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 you want to supply 1 kilowattnothing of power to a house by putting solar panels on its roof. For solar cells with the average power of 41 watts per square meter of solar panels, how many square meters of solar panels would you need? Assume you can make use of the average power from the solar cells (by, for example, storing energy in batteries until it is needed)?

Solar cells can transform solar energy into electric energy. In a sunny day, the average power the sun incides on earth is approximately 1,000 watts (heat). if we had a 100% efficient solar cell, it would mean that the total amount of sunlight energy would be transformed into electrical energy, i.e. 1,000 watts of power. Its efficiency could be 1000 watts(solar cells)/1000(sunlight)x100(to express it in percentage).

Since the solar cells that will be mounted in the roof will produce 41 watts per square meter, its efficiency is calculated by dividing 41 /1,000x100. This gives us an efficiency of 4.1%. In order to generate 1,000 watts of power, we will need to use a simple rule-of-three, described like the following:

if 41 watts are produced by the solar cells in 1 square meter, how many square meters will be needed to produce 1,000 watts?

i.e. 41 watts ----------- 1 sq meter

1,000 watts ------------ x

[tex]x= (1000 watts)1 sq.meter/41 watts\\\\x= 24.39 square meters[/tex]

Finally, we can assume that the solar cell system will produce this amount of energy constantly during a full day cycle (using solar cells at day and batteries at night).