Semi-Electric Refrigeration Drive for Low-Idle Transport Cooling
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Solution Overview
Problem
Conventional mobile refrigerated systems for transporting perishable cargo rely on diesel engines with limited operating efficiency and fuel consumption, particularly during temperature maintenance and standstill modes, where the engine often idles or operates at reduced capacity.
Innovation Solution
A semi-electric transport refrigeration system with an integrated electric generator and controller, allowing direct drive of the compressor by a diesel engine, and utilizing a battery pack for power during stable temperature conditions, enabling downsizing of the engine and optimizing power distribution through AC and DC buses with converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diesel engine is used to power the compressor and fans during all operating modes, then the system can maintain temperature control during temperature pull down and maintenance modes, but the engine operates at reduced capacity or idles during standstill and temperature maintenance modes, resulting in limited fuel efficiency
Solution Approach 1:
The power supply system is segmented into multiple independent power sources: a diesel engine for high-power demands, a battery pack for low-power or idle periods, and a generator for supplemental power. This segmentation allows the system to select appropriate power sources based on operating conditions, reducing diesel engine runtime and fuel consumption while maintaining temperature control reliability.
Solution Approach 2:
The system dynamically switches between different power sources based on real-time operating conditions. The controller monitors temperature, operating mode, and power availability to determine whether to use the diesel engine, battery pack, or generator, optimizing fuel efficiency while ensuring continuous temperature control.
2Weight of moving object
If the diesel engine is downsized to reduce weight and cost, then the engine weight and system complexity are reduced, but the engine may lack sufficient power during temperature pull down mode
Solution Approach 1:
The system merges multiple power sources (diesel engine, battery pack, and generator) to collectively meet the power demands of the refrigeration system. This combination allows the diesel engine to be downsized since it no longer needs to provide all power independently, reducing engine weight while ensuring sufficient power availability during high-demand temperature pull down mode through coordinated operation of all power sources.
3Stability of the object's composition
If the diesel engine operates continuously to maintain temperature, then temperature stability is ensured, but fuel consumption increases and engine wear accelerates
Solution Approach 1:
The diesel engine operates periodically rather than continuously, activating during high-power需求的温度下拉模式 and deactivating during temperature maintenance or standstill modes when the battery pack or generator can maintain temperature control. This periodic operation reduces fuel consumption and engine wear while maintaining temperature stability through coordinated power source switching.
4Use of energy by moving object
If an all-electric system with generator is used, then fuel efficiency improves during maintenance mode, but system complexity and initial cost increase
Solution Approach 1:
The system implements a hybrid configuration that partially adopts the all-electric approach by incorporating a battery pack and generator, but retains the diesel engine for high-power demands. This partial implementation achieves fuel efficiency improvements during maintenance and standstill modes without the full complexity and cost of a complete all-electric system, providing a balanced solution.
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 configuration reduces engine size and weight, lowers fuel consumption, and maintains efficient temperature control while minimizing idle engine operation, enhancing overall system efficiency and reducing fuel costs.
Implementation Method 1
an electric generator, allowing direct drive of the compressor by a diesel engine
Implementation Method 2
utilizing a battery pack for power during stable temperature conditions
Data Source
Figure 1
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Figure 3
AI summary
A power supply system for a transport refrigeration system (20) includes an engine (26) coupled to a compressor (32) of a refrigeration unit for direct drive powering the compressor (32) and a generator (24) arranged to also be direct driven by the engine (26) for generating electric power. The generator (24) and the compressor (32) are mounted to a common drive shaft (25) driven by the engine (26), and the generator (24) may be integrated with the compressor (32). The power supply system may further include an alternator (50) arranged to be belt driven by the engine (26) for generating DC electric power. A battery pack (28) may be provided for storing and supplying additional DC power. During peak load demand on the refrigeration unit (20), the engine (26) may be operated with the generator (24) switched off to directly drive the compressor (32) and direct current may be drawn from the battery pack (28) to drive the condenser/gas cooler and evaporator fans (40, 44).