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Growing number of household refrigerators and freezers also increase the overall energy consumption and number of household refrigerators have grown nearly 3% per year. on the other hand, investigations showed that household refrigerators have a significant technical energy saving potential of up to 30-40%. in this study, a single-phase natural circulation loop is considered as a suction line heat exchanger between the high and low pressure sides of conventional refrigeration cycle of a household chest freezer. the potential heat transfer by the single-phase natural circulation loop is studied by a CFD analysis, considering the possible temperature range for refrigeration cycle and geometrical parameters that affect the loop performance. the performance map of this refrigeration cycle is presented for different compressor suction and discharge pressures (LP/HP), discharge temperatures (T-2) and different compressor speeds. the results indicate that the highest amount of heat transfer is obtained for the single-phase natural circulation loop with aspect ratio of 0.8 and pipe diameter of 6.53 mm. Moreover, the single-phase natural circulation loop provides 11.5% efficiency improvement for the household freezer for maximum compressor speed at lowest T(2)and LP/HP. Considering reduction in required compressor work, SPNCmL assisted refrigeration system has a wider operating range., Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [5180042], This research was supported by the Scientific and Technological Research Council of Turkey under grant number: 5180042.

Fuels that are environment-friendly resources play a vital role in the development of economies. Each fuel resource has intensive, however, inadequate specifications in terms of security, sustainability, capacity to compete with other sources. Although oil and gas resources lead the way of fuel production due to their low cost, alternative sources such as wind and solar renewable energy and nuclear energy have also gained popularity forcing the technological development of fuel production technologies. Hydrogen is a source for the production of energy by using any energy resource. In this chapter, we investigate the latest fuel production technologies providing energy outputs from renewable energy resources for their usage in smart cities. We study the role of renewable resources under the current dynamics of the global energy market situation as well as the effects of fuel production technologies to increase the efficiency and sustainability for the future of smart cities. This review includes a broad spectrum that spans from the technical energy resources literature with very comprehensive research by using SCOPUS database to nontechnical but renowned resources including journals and other publications including raw data as well as forecasts and opinions that respected experts have performed. Specifically, solar and wind production technologies, as well as future forecasts compared with the conventional fuel resources, are reviewed comprehensively. By that, we aim to shed a light on the current status of fuel production technologies in renewable energy resources and their usage in smart cities. © 2022 Elsevier Inc. All rights reserved.

This study deals with designing a decentralized multi-input multi-output controller board based on a low-cost microcontroller, which drives both parts of variable-speed scroll compressor and electronic-type expansion valve simultaneously in a chiller system. This study aims to show the applicability of commercial low-cost microcontroller to increase the efficiency of the chiller system, having variable-speed scroll compressor and electronic-type expansion valve with a new electronic card. Moreover, the refrigerant system proposed in this study provides the compactness, mobility, and flexibility, and also a decrease in the controller unit's budget. the study was tested on a chiller system that consists of an air-cooled condenser, a variable-speed scroll compressor, and a stepper driven electronic-type expansion valve. the R134a was used as a refrigerant fluid and its flow was controlled by electronic-type expansion valve in this setup. Both variable-speed scroll compressor and electronic-type expansion valve were driven by the proposed hardware using either proportional integral derivative or fuzzy logic controller, which defines four distinct controller modes. the experimental results show that fuzzy logic controlled electronic-type expansion valve and proportional integral derivative controlled variable-speed scroll compressor mode give more robustness by considering the response time., Turkish National and Scientific Research Council (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TEYDEB-1505, 5130027], The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was funded by a grant (TEYDEB-1505 No. 5130027) from the Turkish National and Scientific Research Council (TUBITAK).

In this study, a chiller system with an electronic expansion valve (EEV) and a thermostatic expansion valve (TXV) were compared from an energy saving view under variable and fixed speed compressor. The experimental chiller system under study has a variable speed scroll compressor, EEV and TXV, air cooled condenser and auxiliary equipments. The R134a was used in the compressor as a refrigerant. Although in variable speed chiller systems usually EEVs are used, in this study a TXV was also used to compare its performance. The results of the experimental studies show that the chiller system with EEV has 30% lower superheat value and 6% lower power consumption than the chiller system with TXV under variable speed operation. From the fixed speed compressor view, the chiller system with TXV performs 1.7% lower superheat value than the chiller system with EEV and, the chiller system with EEV has 8.5% higher compressor power consumption than TXV.

EgeUn###, In this study, implementation of a thermosyphon heat exchanger into a Stirling refrigeration system is demonstrated by means of both theoretical and experimental analyses. R-134a was employed as the working fluid which formed a liquid column at the condenser exit, enabling a two-phase flow through the evaporator. Experiments were conducted in a controlled chamber. Cooling capacity, coefficient of performance, and two-phase pressure drop of the cooler were compared at two different voltages. The flow regime for the refrigerant in the evaporator was found to be stratified based on the calculated wavy flow and Lockhart-Martinelli parameters.

