Question
Given a facilitys hourly chilled water (CHW) cooling load demand shown in the following spreadsheet, a combined chiller and stratified CHW thermal storage system is
Given a facilitys hourly chilled water (CHW) cooling load demand shown in the following spreadsheet, a combined chiller and stratified CHW thermal storage system is proposed to meet the demand while saving the cost (due to the time-of-use rate schedule). A full storage operating strategy (load shift) is employed in which the chiller is completely turned off for the 5-hour ON-PEAK rate period from 12pm to 4 pm (why 5 hours? It starts from 12pm to 5pm, i.e., from 12-1pm, 1-2pm, 2-3pm, 3-4pm, and 4-5pm.) with the cooling load solely provided by the CHW storage system. During the NON ON-PEAK period (5pm to 11am), the chiller will meet the instantaneous cooling load demand in addition to store thermal capacity.
Construct an Excel spreadsheet based on the one in the next page which illustrates the load shifting operating strategy and answer questions 1-10 on Blackboard.
Chiller EER (Energy Efficiency Ratio) = 7.6 (COP = EER / 3.412)
Electricity rates:
| Summer |
kWh of on-peak billing demand | $0.21/kWh |
kWh of off-peak billing demand | $ 0.17/kWh |
Time of day | Facility hourly CHW cooling load (tons) | Chiller + CHW storage system | |
Hourly chiller output (tons) | CHW storage charge inventory (ton-hours) | ||
12:00am | 1094 |
|
|
1:00am | 1015 |
|
|
2:00am | 950 |
|
|
3:00am | 979 |
|
|
4:00am | 969 |
|
|
5:00am | 968 |
|
|
6:00am | 1274 |
|
|
7:00am | 1367 |
|
|
8:00am | 1457 |
|
|
9:00am | 1773 |
|
|
10:00am | 2176 |
|
|
11:00am | 2518 |
|
|
12:00pm | 2668 | 0 |
|
1:00pm | 2831 | 0 |
|
2:00pm | 2900 | 0 |
|
3:00pm | 2900 | 0 |
|
4:00pm | 2784 | 0 |
|
5:00pm | 2598 |
|
|
6:00pm | 2348 |
|
|
7:00pm | 2077 |
|
|
8:00pm | 1935 |
|
|
9:00pm | 1836 |
|
|
10:00pm | 1711 |
|
|
11:00pm | 1302 |
|
|
Total |
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