Roadways and roadway right-of-ways (ROWs) have been sites for experimenting with renewable energy for over 70 years. In 1948 a bridge on US 97 over a canal in Klamath Falls, Oregon utilized geothermal de-icing to address a traffic safety issue on an intersection with a steep grade. The first solar highway project in the U.S. came on line in 2008 in Oregon. Known as "Oregon's Solar Highway Demonstration Project," a 104-kW ground-mounted solar array was installed on highway ROW at the interchange of I-5 and I-205 (see Figure 1). Although a bit dated (2017), the Federal Highway Administration has a good summary on
alternative uses of highway ROW that describes the various renewable energy technologies and alternative fuel facilities that have been, or have the potential to be, accommodated in highway ROWs.
Even more challenging is the concept of a solar roadway in which the road surface is used to collect solar energy. At first glance, this concept seems to make a lot of sense. There are a lot of roadways in the world that receive a lot of sunlight which could power solar panels, plus roads, like solar panels, are pretty flat. A number of companies jumped into the technology, and there have been several demonstration projects around the world. Unfortunately, the technology that seemed promising in the 2014 to 2016 timeframe has pretty much led to real world failures:
- A demonstration bicycle lane consisting of a 230-foot stretch of road embedded with solar cells protected by two layers of safety glass was opened in the Netherlands in November 2014 (see Figure 2). Each square meter of road was intended to generate 50-70 kilowatt hours of energy per year. In its first year the road performed better than developers expected and produced more than 9,000 kW-hrs of energy, which was enough to power three small households for one year. However, this was only half as much as a solar roof system in the same location would produce at a significantly higher price. Although successful as a demonstration project, it appears unlikely to be an effective or efficient source of power.
- In 2016 the Wattway Solar Road was opened in Normandy, France, as demonstration of technology that was envisioned to be used to pave 1,000km of road with photovoltaic panels in the subsequent five years. The demonstration roadway used a new product called Wattway Panels (see Figure 3), developed by Calas, a subsidiary of Bouygues, one of the largest construction companies in the world. These panels were marketed as being resistant to the passage of heavy goods vehicles and with sufficient traction to prevent skids. The goal of the full program, if successful, was to furnish enough electricity to light the homes of 5 million people, or about 8% of the French population. Unfortunately, the design didn't take into account such mundane issues as rotting leaves which blocked sunlight and reduced power output, and the panels turned out to be quite noisy at even moderate speeds. And within two years after start-up, the road began to break apart and its capacity declined rapidly.
- A stretch of historic US Hwy 66 was set to become the first solar roadway in the United States by the end of 2016, installed along a short stretch of sidewalk in front of the visitor center in Conway, Missouri. Electricity generated was planned to be used to power the visitor center, and, if successful, the test would have been expanded to include the center's parking lot. The panels for the test were tp be provided by Solar Roadways, an Idaho start-up company that has developed its modular, glass roadway solar panels under grants from the US Department of Transportation, plus a successful Indiegogo campaign. They describe their product as "a modular system of specially engineered solar panels that can be walked and driven upon. Our panels contain LED lights to create lines and signage without paint. They contain heating elements to prevent snow and ice accumulation. The panels have microprocessors, which makes them intelligent. This allows the panels to communicate with each other, a central control station, and vehicles." Unfortunately, at the end of 2017 the project hit a contractual snag and was cancelled with no real explanation as to what happened.
- In what was advertised as a game-changer for the technology, China opened a 1-kilometer long solar road in Jinan, the capitol of Shandong province south of Beijing, in December 2017, capable of generating 1 GWh per year. However, five days after opening, it was reported that thieves stole several of the solar panels, and the road was shut down. Further investigation showed that it was more likely that the panels had been damaged, possibly by items that fell from passing vehicles. Although, the damage was repaired, and the road was reported as performing well, the fact that there has been no news regarding performance for several years is suspicious..
Again, there are many critics and estimates that such roadways will cost six times the cost of rooftop solar on a per kWh basis (see Video 1). The Chinese roadway is reported to have cost approximately 90 times the cost of a typical road. A good summary of the issues associated with the concept is given in
Solar Roads:will they ever come?. Despite all the problems, one must admit that solar roadways are a really cool idea, and the video prepared for the Route 66 project, "Solar Freakin' Roadways" is well worth watching for entertainment value, if nothing else! (see Video 2).
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