EEVblog #743 – Solar Roadways Test Results

[vlad777]

Three layer solar cell has maximum theoretical efficiency of 45% and infinite layer has 80% .
So instead of crying about this, why don't we make use of this fact.
I am proposing a greenhouse made out of one-layer solar cell that is transparent to blue light that plants like. (and far IR)
And if earth needs for energy are going to come from solar,
 than I predict that all of arable land will be covered in these greenhouse-power plants.

[Jeroen3]

That doesn't work because most greenhouses have gas engine generators for heat, co2 and power production already. Why would they want expensive solar panels?

[vlad777]

To ditch the gas engine and also there may be some surplus energy.

Edit, gasoline is going to run out. Also you have to pay for it constantly.



I am including this picture to illustrate that there is enough near IR to convert to far IR (heat).

[max_torque]

We need 1 year to establish things.

No, no we don't!

  By comparing the solar cycleway to the normal roof top solar instalations, that were within a few Km, we already have a direct comparison because the same amount of sun light fell on both systems during the test period.

It doesn't matter for how long we test it, the comparison is valid in terms of $ per kWHr , which is ALL that matters.


(hint, i have two packets of crisps to sell.  Packet A is 50grams and costs $0.20, Packet B is 25grams and costs $3.  Which one would you like to buy??  ;-)

[Monkeh]

Packet B please, I'm sure they're far superior.

[eneuro]

The expected power is not 25Wh/m2 on that period but between 15 and 20. So 24.5 is significantly more.

It is  while make easy calculation:
3000kWh per 6 months, great 3MWh wow 
BUT: 6months= 6*30.5 days= 183 days
so we get: 3000 kWh / 183 ~16 kWh/day
Is it 122 m2 instalation, so we get: 0.131kWh/m2/day 
Now lets assume those bloody roads worked for those "great" results 8 hour a day, than we get: 0.016kWh/m2/hour = 16 Wh/m2/hour  
I wish I made mistake, but probably not
Update: I've forgot hour in kW in a few places, but doesn't change to much.. corrected now.

Dave have on his 3000kWh per 6 months, but ~16 Wh/m2/hour it is nothing and people riding bicycle will easy save such amount of energy, by... driving 1km/h slower or slower on this path 

BTW: Forgot to mention that even using not cheap electricity cost in my country it looks like those "solar roads" earned ~0.80 $ /month/m2 
Is it a joke? 


In comparision another data:
This cheap savonius wind turbine output annual 1752 kWh (per 12 months I guess) using ONLY 9m2 wind swept area,
so we have 16kWh/m2/month  and 146kWh/month ~5kWh/day assuming small investment not so bad 
http://www.uvm.edu/extension/cropsoil/wp-content/uploads/savonius_windpower_report.pdf

They claim 2 years payback period invested ~1000$ if we consider only materials used for steel savonious wind turbine 

[tszaboo]

On a sidenote:
The pilot is €3 million euro (50% government funded), and they expect a production road (not this one) to pay back in 15 years.
In about 5 years they hope to start producing to pave more roads.

I hope they dont. This solar roadways payback questions are like asking people how much time does it for a church to pay back. They dont care they do it because they believe in it.
It is like in the 21 century we do engineering and science based on what we believe in, screw logic. Solar roadways, mars one, perpetuum mobiles, and indiegogo revolutionary gadgets.

BTW, seeing 3 Daves waving hands at the same time, in black tee 

[Someone]

Edit: that is if you are going to post before giving Dave a chance to start the topic where he will add his initial comment like:

The 6 month test results for the Solar Roadways Solaroad.nl solar bike path project in the Netherlands are in. Dave compared the results to three local rooftop solar system and debunks the recent media reports that the project produces more power than was expected and that the solar roadway are now viable as a result.
And which country is doing Solar Roadways right? - South Korea!

There is roadside solar in Melbourne, pretending to use some space on top of a reclaimed rubbish dump site.
https://www.google.com.au/maps/@-37.768334,144.809395,3a,75y,128.35h,89.59t/data=!3m4!1e1!3m2!1sYgz61tw1WlDq0VVXVQjnUA!2e0!6m1!1e1

[EEVblog]

Also, the website states the panels are 2.5 x 3.5 meter. Does that change the numbers much?

They don't look 2.5m wide to me.



They might have changed it from the initial prototype from the ones used in the actual pathway. I forget how I came to the 1.75m figure in the previous video.
Bigger than I expected would mean they aren't as good as I calculated.

EDIT: David2 and I just did a test with a measuring tape, and 2.5m seems too wide. Also, the ratio of the panel dimensions doesn't quite fit the 1:1.4 of 2.5m x 3.5m
In any case, bigger makes the calcs for the output worse.

[EEVblog]

No and again this is where you are terribly wrong. 50% is not "ballpark" it's completely wrong. In winter sunlight time is much shorter than in summer in NL and the Sun is not high at all.

Fine, I was wrong to make the 50% ballpark assumption, happy?

You took figures from neighbors. Why didn't you use these figures to check that ?
I did it and found 30%.

Their own figures indicate a ratio of 2.8 based on my area measurements, not 2.0 as I used. That's about 35%.

So if they did 25 and that's 25%-30% of the year production, then one year will actually be 80-100kWh/m2
That's much better than the 50-70kWh/m2 they expected.

Their own estimates are and I quote

"If we translate this to an annual yield, we expect more than the  70 kWh per square meter per year, which we predicted as an upper limit in the laboratory stage."

If it was 100kWh they would be damn well crowing about it! So most likely it's just a smidgen more than 70kWh.

But again, I mentioned this in the video, even if it was double what they expected it's still useless from a cost perspective.

