Long-Term Performance Evaluation of BTU Metering under Seasonal & Low-Load Conditions in District Cooling Systems: A Before-and-After Pilot Study

Abstract

District Cooling Systems (DCS) are increasingly adopted in smart urban developments to improve energy efficiency, reduce greenhouse gas emissions, and provide centralized cooling for commercial and residential buildings. Accurate thermal energy measurement through Building Thermal Unit (BTU) meters is fundamental for energy billing, operational optimization, and system performance assessment. However, BTU meter performance is often affected under seasonal low-load operating conditions, where reduced chilled water flow rates and diminished temperature differences (ΔT) introduce measurement uncertainties and compromise energy accounting.
This paper presents yearly operational trend analysis of BTU meter performance using data collected from two representative commercial buildings connected to a large-scale district cooling network. To preserve operational confidentiality, the monitored facilities are referred to as Case Study Building A and Case Study Building B. Historical operational data including chilled water flow rate, supply temperature, return temperature, ΔT, cooling energy, and meter diagnostics were analyzed.
The results demonstrate that seasonal variations & low load in system significantly influence BTU meter accuracy. During low-load periods, flow & ΔT degradation of up to 35% was observed, accompanied by reduced flow velocity and increased measurement uncertainty. Statistical analysis indicates a strong correlation between flow rate reduction and thermal energy measurement deviation. The findings further reveal that proactive pilot measurement strategies, periodic calibration, optimized sensor placement, and continuous SCADA-based monitoring substantially improve metering reliability under varying operating conditions.
The study provides practical recommendations for district cooling utilities seeking to enhance thermal energy measurement accuracy, improve operational efficiency, and support long-term energy sustainability.