Author(s)

TADAS ZDANKUS, SHAMAIMA WAFA QAMMAR

Abstract

Space heating in northern countries accounts for a large share of total energy consumption and a significant portion of this heat is still produced by burning fossil fuels in individual heating systems or in district heating cogeneration plants. Therefore, greater attention is being paid to solutions that enable more efficient energy use and allow renewable heat produced in one season to be utilised in another. Seasonal ground thermal energy storage is one approach that can help balance the mismatch between heat production and demand while reducing environmental impacts associated with conventional heating. This study investigates the possibility of generating heat with solar collectors during the warm season and storing it in an underground seasonal thermal energy storage system for later use in building heating. The simulated and analysed case was a high-energy-efficiency single-family residential building representing a typical detached house. The building’s annual space–heating demand was estimated using climatic data representative of Lithuanian conditions. An underground thermal energy storage volume beneath the building was considered for seasonal heat storage. To store sufficient thermal energy, the average soil temperature during the charging period was increased to approximately 40–45°C. Because large temperature gradients can occur near the heat exchangers’ pipes, soil heat distribution is an important factor affecting storage performance. Laboratory experiments were conducted to examine whether heat dissipation in the soil could be improved using natural materials. Stones were added to the gravelly sand backfill at a concentration of 10–15% by mass. The results showed that this modification improved heat dissipation compared with gravelly sand alone, leading to a more uniform temperature distribution and more effective charging of the seasonal heat storage volume.

Keywords

seasonal energy storage, heat, building heating, soil thermal conductivity, dissipation