The main substrate of our roads hasn’t changed much in the past 50 years. Most of our roads these days are asphalt concrete with some being plain old concrete with a coarse aggregate in them. For what we use them for this isn’t really an issue as the most modern cars can still perform just as well on all kinds of roads so the impetus to improve them is low. There have been numerous ideas put forth to take advantage of the huge swaths of road we’ve laid down over the years, many seeking to use the heat they absorb to do something useful. One idea though would be a radical departure from the way we currently construct roads and it could prove to be a great source of renewable energy.
Solar (Freakin’) Roadways are solar tiles that can be laid down in place of regular road. Their surface is tempered glass that’s durable enough for a tractor to trundle over it and provides the same amount of grip that a traditional asphalt surface does. Underneath that surface is a bunch of solar panels that will generate electricity during the day. The hexagonal panels also include an array of LEDs which can then be used to generate lane markers, traffic signs or even alert drivers to hazards that have been detected up the road. Both the concept art and the current prototypes they have developed look extremely cool and with their Indiegogo campaign already being fully funded it’s almost a sure bet that we’ll see roads paved with these in the future.
The first question that comes to everyone’s mind though is just how much will roads paved in this way cost, and how does that compare to traditional roads?
As it turns out finding solid numbers on the cost of road construction per kilometer is a little difficult as the numbers seem to differ wildly depending on who you ask. A study that took data from several countries states that the median cost is somewhere around $960,000/km (I assume that’s USD) whereas councils from Australia have prices ranging from $600,000/km to $1,159,000/km. Indeed depending on how complicated the road is the costs can escalate quickly with Melbourne’s Eastlink road costing somewhere on the order of $34,000,000 per kilometer laid down. In terms of feasibility for Solar Roadways I’d say that they could be competitive with traditional roads if they could get their costs to around $1,000,000/km at scale production something which, in my mind, seems achievable.
Unfortunately Solar Roadways isn’t forthcoming with costs as of yet mostly due to them being in the prototype stage. Taking a look over the various components they list though I believe the majority of the construction cost will come from the channels beneath the panels as bulk prices for things like solar panels, tempered glass and PCBs are quite low. Digging and concreting the channels required to carry the power infrastructure could easily end up costing as much as a traditional road does so potentially we’re looking at a slightly higher cost per km than our current roads. Of course I could be horribly wrong about this since I’m no civil engineer.
The cost would be somewhat offset by the power that the solar roads would generate although the payback period is likely to be quite long. Their current prototypes are 36 watt panels which they claim will go up to 52 watt for the final production module. I can’t find any measurements for their panels so I’ve eyeballed that they’re roughly 30cm per side giving them a size of about 0.2 square meters. This means that a square meter of these things could generate roughly 250 watts at peak efficiency. The output will vary considerably throughout the year but say you get 7 hours per day at 50% max output you’re looking at about 875 watts generated per square meter. Your average road is about 3 meters wide giving us 3000 square meters of generation area generating about 2,600kwh per day. The current feed in tariffs in Australia would have 1km of Solar Roadways road making about $1000 / day giving a pay off time of around 3 years. My numbers are likely horribly skewed to be larger than they’d be realistically though (there are many more factors that come into play) but even slashing the efficiency down to 10% still gives you a pay back time of 15 years, longer than the current expected life of the panels.
As an armchair observer then it does seem like Solar Roadways’ idea is feasible and could end up being a net revenue generator for those who choose to adopt it. All of my numbers are based on my speculation though so there are numerous things that could put the kibosh on it but it’s at least taking to the real world implementation stage to see how things pan out. Indeed should this work as advertised then the future of transportation could be radically different, maybe enough to curb our impact on the global ecosystem. I’m looking forward to see more from Solar Roadways as a future with them looks to be incredibly exciting.