A U.S. Department of Energy report estimates that over 122 billion kWh/year can
ID: 2085822 • Letter: A
Question
A U.S. Department of Energy report estimates that over 122 billion kWh/year can be saved in the manufacturing sector in the United States by using mature and cost-effective conservation technologies. Calculate (a) how many 1000 MW generating plants are needed to operate constantly to supply this wasted energy and (b) the annual savings in dollars if the cost of electricity is 0.10 $/kWh. Electricity generation in the U.S. in year 2000 was approximately 3.8 times 10 MW hrs, 16 percent of which is used for heating, ventilating and air conditioning. Based on a DOE report, as much as 30 percent of the energy can be saved in such systems by using adjustable speed drives. On this basis, calculate the savings in energy per year and relate that to 1000 MW generating plants needed to operate constantly to supply this wasted energy.Explanation / Answer
Answer:-3.16) 122 billion kWh / year means:- (122 x 109 x 103 ) / (365 x 24) Watt = 1.3926 x1010 Watt.
a) 1000 MW plants produce 1000 x 106 Watt = 109 Watt, hence number of plants required is-
= (1.3926 x 1010) / (109)
= 13.9 or we can say it is 14.
b) Annual saving in dollar = 122 x 109 x 0.10 = $12.22 billion.
Answer:-3.17) Per year production = 3.8 x 109 MW-hr.
16 % of this is used in heating, ventilating and air-conditioning i.e. 0.16 x 3.8 x 109 MW = 6.08 x 108 MW-hr/year
30 % of this can be saved using adjustable speed drives, saved energy = 0.3 x 6.08 x 108 MW = 1.824 x 107 MW-hr/yr
Number of 1000MW plants required = (1.824 x 107 ) / (1000 x 24 ) = 760 plants. (Divide by 24 hr to convert one day energy(MW-hr) into power(MW) ).
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