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Ch.7 - Thermochemistry
Chapter 7, Problem 96

In a sunny location, sunlight has a power density of about 1 kW/m2. Photovoltaic solar cells can convert this power into electricity with 15% efficiency. If a typical home uses 385 kWh of electricity per month, how many square meters of solar cells are required to meet its energy requirements? Assume that electricity can be generated from the sunlight for 8 hours per day.

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1
Calculate the total energy consumption of the home in kilowatt-hours (kWh) per day by dividing the monthly consumption by the number of days in a month.
Convert the daily energy consumption from kilowatt-hours to kilowatts by dividing by the number of hours in a day that the solar cells can generate electricity.
Determine the amount of power that needs to be generated by the solar cells by dividing the required power by the efficiency of the solar cells (15%).
Calculate the area of solar cells needed by dividing the required power by the power density of sunlight (1 kW/m^2).
Ensure the units are consistent and check the calculations to verify the area of solar cells required.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Power Density

Power density refers to the amount of power (energy per unit time) received per unit area, typically measured in watts per square meter (W/m²). In this context, a power density of 1 kW/m² indicates that each square meter of solar panel can receive 1 kilowatt of solar energy under optimal conditions. Understanding power density is crucial for calculating the total energy available from sunlight for solar energy applications.
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Efficiency of Solar Cells

The efficiency of solar cells is the ratio of the electrical output to the solar energy input, expressed as a percentage. In this case, a 15% efficiency means that only 15% of the solar energy hitting the solar cells is converted into usable electricity. This concept is vital for determining how much solar panel area is needed to generate a specific amount of electricity, as higher efficiency results in less area required.
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Energy Consumption and Conversion

Energy consumption refers to the total amount of energy used by a household, measured in kilowatt-hours (kWh). To meet the energy needs of a home using 385 kWh per month, one must convert this monthly requirement into a daily average and then into the equivalent solar energy needed, factoring in the hours of sunlight available. This conversion is essential for calculating the area of solar cells required to meet the household's energy demands.
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