### Author Topic: EEVblog #938 - Tesla Solar Roofs - Are They Viable?  (Read 37609 times)

0 Members and 1 Guest are viewing this topic.

#### cavac

• Contributor
• Posts: 14
• Country:
• The Perl Geek
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #50 on: October 31, 2016, 07:15:34 pm »
Solar Freakin' Roofs!

Dave, maybe you could do a video on a DIY solar system with those slightly damaged but functional reject solar cells from Ebay. Something like a 12 Volt/5 Volt system thats not connected to the grid.

Not the "mounting in a frame" part, which there are lots of youtube videos. But the wiring stuff, the maths, how to select the correct wire gauge and things like that. For example, how to wire a single panel, but also how to correctly wire up multiple panels to a single charge controller? How does one calculate the values for the protection diode? That kind of video.

"I calculated the odds of this succeeding versus doing something incredibly stupid... then i went ahead anyway." (Crowe, MST2K)

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #51 on: October 31, 2016, 07:23:13 pm »
Several of us engineers at a production plant calculated that a solar panel connected to the grid would have to run 10 to 15 years before it comes close to offset the impact of energy and hazardous waste it took to build the module.

Just give us numbers.

The EROI of solar PV panels is generally shown to be around 5, but if you have better numbers, just give them to us.

Concerning hte recycling : let's assume panels will be recycled in 30 Years, on average.
The copper, aluminium is straightforward and easy to retrieve. The glass, silicium, interlink ( probably also mainly copper) will probably be wasted, which is not a big deal, silicium is cheap and very low relative weight, glass also. Interlink copper is a small portion of the total copper.
« Last Edit: October 31, 2016, 08:53:02 pm by f4eru »

The following users thanked this post: HackedFridgeMagnet

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #52 on: October 31, 2016, 08:08:09 pm »
Concerning the solar shingles, this will probably be a fad.
Conventional panels are just easier to manufacture, sturdier, easier to mount, more efficient, and cheaper.

Concerning efficiency, regarding the sole change in linking technology:

Warning : these are ballpark calculations.

let's assume they have a single cell that outputs 0.6V @ 5A in one of these shingles.
let's assume the resistance of the interconnection to the next cell is 10 mOhm, (a 25cm wire @60°C 1mm² is 4.8mohm, plus 5.2mohm for a connector). Cable loss : 0.01*5 = 50mV
Now you already have a loss of 8.3% of the generated electricity only in the shingle to shingle link.......

le's see on a small traditional glass panel : 24V @ 5A
The cells are very close together, there's only a few mm from cell to cell, the end of the string is looped back to the start of the panel.
The same 1mm² wire with 1m length @60°C -> 19.3mOhm
The same connector @5.2mohm
the interconnects drom cell to cell can be estimated at nearly zero (the loss of the cell to edge interconnect and the few mm from cell to cell are the same than in the shingle solution )
cable loss : 0.0245*5 = 0.1225V  --> 0.5% loss

Now that's much better !!

Now let's consider the ressource "copper" in this link :

40 shingles(24V) : 40*0.25m = 10m of copper wire@8.9g/m, 40 connector pairs @ 2g    total : 169g of copper
single 24V panel :  1*1m of copper wire, 1 connector @2g  total : 10.9g of copper

So you have roughly 15x the power loss in the link despite investing 15x more in the copper, just because you want to space the cells for aesthetic reasons.

« Last Edit: October 31, 2016, 08:44:01 pm by f4eru »

#### kevyk

• Contributor
• Posts: 21
• Country:
• Mac software by day. Electronics by night...
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #53 on: October 31, 2016, 09:45:20 pm »
Everyone is forgetting a most critical limitation to the engineering for ANY solar panel including the Tesla / Solar City ones. This issue alone makes almost all rooftop solar panels completely unviable once you do the actual calculations. And no one ever talks about this.

The issue is, for at least on one evening every year, the weight of Santa's sleigh would obviously crush any solar tiles placed upon the roof. This makes rooftop solar panels impractical.

