A single-story retail store wishes to supply all its lighting requirement with batteries charged by photovoltaic cells. The PV cells will be mounted on the horizontal rooftop. The time-averaged lighting requirement is 10 W/m2 , the annual average solar irradiance is 150 W/m2 , the PV efficiency is 10%, and the battery charging/discharging efficiency is 80%. What percentage of the roof area will the PV cells occupy

83.33% of the roof area will be occupied by the PV cells

Explanation:

Given the data in the question;

time-averaged lighting requirement = 10 W/m²

the annual average solar irradiance = 150 W/m²

the PV efficiency η = 10% = 0.1

battery charging/discharging efficiency η = 80% = 0.8

we know that; Annual average power to the light = × A

Now, the electrical power delivered by the solar cell battery system will be;

⇒   × A × η × η

A = × A × η × η

Such that;

A = A / × A × η × η

A / A = /   × η × η

so we substitute

A / A = 10 W/m² / [ 150 W/m² × 0.1 × 0.8 ]

A / A = 10 W/m² / 12 W/m²

A / A = 0.8333

A / A = (0.8333 × 100)%

A / A = 83.33%

Therefore, 83.33% of the roof area will be occupied by the PV cells.

c)as speed changes, wavelength and frequency change.

everything changes!

answer: b.

explanation: