Dynamic exergy-based methods for improving the operation of building energy systems

The objective of the present research is the operational assessment of building energy systems through the application of conventional and advanced exergy-based methods. Two different case studies are considered here. The first one is a theoretical single-office building equipped with heating and ventilation systems, located in a typical cold-climate region. The second case study is a real-life system, including a large building and its complex heating and cooling systems, located in Aachen, Germany. Since the first case study is theoretical, mathematical heat and mass transfer models representing the system’s dynamic behavior were first formulated. Then all dynamic exergy-based methods were developed and applied to this model. Unlike the first case study, the second one is a real existing building with an extensive data collection and monitoring system, which offers the opportunity to apply all methodologies developed for the first case study to a “real” system. Consequently, the input data for the exergy-based operational assessment of the second case study comes from the various temperature, pressure, and volume flow rate sensors installed in different parts of the considered building. The present study provides a step-by-step framework for conducting dynamic exergy-based methods for building energy systems using a small and a large-scale case study. Two novel approaches for performing dynamic advanced exergetic analysis are proposed in this study for the first time. The first method, called the method of Serial F/P Arrangement, splits the dynamic exergy destruction into endogenous and exogenous parts, and the second one, called the Design-Based Approach, obtains the avoidable and unavoidable exergy destruction in dynamic systems. Moreover, the dynamic formulation of exergoeconomic analysis, taking into account the stored/discharged costs in different system components at different times, is also presented for the first time in the current research study. As a general rule of thumb, only between 15% to 25% of the total exergy destruction caused in the operation of building energy systems can be avoided. Approximately one-quarter of this avoidable exergy destruction is endogenous, and the rest is exogenous. This means improving the interconnections among system components through the implementation of better control systems has a stronger effect on the performance of the overall system than improving single components of the system. Based on the results of dynamic advanced exergetic and exergoeconomic analyses, four new dimensionless performance indicators for evaluating the “operation” of dynamic systems are introduced. Results obtained from both case studies confirm that these new exergy-based parameters provide valuable insights into the operational assessment of systems and can identify components with the highest priorities for optimization.

Author dc:creator

• Sayadi, Saeed

Advisor dc:contributor.advisor

• Tsatsaronis, George

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-10971

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/12096