Simulation-Based evaluation of Cost-Responsive supply air temperature control strategy for office buildings across different climates

Abstract

The supply air temperature (SAT) setpoint control strategy is a vital part of a variable air volume (VAV) system. This paper presents a new cost-responsive (CORE) SAT control algorithm for the VAV system which does not require discharge air temperature data for easier implementation, along with a new humidity control strategy that constrains the maximum SAT based on outdoor dewpoint temperature to meet dehumidification requirements in humid climates. We conducted a comprehensive parametric simulation study using a representative office building model to assess energy cost savings of the new CORE control algorithm against other widely adopted control strategies, including the best industry practice ASHRAE Guideline 36 (G36). We created an EnergyPlus-Python-based simulation environment to implement all control algorithms. Results showed that the new CORE algorithm consistently yielded higher energy cost savings than other control algorithms, despite variations in climate, energy tariff structure, and building design and operation. Compared to G36, the new CORE algorithm reduced energy costs by a mean (first – third quartiles) of ∼ 4 % (0.8–6.9 %) across all simulated cases. Moreover, the climatic conditions had a significant impact on the control performance. In milder climates, the new CORE algorithm achieved higher energy cost savings due to considerable economizer hours, e.g., with ∼ 7 % (6.3–7.1 %) savings compared to G36 and ∼ 31 % (26.8–36.0 %) compared to the worst-performing fixed SAT strategy for Oakland. Conversely, in more extreme climates with fewer economizer hours and dehumidification constraints, energy cost savings of the new CORE algorithm were diminished, e.g., with 0.6 % (0.2–0.7 %) savings relative to G36 and 5.4 % (4.3–6.2 %) relative to the least effective Warmest SAT strategy for New York City. These findings demonstrate the potential of the new CORE SAT control strategy to reduce HVAC operating costs while maintaining occupant comfort.