Multi-Story Building Pressure Control to Counteract Stack Effect
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Solution Overview
Problem
Multi-story buildings face challenges in maintaining comfortable temperatures in lower floors due to 'stack effect' pressure differentials, which disrupt HVAC control systems, leading to inefficient energy use and temperature fluctuations, especially during cold weather.
Innovation Solution
The implementation of the Pathian Optimal Building Pressurization Control (POBPC) algorithm, which adjusts the return air fan setpoints and relief damper positions based on calculated stack effect pressures to maintain optimal building pressure, reducing energy consumption and minimizing air infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If standard HVAC control sequences are used to maintain building pressure, then energy consumption is reduced under normal conditions, but temperature control in lower floors deteriorates during cold weather due to stack effect
Solution Approach 1:
The control system dynamically adjusts the building pressure setpoint based on outdoor temperature conditions. During cold weather when stack effect is significant, the system increases the positive pressure setpoint to counteract the downward air flow caused by stack effect, thereby preventing cold air infiltration into lower floors and maintaining temperature comfort.
Solution Approach 2:
The invention changes the pressure differential parameter across the building envelope in response to varying outdoor temperatures. By calculating the stack effect based on indoor and outdoor temperature differences, the system adjusts the building pressure setpoint to compensate for stack effect forces, ensuring adequate pressure to prevent cold air intrusion during cold weather while maintaining energy efficiency during milder conditions.
2Temperature
If building pressure is increased to prevent cold air infiltration during cold weather, then temperature comfort in lower floors is improved, but energy consumption increases
Solution Approach 1:
The system dynamically adjusts the building pressure setpoint parameter based on outdoor temperature conditions. During cold weather when stack effect is significant, the pressure setpoint is increased to maintain temperature comfort. During milder conditions, the setpoint is reduced to minimize energy consumption, achieving an optimal balance between comfort and energy efficiency.
Solution Approach 2:
The control system uses feedback from outdoor temperature sensors and calculated stack effect forces to continuously adjust the building pressure setpoint. This closed-loop control ensures that the pressure is increased only when and to the extent necessary to counteract stack effect, rather than maintaining constantly high pressure, thereby reducing overall energy consumption while maintaining comfort during critical periods.
3Object-generated harmful factors
If return air fan setpoints are adjusted to maintain optimal building pressure during stack effect, then air infiltration is minimized, but control system complexity increases
Solution Approach 1:
The system calculates stack effect forces based on indoor and outdoor temperature differences and uses these calculations to dynamically adjust return air fan setpoints and relief damper positions. This parameter-based control approach minimizes air infiltration by maintaining appropriate building pressure without requiring complex sensor arrays or advanced control algorithms, achieving simplicity through physics-based calculations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
POBPC effectively manages building pressure, optimizing return air fan speeds, reducing energy costs, and minimizing air infiltration, thereby maintaining comfortable temperatures and reducing the strain on HVAC systems.
Implementation Method 1
the primary cause of lobby temperature issues was directly related to the invasion of cold air on lower floors as a result of 'stack effect' pressure differentials exerted on the building's envelop as outside air temperatures drop below 25 F
Implementation Method 2
building pressurization as a function of the difference between inside and outside air temperature and the resulting difference between inside and outside air density
Data Source
AI summary
The air flow of an HVAC system for a multi-story building B is controlled by optimizing the pressure setpoint at the return air plenum PL-1 used for removing or recirculate air from the building, by measuring a pressure differential between the building B air and atmosphere A air at a sensor location P-2, computing a desired pressure differential between the building B air and atmosphere A air, based upon a computed stack effect pressure that is expected to develop at the sensor location on the building for the current inside and outside air temperature in the absence of mechanical action, and controlling the return air fan and damper D-1 to pressurize the air in at the sensor location to produce the desired pressure differential between the building B air and atmosphere A air at the sensor P-2 location.