Investigation of the ratio of exergy consumption to energy consumption for building energy efficiency

ABSTRACT

The Ratio of Exergy consumption to Energy consumption (REXE) of the building is defined in the paper. The building life cycle REXE_LC provides a full understanding of high-quality energy consumption during the building life cycle. It is proposed as a new thermodynamic parameter to evaluate the building life cycle energy efficiency. It also can be applied as a simplified way to calculate the building life cycle exergy consumption. Five public buildings in China are taken as the study cases. The energy consumption, exergy consumption, and cost per construction area of the five cases are calculated to study the parameter REXE_LC. It is concluded that the building life cycle REXE_LC mainly depends on the energy consumption proportion and REXE of the building material’s production stage and building running stage. The economic analysis of the buildings shows that the building with too large or too small REXE_LC would not be the economic one. At last 2 mathematical regression models are established to investigate the relation between building life cycle energy consumption and REXE_LC. According to the regression model, all the buildings can be divided into four zones. The REXE_LC would be an important instruction in optimizing the design of building envelope.

KEYWORDS:

• Building energy efficiency
• cost
• energy consumption
• exergy consumption
• Ratio of Exergy consumption to Energy consumption (REXE)

Nomenclature

C	=	cost ($)
E	=	Energy consumption (MJ)
Ex	=	Exergy (MJ)
m	=	material/fuel consumption
N	=	electricity consumption (kWh)
N’	=	the building life-span (years)
T	=	temperature (K)

Greek Letters

φ

=

percentage

Subscripts

a	=	annual
c	=	cooling
con	=	construction
demo	=	demolition
elec	=	electricity
f	=	fuel
h	=	heating
i	=	types of energy
in	=	integrated
j	=	types of materials or workers
LC	=	building life cycle
mach	=	machinery
main	=	maintenance
mat	=	material
run	=	running

Additional information

Funding

This work was supported by National Key Technology Support Program (grant number 2015BAJ03B00); National Natural Science Foundation of China (grant number 51378186); National Special Program of International Cooperation and Exchange (grant number 2010DFB63830) and Science and technology plan project of Hunan Province (grant number 2015GK3026). And the authors are also grateful to Mushu Fu for her suggestions and help.