Building Life-cycle Energy Analysis And Application Study Based On Exergy Method

Building consumes large amounts of energy, which consumed in its life cycle accounts for more than a third of the social total energy consumption. With the building energy consumption increasing, more and more people have realized the importance of energy saving and exergy efficiency in buildings.In the paper, it focuses on thermodynamics investigation of building envelope construction and building operation phase, and the concept of exergy-energy ratio is proposed, which is used to reflect the relationship of energy consumption and exergy consumption and evaluate the utilization degree of high quality energy in building. And then, thermodynamics analysis model of building life-cycle energy consumption based on exergy is established, calculation method of energy and exergy consumption is derived. Then, a case of a research and development center located in Hunan is analyzed. Exergy efficiency of the energy flow process from primary energy to the building envelope is also analyzed. The relationship between outdoor air humidity ratio and exergy efficiency (considering indoor air processing) of the typical day is studied. Finally, energy consumption of the typical "unfinished deserted buildings" is estimated.The analysis results have shown that:(1) energy consumption of building operation phase accounts for about72%of the total energy use in the life cycle of the building for50years, and energy consumption in building envelope construction accounts for about23%, of which the energy consumption that building materials production consumed accounts for about91%.(2) The exergy-energy ratio of the entire building life cycle is0.80, exergy-energy ratio of building envelope construction process is0.79, and operational phase is0.80. The exergy-energy ratio of building envelope construction process and builidng operation phases are nearly equivalent with the entire building life cycle, which reflects that building envelope construction process and operational phase are the key to impact on building life cycle energy consumption.(3) The energy consumption of those unfinished deserted building which have not been revitalized is about6.1×106GJ, and exergy consumption is about4.8×106GJ.(4) Exergy efficiency of the energy flow process from primary energy to building envelope is very low. In heating season, the system exergy efficiency is about10.4%, and in refrigeration season, the system exergy efficiency is about30.1%, and the annual exergy efficiency is about27.9%. And the system exergy efficiency with outdoor ambient temperature reference state is greater than the exergy efficiency with annual average temperature reference state. And in refrigeration season, the change trends of system exergy efficiency are consistent with outdoor air moisture contentExergy-energy ratio can reflect building envelope construction process and operational phase are the key to impact on building life cycle energy consumption from another perspective, and use it to evaluate the utilization degree of high quality energy in building is feasible.The exergy combined with building life-cycle assessment method proposed in the paper can be applied to other similar buildings, and can provide a reference for the sustainable construction for buildings.