Thermostat-Coordinated EV Charging With HVAC Load Shifting
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Solution Overview
Problem
The heavy power draw from electric vehicle charging can overload transformers and lead to their degradation or failure, especially when multiple vehicles charge simultaneously, posing a risk to electricity supply and exacerbated by variable pricing scenarios.
Innovation Solution
A system that integrates home heating, ventilation, and air conditioning control with electric vehicle charging, using a thermostat to coordinate the operation of air conditioners and electric vehicle chargers, ensuring they do not run simultaneously by adjusting the air conditioner compressor duty cycle and temperature dead band, thereby managing power draw from the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electric vehicle charging is performed at high power draw, then charging speed and convenience are improved, but transformer overload and power delivery infrastructure strain occur
Solution Approach 1:
The system implements periodic action by scheduling EV charging to occur only during periods when the air conditioner is not operating. The controller monitors HVAC operation cycles and activates charging during off-periods, creating a periodic charging pattern that avoids continuous high load on the transformer. This resolves the contradiction by maintaining charging productivity while preventing transformer overload through temporal separation of high-power operations.
Solution Approach 2:
The system applies dynamics by making the charging operation conditional and adaptive rather than static. The controller dynamically adjusts charging activation based on real-time HVAC operation status, allowing charging to start/stop based on power availability. This dynamic control enables high charging power when needed while automatically preventing overload conditions, resolving the contradiction between charging speed and transformer reliability.
2Ease of operation
If multiple electric vehicles charge simultaneously, then user convenience and energy distribution are improved, but power delivery infrastructure strain and transformer failure risk increase
Solution Approach 1:
The system implements preliminary action by proactively monitoring HVAC operation status before initiating EV charging. The controller anticipates power availability by detecting when the air conditioner will complete its current cycle, and schedules charging to begin immediately when power becomes available. This preliminary monitoring and scheduling ensures user convenience is maintained while preventing infrastructure strain by never allowing simultaneous high-power operations.
Solution Approach 2:
The system uses feedback by continuously monitoring the operational status of the air conditioner and using this information to control EV charging activation. The controller receives feedback signals from the HVAC system about current and upcoming operation cycles, and adjusts charging accordingly. This closed-loop feedback mechanism ensures that charging only occurs when power is available, resolving the contradiction between user convenience and infrastructure protection.
3Reliability
If electric vehicle charging is coordinated with HVAC operation, then power draw management and transformer protection are improved, but system complexity and control requirements increase
Solution Approach 1:
The system applies universality by designing the controller to perform multiple functions: it monitors HVAC operation status, determines power availability, schedules EV charging, and activates/deactivates charging based on conditions. This multi-functional controller consolidates what could be multiple separate control systems into a single device, reducing overall system complexity while achieving reliable power delivery management through coordinated control of HVAC and charging operations.
Data Source
AI summary
A system and method include receiving a temperature signal from a temperature sensor, controlling operation of an air conditioner condenser, and controlling an electric vehicle charger to operate to charge an electric vehicle battery only when the air conditioner condenser is not running.