Güneş takip sistemleri, fotovoltaik panellere gelen güneş ışınlarının dik açı ile panele gelmesini sağlayan ve elektrik enerji üretim verimini arttıran sistemlerdir. Bu çalışmada, bir güneş takip sistemi akıllı kontrol algoritmalarından bulanık mantık ile tasarlanıp, deney düzeneği üzerinde ugulaması yapılmıştır. Deney düzeneğinde kullanılan mikrodenetleyicinin analog girişlerine bağlı dört ışık algılayıcısından alınan veriler, oluşturulan bulanık mantık kurallarına göre yorumlanır. Elde edilen kontrol işaretleri ile servo motorlar tasarlanan mekanik yapının çift eksende hareket etmesini sağlayarak, fotovoltaik panelin güneş ışınlarını dik bir açı ile almasını sağlamıştır. Matlab/Simulink ortamında tasarlanan kontrolör gerçek sistemi kontrol etmiştir. Geliştirilen kontrol mekanizması sayesinde özellikle olumsuz hava koşullarında sistem bulunduğu konumu koruyabildiği için bu izleme yönteminin başarılı sonuçlar verdiği görülmektedir. Kullanılan bu akıllı kontrol ve güneş takip sistemi ile fotovoltaik sistemin elektrik üretme veriminde yaklaşık %9 oranında verim artışı sağlanabildiği gözlenmiştir., Sun tracking systems improve energy production efficiency and also provide direct solar radiation to the photovoltaic panels. In this study, a suntracking system has been controlled via fuzzy logic control as a smart control algorithm by using an experimental setup. In the setup, there is a microcontroller with four anolog input connected to light sensors and fuzzy algorithm. The resulted control signals drive the servo motors and tracks sun with two axes via Matlab/Simulink environment. In conclusion, the control system was able to keep the system very stabile position especially at bad weather conditions in a good success. As a result, the smart control and sun tracking system provide 9% improvement in photovoltaic energy production efficiency.

Although, fossil fuels are still the main source that used to balance the global demand/supply dynamics of energy; most countries have embarked on a quest to reach a solution and started changing their direction from fossil resources (especially oil and gas) to other resources by creating new opportunities with a focus meeting the increasing energy demand by reducing it via energy efficiency. "Transportation" is one of the biggest items of global energy consumption with 24% usage percentage and most of this amount is supplied by conventional energy resources. However, worldwide supporting policies and regulations are positively affected the starting period of environment-friendly use of energy resources. It expedited the process of new technological developments that minimize waste, lower the level of air pollution caused by fossil fuel-powered internal combustion engines, conserve forests and decrease the emissions of greenhouse gases. Worldwide extension of "Electric Vehicle Development and Production" is one of the main concern of these regulations. However, increasing the number of electric vehicles also brings sustainability problems such as; supplying the electricity from renewable resources in an efficient and sustainable way, handling the electricity load on the grid, and establishment of new charging stations. Therefore, in this study a wind solar hybrid energy charging station designed and optimized via HOMER software. The sizing methodology is suitable to apply anywhere around the worldwide. The optimal solution for the hybrid system consists of 44.4% wind energy and 55.6% solar energy and the annual electricity production is 843150 kWh with the 0.064 $/kWh production cost. (c) 2020 Elsevier Ltd. All rights reserved.

In this study, a numerical model of a reciprocating magnetocaloric regenerator using a Halbach magnet array is developed in ansys-fluent software. The model consists of three components, namely, (i) the Halbach magnet array, (ii) the magnetocaloric material (MCM), and (iii) the heat transfer fluid. A two-dimensional (2D) domain is studied due to the axisymmetric geometry of the physical model. A pressure difference is defined between the inlet and outlet sections of the fluid domain to maintain a reciprocating fluid flow. In the proposed computational scheme, a segregated approach is followed to consider the spatial distribution of the magnetic field in the thermal analyses. Therefore, a 2D magnetic field within the MCM is computed using an analytical approach at first, and its results are integrated into ansys-fluent with a user-defined function (UDF). Hydrodynamic and heat transfer characteristics of the proposed regenerator model are evaluated under various Reynolds numbers and cycle durations. Moreover, the temperature drop at the cold side of the regenerator is represented in terms of the pressure difference, flow duration, and the diameter of Gadolinium (Gd) as the MCM. For the current geometrical configurations, it is observed that the magnetic field varies from 0.4 T to 1 T within Gd. The highest temperature spans are measured as 8.4 K, 7.5 K, and 7.2 K numerically for the cycle durations of 1.2 s, 2.2 s, and 4.2 s, respectively.

Geothermal energy is a reliable, environmentally friendly resource efficiently transformed to other energy forms without any storage. Therefore, it has taken the attention of many investors in recent years. The investments in developing new technological materials, tools, fluids and methods to obtain fluid and heat transfer from a geothermal reservoir open the way to increase the efficiency of the entire geothermal power generation cycle in the medium and long terms. The effectiveness of a geothermal production system is directly related to the sustainability of the reservoir and production wells. At this point, the presence of CO2 is crucial for the life of a geothermal well as it provides extra pressure and a lifting mechanism to geothermal fluids along the wellbore. Studies that compare the effect of CO2 in a geothermal reservoir are available in the literature. However, a comprehensive review study investigating the impact of water and CO2 interactions under dynamic wellbore flow conditions is missing. This study aims to be a reference guide to geothermal industry experts by performing a comprehensive literature review of studies about wellbore dynamics involving geothermal fluids' physical and thermodynamic behaviour during production and injection in the presence of CO2 along the wellbore. In this study, a detailed literature review about the theory, methodology, advantages and drawbacks, and the challenges of using CO2 in a geothermal system and the effects of having CO2/geothermal water interaction in the wellbore is given.

In this study, a modified direct current compressor (MDC) is tested experimentally. The experimental study is conducted in order to observe the performance of a solar energy powered MDC. Then, the performance of this MDC is compared with brand new direct current compressors (BNDC) in the market. The experimental setup has a mini fridge with 50 liters capacity, a photovoltaic panel, a battery, a charge regulator and measurement equipments. Also, a pyranometer is used to define solar radiation on the photovoltaic panel. Experiments are conducted for various cabinet loads such as no storage items, low, nominal and over load at steady state condition.

