| Summary: | 碩士 === 國立臺北科技大學 === 冷凍空調工程系所 === 103 === Even in subtropical Taiwan, temperature variation is considerable from summer to winter; and from mid-day to early morning. This has been the biggest problem to the designer in the planning and the specification of the air conditioning system. Commonly system capacity is designed to meet the maximum cooling load. Capacity control is designed to condition the space in order to achieve energy saving at the same time. Energy saving is now an issue of high importance, design with no energy saving has been discarded in most cases.
Of all variable air volume (VAV) is generally used, VAV air handling unit can save much energy by reducing supply volume at lower cooling load. Annual load characteristics of variable air volume system were collected and analyzed. Analysis was carried out for high and low efficiency fans, applied to variable frequency drive, pressure control and variable pitch systems. An actual building case was modelled using a dynamic building energy analysis program (eQUEST), so to obtain annual hourly building energy. A comparison was done with actual power consumption and using the corresponding annual weather data. The benefit of capital investment was evaluated. Pressure control was a less effective energy saving measure as pressure loss occurs in the air volume control. In contrast variable frequency and variable pitch control could reduce the air volume and pressure simultaneously, so that energy saving was quite significant. Variable frequency drive could maintain the same efficiency in the volume control and would be the best energy saving method.
Low cooling load constitutes about 70% in the air-conditioning operation period. A combination of frequency drive control and low efficiency fans were found to achieve significant energy saving, and were the second choice. Compare to the same fans, frequency control system saves 30% of fan energy than damper control. This effect is comparable to using high efficiency fan over low efficiency one of 35% energy saving.
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