TEST BANK FOR Energy Management 7th Edition International Version By Klaus Dieter E. Pawlik (Solutions Manual)

Exam (elaborations) TEST BANK FOR Energy Management 7th Edition International Version By Klaus Dieter E. Pawlik (Solutions Manual) Table of Contents Chapter 1: Introduction to Energy Management .................................. 1 Chapter 2: The Energy Audit Process: An Overview .................... .... 15 Chapter 3: Understanding Energy Bill .................................................. 21 Chapter 4: Economic Analysis and Life Cycle Costing ..................... 37 Chapter 5: Lighting ................................................................................... 53 Chapter 6: Heating, Ventilating, and Air Conditioning .................... 69 Chapter 7: Combustion Processes and the Use of Industrial Wastes ...................................................... 81 Chapter 8: Steam Generation and Distribution ................................... 93 Chapter 9: Control Systems and Computers ..................................... 101 Chapter 10: Maintenance ......................................................................... 109 Chapter 11: Insulation .............................................................................. 117 Chapter 12: Process Energy Management ............................................ 131 Chapter 13: Renewable Energy Sources and Water Management Supplemental ............................................... 139 1 Chapter 1 Introduction to Energy Management Problem: For your university or organization, list some energy management projects that might be good “first ones,” or early selections. Solution: Early projects should have a rapid payback, a high probability of success, and few negative consequences (increasing/ decreasing the air-conditioning/heat, or reducing lighting levels). Examples: Switching to a more efficient light source (especially in conditioned areas where one not only saves with the reduced power consumption of the lamps but also from reduced refrigeration or air-conditioning load). Repairing steam leaks. Small steam leaks become large leaks over time. Insulating hot fluid pipes and tanks. Install high efficiency motors. And many more 2 Solutions Manual for Guide to Energy Management, International Version Problem: Again for your university or organization, assume you are starting a program and are defining goals. What are some potential first-year goals? Solution: Goals should be tough but achievable, measurable, and specific. Examples: Total energy per unit of production will drop by 10 percent for the first six months and an additional 5 percent the second half of the year. Within 2 years all energy consumers of 5 million kilojoules per hour (kJ/h) or larger will be separately metered for monitoring purposes. Each plant in the division will have an active energy management program by the end of the first year. All plants will have contingency plans for gas curtailments of varying duration by the end of the first year. All boilers of 25,000 kg/h or larger will be examined for waste heat recovery potential the first year. Introduction to Energy Management 3 Problem: If you were a member of the upper level management in charge of implementing an energy management program at your university or organization, what actions would you take to reward participating individuals and to reinforce commitment to energy management? Solution: The following actions should be taken to reward individuals and reinforce commitment to energy management: Develop goals and a way of tracking their progress. Develop an energy accounting system with a performance measure such as kJ/m2 or kJ/unit. Assign energy costs to a cost center, profit center, an investment center or some other department that has an individual responsibility for cost or profit. Reward (with a monetary bonus) all employees who control cost or profit relative to the level of cost or profit. At the risk of being repetitive, note that the level of cost or profit should include energy costs. 