Thermal Storage Heat Pump Control for Cold-Start Cabin Heating
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Solution Overview
Problem
In electric vehicles, the thermal energy stored in the energy storage system depletes faster in colder ambient temperatures, affecting the ability to maintain a warm passenger compartment efficiently.
Innovation Solution
A thermal storage heat pump system with multiple coolant and refrigerant circuits, including a thermal storage device, compressor, and flow control valves, controlled by sensors and a controller to manage refrigerant pressures and temperatures, optimizing heat transfer from both the thermal storage device and ambient air to the passenger compartment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thermal energy stored in the energy storage system is used to heat the passenger compartment, then the heating efficiency is improved, but the stored thermal energy depletes faster in colder ambient temperatures
Solution Approach 1:
The system pre-charges the thermal storage device (battery pack) with thermal energy during vehicle operation or when connected to external power sources. This preliminary accumulation of thermal energy ensures that sufficient heat is available for passenger compartment heating during cold conditions, preventing rapid depletion during actual heating operations.
Solution Approach 2:
A thermal storage device (battery pack) is introduced as an intermediary between the refrigerant circuit and the passenger compartment heating system. This intermediary stores thermal energy temporarily, allowing the system to decouple the heating demand from the energy storage system's direct thermal output, thereby managing the rate of thermal energy depletion.
2Reliability
If the heat pump system operates continuously to maintain passenger compartment temperature, then the comfort level is maintained, but the energy consumption increases
Solution Approach 1:
The heat pump system operates in periodic cycles rather than continuously. The controller monitors the passenger compartment temperature and cycles the heat pump operation accordingly, turning it on when temperature drops below the desired threshold and turning it off when the threshold is met. This periodic operation maintains comfort while reducing overall energy consumption compared to continuous operation.
Solution Approach 2:
The system incorporates temperature sensors that continuously monitor the passenger compartment temperature and provide feedback to the controller. Based on this feedback, the controller adjusts the heat pump operation, coolant pump speeds, and flow control valves to maintain the desired temperature with minimal energy consumption, avoiding both overheating and unnecessary continuous operation.
3Productivity
If multiple coolant circuits and flow control valves are added to optimize heat transfer, then the heating efficiency is improved, but the device complexity increases
Solution Approach 1:
The cooling system is segmented into multiple independent coolant circuits (first coolant circuit for thermal storage device, second coolant circuit for passenger compartment heating, third coolant circuit for battery cooling). Each circuit has its own coolant pump and can be controlled independently. This segmentation allows optimized heat transfer in each circuit while maintaining modular complexity that is manageable through electronic control.
Solution Approach 2:
The system employs variable speed coolant pumps and electronically controlled flow control valves that dynamically adjust their operation based on real-time thermal demands and system conditions. This dynamic control optimizes heat transfer efficiency across different operating conditions while managing complexity through electronic regulation rather than mechanical complexity.
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
Enhances the efficiency of heating the passenger compartment by effectively utilizing stored thermal energy and ambient heat, maintaining comfort while reducing energy consumption, especially in cold conditions.
Implementation Method 1
a refrigerant circuit in thermal communication with the first coolant circuit and the second coolant circuit via a first heat exchanger and a second heat exchanger, respectively
Implementation Method 2
a refrigerant circuit in thermal communication with the first coolant circuit and the second coolant circuit via a first heat exchanger and a second heat exchanger, respectively
Implementation Method 3
The thermal storage device is located in the first coolant circuit, and is configured to store thermal energy
Implementation Method 4
The heater core is located in the second coolant circuit and is configured to transfer heat from the second coolant to air flowing across the heater core to warm up the passenger compartment of the vehicle
Implementation Method 5
The compressor is located in the refrigeration circuit, and has an inlet and an outlet. The compressor is configured to compress the refrigerant from a low-side pressure at the inlet to a high-side pressure at the outlet
Implementation Method 6
The third heat exchanger is also located in the refrigeration circuit and is configured to transfer heat from ambient air to the refrigerant
Data Source
AI summary
A thermal storage heat pump system transfers heat to a passenger compartment of a vehicle from at least one of a thermal storage device and ambient air. Heat from the thermal storage device is absorbed by a first coolant flowing through it, and is transferred to a refrigerant via a first heat exchanger. The heat is then transferred from the refrigerant to a second coolant via a second heat exchanger, and then from the second coolant to air flowing into the passenger compartment via a heater core. Heat from ambient air is absorbed by the refrigerant via a third heat exchanger. The heat source is determined by at least one of the thermal storage device temperature, ambient air temperature, and ambient air humidity. At start-up of the vehicle, heat transfer to the refrigerant and to the second coolant is controlled based on low-side and high-side pressure measurements of the refrigerant.