ME 4180 Energy Systems Homework Set 2 Fall 2024 PDF

Dr. Medina ME 4180 Energy Systems and Sustainability Homework Set #2 Fall 2024 Concept Questions 1. Explain which countries/regions expect the largest increase in energy demand in the 21st...

Dr. Medina ME 4180 Energy Systems and Sustainability Homework Set #2 Fall 2024 Concept Questions 1. Explain which countries/regions expect the largest increase in energy demand in the 21st century. What drives this demand? The region with the largest expected energy demand is Africa as a whole. In general, the demand is driven by population growth and the desire to industrialize. In the case of Africa, population growth will drive the demand. It was believed that the BRIC nations (Brazil, Russia, India, and China) were going to have the largest increase but now much of that increase is expected in Africa. 2. List all the end-use sectors in the U.S and the major energy carrier for that sector. Name an application that uses the listed energy carrier in each sector. End use sectors include residential, commercial, transportation, and industrial. The energy carriers for those sectors listed above (in the same order) are natural gas, either NG or coal in the form of electricity, petroleum, natural gas. An application for that energy carrier in that sector (in the same order) are homes, hospitals, vehicles, and metal processing plants. The answers come from slide 24 in Lecture 3 – Energy supply and demand. The most difficult one to figure out is commercial some math is required. Commercial receives 4.7 quad BTU from electricity and 3.57 quad BTU from NG. From electricity, coal delivers 12 quad BTU but a majority is lost. 3. Hydrogen’s heating value is ~3x higher than gasoline. Give 2 reasons why the combustion of hydrogen for the transportation sector has not been implemented on a global scale. there are many reasons why this hasn’t happened yet. Below are just four reasons I can think of from the top of my head. Although the heating value is higher, the volumetric energy density is a lot lower. Need to carry more volume If it’s in a gaseous state, needs to be pressurized and a heavy tank to maintain safety. There is no natural occurring source of hydrogen, so currently hydrogen gets produced from NG. Its more convenient to burn NG directly. Hydrogen only combustion is very fast and unstable and can be very dangerous, reaching high pressures and high temperatures. Also, suffers from high NOx emissions 4. List 3 reasons why the United States dependence on coal-fired power plants has decreased over the last 2 decades. Flue gas aftertreatment is expensive for coal bc it contains sulfur, nitrogen, and other contaminants NG produces less CO2 compared with coal  Dr. Medina Coal-fire power plants are old and exhibit poor efficiency. Need improvements and retro- fts that are more costly than a new NG power plant. NG gas fired-power plants are cheaper and faster to build Fracking has made NG much cheaper to extract compared with coal mining. Also coal mining is less safe. Other reasons might be accepted if they are different enough and can be justified. Renewables aren’t really the driver that has decreased our dependence, instead its natural gas. Numerical Questions 5. Regulators want to impose a carbon tax on a gallon of gasoline. If the carbon tax was set to $90 per ton of CO2, how much more would you pay for a gallon of gasoline? Assume gasoline is C8H18 with density of 740 kg/m3.  Dr. Medina 6. How long would you need to run on the treadmill to expend the energy consumed for the electronics listed below. (assume you burn 400kcal/hour 1)? Please also state how much energy is consumed (in kJ). a. 2 light bulbs: 2 hr @ 60W each b. Toaster: 5 minutes @ 1200 W c. Coffee maker: 20 minutes @ 900W d. Hairdryer: 5 minutes @ 1200W e. Vacuum cleaner: 45 mins @ 1.4 kW f. Microwave: 5 mins @ 2 kW g. Computer: 8 hours @ 200 W Note: This is a very conservative estimate of our energy use. We have not included refrigeration, heating or water use etc. here! 1 You may have noticed that on food packages or on a treadmill you rarely see numbers like 400x103 calories. A food calorie is actually 1000 calories or a kcal. Following conversions may also be useful: 1 Liter (L) = 0.001 m3; 1N = 1kg.m/s; 1 joule (J) = 1Nm; 1 Watt (W) = 1 J/sec ; 1 calorie = 4.184 joules.  Dr. Medina 7. Calculate the product gas composition for a butane and air combustion operating with an equivalence ratio of 0.9.