Revising solar roads: is the idea nonetheless too good to be true? – EcoWatch

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Almost as long as solar collectors adorn roofs and barren land, creative people are looking for additional areas that can be covered with energy-generating photovoltaic (PV) panels. The idea was pretty simple: if solar panels generate energy by simply facing the sun, then people could collectively reduce our reliance on coal, oil, gas and other polluting fuels by maximizing our total solar surface area.

So what kind of unobstructed surfaces are being built in every community and between every major city around the world? Highways and roads. With this in mind, the futuristic vision of placing thousands or even millions of solar panels on the asphalt of highways and main roads was born.

While concept art looked like a still from a science fiction movie, many inventors, companies, and investors saw these panels as the golden path to clean energy and profit. Ultimately, however, technology and business failed those behind every solar road project – from the first concepts in the early 2000s to the first actually opened solar road in France in 2016, they all flopped.

In the years since the concept of solar roads went viral, photovoltaic technology has continued to improve and the price has come down. So with a lens for 2021, is it time to recalculate the numbers and see if a solar pavement could possibly deliver on that early promise? We dig in to find out.

Solar roads: the original concept

Solar roads are complex to do, but as simple as they sound to be in concept. They are streets that are “paved” with extremely powerful solar panels that are covered with glass that can withstand environmental pollution and the weight of vehicles driving over them.

The idea was something that really got people excited when Solar Roadways, Inc.'s first project (which is still looking for funding) hit the market in 2014:

More advanced designs included solar lanes fitted with LED lights that could be used to illuminate lane lines, communicate with drivers, and more. Other iterations included weight sensors that would detect when there were obstacles in the road or warn homeowners when unexpected vehicles were approaching their driveway. Embedding this type of technology in the renderings of solar streets only added to their appeal and the initial hype surrounding the concept.

Main selling points of solar roads

Early innovators of solar pavement touted the numerous benefits of their ideas. These included:

  • Sunlight falls on the streets for free, making energy not only readily available, but also free (apart from installation and maintenance).
  • The ability to operate street lights with solar lanes made it superfluous to draw additional energy from the grid.
  • Embedding the electronics in the pavement opened up a world of opportunities for communicating with drivers in a way that didn't require painting and repainting of roads.
  • The ingenuity of adding weight sensors to the solar panels could be used to warn drivers of potential obstacles such as animals, disabled vehicles, or stones on the road.
  • In a future of electric vehicles, the possibilities were seen as even more advantageous, as solar lanes could be used to operate charging stations for electric vehicles or to charge the cars while driving.

While some early thinkers may have also envisioned these streets feeding solar energy into the local power grid, the most powerful way solar streets could use the energy they generate is right around the street: lighting street lamps, heating mechanisms for melting snow on the road, or driving small emergency equipment on the side of the road.

Using the energy for use on the road would mean that the energy does not have to be sent over long distances before being used, which leads to energy losses. In more rural or remote areas, however, it can be of great benefit to make the solar street energy available for nearby homes and businesses, especially if the overall grid fails.

Why solar road tests failed

For a large part of the public – and especially people unfamiliar with the intricacies of solar panels or street structures – solar streets seemed like a slam-dunk solution that looked both futuristic and had benefits that went well beyond just generating electricity . It was the kind of innovation that made people exclaim, “How hasn't anyone done that before ?!” But in reality, the implementation of solar roadways was much more complex than the idea.

Here are some reasons why solar lane tests have failed:

Manufacturing and maintenance costs

The cost of solar energy may be free, but the investment in installing and maintaining the solar roads was undeniably prohibitive. The reason asphalt is used as standard for road construction is because it is immensely affordable and requires little maintenance, which is especially critical on huge, sprawling roads and highways.

In 2010, Scott Brusaw, co-founder of Solar Roadways, Inc. estimated that a square foot of solar pavement would cost about $ 70. However, when the first solar pavement was built in France by a company called Colas, it measured 1 kilometer and cost $ 5.2 million – or about $ 1,585 per foot of road. Of course, this was a small iteration and mass production would cost less, but anyway, it's hard to believe that the cost of a solar pavement could ever be competitive with the price of asphalt, which is around $ 3-15 per square foot would.

In addition, the cost and complexity of sending a crew to repair individual panels that fail would far outweigh the cost of maintaining the asphalt. So while one of the putative benefits of solar pavement is the cost savings associated with self-generated energy, even the backward calculation shows that the numbers simply aren't any cheaper in the long run.

Energy requirement for the production of the panels

Another limiting factor appears when you consider the energy required to manufacture asphalt compared to high-strength glass and solar panels. Most of the asphalt used on roads today is a by-product of the distillation of petroleum oil for products like gasoline, which means it uses a substance that would otherwise be disposed of as waste.

The solar carriageway slabs are supposed to save energy in the long term, but need a lot more to manufacture. Typical rooftop solar panels can easily make up for the extra energy consumed in production, as the glass does not have to withstand the weight of vehicles passing over them, but solar lanes have this added complexity.

Power output of the panels

In estimating power output, early optimists seemed to be making calculations based on the raw surface area they could cover – and not much more. However, aside from the stunted power generation that solar panels face on cloudy days or at night, solar roadways have presented unique new performance challenges.

For example, vehicles that constantly drive on solar lanes would interrupt solar radiation. In addition, they would leave traces of liquid, dirt and dust that can drastically reduce the efficiency of solar panels. Installation on the ground is a challenge in itself as shade would easily find the streets; For this reason, most solar panels can be found on roofs or raised above the ground and tilted towards the sun.

Problems with glass streets

After all, driving on glass surfaces is simply not what modern cars are designed for. Asphalt and tires grip well and are particularly resilient when it is wet. If the asphalt is replaced with glass – even the textured glass used for solar roadways – tire traction could be drastically reduced. Wet or icy conditions can lead to catastrophic situations on solar pavement.

Could recent advances in solar technology bring solar roads closer to reality?

Despite all of these challenges and even more obstacles that early solar road projects have encountered in the past, the reality is that solar technology is constantly improving. In the seven years since Solar Roadways, Inc.'s first video went viral, solar panels have evolved to be more durable, cheaper, and more efficient at converting sunlight into electricity. To put some numbers behind these trends:

  • The average cost of PV modules has decreased by around 70% since 2014.
  • In 2015, FirstSolar made headlines with panels with an efficiency of 18.2%. Today the most advanced prototypes are able to achieve an efficiency of over 45%.
  • The total capacity of solar energy in 2021 is nearly six times higher than it was in 2014, and with this explosion, progress has been made to flatten the learning curve and increase acceptance of the benefits of solar energy among the general public.
  • Solar jobs have grown 167% over the past decade, helping the industry have more skilled workers who can take control of a solar road project and more professionals who know how to install solar panels cheaply.

The question arises as to whether these advances will be enough to lead solar roads from failure to success.

Despite the improvements, many of the original solar road challenges remain and the scope of execution is immense. Even with falling PV costs, equipping long stretches of road with such complex technologies will require enormous capital.

Rather than in a future where solar roads will cover the country from coast to coast, it is more likely that these advances will make solar roads profitable in tight niche applications.

Just as tidal energy is a great opportunity for small coastal communities but cannot be scaled to solve the energy crisis around the world, it is conceivable that limited solar roads will be built around the world. However, large solar roads can never be more than a pipe dream.


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