Optimal option of natural-gas district distributed energy systems for various buildings

With the energy policy of encouraging Liquefied Natural Gas (LNG) application in China, district distributed energy (DE) system is expected to play a greater role in buildings. This paper presents the energy consumption characteristics of four building categories (residential buildings, hotels, offices and mixed buildings) in Dalian (China). A DE system under basic and improved operation cases is developed and evaluated with respect to energy savings, exergy efficiency, annual total cost savings and environmental impacts. Results show that (1) in summer day, the applications of DE system achieve no energy savings under basic cases in all types of buildings, however improved cases mostly contribute to the savings, especially case 4 with hybrid cooling system. (2) In winter day, all types of buildings with different cases achieve effective energy savings. (3) The exergy efficiency of DE system in summer day is lower than that in winter day due to the large cooling demands and low COP of absorption chiller. (4) The applications of the DE system decrease annual total cost and CO2 emissions in all examined operation cases compared with the reference system. Furthermore, the relationship between heat-to-power ratio and energy savings is also analyzed deeply in this paper.