Comprehensive and quantitative evaluation for selecting a suitable scheme of central air-conditioning during the design phase

Abstract

As for routinely selecting the number and size of chillers in central air-conditioning system, the conventional scheme in which the total cooling capacity is allocated in an equal or empirical way is generally suboptimal. A few factors are brought into consideration, and the time domain of evaluation is too short. The low suitability between the cooling load of building and the scheme selected results in an inefficient state of system during the most of operation time. Some novel methods provide long-term evaluations for selecting an efficient scheme by simulating the cooling loads then calculating the cost and performance of the scheme. However, the schemes are formed without correlating actual plants which is difficult to be applied to an actual project, and the long-term environmental impact is rarely considered. The evaluation method with a high engineering value is required. But the more complicated the method is, the more work is required. The relationship between the benefits and the costs is unknown. Therefore, this study proposes three evaluation methods at different levels. From simple to complex, the three methods are corresponding the cooling load curve of building calculated through EnergyPlus to the performance curves of chillers, system simulation using TRNSYS and co-simulation based on BCVTB respectively. A case study using a hospital building located in Zhejiang province, China combined with equipment list was conducted to demonstrate the evaluation process. The results calculated by different methods and the various indexes of different schemes were compared to illustrate how to optimize the scheme selection during the design phase in order to select a suitable scheme for a certain building reducing the energy consumption and carbon emission.