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Film Turns Windows Into Solar Panels

Posted by samzenpus on from the peel-and-stick-power dept.

itwbennett writes "At the Ceatec electronics conference in Japan this week, 3M is showing film that turns windows into solar panels. Although the product only generates about 20% of the electricity of a traditional solar panel, it will cost about half as much, is much easier to install, and takes up no additional space. 'An average person could go to the store, buy some of this, and then bring it home and install it themselves,' said Yasuhiro Aoyagi, a senior manager in the company's construction markets division."

23 of 186 comments (clear)

  1. about time... by tverbeek · · Score: 3, Funny

    It's about time someone found a good use for Windows.

    --
    http://alternatives.rzero.com/
  2. Sun Shade by malignant_minded · · Score: 2

    "The film blocks or absorbs about 80 percent of visible light and over 90 percent of infrared light, so it also acts as a sunshade"

    Thats pretty dark. Now you don't have to live in the basement

    1. Re:Sun Shade by SomePgmr · · Score: 2

      Well if you're generating that power and keeping your AC from kicking on, you could be looking at a win.

    2. Re:Sun Shade by raygundan · · Score: 2

      We have shade screens that block 90% of the visible light coming into our house, and surprisingly, it doesn't look dark at all. (But it cut a HUGE chunk off our utility bills.)

    3. Re:Sun Shade by dgatwood · · Score: 2

      Seriously. It blocks as much light as putting up a full blown solar panel that covers 80% of my window, but only produces a fourth as much power.

      So let's do the math. A typical solar panel has anywhere from 6% to 20% efficiency. Let's generously assume that this is 20% of the efficiency of a fairly good one, so... sat 4% efficient. 4% of the energy from the sun turns into power.

      Now sunlight is about 93 lumens per watt. CFLs only produce about 75 lumens per watt. So even if you had 100% efficient capture of sunlight, the lamps would produce only 81% as much light.

      Multiply. This means that for every 100 lumens of light that would ordinarily come into your window, 20 lumens pass through the film. 4 lumens become electricity, and 81% of that, or about 3.24 lumens, is available by the time you convert it back to light. Thus, the total lumens available between the sun and the artificial lighting powered by the solar panel film would be 23.24 lumens.

      So assuming that, like most houses, the amount of light you get in the room from sunlight is barely adequate even without this film, then you would need to replace 80 lumens for each 100 lumen window that you cover, at an efficiency of 3.24 lumens per window, which works out to just shy of 25 windows to replace the light provided by a single window. Assuming (for simplicity) that the rooms in your house all have about the same number of windows, this means that you would need a house with 25 unused rooms just to break even.

      I can't imagine how you could possibly save enough money on cooling to be make up for the added lighting costs at a paltry 3.24% best-case light-to-light conversion efficiency. It's just not significantly better than draping a thick blanket over the outside of the window and blocking out the sunlight altogether, but doesn't block as much heat as the blanket.

      An 80% tint is just insanely dark—darker than the darkest I've ever seen on any building—that's like pimpmobile window tinting dark. Now if you have an electric car and you want your windows darkly tinted, then maybe, though I suspect an 80% tint is illegal in all 50 states and the District of Columbia. Not that you care when you're driving along in your tricked-out electric pimpmobile, but.... No, wait....

      --

      Check out my sci-fi/humor trilogy at PatriotsBooks.

  3. Am I the only one... by ArsenneLupin · · Score: 3, Funny

    ... who misread this as "Film turns Windows Into Solaris"...

  4. Re:Average person rewiring their house? by Abstrackt · · Score: 2

    I imagine that if/when this tech is available at the hardware store there will be companies selling borderline-foolproof kits.

    --
    They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance. - Terry Pratchett
  5. install it themselves? by roc97007 · · Score: 2

    > 'An average person could go to the store, buy some of this, and then bring it home and install it themselves,'

    This is really a selling feature? Anyone can go to amazon.com, buy any one of a number of solar panel kits, get it delivered to their home, and install it themselves, with the panels inclined correctly to maximize exposure to the sun (unlikely using existing windows, which have different design considerations) and get the full output of a solar panel, not just 20%, and never have to leave their home. (Speaking from personal experience.)

    Mind you, it might be interesting to build a house designed to maximize the use of the technology, for instance, big skylights that are also solar panels. But a film for existing windows? There are better solutions.

