The site energy and primary energy

by | Nov 5, 2021 | Physics

  1. In Solution Box 6.1, the site energy and primary energy using a gas furnace versus a straight
    electric resistance heater were compared for a home.
    a. Compare the carbon emissions for these two houses assuming natural gas emits 5 kg CO2 per
    therm (100,000 Btu) and a coal-fired power plant that emits 1 kg CO2 per kWh that it
    delivers.

b. Now, consider replacing the ordinary resistance heater with an efficient heat-pump heater
that delivers 12,000 Btu of heat per kWh of input electric power (e.g. Section 6.12). Now
compare the CO2 emissions for gas heater with a new heat-pump space heater.
c. Now, reconsider the source of electricity for the heat pump space heater. Replacing the old
coal-fired power plant with a new combined-cycle, natural-gas-fired power plant (e.g.
Section 9.5.4), carbon emissions drop to around 0.4 kg CO2/kWh. Now compare the carbon
emissions for the gas furnace versus the heat-pump space heater.

  1. In Solution Box 6.5, the R-value of a conventional 2×4 wall with a 15% framing factor and R-11
    fiberglass insulation between the studs was determined to be 11.4. Suppose that wall did
    not have any insulation between the studs resulting in an air gap that itself has an R-value of
    1.0. Find the overall R-value of this un-insulated wall.
  2. Suppose a blower door test on a 2000 ft2 house with 8-ft ceilings required 2400 cfm of airflow
    to create a 50 Pa pressure difference.
    a. Estimate the average annual infiltration rate n(ach) using the rule-of-thumb given in Eq.
    6.17.
    b. Estimate the equivalent (UA)-value (Btu/hroF) for the infiltration rate.
    c. What is the annual Btu/yr that must be supplied by the heating system if this house is in a
    region characterized by HDD65 = 4000 degree days.
    d. With a 75% efficient heating system and natural gas costing $1.30/therm, what is the annual
    cost of fuel to heat this house due to this infiltration?
    Chapter 7
  3. Consider the decision about whether to purchase a fiberglass insulating jacket to put around
    your home water heater. When you touch the metal on the outside of the water heater it
    seems pretty cool, so you are not convinced that it needs more insulation.
    Suppose the exterior metal surface of the water heater is 75oF while the room that it is in is

70oF. The water inside the tank is 130oF. Using a convective resistance from outer-metaljacket-to-air of 0.68 hr-ft2

oF/Btu:
a. Estimate the overall R-value (from water to room air) of this water heater. Equation 6.7
will help.
b. Under the above conditions, how long would it take (in days) before a 22-ft2
, $10 water
heater insulating blanket would pay for itself if it adds R-7 to the tank. Assume it is a 70%
efficient gas water heater, with gas costing $1.30/therm (1 therm = 100,000 Btu).

  1. Those very handy sun-path diagrams, such as the one shown below, can be downloaded
    from the University of Oregon’s website:
    http://solardat.uoregon.edu/PolarSunChartProgram.html.

a. For the above sun-path diagram, use your knowledge of solar angles at noon to figure out
the latitude for which it has been drawn.
b. Download the sun path diagram for the equator… pretty strange, eh?
c. Can you imagine what the sun path diagram looks like at the north pole? Download it and
see whether you figured it out correctly.

  1. Create the following spreadsheet for a “Suntempered” house. Notice that the south-facing
    windows have been treated as if they are not even there (thermally neutral). The annual
    fuel bill is estimated to be $897/yr.

After replicating the spreadsheet, suppose a neighbor builds a new structure that
completely shades those south-facing windows. What would your spreadsheet predict as
the new annual fuel bill for heating? How much has that shading cost the original “suntempered” homeowner ($/yr)?

