Energy-Efficient Electrical Systems for Buildings 1st. Edition by Moncef Krarti | 9781482258332 | 1482258331 | Holooly

Basic Electrical

Energy-Efficient Electrical Systems for Buildings

90 SOLVED PROBLEMS

Question: 9.14

Calculate the cost savings in electric utility bills for an industrial customer serviced by the RTP rate used in Example 9.13 if the excess electrical load experienced during the curtailment hours (between 3 p.m. and 8 p.m.) is shifted uniformly to the next 4 h (between 8 p.m. and midnight). With ...

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(a) The excess load during the curtailment hours i...

Question: 8.7

Determine all the required sections of a unit substation for a radial distribution system shown in Figure 8.21. Then, size the electrical room assuming the unit substation is placed in the center of the room. ...

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Using the different steps outlined in the general ...

Question: 9.13

Calculate the utility bills for a customer serviced under two rates: (i) Conventional rate with the following charges: (a) Customer charge: $150.00 (b) Energy charge: $0.0264/kWh (c) Demand charge: $13.1/kW (ii) RTP rate structure with the hourly prices given in Table 9.11. In addition, a customer ...

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(i) First, the utility bill is determined using th...

Question: 10.2

Determine the reduction in the annual energy costs due to staggered duty cycling of three identical fan motors (each rated at 30 kW [40 HP]). The motor manufac turer specifies that a cycle has 20 min on and 10 min off as the minimum duty cycle. The utility monthly demand charge is $10/kW. First, ...

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(a) Using Table 10.2, the allowable number of star...

Question: 10.7

Determine if it is economically feasible to install number 10 (AWG) copper conductor instead of number 12 (AWG) on a 100 ft branch circuit that feeds a load of 16 A. Assume that • The load is used 10 h/day and 300 days/year • The cost of electricity is $0.10/kWh • The installed costs of No. 12 and ...

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In addition to the electric energy used to meet th...

Question: 10.6

Determine the cost-effectiveness of using a unit with an efficiency of 98.50% rather than 98.95% (NEMA Premium) for a 225 kVA rated transformer. Assume that • The cost of electricity is $0.12/kWh • The installed costs of 98.5% and 98.95% efficient transformers are $5950 and $7100, respectively • The ...

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To determine the cost-effectiveness of installing ...

Question: 10.5

Estimate the annual phantom load for a TV with a set-top box if the TV is operated 2 h/day. Determine the annual cost of the phantom load energy if the electricity cost is 0.10/kWh. ...

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Based on Table 10.6, the standby power for a TV is...

Question: 10.4

Consider an open office space with 150 m2 located in Denver, CO, with a total window area of 20 m2, with double-pane glazing, which has a visible transmittance of 0.55. The office space has 10 fluorescent fixtures, each rated at 52 W. Determine the energy use and cost savings due to daylighting ...

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Based on Equation 10.4, using the coefficients a =...

Question: 10.3

Consider a home with a total of 10 incandescent lamps rated at 60 W. Determine, the energy-saving potential if these lamps are replaced with (i) 13 W CFLs and (ii) 7 W LED lamps. The lifespan of the incandescent lamp, CFL, and LED lamp is, respectively, 1,300, 8,000, and 30,000 h. Perform the ...

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Incandescent lamps: Over the lifespan of

30...

Question: 10.1

Determine the cost-effectiveness of replacing a 10 HP motor with an efficiency of 85% with a premium-efficiency motor with a rated full-load efficiency of 91.70%. Assume that • The cost of electricity is $0.10/kWh • The differential cost of premium versus standard motor is $300 • The average load ...

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To determine the cost-effectiveness of installing ...

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