Techno-economic comparison of cold storage configurations for summer air conditioning of high-risk commercial buildings

Abstract

This research investigates the application of thermal energy storage (TES) systems for air conditioning in office buildings located in tropical climates with high cooling demands. While integrating cold storage systems with air conditioning offers benefits such as reduced peak demand electricity costs, the ability to leverage the electricity demand to get time- based electricity tariff benefits, enhanced chiller plant efficiency, and improved condenser performance during nighttime operation, the adoption of TES technology remains limited. This is primarily due to the lack of comprehensive assessments and cost analysis related to local electricity tariff structures in various regions. The study provides guidelines and a decision-making tool for selecting the most suitable thermal energy storage (TES) system for buildings, with a focus on load-shifting strategies to off-peak hours. It includes a literature survey to explore the fundamentals and characteristics of thermal storage systems and media for air conditioning, review software tools for cooling load calculations and system simulations, and investigate cost analysis methods and applicable electricity tariff structures for high cooling demand buildings in tropical climates. Following this, the report presents a detailed examination of TES integration with chiller plants, assessing various configurations based on factors such as energy consumption, maximum demand variations, daily energy distribution, space requirements, and implementation costs. Among the four configurations assessed, including a conventional chiller plant, a chiller plants with TES for full capacity (full storage), and two configurations with partial TES for load leveling and demand limiting, the configuration 2-2, which uses TES for partial storage-load leveling, was found to be the most cost-effective. This configuration demonstrated substantial operational savings, reduced peak demand, and required minimal space. Payback periods for Configuration 2-2 varied by region: approximately 14 years under Sri Lanka’s July 2024 electricity tariffs, 3.28 years under Sri Lanka’s August 2022 tariffs, 1.49 years under Singapore’s current tariffs, and 6.21 years under Kerala, India’s current tariffs. The extended payback period under Sri Lanka’s latest tariffs is attributed to the reduction of the differences among daytime, peak, and off-peak electricity rates. Despite this, Configuration 2-2 remains financially favorable compared to other tariff structures evaluated