SE-99-16-2 -- Evaluating the Uncertainty in Cool Storage Inventory Using an Energy Balance Method ✓ Most Recent

Instrumentation was installed at a large convention hotel in San Francisco to monitor the performance of the chilledwater plant with cool storage. The instrumentation was intended to provide the basis for evaluating advanced control technology, including real-time optimization of the plant, electricity price-based control, and enhanced scheduling. These capabilities were to be incorporated into a new building management system, which would also provide performance monitoring and data management. Fundamental to performance optimization of a chilled-water plant with cool storage is the need to know the state of charge or storage inventory (sensible and latent) of the cool storage system. Both instrument error and storage standby loss offer potential impediments to balancing thermal flows over any given storage charge/discharge cycle or series of cycles. In this project, we attempted to measure storage inventory using accurate instrumentation familiar in the HVAC environment while employing proper installation and advanced field calibration techniques. We utilized a series of tests along with an uncertainty analysis in an attempt to evaluate what error tolerance is required to maintain a predictable measure of present and future inventory levels. In this paper, we examine what influences the uncertainty in the storage inventory calculation, evaluating both theoretical possibilities and the as-measured conditions. We also compare measured results with that of factory-supplied ice capacity transmitters.

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