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Power Science

Tesla Unveils Residential 'Solar Roof' With Updated Battery Storage System (theverge.com) 231

Tesla founder and CEO Elon Musk today unveiled the "residential roof" -- pegged as a roofing replacement -- with solar energy gathering powers. Unlike other solar systems which must be mounted on top of a traditional roof, these new panels are actually integrated within glass roof tiles, replacing a home's roof, Musk said. And because they're made of glass, Musk says they will last "quasi indefinitely," even in harsh conditions where snow and ice make short work of traditional asphalt shingles. Musk said that 50 years of lifespan should be no problem, and they offer efficiency that is 98 percent as good as a traditional, ugly photovoltaic panel. From a report on The Verge: There are a number of different versions of solar panels: Textured Glass Tile, Slate Glass Tile, Tuscan Glass Tile, and Smooth Glass Tile. Tesla says its glass tiles are much more durable than conventional roof tile -- something that's important in areas with risk of hail.The products are a "joint collaboration" between SolarCity and Tesla, according to SolarCity CEO Lyndon Rive. Tesla is attempting to acquire SolarCity for $2.6 billion and shareholders of both companies will vote on the proposed acquisition in the middle of November. The Powerwall 2 can store 14 kWh of energy, with a 5 kW continuous power draw, and 7 kW peak. The battery is warranted for unlimited power cycles for up to 10 years. It can be floor or wall mounted, inside or outside. It can be used for load shifting or back-up power. Musk says there are three parts to the solar energy solution: generation (solar panels), storage (batteries), and transportation (electric cars). Musk's plan is to sell all three of those products through Tesla.
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Tesla Unveils Residential 'Solar Roof' With Updated Battery Storage System

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  • TENNIS BALL-SIZED HAIL EXPECTED. Take Cover Now (and not under a glass roof, you dingus).
    • by AK Marc ( 707885 ) on Saturday October 29, 2016 @01:10AM (#53173697)
      Had a friend buy a hail-damaged car. He'd heard about hail sales and was looking to buy at the time. We walked the lot after a hail storm. The damaged cars had lots of dents in the metal, but not a single broken glass. The Texas dealership said that was common. Glass designed to take it is quite strong. Even bulletproof.
      • Re: (Score:2, Interesting)

        by Anonymous Coward

        I purchased a hail damaged Accord in north Florida for $7K off the price and got a paintless dent repair guy to pull up the dents with a suction cup attached to a compressor for $500. Total win. You can't tell the car was damaged, at all.

        • by hawk ( 1151 )

          You can't tell *yet*.

          Every layer of the paint suffered at least some damage at every dent, and will be partly detached from the metal underneath.

          These will rust *far* sooner than undamaged cars.

          Then again, $7k is more than enough for a really good paint job . . .

          hawk

      • by thegarbz ( 1787294 ) on Saturday October 29, 2016 @04:40AM (#53174101)

        That is actually quite irrelevant. Glass is weak and depends on it's structure to make it strong. The reason cars don't often suffer hail damage is due to the angle of incidence of the hail hitting the windows. Most damage is on the roof, bonnet, and boot (trunk for the America sedan owners), where the hail lands almost perpendicularly and can impart all of it's force into the thing it hits. By comparison window hits often happen at a very low incidence angle so only a tiny portion of the force is transferred into the glass. This is also why in a hail storm the most commonly damaged window by far is the front window despite also being the strongest of all windows in a car.

        Strength comes from structure. The reason solar panels are strong is because they are supported underneath. Glass (especially tempered glass) performs very well under compression. The strength comes not only from the glass, but the substrate behind it and the metal backing of the panel. A typical solar panel is far more durable than a sheet of tempered glass alone.

        Anecdote: I lived in a city with some ferocious hailstorms. Not just big round balls of hail, but irregular and sharp shaped blocks too. All of my solar panels survived. All of my neighbours' survived. All of our cars were completely written off and has massive amounts of damaged glass too (and in my case the inside turned into a bit of a swimming pool).

