High-efficient central chiller plant system with variable load by phase change material thermal energy storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Central chiller plant systems face inefficiencies under partial loads, as their COP (Coefficient of Performance) is maximized only within a narrow range of 40%-60% load, and most operational time is spent outside this range, leading to suboptimal refrigeration efficiency.
Innovation Solution
A high-efficient central chiller plant system utilizing phase change material thermal energy storage, which connects the refrigeration unit with phase change thermal energy storage to manage energy storage and release through flow and pressure control, allowing the system to operate efficiently across varying loads by storing energy during low demand and releasing it during high demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the refrigeration unit operates under partial load to match variable cooling demand, then the system adapts to actual usage requirements, but the COP (Coefficient of Performance) decreases significantly as operation moves away from the optimal 40%-60% load range
Solution Approach 1:
The phase change thermal energy storage system stores cooling energy in advance during low-demand periods when the refrigeration unit operates at optimal load (40%-60%). The PCM absorbs and stores thermal energy during off-peak hours, preparing cooling capacity before the peak demand period begins. This allows the refrigeration unit to maintain high COP by operating continuously at optimal load rather than cycling at variable partial loads.
Solution Approach 2:
The phase change material (PCM) acts as an intermediary energy storage medium between the refrigeration unit and the cooling load. The PCM absorbs excess cooling energy during low-demand periods and releases it during high-demand periods, decoupling the refrigeration unit operation from the variable cooling demand. This intermediary storage system enables the refrigeration unit to operate at constant optimal load while meeting variable cooling requirements.
2Use of energy by moving object
If the refrigeration unit operates at full load to maximize COP, then energy efficiency is optimized, but the system cannot meet variable cooling demands and operates inefficiently during most of the year
Solution Approach 1:
The system performs preliminary cooling energy storage during off-peak hours when cooling demand is low. The PCM thermal energy storage system accumulates cooling capacity in advance, allowing the refrigeration unit to operate at full or optimal load during these periods. This pre-stored energy is then discharged during peak demand periods, eliminating the need to reduce refrigeration unit load and maintain high COP throughout the year.
Solution Approach 2:
The refrigeration unit operates continuously at optimal load (40%-60%) rather than cycling on and off or varying its load to match demand. The PCM thermal energy storage system ensures continuous useful action by absorbing excess cooling during low-demand periods and supplementing cooling during high-demand periods, allowing the refrigeration unit to maintain steady-state optimal operation without interruption or load variation.
3Use of energy by moving object
If variable speed motors are used to improve COP under partial loads, then efficiency is enhanced within the 40%-60% load range, but the system still cannot achieve best results when operating outside this interval for most of the year
Solution Approach 1:
The PCM thermal energy storage system serves as an intermediary that compensates for the limited load range of variable speed motors. While the variable speed motor optimizes refrigeration unit performance within 40%-60% load, the PCM storage system handles the variable demand outside this range by storing or releasing cooling energy, allowing the combined system to achieve high efficiency across all load conditions, not just the narrow optimal range.
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 enhances energy efficiency by maintaining high COP across variable loads, saving energy by up to 40%-70% and reducing operational costs by optimizing refrigeration unit operation based on usage statistics, while simplifying the design and reducing maintenance needs.
Implementation Method 1
the chilled water in the first chilled water pipeline flows into the phase change thermal energy storage to make phase change of the phase change material for energy storage
Implementation Method 2
the phase change thermal energy storage for storage or release of energy
Implementation Method 3
the chilled water in the first chilled water pipeline flows into the phase change thermal energy storage to make phase change of the phase change material for energy storage
Data Source
AI summary
A high-efficient central chiller plant system with variable load by phase change material thermal energy storage includes a refrigeration unit and a phase change thermal energy storage. The refrigeration unit operates under the highest COP. If the refrigerating output is higher than the demand of cooling load, the phase change thermal energy storage stores energy by the phase change. Contrarily, if the refrigerating output cannot meet the demand of cooling load, the phase change thermal energy storage releases energy to supply the insufficient cooling load of the refrigeration unit. So that users can set the operation strategy of the refrigeration unit according to the usage statistics, and let the refrigeration unit operate efficiently with the cooperation of the phase change thermal energy storage, thereby effectively improving the energy efficiency of the system operation to save energy. Compared with the existing central chiller system, it saves energy more than 40%-70%.