A modified total equivalent warming impact analysis: Addressing direct and indirect emissions due to corrosion
A global rise in HVAC-R utilization requires a deeper understanding of the industry's effect on electricity consumptions and greenhouse gas emissions. The Total Equivalent Warming Impact (TEWI) methodology was designed to analyze emissions from direct release of refrigerant and indirect emissions through electricity consumption of HVAC-R systems to increase the understanding of system design on emissions, and to guide refrigerant replacement. However, the original TEWI calculation neglects the system degradation due to corrosion. This paper studies on the impact of corrosion and highlights how the original TEWI method underrepresents the lifetime emissions due to energy efficiency decrease and refrigerant release. Corrosion impacts direct emissions by increasing refrigerant leakage rates over time and indirect emissions through heat exchanger efficiency degradation and suboptimal refrigerant level. A modified TEWI equation is proposed to capture the dynamic corrosion impacts over the lifetime of HVAC operations. Three scenarios (low corrosivity, conservative and moderate corrosivity) are examined to analyze different corrosion environments. This analysis indicates 6%–27% increase in TEWI emissions based on a typical residential air conditioner (AC), when the impacts of corrosion are included, with the greatest emissions increase from reduced electrical efficiency. The impact of several current and future corrosion protection scenarios on TEWI are also included. Appropriate corrosion mitigation can reduce total lifecycle emissions of systems by 6% ~ 10%. The proposed modified TEWI method is expected to provide a more accurate emission estimation for AC sustainability and policy making.