The dynamics of down-voting on HN can be interesting. I have this --possibly flawed-- mental image of emotional impulse voting devoid of any effort to analyze what is being said.

For the benefit of those who didn't take the time to think before down-voting my prior comment I'll try to spell it out here.

A few facts:

- Good commercial cells deliver an efficiency in the 14% to 19% range.

- This efficiency assumes the cells are aimed at the sun

- Optimal winter angle for the Netherlands is approximately 76 degrees from horizontal

- Peak efficiency also assumes the cells are clean and have nothing obstructing or altering light from reaching it's surface at the optimal angle

- In all cases you can Google my claims and verify their veracity

Option #1:

- Cover the solar panels with glass
- Scuff-up the surface so people and bikes don't slip and slide all over the place
- As an alternative, apply a film to achieve the same effect
- Mount them flat on the ground
- Place trees around it
- Have people, bikes and dogs walk on it

Analysis:

- The cost of encasing panels in concrete and glass modules and installing them is monumental

- The optimal angle for Amsterdam is approximately 76 degrees. Panels mounted flat simply throw away a significant amount of available energy.

- Solar cells laid flat will produce between 20% and 30% less when compared to optimally aimed cells.

- Glass will create problems based on how light enters. You have reflection, diffraction and scattering as possibilities. A percentage of the energy will never reach the cells.

- A non-slip surface will scatter and absorb a significant amount of energy. Based on the images I've seen of these road modules I am going to guestimate that at best 70% of the light entering the road reaches the cells. I base this on years of working with a wide range of optical diffusers.

- Dirt and particles on the cells can have huge efficiency effects. From light scattering to simply blocking and absorption. I'll go ahead and guess that you can't keep a roadway clean 100% of the time, therefore, you probably pay a, say, 20% penalty on average for having dirt, leaves and dog shit on the road. This is entirely a seat-of-the-pants number. It could be 10% or 50%. It isn't going to be zero.

- Power generation is now utilization dependent. With more people on the road more light is blocked and less power is generated. I won't put a number to this. I will rather make a statement: If nobody uses the road, what's the point of building one in the first place or building one that is so much more expensive than simply pouring plain concrete?

- Depending on angle, trees, buildings and even tall vehicles on the road will cast shadows on the panels.

A very rough calculation then says that, at best, our solar roadway will operate at 40% of peak efficiency. If we factor in the constant need for cleaning this number could very well go down significantly. For example, do we have a crew of a few people using gas powered leaf blowers cleaning the roadway a few times a day?

Option #2: Build a light steel structure atop a conventional bike path. Angle the panels for optimal efficiency at that latitude. You might splurge and add active tracking.

Analysis:

- The cost of installation is significantly lower

- By mounting the panels at the optimal collection angle we ensure converting power as near to the efficiency peak for the panel in question

- Angled mounting also aids in reducing surface particulate contamination and makes cleaning potentially as simple as an automated water sprinkler system

- The entire system is far less costly and efficient

- The bike path gets "free" shade as a side effect

So, yeah, the entire idea is absolutely ridiculous if anyone bothers to do a little math. Someone has got to be lining their pockets or whoever is leading this project is simply in denial.

Go ahead and downvote, but, if you do, please show your calculations and how you arrived at the idea that this concept actually makes sense to deploy at scale. I'll bet you can't.