Striding Into the Future on Solar Sidewalks

Kamloops, British Columbia, is a radiant place, receiving over 3,100 hours of sunshine a year. So it’s no wonder that in 2016, Thompson Rivers University (TRU) decided to harness all that luminescence and convert it to electricity.

If the university’s solar array had been installed on a roof or mounted above ground in a corner of a soccer field, that probably would have been the end of the story. Instead, TRU didn’t follow trends — it set one: It became the first place in Canada to embed solar panels into the ground. By 2017, a 12-meter walkway with 16 solar modules near the campus daycare, together with a compass (sunburst) design of 62 modules in front of the arts and education building, were producing power. By its second summer of operation, the compass produced enough electricity to power an entire classroom of computers at TRU’s arts and education building for the day.

For Amie Schellenberg, an electrical instructor at TRU and part of the team that spearheaded the sidewalks, ground-mounted solar arrays just make sense.

“Why wouldn’t we use the space we already have?”  she asks. “We don’t need to create new space, or repurpose anything. We don’t need to plow fields or redo rooftops — the ground is there.” Historically, solar panels have been mounted above ground, typically on roofs or in gigantic solar parks. But wide-open spaces and sunlit rooftops aren’t always an option in cities.

“It’s hard to integrate traditional rooftop solar into urban centers,” says Gilbert Michaud, chair of the American Solar Energy Society’s policy division. “Buildings shade each other and condo buildings may have restricted HOA policies. It makes it really hard for people in urban environments to install solar, even though population centers have a demand for cool energy and want to see it.”

This is where in-ground solar shines. In 2021, the city of Barcelona installed Spain’s first photovoltaic (PV) pavement as part of the city’s goal to become climate neutral by 2030. In the Netherlands, an embedded 400-meter solar sidewalk in front of Groningen Town Hall is powering the building as part of that city’s ambition of becoming CO2 neutral by 2035. The project is part of the European Union’s Making City project, which aims to develop positive energy districts (PEDs) that demonstrate innovative solutions to tackle climate-neutral goals. The 400-square-meter installation is projected to offset approximately 18 tons of CO2 annually. “It is an example of how to use space in the city in a smart and sustainable way,” Philip Broeksma, councilor of energy from the Municipality of Groningen said when the sidewalks were revealed in 2023.

With places around the world looking to produce more solar energy, the question is: Can in-ground solar be scaled to meet demand?

Most solar installs are fixed tilts at a 45-degree angle, Michaud explains. “Larger installations [such as solar farms] move with the sun to capture as much light as possible. A horizontal sidewalk is much less efficient,” he says.

Not everyone agrees. Pavegen, a U.K.-based company, has combined the concept of in-ground solar tiles with the kinetic energy generated by people’s footsteps. When someone walks across the tile, a mechanism underneath it triggers an electric current that generates power.

“An example of kinetic [foot power] alone in Yosemite National Park has exceeded 35 million joules of energy. That’s equivalent to around 9,000 kilometers on an e-bike, or 10,000 hours of talk-time on a standard smartphone,” says Paul Price, head of marketing and communications for Pavegen. “When the tiles capture solar energy, they generate 30 times more.”

Pavegen’s Solar+ system, which uses the combined power of solar energy and kinetic energy, is poised for large-scale distribution this fall. Suited for integration into school campuses and city promenades, it will be able to power everything from LED streetlights to digital devices.

But how durable is the surface of a solar panel? The solar paths at TRU were covered with an epoxy and finished with a gritty, anti-slip surface that felt spongy to walk on, but this still wasn’t enough to protect the array from a Canadian winter.

“We do get snow every winter,” Schellenberg says. “And to be honest, every year, something new happened, whether it was a piece of rail that lifted off, or a couple of fasteners, or there was some water seepage underneath.”

Since the installation of TRU’s sidewalks, technology has advanced, and according to Price, companies such as Pavegen now design installations with integrated drainage channels beneath the sub-frame, ensuring water flows away efficiently and doesn’t compromise performance or safety. But despite this, installing inground solar tiles is no easy feat.

At TRU, troughs had to be cut into the concrete for wires that connect the array to the university’s electrical grid. Solar panels generate DC (direct current) electricity, so an inverter cabinet, to convert the current to usable AC (alternating current), was installed inside the arts and education building. These infrastructure changes aren’t cheap. A sustainability grant of $35,000 Canadian from the university covered the cost, not including the panels, which were donated. Schellenberg says the power generated from the sidewalks has offset this cost and it all has broken even financially. Still, she and Michaud concur that, as things stand now, in-ground solar in North America can be expensive and may lack electrical efficiency. The good news is that they both see change on the horizon.  

“As the technology gets better, costs go down, and as policies are adopted, including tax credits, it becomes much more feasible,” Michaud says. Schellenberg imagines unlimited possibilities for the technology, both big and small. “An unused corner of a Walmart parking lot could become a solar-generating hub,” she muses.

In fact, this is an idea that has already reaped dividends in Moult, France. The Lidl supermarket has installed 50 square meters of in-ground solar panels in a back corner of its parking lot to reduce its energy bill. In one year, the panels produced the equivalent of 7,000 hours of use for five cash registers.

As fossil fuel-powered vehicles become antiquated and EVs increase in popularity, Schellenberg sees wireless in-ground solar EV charging stations becoming commonplace. “This could be the boost that those EVs need to make it the next 100 kilometers,” she notes.

In Amsterdam and Paris, this is already proving successful. Select bus stops and terminals are embedded with solar panels that collect energy and store it in batteries below the surface. As an electric bus pulls into the stop to pick up passengers, it’s able to draw power from the embedded system and top up its charge without needing to return to the central depot. A single charging point can produce 15 to 20 kilowatt-hours per day, enough to power a bus for several kilometers. At TRU, the in-ground solar arrays were a prototype and never meant to produce a lot of power. In the six years they were operational (2016 to 2022), they generated just enough electricity to power a single home for half a year. To put this into perspective, Topaz Solar Farm in San Luis Obispo County, California, is the largest in the U.S., spanning 4,700 acres. Over nine million above-ground mounted solar panels supply power to approximately 180,000 homes.

By 2023, the sidewalks had stopped producing power and couldn’t be maintained, but they weren’t removed. Schellenberg hopes that when people see them, they are inspired to think outside the box. She’s proud of the project and doesn’t measure its success in kilowatt hours but rather in what’s possible when it comes to renewable energy solutions. “It is another extension of finding ways to solve problems,” she says.

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