Two-layer energy optimization of HVAC system in a cement factory building

Based on the building thermodynamics model and the physical heat/cold conversion model of an air-conditioning system, this paper proposes a double-layer energy optimization model for a cement factory’s office building air-conditioning systems considering dynamic ambient temperature and the entire unit equipment. First, taking the envelope structure, outdoor air, and internal heat sources as the main subjects and considering the heat exchange between human skin and the envelope structure, a building thermal balance model and a refined calculation model of comfort were established. Secondly, the ground source heat pump is considered. A physical model of the operation of the air-conditioning system is set for the equipment, such as heat pumps, circulating water pumps, and variable frequency fans. Then, a two-layer comprehensive optimization model of the cement factory office building air-conditioning system was given based on system power consumption and comfort. The upper model dynamically adjusts the indoor set temperature to obtain the cooling load of the air-conditioning system; the lower model allocates the load rate based on the heat pump unit's performance to optimize the system's overall energy consumption. Finally, a typical case of a double-story model of a cement factory office building using the GA algorithm was compared and verified, showing the effectiveness of the proposed model.