PV Gap

Ross Said:

How to calculate efficiency?

We Answered:

40 is wasted. 60 is useful so 60/100 = 60% :)

Vernon Said:

How much energy, in kilowatt hours per year, would one square foot of solar cells produce?

We Answered:

It would be best to look at real historical data from the nrel maps: http://rredc.nrel.gov/solar/old_data/nsr…

According to those, Rapid City gets 5 equivalent peak sun-hours per day, averaged over the year. That's because even though the sun may be up for 12 hours in a given day, the morning and evening sun is weak, only a fraction of the noonday sun. This data also takes into account overcast days and seasons.

5 hours per day means about 1800 hours per year (I used 360 days as a crude estimate). It is reasonable to expect 12 watts per square foot of panels, maybe even 15 watts from the best ones made.

12 watts x 1800 hours = 21600 wh = 21.6 kWh per square foot.

That assumes the panels are stationary, but ideally oriented.

Cory Said:

calculating efficiency?

We Answered:

1) What is the overall efficiency of the transfer of light energy from the Sun to electrical energy? 15%

2) each square metre of the solar panel recieves 500 w. the area of the panel is 5cm^2. how much energy falls on the panel in 2 hours?
500W per m². on 5cm² energy received = 500*5/100² = 0.25W
Energy = power * time
Energy = 0.25W * 2*60*60 = 1,800J

3) another panel of solar calls has the efficiency of only 6% what is the electrical output of this panel when the input power is 2500w?
6/100*2500 = 150W