cooling load and use reheat coil in zone B to reheat the air up. Thus, simultaneous cooling and heating happens all the time in MRQ building. And this is a waste of energy. However, VAV is more energy efficient since it supplies variable volume of air with constant outlet temperature. So variable cooling load could be achieved by variable air volume supply. Therefore, reheat process is not necessary for VAV system, which saved a lot of energy. Regarding the slight increase of the heating energy consumption of VAV building case comparing to CAV building case, reheat coil could save energy by controlling temperature in individual thermal zones by not varying too much in supply air temperature in central air duct. And CAV system purely heats the building in winter while simultaneous cools and heats the building in summer. Thus, the energy is not wasted in heating for the CAV building case. So the heating consumption for CAV and VAV are similar. But VAV heating consumption should be smaller than CAV system, this is not normal. Further investigation is necessary for this case. The monthly energy consumption results are shown in Figures 35, 36, 37 and 38.
Figure 80 Monthly end use trend for Proposed CAV Model
Figure 81 Monthly end use trend for Proposed VAV Model
In Figure 35, the pump energy also increased from May to September because operation of chiller requires water circulation in the water loop.
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