Increasing demand of energy in the world and environmental consequences of using fossil fuels brought the idea of improving energy efficiency in energy systems. To this end, the concept of exergy analysis is developing to optimize energy systems by taking into account both quality and quantity of energy instead of only its quantity. Exergy is defined as the maximum amount of work can be obtained from different forms of energy which shows the quality of that energy form. Aim of this work is investigating the advantages of performing exergy analysis for thermodynamic systems consist of District Heating Network (DHN) and comparison with individual heating (IH) systems. Moreover the influence of choosing control volume, energy source type, conversion technology, supply/return temperature and reference temperature on exergy analysis is investigated. An initial literature overview to see the diversity of methodologies used for exergy analysis shows that a) there is no generally agreed terminology and nomenclature for exergy analysis and b) the most popular exergy indicator is exergy efficiency, although some other indicators also have been used by some researchers. In some cases the exergoeconomic indicators are investigated to discover the possible relationships between exergy and economic results. In the next step, the energy & exergy performance of 3 case studies in Austria are analyzed using an existing static Matlab tool for energy systems analysis. This tool receives the input data (like: conversion technologies, load percentage, exergy content of sources etc.) for each case study, and delivers the results of energy, exergy & environmental assessment. Comparison of the results for different case studies and scenarios shows that the most important factor that changes exergy performance of system is the energy source form and its conversion technology. In the meantime, it is observed that lowering supply temperature of DHN can increase the exergy efficiency of system, while changing reference temperature of system does not show a clear ascending or descending trend of exergy efficiency although it affects the exergy efficiency value. In case of disregarding CHP plant from the system, IH has slightly higher exergy efficiency compare to DH while presenting CHP plant in real systems proves the opposite result. Finally no connection between energy and exergy efficiencies of these thermodynamic systems was discovered. Regarding the ecologic assessment it is concluded that the higher is the exergy efficiency of system; the less is the direct CO2 emissions of it.
|Betreuer/-in / Berater/-in|
|Datum der Bewilligung||31 März 2015|
|Publikationsstatus||Veröffentlicht - 2015|
- Ehemaliges Research Field - Energy