Article
Thermodynamics
Shady M. Henein, Ahmed A. Abdel-Rehim
Summary: In this study, the effect of using MgO/MWCNT hybrid nanofluid on the thermal performance of the evacuated tube solar collector was investigated. The results showed that increasing the weight ratios of MWCNTs nanoparticles and volume flow rate improved the energy and exergy efficiencies of the collector. Furthermore, MgO/MWCNT (50:50) hybrid nanofluid performed better than other hybrid nanofluids at all volume flow rates.
CASE STUDIES IN THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Koosha Ensafjoee, Roonak Daghigh
Summary: Liquid desiccant air conditioners (LDAC) are environmentally friendly and energy-efficient. A prototype of an internally heated bubble column regenerator has been constructed to address the corrosion issue and improve the overall performance. Experimental results indicate that the initial desiccant concentration has the highest impact on the device's performance, increasing air flow rate leads to higher water extraction, and air injection depth has no significant impact.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Mahmoud Eltaweel, Ahmed A. Abdel-Rehim, Ahmed A. A. Attia
Summary: The continuous increase in energy demand poses a challenge for the future, leading to a focus on efficient methods for utilizing renewable sources such as solar energy. Evacuated tube and flat-plate solar collectors are simple and cost-effective for domestic use, and enhancing heat transfer with nanofluids can improve performance, especially at low temperatures. Comparisons in the literature show different behaviors between the two collector types based on working conditions. Studies on the comparison of stationary collectors using nanofluids are scarce, but research in this area can help evaluate energy and exergy efficiencies, showing potential for improvement with Multi-walled Carbon Nanotubes/water nanofluid at varying mass flux rates.
APPLIED THERMAL ENGINEERING
(2021)
Article
Green & Sustainable Science & Technology
Sumit Kumar, Arun Kumar Tiwari
Summary: This study demonstrated the impact of hexagonal Boron Nitride nanofluid on the thermal performance of a solar collector. The results showed that the nanofluid with a volumetric concentration of 1.5% achieved the highest energy efficiency at a mass flow rate of 0.051 kg/s, which was approximately 84% higher than water.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2022)
Article
Green & Sustainable Science & Technology
Ashok Kumar Singh, Samsher
Summary: This paper examines an eco-design criterion for a novel solar desaltification setup and proposes a modified combination of parabolic concentrator to improve its performance. The results show significant improvements in temperature, energy efficiency, and cost.
ENVIRONMENT DEVELOPMENT AND SUSTAINABILITY
(2023)
Article
Green & Sustainable Science & Technology
Santanu Malakar, Vinkel Kumar Arora, Prabhat K. Nema
Summary: The study designed and developed an evacuated tube collector-based solar dryer with heat pipe for drying garlic cloves. Experimental results showed that the dryer performed best at an air flow velocity of 2 m/s, capable of efficiently drying garlic cloves within 8 hours with a short payback period of 1.3 years.
Article
Thermodynamics
Cong Lai, Huichao Zhu, Houcheng Zhang, Ziyang Hu
Summary: Short lifespan and low thermal efficiency have hindered the development of solar desalination systems. A novel hybrid system model combining an efficient evacuated U-tube solar collector and direct contact membrane distillation (DCMD) is proposed. The model is validated and performance indicators including permeate flux, energy efficiency, and exergy efficiency are deduced. The performance of the system is predicted under the weather conditions of Ningbo city, China, and the effects of various parameters are investigated. The EUSC/DCMD coupling system shows promise as an alternative for small-scale freshwater generation.
APPLIED THERMAL ENGINEERING
(2023)
Article
Green & Sustainable Science & Technology
Oveepsa Chakraborty, Sujit Roy, Biplab Das, Rajat Gupta
Summary: The study finds that a parabolic solar trough collector with a helical absorber tube performs better in terms of heat transfer rate, efficiency, and exergy efficiency compared to traditional collectors with smooth absorber tubes. The presence of a helical absorber tube increases the net surface area of the absorber, leading to a significant enhancement in useful heat transfer rate. Overall efficiencies are 3.5%-10% higher for the helical absorber tube based PTC, showing the advantages of this design over the traditional smooth absorber tube design.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2021)
Article
Energy & Fuels
Arun Uniyal, Yogesh K. Prajapati, Siddharth Suman
Summary: Three-dimensional computational fluid dynamics simulation was used to compare the heat transfer and melting characteristics of a copper U-tube based evacuated tube solar collector filled with different phase change materials. The results showed that the evolution of natural convection current and vortices within the collector differed for each phase change material, affecting their melting and heat transfer behavior. Lauric acid had the highest liquid fraction while stearic acid had the lowest. Increasing the mass flow rate of the heat transfer fluid resulted in a decrease in the liquid fraction of paraffin wax.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Engineering, Mechanical
A. Veera Kumar, T. Arjunan, D. Seenivasan, R. Venkatramanan, S. Vijayan
Summary: The study found that the evacuated tube solar air collector with inserted baffle performs well even in poor insolation periods, with maximum outlet air temperature reaching 80.5 degrees Celsius and a thermal efficiency of 55.4%. However, the maximum exergy efficiency decreases with increasing mass flow rate of air.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART E-JOURNAL OF PROCESS MECHANICAL ENGINEERING
