Comparative Analysis of Air-Based and Water-Based Cooling Systems in Office Buildings Under Changing Climate and Extreme Weather Conditions

Abstract

As climate change continues leads to rising global temperatures and poses the threat of extreme weather conditions, the cooling energy demand within the building sector is experiencing rapid growth. This study aims to compare both energy performance and cost efficiency between all-air cooling systems and water-based cooling systems by investigating variable air volume (VAV) system and ceiling radiant cooling panel (CRCP) system in a nine-storey office building located in Gothenburg, Sweden.
To conduct these comparisons, the professional energy simulation software IDA-ICE was employed to dimension the system size and energy simulations for both systems. The analysis encompassed energy demands for heating, cooling and HVAC auxiliary electricity. In addition, life cycle costs, including investment, maintenance and operational costs, were calculated to identify the most cost-effective mechanical cooling system over a long term (20 years). Furthermore, the study evaluated thermal comfort for each cooling system under both current and future climate scenarios.
The findings indicate that although the VAV system consumes less total energy as utilizing free cooling, it requires higher peak power compared to the CRCP system. Conversely, the CRCP system shows significant potential for reducing peak power demand and HVAC auxiliary electricity due to low airflow, thereby leading to long-term cost savings. The parametric analysis on external and internal loads shows that in winter, high external loads cause CRCP system consuming more energy for heating with high constant airflow, while high internal loads cause the VAV system consuming more energy for heating due to need of cooling for center zones. Moreover, the CRCP system can improve thermal comfort level for the occupants because it can provide lower and more table operative temperatures compared to the traditional VAV system. The initial investment of the CRCP system is slightly higher than that for VAV system, but it requires lower maintenance cost compared to VAV system. Over a 20-year calculation period, the CRCP system achieves a lower LCC. Despite having slightly higher annual energy costs than the VAV system in future climate scenarios, the overall cost efficiency of the CRCP system remains superior.
In conclusion, the CRCP system represents a viable and cost-effective alternative to traditional VAV systems, both under current and future climate scenarios, except under super high external loads condition.

Popular Abstract

"Air vs. Water: Which Cooling System Wins in an office building under Changing Climate?"
This project compares the energy and cost performance between VAV and ceiling radiant cooling panel systems in an office building in Sweden to identify the energy-efficient, cost-effective, and comfortable solution, considering changing climate.
Imagine walking into a sweltering office on a summer day, especially under future high temperature. What do you want most with unbearable heat? A reliable cooling system. However, which one would you like to invest in: an all-air system or a water-based system? Why do you choose that? The answer lies in the following analysis. Let's explore the results of the comparison between the VAV system and ceiling radiant cooling panels (CRCP) system.
Energy Efficiency: The CRCP system is a power-saver when it comes to peak demand and HVAC electricity, thanks to its low airflow. But here’s a weakness: it uses more overall energy because it always relies on chilled water from refrigeration.
Cost Savings: Think water-based cooling is expensive? Think again. While the initial investment cost more, the long-term savings are significant. Lower maintenance cost and energy bills mean that the investment pays off quicker than you might expect. Why not Imagine slashing your office’s electricity costs and investing those savings elsewhere!
Thermal comfort: Pay attention to the operative temperature — it’s what you actually feel! In the office with the CRCP system, you could experience a consistently cool environment without the discomfortable blowing air, especially on future extreme warm days, thanks to its lower and stable operative temperature.
Future conditions: When temperature rises in the future, heating demands will drop, but cooling needs will increase dramatically. The CRCP system can greatly cut peak power demand and offer long-term savings, but will need more energy overall due to its high compensation airflow. Meanwhile, the VAV system could see a reduction in total energy as increased cooling demand is balanced by decreased heating needs.
These comparison results were obtained by using a professional energy simulation software IDA-ICE. Regarding the future conditions, the method is based on synthesizing three projected weather data sets for each 30-year period, making simulations simplified but reliable. As for life cycle cost, investment, maintenance and operational costs were calculated to identify the most cost-effective mechanical cooling system over 20 years.
Based on the study, we could summarize some recommendations:
If your office is located in oceanic climate area like Sweden, a water-based cooling system such as CRCP system could be a good alternative compared to the traditional VAV system, which can enhance cost efficiency and thermal comfort.
As global temperature is rising and extreme weather becomes more common, investing the CRCP system could be an attractiveness but comprehensive consideration and more research are still needed.
In conclusion, the battle between all air and water-based cooling systems is heating up, the CRCP system is a strong contender for long-term efficiency, but the VAV system might still come out on top in overall energy savings.

• author: Xu, Mingyin
• supervisor: Vahid Nik; Taha Arghand
• organization: Division of Energy and Building Design
• course: AEBM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Variable air volume system, Ceiling radiant cooling panels system, energy performance, life cycle cost, future climate
• language: English
• id: 9171516
• date added to LUP: 2024-08-21 12:47:34
• date last changed: 2024-08-21 12:47:34