Off Grid Home Forums Technical Discussion Any Energy Gained From Solar Panels Toward Water

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    Hi All,

    I am wondering if I were to install solar panels over water (I live on a lake) if much energy would be produced from light reflected off the water. I am thinking if the panels faced BOTH up and down maybe I would gain additional current. What does anyone think? Ever seen this or heard of it?

    I know light can be used reflected off a mirror but it seems this was always in very controlled settings and of course there was some loss of flow. Just daydreaming about how much might be gained there as you know how you can get a sunburn from reflected sunlight when you are on the water.

    Nick Rosen

    If you are talking about facing half of your panels up, and half down, then you would be loosing a LOT of your potential and would want all of them facing the sun directly.

    If you are talking about a single panel’s ability to create electricity from light that strikes from below, I wasn’t aware that they performed that way, but I really don’t know . . . but I can say that once you face your panels toward the sun for maximum efficiency, there will be very little sunlight reflecting off the lake and hitting them.

    If panels produce power from light striking both above and below then you would see some gain from having panels suspended over water, but very little.


    I wasn’t thinking of putting half my panels down, but wondering if I added panels in the space I have available that were also facing down “underneath” panels that face up if I would be making good use of the space I have. The prime concern I had was payback as the cost of putting panels in that are only say 60% as efficient as upwards facing may be futile.

    Other options may prove better but would require some home construction modifications and so I was just thinking it over.

    Thanks for your input, it is appreciated!



    As someone with a physics degree and who has taught high school physics (lamentably… and i know there’s a lot wrong with what we teach, anyways), and currently as an engineer interfacing with the renewables field; i can confidently clear this one up. Most of the radiation from the sun is transferred into the water, a very small fraction is reflected, even if it is a fraction that will produce a sunburn. Although I’ve never come across anyone claiming reflected sunburn and find it hard to accept. Sadly it’ll be a complete waste of time mounting panels on the back – you lose so much in potential energy converted from non-direct incidence. Basically the best thing you can do is angle your panels in a way so they face the sun directly for as much of the time. I think you’d be lucky to get anything close to 5% from a backward mounted panel. Admitedly this is a guess, its not worth doing the calcs and solar panels dont do a lot with diffuse radiation. Hopefully in about ten years we should have solar panels with double efficiency (like 30%), but this likely to be the limit of the technology. We can still hope for better solutions. Ever come across this? ? I’m trying to research alternatives like high powered magnet heating and EM generation – its all viable, we just dont have manufactured products yet. Keep your eyes peeled!


    PVA’s work best under direct sunlight but only at about 14%. Additionally, not all types of light produce electricity from a PVA at the same level. Since backscatter from water is lower in intensity, lacks some of the full spectrum, and is less focused, it adds little to the total from the cells. Better to add silvered reflectors or a rotation system to keep the cells under full intensity for longer each day.

    NREL has already shown a cell with 40.8% efficiency but requires special manufacturing and handling steps so, RSN (real soon now). As an aside, it splits the incoming EMS into 3 parts and produces an electron from each of the partial photon making 3 electrons from 1 photon instead of 1 electron from 1 photon.


    It’s a really lovely discussion.

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