Load allocation methods for the thermal and electrical chillers in distributed energy systems for system efficiency improvement

Abstract

Distributed energy systems fully utilize clean and renewable energy to satisfy the thermal and electrical loads of users. Absorption chillers are adopted to recover the waste heat from generators and are generally supplemented by electrical chillers or heat pumps to meet the insufficient thermal load. However, the load allocated to the absorption chillers can be affected by the heat pump/chiller owing to the chilled or hot water system distribution, leading to a lower energy utilization efficiency. In this study, a new load allocation method is proposed in which the water flow rate (F-method) or supply temperature (T-method) of chilled/hot water systems is adjusted according to the cooling production capability of absorption chillers. The proposed method was verified using a distributed energy system serving a campus. The results showed that the cooling utilization ratio of the absorption chillers could be maintained close to 1, and the absorption chiller could follow the system waste heat well. Consequently, the primary energy efficiency and cost savings could be increased by 1.74% and 1.55%, respectively, and carbon emissions from the cooling systems could be reduced by 4.21%. This study can thus help improve the application and performance of distributed energy systems.