Refrigeration systems have higher electricity consumption ratio in overall energy consumption especially in household utilization. On the other hand, these systems have an advantage of being powered by renewable energy sources such as solar or solar-wind hybrid systems because of their lower power demand. Since the efficiency improvement of refrigeration systems is crucial for domestic and industrial systems in the present study, solar energy powered compressor for vapour compression refrigeration systems have been investigated. Compressor is the most important part and often the costliest component of any refrigerant system. There are two different options for powering the compressor such as alternative current (AC) and direct current (DC).For that reason, this study focused on thermal analysis of critical component inside the novel DC compressor. Computational Fluid Dynamics (CFD) analysis has been realized to figure out the heat transfer mechanism inside the compressor components and also thermodynamics efficiency. Temperature distribution in the compressor during the operation was presented and the component of the compressor position re-designed with resulted parameter and discussed affects of the volumetric efficiency.Furthermore, in this study, experimental performance analysis of the novel DC type refrigeration compressor implemented in a 50 l refrigerator to show its cooling performance and compare well known DC compressor in the market. Energy usage reduction and operational improvement potential of the solar powered DC compressor via variable speed operation were investigated. The comparison showed that variable speed operation of the novel DC compressor can be much more efficient than constant speed operation.

Ejector expansion refrigeration cycle with reference to the constant pressure mixing theory is investigated to display the effects of the liquid-vapor separator efficiency on the performance, entrainment ratio, and area ratio at various operation conditions. Reversible ejector assumption is used for the highest theoretical performance limit, whereas efficiency of the liquid-vapor separator and all ejector components is added to the model to calculate more realistic performance improvement potentials. R1234yf and R1234ze(E) having low global warming potential values are used in the analyses. Zero-dimensional thermodynamic models are constructed applying the conservation equations between the inlets and outlets of the refrigeration cycle and ejector components. Percentage performance decrease is higher when the mixing section and the separator efficiency is added to the model at higher condenser temperatures compared with the lower evaporator temperatures according to the investigated operation ranges. Vapor and liquid separation efficiency affects not only the performance but also the design of the ejector although it is an external component since it has influence on the area ratio and entrainment ratio. Finally, the difference between the percentage performance improvement of the reversible ejector cycle and the realistic ejector cycle including the separator and ejector components efficiencies is as high as 35% at the highest investigated condenser temperature for R1234yf. Copyright © 2019 by ASME., Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAK: 116M367, Scientific and Technological Research Council of Turkey (TÜBİTAK) (Grant No. 116M367; Funder ID: 10.13039/ 501100004410).

Two-phase ejectors are used in the refrigeration cycles to decrease the throttling losses and improve the performance. The subject of this paper is the motive nozzle which is the critical component of the ejector since the pressure distribution throughout the motive nozzle affects the secondary fluid to be entrained into the ejector. A simplified version of the one of the previously established one-dimensional (1-D) converging-diverging motive nozzle models is developed in this paper to calculate the pressure, temperature, velocity, and Mach number distributions. 1-D model of the nozzle is established based on the conservation equations of mass, momentum, and energy and the equation of state under steady, frictional, and adiabatic flow assumptions with the homogeneous equilibrium condition. Maximum differences of the pressure drop throughout the nozzle between the literature data and the calculated results are around 6% and 8% for CO2 and R134a nozzles, respectively. The main objective is investigating the effects of the subcooling temperature difference, inlet pressure (condenser temperature or pressure), mass flow rate, and motive nozzle outlet diameter for R134a, R1234yf, and R1234ze(E). Parametric comparisons and evaluations are used to lead the motive nozzle designs for the further numerical and experimental studies including these new generation refrigerants for R134a replacement. © 2020 Elsevier Ltd, 116M367 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAK, The authors would like to acknowledge the support of the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 116M367 .

This study reports levels of indoor environmental quality variables before and after installation of heat recovery ventilation in a primary school located in an urban area in Izmir, Turkey. A CO2-based modeling was performed to determine the required flow rates that would comply with an international ventilation standard, followed by computational fluid dynamics modeling for best airflow distribution in a classroom. Temperature, CO2, PM2.5, and total volatile organic compounds were found at undesired levels, among which relative humidity, CO2, and PM2.5 were improved after the intervention. Reductions in the mean and maximum concentrations were 29% and 68% for CO2 and 29% and 46% for PM2.5. This intervention study was a part of the city-wide main project that aimed to increase awareness of the students and their families, teachers, and staff regarding importance of indoor environmental quality in both at school and home due to its possible effects on children's health and academic performance, one of the major challenges of today's societies all around the globe., Mechanical Engineering Chamber of Izmir; HVAC industry; Ministry of Education-Izmir Directorate

4th International Conference on Advances on Clean Energy Research (ICACER) -- APR 05-07, 2019 -- Univ Coimbra, Coimbra, PORTUGAL, WOS: 000503744000002, Ejector expansion refrigeration cycle is the modification of the vapour compression refrigeration cycle with the implementation of a two-phase ejector and a vapour-liquid separator to improve the cycle performance. in this study, main geometrical parameters of an ejector, i.e. diameters of the motive nozzle throat, motive nozzle outlet, suction nozzle outlet, and constant area mixing section are calculated in order to provide the preliminary design aspects at various operation conditions. the thermodynamic model of the ejector is established with reference to constant-area mixing assumption. the equations are solved in Matlab (R). the environmentally-friendly refrigerants, R1234yf and R1234ze(E) from the hydrofluoroolefins (HFOs) and R134a which is about to be phased out by the F-gas Regulation are used in the analyses. When compared to the previous literature findings, the current research aims to compare the dimensions of a twophase ejector to be used in anexperimental system having 5 kW coolingcapacity for these three refrigerants., Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116M367], The authors would like to acknowledge the support of the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 116M367.

