Time-Based Safe Mode for Freecooling Chiller Control
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Solution Overview
Problem
Multi-mode chiller systems in data centers face inefficiencies due to reliance on temperature sensors, which can fail, causing them to default to less efficient direct refrigeration even when freecooling conditions are suitable, leading to increased energy and water consumption.
Innovation Solution
A controller device that monitors ambient and return water temperatures to determine threshold conditions for engaging freecooling, and switches to a time-based safe mode if sensors fail, allowing the system to alternate between direct refrigeration and freecooling based on user-configured parameters, ensuring continuous efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the chiller system relies on temperature sensors to determine when to switch to freecooling mode, then energy efficiency is improved, but system reliability deteriorates when sensors fail
Solution Approach 1:
The system performs preliminary actions by pre-configuring time-based safe mode parameters before sensor failure occurs. When sensor failure is detected, the controller immediately switches to time-based safe mode using pre-set configuration parameters, ensuring continuous operation without waiting for sensor repair. This preliminary preparation resolves the contradiction by providing a reliable fallback mechanism that maintains energy efficiency goals even when sensors fail.
Solution Approach 2:
The controller acts as an intermediary between the temperature sensors and the cooling system operation. It monitors sensor status and mediates the transition between sensor-based control and time-based safe mode. This intermediary function ensures that system reliability is maintained by detecting sensor failures and automatically switching to alternative control mechanisms, while still pursuing energy efficiency through freecooling when conditions permit.
2Reliability
If the chiller system defaults to direct refrigeration when sensor failure occurs, then system reliability is maintained, but energy efficiency deteriorates
Solution Approach 1:
The system applies dynamics by making the control mode adjustable based on real-time conditions. Instead of a static default to direct refrigeration, the controller dynamically switches between sensor-based freecooling control and time-based safe mode, and can modulate the balance between freecooling and direct refrigeration based on ambient temperature conditions. This dynamic approach maintains reliability through safe mode while optimizing energy efficiency by utilizing freecooling when ambient temperatures are favorable.
Solution Approach 2:
The system changes operational parameters by switching from sensor-based temperature threshold control to time-based configuration parameter control. In time-based safe mode, the controller uses pre-configured time parameters to determine when to engage freecooling versus direct refrigeration. This parameter change allows the system to maintain reliability through structured fallback behavior while preserving energy efficiency by still attempting freecooling operation when conditions permit, rather than defaulting entirely to less efficient direct refrigeration.
3Productivity
If the chiller system uses temperature sensors to detect freecooling conditions, then cooling efficiency is improved, but device complexity increases due to sensor monitoring requirements
Solution Approach 1:
The system extracts the essential control function from the temperature sensors themselves. Instead of relying solely on sensor-based temperature threshold comparison, the controller separates the sensing function from the decision-making function. In time-based safe mode, the controller uses time-based configuration parameters rather than continuous temperature sensor data to make cooling decisions. This extraction reduces the complexity of sensor monitoring while maintaining cooling efficiency through alternative means.
Solution Approach 2:
The system applies self-service by having the controller monitor its own operational status and automatically switch to safe mode when sensor failures are detected. The controller serves its own diagnostic and protective functions, eliminating the need for additional complex monitoring systems. This self-service approach maintains cooling efficiency by automatically adapting to sensor failures without requiring external intervention or complex additional hardware.
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 solution enables the chiller system to maintain energy efficiency and reduce water consumption by automatically switching to freecooling when conditions are favorable, even if temperature sensors fail, thereby preserving uninterrupted cooling functionality.
Implementation Method 1
air is driven (e.g., by fans) through the coil to transfer heat from the air to the chilled water
Implementation Method 2
air is driven (e.g., by fans) through the coil to transfer heat from the air to the chilled water
Implementation Method 3
the FC directs ambient air over the water loop via a fan, without mechanical refrigeration
Implementation Method 4
the DX system may be the default chiller subsystem, cooling the water loop via a full refrigeration cycle
Data Source
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AI summary
A system and method for time-based safe mode operation of a multi-mode chiller device incorporating a freecooling system and a direct refrigeration system (e.g., wherein a fluid loop is circulated between the chiller device and a data center or similarly sensitive environment, from which the chilled water transfers heat before returning to the chiller device) senses ambient air temperatures outside the data center environment and return water (RW) temperatures (e.g., of water returning to the chiller from the environment) and engages the freecooling system based on a difference or delta between ambient and RW temperatures. If either the RW or ambient temperature sensors fail, preventing the freecooling system from engaging automatically, time-based safe mode is engaged wherein the freecooling and direct refrigeration systems are alternately engaged according to configuration time parameters adjustable by a user.