Exam 1 2009 - Name Z 1/3 ECE 398RES Exam#1 Tuesday March 3...

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Unformatted text preview: Name: Z 1/3 ECE 398RES Exam #1 Tuesday, March 3, 2009 Closed book, closed notes One note sheet allowed 1. /20 2. /lS 3. /20 4. /15 5. /30 Total ____/ 100 1. (20 points total) A new coal-fired power plant with a heat rate of 10,000 Btu/kWh burns coal with an energy content of 24,000 kJ/kg. The coal content includes 62% carbon, 2% sulfer and 10% unbumable minerals called ash. Ifneeded, the last page has some usefiil constants. a. What is the carbon emissions rate? Express your answer in kg carbon per kwh. b. What will be the uncontrolled sulfur emission rate? Express your answer in g (grams) sulfer per kwh. c. If 70% of the ash is released as particulate matter from the stack (called fly ash), what would be the uncontrolled particulate emission rate? Express you answer in g per kwh. C4) [04300 Btu («038’ kJ' ~— kw‘h 2. (15 points total) Assume you have a Capstone 65 kW microturbine that burns 760,500 Btu/hr when running at full output, and that when running the microturbine there are no other costs. You can assume the cost of natural gas for the turbine is $6 per million Btu OMbtu). a. What is the cost of electricity from this tubine in $/MWh? b. If electricity from the local utility costs 8 cents per kWh, what would be the yearly savings from using this microturbine assuming the electric load is fixed at 65 kW for the entire year? Express your answer in $/year. c. Calculate the simple payback period in years (i.e., assuming no interest costs) if the initial investment for the microturbine is $100,000 and there are no other costs or savings. The waste heat from the microturbine is not used. 0‘5 031.403 Mal/lair» iiG/mHU ° DES MWL lat" :: “MA/la l ‘03 310,08 «- 360708 a) GQV~3L2$ u (of; : iS’SKO/UW <93 Vii/000m : i739; "rs tests/W j 3. (15 points total) Suppose 300 gpm (gallons per minute) of water is taken from a small river and delivered through 600 it of 4 inch diameter PVC pipe to a turbine 200 fi lower than the source. You may assume the frictional head loss for this flow and pipe size is 4.4 ft per 100 ft of pipe. Assume the turbine/generator has an efficiency of 50%. Potentially useful constants are provided on the last page of the exam. a. How much electric power (in kW) would be supplied by this system? b. Assuming the system operated at filll capacity for one year, how much energy (in MWh) would be supplied during the year? m P = @qu Q: am 8’3 1+: 3-00 \ (mutt : mes TOE, , w. P :1 33¢: *3 [73’ (pg 0.8‘ . - $13 ‘-‘ w (7“ Cl1 kW 13‘) ll; 0 Watt/lg 4 (20 points total). A single phase motor with a power factor of 0.7 draws 6 kW of real power at 240 V from an ideal transformer with a high side voltage of 2400 V. a. How much reactive power is consumed by the motor? b. What is the magnitude of current in amps on the high side of the transformer? c. How many kvars of capacitors need to be connected across the motor to correct its power factor to 0.95 lagging? You may assume the additional capacitors do not change the motor’s voltage. 5 (30 points total). True/False - Three points each. Circle T if statement is true, F if statement is False. 10. As discussed in class, a usefiil rule-of—thumb is one pound of coal produces enough electricity to light 100 W bulb for one hour The hydro plant with the most capacity in the world (currently) is located at Itaipu falls on the Brazil/Paraguay border. In the M80 electric market the locational marginal costs (LMPs), expressed in $/MWh, are sometimes negative. In a transformer the core losses due to eddy currents can be reduced by laminating the core. Referring to harmonics, if an electric current has half-wave symmetry then there will be no even harmonics. Because of the rapid, recent growth in wind energy, the United States now gets more energy from wind than from nuclear. The maximum possible efficiency of a heat engine with a Tc of 50°C and a T5 of 250°C is 80%. A Sterling engine uses external combustion in which energy is supplied to the working fluid from a source outside the engine. Because of their relatively high elficiency, the capacity factor for a solar PV installation is usually more than 50% A basic steam power plant uses a Rankine cycle because the working fluid (water) changes between gas and liquid. Useful Constants One cubic foot = 7.4805 gallons 0.02832 m3 One foot per second = 0.6818 mph 0.3048 m/s Water density = 652.428 lb/fi3 1000 kg/m’ 1 kW = 737.56 fi—lb/s 1000 N-m/s Gravity = 32.2 fi/sec2 9.81 m/s2 One BTU = 777.9 ft—lb 1055 J One Meter = 39.37 inch K = °C+273. 15 You may assume the atomic weight of carbon is 12, and oxygen is 16. ...
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