Cascade Heat Pump Layout for EV Heating in Extreme Cold
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Solution Overview
Problem
Existing vehicle thermal management systems struggle to effectively manage temperature in scenarios with extremely low outdoor ambient temperatures, leading to inefficient heating and reduced vehicle usage.
Innovation Solution
A cascade heat pump system for electric vehicles, comprising a low-pressure-stage and a high-pressure-stage compression device, along with a functional heat exchange device, which allows for efficient heat exchange and utilization of waste heat from the battery, motor, and electronic control circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-stage heat exchange circuit is used, then the system structure is simple, but the heating efficiency is insufficient in extremely low outdoor ambient temperatures
Solution Approach 1:
The patent divides the compression device into two independent stages: a first compression device and a second compression device. Each stage has its own evaporator, compressor, and expansion valve, allowing independent operation and optimization for different temperature conditions. This segmentation enables the system to maintain high heating efficiency in extremely low temperatures while keeping each individual stage relatively simple.
Solution Approach 2:
The patent designs the heat exchange circuit to serve multiple functions: the first heat exchange circuit handles high-temperature heating requirements, while the second heat exchange circuit handles low-temperature heating requirements. The system can switch between or combine these circuits based on ambient temperature, making the thermal management system universally applicable across a wide temperature range.
2Reliability
If a cascade heat pump system with multiple compression devices is used, then the heating efficiency in low temperature is improved, but the device complexity increases
Solution Approach 1:
The patent merges the first and second heat exchange circuits into a unified thermal management system that shares common components such as the battery heat exchanger, motor heat exchanger, and electronic control heat exchanger. This combining approach allows the system to achieve high heating efficiency through cascade compression while reducing overall complexity by sharing heat exchange components between the two stages.
Solution Approach 2:
The patent implements dynamic switching between the first and second heat exchange circuits based on ambient temperature conditions. The control system can dynamically adjust which circuit operates or how they operate together, optimizing performance for current conditions while simplifying control logic through rule-based switching rather than complex continuous adjustment.
3Ease of manufacture
If waste heat from battery and motor is not utilized, then the system design is simpler, but energy efficiency is reduced
Solution Approach 1:
The patent converts the waste heat generated by the battery and motor during operation into a useful resource for cabin heating. The heat exchangers coupled to the battery and motor capture this waste heat and transfer it to the cabin through the heat exchange circuits, especially valuable in cold conditions. This transforms what would be energy loss into a contribution toward heating efficiency.
Solution Approach 2:
The thermal management system uses the vehicle's own operational components (battery and motor) as heat sources for cabin heating. During motor operation or battery charging/discharging, the generated heat is automatically captured and redirected to heat the cabin, allowing the vehicle to heat itself using its own operational byproducts without requiring external energy input.
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
The system ensures efficient heating and cooling of the vehicle's battery, motor, cabin, and electronic control circuit board, even in extremely low temperatures, thereby improving the vehicle's operational efficiency and extending its driving range.
Implementation Method 1
The second working medium is capable of exchanging, in the low-pressure-stage intercooler, heat with the first working medium
Implementation Method 2
The air-side heat exchanger communicates with the cabin heat exchanger and the battery heat exchanger separately
Data Source
AI summary
A cascade heat pump system for an electric vehicle includes a low-pressure-stage compression device, a high-pressure-stage compression device, and a functional heat exchange device. The low-pressure-stage compression device includes a low-pressure-stage compressor, a low-pressure-stage evaporator, a low-pressure expansion valve, and a low-pressure-stage intercooler connected in sequence. The high-pressure-stage compression device includes a high-pressure-stage compressor, a high-pressure-stage four-way valve, an air-side heat exchanger, a water-side heat exchanger, a cabin heat exchanger, and a battery heat exchanger. The compressor outlet of the high-pressure-stage compressor communicates with one of the air-side heat exchanger or the water-side heat exchanger. The air-side heat exchanger communicates with the cabin heat exchanger and the battery heat exchanger separately. The functional heat exchange device includes a motor heat exchange assembly, a heat exchange water tank, a battery heat exchange member, and a cabin heat exchange member.