Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively

Application of net zero extended exergy buildings concept for sustainable buildings analysis

[EN] Different Zero-Energy Building (ZEB)-related definitions considering its four main dimensions, such as zero energy, zero carbon, zero exergy and zero cost, have been proposed by different investigators. Among these, exergy-based definitions are relatively low in numbers. In this regard, the main objective of this present study is to propose net zero extended exergy buildings as a new concept, which combines extended exergy and net zero exergy building concepts and is a measure of the exergetic footprint. This concept setups a balance between extended exergy accounting of electricity from the grid and electricity generated in building. The proposed methodology is applied to a building available in the literature for heating and cooling seasons. Results show that 450Wp peak power and 44.181 kWh electrical energy must be obtained for meeting the electricity demand of the building. Another novel result is that the extended exergy accounting of the electricity generated by PV panels is bigger than the extended exergy of the electricity taken from the gird meaning that exergetic footprint of the electricity generated by PV panels is bigger. However, this result must be interpreted for the whole life time of the system.S

Performance evaluation of a building integrated photovoltaic (BIPV) system combined with a wastewater source heat pump (WWSHP) system

This paper deals with both energetic and exergetic performance assessments of two combined systems as a whole. The first one is a Building Integrated Photovoltaic (BIPV) system while the second one is a wastewater (WW) Source Heat Pump (WWSHP) system. Both systems were installed at Yasar University, Izmir, Turkey within the framework of EU/FP7 and the Scientific and Technological Research Council of Turkey (TUBITAK) funded projects, respectively. The BIPV system was commissioned on 8 February 2016 and has been successfully operated since then while the WWSHP system was put into operation in October 2014. The BIPV system has a total peak power of 7.44 kW and consists of a total of 48 Crystalline Silicon (c-Si) modules with a gap of 150 mm between the modules and the wall, and a peak power per PV unit of 155 Wp. The WWSHP system consists of three main sub- systems, namely (i) a WW system, (ii) a WWSHP, and (iii) an end user system. Two systems considered have been separately operated while the measured values obtained from both systems have been recorded for performance assessment purposes. In this study, a combined system was conceptually formed and the performance of the whole system was evaluated using actual operational data and some assumptions made. Exergy efficiency values for the WWSHP system and the whole system were determined to be 72.23% and 64.98% on product/fuel basis, while their functional exergy efficiencies are obtained to be 20.93% and 11.82%, respectively. It may be concluded that the methodology presented here will be very beneficial to those dealing with the design and performance analysis and evaluation of BIPV and WWHP systems

Experimental and numerical studies to assess the energy performance of naturally ventilated PV façade systems

This paper presents a holistic approach to assess the energy performance of a naturally ventilated PV façade system. A rigorous combined experimental and numerical approach is established. The real energy performance of the system has been evaluated through a long-term high resolution monitoring of a typical ventilated PV façade system. A numerical model based on TRaNsient SYstem Simulation (TRNSYS) package was developed to assess the thermal and energy performance of the system, which has been verified by a series of statistical analysis using the data collected from the experiment. The validated model was then used to assess the energy and thermal performance of a 7.4 kWp prototype ventilated PV façade system in Izmir, Turkey. The results of this study demonstrated that ventilation in the air cavity of the PV façade system could significantly improve energy performance of the system even in a southeast facing façades. The quantitative analysis provides useful guidance to the system designers for the improvement of energy efficiency of the PV facade system

Sustainability indicators of a naturally ventilated photovoltaic façade system

Building Integrated Photovoltaic (BIPV) systems have been increasingly used as a means to generate electricity on-site, and their diffusion will increase in the near future. The objective of this article is to carry out a sustainability assessment of a BIPV system installed in Turkey regarding the three pillars: environmental, economic and social potential impact, in order to develop different indicators. For the socioeconomic analysis, a Multiregional Input-Output (MRIO) method was used to estimate production of goods and services, value added creation and employment opportunities. For the environmental evaluation, an Environmental Footprint (EF) analysis was performed. The levelized electricity costs and the greenhouse gas emissions abatement costs were also calculated. Results showed that the socioeconomic effects are relevant, although only a 23% of these effects remain in Turkey. The environmental profile is also good in terms of climate change impacts, showing substantial reductions in greenhouse gas emissions compared to fossil fuel alternatives for electricity generation. Regarding the life cycle stages of the technology, the highest environmental impacts are produced in the PV manufacturing processes. The electricity produced is still more costly than fossil-based technologies and in the highest range of PV technologies, but greenhouse gases abatement costs are not so high when compared to other references

