Operation optimization of suspended radiant ceiling panel system using a grey-box modeling approach considering energy consumption and discounted payback period

To optimize and enhance the operational performance of radiant ceiling panel systems, it is essential to develop predictive models that balance the accuracy and computational efficiency. This paper proposes a grey-box model of a suspended radiant ceiling panel (SRCP) system, separated from the building envelope. Parameter identification was conducted using the experimental data collected from an office equipped with a SRCP and open-loop groundwater heat pump (GWHP) system. A TRNSYS model was developed to supplement the experimental data. Subsequently, the grey-box model was used to optimize the system operation by adjusting the inlet water temperature of the SRCP system with the aiming of reducing the electrical consumption of the GWHP system while maintaining the indoor thermal comfort. The optimization resulted in a 12.3 % reduction in the total electrical consumption. Moreover, the optimization eliminated the morning time lag in winter caused by the thermal inertia of the thick concrete walls. Finally, an economic analysis was performed to investigate the optimal design configurations for the building thermal envelope insulation and variations in the ceiling panel area. With normal insulation as the benchmark, the payback time for a good insulation design was estimated to be 10 years, whereas that for a superior insulation design was 20 years. However, the use of superior or good insulation design can reduce the coverage area, thereby reducing the investment costs. Based on the economic considerations, the coverage area should be adjusted to prevent system oversizing and unnecessary expenditures.