The heating

ventilation

and air conditioning (HVAC) system accounts for a large portion of the total energy consumption of a building. When aiming to achieve energy efficiency

the vital factor is optimal operation of the chiller plants

which constitute a large percentage of the system energy consumption. In fact

chiller plants are often configured with multiple chillers

in order to meet the requirements for energy efficient operation of the HVAC systems of public buildings under partial loads. The chiller sequence control plays a significant role in satisfying the indoor load demand and facilitating energy-saving operation. In this paper

to improve the energy efficiency of the air-source heat pumps

an optimal sequencing control strategy is presented

taking an office building as an example. To develop this strategy

a variable-speed heat-pump model and the objective function for optimization of the heat-pump sequence control were first established

so as to determine the optimal solutions under partial building loads. Here

the variation of the actual capacity under different operation conditions was taken into consideration. In addition

the annual cooling and heating loads of the selected office building were analyzed using eQUEST software. It was found that loads greater than 70% of the peak loads occupy only 24% of the cooling time and 8% of the heating time. Finally

the optimal sequencing control strategy was contrasted with the traditional strategy based on the typical daily loads in the summer

winter

and transition seasons; the results indicate that the heat-pump energy consumptions are reduced by 14.5%

12.3%

and 3.3%

respectively. In addition

the energy consumption for the entire year was analyzed. The results show that the energy consumed by the heat pump is reduced by 14.1% during the cooling season and 9.0% during the heating season following adoption of the optimal sequencing control strategy. Thus

the optimal sequencing control strategy for the heat pump has a remarkable energy saving effect.