Trailer Refrigeration Economizer Control Under Generator Power Limits
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Solution Overview
Problem
Electrically powered trailer refrigeration systems face challenges in efficiently meeting refrigeration capacity demands due to electrical losses, leading to increased engine, generator, compressor, and fan sizing, which affects cost, fuel efficiency, emissions, and design space limitations.
Innovation Solution
The system incorporates a bypass circuit and economizer circuit with a scroll compressor that can operate in economized or non-economized modes, optimized by a controller to adjust power usage based on refrigeration demand and available generator power, using an economizer circuit to inject refrigerant vapor into an intermediate stage of the compressor and a bypass circuit to unload refrigerant capacity as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If engine, generator, compressor, and fan sizing are increased to compensate for electrical losses, then refrigeration capacity requirements are met, but system cost, fuel efficiency, and emissions worsen
Solution Approach 1:
The patent changes the operating parameters of the compressor by implementing variable speed control and optimized start-stop sequences. The compressor operates at reduced speeds during low-load conditions and is cycled off during minimal load periods, directly reducing energy consumption while maintaining refrigeration capacity through intelligent parameter management rather than hardware scaling
Solution Approach 2:
The system transitions from static, oversized component sizing to dynamic operation with real-time adjustment of compressor speed and cycling. The controller continuously monitors system conditions and dynamically adjusts compressor operation, allowing the system to adapt to varying refrigeration loads and minimize energy consumption without requiring oversized hardware
2Reliability
If engine, generator, compressor, and fan sizing are increased to compensate for electrical losses, then refrigeration capacity requirements are met, but system cost increases
Solution Approach 1:
The patent utilizes parameter changes in compressor operation (variable speed, optimized cycling) to reduce the required capacity of expensive components. By intelligently managing operational parameters, the system achieves required refrigeration capacity with smaller, less expensive hardware, directly reducing manufacturing and acquisition costs
3Reliability
If engine, generator, compressor, and fan sizing are increased to compensate for electrical losses, then refrigeration capacity requirements are met, but design space limitations are exacerbated
Solution Approach 1:
The patent applies parameter changes to compressor operation (variable speed control, optimized cycling sequences) that enable the system to achieve required refrigeration capacity with significantly reduced component sizes. This intelligent operational management allows compact component packaging, directly addressing design space constraints in mobile refrigeration applications
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 reduces engine horsepower and generator requirements, improving fuel efficiency and reducing emissions while providing more design space by optimizing refrigeration system performance according to available power and demand.
Implementation Method 1
using an economizer circuit to inject refrigerant vapor into an intermediate stage of the compressor
Implementation Method 2
a refrigeration compressor which is a scroll compressor having a suction inlet, a discharge outlet, an intermediate pressure discharge port
Data Source
Figure 1
AI summary
The refrigeration unit of an electrically powered trailer refrigeration system includes an economized scroll compressor and an economizer circuit selectively operable to inject refrigeration vapor into an intermediate stage of the scroll compressor. An engine driven generator produces AC current to power the scroll compressor and other electric components of the system. During operation of the refrigeration system at high capacity demand, a controller will operate the refrigeration system in an economized mode if sufficient electric power is available from the generator and in the non-economized mode if insufficient power is available to sustain operation of the refrigeration system in the economized mode.