Ejector expansion refrigeration cycle was investigated theoretically to compare the constant pressure mixing and constant area mixing ejector theories making use of thermodynamic models. Performance improvement was presented according to optimum and constant value pressure drop assumptions in order to simulate the design and off-design conditions, respectively. The agreement between the results with respect to both pressure drop assumptions is better at higher condenser and lower evaporator temperatures for each ejector mixing theory. Optimum area ratio (phi(opt)) is less for constant area mixing approach since the ratio of the secondary flow velocity to the primary flow is higher for this ejector theory at each operation point. Although a group of low-global-warming-potential refrigerants were compared in terms of the performance and expansion losses, deep investigations were presented for R1234yf in main and sometimes R1234ze(E). Finally, when compared to other ejector sections, the mixing section efficiency has the most critical effect on the optimum performance improvement ratio of R1234yf with reference to constant pressure mixing assumption. (C) 2018 Elsevier Ltd and IIR. All rights reserved.

Wastewater heat recovery applications are becoming widespread in energy saving applications. A sustainable and low emissions operation in air conditioning and heating processes is achieved by harvesting the otherwise wasted energy in wastewater through specially designed heat exchangers, lying at the core of heat pumps. This combined system is called wastewater source heat pump. In this study, a review of wastewater heat exchangers in wastewater source heat pump applications is presented, and wastewater heat exchangers are classified in detail based on multiple features, including utilization and construction methodology. Also, the potential of wastewater, types of wastewater source heat pumps, and their applications are briefly discussed. (C) 2015 Elsevier B.V. All rights reserved.

In this study, retrofitting of a fixed speed refrigeration system to a variable speed refrigeration system is investigated. Economical and technical benefits of the retrofitting procedure are also studied. Refrigeration systems are usually designed to overcome maximum load conditions. However, they work under partial load in most of their life cycle. Hence, in this study a variable speed compressor that equalizes the cooling load to the demand that assures significant energy saving is considered. As a result of this study, the retrofitted variable speed compressor performed 17% decreased energy consumption versus the thermostatic controlled fixed speed system. Also, the retrofitting procedure provided considerable payback time. From the result, 10750 kilograms less carbon emission per year as an environmental benefit within retrofitting procedure is obtained.

This study proposes a novel solar assisted absorption cooling (SAAC) system and performs its exergetic analysis and assessment. The system was designed, constructed and tested in Izmir, Turkey. Water was used as refrigerant in the system. The performance of the whole system along with its main components was assessed through exergy analysis method. The results obtained gave the exergy destruction rate, the exergy efficiency in various forms, the relative irreversibility and sustainability index in both charging and discharging processes. A parametric study was also undertaken to investigate the effect of the various dead (reference) state temperatures ranging from 30 degrees C to 42 degrees C with an interval of 4 degrees C on the entire system efficiency. In this context, the exergy efficiency of the whole system varied between 13.1 and 43.2% as the dead state temperatures increase from 30 degrees C to 42 degrees C. The highest relative irreversibility values of 66.1% and 34.6% belonged to the solar collectors and the absorption chiller in charging and discharging processes at a dead state temperature of 34 degrees C, respectively. (C) 2013 Elsevier B.V. All rights reserved.

Direct current compressors are strong candidates to be employed in energy-efficient refrigeration systems, especially for renewable energy powered units, as these compressors do not require additional components such as a power inverter that an alternative current compressor would require. This study represents experimental performance analysis of a direct current type refrigeration compressor implemented in a 79 L refrigerator. Energy usage reduction and operational improvement potential of the direct current compressor via variable speed operation were investigated. Experiments were carried out at variable speed operation and four different constant speed operation modes of the compressor. Temperature, pressure, and power input measurements were obtained every 30 s. The experimental data were analyzed in terms of energy and exergy efficiencies. The comparison showed that variable speed operation of the direct current compressor can be much more efficient than constant speed operation of the direct current compressors, especially at higher speeds.

In this study, for a near-room-temperature magnetic cooling system, a decoupled multi-physics numerical approach (Magnetism, Fluid Flow, and Heat Transfer) is developed using a commercial CFD solver, ANSYS-FLUENT, as a design tool. User defined functions are incorporated into the software in order to take into account the magnetocaloric effect. Magnetic flux density is assumed to be linear during the magnetization and demagnetization processes. Furthermore, the minimum and maximum magnetic flux densities (Bmin and Bmax) are defined as 0.27 and 0.98, respectively. Two different sets of analyses are conducted by assuming an insulated cold heat exchanger (CHEX) and by defining an artificial cooling load in the CHEX. As a validation case, experimental work from the literature is reproduced numerically, and the results show that the current methodology is fairly accurate. Moreover, parametric analyses are conducted to investigate the effect of the velocity of heat transfer fluid (HTF) and types of HTF on the performance of the magnetic cooling system. Also, the performance metrics of the magnetic cooling system are investigated with regards to the temperature span of the magnetic cooling unit, and the cooling load. It is concluded that reducing the cycle duration ensures reaching lower temperature values. Similarly, reducing the velocity of the HTF allows reducing the outlet temperature of the HTF. In the current system, the highest temperature spans are obtained numerically as around 6 K, 5.2 K and 4.1 K for the cycle durations of 4.2 s, 6.2 s and 8.2 s, respectively., Scientific and Technological Research Council of Turkey (TUBITAK 114M829)