[EEVblog]

My own bicycle is 1.75 m and attempting to calculate the track width against the rightmost fully visible bicycle (with blue coat on rack) assuming it too is 1.75m leads me to approx 2m. If it is 2.5m wide then that would be a freakish long bicycle.

Yep, about 2m popped out for us too. 2.5m wide seems way too wide.
If it is 2m then 1.75m isn't too bad because the cell isn't the full width.

[BobC]

It's customary to embed the video on the first post:

Edit: that is if you are going to post before giving Dave a chance to start the topic where he will add his initial comment like:

But with the appropriate links he decides to place in the topic as well.

Hey, I'm just glad I remembered to use the correct subject line.  It did get folks like you here to do the next step.

Thanks!

[firewalker]

Dave, did you calculate that the 100% of the panel surface produces power? What is the effective area? 70%? If so, the kwh/m2 could be slightly better, is the area of the roof top panels show on the data is the effective area.

Alexander.

[EEVblog]

Dave, did you calculate that the 100% of the panel surface produces power? What is the effective area? 70%? If so, the kwh/m2 could be slightly better, is the area of the roof top panels show on the data is the effective area.

I mentioned in the video IIRC that I used 100% area for both the solar pathway and the solar panels, so any unused area on both should be similar and hence comparing apples with apples.

[Fungus]

Dave, did you calculate that the 100% of the panel surface produces power? What is the effective area? 70%? If so, the kwh/m2 could be slightly better, is the area of the roof top panels show on the data is the effective area.

Which part of "ballpark figures" is confusing?

Even if we add another 10% it's still not enough to take it off the list of "top-10-stupidest-ideas-ever".

To take it off that list you'll need a 1000% improvement in output, not 10%. Even so it'll still be on the "top-100-stupidest-ideas-ever" list.  (Lorries driving on glass for 20 years without any damage at all? Really?)

[quarros]

I forget how I came to the 1.75m figure in the previous video.

There was one forum member who went there for check (frvisser) and he posted about it in the forum: https://www.eevblog.com/forum/blog/eevblog-681-more-solar-roadways-bullshit!/msg546105/#msg546105
One tile is 170X270 cm.

[EEVblog]

There was one forum member who went there for check (frvisser) and he posted about it in the forum: https://www.eevblog.com/forum/blog/eevblog-681-more-solar-roadways-bullshit!/msg546105/#msg546105
One tile is 170X270 cm.

Ah, now I remember that, thanks. Still don't remember how I calculated it initially, but it was close to spot on.

[JoeO]

Maybe we need videos on "Worst Case Analysis" and one on "Best Case Analysis" that is separate from the solar roadways project.

It is obvious that some people do not understand these concepts.

[mullecy]

We need 1 year to establish things.

No, no we don't!

  By comparing the solar cycleway to the normal roof top solar instalations, that were within a few Km, we already have a direct comparison because the same amount of sun light fell on both systems during the test period.

It doesn't matter for how long we test it, the comparison is valid in terms of $ per kWHr , which is ALL that matters.


(hint, i have two packets of crisps to sell.  Packet A is 50grams and costs $0.20, Packet B is 25grams and costs $3.  Which one would you like to buy??  ;-)

Read my answer... This is what I did. But I guess reading more that one line and quoting it out context is all you can do.

[JoeO]

50 years ago my father gave me a Knight Kit solar powered radio.  I was so impressed that I investigated solar power.  50 years ago, financially practical solar power was just around the corner.
50 years later, today, it is still just around the corner. 

[Monkeh]

Dave, your obsession with comparing this to roof top solar made you completely miss the point of the project.

Local governments own a lot of property, including many paths. They spend quite a bit of money building and maintaining them. Solar PV is getting cheaper. They can only install so much rooftop solar, and the way budgets work they often can't just take money from the paving budget and spend it on roofs. Having the option to install less efficient but still useful solar paving will allow them to install PV capacity that they would otherwise not be able to.

I think you completely missed the point.

Why install amazingly expensive, less effective solar roads when they could put solar panels up on posts next to the road for less money and more output?

[Fungus]

Local governments own a lot of paths. They spend quite a bit of money building and maintaining them.

They're going to spend an awful lot more building these.

They're also going to spend an awful lot more maintaining them - especially when kids find they can smash them for fun.

Bottom line: There's no way a bit of 'free' electricity can ever make up for any part of this steaming turd of an idea. If you want to help the world then invest those billions of dollars you'd spend on this  in fusion research instead.

[Monkeh]

They're going to spend an awful lot more building these.

That's the thing, not really. I work in the water industry, and so I know a bit about the costs to do works in public areas. Most of the cost is not the materials, it's labour, ensuring that the work is done safely, managing traffic and diversions etc. Because of that digging a 1m square hole can easily cost €5-10k. The cost of the replacement 1m square paving surface is a fraction of that.

But you don't need to dig a 1m² hole, or replace the paving surface.

[Monkeh]

But you don't need to dig a 1m² hole, or replace the paving surface.

What... are you on about? It's an example of the costs involved of doing works in a public area. The costs of actually digging the hole and the materials needed to re-cover it are negligible, that's the point. It's the same when you want to re-surface or build a new path somewhere. Most of the cost is not the materials.

I'm on about not needing to replace pavements with stupid solar pavements.

Okay, sure, a lot of the expense is indeed in the work, not the material, but why spend money on crap solar in the ground when you can do it properly for less?

[Jeroen3]

This was a pilot project. An experiment. Government funded.
No company nor individual will ever pay for non-profitable solar roads from non-pr budget. Or at least, healthy companies shouldn't.