Central Plant HVAC Control Using Stranded Node Analysis
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Solution Overview
Problem
Conventional methods for predicting thermodynamic states and determining operating parameters in complex HVAC systems are inefficient in terms of computational resources, making it exhaustive to predict states for multiple sets of operating parameters and compare power consumptions.
Innovation Solution
A central plant controller uses stranded node analysis to determine schematic relationships among HVAC devices, reducing the number of devices and states to be predicted, by identifying and excluding or adding devices based on their dependencies, and generating an incidence matrix to optimize the prediction of thermodynamic states and operating parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional non-linear solver is used to predict thermodynamic states for multiple candidate sets of operating parameters, then prediction accuracy is maintained, but computational resources (processor usage and memory) are excessively consumed
Solution Approach 1:
The system segments the HVAC system into independent subplants (e.g., cooling subplant, heating subplant, thermal energy storage subplant). Each subplant is analyzed separately to determine its operational status and dependencies, reducing the overall computational burden while maintaining prediction accuracy for each segment.
Solution Approach 2:
The system extracts and identifies stranded nodes (nodes with only one connection) and their associated dependent HVAC devices from the full system model. By removing these dependent devices from the prediction calculation and determining their states based on the operational status of independent devices, the computational scope is reduced without sacrificing accuracy for the independent subsystems.
2Reliability
If full thermodynamic states of all HVAC devices are predicted for multiple candidate sets of operating parameters, then complete system analysis is achieved, but computational time and resources increase exhaustively
Solution Approach 1:
The system performs preliminary analysis to identify stranded nodes and dependent HVAC devices before the main prediction process. By pre-determining which devices are dependent on others and should not be independently predicted, the system avoids redundant computations while ensuring complete system analysis through dependency tracking.
Solution Approach 2:
The system performs partial prediction only for independent HVAC devices rather than all devices. The states of dependent devices are derived from the independent devices' operational status, achieving complete system analysis with reduced computational effort by performing action only where necessary.
3Ease of operation
If all HVAC devices are included in thermodynamic state prediction, then comprehensive operating parameter determination is achieved, but computational complexity increases
Solution Approach 1:
The system applies different treatment to different parts of the HVAC system: independent devices undergo full thermodynamic state prediction while dependent devices (connected to stranded nodes) have their states determined locally based on the operational status of independent devices. This localized approach reduces overall computational complexity while maintaining comprehensive operating parameter determination.
Data Source
AI summary
Disclosed herein are related to a system, a method, and a non-transitory computer readable medium for operating an energy plant. In one aspect, a system determines schematic relationships of a plurality of heat, ventilation, and air conditioning (HVAC) devices of the energy plant based on connections of the plurality of HVAC devices. Each HVAC device is configured to operate according to a corresponding operating parameter. The system determines, from a plurality of HVAC devices, a reduced subset of the HVAC devices based on the schematic relationships. The system predicts thermodynamic states of the reduced subset. The system determines a set of operating parameters of the plurality of HVAC devices based on the thermodynamic states. The system operates the plurality of HVAC devices according to the set of operating parameters.