Solar Energy Per Square Meter
Comments (0) physics question: about batteries?
an environmental monitoring station is battery powered. assume that one fresh LongLife 1.35 V cells stores 1.5 KJ of useable electrical energy before its output drops below an acceptable value. two such cells are connected in series to provide 2.7 volt. the monitoring station requires a current of 12 mA.
a) how many seconds will the batteries last, assuming no internal resistance?
to enable the station to run without maintenance, a solar electric panel is installed. data provided for the solar panel installation in that particular location indicates:
– 7% of the sun’s energy reaching the panel is converte to electricity
– in this location the mean solar energy per day onto 1 square meter (allowing for the season and typical weather patterns) is 12 MJ.
b) what total electrical energy is produced per day if the solar panel has effective photovoltaic area of .20 m x .25 m.
note; efficiency = energy output/total energy used
Power = voltage x amperage = violts x current = P = V I
Energy = Power x time of operation = E = P t
So time is t = E/(V I)
Now you have two batteries with a total of 3 kJ on energy, V = 2.7 V and I = 12 mA. Plufg into above to get time in seconds making sure you convert mA to Amps (1 mA = 10^-3 A)
Solar panel: Area = 0.2 x 0.25 m^2 = 0.05 m^2
Energy on solar panel = 12 MJ/m^2 * 0.05 m^2 = 0.6 MJ
Panel is 7% efficient so energy produced by panel = 0.07*0.6 MJ = 0.042 MJ = 42 kJ
Energy Revolution 2.0
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