Heat Pump Partial Load Control Using Phase-Change Thermal Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems for electric or hybrid vehicles with refrigerant circuits operated as heat pumps are inefficient at partial load, leading to high energy consumption and potential compressor damage due to frequent cycling at low capacities.
Innovation Solution
A system with a controllable compressor and thermal accumulators using phase-change materials, where the compressor power is reduced during low heat requirements, and stored heat is released to meet interior temperature needs, combined with high-pressure control in the refrigerant circuit to optimize energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compressor output is regulated to reduce power consumption at partial load, then energy efficiency is improved, but the system becomes insufficient for long-term low-capacity operation due to oil circulation requirements
Solution Approach 1:
The thermal accumulator stores thermal energy in advance during high-load operation, so that during subsequent low-load operation the stored energy can be utilized, allowing the compressor to be shut off without compromising system reliability. This preliminary energy storage enables the system to withstand compressor downtime.
Solution Approach 2:
The thermal accumulator utilizes phase change materials that transition between solid and liquid phases to store and release thermal energy. This phase transition mechanism provides high-density thermal storage, enabling the system to maintain operation during compressor shutdown periods.
2Use of energy by moving object
If the compressor is frequently switched on and off at low capacity, then partial load operation is achieved, but compressor damage occurs due to excessive cycling
Solution Approach 1:
The thermal accumulator pre-stores thermal energy before compressor shutdown, enabling the system to maintain heating or cooling function without immediate compressor operation. This prevents frequent compressor cycling by providing a buffer of stored thermal energy.
Solution Approach 2:
The thermal accumulator ensures continuous thermal supply to the vehicle interior even when the compressor is shut off. The stored thermal energy is released gradually, maintaining the heating or cooling function without interruption and avoiding repeated compressor start-stop cycles.
3Device complexity
If only compressor output regulation is used for partial load control, then system simplicity is maintained, but efficiency is insufficient due to lack of additional control mechanisms
Solution Approach 1:
The thermal accumulator is integrated into the existing refrigerant circuit and controlled by the existing controller, adding thermal storage functionality without requiring complex additional control mechanisms. The system leverages existing components to achieve enhanced efficiency.
Solution Approach 2:
The thermal accumulator serves multiple functions: storing thermal energy during high-load operation, providing thermal supply during low-load operation, and enabling compressor shutdown. This multi-functionality is achieved within the existing system architecture without requiring separate dedicated control systems.
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
This approach enhances efficiency and reduces energy consumption, particularly at partial loads, extending electric vehicle range and minimizing compressor wear, while providing effective thermal storage for both heating and cooling operations.
Implementation Method 1
with a phase change material as a heat accumulator
Implementation Method 2
the thermal storage unit (7) has a phase change material as a heat accumulator
Implementation Method 3
at least one heat exchanger (8) that can be operated as a condenser or gas cooler
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a system (1) for an electric or hybrid vehicle comprising a refrigerant circuit (3) that can be operated as a heat pump for heating air for and/or in at least one part of a vehicle interior and comprising at least one compressor (5), at least one heat exchanger (13, 8) that can be operated as a condenser or gas cooler, at least one expansion element (19, 35) and at least one further heat exchanger (21) that can be operated as an evaporator, wherein the compressor output is controllable, the system (1) comprises a thermal storage unit (7) with a phase-change material as a heat storage medium that is thermally coupled or thermally coupled to the high-pressure section of the refrigerant circuit (3) that can be operated as a heat pump, and/or the system (1) comprises a control of the high pressure of the refrigerant in the high-pressure section of the refrigerant circuit (3) which is configured toThe invention relates to reducing the high pressure by a controllable pressure value of up to 50% of the design high pressure (PS) or within a sub-range thereof, compared to the pressure value of an unreduced high pressure, wherein the high pressure of the refrigerant is higher than the evaporation pressure at 20°C. Furthermore, the invention relates to an electric or hybrid vehicle and a method for controlling such a system (1). Heating is possible with the system (1) even under partial load operation.