Life Cycle Optimization for Residential Air Conditioning Replacement
The electrical consumption from central air conditioners currently accounts for about 14% of residential electrical use in the United States. Utilizing more efficient air conditioning units is one strategy to curb energy consumption. However the potential energy savings and greenhouse gas emission reductions from operating a more efficient unit must be measured against the burden associated with the fabrication of a new unit and disposal of the old unit. It is often difficult for consumers to know how long to use products and when to replace them in order to minimize environmental impact and operating costs. A life cycle optimization (LCO) model was developed to evaluate the ideal replacement schedule for a typical central air conditioner from 1985-2025. Life cycle profiles for each air conditioner model year were key parameters input into the LCO model. An algorithm was used to determine in which years the unit should be replaced. Replacement schedules were explored for the various climate zones in the continental United States. Using this method replacement schedules were developed with the objective of minimizing (1) energy usage (2) greenhouse gas emissions and (3) cost to the consumer. The model was also used to examine how rates of efficiency improvement and changing energy costs impact this schedule. Furthermore the research will explore how demand-side management can be used to correct misalignment between the cost schedules and the energy and emissions schedules through the use of utility incentives for early replacement of inefficient units. The results are expected to help manufacturers consumers and policymakers understand the environmental and economic benefits of the replacement of old air conditioners with new units.