In this study, the performance of a ground heat exchanger (GHE) for domestic hot water loads was evaluated using an FLS (Finite Line Source) model with various configurations. The evaluation compared two scenarios: using the GHE alone and using a hybrid system combining the GHE with solar thermal modules, operated in both group and individual modes. The results indicated a continuous decrease in ground temperature when only the GHE was used. However, in the group/individual operation modes, the ground temperature showed a slight decrease but maintained a more stable level. Over a long-term operation of 20 years, the hybrid group/individual operation with solar thermal modules showed that the average temperature of the fluid discharged from the GHE was approximately 0.7℃ higher than when only the GHE was used. Providing a higher temperature fluid on the heat source side suggests the potential to improve the COP (Coefficient of Performance) of the heat pump. Moreover, the proposed hybrid group/individual operation mode demonstrated the ability to mitigate ground temperature imbalances caused by load imbalances, and confirmed the possibility of reducing the number of GHE installations by half, thereby lowering initial investment costs. In conclusion, the simulation verified that the group/individual operation mode utilizing hybrid heat sources is an effective alternative for enhancing the performance and cost-efficiency of ground source heat pump systems.

Energy efficiency of a smart farm was investigated through TRNSYS simulation. We evaluated the economic feasibility, and derived the optimal operating conditions for the Eumseong smart farm's air conditioning system. Comprehensively, we analyzed the effects of regional climate conditions, the thickness of the glass insulation layer, and the installation of the sunshade on the energy consumptions and smart farm's temperature. Besides, the economic feasibility of the heating system was evaluated. The total annual energy consumption of Changwon smart farm decreased by 11% compared to that of the Eumseong region, and the annual energy consumption of Cheolwon smart farm increased by 3% compared to that of the Eumseong region. The inside temperature of the smart farm where the sunshade was applied, decreased by about 10% compared to the temperature without sunshade, and it was confirmed that a total of 1,955,855 kJ of cooling energy in the summer can be saved. When the air layer thickness of double-layer glass was increased from 5 mm to 10 mm, the total annual energy consumption decreased by 17% and heating electricity bills decreased by 14.7%. The system utilizing an electric boiler can reduce energy consumption by more than 14% per year compared to a system using a diesel boiler, and an electric boiler system can reduce energy consumption by 12.7% per year compared to a system using a diesel boiler.

The Government the Republic of Korea is showing a lot of interest in net zero-energy buildings (NZEBs) to reduce energy consumption of buildings and to promote green growth policy in construction sector. The application of building passive technologies and renewable energies is essential to achieving NZEBs. Green remodeling reinforced the insulation of the exterior walls and roofs of the buildings and replaced high-efficiency windows and doors. In this study, the energy performance before and after green remodeling applied in a senior citizens' center was comparatively analyzed for baseline case and three different cases, Case-A, Case-B and Case-C. A building modeling software (DesignBuilder V7.0) with EnergyPlus (V9.4) calculation engine was used to evaluate the energy demand and energy consumption of each case. Based on the simulation results of the building's energy demand for baseline, it was determined that the target building required more heating energy than cooling energy. The simulation results also showed that the implementation of building envelope performance improvement technologies (Case-A) could notably decrease the heating energy consumption of the building. After the remodeling (Case-A), the source energy consumption per unit floor area was assessed to be reduced by 61.8%, compared to prior remodeling of 363.9 kWh/m²-y. Meanwhile, Case-B can achieve energy savings of 59.4% and Case-C can achieve savings of 63.2%. Following completion of the remodeling project, actual construction costs, and on-site measurements and verification results will be gathered and compared with the simulation results. Additionally, economic analysis including construction costs and payback period will be conducted using actual site data.