Learning Thermostat Power Harvesting and Progressive Function Scaling
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Solution Overview
Problem
Thermostats powered by disposable or rechargeable batteries face challenges in reducing power usage when battery levels are low, and existing power harvesting techniques may not suffice during periods of high power demand or temporary power interruptions.
Innovation Solution
A method for strategically reducing power usage in thermostats by using a rechargeable battery that harvests power from HVAC systems, altering activities based on battery voltage or capacity, including reducing display backlighting, curtailing wireless communications, and disabling HVAC stages, to conserve energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thermostat performs processor intensive functions and wireless communications, then the thermostat functionality is enhanced, but power consumption increases making battery power unrealistic
Solution Approach 1:
The patent combines multiple power sources (power harvesting circuit from HVAC transformer and rechargeable battery) into a hybrid power architecture. The power management module intelligently switches between harvested power and battery power, allowing the thermostat to maintain enhanced functionality with wireless communications and processing while managing overall power consumption through coordinated use of both power sources.
Solution Approach 2:
The patent dynamically adjusts power consumption parameters based on available power. The power management module monitors power availability and adjusts operational modes, transmission power levels, display refresh rates, and processing intensity to match available power from harvesting or battery, enabling full functionality when power is abundant while conserving energy when power is limited.
2Adaptability or versatility
If a thermostat uses power stealing from HVAC transformer, then no C-wire is needed, but power availability is limited and may cause voltage drop affecting load coil operation
Solution Approach 1:
The patent incorporates a rechargeable battery that is charged during periods when harvested power is sufficient. This battery serves as a cushion or backup power source that activates when harvested power becomes insufficient or unavailable, preventing voltage drops and ensuring continuous reliable operation of both the thermostat and HVAC system without affecting load coil operation.
Solution Approach 2:
The power management module acts as an intermediary between the power harvesting circuit and the thermostat load. It monitors voltage levels and power availability, intelligently switching between harvested power and battery power, and regulating power delivery to prevent voltage drops that could affect HVAC transformer and load coil operation, thus ensuring system reliability.
3Speed
If a remote sensor transmits signals at higher power level, then data transfer rate increases, but battery life decreases
Solution Approach 1:
The patent implements dynamic transmission power adjustment in remote sensors. The sensors continuously monitor signal quality, distance to the thermostat, and battery status, then adaptively adjust transmission power levels. When signal conditions are good or distance is short, transmission power is reduced to conserve battery. When signal quality degrades or distance increases, power is increased to maintain data transfer rate, optimizing the balance between communication performance and battery life.
4Ease of operation
If a thermostat LCD display continuously shows temperature, then user interface functionality is maintained, but battery power depletes faster
Solution Approach 1:
The patent implements periodic or on-demand display activation based on user presence detection. Motion sensors or proximity sensors detect when a user approaches the thermostat and activate the display. When no user presence is detected for a predetermined period, the display enters sleep mode or turns off completely. This periodic activation maintains user interface functionality when needed while dramatically reducing display power consumption during extended idle periods.
Data Source
AI summary
In a multi-sensing, wirelessly communicating learning thermostat that uses power-harvesting to charge an internal power source, methods are disclosed for ensuring that the battery does not become depleted or damaged while at the same time ensuring selected levels of thermostat functionality. Charge status is monitored to determine whether the present rate of power usage needs to be stemmed. If the present rate of power usage needs to be stemmed, then a progression of performance levels and/or functionalities can be scaled back according to a predetermined progressive power conservation algorithm. In one embodiment, a wake-on-proximity function that activates a user interface based on readings from the proximity sensor may be altered while still allowing a HVAC control circuitry to operate as normal.