TU/ CODL

TEZPUR UNIVERSITY
SEMESTER END EXAMINATION (SPRING) 2020
DRE 203: ENERGY EFFICIENCY IN ELECTRICAL UTILITIES
Time: 3 Hours Total Marks: 70
The figures in the right-hand margin indicate marks for the
individual question.
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1. Select appropriate answer from the following:
10×1=10
a) If inlet and outlet water temperatures of a cooling tower are 40°C
and 33°C, respectively and atmospheric WBT is 30 °C then the
efficiency of the cooling tower is:
i. 70% ii. 72% iii. 75% iv. 77%
b) The maximum unbalanced load between phases should not exceed
…… % of the capacity of the DG set:
i. 2 ii. 10 iii. 8 iv. 10
c) The nearest kVA rating required for a DG set with 1000 kW
connected load, with diversity factor of 1.5 and 80% loading and
0.84 power factor is:
i. 1000 ii. 500 iii. 1500 iv. 2000
d) The required air conditioner size for comfort conditions for
general
living room (12' × 12') at residence is:
i. < 0.5 TR ii. 1.25 – 1.5 TR iii. 2 – 2.5 TR iv. >2.5TR
e) A modern electronic starter is used in motor to:
i. achieve variable speed ii. provide smooth start and
stop
iii. improve the loading iv. none of the above
f) Luminous efficacy of which of the following lamps is the highest?
i. HPMV ii. HPSV iii. LPSV iv. CFL
g) A device that distributes and filters the light emitted from one or
more lamps is:
i. Control gear ii. Lamp iii. Luminaire iv. Starter
 P.T.O. 8. A 3 phase, 415 V, 100 kW induction motor is drawing 50 kW at a 0.75
PF. Calculate the capacitor rating requirements at motor terminals for
improving PF to 0.95. Also, calculate the reduction in current drawn
and kVA reduction, from the point of installation back to the
generating
h) The volumetric efficiency of the compressor ______ with the increase
side due to the improved PF. What is the percentage reduction in
in
distribution losses per month if PF is improved up to 0.95 at load end?
altitude of place:
4+4+2=10
i. increases ii. decreases
iii. remains constant iv. may increase/decrease
9. Explain the possibility of implementing waste heat recovery for the
I) The compression ratio in diesel engines is in the range of following DG Set:
i. 14:1 to 25:1 ii. 10:1 to 13:1 7
iii. 5:1 to 10:1 iv. 10:1 to 15:1 Outputs:
j) The input power to an 18 kW, 415 V, 4 pole, 50 Hz, 3 phase squirrel Electrical output: 38%
cage Stack loss through flue gas: 30%
induction motor with a full load efficiency of 92% and power factor of Coolant losses: 20%
0.90 is: Alternator losses: 4%
i. 18 kW ii. 16.5 kW Radiation losses: 8%
iii. 16.2 kW iv. 20 kW
10. What is the significance of back pressure in the flue gas path while
2. How does the power factor of an induction motor improve with the recovering waste heat in a DG set? 3
increase in the applied load on the motor? 5
3. How does a Vapour Adsorption System work? What is the main ***
difference between Vapour Compression and Vapour Absorption
Refrigeration systems? 5+5=10
4. List the energy conservation opportunities in a cooling tower system.
10
5. List down five important parameters that influence the selection of an
induction motor. 5

6. Explain different components of tariff structure in the electricity

7. Calculate the annual energy savings and simple payback from