Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 21/06/2018 15:42:24
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Hello!
What is the optimum lux to maximise conversion of light into energy? What is the efficiency of this conversion?
Thanks!
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Light already is energy.
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maximise conversion of light into energy?
What sort of energy do you want to convert it into?
- If you want to convert it into light, an ordinary mirror will do that with over 50% efficiency (and an astronomical mirror will do it with over 99% efficiency)
- If you just want heat, any black surface will do. Covering it with a sheet of glass will reduce the amount of heat lost by convection and re-radiation.
- If you want electricity, cheap solar cells will give about 10% efficiency, while space-rated ones might give you over 20%. In this case, you have to allow air to circulate to keep them cool, as they lose electrical efficiency when they get hot.
- Commercially, both thermal and electric systems are optimised for sunlight, with about 700W per square meter
- In theory, they would both continue to work (a bit) under a full Moon, at about 0.01 Watts per square meter, so it would be a challenge to measure it!
See: http://forum.solar-electric.com/discussion/22560/full-moon-wattage
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Light already is energy.
Not very useful as electricity.
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Light already is energy.
Not very useful as electricity.
Light isn't energy. It has energy. Big difference.
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Light already is energy.
Not very useful as electricity.
Light isn't energy. It has energy. Big difference.
Well said.
But what about some figures for my question please?
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Light already is energy.
Not very useful as electricity.
True, but very handy if you want to see where you are going.
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Light already is energy.
Not very useful as electricity.
Light isn't energy.
Unless, of course, it is.
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev4.shtml
What do you think it is; chicken soup?
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Light already is energy.
Not very useful as electricity.
Light isn't energy.
Unless, of course, it is.
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev4.shtml
What do you think it is; chicken soup?
It's like saying electrons are energy, when in fact their movement is.
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Photons are defined in terms of energy, E = hf. Here h is Planck's constant and f is the frequency of light. Since frequency is variable then any equivalent mass that can be defined for the photon also changes. This cannot be defined as rest mass and therefore must depend entirely upon kinetic energy. In terms of objects with rest mass, kinetic energy is connected to a change in velocity and not to any change in frequency. The energy changes for entirely different reasons. This is like comparing apples and pears.
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The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unit area. It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity
So to answer the question: the more lux input to your converter, the more watts output. The optimum input is that which delivers the rated output.