HVAC Multi-Mode Control to Balance Indoor Air Quality and Energy Use
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Solution Overview
Problem
HVAC systems face challenges in balancing ventilation rates to maintain indoor air quality and occupant comfort while minimizing energy consumption, especially during conditions that require increased ventilation, such as pandemics, where the system may lack capacity to adequately condition incoming fresh air.
Innovation Solution
The implementation of an HVAC control system that automatically selects operating modes based on sensed values, using a ventilation setpoint prediction algorithm to optimize ventilation rates while maintaining comfort conditions and indoor air quality within specified thresholds, and adjusting these settings dynamically to improve prediction accuracy over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ventilation rate is increased to reduce the spread of pathogens and maintain indoor air quality, then the health and safety of occupants is improved, but the energy consumption of the HVAC system increases and the system may lack capacity to adequately condition the incoming fresh air
Solution Approach 1:
The system dynamically adjusts the ventilation rate based on real-time sensed values (occupancy, CO2 levels, temperature, humidity) and automatically selects operating modes (health mode, energy savings mode 1, energy savings mode 2) to optimize the balance between indoor air quality and energy consumption. This dynamic adaptation allows the system to provide adequate ventilation when needed while minimizing energy usage during periods of lower demand.
Solution Approach 2:
The system changes operational parameters (ventilation rate, temperature setpoint, humidity setpoint) based on the selected operating mode and current building conditions. In health mode, the system prioritizes maximum ventilation with relaxed energy constraints, while in energy savings modes, it reduces ventilation rate and adjusts conditioning parameters to minimize energy consumption while maintaining acceptable indoor air quality thresholds.
2Reliability
If the ventilation rate is set too high during conditions requiring increased ventilation, then indoor air quality is improved, but the HVAC system lacks the heating and/or cooling capacity to adequately condition the incoming fresh air while maintaining occupant comfort
Solution Approach 1:
The system dynamically coordinates ventilation rate adjustments with heating and cooling capacity management. When operating in health mode with increased ventilation, the system simultaneously adjusts temperature and humidity setpoints and modulates HVAC equipment capacity to ensure incoming fresh air is adequately conditioned, thereby maintaining occupant comfort despite higher ventilation rates.
Solution Approach 2:
The system proactively pre-conditions incoming fresh air by adjusting heating and cooling equipment in advance of when the ventilated air will be supplied to occupied spaces. This preliminary conditioning ensures that even at high ventilation rates, the fresh air reaches occupants at comfortable temperature and humidity levels.
Data Source
AI summary
Methods and systems for operating a Heating, Ventilating and Air Conditioning (HVAC) system in accordance with one of a plurality of operating modes. The plurality of operating modes include one or more of a health mode, an energy savings mode and a balanced mode. In some cases, the operating modes include two or more energy saving modes. The currently operating mode is selected based on the current operating conditions of the building and the desired goals of the building operator. The goals can include, for example, reducing energy usage, reducing pathogen risks, increasing air quality and/or a combination of these goals. In some cases, the operating modes are autonomously controlled. In some cases, the operating modes are manually controlled.