08.05.2023 | Thirty years ago, Axpo built the largest solar plant of the time in the Swiss Alps

Caischavedra – A giant yesterday, a dwarf today

Jeanette Schranz

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The Caischavedra solar plant above Disentis has been in service for decades – and the solar panels are still producing electricity to this day. The primary drivers behind the construction of the PV power plant was Axpo, formerly known as NOK. Axpo now plans to build the "Ovra Solara Magriel" plant in close proximity. The plant will have with a capacity 100 times higher than Caischavedra – which made records 30 years ago with a capacity of just 100 kilowatts. 

Those smitten with gold fever go to the Surselva in the Canton of Grison during the summer. Since the mid-1990s, gold nuggets of record-breaking size have been fished out of the water in this region. The largest nugget ever found in the Swiss Alps comes from this area. It weighed 1.4 kilograms. But there is not only gold to be found in the Grisons mountains. There is ample sunshine as well – especially during the winter when fog divides Switzerland into "grey below and blue above".

PSI searches for suitable locations

In the mid-1980s, the Paul Scherrer Institute (PSI) was already searching for suitable locations to build a solar-thermal power plant above Disentis. Data was collected from an untouched region on Lai Alv at 2600 metres above sea level above the Caischavedra plateau.

The idea of a thermal power plant was soon abandoned owing to technical obstacles. However, the measured irradiation values indicate: the prerequisites for a solar plant are ideal. The area is above the fog line, the sun reflects off the snow, and the temperatures are low. These are the ideal ingredients for the construction of alpine PV plants and make them very valuable for solar power generation – especially for winter power supply.

NOK and Co. take action

The location is suitable. Now it's a question of pioneering spirit on the part of the energy companies and local policy-makers. Axpo (formerly NOK), the Elektrizitätswerk Bündner Oberland, the Disentis mountain railway, as well as the town of Disentis/Muster establish the construction and operations company Desertasol in 1991.

NOK holds a share of 26 per cent in Desertasol (Axpo holds no shares today) and together with the Federal Government and the Canton of Grisons the necessary funds to realise the project are made available. 

Using existing infrastructure

However, the new solar power plant is not built in the untouched region of Lai Alv. In order to protect the environment and for an efficient grid connection, the parties decide to connect the plant to the existing infrastructure of the Caischavedra mountain railway at 1900 metres a.s.l. 

The plant will have a capacity of 100 kilowatts and deliver nearly 120,000 kilowatt-hours (kWh) of electricity annually. In doing so, the parties pursue a mission to build the largest solar power plant of its time in the Swiss Alps.

Today, 100 kilowatts seems paltry in comparison to the capacity of today's alpine solar plants. As a comparison: The large-scale solar plant on the Muttsee dam, AlpinSolar, has a capacity of 2200 kilowatts and produces 3.3 million kWh per year. The planned ground-mounted plant NalpSolar in Tujetsch in the Canton of Grisons is designed for a capacity of 10,000 kilowatts and will produce 13 million kWh of electricity annually. The most recent project, the plant at La Motta is also designed for a capacity of 10,000 kilowatts and should produce 17 million kWh of electricity yearly. The "Ovra Solara Magriel" plant will be built just a few metres in linear distance to the small Caischavedra plant. The venture has come full circle.

New module types – NOK fastening technology

Of course Caischavedra remains a dwarf in comparison to its future neighbour, but that does not diminish the relevance of this pioneer plant. NOK and Co. did not only go in new directions in terms of size: In the fall of 1992 the solar modules are installed. The special feature: They are much larger than those commonly used in solar technology at the time. They reduce installation costs and allow snow to slide off easily.

The new type is about two square metres in size and weighs 50 kilos. Together the modules weigh about 110 tonnes. The heavy panels require special installation. With partners, NOK develops a new fastening technique that attaches the module itself rather than its edge, which is the conventional method at the time. The new technology reduces the danger of panel deformation. We still benefit from this pioneering, innovative achievement today. And: Knowing that an alpine solar plant can still reliably produce power after 30 years of operation is at least as valuable as the heaviest gold nugget ever found in the Surselva.

Production started in June 1993. The generated electricity is fed into the grid of the Elektrizitätswerk Bündner Oberland and directly supplies the Disentis mountain railway with power – to this day. 

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