        • by dbIII ( 701233 ) on Saturday October 29, 2016 @06:11AM (#53174259)
          Glass is very, very strong - which is why it is used in glass fibre reinforced plastic. It is however normally very brittle as in it can't absorb a lot of impact energy without cracking.
          If you add something to absorb the energy, such as a sandwich of plastic between layers of glass in a car's windscreen you end up with something that is tough enough to take some impacts without cracking.


          For a first year engineering materials practical I used to get students to load up horizontal glass rods with a lot of weight until they bowed a lot. You need a very smooth surface so that cracks won't start from tiny scratches, so that meant preparing with Hydrofluoric acid (don't try it at home!). That gave the students a bit of an insight into the difference between strength (maximum load) and toughness (energy which is proportional to the area under a curve of load versus extension).
        • by Gussington ( 4512999 ) on Saturday October 29, 2016 @06:55AM (#53174329)

          That is actually quite irrelevant. Glass is weak and depends on it's structure to make it strong.

          Is hail that big a problem for most people? I'm sure for some people it is, just like some people have to deal with tornadoes, and others have to deal with heat waves, and others flooding. But most people don't have to worry about them, and for them, this is great.

          BTW we get the odd hail storm here, in the lat 30 years we've had two big ones that were enough to break stuff, and even the it was only in some suburbs, not the entire city. So these rare cases would be covered by insurance. A small additional cost is still probably going to be cheaper than 30 years of paying electricity bills

          • by dcw3 ( 649211 )

            Anecdotally, I've been through two hailstorms that were bad enough for the insurance company to replace the roof on my house. I think my insurance company hates me...the last one cost them over $30k.

            • There's also all kinds of hail - I used to get caught outside in Florida afternoon thunderstorms waiting to be picked up after school - those were usually more slush-balls than stones, though some of them were hard enough to bounce off the asphalt.

          • by adolf ( 21054 )

            We get hail storms, tornadoes, heat waves, flooding, and blizzards here.

            After the last good wind storm it took over a year to get most of the asphalt shingled roofs all fixed. Glass roofs made out of photovoltaic panels will just make the problem worse.

            • Any plague of frogs or locusts?

              • by adolf ( 21054 )

                There were locusts at my mother's house a few years ago, in numbers rather short of a plague. They ate the swimming pool. They ate the vinyl siding. They ate the window screens.

                I wish I were making any of this up.

          • Is hail that big a problem for most people?

            For most people in a given area frequented by hailstorms maybe :-)

            It certainly is a consideration in the parts of Australia I used to live in. I wouldn't give a second thought now though, mind you I wouldn't give it a first through either since the sun never shines where I live now.

        • by JoeMerchant ( 803320 ) on Saturday October 29, 2016 @08:39AM (#53174573)

          It's also a matter of scale - the metal panels of cars are quite thin compared to their glass. And then there's the classic flexible vs brittle contrast - metal will flex and permanently deform, while glass will flex and rebound - until it flexes so far that it shatters.

          Hit a glass panel with a big (fast) enough hailstone and it will break - it's just a matter of making the glass strong enough to survive the typical hailstones encountered within a 50 or 100 or 500 year period (depending on how much you are willing to pay now to not have to replace your roof later.)

          The fun part of this is changing weather patterns, how accurately can we predict the size and speed of hailstones 50 years from now? Since Elon's shingles are a brand new concept with essentially no competition, if he's got any class at all he'll over-design them so that they are more robust than they need to be. 15-20 years after they gain significant adoption in the marketplace, competition will shave their structural integrity down and down, saving a few cents on production costs in order to be the low price leader in the marketplace and simultaneously creating a shingle replacement labor market which actually costs far more than stronger (thicker) glass shingles that last twice as long would.

          • metal will flex and permanently deform

            Now there's a statement that has a whole lot of dependent variables.

          • by torkus ( 1133985 )

            How long is the solar PV portion good for? PV degrades over time AFAIK so your design life is likely to be based on that.

