Energy Performance Analysis of an Integrated Distributed Variable-Frequency Pump and Water Storage System for District Cooling Systems

Abstract

Abstract:In a district cooling system (DCS), the distribution system (i.e., cooling water system or chilled water system) will continue to be a critical consideration because it substantially contributes to the total energy consumption. Thus, in this paper, a new distributed variable-frequency pump (DVFP) system with water storage (WS) for cooling water is adapted to a DCS with large end-use cooling load fluctuations. The basic principle and energy saving potential of the new system is analyzed. A case study of a DCS with a conventional central circulating pump (CCCP) system is presented to compare the energy consumption and the operating performance of CCCP and DVFP systems that are exposed to various weather conditions. The methods to perform this case study include, cooling load simulation and the modeling of two water distribution networks and systems via several commercial software packages. By replacing the throttling valves with a DVFP, the pump efficiency is increased and transportation energy consumption is reduced. Additionally, by introducing water tank storage, the cooling water is cooled at night and is released at a peak hour during the daytime, thereby further reducing the energy cost. As compared to the field test results of the CCCP system, the daily electrical energy saved by the DVFP and WS system is approximately 57% for a cooling water pump system on the hottest day in summer. This value also corresponds to approximately 10% of the energy saved for the entire system. Furthermore, additional energy could be saved under partial loading conditions.

An Occupant-Oriented Calculation Method of Building Interior Cooling Load Design

“…The installed rated power of lamps and equipment is decided by building design. So, the key factors of calculating interior load based on Equations (4) and (5) are the indoor occupant number and the corresponding used lamps and equipment. The problem has been transferred to the quantifying of indoor occupant number and establishing the relationship of used lamps and equipment number with indoor occupant number.…”

“…With the continuous improvement of building energy efficiency standards [3], the thermal performance of building envelopes has notably enhanced. Based on the demarcation of the building structure, three primary factors affect the energy consumption of the HVAC system: exterior disturbances, interior disturbances, and the operational factors of the energy supply system [4,5]. Exterior disturbances include outdoor air conditions and solar radiation.…”