Now, when Santa finally implements anti-grav, then we can talk about solar again, but until then don't waste your money on an obviously flawed technology.
Kevin

The following users thanked this post: lpickup

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #54 on: October 31, 2016, 10:07:22 pm »
The problem is, there are people also in nuclear power stations, so sometimes the roof collapses at nuke power stations when santa passes :
http://media.gettyimages.com/photos/snow-storm-in-isere-the-roof-of-in-warehouse-at-the-nuclear-plant-of-picture-id162568841?k=6&m=162568841&s=594x594&w=0&h=iWRnFUXLd9WwgoukcN4GTfR1DL2YIZ_rtI1ana_33Xo=
« Last Edit: October 31, 2016, 10:35:17 pm by f4eru »

#### blueskull

• Supporter
• Posts: 12318
• Country:
• Power Electronics Guy
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #55 on: October 31, 2016, 10:11:18 pm »

The following users thanked this post: rs20

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #56 on: October 31, 2016, 10:37:33 pm »
Strange! BBcode strips the final "=" sign in the URL. Some bug in the parser probably..

Here's the picture :

#### rrinker

• Super Contributor
• Posts: 1885
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #57 on: October 31, 2016, 11:12:22 pm »
Of course.... if they actually also provided a superior, stronger, and longer lasting ROOFING material than traditional materials that could offset some of the costs of using them even on shaded parts of the roof compared to traditional materials.

Prediction, Coming in 2017

- Solar freaking FLOOR TILES!  Tile your entire house in solar, great for the bathroom/shower too!
- Solar freaking DRIVEWAYS!
- Solar freaking POOLS! Put solar panels at the bottom of your pool, after all it has a built in lens effect to magnify the solar radiation!  Hmm that might not be a terrible idea on first thought. I should patent that.

That's it, when I repaint my pool, I'm painting it black instead of blue.

#### boffin

• Supporter
• Posts: 865
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #58 on: November 01, 2016, 02:55:14 am »
Everyone is forgetting a most critical limitation to the engineering for ANY solar panel including the Tesla / Solar City ones. This issue alone makes almost all rooftop solar panels completely unviable once you do the actual calculations. And no one ever talks about this.

The issue is, for at least on one evening every year, the weight of Santa's sleigh would obviously crush any solar tiles placed upon the roof. This makes rooftop solar panels impractical.

Now, when Santa finally implements anti-grav, then we can talk about solar again, but until then don't waste your money on an obviously flawed technology.

OMG and that's today  OCT(31) = DEC(25) !

The following users thanked this post: vinicius.jlantunes

#### CatalinaWOW

• Super Contributor
• Posts: 3242
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #59 on: November 01, 2016, 03:40:02 am »
Almost all of the replies here give comments on the engineering viability of these panels.  They are mostly correct, and largely irrelevant.

If you look at US homes (and I suspect homes in much of the developed world) engineering evaluations are very far down the list of what makes them sell.  Just as an example there are few engineering reasons to differentiate between granite counter tops and tile counter tops.  But the vastly more expensive granite counter tops are greatly desired and widely sold here.  Since most US owners actually don't own their homes for more than a decade, even the lowly melamine coated counter top competes well on a technical basis.

So the appeal of these solar tiles will be for style, green points, feel good reasons.  Not anything related to efficiency, payback time, or even real impact on global warming.  They will have to be fairly reliable and repairable, but that is about all from the engineering side.  And as many have already pointed out, this baseline design may not meet that need, but I wouldn't bet against the product that actually reaches the market.

#### Bud

• Super Contributor
• Posts: 3468
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #60 on: November 01, 2016, 04:29:21 am »
I think after all there may be a problem with installers workforce. This looks delicate technology, and seeing those Chinese roofing crews in my neighborhood coming a dozen people on the roof and doing boom boom boom shooting their nail guns, finishing the roof in no time (with their usual quality issues of course), I cant possibly picture how they can repeat that with solar shingles. Job quality may become an issue, installation may require qualification, maybe even licensing and may be expensive and take longer, this alone will drive average house owners away.

#### nuclearcat

• Supporter
• Posts: 82
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #61 on: November 01, 2016, 04:34:38 am »
Probably as Powerwall, they void warranty, as soon as unit are not installed/maintained by certified installer. (at least according TESLA POWERWALL LIMITED WARRANTY (AUSTRALIA AND NEW ZEALAND), Jun 21 2016)
I guess same will be for solar roof, it will be pricey (but because of that highly profitable for installer), and logically - well done.

