Tandem Compressor System for Low-Load HVAC Efficiency Without Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
HVAC systems with variable-speed compressors face inefficiencies due to the need for repeated on/off cycles during low cooling or heating loads, as they cannot maintain desired environmental conditions, leading to increased energy consumption.
Innovation Solution
A tandem compressor system comprising a fixed-speed compressor and a variable-speed compressor, where the two work in tandem to match load demands by modulating their operation based on detected cooling or heating loads, using suction and oil equalization lines, and control algorithms to optimize compressor usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a variable-speed compressor is used to improve efficiency, then energy consumption is reduced during high load periods, but the compressor cannot maintain desired environmental conditions during low load periods and requires repeated on/off cycling
Solution Approach 1:
The compressor system is divided into two independent compressors: a variable-speed compressor and a fixed-speed compressor. Each compressor can operate independently or in combination, allowing the system to segment the cooling load between two units. This segmentation enables the fixed-speed compressor to provide a stable baseline cooling capacity while the variable-speed compressor handles modulation, eliminating the cycling problem of the single variable-speed compressor during low load periods.
Solution Approach 2:
The patent combines a variable-speed compressor and a fixed-speed compressor into a single hybrid compressor system. The two compressors work together to provide a wider range of cooling capacities, merging the advantages of both types: the energy efficiency and modulation capability of the variable-speed compressor with the stable continuous operation capability of the fixed-speed compressor. This combination allows the system to maintain desired environmental conditions during low load periods while still achieving energy savings during high load periods.
2Adaptability or versatility
If a variable-speed compressor operates in repeated on/off cycles during low load periods, then it can adapt to small cooling loads, but this cycling introduces further inefficiencies and increases energy consumption
Solution Approach 1:
The fixed-speed compressor provides continuous operation during low load periods, eliminating the on/off cycling of a single variable-speed compressor. By running the fixed-speed compressor continuously at a steady state and using the variable-speed compressor to handle only the necessary modulation, the system maintains continuous useful action without the energy losses associated with repeated startup and shutdown cycles.
Solution Approach 2:
During low load periods, the fixed-speed compressor operates at a capacity that may be slightly excessive for the actual cooling demand, but this partial operation is more efficient than complete cycling. The variable-speed compressor complements this by operating at reduced speed to provide only the necessary additional capacity, rather than requiring the fixed-speed compressor to cycle on and off.
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A compressor system includes a variable-speed compressor and a fixed-speed compressor. A control unit is operatively coupled to the variable-speed compressor and is operatively coupled to the fixed-speed compressor. A sensor is operatively coupled to the control unit and disposed in an enclosed space. The sensor measures at least one of a temperature and a relative humidity of the enclosed space and determines an HVAC load of the enclosed space. Responsive to a determination of the HVAC load, the control unit directs operation of the variable-speed compressor and the fixed-speed compressor.