  1. Suppose you have enough space on your roof to fit 50 m2of 19%-efficient
    photovoltaics. Your PVs are “premium” 19%-efficient modules, which face due south with a
    tilt angle of 25o
    .
    a. How many kW (rated under Standard Test Conditions) of PV modules can you fit onto that
    roof area?
    b. Suppose your house is in Reno, Nevada. Using PVWatts, how many kWh/yr would you
    expect this array to produce? (be sure to select “premium” (19% eff) for your modules).
    c. Suppose you will be using some of that PV electricity to supply a modest 60 gallons/day of
    water heated from 60oF to 120oF using a heat pump with a 3.25 efficiency-factor (Table 7.4).
    How much of your PV area would be needed to meet that need?
    d. What would be the rated power (kW) of the PVs needed for that hot water?
    Chapter 8
  2. Update progress of LED performance and cost compared to DOE goals described in
    Figure 8.7.
  3. A “Home Energy Analysis” spreadsheet is given below.
    a. Construct your own spreadsheet.
    b. Run the spreadsheet with the following cases, providing answers for total
    gasoline, natural gas, and electricity use and costs, total energy cost and total CO2
    emissions in the log sheet. Please highlight the changes in results in bold or by
    highlighting or circling on spreadsheet.
    i. Default values, current prices: $1.10/therm; $0.12/kWh; $2.75/gal gasoline
    ii. High efficiency case with current prices: House with thermal index of 3.5,
    automobiles @ 50 mpg and 11000 miles, and the following efficiency measures:
     high efficiency gas furnace (96%)
     high efficiency water heater (0.75)
     efficient refrigerator (400 kwh/yr), efficient dishwasher (200 kWh/yr),
    washing machine (250 kWh/yr), and related clothes drying efficiency (900
    kWh/yr)
     LED lamps (replace indoor 2 100W with 2 12W and 5 60W with 5 9W, all
    on 5 hours/da; replace outdoor 3 75W with 3 11W, all on 6 hours/da),
     efficient room air conditioner (300 kWh/yr)
     add ceiling fan: (50 w, 4 hr/da),
    iii. High energy price case: Original situation but with a gas price of $1.75 per
    therm, electricity price of 16 cents per kWh, and gasoline price of $3.75 per
    gallon.
    iv. High efficiency case (ii) with high energy prices (iii)
    HOME ENERGY ANALYSIS (Entries with * are calculated)
    (everything else is data entry)
    HOME HEATING:
    Floor Area: 2000 square feet
    Thermal Index 8 Btu/ft2-degree-day (24 x UAtot / floor area)
    Degree Days: 5000 degree-days/yr
    Furnace Efficiency: 0.65
    Natrl Gas price: 1.25 $/therm (1 therm = 100,000 Btu)
    Heating Energy Use: * 1231 therms/yr (area x thermal index x DegDays/furn eff)
    Heating Energy Cost: * 1538 $/yr
    CO2 coefficient – NG 11.7 lb/therm
    COOKING:
    Gas Stove 8 therm/mo
    Cooking Energy cost: * 120 $/yr
    WATER HEATING:
    Hot Water use: 80 gal/day (at 20gal/person/da and 4 person)
    Heater efficiency: 0.6
    HW Energy to heat: * 23.352 therms/mo (assume 30da/mo, 70oF temp rise)
    energy = (gal/d x 30d/mo x 8.34lb/g x 1Btu/lbF x 70F)/(eff x 100000Btu/th)
    HW Energy Cost: * 350.28 $/yr
    ELECTRICITY: Watts Hrs/day: kWh/mo * $/mo *
    Refrigerator: 500 120 12.00
    Color TV: 250 5 38 3.75
    Stereo: 60 6 11 1.08
    Computer: 120 5 18 1.80
    Lights: indoors 500 5 75 7.50
    Lights: outdoors 225 12 81 8.10
    Washing machine: 500 1 15 1.50
    Clothes Dryer 2000 120 12.00
    Room air cond.: 1400 2 84 8.40
    Furnace fan: 280 4 34 3.36
    Clocks, nite lites: 40 24 29 2.88
    Dishwasher: 1300 1.5 59 5.85
    Microwave oven: 1500 0.5 23 2.25
    Toaster: 1200 0.2 7 0.72
    Vacuum cleaner: 600 0.2 4 0.36
    TOTAL* 715.5 71.55 (assume 30 days/mo)
    Electricity price: 10 cents/kWh
    CO2 coefficient – Elect 2 lb/kWh AEP rate
    AUTOMOBILES 18000 miles, @ 20 mpg, and 2.5 $/gal
    TOTAL GASOLINE * 900 gallons 2250 $/yr 17640 lb CO2
    CO2 coefficient – gasoline 19.6 lb/gal
    TOTAL NATL GAS * 1607 therms/yr 2009 $/yr 18802 lb CO2
    TOTAL ELECTRIC * 8586 kWh/yr 859 $/yr 17172 lb CO2
    TOTAL ENERGY * 5117 $/yr 53614 lb CO2