#### Brumby

• Supporter
• Posts: 9229
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #62 on: November 01, 2016, 05:16:05 am »
OMG and that's today  OCT(31) = DEC(25) !

How long have you been waiting to roll that one out?

#### dansan

• Contributor
• Posts: 11
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #63 on: November 01, 2016, 07:30:24 am »
I didn't see Elon Musk taking any questions from the audience after his solar roofs announcement.  If so, that's probably a good thing, considering the cringeworthy audience questions he got after his recent mars announcement.

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #64 on: November 01, 2016, 08:07:47 am »
So the appeal of these solar tiles will be for style, green points, feel good reasons.  Not anything related to efficiency, payback time, or even real impact on global warming.
A kitchen typically is a style driven buy which is sold by a guy getting a big comission.
A roof typically is a cost and performance driven item which is proposed by your architect, or builder, which is budget constrained, and tries to get the best performance out of cheaper materials.
Very very very very different things.

The market of styly overpriced solar tiles is a very small one compared to the market of efficient cheap panel solar.
That'S where the marketing of Tesla will fail.
and where others failed : http://client.dow.com/dowpowerhouse

#### jonovid

• Frequent Contributor
• Posts: 777
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #65 on: November 01, 2016, 08:26:37 am »
Quote
Quote
Quote from: CatalinaWOW on Today at 02:40:02 PM
So the appeal of these solar tiles will be for style, green points, feel good reasons.  Not anything related to efficiency, payback time, or even real impact on global warming.
A kitchen typically is a style driven buy which is sold by a guy getting a big comission.
A roof typically is a cost and performance driven item which is proposed by your architect, or builder, which is budget constrained, and tries to get the best performance out of cheaper materials.
Very very very very different things.
Tesla Solar Tiles, the solar you have, when you want everyone to think you do Not have solar. gosh that's not hard to do.
Hobby of evil genius      basic knowledge of electronics

#### nuclearcat

• Supporter
• Posts: 82
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #66 on: November 01, 2016, 08:34:40 am »
Just because there is plenty of fanboys, he might succeed. They already bought car (but it is really good), powerwall(v1 was not so good, feasibility questionable, but still good sales as they say), why not "solar roof" as well?
Only difference with Apple - world was waiting for proper handheld device, phones were moving to this direction, and Apple iphone has significant innovation in UI.
But, IMHO, solar power not in favor right now, due low oil prices, and he is not much different from solar shingles.
I hope someone do real innovation, rather than just repacking existing technologies in shiny envelope, for example improve nickel-iron batteries with their insane lifetime (30-50 years and almost unlimited cycles), which also much less hazardous to environment and dont need lithium (limited supply and lithium mines are really terrible for environment).

#### dekra54

• Supporter
• Posts: 27
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #67 on: November 01, 2016, 09:55:02 am »
As someone who install Photovoltaik Systems nearly every day i think the most important thing is the final cost per Watt and cost per kW installed. Right now in germany it is between 39 to 60 Cents per watt. And about 800 to 1200 Euro for 1 kW installed depending on the type of roof.
But aside from the financial aspect i'm interested what technical solutions they come up with. Especially with the interconnects because apart from a broken inverter a defective connector is the most common reason why i have to climb on to a roof. And i dont Like  having hundreds or maybe thousands of  connections that are connected on a construction side where are a amount of reasons why such a simple thing can go wrong. Would also be interesting how they tie it to ground

Gesendet von meinem SM-G900F mit Tapatalk

#### dekra54

• Supporter
• Posts: 27
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #68 on: November 01, 2016, 10:38:17 am »
As someone who install Photovoltaik Systems nearly every day i think the most important thing is the final cost per Watt and cost per kW installed. .
I'm prepared to believe that is true of Germans, but in Australia it is more likely to be about the feed-in tarrif per KWh you receive for energy supplied to the grid or the rebate on the installation you get from the government.

Sure one depends from the other. At the moment the fixed feed in tarif for self energy use systems is 8.5 to 12.5ct (depending on size) per kWh and for complete feed insystems its much lower. About ten years ago it was abou 50ct ! but the price for the system installed was obviously much higher.
And in germany there is actually no direct public sponsorship for installation, just the fixed feed in tarif for 20 years (at least that i'm aware of).

