LIFE CYCLE ENVIRONMENTAL IMPACT ANALYSIS OF ALTERNATIVE USES OF NATURAL GAS-FIRED EQUIPMENT IN BUILDINGS

摘要

LIFE CYCLE ENVIRONMENTAL IMPACT ANALYSIS OF ALTERNATIVE USESOF NATURAL GAS-FIRED EQUIPMENT IN BUILDINGSAyat Ezzeldin Osman, MSUniversity of Pittsburgh, 2002Cogeneration systems offer an opportunity to satisfy buildings' electrical and thermal loads, which could result inoverall energy efficiency improvements and lower emissions to the environment. The objective of this research is touse a life cycle assessment framework to evaluate the environmental impact of using natural gas-fired technologiesfor heating, cooling and electrical energy generation in buildings. The natural gas-fired cogeneration systemsexamined were solid oxide fuel cell (SOFC), microturbine, and internal combustion engine (ICE). These systemswere compared to two systems representing conventional practice: average electric generation mix in the U.S. andnatural gas combined cycle electric generation (NGCC) for electrical energy; electric chillers (EC) and absorptionchillers (AC) for cooling; and natural gas-fired boilers for heating.A large commercial office building was used as a hypothetical case study. Typical building characteristics from theCommercial Building Energy Consumption Survey (Sezgen et al., 1995) in combination with simulation softwarewere used to obtain the building's electrical, heating, and cooling energy use. The building's energy use and processdescriptions were used to construct life cycle models with the aid of life cycle assessment software.The results of the research include analysis of the environmental impact from the use of the different energy systemsin the building and comparisons between different operational strategies for the cogeneration systems: thermal loadfollowing (TLF) and electrical load following (TLF). Under the assumptions in this study, the main findings werethat cogeneration systems performed better with ELF when the thermal load of the building was high; energyconsumption and emissions were reduced when AC or combination of AC and EC were used for cooling withcogeneration systems, except for the SOFC, which performed equally well with EC only; and the 3-MW ICE (ELF)using combination of AC and EC, and the SOFC using EC (ELF) showed the best performance given the indicatorsand systems considered.