Conversion help?

Question

Solar (photovoltaic) cells convert sunlight directly into electricity. If solar cells were 100% efficient, they would generate about 1000 watts of power per square meter of surface area when exposed to direct sunlight. With lower efficiency, they generate proportionally less power. For example, 10% efficient cells generate 100 watts of power in direct sunlight. Suppose a 1-square-meter panel of solar cells has an efficiency of 90% and receives the equivalent of 12 hours of direct sunlight per day. How much energy, in joules, can it produce each day? What average power, in watts, does the panel produce? How much energy, in joules, can the solar panel produce each day? Give the value in millions of joules per day.

Answer 1

Hi Jacob,

 

An efficiency of 90% means that they can generate 90% of 1000 Watts of power per square meter of surface area, which is 900 Watts. Because the question asks for how much energy in a day, we convert Watts, which is Joules / seconds, to energy, which is Joules. Because the panel receives 12 hours in a day, we multiply by 12 hours:

 

900 Watts = 900 J / s * 12 hours * (3600 seconds / 1 hour)

 

38880000 J, or 38.88 MJ (Mega(M) = 10^6 = 1,000,000)

 

You repeated your question twice, but both answers have been given.

 

Hope this helps!