Occupancy-Based Ventilation Control Using RFID Zone Counting
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Solution Overview
Problem
Existing HVAC systems lack the capability to automatically adjust ventilation rates based on actual occupancy levels, relying on unreliable CO2 monitors and costly active RFID tags, and fail to compile occupancy data by ventilation zones for effective demand-controlled ventilation.
Innovation Solution
A system using passive or active ID badges with remotely-scannable/transmittable identification codes, detected by tag detectors, which wirelessly communicate occupancy data to a zonal compiler and then to a central microprocessor to compute and implement ventilation rates based on ASHRAE standards, interfacing with the HVAC system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 monitors are used to estimate occupancy, then ventilation rate adjustment is achieved, but system reliability and accuracy deteriorate due to monitor limitations
Solution Approach 1:
The patent replaces the mechanical/chemical CO2 monitoring system with an electronic RFID identification system. Instead of measuring CO2 concentration levels to infer occupancy, the system uses radio frequency identification tags and readers to directly detect and count occupants, eliminating the indirect and unreliable CO2-based estimation method.
Solution Approach 2:
The patent introduces RFID tags as intermediary carriers of occupancy information. Each occupant wears or carries a passive RFID tag that serves as an identifier, allowing the system to track and count individuals without requiring complex sensing of environmental parameters like CO2 levels.
2Difficulty of detecting and measuring
If active RFID tags are used to monitor occupancy, then occupancy detection capability is achieved, but system cost increases due to expensive tags and maintenance
Solution Approach 1:
The patent employs passive RFID tags instead of active RFID tags. Passive tags are significantly cheaper, have no battery, and do not require maintenance. They are activated only when interrogated by a reader, making them ideal for cost-effective occupancy monitoring without the ongoing costs associated with active tags.
Solution Approach 2:
The patent extracts the power source (battery) from the RFID tag system, using only passive tags that draw power from the reader's electromagnetic field during communication. This eliminates the need for battery replacement and maintenance while retaining occupancy detection functionality.
3Productivity
If occupancy data is collected without zonal compilation, then occupancy counting is achieved, but ventilation control effectiveness deteriorates due to lack of zone-specific adjustment
Solution Approach 1:
The patent divides the building into multiple ventilation zones, each with its own occupancy compiler that aggregates RFID tag data specifically for that zone. This segmentation allows independent ventilation control for each zone based on its actual occupancy, rather than treating the entire building as a single unit.
Solution Approach 2:
The patent implements zone-specific occupancy compilation and ventilation control, where each ventilation zone has tailored occupancy data and control parameters. The system adjusts ventilation rates locally in each zone according to its specific occupancy conditions, rather than applying uniform control across the entire building.
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
This solution enables significant energy efficiency by accurately adjusting ventilation rates according to occupancy, reducing energy consumption and costs compared to default settings, while being simpler and less expensive than CO2 monitoring systems.
Implementation Method 1
Active or passive identification tags incorporated in identification badges worn by building occupants are used to actually count the number of occupants of a given space
Data Source
AI summary
In a demand control ventilation (DCV) system, ID codes of tags worn by occupants are detected in each room by a tag detector and wirelessly communicated to a zonal occupancy compiler. The zonal occupancy count arrived at by the compiler is transmitted to a DCV microprocessor, which interfaces with the ventilation controller of the building's HVAC system and sets the zonal ventilation rate based on the occupancy count and applicable ASHRAE standards.