Occupancy-Based HVAC Control to Extend Battery-Powered Sensor Lifetime
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Solution Overview
Problem
HVAC systems face challenges in determining the appropriate level of ventilation based on occupancy levels, and battery-powered CO2 and VOC sensors have limited lifetimes due to high energy requirements, affecting their usability in controlling indoor environmental conditions.
Innovation Solution
A control system that uses presence sensors to generate occupancy data, which is processed with a control model to direct actions to the HVAC system, and environmental sensors are used sparingly for verification and tuning, optimizing their power consumption and positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If battery-powered CO2 and VOC sensors are used for measuring environmental conditions, then ease of installation and positioning is improved, but sensor lifetime is limited due to high energy consumption
Solution Approach 1:
The system implements periodic measurement cycles where environmental sensors are activated only when occupancy changes are detected by presence sensors. During periods of stable occupancy, sensor measurements are suspended, dramatically reducing power consumption while maintaining air quality monitoring effectiveness.
Solution Approach 2:
The control model uses occupancy data from low-power presence sensors to autonomously determine when environmental measurements are needed, eliminating the need for continuous high-power sensor operation while maintaining system effectiveness.
2Measurement precision
If continuous environmental sensor measurement is used to verify control model, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The system performs environmental measurements periodically based on occupancy triggers rather than continuously. When presence sensors detect occupancy changes, the control system activates environmental sensors for measurement and verification. This periodic approach maintains measurement precision for model verification while reducing energy consumption by keeping sensors dormant during stable periods.
3Use of energy by moving object
If occupancy data alone is used to control HVAC, then energy consumption is reduced, but ability to determine appropriate ventilation levels deteriorates
Solution Approach 1:
The control model serves as an intermediary that translates occupancy data from presence sensors into appropriate ventilation control actions. The model contains pre-established relationships between occupancy levels and required ventilation, allowing the system to determine appropriate ventilation levels without continuous environmental sensing while maintaining energy efficiency.
Solution Approach 2:
The control model is pre-trained with environmental data to establish the relationship between occupancy and required ventilation levels. This preliminary action allows the system to make accurate ventilation decisions based solely on occupancy data during normal operation, eliminating the need for continuous environmental measurements.
Data Source
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AI summary
A control system for controlling environmental conditions prevailing in a building comprises one or more presence sensors (101) for producing occupancy data indicative of physical activity in the building and a data processing system (102) for controlling a building service system related to the environmental conditions based on: i) the occupancy data and ii) a control model for producing, based on the occupancy data, control actions to be directed to the building service system. The control system further comprises environmental sensors (104) for measuring the environmental conditions. The data processing system is configured to verify and/or tune the control model based on the measured environmental conditions and on requirements related to the environmental conditions. As the building service system is controlled based on the occupancy data, the environmental sensors can be battery-powered devices which are used only when there is a need to verify and/or tune the control model.