Session: 02-03: HVAC System Analysis I

Paper Number: 138580

138580 - Enabling Electrification and Decarbonization of Buildings Using Air-to-Water Heat Pump Chiller 

Abstract: 

Buildings significantly contribute to global energy consumption and greenhouse gas emissions. Among various systems within buildings, heating, ventilation, air-conditioning systems are particularly important, as they account for approximately 20-40% of total energy consumption in the entire building. To effectively lower energy consumption and mitigate the environmental impacts, exploring alternative heating and cooling systems for building applications is crucial. Such exploration can not only enhance building energy conversion but also contributes to the global efforts in reducing the environmental footprint. This study evaluates electrification and decarbonization potential of air-to-water heat pump chiller system, a system which transfers heat from outside source (air) to inside sink (water) and vice versa in summertime, as a potential replacement for traditional condensing-type hot water boilers. The primary objective is to assess whether the heat pump chiller system can reduce carbon emissions while providing the necessary heating energy to multi-story office buildings across three California cities. The evaluation is carried out using the EnergyPlus building energy modeling tool by implementing a 420-ton (6×70 tons) heat pump chiller system in a 175,000-square-foot, 10-story office building in California climates (i.e., San Francisco, Los Angeles, and Sacramento). The DOE’s commercial reference building model (i.e., medium office building) is modified to establish a baseline building model for this study, and the alternative building model is then developed by replacing the original heating system, two 2,000 MBH, 95% efficiency condensing boilers, with a heat pump chiller (2.5 COP for heating) system. The modified models were simulated across various climate zones in California to evaluate hourly heating energy consumption and annual savings potential. Furthermore, the study examined the impact of part-load ratios (PLRs) and external air conditions on heating capacity and COP values to determine the proposed system's efficiency under diverse climatic conditions. Results highlight that the heat pump chiller system can achieve heating energy savings of around 60-70% compared to conventional condenser-type gas boilers. Additionally, this system was confirmed to reduce carbon emissions by average 13%. While the reduction in carbon dioxide emissions varies by climate zones, the potential for CO2 emission reductions is somewhat limited relative to the alternative heating energy savings due to different emission conversion factors for electricity (4.33 × 10-4 metric tons CO2/kWh) and natural gas (0.0053 metric tons CO2/therm). The results of this analysis indicate that implementing such innovative solutions in buildings can significantly mitigate the building energy sector's environmental impact and contribute to a more sustainable future.

Presenting Author: Dongsu Kim Hanbat National University

Presenting Author Biography: Dongsu Kim is a distinguished assistant professor in the Department of Architectural Engineering at Hanbat National University, located in the Republic of Korea. With a profound expertise in building energy system modeling and simulation, he has become a notable figure in his field. His research is particularly focused on HVAC (Heating, Ventilation, and Air Conditioning) system modeling and design optimization for building applications. This specialization reflects his commitment to enhancing the efficiency and effectiveness of building systems. Additionally, Professor Kim is deeply involved in research on renewable energy systems with the goal of achieving net-zero energy buildings. His work often incorporates field test-based analysis, demonstrating a practical and hands-on approach to building energy system challenges.

Authors:

Dongsu Kim Hanbat National University
Jaeyoon Koh Smart Building Solutions LLC.
Heejin Cho University of Nevada, Las Vegas
Jongho Yoon Hanbat National University