Its impossible to pave a road with solar panels?
It's possible (although idiotic) to pave a road with solar panels. It might not be possible to do so without compromising the road's key requirements (durability, high friction in adverse weather conditions, etc.). It is impossible for this road to also power its own LED line markings, produce a return on investment, heat the road it constitutes and also become a super military surveillance drone comparable to NASA's description of the Curiosity rover.
The fact that it's financially impractical (which rooster was kind enough to remind us of), is just the cherry on top of the cake.
Why would it be impossible for all that at once? Ok, the last part is just silly but the rest of it is possible.
LEDs aren't exactly high powered lights.
The Return on Investment will be tough. Without the math on how much each panel will cost during production we can't even begin to calculate a ROI.
So let's take the 280 Watt Solar Panel from Home Dept. $400/panel. 39.1"x77"
Let's pave that over 1 mile of road, 2 lanes.
Lanes vary between 9-12 feet in rural US for local lanes. So that's what we'll do. Let's use 10ft (for ease of math)
But I'm not stupid so I'm converting everything to metric.
1 mile = 1609.34 meters
Each lane is 3.048 meters wide.
Each Panel is 0.99314 meters x 1.9558 meters.
So the total area needing to be covered is 6.096*1609.34 = 9,810.53664 m
2
Each panel has an area of 1.942383212 m
2So dividing
9,810.53664/1.942383212
Total Panels needed: 5,051
At $400/panel it'll cost $2,020,400. Assuming we buy the panels straight from Home Dept.
http://www.homedepot.com/p/Grape-Solar-280-Watt-Polcrystalline-Solar-Panel-GS-P-280-Fab1/202959966?N=5yc1vZbm31So how long would it take to get a return on investment?
Let's assume (impossibly) that no cars ever drove on it. This will give us a lower limit on the minimum time it would take for a ROI.
Let's take New York since I'm more familiar with the state.
Peak sun averages about 4 hours. But let's assume 2 because we have panels flat on the ground instead of at an angle.
5,051 at 280watts = 1,414,280 watts.
1,414,280 watts*2 hours /1000 = 2,828.56 KWH
At the current rate of .08/kwh the panels would generate $226.2848 worth of energy a day. (ignoring the LEDs)
So the flat cost of $2,020,400/mile and a return of $226/day, it would take roughly 24.5 years to break even.
But what if we use cheaper panels?
http://www.ebay.com/itm/like/181395099800?lpid=8250x250w panels.
Or $156/panel.
Dimensions are a little different.
0.9906x1.64084 = 1.625416104 m
26,036 Panels. At $156 it'll cost $941,616. Less than half of the other panels.
Total power generated per day: 3,018 KWH
or $241.44/day.
ROI: 10.6 years.
Wow that was a lot of typing. (weird that the cheaper, smaller panels produced more energy. But whatever.)
Anyway, to calculate the same cost of the materials for an asphalt road, let's use this document:
http://www.dot.ca.gov/hq/esc/oe/cost_index/historical_reports/PI_2012_qtr4.pdfSo $94.41/ton.
Asphalt concrete is about 2.243 grams per cubic centimeter.
(I'm probably going to screw something up with the math so please point out my mistakes)
Convert to meters.
0.000001 meters
3
.002243 kg.
Density = 2,243kg/m
3
Assuming 0.0889m thickness a 1 mile road would be
0.0889*1609.34 = 143.070326 m
3So Mass = 2243*143.070326= 320,906.741218 Kg
kg to ton conversion:
321 metric tons.
Cost: $30,305.61
Or 4 months worth of pure solar roadway energy.
TL:DRMaterial Cost of Solar Panels for 1 mile 2 lane highway: $941,616
Time for ROI: 10.6 Years.
Material Cost of Asphalt Concrete: $30,305.61
Time for ROI: ?? (the roads produce nothing so their investment is all about having happy citizens and businesses but probably within 6 months if not sooner)
There!
The Math for all to see!
Solar roads are incredibly expensive.
3 mile island cost $1.91 Billion (adjusted for inflation) to build.
It generates 6,645,000,000 KWh /year.
At .08/kwh = 531,600,000 it's ROI is roughly 2 years.
Heating the road is easy and they've shown it working. It takes more energy than the panels will produce in the winter, but it can be done.