AiCARR 50th International Congress -- MAY 10-11, 2017 -- Matera, ITALY, WOS: 000426433900038, 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 W-p. The WWSHP system consists of three main subsystems, 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. (C) 2017 The Authors. Published by Elsevier Ltd., European CommissionEuropean Commission Joint Research Centre [608466]; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113M532]; European CommissionEuropean Commission Joint Research Centre; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK), The presented work was developed within the framework of the two research projects. The first one is "REELCOOP - Research Cooperation in Renewable Energy Technologies for Electricity Generation", co-funded by the European Commission (FP7 EN-ERGY.2013.2.9.1, Grant agreement no: 608466 while the second one is "Design, Construction and Experimental Investigation of a Novel Solar Photovoltaic/Thermal (PV/T)-Assisted Wastewater Heat Pump System (113M532)", fully funded by The Scientific and Technological Research Council of Turkey (TUBITAK). The authors would like to thank European Commission and TUBITAK for the financial support given to the both projects. They also thank Teodosio del Carlo, Elena Rico and Juan Luis Lechon from Onyx Solar in Spain.

3rd International Conference on Energy and Environment Research (ICEER) -- SEP 07-11, 2016 -- Barcelona, SPAIN, WOS: 000400640900026, In this study, performance of a near room temperature magnetic cooling system was investigated experimentally in terms of temperature span. The current setup has a permanent magnet pairs (0.7 Tesla), a magnetocaloric material (Gadolinium) and a heat transfer fluid (water, ethylene glycol and 10% ethanol-water mixing) furthermore solar energy was used as a power source of liner motion of the magnetic system. The obtained results showed that ethanol-water was the best heat transfer fluid and also that optimum magnetization-demagnetization period for the system was found 10 s. (C) 2016 The Authors. Published by Elsevier Ltd., Univ Poltecnica Catalunya, BarcelonaTECH, The Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114M829], The authors would like to thank The Scientific and Technological Research Council of Turkey (TUBITAK) for financial support given to the project entitled "Experimental Performance Evaluation of a Solar Assisted Magnetic Cooling System (114M829)"

Bu çalışmada çiftlik tipi bir süt soğutma tankının, klasik buhar sıkıştırmalı soğutma sistemiyle soğutulmasına alternatif olarak, güneş enerjili bir absorpsiyonlu soğutma sistemiyle soğutulması deneysel olarak incelenmiştir. Çalışmada 1000 litre kapasiteli 2BII sınıfı çiftlik tipi bir süt soğutma tankı kullanılmıştır. Tank tabanı klasik buhar sıkıştırmalı soğutma yapabilecek özellikte olup, tank çevresi ise absorpsiyonlu soğutma sistemine uygun özel ısı değiştirici (rollbond) sistemiyle donatılmış olarak imal edilmiştir. Deneysel çalışmalarda, klasik buhar sıkıştırmalı soğutma sistemi ve hibrit yöntem (içsel enerji depolamalı LiCl?H2O çiftiyle çalışan absorpsiyonlu soğutma ile ardından klasik buhar sıkıştırmalı soğutma sistemi) kullanılarak, süt soğutma tankının ilk ve son sağım soğutma performansları Uluslararası ve Türk standartlarına göre ortaya konulmuştur. Her iki sistemle yapılan soğutmada, ilk sağım soğutması sınır kabul edilen süre içinde tamamlanmıştır. Son sağım soğutması ise, buhar sıkıştırmalı soğutma sistemi ile zamanında tamamlanırken, hibrit yöntemle sınır kabul edilen süreden daha fazla zaman almıştır. Genel olarak, aynı soğutma kapasitesi için klasik buhar sıkıştırmalı soğutma sisteminin özgül enerji ihtiyacı 21,06 Wh/L olurken absorpsiyonlu soğutma sistemi ilaveli hibrit yöntemin özgül enerji ihtiyacı 18,01Wh/L olarak bulunmuştur. Ülkemizin avantajlı konumda olduğu güneş enerjisi, jeotermal enerji gibi yenilenebilir enerji kaynaklarının kullanıldığı absorpsiyonlu soğutma sistemlerinin farklı soğutma uygulamalarında daha fazla yer almasıyla önemli düzeyde enerji tasarrufları sağlamak mümkün olabilecektir., In this study, utilization of a solar energy powered absorption cooling system has been investigated instead of conventional cooling systems for milk cooling purpose as an alternative method. In this study, a novel designed milk tank (1000 liter tank capacity and 2BII performance class) with rollbond type heat exchanger around the wall and conventional heat exchanger bottom of the tank for vapor compression cooling system was used. Performance investigation of the tank has been realized while the first and last milking experiments according to International and National Standards for the milk storage tank. Experimental studies have been realized for the hybrid combination of the conventional (vapor compression) cooling and the LiCl-H2O absorption cooling systems with an internal energy storage ability. According to experiments, the conventional and absorption cooling method were cooled down the milk at the first milking period in the reasonable time interval. On the other hand, while the conventional method was being completed in the reasonable time interval, hybrid method was not able to complete in accepted time limit. Utilization of the hybrid combination of the LiCl-H2O absorption and conventional cooling system showed 18.01 Wh/L specific energy consumption, but conventional cooling system showed 21.06 Wh/L specific energy consumption at the same cooling amount. In Turkey, utilization of solar and geothermal energy powered absorption cooling systems to increase energy savings in different cooling application can be significant method since Turkey has advantages about renewable energy sources such as solar and geothermal energy.

