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Solar roadways: Better for show than practicality?
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Lauren Swan
Wednesday, November 19, 2014
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Solar roadways: Better for show than practicality? The Netherlands has installed a bike path with solar panels. (Photo: SolaRoad)
With the new solar road opening for cyclists in the Netherlands, a debate has been reignited that was initially begun by the Dutch's installation of solar panels into their roads. On the one hand, the government is trying to practice energy conservation and go "more green," while on the other hand, there are plenty of engineers who believe this is not a feasible option due to the mathematics supporting the installations.
So which is correct? Are solar road ways a waste of time and money, or should the engineers back off and see how much energy the panels can actually produce? Surprisingly, it seems like the answer is the former.
It seems like many people were honestly ready for solar panels to be the next world-changing, energy-conserving practice, which would be adopted throughout the EU and the U.S. In a way, it is a great thing that so many people want it. Energy conservation is important and ties into cutting greenhouse gases which are responsible, in part, for climate change.
The unfortunate side to this theory is that it means people are going to sink their teeth into this idea and not let it go. Solar roadways just sound cool — who wouldn't want to ride a bike on one? I mean, remember this video from an American crowdfunding campaign earlier this year?

But while they may be neat, they are not practical, and it all comes down to the science.
To start with, there are several aspects to consider even before we start to break down the physics of the matter. For instance, the solar panels are going to be laid flat for the road. There will be a slight tilt, but that is to ensure water doesn't pool on the surface. The government says that the tilt will also help to keep dirt and grime from piling up on the solar panels and affecting their efficiency, however, for practicality’s sake, the tilt is likely not going to be that pronounced.
They are expecting 2,000 people per day to use it. If the path was noticeably tilted, it wouldn't be comfortable to bike on. This, in turn, means that there will be dirt buildup, and even if people come by to clean off the road way every night, then that means more money invested in maintenance per year.
Another issue is the amount of energy that will actually be generated by the panels. Solar panels work best when they are at an angle — allowing them to take in more sunlight. A raised solar panel on a roof at an angle generates five times more energy than a solar panel laid down flat, such as the solar roadway in the Netherlands.
But the angle — or lack thereof — isn't the only concern. The glass being used for the roadway is also a no-glint, thicker piece (10 mm) of glass with a pattern etched into the top. Not only is this type of glass more expensive, but it also traps heat, which can compromise the amount of sunlight a solar panel can take in.
This is all assuming there are never cloudy days in the Netherlands.
Practicality aside, when you work out the physics for this solar power bike path, the numbers don't match either. The government's hope is that 100 meters (m) of roadway will power three houses, and that the project will essentially pay for itself within 15 years.
The typical house uses 3,200 kilowatt hours (kWh) per year. This means that three houses will need 26.4 kWh per day. A flat solar panel in Amsterdam, meanwhile, has a 30 percent loss, which generates about 3 kWh/m˛ per day.
This sounds like a decent figure, but you have to keep in mind that solar cells are not that efficient — one of the best types of solar panels that exists can only keep 18.5 percent of that figure, significantly reducing the amount of energy generated. The total amount is roughly 388 Wh/m˛ per day — and keep in mind this is a best-case scenario.
Now, the Dutch government has put a lot of research into this project, as you would expect since it is costing 3 million euros. They have actually posted some numbers referring to what they expect will happen with the cycle path.
The bike path is expected to generate about 137 Wh/m˛ per day, which is pretty realistic; it's also backed up by their first test result. They got 100 Kwh for the week, but that has to be divided by the length of the solar panels, which is about 122 m˛, since the panels are slightly wider than a meter. Then, that number has to be divided by seven, since there are seven days in a week, leaving a result of 117 Wh/m˛ per day. This isn't too far off their estimate.
In the Netherlands, energy costs about 0.2 euros per kilowatt hour, so that needs to be multiplied by the government's figure of 50 kWh/m˛ per year, and the result is 10 euros per year per m˛, which is low. Multiply that figure by the 15 years they expect for the payback, and it comes out to 150 euros for 15 years per m˛.
However, the government also provided expected costs for the solar biking road, which should let people know whether or not this project is viable. The installed system cost is roughly 230 euros per panel, which is what it costs to install a normal solar roof panel, which includes the panel, wiring and the installation. It is highly unlikely it will cost less to install the cycle path, given that it will be more difficult and time consuming. So that has already passed the generated revenue for the 15 years.
There is also road rehabilitation to consider, the cost of the protective glass and any special maintenance the cycle path may need. So clearly the payback period of 15 years is too optimistic. A more realistic, but still generous figure for total cost including all of the previously mentioned necessities, would be more like 250 euros per panel. That isn't including the road services and maintenance costs.
There are those who feel like shutting down the idea of solar roadways and cycle paths is detrimental to furthering the solar power agenda. After all, if people hadn't continued changing the automobile, we would never be where we are today. In that aspect they have a point, but only in terms of automobiles.
Creating a plethora of solar cycle paths will not somehow change the physical properties behind them. Lying flat on the ground, with thick, protective glass, there is only so much energy that can be caught from the sun. The point is that the engineers creating the panels will need to go back to formula, and re-create panels that can catch more light to convert into energy, though it will still be difficult regardless because the panels will be at the worst possible angle.
Solar panels are a wonderful thing, and the more the world can use them to get its energy, the better. However, wishful thinking doesn't change the math behind the project. The idea of solar roads and solar cycle paths are just not fruitful ideas, and will actually ending up costing citizens more in the long run, rather than saving money.
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Spanish Manlove posted:

thanks rereg guy!

WWWWWWWWWWWWWWWWWW posted:

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freelop posted:

https://www.youtube.com/watch?v=H901KdXgHs4

quote:

Are solar road ways a waste of time and money, or should the engineers back off and see how much energy the panels can actually produce? Surprisingly, it seems like the answer is the former.

Spanish Manlove posted:

thanks rereg guy!