Systems and methods for combined outdoor air fraction and VAV unit control
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Solution Overview
Problem
Existing HVAC systems struggle to efficiently manage ventilation and temperature control in buildings, particularly in maintaining carbon dioxide levels and temperature within desired thresholds across multiple zones, without excessive energy consumption.
Innovation Solution
A ventilation and temperature control system that integrates an air handling unit (AHU) and variable air volume (VAV) units, utilizing processing circuitry to adjust fresh air intake fraction and damper positions based on carbon dioxide levels and temperature measurements, employing predictive models and sinusoidal functions to maintain CO2 levels below thresholds and temperatures within desired ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the AHU increases fresh air intake to maintain CO2 levels below thresholds across multiple zones, then ventilation control objective is satisfied, but energy consumption increases
Solution Approach 1:
The system dynamically adjusts the fresh air intake fraction of the AHU between multiple discrete values based on real-time CO2 measurements and predictive models, rather than maintaining a constant intake rate. This allows the system to provide adequate ventilation only when and where needed, reducing unnecessary energy consumption during periods of low occupancy or CO2 levels.
Solution Approach 2:
The system implements zone-specific control by adjusting damper positions of individual VAV units based on CO2 measurements and occupancy predictions for each specific zone. This localized control approach ensures that fresh air is delivered precisely to zones that need it, rather than uniformly across the entire building, thereby optimizing energy efficiency while meeting ventilation requirements.
2Reliability
If the system dynamically adjusts fresh air intake fraction and damper positions to maintain CO2 levels and temperature, then indoor air quality improves, but device complexity increases
Solution Approach 1:
The system merges ventilation control and temperature control functions into a single integrated control framework that simultaneously manages both CO2 levels and temperature by coordinating AHU fresh air intake with VAV unit damper positions. This unified approach improves indoor air quality while avoiding the need for separate, redundant control systems.
Solution Approach 2:
The system employs predictive models that use historical data and real-time measurements to automatically forecast occupancy and environmental conditions, enabling the control system to make proactive adjustments without constant human intervention. This self-regulating capability maintains high indoor air quality while reducing the operational complexity burden.
3Loss of energy
If the AHU operates with variable fresh air intake fraction, then energy efficiency improves, but temperature control precision deteriorates
Solution Approach 1:
The system continuously monitors actual temperature measurements from each zone and uses this feedback to adjust damper positions and fresh air intake in real-time. This closed-loop control ensures that temperature remains within the desired range even as fresh air intake varies, maintaining temperature control precision while achieving energy efficiency gains.
Solution Approach 2:
The system uses predictive models to forecast future occupancy and thermal loads, allowing it to pre-adjust fresh air intake and damper positions before actual changes occur. This proactive control approach prevents temperature deviations rather than merely reacting to them, maintaining temperature precision while optimizing energy usage.
Data Source
AI summary
An control method includes obtaining measurements of a carbon dioxide (CO2) level of a zone and a temperature of the zone. The method includes determining, based on the CO2 level of the zone and the temperature of the zone, a combination if (i) control decisions for an air handling unit (AHU) and (ii) control decisions for a damper of a variable air volume (VAV) unit to satisfy both a ventilation control objective and a temperature control objective. The control decisions for the AHU include adjustments to a fresh air intake fraction of the AHU between multiple values over time, and the control decisions for the VAV unit include adjustments to a position of a damper of the VAV unit over time. The method includes operating the AHU according to the control decisions for the AHU and operate the VAV unit according to the control decisions for the VAV unit.