Written by James Hinton
Last year I wrote a piece discussing the possible use of solar panels as road surfaces. In it I discussed a project by engineer Scott Brusaw intended to take our decaying roadways, contributors to climate change, and repurpose them to become part of the solution. Solar power generating roadways, he argued, could virtually eliminate dependence on carbon emitting fossil fuels for decades to come.
The article generated a good bit of discussion as both supporters of the concept and detractors weighed in on a healthy debate over the project. Supporters backed the confidence of Norwich Civil Engineering professor Edwin Schmeckpeper. Opponents, however, remained unconvinced. Ultimately, the disagreement between the two sides came down to one simple problem, a lack of hard data to support or rebuff the concept.
We now have numbers, though they did not come from Solar Roadways. Instead, they come from a project in Europe. A consortium of companies working together constructed the SolaRoad along a bike path in the Netherlands’ village of Krommenie. The solar panel portion, covering half the width of the path, stretches for 70 meters (230 feet) and is 1.25 meters wide (4 feet). The other half lacks panels and is being used as a “control” surface to compare wear and tear of conventional road surfaces. It was “turned on” and opened to the public on November 12th.
The initial predictions were that a 100 meter long bike path could power 2 houses over the course of a year. According to a May 7 press release covering a review of the first six months of data, the path had already generated 3,000 kWh, enough to power one home for a full year while being only 70% as long as the initial plan. This represents a performance 43% better than expectations.
It was not all good news, however. The first six months revealed there was still work to do to make the project viable. Subjected only to foot and bicycle traffic and the relatively kind weather of the Low Countries, sections of the path suffered from delamination separating the panels from their protective coating.
Further, SolaRoad admits that the current cost is not yet within a practical range, though it has been cautious about stating actual costs. So far SolaRoad has invested €3.5 million ($4 million U.S.) on the project, but this cost includes the entire budget, including 5 years developing a panel design in the first place. The bike path in the Netherlands “represents just a small part of this”.
SolaRoad expects that both of these problems will be overcome soon. Krommenie is specifically being used as a three year long test, during which improvements will be made as solutions to problems are developed. The goal is to achieve panels that will achieve a zero-sum cost at 15 years of use (with an expected lifespan of 20+ years). SolaRoad is already testing possible solutions to the delamination issue while exploring how improved manufacturing and mass production methods can drastically reduce costs.
In this, solar power generating roadways are following an already well demonstrated path. When solar power first went commercial it was still prohibitively expensive for all but the most idealistic of well off home owners. The average solar panel in 1980 cost $21 per watt. Today, even with 25 years of inflation, improved design and increased mass production has dropped that price to $1 per watt.
Now that we have some numbers, however, we now need to translate what they mean in practical terms. SolaRoad’s numbers were based around a single person home in the Netherlands, using 3,000 kWh of power annually. What would this look like in the U.S.?
The per capita use of electricity in the U.S. comes out to just shy of 12,000 kWh per person. By comparison, in the Netherlands it’s a little over half of that, at 6,750 kWh. If we assume that SolaRoad’s road remains static in terms of their output (instead of improving as happened with solar panels from 1980 to today), it will require roughly 560 square feet of paneling per American to meet our electricity needs.
The average residential roadway in the U.S. has lanes 9-12 feet wide. Even assuming a very narrow, tight 9 foot “average” residential lane, only 58 feet of lane is needed to equal that “average American.” Add in sidewalks and bike paths (a-la SolaRoad) as well as gutters for drainage, and it drops to about 40 feet. These numbers grow even smaller when you start extending this project to non-residential roads, such as three lane highways and four-plus lane interstates.
These numbers can drop even further when combined with other green energy initiatives gaining steam in the U.S. The typical incandescent light bulb has a life span of 1,200 hours and uses 60 W of electricity. Fortunately, it only costs a buck. An LED replacement bulb is going to cost $79.96 to purchase, will last 30,000 hours (three and a half years of constant use!), and only use 13 W of electricity. When you take into account replacement costs for incandescent bulbs, the LED is three times the price, but that one bulb is going to save you 1,400 kW of electricity. At the average cost of electricity in New England, that’s a savings of $292.15 over the lifetime of that LED for a net profit of $242.15.
That is the savings from a single light bulb. When you look at the total savings of new, energy efficient homes over older pre-green movement homes, the average home uses 3,500 kWh less every year. Application of the same building and maintenance practices across business and industry means that, ultimately, the typical American could come down to needing a mere 9,000 kWh/year. Now we’re looking at 30 feet (360 square feet) of typical residential lane with bike lane and/or sidewalk per American to provide 100% of our energy needs.
Going back to Scott Brusaw’s numbers while pitching Solar Roadways, and assuming that Scott’s far, FAR more rugged panels generate similar power production, we have around 31,250 square miles of paved surfaces such as roads, bike paths, parking lots, etc. At 360 square feet per average American, that much road converted into solar roads can support 2.4 billion people, eight times our current population. Add in green construction and LED bulbs, we can up that to over 3 billion.
But Scott’s solar panels are far more rugged, designed for 100,000 pound traffic doing 70 MPH, and with many additional capabilities built in, such as melting off snow and instantly “painting” themselves with warnings and changing traffic patterns. So let’s “handicap” him a full 50% to account for a possible reduction of sunlight reaching the panels through the glass plus the power needs of melting ice and illuminating lanes. Let’s also assume Americans refuse to buy smart houses and bulbs.
We’re still, at worst, supporting four times our current population using existing surfaces on green energy produced using nothing but our roads and parking lots. The technology to do this is real, it is in place, and 120,000 bicycles have ridden over it in the past six months.
All we need to do now is have the patience to wait just a few more years for the technology to move from “real” to “realistic”, and “Solar Freakin Roadways” can come to a neighborhood near you.
James Hinton is a lifelong learner and army veteran. The son of an engineer, he keeps a close eye on the solutions engineering is developing for future growth.uf