#### b_force

• Super Contributor
• Posts: 1180
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #69 on: November 01, 2016, 11:15:04 am »
Maybe the following is a bit of a party pooper.
But every time I see something about 'reliable energy solutions' I can't help thinking about one thing.
We are simple with WAY to many people on earth.

Even if magically we nail all the problems, reduce the total power consumption AND garbage waste with 50% (which is heaps!)

Currently the world population is growing with a whopping 83 million each year.
If we don't don't anything against it, this means that in 2050 the world population will be around 9.7 billion pooing, farting, wasting, drinking, eating super apes.
Or 11.2 billion in 2100.
The population at this moment is 7.4 billion people.

In other words, we need to cut at least 30% of all waste (in any form) to be even as we are today in 2050.
That also means, we haven't gained anything extra, to 'safe' our asses (not the world, the world will be fine eventually)
There are some ideas and predictions that the growth will go down eventually and even get lower.

Anyway, realistically I don't see how on earth (no pun) we are going to fix 50% of the total waste.
Another thing I don't get is, why the focus is only on this subject, and not the extremely high growth?
I guess because from an ethical point of view it's a difficult subject.

Does this mean all of this is b*llsh*t?
No! As many great scientists already pointed out, there is nothing wrong with making things better, more efficient, more reliable.
On top of that it creates new exciting jobs.

It's only not going to help us in the end......

"If you can't explain it simply (or at all), you don't understand it well enough." A. Einstein

http://www.oneworldconcepts.com/ | http://www.soundprojects.com

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #70 on: November 01, 2016, 11:38:20 am »
Tesla Solar Tiles, the solar you have, when you want everyone to think you do Not have solar. gosh that's not hard to do.
hmm. So, if i understood you correctly, Tesla tiles are about bragging about a thing that is nearly invisible ?
That's kind of a very very niche market to me.

#### f4eru

• Frequent Contributor
• Posts: 550
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #71 on: November 01, 2016, 02:04:03 pm »
In other words, we need to cut at least 30% of all waste (in any form) to be even as we are today in 2050.
Yes, completely true. The world is overpopulated. Ressources are not lasting. We need to reduce drastically the population, that is the "easiest" measure.

#### CatalinaWOW

• Super Contributor
• Posts: 3242
• Country:
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #72 on: November 01, 2016, 07:01:38 pm »
Lets be clear.  Solar roof tiles are nearly invisible.  Unless you are a car nut, Tesla roadsters are also nearly invisible.  I can't tell you how many times one of my sons has said "There goes a Tesla" and I look around without spotting it.  They are smallish, rounded vehicles not greatly different than dozens of others on the road.  I need to see the Tesla logo to know what the car is.  So bragging rights aren't firmly tied to a flamboyantly obvious product.

The same thing applies in a variety of other fields.  Have you ever tried bragging about your new piece of test gear to your significant other or to friends who do not share your avocation?

So I am going to pile on with others and say that the primary market barrier for these is the interconnect problem.  If these have magic in this area it isn't obvious.

Those arguing that efficiency or cost is the primary factor are totally ignoring the fact that the best engineering solution to those problems is to make the house smaller.  But except for certain fad markets (the tiny house movement, for example) that direction has met little success in most of the developed world.  None at all in the US.

#### Don Hills

• Regular Contributor
• Posts: 159
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #73 on: November 01, 2016, 11:38:02 pm »
Yes, completely true. The world is overpopulated. Ressources are not lasting. We need to reduce drastically the population, that is the "easiest" measure.

Which method do you have in mind to achieve this? Plague? War?

#### retrolefty

• Super Contributor
• Posts: 1604
• Country:
• measurement changes behavior
##### Re: EEVblog #938 - Tesla Solar Roofs - Are They Viable?
« Reply #74 on: November 01, 2016, 11:50:23 pm »
Yes, completely true. The world is overpopulated. Ressources are not lasting. We need to reduce drastically the population, that is the "easiest" measure.

Which method do you have in mind to achieve this? Plague? War?

Well we could always try the "tax what you want less off and remove tax from what you want more of".
I recall from my service days that married Airmen were allowed extra income allotment for each child up to five. Not many had more then 5 but most had more then 2.

Smf