America's roadways

Opinion: Exploring the Solar Roadways debate

By guest contributor Chris Lee

Any technology with the potential to change the world will be met with almost equal amounts of optimism and pessimism. Solar Roadways, the new road surface technology being produced in Idaho, is a fine example of this.

The technology, produced by a husband and wife team, is taking the internet by storm. Some people are heralding it as a paradigm shift that will revolutionise the way America’s roads work, others are greeting it as another misguided venture eventually destined to fail.

Recently I’ve been exploring the debate in some detail, and the findings are summarised here!

The world’s first Solar Roadways prototype! Image taken from the Solar Roadways website, here.

What is the technology?

The idea is to replace traditional asphalt-based road surfaces with specially designed hexagonal solar panels. The panels will be sturdy enough to withstand the vehicles passing over them, and will take advantage of their almost continuous exposure to the elements by generating solar energy when exposed to sunlight.

Sounds great, what are the issues?

The issues are many. People question whether they will actually be able to support the weight of the vehicles passing over them, whether they will offer traction in wet conditions, how effective their power generation capabilities will be, how much they will cost to produce, as well as questioning many of the company’s claims about the other capabilities of the panels.

In terms of weight, vehicles are unarguably heavy. Highway traffic is relentless and includes trucks and SUVs – will the panels be able to handle it? The first response is to laugh – “no way will glass be able to handle that!”, people say. When you consider that asphalt is a 1.3 on the Moh’s hardness scale though, and that tempered glass is a 5.5-6 (both out of ten), it becomes less silly*.

Thinking about traction, people are concerned that glass will become slippery when wet. This is a fair concern, however Solar Roadways say the panels will have bumpy surfaces to provide necessary traction in all conditions. This then raises the question of whether the bumps will reflect light away and reduce the efficacy of the panels.

Which brings us to the next question: how much power will they be able to generate? Someone on Reddit calculated that even in optimal conditions and if the panels covered all American roads, only 1% of 1% of 1% of the USA’s power output would be able to be generated. These are back-of-the-napkin calculations though – we can safely presume that Solar Roadways have put more thought into this! The power generated will be pumped into the national grid, and able to be allocated as necessary – back to the panels, or to power appliances in the home – from here.

Reddit have also taken their hand to calculating the cost of the panels. A user calculated that the panels would cost $21,257,280,000,000 (twenty-one trillion, two hundred fifty-seven billion, two hundred eighty million dollars) to install across the country – although again this is back-of-the-napkin stuff. The company’s goal is to start small – on driveways and car parks, then scale upwards toward small roads, with highways being the eventual goal, so the cost won’t reach the predicted maximums early on. The Solar Roadways Indiegogo campaign recently raised just over $2,000,000, suggesting that people are willing to invest and see where the technology ends up, and this will allow for the prototypes to be rolled out on smaller targets to gauge their wider viability.

Some of the other claims of the panels’ capabilities are that they will be able to generate heat and melt snow and ice, that they will contain LED lights which can be used to display road markings, and that they will be able to house power cables. Again, bold claims that are being met with mixed reception!

Let’s start with the snow and ice claim. Another Reddit user suggests that “just eight and a half minutes of snowfall [is] capable of being melted by the solar road” per day, and that “it’s a really stupid idea to have solar panels in the snow”. This calculation looks at each panel as a standalone unit, however. Solar Roadways imply that energy generated by panels in sunlight will be able to be directed elsewhere in the grid, so icy panels can receive energy from others to get them back into action.

In terms of road markings, this is one of the less-controversial claims. LED lights require very low energy input, and coordinating lights between panels to display the required markings shouldn’t be too difficult. See the artist’s impression below of what these road markings will look like:

Linked to source

The final point, that power cables will be housed in the panels is again relatively uncontroversial. People who do have issues with this quote the fragility of the panels as the limiting factor, but as mentioned above, tempered glass is actually a very hard material.

What are your thoughts on these panels? Green revolution or misguided fantasy?

* The Moh Hardness scale measures a mineral’s ability to scratch another mineral visible, which is the technical definition for ‘hardness’. The scale is ordinal, which means that there is not a consistent ratio of absolute hardness between items with Moh rating 1 and 2, or 4 and 5, and so on. A more comprehensive solution can be found on the Wikipedia article.

Chris Lee currently writes on behalf of Vantage Leasing, and is interested in development of green technologies. Given our large dependence on finite resources, any technological developments that result in cleaner, safer and more plentiful energy supplies are of great importance to us as a society. Solar Roadways are a great example of the creative process going on in this field, and are exactly the kind of thing Chris enjoys writing about.

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Is alternative energy really the answer? 

2 replies »

  1. // When you consider that asphalt is a 1.3 on the Moh’s hardness scale though, and that tempered glass is a 5.5-6 (both out of ten), it becomes less silly*.//

    Did you come up with that STUPIDITY on your own or did you lift that stupidity from their website? Material hardness has nothing to do with load bearing capability, impact resistance, and other measure of strength. Furthermore, the goo that binds the rock aggregate together has a hardness of 1.5. The rocks in the aggregate average are between 7 and 9 on the moh scale. Don't conflate asphalt (black sticky goo) with *asphalt concrete*.

    Obviously, you don't have a very good hold of the issues here. Another one of your gems is your claims about cost (vastly understated). Assuming a foot of concrete for the road surface, tunnel walls, floor, and footing, the cost is $65 million per mile or almost $300 TRILLION (19 years of GDP). Or the fact that low power LEDs cannot be seen in direct sunlight or at shallow angles…



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