, partners & suppliers Shareholders


Electricity customer


Planning services Construction


Axpo (51%), IWB (49%) Denner


20 years, total electricity volume, fixed price in PPA contract Axpo, energiebüro (solar planner), Lombardi, Gröber etc. Planeco with subcontractors Crestageo, Mettler Prader, etc.


the energy industry’s point of view, increased storage facilities for hydropower in Switzerland are particularly valuable (e.g. projects to raise dams), the general production issue in Switzerland is winter electricity: in summer there are surpluses, in winter there is a need to import (but the capacity ability to import is limited), and this imbalance is likely to worsen as more nuclear power plants are shut down and more conventional PV (with a production share in the winter season of a good 25%) is added. From this point of view, alpine PV plants are very desirable – even more so as wind power (with its high winter share) has had an extremely difficult time in Switzerland so far.


Potential Muttsee AlpinSolar was borderline from a profitability


point of view, and the potential for alpine plants that could actually be built was initially very low. With current electricity prices, profitability looks very different, and the planned changes in the law should make PV plants possible at many alpine locations. The location at a dam is likely to be the exception, but hydropower plants have considerable potential for new alpine PV plants due to their existing infrastructure ( ie electricity and road connections in the high alpine region). ●


Above: The author is Christian Heierli, Investment & Regulatory Management, Axpo Solutions AG, Baden, Switzerland


www.waterpowermagazine.com | November 2022 | 17


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