Understanding Emissions from Combined Heat and Power Systems

Abstract

Combined Heat and Power (CHP) is more energy efficient than separate generation of electricity and thermal energy. In CHP, heat that is normally wasted in conventional power generation is recovered as useful energy for satisfying an existing thermal demand thus avoiding the losses that would otherwise be incurred from separate generation of power. Modeling analyses has demonstrated significant air emissions, transmission and price benefits of clean CHP technologies. Despite these benefits, CHP remains an underutilized technology hindered by a number of disincentives, including treatment under current air quality permitting practice, which does not recognize the efficiency benefits of CHP. Output-based standards begin to address these permitting shortcomings. This paper will discuss how to view emissions from CHP systems from an output-basis and compares emission from different technologies. Treatment of distributed generation is compared with central generation, and emissions from an integrated system that produces more than one usable output are discussed. Regulatory and policy strategies that encourage clear and efficient CHP are also discussed.