Swiss ‘solar rails’ pilot puts removable PV between tracks

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On a quiet 100 meter stretch of track in western Switzerland, an experiment is underway that could redefine how railways contribute to the energy transition: a removable “solar carpet” laid between the rails and generating power every time the sun comes out.

A world-first test bed in the Neuchâtel mountains

The pilot project, developed by Swiss cleantech startup Sun-Ways, is installed near the village of Buttes in the canton of Neuchâtel. Publicly available information shows that 48 photovoltaic modules have been mounted between the rails on a section of active line, with trains continuing to run overhead at normal speed.

The system has been authorized as a removable solar power plant on an operational railway, described in industry coverage as the first of its kind. The trial section is relatively short, but it is intended as a proof of concept for a much larger opportunity across Switzerland’s largely electrified rail network.

The plant, which was switched on in 2025 after federal transport authorities granted approval the previous year, is designed to remain in place for a three year test phase. During this period, engineers and researchers are tracking performance, weather resilience and how the solar hardware coexists with demanding railway operating conditions.

Reports indicate that the array is dimensioned to withstand trains traveling up to around 150 kilometers per hour. More than ten thousand train passages have already been logged over the installation, according to recent public updates, without reported safety incidents on the test segment.

How the ‘solar carpet’ between the rails works

Instead of building ground mounted solar farms or rooftop systems, the Sun-Ways concept places modules in the unused ballast space between the rails. The modules are pre assembled into narrow mats that match the rail gauge and are fixed to the sleepers using a patented mechanical anchoring device.

The technology is designed so that the panels do not carry any vehicle load. Trains run on the rails as usual, while the solar elements sit slightly recessed between them. The layout keeps the PV surfaces low enough to avoid interference with wheels and braking systems, but high enough to limit the accumulation of ballast and debris.

A key feature highlighted in technical descriptions is removability. The anchoring system allows teams to lift out individual panels or whole sections in a short time window to carry out sleeper replacement, welding work or other track maintenance. A specialized laying train developed with a Swiss rail equipment manufacturer can reportedly install up to around 1,000 square meters of panels per day by unrolling the modules “like a carpet.”

The modules are conventional crystalline silicon units adapted for the harsh rail environment, including vibration resistance and anti slip, anti glare surfaces on the upper layer. In the Buttes pilot, generated electricity currently feeds into the local grid, but the project partners are also studying direct connection to the traction power system in future phases.

Energy potential and early performance signals

On the 100 meter demonstration stretch, annual production is modest in absolute terms, on the order of tens of thousands of kilowatt hours per year. Yet the strategic interest lies in the scale of Switzerland’s rail network, which spans roughly 5,000 kilometers of track when regional and national lines are included.

Company projections cited in specialized energy and rail publications suggest that widespread deployment between the rails could yield up to around 1 terawatt hour of electricity annually. That figure would represent approximately 2 percent of Switzerland’s current electricity consumption and is comparable to the power demand of several hundred thousand households.

Because the panels are mounted flat and at ground level, projected yields per square meter are lower than optimally tilted rooftop or hillside arrays. However, advocates argue that the ability to reuse existing transport corridors without occupying new land or altering scenic landscapes compensates for the efficiency trade off, especially in a country where space is tightly contested.

Recent summaries of the first year of operation indicate that the plant has met its initial technical objectives, particularly regarding mechanical stability and compatibility with train operations. Ongoing measurements are focusing on degradation, soiling from dust and grease, and the effect of snow and frost on both safety and energy output through Swiss winters.

Safety, maintenance and environmental questions

From the outset, regulators and infrastructure managers have highlighted safety and maintainability as central concerns. The three year test program near Buttes is therefore structured as much around risk assessment as around energy generation, with parameters such as glare, emergency braking, track inspection access and fire behavior all under scrutiny.

Anti reflective surface treatments are being used to minimize reflections that could distract train drivers or nearby road traffic. The removable design is aimed at addressing worries that fixed solar hardware could obstruct visual inspections or complicate the use of tamping, grinding and welding machines along the line.

Cleaning and fouling are also under analysis. Industry reporting notes that passing trains create a partial self cleaning effect by generating air movement over the panels, but detailed monitoring is in place to quantify the impact of ballast dust, oil residues and winter de icing agents on output and lifespan.

Environmental groups and energy analysts following the trial have raised broader questions familiar from earlier “solar road” experiments in Europe and elsewhere, some of which encountered severe durability and economic challenges. The Swiss approach differs by avoiding direct vehicle loading on the glass and by deploying only on relatively smooth, controlled rail ballast instead of open road surfaces, but long term durability data are still being collected.

Beyond Switzerland: a possible model for rail corridors worldwide

The Buttes project has attracted interest from foreign rail operators and energy planners looking for ways to scale solar generation without creating new conflicts over land use. Public documents show that Sun-Ways has entered into a collaboration with the French railway group SNCF to prepare tests of the technology on sections of line in France.

Studies published in recent years on solar installations near or within rail corridors point to significant theoretical potential along electrified mainlines globally, particularly where corridors cut through densely populated regions short on available space for new renewables capacity.

At the same time, experts caution that business cases will depend heavily on installation and maintenance costs, panel lifetimes in a rail environment and the value of power generated close to high voltage traction infrastructure and urban demand centers. The Swiss pilot is therefore being watched not only as a technological trial, but also as a test of financial viability for operators under pressure to decarbonize.

If the three year test confirms robust performance, the concept could progress from a single mountain valley in Neuchâtel to longer stretches on busy mainlines, and eventually to networks beyond Switzerland’s borders. For now, the short glint of glass between the rails at Buttes remains a compact illustration of how transit infrastructure might double as a power plant in a climate constrained era.