Dynamic rule-based change-over ventilation strategy with weather-responsive air-conditioning setpoints

Abstract

Recent studies have actively developed dynamic rule-based mixed-mode ventilation (MMV) strategies to manage indoor thermal quality in an energy-efficient manner. Existing research on the dynamic rule-based MMV control has mainly focused on window opening area ratio calculation with fixed setpoints of mechanical operation. However, using fixed setpoints tends to force mechanical operation, though the outdoor temperature is suitable for natural ventilation. For this reason, this study questions whether a rule-based MMV strategy can effectively manage indoor thermal quality and reduce air-conditioning (heating and cooling) load when incorporated with the methods adjusting operation variables of both active and passive systems. To address this research question, this study proposes a dynamic rule-based change-over ventilation strategy integrated with three control components. First, a rule-based control component for adjusting air-conditioning setpoints is developed. Second, an operation mode selection scheme is proposed to decide the appropriate mode for fulfilling thermal demands. Third, a dynamic window opening area ratio function is proposed to provide a sufficient cooling effect to rooms when natural ventilation is required. The proposed strategy integrated with these key components is optimized for each space by non-dominated sorting genetic algorithm II. As a result of the optimization, the proposed strategy reduces 59.77% of the total cooling and heating load against the baseline, which fully operates the building by mechanical systems while ensuring 97.75% of thermally comfortable periods relative to the entire occupied period. Conclusively, this study identified that dynamically adjusting operation thresholds in MMV strategy achieves a substantial load reduction rate and ensures thermal comfort.