    --
    Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
  6. Return on investment by ickleberry · · Score: 3, Interesting

    Normal solar panel takes 10-15 years to pay for itself. If it only produces 20% of a normal panel it won't be worth it unless it costs about 20% of a normal panel

    1. Re:Return on investment by MrTester · · Score: 2

      With normal solar panels you have to pay someone nearly as much as they cost to install them. These you can install yourself. That can cut the true total cost in half right there.
      TFA also states that it takes less sunlight to power these than traditional cells, so while they are less efficient, they will generate power for more of the day and on more days.

    2. Re:Return on investment by ProfessorPillage · · Score: 2

      Assuming no subsidies anywhere along the production/sales/installation process making the solar panels feel artificially cheap.

      And what about the subsidies that make conventional electricity feel artificially cheap?

      Nor counting losses converting power to storage and back again to match energy demand that doesn't coincide with peak production.

      Solar production tends to match up pretty well with peak demand. Better than, say, regular power plants.

      ...or just use the usual tactic, ratchet up the subsidies a little more to further hide the underlying inefficiencies.

      You're right, it's only fair to subsidize energy from fossil fuel sources. You know, real energy.

    3. Re:Return on investment by roc97007 · · Score: 2

      Ok hang on.

      I'm not a big fan of solar power, I think solar solutions are *way* oversold, but there are cases where they pay for themselves immediately.

      I had an issue where a new building on my property needed power. I had the city come out and mark where all the utilities were, so I could trench it myself and only have to hire out running the actual electrical and wiring it into the panel. (Which I could also do, but I'm not licensed so it'd put me in a legal grey area...)

      So I pick my path, and start digging the trench, and run into a pipe that wasn't on the city's plat map. It's obviously a wet pipe (water, sewage or drainage) and it's only 18 inches down, and it combines with the other utilities to make it impossible to trench from the new building to the existing house without crossing a utility. In my area, electrical MUST be buried 24 inches down and MUST NOT cross under a wet pipe. (It's ok for electrical to cross *over* a wet pipe as long as it's 24 inches below ground.)

      This resulted in making it impossible to run electricity to the building in any way I could afford. So I started looking into alternatives. Wind power was out, as wind is noisy and I have neighbors nearby. But solar looked like it would work.

      So I planned it out and (this is the point) to my utter amazement, the cost of the solar kit was *less* than the total cost of labor to wire the building into the house. Of course, I had to assemble and wire it myself, but I'm willing to trade sweat equity for having to hire contractors, and I learned valuable information useful to design a larger installation for the main house.

      So, I understand what you're saying, but in some cases, the savings, especially for a new installation, can be immediate, if total cost (not just the cost of power) is factored in.

      Consider: If you wire just one circuit to solar, and put your freezer and fridge on that circuit, you only have to save your food a couple times during major power outages before you've paid for the installation.

      --
      Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
    4. Re:Return on investment by ProfessorPillage · · Score: 3, Informative

      You're right though, fossil fuels (for example) are an actual energy source when compared to typical current photovoltaic solar panels which use more energy to produce than they'll generate over their lifetime (and that's before the conversion losses). The typical solar panel you see on a rooftop is really more a coal burning panel.

      Now you're making things up. According to NREL, back in 2004, the time needed to generate the amount of energy used to produce solar panels was about 3-5 years or less, depending on the type of panels ( http://www.nrel.gov/docs/fy04osti/35489.pdf ). The financial payback time (time to recover the dollar cost through savings on your bill) without subsidies is longer because you're paying for more than manufacturing energy, and because the competing technologies are both subsidized and are also larger, more established industries.

      According to Murphy & Hall ( http://dx.doi.org/10.1111%2Fj.1749-6632.2009.05282.x ), the EROI for PV is 6.8. That means it takes one unit of energy from somewhere else to result in 6.8 units of electricity from the panels. Compare that to natural gas, which has an EROI of 10, which means it takes 1 unit of energy from other sources to get enough gas out of the ground to burn for 10 units of energy. This comparison doesn't take into account that the "energy returned" is in the form of a finite resource you have to burn in the case of gas. In other words, with 1 unit of natural gas, you can generate 6.8 units of electricity by using it to build PV, or you can get around 0.4 units of electricity by burning it in a turbine, after deducting the amount needed to get another unit of gas out of the ground. For comparison, the same source says that nuclear power has an EROI of 5-15, and coal is higher at 80. Again, this doesn't take into account that you're using the fuel itself.

      Nothing against research into solar energy, just when you find people deploying with current technology onto their rooftops (or window panes) and announcing their "helping the environment" or that they have a "carbon neutral" energy source or that what they're doing makes economic sense is laughable.

      In terms of environmental impact, grid-tied solar power makes sense with today's technology (or 10-year old technology for that matter). In terms of dollar cost for putting it on residential roofs, maybe you don't save money without the subsidies. For the window film, who knows.

