Session: 02-06: HVAC System Analysis II

Paper Number: 142392

142392 - Life Cycle Assessment of a Water-Cooled Chiller 

Abstract: 

Life cycle assessments, or LCAs, present a methodology for assessing environmental impacts, such as a carbon footprint, over the entire life of a product from manufacturing to end-of-life. LCAs are especially important for Heating, Ventilation, and Air Conditioning (HVAC) products as building owners and original equipment manufacturers (OEMs) set net zero carbon emission goals for 2040 and beyond. Currently, the built environment contributes to 40% of annual global CO₂ eq emissions.

A life cycle assessment for a water-cooled chiller was performed based on ISO 14040/44, UL Environment Part A: Life Cycle Assessment Rules and Report Requirements (V3.2, 2018), and UL Environment Part B: Water Cooled Chiller EPD Requirements (V2.0, 2018). The results were published in an environmental product declaration (EPD) report.

The system boundary for the LCA cradle-to-grave study includes five categories: raw material extraction, processing, and transport to plant; manufacturing; delivery and installation; use and maintenance; and disposal. Six impact categories were included in the study: acidification potential of soil and water (AP), eutrophication potential (EP), global warming potential (GWP), depletion of the stratospheric ozone layer (ODP), depletion of non-renewable fossil fuels (Resources), and smog formation potential (SFP). Analysis results were normalized per functional unit as one ton of chilling capacity.

Primary data was compiled from the manufacturer on the chiller bill of materials (BOM) and facility utility consumption for the calendar year 2021. BOM data included component weight and material composition for various chiller capacities. Utility data of the manufacturing facility reported an electricity demand value per kilogram of specified material used. By deriving a per-unit value for manufacturing electricity, the electricity demand was scaled to all materials of the same type to calculate the total energy demand for the chiller. The proportion of energy demand for one chiller to the total electricity consumed by the facility was applied to other manufacturing inputs such as thermal energy and water. Scrap rates were also determined on a material basis using the same dataset. The only recycled materials included in the study are the reprocessing and preparation of recycled materials listed in the BOM.

The dominance analysis utilized R-134a as the default refrigerant to determine which life cycle modules had the highest contribution to environmental impacts. For the most common configuration, approximately 91% comes from operational energy use. The results also showed that refrigerant leakage during maintenance, use, and end-of-life phases plays a key role. AP is driven by the burning of coal or other fossil-based sources of energy for the generation of power. Further analysis revealed that AP, EP, ODP, and SFP impacts are prevalent during the two (2) chiller replacements over the service life of the building.

In summary, Commercial HVAC equipment plays a significant role in a building’s carbon footprint. The life cycle assessment process determined the specific emissions at every life stage of a water-cooled chiller and revealed opportunities to improve the design for sustainability, primarily by focusing on increased energy efficiency and reducing refrigerant GWP.

Presenting Author: Karina D'abruzzo Carrier Corporation

Presenting Author Biography: Karina D’Abruzzo is a systems engineer who leads the development of new water-cooled chillers at Carrier Corporation. Her research in life cycle assessments uncovered the process requirements to evaluate the carbon footprint of a water-cooled chiller.

Authors:

Karina D'abruzzo Carrier Corporation
Clayton Terry Carrier Corporation
Ravi Annapragada Carrier Corporation
Valerie Lisi Carrier Corporation