Tandem Compressor EEV Control for Low-Energy Data Center Cooling
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Solution Overview
Problem
Current data center cooling systems are inefficient, consuming at least half of the power used in a typical data center, with a focus on improving energy efficiency becoming increasingly important due to the high energy consumption by cooling and power conversion systems.
Innovation Solution
A high efficiency cooling system is introduced, featuring staged cooling with multiple cooling circuits arranged serially, including a DX cooling circuit and a pumped refrigerant economizer mode that bypasses the compressor when outdoor temperatures are low, utilizing a controller to manage the operation between direct expansion and economizer modes to optimize energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a traditional DX cooling system operates continuously with compressor, then cooling capacity is maintained, but energy consumption increases significantly
Solution Approach 1:
The system dynamically switches between two operational modes: DX mode (compressor + liquid pump) for high cooling demand, and economizer mode (liquid pump only) for low cooling demand. This dynamic operation allows the system to adapt to varying cooling loads and minimize energy consumption by using the more efficient economizer mode whenever possible while maintaining adequate cooling capacity.
Solution Approach 2:
The system changes the operational parameters by bypassing the compressor during economizer mode when outdoor temperatures are favorable. This parameter change allows refrigerant to be circulated and cooled without compression, significantly reducing energy consumption while still providing cooling capacity through the liquid pump and heat exchangers.
2Productivity
If compressor operates at full capacity, then cooling demand is met, but energy efficiency decreases
Solution Approach 1:
The system uses partial action by operating the liquid pump in both DX and economizer modes, but only operating the compressor in DX mode. This partial operation of the compressor (rather than continuous full-capacity operation) reduces energy consumption while the liquid pump continues to provide necessary refrigerant circulation and cooling capacity.
Solution Approach 2:
The liquid pump serves as an intermediary component that maintains refrigerant circulation in both operational modes. During economizer mode, the liquid pump becomes the primary driver, allowing the system to meet cooling demand without the high energy consumption of the compressor, thus mediating between full compressor operation and complete compressor shutdown.
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 energy consumption by minimizing compressor power usage and optimizing cooling capacity, achieving significant energy efficiency gains, with annual energy efficiency increases of up to 53% in colder climates.
Implementation Method 1
the compressor is on and compresses a refrigerant in a vapor phase to raise its pressure and thus its condensing temperature
Implementation Method 2
the liquid pump is on and pumps the refrigerant in a liquid phase and refrigerant is circulated around the cooling circuit by the liquid pump
Implementation Method 3
a condenser, a compressor, an expansion device and a liquid pump... Heat rejection device 124 that provides cooled liquid to CRACs 116. Heat rejection device 124 is a device that transfers heat from the return fluid from CRACs 116 to a cooler medium
Data Source
AI summary
A cooling system has a tandem compressor, a condenser, an electronic expansion valve and an evaporator arranged in a direct expansion cooling circuit. The tandem compressor includes a variable capacity compressor and a fixed capacity compressor. A controller controls the electronic expansion valve and selects which of a plurality of superheat control modes to use in operating the electronic expansion valve based on control parameters and a current operating status of each of the variable capacity compressor and fixed capacity compressor of the tandem compressor.