Thermoeconomic analysis of household refrigerators

WOS: 000248519600003This study deals with thermoeconomic analysis of household refrigerators for providing useful insights into the relations between thermodynamics and economics. In the analysis, the EXCEM method based on the quantities exergy, cost, energy and mass is applied to a household refrigerator using the refrigerant R134a. The performance evaluation of the refrigerator is conducted in terms of exergoeconomic aspects based on the various reference state temperatures ranging from 0 to 20 degrees C. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. Thermodynamic loss rate-to-capital cost ratios for each components of the refrigerator are investigated. Correlations are developed to estimate exergy efficiencies and ratios of exergy loss rate-to-capital cost as a function of reference (dead) state temperature. The ratios of exergy loss rates to capital cost values are obtained to vary from 2.949 x 10(-4) to 3.468 x 10(-4) kWUSS(-1). The exergy efficiency values are also found to range from 13.69 to 28.00% and 58.15 to 68.88% on the basis of net rational efficiency and product/fuel at the reference state temperatures considered, respectively. It is expected that the results obtained will be useful to those involved in the development of analysis and design methodologies that integrate thermodynamics and economics. Copyright (c) 2006 John Wiley & Sons, Ltd

A review on energetic, exergetic and exergoeconomic aspects of geothermal district heating systems (GDHSs)

WOS: 000278730100025Geothermal is a reliable and promising renewable energy. In 1892 the first geothermal district heating system (GDHS) began operations in Boise, Idaho, USA. Since then, a number of GDHSs installations have been made worldwide. Various investigations on the efficient utilization of geothermal energy resources have also been conducted to attain sustainable development. There is a link between exergy and sustainable development. In recent years, exergy analysis has been widely used in the design, simulation and performance assessment of thermal systems. Exergoeconomic analysis, which is a combination of exergy and economics, is nowadays considered a powerful tool to study and optimize various types of energy-related systems. The present study comprehensively reviews GDHSs in terms of three aspects, namely energetic, exergetic and exergoeconomic analyses and assessments, for the first time to the best of the author's knowledge. A brief historical development of the studies on GDHSs was given on the base of these three aspects first. Next, GDHSs analyzed were schematically presented and shortly described. The previously conducted studies on GDHSs were then reviewed and classified. Finally, the conclusions were presented. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the energetic, exergetic and exergoeconomic design, analysis and performance evaluation of GDHSs. (C) 2010 Elsevier Ltd. All rights reserved.Scientific & Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)The continuous incentive support given by the Scientific & Technological Research Council of Turkey (TUBITAK) is gratefully acknowledged. The author would like to express his appreciation to his wife Fevziye Hepbasli and his daughter Nesrin Hepbasli for their continued patience, understanding and full support throughout the preparation of this paper as well as all the other ones. He is also very grateful to the three reviewers and the editor for their valuable and constructive comments, which have been utilized in improving the quality of the paper

Exergetic modeling and assessment of solar assisted domestic hot water tank integrated ground-source heat pump systems for residences

WOS: 000250696900003The present study deals with the exergetic modeling and performance evaluation of solar assisted domestic hot water tank integrated ground-source heat pump (GSHP) systems for residences for the first time to the best of the author's knowledge. The model is applied to a system, which mainly consists of (i) a water-to-water heat pump unit (ii) a ground heat exchanger system having two U-boreholes with an individual depth of 90 m, (iii) a solar collector system composing of rooftop thermal solar collectors with a total surface area of 12 m(2), (iv) a domestic hot water tank with a electrical supplementary heater, and (v) a floor heating system with a surface of 154 m 2, and (vi) circulating pumps. Exergy relations for each component of the system and the whole system are derived for performance assessment purposes, while the experimental and assumed values are utilized in the analysis. Exergy efficiency values on a product/fuel basis are found to be 72.33% for the GSHP unit, 14.53% for the solar domestic hot water system and 44.06% for the whole system at dead (reference) state values for 19 degrees C and 101.325 kPa. Exergetic COP values are obtained to be 0.245 and 0.201 for the GSHP unit and the whole system, respectively. The greatest irreversibility (exergy destruction) on the GSHP unit basis occurs in the condenser, followed by the compressor, expansion valve and evaporator. (C) 2007 Elsevier B.V. All rights reserved

A study on estimating the energetic and exergetic prices of various residential energy sources

WOS: 000252604700015In choosing the type of any energy sources for residential and other uses, their prices play in general a big role. These prices are based on energy values. Besides this, the application of the exergy, which is a way to a sustainable future, is more meaningful in providing information for long-term planning of resource management. In the present study, energy and exergy prices of various energy sources are investigated. The energy sources considered include coal, natural gas, furnace oil, diesel oil, liquefied petroleum gas (LPG) and wood, while electric resistance along with heat pump and district heating are also covered. In this context, chemical exergy relations of these energy sources are presented first. The prices of various energy sources in the Turkish residential sector, which is given as an illustrative example, are then used in the calculations. Finally, the energy and exergy prices are compared with each other, while the main conclusions are listed. The highest unit energy price is that of diesel oil, while the lowest one is that of natural gas. The differences between the energy and exergy prices are small for all energy carriers. (c) 2007 Elsevier B.V. All fights reserved