Numerical Modelling and Performance Analysis of a Packed Bed Electric Thermal Energy Storage System Integrated with a Rankine Cycle
Author
Olesen, Jakob Nørregård
Term
4. term
Education
Publication year
2025
Submitted on
2025-05-28
Pages
69
Abstract
The shift to renewable energy makes effective storage essential to smooth out fluctuations in supply and demand. This thesis studies a packed-bed thermal energy storage (PBTES) system coupled to a Rankine cycle, a common steam-turbine process. We develop a one-dimensional, transient numerical model to track how temperatures and heat move during charging and discharging. The model is validated against reference data from a PBTES facility and reliably predicts system behavior. A parametric sensitivity analysis examines how particle size, mass flow rate, and void fraction (the empty space between particles) affect temperature distribution and pressure loss. To assess performance during discharge, both single-pressure and dual-pressure Rankine cycles are integrated with a heat recovery steam generator (HRSG), and thermal efficiency, power output, and round-trip efficiency (the fraction of stored energy recovered) are evaluated. Results show that a dual-pressure Rankine cycle improves heat recovery while maintaining a thermal efficiency of about 36%. Overall, the work demonstrates that a packed-bed storage system integrated with a Rankine cycle is a viable option for flexible, grid-scale energy storage.
Overgangen til vedvarende energi kræver effektiv lagring for at udjævne udsving i produktion og forbrug. Denne afhandling undersøger et pakket bed termisk energilager (PBTES) koblet til en Rankine-cyklus, som er en almindelig dampturbineproces. Vi udvikler en én-dimensionel, tidsafhængig (transient) numerisk model, der simulerer, hvordan temperaturer og varme transporteres under opladning og afladning af lageret. Modellen valideres mod referencedata fra et PBTES-anlæg og viser pålidelige forudsigelser af systemets adfærd. En parametrisk følsomhedsanalyse undersøger, hvordan partikelstørrelse, masseflow og hulrumsfraktion (andelen af tomt rum mellem partiklerne) påvirker temperaturfordeling og tryktab. For at vurdere systemets ydeevne under afladning integreres både enkelt-tryk og dobbelt-tryk Rankine-cyklusser med en varmegenvindingsdampgenerator (HRSG), og vi evaluerer termisk virkningsgrad, el-effekt og rundturseffektivitet (hvor stor en del af den lagrede energi der kan hentes tilbage). Resultaterne viser, at en dobbelt-tryk Rankine-cyklus forbedrer varmegenvindingen, samtidig med at den termiske virkningsgrad holdes omkring 36%. Samlet set demonstrerer afhandlingen, at et pakket bed varmelager integreret med en Rankine-cyklus er en realistisk løsning til fleksibel energilagring i stor skala.
[This apstract has been rewritten with the help of AI based on the project's original abstract]