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POWER ENGINEERING: economics, technique, ecology
ISSN 1813-5420 · e‑ISSN 2308-7382 Open Access · CC BY 4.0
Vol. · Issue 3 · 2026 Oct 12, 2026 ENERGY EFFICIENCY AND ENERGY SAVINGS

DYNAMIC ENERGY EFFICIENCY MODEL OF A SOLAR HEAT SUPPLY SYSTEM WITH SEASONAL BOREHOLE THERMAL ENERGY STORAGE

KS
Kirill Slizhevskyi Corresponding National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute», Ukraine
OC
Olha Chernousenko National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute», Ukraine
ON
Olexander Nedbailo National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute», Ukraine
Pages149-158 PublishedOct 12, 2026 LicenseOpen Access
PDF (Ukrainian)
VOL · ISS 3 · 2026 85 View issue

Abstract

The growing demand for decarbonization of heat supply systems necessitates the development of efficient technologies for long-term thermal energy storage. One of the most promising solutions is Borehole Thermal Energy Storage (BTES), which enables seasonal accumulation of excess solar heat and its utilization during periods of increased demand. The aim of this study is to investigate the thermal behavior of a BTES system operating under the climatic conditions of Ukraine using a two-dimensional axisymmetric numerical model of transient heat transfer in a soil mass.

The mathematical model is based on the transient heat conduction equation in cylindrical coordinates and is solved using an explicit finite-difference scheme. The borehole field is represented by an equivalent distributed heat flux applied to the upper boundary of the computational domain. Numerical simulations were performed for a cylindrical BTES with a radius of 15 m and a depth of 30 m using measured annual solar radiation data. Model verification demonstrated good agreement with published literature results.

The obtained results revealed a pronounced seasonal thermal response of the storage system. It was established that the maximum temperature within the central part of the storage volume occurs approximately 1–1.5 months after the peak solar radiation, reflecting the thermal inertia of the surrounding soil. For the reference configuration, the annual heat input to the storage reached 143.6 MWh, while the thermal utilization coefficient of the storage was approximately 78%. The verification results confirmed consistency between the numerical predictions and independent literature data. The influence of geometric parameters on the thermal performance of the storage system was also investigated.

The results demonstrate the applicability of the proposed model for engineering prediction of thermal processes in BTES-based solar heating systems. The developed approach can be used for the design and optimization of seasonal thermal energy storage systems under Ukrainian climatic conditions.

Keywords

#Borehole Thermal Energy Storage (BTES) #solar heat supply #seasonal thermal energy storage #transient heat conduction #axisymmetric numerical model #soil temperature field #finite-difference method #thermal energy storage #renewable heat

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Copyright (c) 2026 Кирило Сліжевський, Олександр Недбайло, Ольга Черноусенко

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