Commissioning an Existing Heat Recovery Chiller System at a Large District Plant
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abstract
2018 ASHRAE A heat recovery chiller provides heating hot water to buildings by using recoveredheat from the chiller, whichis efficient and cost-effective. However, not every central plant is an appropriate application for heat recovery chillers because coincident heating hot-water and chilled-water loads are required. Most previous studies on applications of heat recovery chillers have focused on techniques for optimal design of a utility plant with heat recovery chillers. There are very few guidelines for operators on how to run a heat recovery chiller system efficiently at different operating conditions. Factors include electricity demand charges and rate structure, heating hot-water supply temperature, heating hot-water loop delta-T degeneration, chilled-water loop delta-T degeneration, and the performance of other variable-speed drive chillers in the plant, which all affect operational efficiency. This paper presents several commissioning measures for a heat recovery chiller application at a large district plant in central Texas. The on-site measured data from the building automation system (BAS) is used to develop a regression model to evaluate the savings potential for each measure. The current operating strategy saves $270,375/year compared to a baseline chiller without heat recovery, but the proposed control strategies would improve the savings to $389,182/year at current utility prices, or 43.9% more savings than the current control strategy. Although these savings are based on a case-study project, the methodology and control strategies can be applied to optimize other heat recovery chiller applications.