            30 year PV? So design to withstand the 50-year storm.

            • by Charcharodon ( 611187 ) on Saturday October 29, 2016 @08:33PM (#53176917)
              So far they don't know how long solar panels will last. There are solar cells from the 50-60's still producing power.

              The biggest problem for failure over the long term will be the framing, the racks, and the wiring. The cells themselves, absent stray rocks, will probably produces a useable amounts of power for over a hundred years. We are talking about he crystal/glass setups, not the plastic variety solar cells. Currently quite a few of the manufactures under promise the output of their cells so that they will still produce the rated amount of power for at least 20 years for their warranties. They seem to loose 5-10% of their output every decade or so.

        • Having regular tile sized pieces of glass will be much tougher than windshield sized pieces due to the decreased bending forces and underlying support structures.

        • I was in a hail storm/tornado a few years back the tornado was an f4 and passed a little over a mile from my work. The baseball sized hail hit us though we had an open parking lot full of cars and I had to tackle a co-worker and hold her on the ground because she was determined to run outside and move her brand new mustang. Every car in the parking lot was totaled mine actually had upper parts of the frame that were bent and the roof was bent so far down that the metal split at the top where the front winds

        • by AK Marc ( 707885 )
          So the glass sunroof, offered no support from the sides or bottom, just the mounts on the edges, and is as perpendicular to the storm as the surfaces you mention, should have been damaged if glass was weak? But it wasn't. There were dents around the glass, but the glass was undamaged.
        • and yet, few sun/moon roofs or t-tops actually have glass broken from hail.
      • by AmiMoJo ( 196126 )

        It's a lot easier to make glass resilient because it can be laminated and pre-tensioned.

        • In the video there is a thick pillow/foam pad under each tile which greatly enhances impact resistance and yet won't be a part of any practical installation. They all failed including the tesla tile, though it looks like it might still provide some limited protection against water intrusion. The clay tile is a bit silly as you typically don't see many installations in heavy hail climates. Note that an asphalt tile, such as the majority of the United States is roofed with, would likely suffer little to no
      • by dcw3 ( 649211 )

        My old white '98 Grand Prix looked like a giant golf ball after a hail storm back around '99. The insurance company cut me a check for nearly $2k. In less than a year, all of the dents popped out on their own. You literally could not see a single dent.

      • by WindBourne ( 631190 ) on Saturday October 29, 2016 @10:22AM (#53174765) Journal
        Bingo. I live on Colorado front range where we got golf ball size hail regularly. Thus summer our exposed hail resistant shingles failed with golf balls. Otoh, the Solar city panels? Not a scratch. Obviously the original poster has not a clue of what he is speaking.
    • by tofu2go ( 727555 ) on Saturday October 29, 2016 @01:14AM (#53173715)

      Actually, it looks like Tesla has thought of that... apparently their "glass" tile is tougher than conventional tiles. See this CNET video for reference: https://youtu.be/uWcGRYT-aeE?t... [youtu.be] If a conventional roof can withstand it, then so can theirs.

      • If you're going to sell a premium product at a premium price, you'll have to do these kind of "toughness" demos to have any chance in the marketplace.

        Give it 20 years or so, when competing manufacturers enter the market they'll start cheaping out the panels until they last more or less just as long as "conventional" roofing.

        • by JaredOfEuropa ( 526365 ) on Saturday October 29, 2016 @09:11AM (#53174615) Journal
          Could be even less. Our typical roof tiles last 40 years (mine are now at 75 years, and it's definitely time to replace), but solar panel output drops to a level where you need to replace them after 20 or so years. Longevity of the tiles isn't the issue, it's the dropping power output and the high cost of replacing the roof ever 20 years versus the cost of replacing the roof every 40 and separate panels every 20.
          • Re: (Score:2, Informative)

            by Anonymous Coward

            > but solar panel output drops to a level where you need to replace them after 20 or so years.