4 Solutions Manual for Guide to Energy Management, International Version Problem: Perform the following energy conversions and calculations: a) A spherical balloon with a diameter of three meters is filled with natural gas. How much energy is contained in that quantity of natural gas? b) How many Joules are in 550 cubic metres of natural gas? How many GJ in 2,000 litres of #2 fuel oil? c) An oil tanker is carrying 3,000 litres of #2 fuel oil. If each litre of fuel oil will generate 3.3 kWh of electric energy in a power plant, how many kWh can be generated from the oil in the tanker? d) How much hard coal is required at a power plant with a heat rate of 10 MJ/kWh to run a 6 kW electric resistance heater constantly for 1 week (168 hours)? (One tonne of hard coal conttains 25 GJ of heat.) e) A large city has a population which is served by a single electric utility which burns hard coal to generate electrical energy. If there are 500,000 utility customers using an average of 12,000 kWh per year, how many tonnes of coal must be burned in the power plants if the heat rate is 10.5 MJ/kWh? (One tonne of hard coal contains 25 GJ of heat.) f) Consider an electric heater with a 4,500 watt heating element. Assuming that the water heater is 98% efficient, how long will it take to heat 200 litres of water from 20 degrees C to 60 degrees C? Introduction to Energy Management 5 Solution: a) V = 4/3 (PI) r3 = 4/3 × 3.14 × 1.53 = 14.13 m3 E = V × 38.14 MJ/m3 of natural gas = 14.13 m3 × 38.14 MJ/m3 = 539 MJ b) E = 550 m3 × 38.14 MJ/m3 of natural gas × 1,000,000 J/MJ = 2.10E+10 J E = 2,000 L × 39 MJ/L of #2 fuel oil × GJ/1,000 MJ = 78 GJ c) E = 3,000 L × 3.3 kWh/L = 9,000 kWh d) V = 10,000 MJ/kWh × 6 kW × (168 h/25 GJ/tonne hard coal) × (GJ/1,000 MJ) = 0.40 tonnes of coal e) V = 500,000 cus. × 12,000 kWh/cus. × 10.5 MJ/kWh × (1 tonne/25 GJ) × (GJ/1,000 MJ) = 2,520,000 tonnes of coal f) ΔQ = cmΔT = specific heat constant × mass × change in temperature = (4.186 kJ/kg/C) × 200 L × (0.001 m3/L) × (998 kg/m3) × (60 C – 20 C) = 33,421 kJ p = 4,500 W × 1 kW/1,000 W × 1 kJ/s/kW = 4.5 kJ/s t = ΔQ/p/efficiency = 33,421 kJ/(4.5 kJ/s) × (1h/3,600 s)/0.98 = 2.11 h 6 Solutions Manual for Guide to Energy Management, International Version Problem: A person takes a shower for ten minutes. The water flow rate is 12 litres per minute, the temperature of the shower water is 45 degrees C. Assuming that cold water is at 16 degrees C, and that hot water from a 70% efficient gas water heater is at 60 degrees C, how many cubic metres of natural gas does it take to provide the hot water for the shower? Solution: ΔQ = cmΔT eff = specific heat constant × mass × change in temperature = (4.186 kJ/kg/C) × 10 min × 12 L/min × (0.001 m3/L) × (998 kg/m3) × (45 C – 16 C)/0.7 = 20,769 kJ V = (20,769 kJ/38.14 MJ/m3) × MJ/1,000 kJ = 0.54 m3 of natural gas Introduction to Energy Management 7 Problem: An office building uses 1 million kWh of electric energy and 12,000 litres of #2 fuel oil per year. The building has 4,000 square metres of conditioned space. Determine the energy use index (EUI) and compare it to the average EUI of an office building. Solution: E(elect.) = 1,000,000 kWh/yr. × kJ/s/kW × 3,600 s/h = 3,600,000,000 kJ/yr. E(#2 fuel) = 12,000 L/yr. × 39 MJ/L × 1,000 kJ/MJ = 468,000,000 kJ/yr. E = 4,068,000,000 kJ/yr. EUI = 4,068,000,000 kJ/yr./4,000 m2 = 1,017,000 kJ/m2/yr. which is less than the average office building 8 Solutions Manual for Guide to Energy Management, International Version Problem: The office building in Problem 1.6 pays €65,000 a year for electric energy and €9,900 a year for fuel oil. Determine the energy cost index (ECI) for the building and compare it to the ECI for an average building. Solution: ECI = (€65,000 + €9,900)/4,000 m2 = €18.73/m2/yr. which is greater than the average building Introduction to Energy Management 9 Problem: As a new energy manager, you have been asked to predict the energy consumption for electricity for next month (February). Assuming consumption is dependent on units produced, that 1,000 units will be produced in February, and that the following data are representative, determine your estimate for February. ————————————————————— Units Consumption Average Given: Month produced (kWh) (kWh/unit) ————————————————————— January 600 600 1.00 February 1,500 1,200 0.80 March 1,000 800 0.80 April 800 1,000 1.25 May 2,000 1,100 0.55 June 100 700 7.00 Vacation month July 1,300 1,000 0.77 August 