      Solar panels are not carbon-neutral, but they generate about 90% less greenhouse gas emissions than the conventional plants they displace, which are primarily coal- and gas-fired.

    5. Re:Return on investment by tragedy · · Score: 2

      The notion that solar cells produce less power than they take to make is pretty outdated if it was ever true to begin with. Look at
      this pdf from the DOE. The only kind of solar cells that dogma might actually apply to are high efficiency ones used for applications where cost-effectiveness isn't the point, but rather absolute effectiveness.

    6. Re:Return on investment by aphelion_rock · · Score: 2

      Normal panels are typically less than 20% efficient, so if these panels are only 20% of that then these panels are less than 4% efficient. - A lot of work for not much power.

    7. Re:Return on investment by dbIII · · Score: 2

      typical current photovoltaic solar panels which use more energy to produce than they'll generate over their lifetime

      Well, if you never take them out of the box and keep them stored in the dark that's going to happen.

      The really amusing thing here is the poster above submitted his rubbish via a computer that is now affordable due to vast energy savings over the last few decades in the production of silicon wafers. One guess as to what silicon solar cells are made from.

  7. Re:Average person rewiring their house? by localman57 · · Score: 2

    plug a small power plant into their house's electrical system

    A very very small power plant. TFA says it's enough to "Charge an iPhone". Assuming you're charging over USB, an iPhone pulls a max of 500ma at 5V, or 2.5 watts. Not enough energy to warrant upconverting it to AC, given that there's efficiency losses there. Given that you can only charge your iPhone under the best of circumstances, this seems like yet another not-market-viable solar technology. But, ya gotta start somewhere. Maybe they'll make it better. None the less, the applications are on windows, most of which aren't oriented to maximize direct sunlight angle anyways, so it's probably even worse in application than they're talking about here.

  8. Re:Average person rewiring their house? by amorsen · · Score: 3, Informative

    Actually it is dead easy these days. You buy an inverter which plugs into any socket. It doesn't support "island mode", so if the grid power fails, the solar power goes out too.

    They are not universally legal, so check the local laws. They are about as safe as anything gets when electricity is involved.

    --
    Finally! A year of moderation! Ready for 2019?
  9. Re:Average person rewiring their house? by localman57 · · Score: 2

    Also interesting... If it is indeed, 2.5 watts, that's 1/400 of a killowat. If your window generates that for an hour, you get 1/400th of of a kilowatt-hour. At 10 cents per kWH, you earn roughly 1/40th of a cent worth of electricity per hour. Even if you get 8 good hours out of the thing a day, it takes 5 days to generate a penny worth of electricity...

  10. 80% is high visibility ?? by MycoMan · · Score: 2

    Paragraph 2 says: "still allows for high visibility."

    Paragraph 6 says: "The film blocks or absorbs about 80 percent of visible light"

    I am not an engineer - but can you actually prevent 80 % of visible light from getting through and really claim there is "high visibility" ?

    1. Re:80% is high visibility ?? by rocket+rancher · · Score: 2

      Paragraph 2 says: "still allows for high visibility."

      Paragraph 6 says: "The film blocks or absorbs about 80 percent of visible light"

      I am not an engineer - but can you actually prevent 80 % of visible light from getting through and really claim there is "high visibility" ?

      Indeed you can. In order to see clearly, humans need only a fraction of the visible light of a typical sunny day. During the day, your pupils are contracted, allowing relatively little of the available light to hit your retinas; you would be blinded by the glare if your pupils allowed all available light in. Blocking eighty percent of the light on a clear day at noon still leaves a lot of light, more than enough to see clearly with. Your pupils would simply dilate enough to compensate.

  11. Re:Average person rewiring their house? by zennyboy · · Score: 2

    I live in Spain. In general (our house included) we have NO windows facing the sun...

  12. Fake specific numbers hiding a fuzzy lie by dbIII · · Score: 3, Interesting

    The numbers are going to vary depending on how much grid electricity costs where you are, how much electricity you use, how much sun you get, which panels you use, how much 12V DC stuff you run, how much you run through an inverter and which inverter you have. I probably left a few things out - batteries for one thing but not all installations have them.
    Since reality is so hard to pin down you have to ask yourself where the confidence of the above post comes from. Is it ignorance and just parroting some specific case? Or is some petty little agenda being pushed to put those greasy engineers and smelly hippies in their place as mere consumers instead of rocking the boat? Either way the above poster IMHO deserves contempt.
    Two decades ago some solar panels in the right place paid for themselves on installation if they cost less than getting a line in from the grid. It's not just about being green.