Sample Solution

Sample solution

Dante Alighieri played a critical role in the literature world through his poem Divine Comedy that was written in the 14th century. The poem contains Inferno, Purgatorio, and Paradiso. The Inferno is a description of the nine circles of torment that are found on the earth. It depicts the realms of the people that have gone against the spiritual values and who, instead, have chosen bestial appetite, violence, or fraud and malice. The nine circles of hell are limbo, lust, gluttony, greed and wrath. Others are heresy, violence, fraud, and treachery. The purpose of this paper is to examine the Dante’s Inferno in the perspective of its portrayal of God’s image and the justification of hell. 

In this epic poem, God is portrayed as a super being guilty of multiple weaknesses including being egotistic, unjust, and hypocritical. Dante, in this poem, depicts God as being more human than divine by challenging God’s omnipotence. Additionally, the manner in which Dante describes Hell is in full contradiction to the morals of God as written in the Bible. When god arranges Hell to flatter Himself, He commits egotism, a sin that is common among human beings (Cheney, 2016). The weakness is depicted in Limbo and on the Gate of Hell where, for instance, God sends those who do not worship Him to Hell. This implies that failure to worship Him is a sin.


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God is also depicted as lacking justice in His actions thus removing the godly image. The injustice is portrayed by the manner in which the sodomites and opportunists are treated. The opportunists are subjected to banner chasing in their lives after death followed by being stung by insects and maggots. They are known to having done neither good nor bad during their lifetimes and, therefore, justice could have demanded that they be granted a neutral punishment having lived a neutral life. The sodomites are also punished unfairly by God when Brunetto Lattini is condemned to hell despite being a good leader (Babor, T. F., McGovern, T., & Robaina, K. (2017). While he commited sodomy, God chooses to ignore all the other good deeds that Brunetto did.

Finally, God is also portrayed as being hypocritical in His actions, a sin that further diminishes His godliness and makes Him more human. A case in point is when God condemns the sin of egotism and goes ahead to commit it repeatedly. Proverbs 29:23 states that “arrogance will bring your downfall, but if you are humble, you will be respected.” When Slattery condemns Dante’s human state as being weak, doubtful, and limited, he is proving God’s hypocrisy because He is also human (Verdicchio, 2015). The actions of God in Hell as portrayed by Dante are inconsistent with the Biblical literature. Both Dante and God are prone to making mistakes, something common among human beings thus making God more human.

To wrap it up, Dante portrays God is more human since He commits the same sins that humans commit: egotism, hypocrisy, and injustice. Hell is justified as being a destination for victims of the mistakes committed by God. The Hell is presented as being a totally different place as compared to what is written about it in the Bible. As a result, reading through the text gives an image of God who is prone to the very mistakes common to humans thus ripping Him off His lofty status of divine and, instead, making Him a mere human. Whether or not Dante did it intentionally is subject to debate but one thing is clear in the poem: the misconstrued notion of God is revealed to future generations.

 

References

Babor, T. F., McGovern, T., & Robaina, K. (2017). Dante’s inferno: Seven deadly sins in scientific publishing and how to avoid them. Addiction Science: A Guide for the Perplexed, 267.

Cheney, L. D. G. (2016). Illustrations for Dante’s Inferno: A Comparative Study of Sandro Botticelli, Giovanni Stradano, and Federico Zuccaro. Cultural and Religious Studies, 4(8), 487.

Verdicchio, M. (2015). Irony and Desire in Dante’s” Inferno” 27. Italica, 285-297.

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