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Last Post 3/24/2020 1:21 PM by  Kelly Larson
Volts from sun?
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3/24/2020 7:25 AM
    (from Answer Garden)

    How many volts does the sun give?

    Christina Cohen

    Basic Member

    Basic Member

    3/24/2020 12:50 PM
    Power, not voltage, is really the thing to think about. The amount of volts you get from a power supply depends on the current you need. If you need more current, you get less voltage and vice versa.

    So, one might ask how much power does the Sun give? The answer to that depends on where you are since power decreases very quickly as you move away from the Sun. A spacecraft currently in space, called Parker Solar Probe, uses solar panels to power all the instruments on the spacecraft. When the spacecraft is near Earth's orbit it uses all the solar panel area to gather the power, but when it goes close to the Sun (so far it has gotten 5 times closer to the Sun than the Earth), the spacecraft actually folds back the solar panels so it only uses the tips to generate power. Being so close to the Sun means the spacecraft only needs a fraction of the solar panel area to provide the same amount of power.

    In contrast, spacecraft like New Horizons which went out to Pluto couldn't carry solar panels big enough to provide the power it needed once it was beyond about Jupiter's orbit. The power from the Sun is just so much less out there.

    On Earth, on a cloudless day, the Sun provides more than enough power for a lot of our needs. Over the 6 hours that the Sun is pretty high in the sky, the power collected by a system about the size of small swimming pool would be enough for about 10 houses for a day. The problems are that the Sun isn't up all the time, we don't always have cloudless days, and we're don't have great ways of storing that energy to use for later. People are working on it though and the systems are continually improving!

    Kelly Larson

    New Member

    New Member

    3/24/2020 1:21 PM
    Great question!  When working with photovoltaics, (solar electric panels, solar, or PV), each PV cell gives about half a volt.  So while it isn't the sun that is producing the voltage, it is the PV cells reaction to sunshine.  

    We measure the power, (the amount of work that can be done), in watts.  The sun gives us plenty of power to do all the work we do on earth.  The conversion efficiency from the sun's rays to electricity is about 10-20%. We need to put up enough panels to produce the power we need for the work we want to do.

    The sun's power output varies throughout the day.  First thing in the morning there is low irradiance, (the power in the sun).  At noon on a cloudless day, the irradiance is a a maximum, and then at dusk the irradiance is low again.  Above the weather and atmosphere, the sun's irradiance follows a bell curve.

    Energy is power over a period of time.  Energy is what we use to get work done.  For instance, that one PV cell is probably putting out around 5 watts, and if it was in the sun for 2 hours in the middle of the day it would make 5 watts * 2 hours = 10WH, (or 10 watt-hours).

    Here is a link for charts showing the sun's average daily energy for different locations on the earth:  In general, the closer to the equator and the less clouds, the higher the energy at that location.

    Hope that helps,
    Kelly Larson
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