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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

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3 votes

Answer:

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

Step-by-step explanation:

Given the data in the question;

time-averaged lighting requirement
P_{lighting = 10 W/m²

the annual average solar irradiance
q_{solar = 150 W/m²

the PV efficiency η
_{pv = 10% = 0.1

battery charging/discharging efficiency η
_{battery = 80% = 0.8

we know that; Annual average power to the light =
P_{lighting × A
_{roof

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


q_{solar × A
_{pv × η
_{pv × η
_{battery


P_{lightingA
_{roof =
q_{solar × A
_{pv × η
_{pv × η
_{battery

Such that;

A
_{pv =
P_{lightingA
_{roof /
q_{solar × A
_{pv × η
_{pv × η
_{battery

A
_{pv / A
_{roof =
P_{lighting /
q_{solar × η
_{pv × η
_{battery

so we substitute

A
_{pv / A
_{roof = 10 W/m² / [ 150 W/m² × 0.1 × 0.8 ]

A
_{pv / A
_{roof = 10 W/m² / 12 W/m²

A
_{pv / A
_{roof = 0.8333

A
_{pv / A
_{roof = (0.8333 × 100)%

A
_{pv / A
_{roof = 83.33%

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

User ZOqvxf
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