            Citation? Solar panel output only drops about 0.5-7% a year. https://electrek.co/2016/07/04/solarcity-increase-useful-lifetime-of-solar-power-installations/

          • Re: (Score:3, Interesting)

            by Anonymous Coward

            Disclaimer: I work for a solar panel manufacturer.

            Our best prediction is that at least 99% of our panels will output at least 70% of their power after 40 years. Trying to get that out to 50 years now.

            Panel longevity and reduced output has come a long way.

      • Actually, it looks like Tesla has thought of that

        This is something the solar panel industry solved years ago.

      • The Tesla glass tile did have multiple cracks after the kettlebell dropped. I doubt it will produce electricty, or much of it after a crack.

        I wonder what the weight will be for roof support loads.

    • by Dutch Gun ( 899105 ) on Saturday October 29, 2016 @01:55AM (#53173791)

      Glass is tougher than most people think [youtube.com].

      • by AK Marc ( 707885 )
        Windows in the Pentagon survived better than the walls. As someone trying to snipe would likely use a window-shot to sight the target, the windows would survive most man-portable munitions, including small missiles. In "glass".
      • by dabadab ( 126782 )

        It is pretty heavy though.

    • By their very nature, solar panels are plates of laminated glass or plastic reinforced with wires running through them.

      I.e. It's reinforced the same way bulletproof glass is.
      Where conventional tiles shatter into pieces, these tiles merely crack and dent. [youtube.com]
      And the best part is, each solar plate being an array of parallelly connected cells - it will still function both as a roof tile and as a solar cell.
      Whereas a conventional tile would at that point be useful only as gravel substitute.

      Guy runs a company which

    • by Socguy ( 933973 )
      That would tear a traditional roof apart. Good thing there's insurance...
    • by Jeremi ( 14640 )

      I'm pretty sure that SolarCity's hardware engineers are aware of the existence of hail, and have designed their solar panels to be adequately robust to handle it.

      Whether Elon is aware of the issue or not is irrelevant, since (reports to the contrary notwithstanding) he does not personally oversee every detail of every product.

  • The Powerwall 2 can store 14 kWh of energy

    In other words, they've improved it from storing $1 worth of electricity to $1.40. But you still need to cycle it many thousands of times with FREE electricity before it breaks even.

    • by Okian Warrior ( 537106 ) on Saturday October 29, 2016 @01:43AM (#53173777) Homepage Journal

      The Powerwall 2 can store 14 kWh of energy

      In other words, they've improved it from storing $1 worth of electricity to $1.40. But you still need to cycle it many thousands of times with FREE electricity before it breaks even.

      A quick search [eia.gov] shows that the average household electricity usage is about 10K kWh per year (900-ish per month), ranging from 14K in Louisiana to 6K in Hawaii.

      Using your numbers, that would be roughly $1000/yr. The powerwall costs roughly $7000 installed with inverter and other extras, or you can lease it for 9 years for $5,000 which includes installation, a maintenance agreement, the electrical inverter and control systems.

      Tesla is offering a ten year warranty [slashdot.org] on the batteries, and there's some discussion about how a battery can last for 3650 cycles (mostly because the 14K powerwall is a 20K battery pack that's discharged much more shallowly than if it was an actual 14K battery, and other tricks).

      The total cost comes out to about 0.15/kWh.

      "Tentative Conclusion: The battery is right on the verge of being cost effective to buy across most of the US for day/night arbitrage. And it’s even more valuable if outages come at a high economic cost."

      • by Kjella ( 173770 )

        My math says 14 kWh * 365 cycles = 5110 kWh and $5000 / 9 years / 5110 kWh works out to $0.11/kWh. That however assumes it has a source that can fill it up every day and you use it completely every day. With solar that is unlikely as in the summer the main consumer is AC which correlates well with when the sun is up and you'll probably not use 14 kWh every evening. In the winter when it's dark and cold and snowing can you still get 14 kWh? Unlikely.

        If you try for mixing with online power to increase utiliza

        • You've suggested an interesting value add by integrating a generator. Combined with the Tesla battery system, the home's electrical power quality suddenly becomes UPS grade.

          It seems obvious, but I don't hear Tesla touting their system as a component in better power, only green.

      • 10K kWh per year reads better to those unfamiliar with electrical units as 10,000,000 Watts per year. When put in "light bulb" terms, people start to get just how much electrical power a single US home uses. Staggering.

      • "Tentative Conclusion: The battery is right on the verge of being cost effective to buy across most of the US for day/night arbitrage. And itâ(TM)s even more valuable if outages come at a high economic cost."

        Except that as the prevalence of storage becomes higher, the day/night arbitrage gets lower and so the cost effectiveness of storage goes down.

        California has already hit this for solar, the peak load on the system is now right after dark when the solar cuts out and people get home and turn on their gadgets. People that bought panels and computed the lifetime cost curve based on the old peak plans are now never going to recoup their investment.

  • Let me start by saying that I'm very eager for this sort of thing. But not yet, economically. Bless you early adopters, keep it up.

    Musk says there are four to five million new roofs built each year in the US, and the solar roof product will be price competitive with more traditional roofs with solar added to it. However, existing roofs which do not need to be replaced will be better candidates for more traditional roof-mounted solar solutions.

    Translation: 137 year ROI.

    • by dbIII ( 701233 )
      There have been a few products of this type such as some in the UK. Tesla are not the early adopters and neither will be their customers. I think it will get cheaper though just as the panels did once some huge factories came online.
  • Only probs is that while everyone knew about solar roofs, one jerk patented it insuring no one would make them. Basically at this point, anything is better than regular shingles even if it doesn't make electricity. If you can find a legal way of doing solar roofs, that saves the customer every 35 years they need to replace.
  • quasi-infinite? (Score:2, Interesting)

    by Anonymous Coward

    "quasi indefinitely," even in harsh conditions where snow and ice make short work of traditional asphalt shingles. Musk said that 50 years of lifespan should be no problem

    Europe has buildings with 1000 year old roofs, and it is somehow a little bit amusing to hear 50 years referred to as "quasi infinite".

    • Are they really 1000 years old? Or have they been maintained over the centuries. Filling cracks, replacing broken parts. I expect you will see roof maintenance at least a couple time a century.
      The standard home in the north east us is the sick built home with shingle roofs that last about 30 years. These homes while not meant to last a century are comfortable and do the tick for the price.

  • As long as Musk isn't paying people to install it and paying them to accept the free power, we'll have the Global Warming deniers and their buddies complaining about this...and their lobbyists trying to have it made illegal.

  • The powerwall is all cool-looking and compact, but I don't actually budget a lot for fashion statements in my basic infrastructure.

    I see that wal-mart sells "deep discharge marine batteries" that hold about 1kWh for $99. So that's $1400 to duplicate a powerwall's storage. I guess if a powerwall can take over 4X as many cycles as lead acid, it wins. For solar and daily cycling. (My interest is getting through The Big One with a $500 generator that doesn't have to be on 24H a day, so I think the cheaper

    • Li-ion batteries still suck, but lead acid suck at least 10 times as much!

    • by swb ( 14022 ) on Saturday October 29, 2016 @07:20AM (#53174383)

      I think lead acid isn't terrible if you have the space, but really to get the most life out of a lead acid battery you have to look at max discharge as about 60% even using absorbed glass mat (AGM) batteries to get anything like long life cycles.

      So your 1 kWh battery is only really useful for about 400 Wh which means you need 35 of them.

      But it's more complicated than that, as you'd be better off driving an inverter at 48v and using something like 6v golf cart type batteries arranged in series/parallel strings to get to 48v and probably want some kind of more sophisticated charging/monitoring system to keep track of individual batteries and be able to isolate 48v groups if a unit failed. Usually more individual batteries gets you higher aggregate discharge rates since you pull less from any one battery.

