scholarly journals Advanced Exergy Analysis in the Dynamic Framework for Assessing Building Thermal Systems

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 32 ◽  
Author(s):  
Ana Picallo-Perez ◽  
José M Sala ◽  
George Tsatsaronis ◽  
Saeed Sayadi
Keyword(s):  
Exergy Analysis ◽  
Energy System ◽  
Building Energy ◽  
Hot Water ◽  
Exergy Destruction ◽  
Dynamic Calculation ◽  
Thermal Systems ◽  
Dynamic Framework ◽  
Building Energy System ◽  
First Time

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by distinguishing the inefficiencies that can be prevented by improving the quality (avoidable ED) and the ones constrained because of technical limitations (unavoidable ED). ED is related to the inherent inefficiencies of the considered element (endogenous ED) and those coming from the interconnections (exogenous ED). That information cannot be obtained by any other approach. A dynamic calculation within the experimental facility has been performed after a component characterization driven by a new grey-box modelling technique, through TRNSYS and MATLAB. Novel solutions and terms of ED are assessed for the rational implementation of the DAEA in building energy installations. The influence of each component and their interconnections are valuated in terms of exergy destruction for further diagnosis and optimization purposes.

Endogenous and Exogenous Exergy Destruction in Thermal Systems

2006 ◽  
Author(s):  
George Tsatsaronis ◽  
Solange O. Kelly ◽  
Tatiana V. Morosuk
Keyword(s):  
Exergy Analysis ◽  
System Optimization ◽  
Energy System ◽  
General Concept ◽  
System Component ◽  
Thermal System ◽  
Exergy Destruction ◽  
Thermal Systems ◽  
System Components ◽  
Refrigeration Machine

One of the roles of exergy analysis is to provide thermal system designers and operators with information useful for the system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. However, care must be taken when using the total exergy destruction within a component to reach conclusions regarding the optimization of the overall energy system. The reason is that the total exergy destruction occurring in a component is not due exclusively to that component but is also caused by the inefficiencies within the remaining system components. The endogenous exergy destruction within a component is defined as that part of the component's exergy destruction that is independent of any change in the exergy destruction within the remaining components. The part of the component's exergy destruction which depends upon the changes of the exergy destruction within the other components is defined as the exogenous exergy destruction. It is apparent that the sum of endogenous and exogenous exergy destruction is equal to the total exergy destruction within the component being considered. Knowledge of the exogenous and endogenous exergy destruction for the most important components can further assist the engineer in deciding whether an adjustment in that component or in the structure of the system (i.e. in the remaining components) is required to improve the overall system. The paper presents the general concept of endogenous and exogenous exergy destruction. Using a graphical approach, the endogenous and exogenous exergy destruction of a simple gas turbine process and simple refrigeration machine are investigated.

Detailed Energy and Exergy Analysis for a Solar Lithium Bromide Absorption Chiller and a Conventional Electric Chiller (R134a)

2011 ◽  
Author(s):  
Yang Hu ◽  
Laura A. Schaefer ◽  
Volker Hartkopf
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Cooling System ◽  
Residential Buildings ◽  
Lithium Bromide ◽  
Building Energy ◽  
Hot Water ◽  
Exergy Destruction ◽  
Absorption Chiller ◽  
Two Stage

The Building Energy Data Book (2009) [1] shows that commercial and residential buildings in the U.S. consume 39.9% of the primary energy and contribute 39% of the total CO2 emissions. In the operation of buildings, 41.8% of building energy consumption is provided for building cooling, heating, domestic hot water, and ventilation for commercial buildings, while in residential buildings, this percentage increases to 58%. In energy system analysis, the energy approach is the traditional method of assessing the way energy is used in an operation. However, an energy balance provides no information on the degradation of energy or resources during a process. The concept of exergy combines the first law and second law of thermodynamics. The exergy analysis clearly quantifies the energy quality match between the supply and demand sides, and also addresses the exergy destruction (entropy generation) in each component. In this paper, a solar thermal driven absorption cooling system was analyzed for providing cooling to a building, the Intelligent Workplace South Zone at Carnegie Mellon University. The system includes a 52 m2 parabolic trough solar collector, and a 16 kW (4 tons) two-stage lithium bromide absorption chiller. The energy model and newly developed two-stage lithium bromide absorption chiller are programmed and integrated in Engineering Equation Solver (EES). The temperature, enthalpy, entropy, mass flow rate, and mass fraction of lithium bromide in the solar absorption system were presented in steady state operation. The exergy destruction in each component is calculated. The exergy destructions for the solar collector, generator, absorber, and heat exchangers were significantly higher than those in evaporator, condenser and expansion valves, the overall energy and exegetic efficiency were also calculated.

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