Copy of Copy of lab 7
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Old Dominion University *
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108N
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Aerospace Engineering
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Dec 6, 2023
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docx
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1. [S points When peoples think about renewable (i.e., carbon-free) energy, solar energy (in one
way or another) is generally given high consideration. Why is that? In answering this question,
think about the total energy the Earth receives from the Sun and the total energy consumption
by humans based (primarily) on the use of fossil fuels (assume this latter value is 15 TW).
Because it gives fossil fuels a large, sustainable, and ecologically beneficial substitute while
simultaneously boosting the economy and ensuring energy security, solar energy is highly
valued. It's regarded as essential to solving climate change's problems and making the shift to a
more resilient and sustainable energy system.
2. [IS peiutsl Photevoltais (PV) cells represent one way of harvesting solar energy for our
energy needs. How much land would be needed to produce the 15 TW of required energy listed
in question 1 from photovoltaics, assuming that on average the Earth receives 238 W/m? of
solar energy (averaged as a function of latitude, and over the day/night cycle), and that a PV
cell has an efficiency of 12%. Express you answer in m? and as a percentage of all land area on
Earth (assume this value is 1.3 x 10"* m?). Does this amount of needed land suggest that PV
cells might be a reasonable source of carbon-free energy? In answering this question, you may
want i read ahead in your textbook (p. 184). How would your answer change if the efficiency of
photovoltaic cells increased?
approximately 0.0405% of the Earth's land area would be needed to produce 15 TW of energy
from photovoltaic cells. Several factors, such as land availability, economic viability, and
environmental considerations, will determine if this amount of land indicates that PV cells are a
suitable source of carbon-free electricity. The amount of land required to produce the same
quantity of electricity would decrease if solar cell efficiency increased.
3w/S points] Another way we can consider the viability of photovoltaic cells as an alternate
energy source is to ask the question about whether or not PV cells on the roof of a typical house
could meet the energy requirements of the household.
For this calculation assume that a typical household uses 6.3 kW of energy and that it has an
array of PV cells measuring 10 m by 10 m. Using the PV cell efficiency and solar flux values
given in the previous problem, first calculate how much energy a roof-top array of PV cells can
generate (express your answer in kW). What fraction of the total energy usage of a typical
household could be obtained from these solar cells?
2.856 kW / 6.3 kW ≈ 0.453 (approximately 45.3%)
a 10 m × 10 m rooftop PV cell array can produce about 2.856 kW of electricity. This amounts to
roughly 45.3% of the 6.3 kW of energy used by the average household.
4. [10 set
the length of the time series to 10 years and the trend to 0.20 C/decade. Click the
"update plot" button at least 20 times and write down (or enter into Excel) the observed values
of the trend that the model returns. Use these results to fill in the first column of the table
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