Performance Analysis of High Temperature Thermal Energy Storage: Case Sand Battery
Kumpulainen, Ville (2026)
2026
Automaatiotekniikan DI-ohjelma - Master's Programme in Automation Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2026-06-01
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202605316646
https://urn.fi/URN:NBN:fi:tuni-202605316646
Tiivistelmä
Energy storage systems are a key technology for flexibility in energy systems, bridging the time gap between intermittent energy production and varying demand. Heat represents the largest share of global energy consumption, particularly in industrial processes, where a significant portion of demand is used for temperatures above 150 degrees Celsius. Thus, high temperature thermal energy storage (HTTES) is an emerging solution which is being actively researched and developed.
To compare different thermal energy storage solutions, common performance indicators are required. In this work, HTTES systems based on solid materials and sensible heat were reviewed, together with the performance indicators used to evaluate them. Reliable performance evaluation requires accurate measurements. Thus, the most prevalent measurements used for the performance analysis, temperature and fluid flow measurements, were also reviewed briefly.
In this thesis, the performance of a recently commissioned HTTES was analyzed on the basis of operational data. The round trip efficiency and the discharging and charging power were analyzed. The mass flow rate of air circulating through the system was also estimated using four methods: heat exchanger energy balance, resistor energy balance, fan pressure difference and fan shaft power. As measurements inherently contain un certainty, the standard GUM uncertainty framework was used to evaluate the associated measurement uncertainties. To estimate the minimum uncertainty level, only measurement tolerances were considered as sources of uncertainty.
The round trip efficiency was determined to be 85 ± 2.2%, which is consistent with expected performance. Although data of extreme discharging and charging conditions were not found, existing data showed that discharging power exceeded design values by a clear margin while charging power exceeded design values slightly. The mass flow estimation was not conclusive, as none of the estimates showed strong agreement with each other and no validation data were available. Nevertheless, the resistor-based and shaft power-based estimates exhibited a strong monotonic relationship. The resistor-based estimate showed small uncertainties, while the fan-based uncertainties were evaluated to be large or very large.
An overview of the TES operation was also presented. The results suggest that a smaller air-circulation fan may be sufficient for discharging purposes and that the automation logic may not have been operating optimally during discharge. The measurements and instrumentation were also assessed qualitatively and recommendations for improvement were proposed.
To compare different thermal energy storage solutions, common performance indicators are required. In this work, HTTES systems based on solid materials and sensible heat were reviewed, together with the performance indicators used to evaluate them. Reliable performance evaluation requires accurate measurements. Thus, the most prevalent measurements used for the performance analysis, temperature and fluid flow measurements, were also reviewed briefly.
In this thesis, the performance of a recently commissioned HTTES was analyzed on the basis of operational data. The round trip efficiency and the discharging and charging power were analyzed. The mass flow rate of air circulating through the system was also estimated using four methods: heat exchanger energy balance, resistor energy balance, fan pressure difference and fan shaft power. As measurements inherently contain un certainty, the standard GUM uncertainty framework was used to evaluate the associated measurement uncertainties. To estimate the minimum uncertainty level, only measurement tolerances were considered as sources of uncertainty.
The round trip efficiency was determined to be 85 ± 2.2%, which is consistent with expected performance. Although data of extreme discharging and charging conditions were not found, existing data showed that discharging power exceeded design values by a clear margin while charging power exceeded design values slightly. The mass flow estimation was not conclusive, as none of the estimates showed strong agreement with each other and no validation data were available. Nevertheless, the resistor-based and shaft power-based estimates exhibited a strong monotonic relationship. The resistor-based estimate showed small uncertainties, while the fan-based uncertainties were evaluated to be large or very large.
An overview of the TES operation was also presented. The results suggest that a smaller air-circulation fan may be sufficient for discharging purposes and that the automation logic may not have been operating optimally during discharge. The measurements and instrumentation were also assessed qualitatively and recommendations for improvement were proposed.