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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 coalﬁred 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+: 300 \ (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 ruleof—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 halfwave
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 Nm/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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