      I don't think it's impossible to built a decent setup, but doing it right will end up being more expensive than you'd think and will end up sucking a ton of space.

      I think the half assed compromise is probably 4x 8D AGM 12v batteries in a 24v series/parallel combination, which would get you close to 14 kWh. But the batteries alone are $2k and then the inverter more yet.

    • Lead acid batteries are normally closer to $400/kWh(B), but some get lower. The factors you are missing though are:
      -Limited to about 300 cycles at full discharge or 1,000 at 50% discharge.
      -Lower cost batteries have lower round-trip efficiency
      -Physically much larger and heavier
      -Charge/discharge rate ratio is much worse
    • BTW, for the Big One, you are better off with 4-6 12V/200Ah lead acid and portable generator. Ideally two generators, one that you test and service every month and one that has never been used...

      I am still surprised that nobody mass markets a refrigerator UPS that can provide 24 hours backup for the fridge, plus 100W for basic home electronics, with built-in inputs for utility and a portable generator.
  • by swb ( 14022 ) on Saturday October 29, 2016 @07:38AM (#53174417)

    I think the PowerWall would be most useful with a smart panel that allowed individual circuits to be prioritized in various ways when running off battery power to maximize run time.

    Like maybe the lights should be always on, the fridge given a high priority, the dishwasher not on, some circuits which could be cycled off to meet some other intermittent circuit's demand for power, and what order circuits could be killed off to maintain run time for the highest priority circuits.

    Of course, most houses aren't wired that sane. Even in parts of my house where new circuits were run from a new panel during remodeling, electricians are prone to tapping whatever's close for power. I demanded a 20A dedicated circuit for the entertainment center, but the junior guy didn't get the dedicated message and tapped it for two ceiling lights and a hallway outlet.

    I don't know how totally new construction is done, but I'm guessing its not done in a completely structured way except where code dictates dedicated circuits. But it would be great if there were individual circuits for lights by room, outlets by room, and then various specialty circuits for fridge or other items that should be addressed individually.

    • by thegarbz ( 1787294 ) on Saturday October 29, 2016 @10:49AM (#53174853)

      individual circuits to be prioritized

      This can't be solved at the circuit level and is also precisely the point of the "smart appliances" that are so often shamed here on Slashdot. You can't just cut the power to a dishwasher, there may be reasons why it needs to run, also if it is running and you cut the power well that's it, you end up with half dirty dishes and a system stopped mid cycle that needs to start again.

      Better still, move towards some open standard where devices can share this information with each other, and then they can intelligently figure out what to do. My Nest already knows when I'm expected home so the dishwasher should be able to know both if I'm expected home shortly and if I'm no battery power. If I have oodles of power to spare and I'll be home in the next 30min it should keep running even if it is draining the battery. If I won't be home for another 6 hours, well it should stop itself.

      Smart homes need smart protocols, not turning circuits on and off. I hope we can get there someday.

      As for electrical codes, much of the world has things like lights daisy chained, and the move to LEDs means we can not put even more lights on a common circuit. Circuits are pretty much setup depending on max load, it's only when someone smart comes in and says something like please run separate circuit for the fridge so a ground fault somewhere else in the house doesn't cause me to get greeted by rotting meat when I get home. You won't find intelligence in wiring codes.

      • by swb ( 14022 )

        You can't just cut the power to a dishwasher, there may be reasons why it needs to run, also if it is running and you cut the power well that's it, you end up with half dirty dishes and a system stopped mid cycle that needs to start again.

        You *can* just cut the dishwasher, because the worst thing that can happen is you have to run the cycle again. Medical equipment and some life safety equipment can't be cut and when the power goes down and there has to be a way to prioritize it over dirty dishes.

        I'm with you on the ideal view that all things electrical should be able to talk to a power manager and be shut down individually, but I guess I don't see that as entirely realistic, either. Not everything can/will/should have a programmable netwo

        • You *can* just cut the dishwasher, because the worst thing that can happen is you have to run the cycle again.

