The demand use pattern for a small industrial plant is given

The demand use pattern for a small industrial plant is given below. Assume the plant operates 6 days/week and the pattern is the same every day. Assume the billing period is exactly 4 weeks long. The utility rate is $0.08/kWh for energy and $12.00/kW for peak demand during the month. The monthly service charge is $35, the fuel cost adjustment factor is $0.0125/kWh, and there is no sales tax (manufacturing facility..sales tax exempt). There is no power factor penalty.

b. The plant can go on an optional time-of-day rate where energy used between 12:00 noon and 12:00 midnight is billed at an on-peak rate of $0.30/kWh and the energy used during the off-peak period is billed at $0.005/kWh. Any peak demands measured in the off-peak period are not counted on the billing. Calculate the new monthly bill using the off peak energy rate given here and the fuel and demand rates from part a.

c. The plant can shift all its current usage from 8 am to 5 pm EXCEPT 20 kW each hour to the off peak period. The 20 kW baseline is required 24 hours/day for lights, controls, HVAC, etc. If the plant shifts ALL the current usage above 20 kW from 8 am-5 pm to start at 12 midnight and end at 9 a.m., (on top of the existing load from 12 midnight-9 am) calculate the new monthly bill using the time of day rate in part b.

d. The plant has 8 employees who currently make $10/hour. 4 employees work 12 hours/day, 3 days per week (Mon/Tues/Wed) from 7:00 a.m. to 7:00 p.m. The other 4 employees work the same schedule but Thur/Fri/Sat. If the plant pays the employees $12.00/Hour to shift the work hours to the off-peak period so the new schedule is 12:00 midnight to 12 noon, is it feasible for plant management to consider moving the operation time of the plant? (In other words, show the difference in extra labor cost vs electrical savings).

e. If the additional 100 kW load operating between 3:00 and 4:00 p.m. was not time dependant and could be operated at any time during the day, it could be easier to shift its operating time to before 12:00 noon rather than shift the entire operation to night/early morning. Calculate the savings on the electric bill using the rate in part b if ONLY the additional 100 kW load operating from 3:00 to 4:00 p.m. was shifted to before 12 noon in the off peak period. (Remember, this savings includes both demand and energy)

f. In your opinion, which management option (part d or e) would be a “better” option to reduce the electric bill? Explain your answer.

Solution

monthly electrical bill if the above assumptions are used. 83 kW