Exhaust demand control system and methods
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Solution Overview
Problem
High plume exhaust fan systems are energy-inefficient and unreliable due to the high energy consumption of bypass air, which does not result in energy savings when exhaust fan airflow is reduced, and existing contaminant sensing methods are prone to fouling and unreliable.
Innovation Solution
Implementing a multipoint air sampling system with sensor protection modes and IoT connectivity to accurately and reliably detect contaminants, allowing for adaptive control of exhaust fan exit velocities based on contaminant levels and environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high plume exhaust fan systems operate at high exit velocities to ensure contaminant dispersion, then contaminant dilution is improved, but energy consumption increases significantly
Solution Approach 1:
The exhaust fan system dynamically adjusts exit velocity based on real-time contaminant concentration measurements from multipoint air sampling sensors. When contaminant levels are low, the fan operates at reduced speed to save energy; when contaminants are detected, the fan increases velocity to ensure proper dispersion, thus resolving the contradiction between energy efficiency and reliable contaminant dispersion
Solution Approach 2:
The system implements feedback control by continuously monitoring contaminant levels at multiple exhaust points and adjusting fan exit velocity accordingly. The sensor data feeds back to the control system, which modulates fan speed to maintain adequate contaminant dispersion while minimizing energy consumption, directly addressing the technical contradiction
2Measurement precision
If continuous air sampling is performed to monitor contaminant levels, then exhaust demand control accuracy is improved, but sensor exposure to high contaminant levels increases causing fouling
Solution Approach 1:
The system performs preliminary dilution of exhaust air by mixing it with clean ambient air before it reaches the sensors. This pre-dilution action reduces contaminant concentration at the sensor location, allowing continuous monitoring without rapid fouling, thus maintaining both measurement precision and sensor reliability
Solution Approach 2:
Clean ambient air acts as an intermediary substance that mixes with the contaminant-laden exhaust air before sensor exposure. This intermediary dilution protects the sensors from direct exposure to high contaminant concentrations while still enabling accurate contaminant detection through the mixed sample
3Use of energy by moving object
If exhaust fan airflow is reduced to save energy, then energy consumption decreases, but contaminant dispersion capability is compromised
Solution Approach 1:
The system uses feedback from multipoint contaminant sensors to dynamically adjust fan airflow. When sensors detect low contaminant levels, the system reduces airflow to save energy; when contaminants are detected, airflow increases to ensure proper dispersion. This feedback mechanism resolves the contradiction by making dispersion reliability conditional on actual contaminant presence
Solution Approach 2:
The system changes the operational parameter of fan exit velocity based on contaminant concentration levels. By dynamically adjusting this parameter rather than maintaining a fixed high velocity, the system achieves energy savings during low-contaminant periods while maintaining dispersion reliability when needed, resolving the technical contradiction
4Reliability
If bypass air is used to maintain fan exit velocity, then contaminant dispersion is maintained, but energy savings from reduced exhaust airflow are lost
Solution Approach 1:
The system dynamically adjusts fan exit velocity to match actual contaminant dispersion needs rather than maintaining a constant high velocity with bypass air. This dynamic adjustment eliminates the need for energy-consuming bypass air while maintaining dispersion reliability only when contaminants are actually present, resolving the contradiction between dispersion reliability and energy loss
Data Source
AI summary
Methods and apparatus for an exhaust demand control system for measuring one or more contaminants at one or more exhaust locations within one or a plurality of exhaust ducts or plenums served by an exhaust fan system. Example systems and methods can include sensing the one or more contaminants within the one or more exhaust duct locations using a multipoint air sampling system having one or more sensors and comparing contaminant concentration measurements from the one or more of said exhaust duct or plenum locations against an action level to create a fan setback signal.