A review of borehole thermal energy storage and its integration into district heating systems

Abstract

Environmental friendly thermal energy storage (TES) solutions are gaining ground throughout the world. Many novel options, such as utilizing solar radiation collectors, reusing the waste heat of shopping malls and data centers, and recycling the waste heat produced in cooling towers, are considered for TES by many countries. The usual issue with these types of thermal energies is the time gap between energy production and energy consumption. Eliminating this time mismatching has resulted in TES solutions such as tank thermal energy storage, pit thermal energy storage, aquifer thermal energy storage, and borehole thermal energy storage (BTES). The BTES needs fewer environmental considerations than aquifer thermal energy storage, has lower initial costs compared to long-term tank and pit thermal energy storage, and has been widely accepted as a solution. This study initially introduces different TES methods and the district heating and cooling (DHC) generations. Furthermore, it reviews the BTES technology, including its design considerations, environmental, and economic aspects, and its combination into DHC networks. This study found that the integration of BTES into DHC decreases the system temperature and increases its efficiency, which is vital in low-temperature 5th-generation DHC. Additionally, it highlights the adverse effects of the BTES system, such as induced instability and settlement in subsurface soil layers and thermal contamination. The accurate system design, considering the uncertainties, helps the economic viability of the technology, which is essential to convince the users, stakeholders, and policy makers.