The best solar cells out there?

[mitchellleary]

Hi,

What are the best solar cells for size out there? I am looking to buy some to lay on the deck of an autonomous solar-powered boat that I have designed and am in the process of building. I wouldn't be able to accommodate huge cells on the deck of my boat and need as small as possible but want the highest efficiency that people can recommend out there.
I know solar-tech is advancing extremely quickly at the moment so hit me with your top recommendations!

Another quick question I have is that I spoke to someone recently and I told them I was going to cover my cells in epoxy on the deck and he said that this would reduce dramatically the efficiency of the cell. Is this the case?

Thanks in advance for your time.

Mitch

[jflorey2]

What are the best solar cells for size out there? I am looking to buy some to lay on the deck of an autonomous solar-powered boat that I have designed and am in the process of building. I wouldn't be able to accommodate huge cells on the deck of my boat and need as small as possible but want the highest efficiency that people can recommend out there.

Fraunhofer/Soitec now has quad-junction cells that hit 46% efficiency. Expect to spend around $10,000 a watt.
Alta has thin film GaAs cells at around 30%. They are around $50 a watt.

Another quick question I have is that I spoke to someone recently and I told them I was going to cover my cells in epoxy on the deck and he said that this would reduce dramatically the efficiency of the cell. Is this the case?

Depends on the spectral transparency of the material, and how easily it sheds dirt and other deposits (like salt.)

[badley]

you cant epoxy them in, heat expansion and contraction will micro-fracture them .. i would just build panels, see what will fit, maybe make them modular/smaller size and removable maybe to suit your space .. the best cost effective cells are the poly 6 inchers, theres some out of china that are 19+ efficiency but expensive even for factory blems .. you can find ~17 or so efficiency polys that will do fine, i'd steer clear of monos- anything worth a crap with monos is super expensive, never tried those, i have my doubts about their ability to actually produce more power in an average day than a poly .. as far as build scheme you could do the thick glass/silicone encapsulant like alot of people .. i chose to use a double pane of regular window glass and sandwiched and sealed the cells inbetween, its alot cheaper .. only drawback in your situation is something hard hitting them .. i havent had a problem, i made the frames out of angle aluminum and supported/glued the panels to them good in the back, but mine are on the roof .. been up there for 7 years ..

[SunEagle]

you cant epoxy them in, heat expansion and contraction will micro-fracture them .. i would just build panels, see what will fit, maybe make them modular/smaller size and removable maybe to suit your space .. the best cost effective cells are the poly 6 inchers, theres some out of china that are 19+ efficiency but expensive even for factory blems .. you can find ~17 or so efficiency polys that will do fine, i'd steer clear of monos- anything worth a crap with monos is super expensive, never tried those, i have my doubts about their ability to actually produce more power in an average day than a poly .. as far as build scheme you could do the thick glass/silicone encapsulant like alot of people .. i chose to use a double pane of regular window glass and sandwiched and sealed the cells inbetween, its alot cheaper .. only drawback in your situation is something hard hitting them .. i havent had a problem, i made the frames out of angle aluminum and supported/glued the panels to them good in the back, but mine are on the roof .. been up there for 7 years ..

So your home built panels have been outside and working for 7 years!!! That is a lot longer than possible without the proper sealing of the cells which includes poly or thin film type.

What have your used to keep the moisture out? Corrosion is the result of the cells getting wet and the main reason DIY panels fail shortly after getting rained on or see a temperature changed. Unless you have eliminated all air (and the moisture that is captured in it) from the cells it will condense and cause corrosion.

[J.P.M.]

you cant epoxy them in, heat expansion and contraction will micro-fracture them .. i would just build panels, see what will fit, maybe make them modular/smaller size and removable maybe to suit your space .. the best cost effective cells are the poly 6 inchers, theres some out of china that are 19+ efficiency but expensive even for factory blems .. you can find ~17 or so efficiency polys that will do fine, i'd steer clear of monos- anything worth a crap with monos is super expensive, never tried those, i have my doubts about their ability to actually produce more power in an average day than a poly .. as far as build scheme you could do the thick glass/silicone encapsulant like alot of people .. i chose to use a double pane of regular window glass and sandwiched and sealed the cells inbetween, its alot cheaper .. only drawback in your situation is something hard hitting them .. i havent had a problem, i made the frames out of angle aluminum and supported/glued the panels to them good in the back, but mine are on the roof .. been up there for 7 years ..

Can you explain why you use double pane regular window glass ? I'm curious. Does that improve overall efficiency ? Or does that improve the temperatures ?