Life cycle inventory and performance analysis of phase change materials for thermal energy storages

Abstract

Solar energy is a renewable energy that requires a storage medium for efective usage. Phase change materials (PCMs) successfully store thermal energy from solar energy. The material-level life cycle assessment (LCA) plays an important role in studying the ecological impact of PCMs. The life cycle inventory (LCI) analysis provides information regarding the material and energy requirements and economy of PCMs. This work presents an estimated LCA and LCI values in order to reveal all the mentioned efects of PCMs on storing thermal energy generated by concentrated solar thermal power plants. The goal of this study was to provide guidance for PCM system design based on a matrix that considers the performance, costs, and environmental impact. The ecoinvent global database (version 3) was used for the life cycle inventory analysis. For this study, PCMs were selected based on physical and chemical properties as well as state and melting temperatures (300–500 °C) that are suitable for charging and discharging a large amount of thermal energy. The performance of PCMs was determined based on their thermal efusivity. Results indicate that compared to other PCMs, sodium nitrate (100%) used less heat energy, but when comparing the amount of electricity usage for PCM compounds, potassium nitrate (65.31%)+potassium carbonate (34.69%) used less electricity. From the emissions data for PCMs from raw materials to factory gate (cradle-to-gate), Na2CO3 produced the lowest emissions to air, although harmful emissions to water. The performance of PCM mixtures was better, with thermal conductivity almost 3.5 times higher than that of individual PCMs. However, the cost of PCM mixtures was three times higher than that of individual PCMs. This comprehensive compilation of PCM data can be very helpful in the selection of a suitable PCM while ofering a fne balance between cost and performance.