After the hubbub that Solar Freakin Roadways caused last year (ranging in tone from hopeful to critical) all seemed to have gone quiet on the potentially revolutionary road surface front. I don’t think anyone expected us to be laying these things down en-masse once the Indiegogo campaign finished but I’ve been surprise that I hadn’t heard more about them in the year that’s gone by. Whilst Solar Roadways might not have been announcing their progress from the rooftops there has been some definitive movement in this space, coming to us from a Dutch company called SolaRoads. Their test track, which was installed some 6 months ago, has proven to be wildly successful which gives a lot of credibility to an idea that some saw as just an elaborate marketing campaign.
The road was constructed alongside a bike path totalling about 70m in length. Over the last 6 months the road has generated some 3,000kWh, a considerable amount of energy given the less than ideal conditions that these panels have found themselves in. Translating this figure into an annual number gives them around 70kWh per square meter per year which might not sound like much, indeed it’s inline with my “worst case” scenario when I first blogged about this last year (putting the payback time at ~15 years or so), but that’s energy that a regular road doesn’t create to offset its own cost of installation.
Like Solar Roadways the SolaRoad’s design is essentially a thick layer of protective glass above the solar panels which are then backed by a layer of rubber and concrete. Instead of the hexagonal tile design they’ve instead gone for flat panels which would appear to be more congruent road design although I’ll be the first to admit I’m not an expert in this field. By all accounts their design has stood the test of time, at least with the light load of cycling (although they claim it could handle a fire truck). The next stage for them would be to do a full scale replica on a road that sees a decent amount of traffic as whilst a cycleway is a good indication of how it will perform there’s nothing better than throwing the challenges of daily traffic volumes at it.
Unfortunately SolaRoad isn’t yet ready to release a potential price per kilometer installed however the entire program, including the research to design the coatings and the road itself, has come up to some $3.7 million euros. Considering that my original estimates pegged a competitive cost at around $1 million per kilometer I’d say that the trial has been a pretty good investment (unless you’d really want 4km worth of road somewhere instead…). That will ultimately be what determines if something like this can become a feasible alternative to our current asphalt road surfaces as the idea won’t get any traction if it’s noticeably more expensive than its traditional counterpart.
It’s good to see progress like this as it shows that the idea has some merit and definitely warrants further investigation. Whilst the power generation numbers might not be revolutionary there’s something to be said for a road that pays itself off over time, especially when that comes in the form of renewable energy. With further advances in grid technology and energy storage these roadways, in conjunction with other renewables, could form the basis of a fossil fuel free future. There’s a long way to go between today and that idyllic future but projects like this ensure that we keep making progress towards it.
Last week I wrote a post about the Solar Roadways Indiegogo campaign that had been sweeping the media. In it I did a lot of back of the envelope math to come up with some figures that made them seem reasonable based on my assumptions which lead me to the conclusion that they looked feasible with the caveat that I was working with very little information. Still I did a decent amount of research into some of the various components to make sure I was in the same order of magnitude. You’d then think that the venerable Thunderf00t’s takedown video on this project would put me at odds with him but, for the most part, I agree with him although there were a couple of glaring oversights which I feel require some attention.
FIrst off let me start off with the stuff that I agree with. He’s completely correct in the assertion that the tile construction isn’t optimal for road usage and the issues that arise from it are non-trivial. The idea of using LEDs sounds great in principle but as he points out they’re nigh on invisible in broad daylight which would make the road appear unmarked, a worrying prospect.Transporting the energy generated by these panels will also be quite challenging as the current produced by your typical solar panel isn’t conducive to being put directly on the grid. The properties of the road also require further validation as whilst the demonstrations shown by Solar Roadways say they’re up to standard there’s little proof to back up these claims so far. Finally the idea of melting snow seemed plausible to me on first look but I had not run any numbers against that claim so I’d defer to Thunderf00t’s analysis on this one.
However his claims about the glass are off the mark in many cases. Firstly it’s completely possible to make clear glass from recycled colour glass, usually through the use of additives like erbium oxide or manganese oxide. I agree on his point that it’s unlikely that they have the facilities available to them to do this right now however it’s not out of the realm of possibility. Thunderf00t also makes the mistake of taking a single item price of a piece of tempered glass off eBay and then uses that to extrapolate to the astronomical cost for covering all of the roads in the USA with it. In fact tempered glass produced at volume is actually rather cheap, about $7.50 per square meter, when you check out some large scale manufacturers. This makes the cost look far more reasonable than the $20 trillion that was originally quoted.
The same thing can be said for the solar panels, PCBs, LEDs and microcontrollers that are underneath them. Solar panels can be had for the low low price of $0.53 per watt (a grand total of about $30 per panel) and RGB LEDs for about $0.08/each (could have 1000 in each panel for $80). Indeed the cost of the construction of the panels themselves are likely to not be that expensive, especially at volume, however the preparation for the surface and the conduit channel are likely to be more expensive than your traditional road. This is because you’d likely have to do the same amount of site prep work for both of them (you can’t just lay these tiles into dirt) and then the panels themselves would be an incidental cost on top.
Tempered glass is also a lot harder than your regular type of glass, something which Thunderf00t missed in his analysis. It’s true that regular glass has a Mohs hardness of around 5 but tempered glass can be up to 7 or higher, depending on the additives used. Traditional road surfaces have a very similar hardness to that of tempered glass meaning they’d stuffer no more wear than a traditional road surface would. Whether this would mean a degradation in optical quality, and therefore solar efficiency, over time is something I can’t really comment on but the argument of sand and other things wearing away the surface doesn’t really hold up.
All this being said though Thunderf00t hits on the big issues that Solar Roadways has to face in order for their idea to become a reality. Whilst I’m still erring on the side of it being possible I do admit that there are numerous gaps in our knowledge of the product, many of which could quickly lead to it being completely infeasible. Still there’s potential for this idea to work in many areas, like the vast highways throughout Australia, even if some of the more outlandish ideas like melting the snow on them might not work out. It will be interesting to see how Solar Roadways reacts to this as there are numerous questions which can’t go unanswered.
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.