In this study, transfer functions of electronic expansion valve and variable speed scroll compressor in a chiller system are developed based on an experimental analysis. Dynamic behaviours of water temperature at chiller output and refrigerant superheat at evaporator outlet have either the first- or the second-order linear models, respectively. Different from the existing modelling studies in literature novel models are presented for variable speed refrigeration system with scroll compressor and liquid type evaporator. The scroll compressor used in the current study is not produced for variable speed operation however it is operated with some limitations in the range of 30 to 50 Hz through an inverter. Similar restrictions are presented for the electronic expansion valve as 10 per cent to 35 per cent opening range because of operational limitations. To validate transfer functions of the variable speed scroll compressor and electronic expansion valve, mean square error values for all transfer functions are calculated. The mean square error values vary between 0.0126 and 0.3116. In addition, all transfer functions are designed and tested using corresponding proportional–integral–derivative controllers in order to see their applicability. The results indicate that energy savings are a consequence of operating the chiller at smaller frequencies than the basic 50 Hz while partial load occurred.

In this study, usage of a variable speed refrigeration system in latent heat thermal energy storage (LHTES) system is investigated to increase energy storage efficiency. Four different compressor speed control cases are compared to obtain a constant heat transfer fluid (HTF) temperature at the inlet of the energy storage tank. These control cases are (i) control with evaporation temperature, (ii) control with ethylene glycol temperature at the outlet section of evaporator, (iii) control with suction pressure of the compressor and (iv) on/off control. By means of the experimental analysis the best control strategy is obtained as control with Case (ii), in terms of stability of inlet temperature of heat transfer fluid, variations of energy efficiency of LHTES and coefficient of performance (COP) of the system. While the Case (ii) provides the most stabile inlet temperature of HTF, Case (iv) represents the worst stability. Besides, the highest energy efficiency (99.0%), exergy efficiency (87.0%) and COP (2.05) values observed in Case (ii). Additionally, the time period to reach the set value is nearly 50 min in Case (i), Case (iii) and Case (iv) on the other hand this unstable initial time period becomes nearly 25 min for Case (ii). As a result, variable speed compressor should be controlled with Case (ii) to stabilize ethylene glycol-water solution temperatures as well as increase efficiency and COP of the system. (C) 2011 Elsevier Ltd and IIR. All rights reserved.

13th REHVA World Congress, CLIMA 2019 -- 26 May 2019 through 29 May 2019 -- 150961, In this study, a solar powered mechanical ventilation unit has investigated and tested in terms of efficiency and performance. Test unit can be divided into two parts, the first one is ventilation unit with 370 m3/h max airflow rate and max 167 W fan power provides fresh air for a residency and recovers heat from the climatized exhaust air. Total area is 70 m2 for the residency and total occupant is four. The second part of the test system is solar energy power system with two 325 W polycrystalline photovoltaic panels, an inverter and two batteries. The mechanical ventilation unit has energized by a solar photovoltaic system; if the solar energy is not available then ventilation unit has connected to the national electricity grid. This is an alternative option to consumers to use electricity by the grid in case the PV system does not produce enough energy because of the usage or the technical problems or the weather conditions based on the seasons. On the other hand, in some cities, number of photovoltaic panels rolled up upper number according to solar energy potential and therefore resulted excess electricity has assumed to sell to the national grid. According to the results, the test system is able to operate at maximum ventilation necessity and power consumption without grid connection in Izmir. Furthermore, we have compared Izmir and Romania in accordance with feasibility for the same mechanical ventilation system at max flow rate and required ventilation rate is determined depends on daily usage scenario of the room. © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0

In this paper, we perform Simulated Annealing (SA) algorithm for optimizing size of a PV/wind integrated hybrid energy system with battery storage. The proposed methodology is a heuristic approach which uses a stochastic gradient search for the global optimization. In the study, the objective function is the minimization of the hybrid energy system total cost. And the decision variables are PV size, wind turbine rotor swept area and the battery capacity. The optimum result obtained by SA algorithm is compared with our former study's result. Consequently, it is come up with that the SA algorithm gives better result than the Response Surface Methodology (RSM). The case study is realized for a campus area in Turkey. © 2009 Elsevier Ltd.

In this study, control algorithm, based on fuzzy logic, for compressor speed and opening percentage of electronic expansion valve (EEV), was investigated. The main aim of this study is to increase efficiency of the chiller system, having variable speed scroll compressor (VSSC) and EEV. Current chiller system has an air cooled condenser, a shell-tube liquid evaporator, and a vertical scroll compressor. Flow of the refrigerant R134a was controlled by EEV in the system. Chiller systems are designed for working at maximum load conditions; on the contrary, these plants work under partial load conditions most of their life cycle by means of thermostatic control. Refrigeration capacity modulation methods, such as variable speed compressors, allow to match continuously the compressor refrigeration capacity to the load, determining an energy saving according to classical thermostatic control. In this study, compressor speed was controlled with fuzzy logic algorithm according to chiller water output temperature and EEV opening percentage was controlled with fuzzy logic algorithm according to refrigerant superheat value at outlet of the evaporator. Compressor speed has been changed between 30 and 60 Hz and EEV opening percentage has been changed between 10 and 45% of the maximum opening percentage. In fact, the chiller plant was operated as on/off at 50 Hz fixed speed by a thermostat. During the study, it has been operated as variable speed by adding PWM inverter. In the present study, fuzzy logic controlled variable speed chiller system exhibited 17% coefficient of performance increase according to the thermostatic controlled fixed speed system. Also, better water temperature control was obtained via fuzzy controlled VSSC. Copyright (C) 2009 John Wiley & Sons, Ltd.

