Solar power

stess
stess Registered Users Posts: 1
in Solar Beginners Corner #1
what would a 5mm X 5mm solar panel accumulate in solar power? Is it possible to harness the suns power and store it with a solar panel this size or even smaller? Say, the size of an eraser? (Elementary school project)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Solar power

    Welcome to the forum.

    With existing technology it would be a wasted effort. The best commercially available panels are about 20% efficient, and with standard insolation at 1,000 Watts per square meter a panel that is only 25 square millimeters wouldn't produce enough to make it worth hooking wires to. You're looking at 1/40,000 of a square meter there, so the potential power would be only 0.025 Watts, and with the material only 20% efficient the net result would be 0.005 Watts (unless I slipped a decimal somewhere). The resistance of the conductors would literally use up the power produced.

    We need better solar panel materials.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #3
    Re: Solar power

    Digital watches and calculators are devices that can use small amounts of power and, therefore, are canidates for small solar panels.

    For example, say a digital watch uses a 200 mAH battery at 1.5 volts for 3 years:

    0.2 amp*hours * 1.5 volts * 1/3 years * 1/365 days per year * 1/24 hours per day = 0.00027 Watt = 0.011 milliW

    Take Marc's 5 milliWatt solar cell example:

    1 hour * 5 mW / 0.011 mWH = 455 Hours of operation per 1 hour of sun (~19 days)

    My Casio solar power watches will actually run for several months on one charge for ~2 of hours of direct sun.

    For portable electronics, it has been more the design and high efficiency (low power usage) of electronics that have driven the portable electronics market than battery technology. Modern digital electronics has drastically reduce it power usage over the decades, whereas battery capacity has remained relatively stable (WH per unit volume).

    The newer batteries can be much lighter, and supply higher current/charge quicker than older chemistries--But these are relatively small changes vs the changes allowed by "Moore's Law" with respect to electronics.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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