A new integrated modeling and initial commissioning technology have been investigated to introduce and disseminate a more energy and cost efficient way of CO₂ free GSHP (Ground Source Heat Pump) heating and cooling system for multi-family residential applications. A system modeling of key components such as heat pump, ground heat exchanger and a heat exchanger inside a RWST (Rain Water Storage Tank) for a multi-family building has been conducted and expressed as mathematical equations with EES (Engineering Equation Solver) tool and would be validated with a 10 kW (3RT) lab scale system Integral Effect Test (IET). Key results indicated that the effect of the rain water temperature on cooling and heating capacity could be visualized and also a heat pump performance data based commissioning technology could enhance the credibility of the complex integrated system properly as predesigned intentionally. This new integrated concept of a GSHP with RWST for the multi-family residential building could be the one of solutions for the CO₂ free energy issues for Seoul and major cities and communities expecting more clean energy societies.

Pump in HVAC systems are directly linked to pump and heat source energy, making them critical for energy savings. Typically, pumps operate at maximum speed to meet peak load conditions, leading to excessive energy consumption under partial load. Accurate flow measurement is essential for optimal pump operation, but physical sensors have limitations due to high costs, installation constraints, and space requirements. This study develops and validates a virtual flow meter using pump performance curves, heat exchange, and pressure-power theories with field data. The study developed virtual flow meters based on pump performance curves, heat exchange, and pressure-power theories. Results confirmed that the virtual flow meter using the pump performance curve theory achieved the highest accuracy.

Energy efficiency improvements in refrigeration systems are major issues to addressing rising energy consumption and environmental concerns. In this study, the performance of an electronic expansion valve (EEV) system with nozzle were experimentally investigated by evaluating its cooling capacity, power consumption, and coefficient of performance (COP). Three different nozzle diameters (0.8 mm, 1.0 mm, and 1.2 mm) were installed downstream of the EEV, and the system's performance was compared with a conventional EEV only system. Experiments were performed under controlled conditions at ambient temperature, varying the EEV opening rates from 10% to 100%. The results showed that the system with a 1.0 mm nozzle achieved the highest cooling capacity (1456.7W) and coefficient of performance (COP of 2.35), along with an improved minimum COP of 2.00, indicating stable and enhanced efficiency. In the case of the 1.0 mm nozzle, choked flow occurred at an opening ratio of 80%, limiting mass flow rate increases. On the other hand, the 0.8 mm and 1.2 mm nozzles and the EEV only system showed peak mass flow rates at 20~40% valve openings. Overall, the application of nozzles contributed positively to refrigerant flow control and heat exchange efficiency.

Recently, The rapid growth of the global population and energy-intensive industries has significantly increased energy demand, raising concerns about energy supply management and grid stability. The rising electricity consumption is straining power grids, heightening the risk of blackouts and disruptions in energy distribution. Additionally, these challenges contribute to persistent fluctuations in global energy markets and increasing costs. Consequently, energy conservation has become a critical priority, reinforcing the necessity of renewable energy as a sustainable alternative. In response, governments worldwide are actively developing and refining regulatory frameworks to facilitate a transition toward more resilient and sustainable energy systems. In South Korea, regulatory improvements are also being implemented, with the Zero Energy Building (ZEB) certification system and the Renewable energy supply obligation for public institutions playing significant roles in promoting renewable energy adoption. However, the required installation capacity differences between these two policies have caused confusion among practitioners. Therefore, this study aims to contribute to the improvement of evaluation criteria by conducting a comparative analysis of renewable energy installation capacity between the two systems.