Heat pumps (HPs) are part of the environmentally friendly technologies using renewable energy and have been utilized in the developed countries for years. Wastewater is seen as a renewable heat source for HPs. At the beginning of the 1980s, waste (sewage) water source heat pumps (WWSHPs) were widely applied in North European countries like Sweden and Norway and partially applied in China. In the past two decades, the WWSHP has become increasingly popular due to its advantages of relatively higher energy utilization efficiency and environmental protection. The present study comprehensively reviews WWSHP systems in terms of applications and performance assessments including energetic, exergetic, environmental and economic aspects for the first time to the best of the authors’ knowledge. In this context, a historical development of WWSHPs was briefly given first. Next, wastewater potential and its characteristics were presented while a WWSHP system was introduced. The previously conducted studies on WWSHPs were then reviewed and classified in a tabulated form. Finally, some concluding remarks were listed. The COP values of the reviewed studies ranged from 1.77 to 10.63 for heating and 2.23 to 5.35 for cooling based on the experimental and simulated values. The performance assessments are mostly made using energy analysis methods while the number of exergetic evaluations is very low and has not been comprehensively performed. It is expected that the comprehensive review here will be very beneficial to those dealing with the design, analysis, simulation and performance assessment of WWSHP systems.

Despite the high theoretical performance limits of magnetic refrigeration systems, coefficient of performance (COP) of these systems can be lower due to abortive magnet and magnetocaloric material (MCM) assembly orientation and space limitation. To address both of these problems, a rotary-type magnetic cooling system with varied geometric properties was modelled and simulated. Heat transfer from the MCM, which was selected to be gadolinium (Gd), to the working fluid, was considered as volumetric energy generation. Three different geometries of disc-MCM assembly were studied where the inner and outer radii were selected as 5, 10, 15 mm, and 10, 15, 20 mm, respectively. It was observed that the gradient between steady-state temperature and the room temperature decreases with decreasing gadolinium-to-disc area ratio. Conductive heat transfer through the thickness of the disc was found to be inconsiderable compared with the convective heat transfer through the top surface.

This study represents experimental performance analyses of an alternative current (AC) and a direct current (DC) refrigeration compressors implemented in a 79 liter refrigerator. Experiments were carried out at continuously running (ON) and periodically running (ON/OFF) operation modes. Data was analyzed and a comparison in terms of cooling capacity, power input, coefficient of performance (COP), Carnot COP, and exergy efficiency was conducted. The comparison showed that DC compressors can be much more efficient than AC compressors in refrigeration units.

Characteristics of site-specific solar irradiation is required to optimize a solar energy system. If no tracking system is used, the amount of electricity or heat produced by solar energy depends on the total solar radiation on a tilted surface. Although pyranometer measures direct plus diffuse solar radiation on a horizontal surface, there are many locations where diffuse radiation is not measured. Also, diffuse radiation is necessary to determine the total radiation on a tilted surface. Therefore, in this study, new correlations for diffuse solar radiation is proposed as a function of atmospheric parameters for Urla (Izmir, Turkey). After applying the statistical procedure on the measured data, seven new correlations are proposed for the ratio of hourly average diffuse and total radiation. Also, the ratio of monthly average daily diffuse and total radiation for this region is proposed.

The most critical problem in the world is to meet the energy demand, because of steadily increasing energy consumption. Refrigeration systems` electricity consumption has big portion in overall consumption. Therefore, considerable attention has been given to refrigeration capacity modulation system in order to decrease electricity consumption of these systems. Capacity modulation is used to meet exact amount of load at partial load and lowered electricity consumption by avoiding over capacity using. Variable speed refrigeration systems are the most common capacity modulation method for commercially and household purposes. Although the vapor compression refrigeration designed to satisfy the maximum load, they work at partial load conditions most of their life cycle and they are generally regulated as on/off controlled. The experimental chiller system contains four main components: compressor, condenser, expansion device, and evaporator in Fig.1 where this study deals with effects of different control methods on variable speed compressor (VSC) and electronic expansion valve (EEV). This chiller system has a scroll type VSC and a stepper motor controlled EEV.

Energy is an important fact for a country for both its socio-economic development and economic growth. Main energy source on earth is the fossil fuels. However, the usage of fossil fuels causes global warming whose negative effects have recently been felt by all over the world. Also, because it is limited on earth, increased energy demand and high energy prices increase concerns on fossil fuels. For instance, petroleum reservoirs are present only in few countries therefore the other countries mostly purchase petroleum from these countries more than their production amount. Hence, decrease of fossil fuel reservoirs may create a new ‘energy crisis’ and/or “energy wars” as in 1970s in near future. For a sustainable world the usage of fossil fuels must be decreased, in fact ended. Instead, the usage of renewable energy sources must be increased. As it is known, the interest in renewable energy sources has increased because it does not cause greenhouse effect in contrary to the fossil fuels. These energy sources are indigenous, environmental friendly and, they help to reduce the usage of fossil fuels. Solar, wind, wave, biomass and geothermal energies are renewable energy sources. Sun is the source of all energies. Solar energy is usually used in two aims: for thermal applications and for electricity production. Wind is the indirect form of solar energy and is always replenished. The past and the predicted amount of global renewable energy source status by 2040 are presented in Table 1. As seen in this table the renewable energy consumption is predicted to increase in the future. There are several studies on renewable energy sources and hybrid combination of these sources for electricity production. Electricity has high cost mostly due to centralized energy systems which operate mostly on fossil fuels and require large investments for establishing transmission and distribution of grids that can penetrate remote regions (Deepak, 2009). Unlike the centralized energy systems, decentralized energy systems are mostly based on renewable energy sources. They operate at lower scales (a few kWh scale) both in the presence and absence of grid, and easily accessible to remote locations due to generation of

