Feasibility of low-temperature district heating with decentralized substations in Korean apartment buildings: Analysis of heat loss, energy efficiency, and return temperature optimization

This study investigates the feasibility and potential benefits of implementing low-temperature district heating (LTDH) with decentralized substations (DS) in Korean apartment buildings. By incorporating successful international cases and comparing them with the Korean context, a comprehensive analysis of heating and domestic hot water (DHW) consumption patterns, along with a detailed simulation study using the TERMIS software, was conducted to assess the heat loss reduction potential and energy efficiency improvements achievable through LTDH. The case study building, located in Goyang, South Korea, was equipped with DS and monitored for one year using advanced metering infrastructure (from April 2021 to March 2022). The simulation model was validated using measured data from the existing high-temperature district heating (HTDH) system with DS, showing a close agreement with a CV(RMSE) of less than 5 %. The performance of the LTDH system was evaluated under different supply temperature scenarios (specifically at 60 degrees C, 55 degrees C, and 50 degrees C), revealing that reducing the supply temperature led to significant reductions in annual heat losses, with 4.8 % and 8.9 % reductions achieved at 55 degrees C and 50 degrees C, respectively. These temperature levels were selected based on international standards for Legionella prevention and optimal LTDH operation. The analysis of return temperatures from the upper floors demonstrated the potential of LTDH in mitigating the heat loss effect and improving system efficiency, particularly during the summer months. An economic analysis was also conducted, highlighting the cost-effectiveness of LTDH implementation in the Korean context. The study highlights the importance of considering the specific characteristics of Korean apartment buildings and optimizing return temperatures when implementing LTDH. The findings provide valuable insights for building owners, district heating providers, and policymakers to support the transition towards sustainable and energy-efficient heating systems in the Korean building sector.