1,700 1,100 0.65 September 300 800 2.67 October 1,400 900 0.64 November 1,100 900 0.82 December 200 650 3.25 1-week shutdown January 1,900 1,200 0.63 Solution: First, since June and December have special circumstances, we ignore these months. We then run a regression to find the slope and intercept of the process model. We assume that with the exception of the vacation and the shutdown that nothing other then the number of units produced affects the energy used. Another method of solving this problem may assume that the weather and temperature changes also affect the energy use. 10 Solutions Manual for Guide to Energy Management, International Version ————————————————————————— Units Consumption Average Month produced (kWh) (kWh/unit) ————————————————————————— January 600 600 1.00 February 1,500 1,200 0.80 March 1,000 800 0.80 April 800 1,000 1.25 May 2,000 1,100 0.55 July 1,300 1,000 0.77 August 1,700 1,100 0.65 September 300 800 2.67 October 1,400 900 0.64 November 1,100 900 0.82 January 1,900 1,200 0.63 From the ANOVA table, we see that if this process is modeled linearly the equation describing this is as follows: kWh (1,000 units) = 623 + 0.28 × kWh/unit produced = 899 kWh 2,500 2,000 1,500 1,000 500 January Febuary March April May June July August September October November December Units produced Comsumption (kWh) Introduction to Energy Management 11 —————————————————————————————————— Coefficients Standard Error t Stat P-value Lower 95% Upper 95% Lower 95. 0% Upper 95.0% —————————————————————————————————— Intercept 623. 93. 6. 9.19E-05 411. 834. 411. 834. X Variable 1 0, 0. 3. 0. 0, 0. 0. 0. —————————————————————————————————— SUMMARY OUTPUT ———————————— Regression Statistics ———————————— Multiple R 0. R Square 0. Adjusted R Square 0. Standard Effort 118. Observations 11 ———————————— ANOVA —————————————————————————— df SS MS F Significance F —————————————————————————— Regression 1 .9788 .9 15.54545 0. Residual 9 ..07 Total 10 .5455 —————————————————————————— 500 1,000 1,500 2,000 2,500 • • • • • • • • • • • 1,400 1,200 1, Units Produced Energy Used (kWh) Scatter Plot 12 Solutions Manual for Guide to Energy Management, International Version Problem: For the same data as given in Problem 1.8, what is the fixed energy consumption (at zero production, how much energy is consumed and for what is that energy used)? Solution: By looking at the regression run for problem 1.8 (see ANOVA table), we can see the intercept for the process in question. This intercept is probably the best estimate of the fixed energy consumption: 623 kWh. This energy is probably used for space conditioning and security lights. Introduction to Energy Management 13 Problem: Determine the cost of fuel switching, assuming there were 1,000 cooling degree days (CDD) and 1,000 units produced in each year. Given: At the Gator Products Company, fuel switching caused an increase in electric consumption as follows: —————————————————————————— Actual energy Expected consumption energy after consumption switching fuel —————————————————————————— Electric/CDD 75 GJ 80 GJ —————————————————————————— Electric/units of production 100 GJ 115 GJ —————————————————————————— The base year cost of electricity is €30 per GJ, while this year’s cost is €35 per million GJ Solution: Cost variance = €35/GJ – €30/GJ = €5/GJ Increase cost due to cost variance = Cost variance × Total Actual Energy Use = (€5/GJ) × ((80 GJ/CDD) × (1,000 CDDs) + (115 GJ/unit) × (1,000 units)) = €975,000 CDD electric variance = 1,000 CDD × (80 – 75) GJ/CDD = 5,000 GJ Units electric variance = 1,000 units × (115 – 100) GJ/unit = 15,000 GJ Increase in energy use = CDD electric variance + Units electric variance = 5,000 GJ + 15,000 GJ = 20,000 GJ 14 Solutions Manual for Guide to Energy Management, International Version Increase cost due to increased energy use = Increase in energy use × Base cost of electricity = 20,000 GJ × €30/GJ = €600,000 Total cost of fuel switching = Increase cost due to increased energy use + Increased cost due to cost variance = €600,000 + €975,000 = €1,575,000 The Energy Audit Process: An Overview 15 15 Chapter 2 The Energy Audit Process: An Overview Problem: Compute the number of heating degree days (HDD) associated with the following weather data.