          The dishwasher is just an example but this is precisely what I'm getting at. You cut the power to the dishwasher to save energy requiring you to repeat a whole cycle? That's a silly idea, especially from a device that many people time for convenience sake so it's ready when it gets home. I agree if you have life saving medical equipment then you're not going to care if your dishes aren't done, but that's no reason to go back to the technological equivalent of bashing rocks together when the method of manufa

          • by swb ( 14022 )

            I don't think I could comprehend in what world you could consider a 14kWh system puny.

            My electric bill in July was 1900 kWh. 14 wouldn't get me 6 hours that month.

    • I demanded a 20A dedicated circuit for the entertainment center, but the junior guy didn't get the dedicated message and tapped it for two ceiling lights and a hallway outlet.

      More likely the actual electrician just said to himself "f*ck this idiot and his pointless demands".

      • by swb ( 14022 )

        He blamed it on his junior guy, but I saw it before the wallboard went up. I had two dedicated runs in the house and the "junior guy" flubbed both.

        He fixed both, but he didn't want to, "two lights and a mostly unused outlet won't consume much power". I finally had to tell him either it gets put the way I want it, or another electrician fixes it for him and that will be deducted from his bill.

    • It would probably be better to have the appliances themselves do the load balancing as opposed to the circuits. As long as we are going to end up with an internet of things, have the house stagger when the AC and refrigerator compressors start up and turn off the electric oven/range and water heaters for a few seconds whenever a big motor starts up as well. That way when someone hacks your house they can burn out your batteries, inverter, HVAC, and refrigerator by turning on everything in the house at the
  • Sadly the power companies and lobbyists in Florida are trying to make home solar illegal. and the populace is far too stupid to vote it down.

  • The solar power part is nice and all but best part is that now I can finally throw stones inside my glass house! ;)

  • When one or two firemen are electrocuted fighting a blaze this stuff will be gone - or the flipside, no insurance company will cover your home as the fire department will not go up on the roof. Heck, that may happen even with more traditional panels sooner than later.

    With earlier model panels, it was sufficient to have a cutoff near ground level as they were not efficient enough to still be a major risk. Apparently not any more. Firefighters are also nervous about going up on a roof that is overweighted

  • by Dan East ( 318230 ) on Saturday October 29, 2016 @10:44AM (#53174839) Homepage Journal

    I see one downside to this, which is heat. Counter intuitively, solar panels are less efficient the warmer they get. That is why solar panel installers always leave an air gap between panels and a roof, to allow airflow under the panels to help cool them. An air gap of 3-5" is recommended. When the panels (in the form of roofing tiles) are laid directly on the roof, not only is 50% of the surface area for cooling lost, but the heat of the attic is also warming them from the below. As anyone who has been on a hot roof in summer knows, roofing shingles get incredibly hot.

    This may be offset somewhat by the fact that these shingle style PV cells will cover more surface area of a roof than normal solar panels. However it is definitely a factor, and thus a given square footage of these new tiles cannot be as efficient as the same area of standard PV panels for the heat efficiency factor alone.

    • Some manufacturers incorporate water cooling pipes into their solar panels. Keeps the PV cells cool and efficient. Produces hot water which is usually a welcome side-effect. Tesla's shingles don't have water cooling yet, but I'm sure it will come.
  • Should be interesting to see how well Tesla fares with this. Dow Chemical put a lot of money behind the same concept (less the battery whose purpose vs. cost seem like they would be difficult to justify) and they gave up the market due both to technical complications of installation/maintenance and poor sales due to low market interest. And that was just a few months ago, so I doubt much has changed: https://www.greentechmedia.com... [greentechmedia.com]
  • ECD had solar shingles back in the '90s, and the work Stan Ovshinsky was doing improved both their average productivity and durability significantly while reducing production cost. After he retired though the company went downhill and eventually went out of business. How does the new Tesla offering compare to the Ovshinksky offerings from a decade or two ago?

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