O. Ekren, A. Yilanci, E. Cetin, H. K. Ozturk. Experimental Performance Evaluation of a PV-Powered Refrigeration System // Electronics and Electrical Engineering. - Kaunas: Technologija, 2011. - No. 8(114). - P. 7-10. This paper presents cool-down, and steady state performance of a 76 W direct current operated household refrigerator powered by a photovoltaic (PV) solar panel and a battery bank. Exergy method has been conducted to investigate of the performance of the PV powered household refrigerator. Experiments are conducted with different cooling loads. In use of this type system, it can be said that over-loaded condition in the refrigerator should be avoided. From the obtained results, it is seen that exergy efficiency of the system is very low due to the low energy conversion and exergy efficiencies of the PVs. This situation is also seen from exergy destruction values. For all cases, exergy is destroyed highly in the PVs. III. 1, bibl. 8, tabl. 2 (in English; abstracts in English and Lithuanian).

In this paper, an optimum sizing procedure of autonomous hybrid (wind+solar) energy system is presented which can be used to satisfy the requirements of given load distribution. The main purpose of this study is to find out an appropriate wind-photovoltaic hybrid energy system to satisfy electricity consumption of GSM (Global System for Mobile communication) base station at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. To do this, monthly average daily solar radiation and wind speed data are collected. The monthly average wind speeds are measured at 10m height during 3 years period on Izmir Institute of Technology Campus Area. The monthly average wind speed values are obtained between 5.7 and 7.7m/s, on the other hand, the monthly average daily value of solar radiations on horizontal surfaces are ranged from 1.4 to 6.9kWh/m 2 at Izmir Institute of Technology Campus Area. The hybrid system considered in the present analysis consists of one 5kW nominal power wind energy conversion systems (WECS), 21.82m 2 of photovoltaic (PV) panels (18 mono crystal PV panels each having 75W power output) together with a battery storage system.

In this paper, size of a PV/wind integrated hybrid energy system with battery storage is optimized under various loads and unit cost of auxiliary energy sources. The optimization is completed by a simulation based optimization procedure, OptQuest, which integrates various heuristic methods. In the study, the main performance measure is the hybrid energy system cost. And the design parameters are PV size, wind turbine rotor swept area and the battery capacity. The case study is realized for Izmir Institute of Technology Campus Area, Urla, Turkey. The simulation model of the system is realized in ARENA 12.0, a commercial simulation software, and is optimized using the OptQuest tool in this software. Consequently, the optimum sizes of PV, wind turbine and battery capacity are obtained under various auxiliary energy unit costs and two different loads. The optimum results are confirmed using Loss of Load Probability (LLP) and autonomy analysis. And the investment costs are investigated how they are shared among those four energy sources at the optimum points. © 2009 Elsevier Ltd. All rights reserved.

WOS: 000265033400008, This paper aims to show an optimum sizing procedure of autonomous PV/wind hybrid energy system with battery storage and a break-even analysis of this system and extension of transmission line. We use net present value (NPV) method for the comparison of autonomous hybrid energy system and extension of transmission line cases. The case study is completed for the satisfaction of the electricity consumption of global system for mobile communication base station (GSM) at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. First, we optimize the PV/wind energy system using response surface methodology (RSM) which is a collection of statistical and mathematical methods relying on optimization of response surface with design parameters. As a result of RSM, the optimum PV area, wind turbine rotor swept area, and battery capacity are obtained as 3.95 m(2), 29.4 m(2), 31.92 kW h, respectively. These results led to $37,033.9 hybrid energy system cost. Second, break-even analysis is done to be able to decide the optimum distance where the hybrid energy system is more economical than the extension of the transmission line. The result shows that, if the distance between national electricity network and the GSM base station location where the hybrid energy system is assumed to be installed is at a distance more than 4817 m, the installation of hybrid energy system is more economical than the electricity network. (C) 2008 Elsevier Ltd. All rights reserved.

This paper aims to show the use of the response surface methodology (RSM) in size optimization of an autonomous PV/wind integrated hybrid energy system with battery storage. RSM is a collection of statistical and mathematical methods which relies on optimization of response surface with design parameters. In this study, the response surface, output performance measure, is the hybrid system cost, and the design parameters are the PV size, wind turbine rotor swept area and the battery capacity. The case study is realized in ARENA 10.0, a commercial simulation software, for satisfaction of electricity consumption of the global system for mobile communications (GSM) base station at Izmir Institute of Technology Campus Area, Urla, Turkey. As a result, the optimum PV area, wind turbine rotor swept area, and battery capacity are obtained to be 3.95 m2, 29.4 m2, 31.92 kWh, respectively. These results led to $37,033.9 hybrid energy system cost, including auxiliary energy cost. The optimum result obtained by RSM is confirmed using loss of load probability (LLP) and autonomy analysis. © 2008 Elsevier Ltd. All rights reserved.

In this study, exergy analysis and environmental impact assessment of a Photovoltaic (PV)-hydrogen production system and its components are carried out. Actual data measured in the system are employed for analysis purposes. Daily hydrogen production amount from solar energy through water electrolysis is 4.43 kg. The average system exergy efficiency is determined to be 3.18%. It is found that the highest exergy destruction occurs in the PVs. In the PVs, 93.3% of the total exergy input (incoming solar exergy) is destroyed. The second highest exergy destruction is from the electrolyser as 4.76% of the total exergy destruction. The average percent exergy destructions are 1.29% and 1.94% for charge controllers-inverter and batteries, respectively. Copyright © 2011 Inderscience Enterprises Ltd.