Panels inside behind glass?

boisblancboy
boisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
If you are using a panel inside the house but getting plenty of sun through a CLEAN window, would that make a significant difference in output? Just got thinking with newer windows that block the suns heat wasnt sure if this would have an affect on a solar panel.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Panels inside behind glass?

    Placing solar panels behind windows will cost you quite a bit of energy...

    From the iron content of standard glass (which blocks some light), to Low-E glass which blocks some more light, to the extra reflections from additional air/glass interfaces--you will lose a lot of power (50% or more????).

    Here is an example of how glass interferes with a solar cell's spectral response.

    The simple test... Take any silicon solar panel (big or small) and connect it to a DVM set amps. The amp reading in sun and behind glass will give you a very exact reading on how much power you will lose (the current output of a shorted silicon solar panel is proportional to the amount of sunlight energy hitting the panel).

    You also need to take into account that fact that most people's windows are near 90 degrees (vertical). And for much of North America, the ideal angles are closer to 20-40 degrees. Only in winter (and farther towards the north) does running a panel vertical not hurt you (and in some cases may help increase power collected during the winter months).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • boisblancboy
    boisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Panels inside behind glass?

    I just tried it with a small 5 watt panel that I have and there was a difference in both voltage and amps. I didnt happen to think about it until today.

    Now some of the glass that is covering some panels modules, that is obviously glass with less other minerals in it?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Panels inside behind glass?

    Yes, the glass is both very thin and "low iron" content.

    Just looking around the "Internet":

    One Chinese company:
    Jinjing group co.,ltd has constructed the sole one low iron glass line in China by use American PPG technology that with higher light transmission.4MM can reach 91.60%.It is mainly used for solar energy device,solar panel,greenhouse,automotive industry glass,horticulture,top-grade furniture,IT products,electrical home appliance,aquarium,solar lighting and etc.The thickness:2.4-22MM,The biggest size is 3300x12000MM

    Here is another manufacturer. They have a neat picture of the edge view of normal and low iron glass. The normal glass has a darkish green color, the low iron has a clear white edge on view. They also have a chart that shows how thickness of even low-iron glass will reduce solar energy (1/8" vs 1/2"; 89% vs 80%--and UV reduction is even more).

    The difference between regular and low iron glass:
    The transmittance rate for our Photovoltaic Glass is around 91 percent and for regular glass is about 83 percent. This 8 percent difference can be significant over the thirty to fifty year life of a solar module.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • boisblancboy
    boisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Panels inside behind glass?

    Do most makes/models of solar panels have a glass covering? They obviously need to be protected with something, but if they didnt use glass at all that would increase output a few percent one would think. But if your panel is damaged there goes your output completely.
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: Panels inside behind glass?

    Yes, solar panel "glass" is made to allow as much energy through it while still protecting the panels under them. Typical newer window glass tries to keep most UV and even IR out of the living space while only letting visible light in (typically 60-70%), which seems counterproductive to solar heat gain in northern climates...
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Panels inside behind glass?

    Most "good quality" use glass. Some (like Unisolar) use some sort of plastic (because they are flexible panels). Much more rock resistant than glass.

    You cannot really use "bare" silicon cells on earth because the water, moisture, and dust will corrode the cells and their connection points (the "glass" costs you about 10% power loss).

    In space (and on Mars Rovers) they use bare cells--but much of that is simply to save weight.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • boisblancboy
    boisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Panels inside behind glass?

    Great thanks guys, good information. Its just very interesting to me that something so simple as solar panels, to the untrained eye anyway, keep getting more and more complex. Along with all the applications and equipment that go along with it.
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Panels inside behind glass?

    Window glass has much higher losses - up to 40%