(2021)
Article
Green & Sustainable Science & Technology
S. Mojtaba Tabarhoseini, M. Sheikholeslami
Summary: This research focused on examining the thermal characteristic of a thermosyphon evacuated tube collector for domestic use and modifying the structure by adding longitudinal fins within the absorber to enhance thermal efficiency. Computational fluid dynamics were used to study the efficacy of water-based Cu and MWCNT nanofluids in different volume fractions on the collector's performance. The analysis also discussed the impact of variations in solar radiation incidence angles on fluid flow structure and average tank temperature, revealing improvements in heat transfer and system's thermal efficiency with the employment of longitudinal fins.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2022)
Article
Energy & Fuels
Abhishek Tiwari, Amit Kumar
Summary: This study experimentally compares the thermal performance of two solar air heaters, one integrated with phase change material (PCM) and the other without. The results show that the solar air heater with PCM achieves a higher maximum temperature of hot air (112°C) compared to the one without PCM (100°C). Additionally, the use of PCM increases the efficiency of the solar air heater and reduces CO2 emissions.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Environmental Sciences
Sathiya Satchi Christopher, Vellaisamy Kumaresan
Summary: This study improved the energy and exergy efficiencies of solar water heating systems by utilizing cascaded arrangement of phase change materials (PCMs), which played a key role in reducing heat losses and enhancing performance.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2022)
Article
Green & Sustainable Science & Technology
Inderjeet Singh, Sachit Vardhan
Summary: The article evaluates the performance of an Evacuated Tube Collector solar air heater with Helical Coiled Inserts (ETC-HI) compared to a simple ETC solar air heater. Results show that the ETC-HI heater achieved higher outlet temperature and thermal efficiency than the simple ETC heater, despite an increase in pressure losses. Overall, the ETC-HI solar air heater outperforms the simple ETC solar air heater in terms of thermal efficiency and effective efficiency.
Article
Energy & Fuels
Yong Li, Xiaoyu Liang, Wang Song, Tong Li, Dengjia Wang, Yanfeng Liu
Summary: The thermal performance of a PCM-filled U-type ETC with fins was investigated and design parameters were optimized. The results showed that filling PCM inside the ETC can extend the hot water supply time and reduce the peak temperature of the heat transfer fluid. Additionally, it was found that a higher flow rate of the heat transfer fluid can shorten the hot water supply time.
Article
Environmental Sciences
Tomasz Cholewa, Alicja Siuta-Olcha
Summary: The paper analyzes long-term field research results on energy consumption and efficiency of heating systems in buildings equipped with residential thermal stations, and explores the potential to increase the share of renewable energy sources.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2021)
Article
Construction & Building Technology
Tomasz Cholewa, Alicja Siuta-Olcha, Andrzej Smolarz, Piotr Muryjas, Piotr Wolszczak, Rafal Anasiewicz, Constantinos A. Balaras
Summary: The authors propose a new simplified method for generating energy characteristics of buildings and their heating systems. The method only requires inputs of actual heat supplied to the heating system and local outdoor weather conditions, and outputs a building energy model in terms of an equivalent outdoor temperature. This method can accurately determine the duration and amount of heat power supplied to a building while minimizing the impact of occupants and internal heat gains.
ENERGY AND BUILDINGS
(2021)
Article
Energy & Fuels
Tomasz Cholewa, Agnieszka Malec, Alicja Siuta-Olcha, Andrzej Smolarz, Piotr Muryjas, Piotr Wolszczak, Lukasz Guz, Marzenna R. Dudzinska, Krystian Lygas
Summary: The paper introduces a simple method to consider the impact of solar heat gains on heating of buildings, focusing on optimizing heating consumption by effectively utilizing solar heat gains. Field research on seven buildings showed that narrowing down the input data range in building energy model calculations can improve calculation accuracy.
Article
Green & Sustainable Science & Technology
Tomasz Cholewa, Alicja Siuta-Olcha, Andrzej Smolarz, Piotr Muryjas, Piotr Wolszczak, Lukasz Guz, Constantinos A. Balaras
Summary: This study introduces a simple new method to enhance the energy efficiency of existing buildings by predicting short-term heat power demand for optimal operation of heating systems. The addition of equivalent indoor temperature in the prediction method improves accuracy, and five profiles were proposed to select the most accurate one for specific buildings.
JOURNAL OF CLEANER PRODUCTION
(2021)
Article
Energy & Fuels
Pawel Michnikowski, Tomasz Cholewa
Summary: The study proposed two easily applicable methods to address issues with HCAs in existing buildings, and by comparing results from a multi-family building in Poland, it was found that the new methods achieved higher correlation coefficients and eliminated potential issues present in existing methods.
Article
Energy & Fuels
Agnieszka Malec, Tomasz Cholewa, Alicja Siuta-Olcha
Summary: Domestic hot water preparation is a significant source of energy consumption in households, with the design of the storage tank playing a crucial role in system efficiency. Experimental results show that an inlet with a downward-facing elbow and single plate, as well as placing a partition in the lower part of the tank, can increase energy efficiency and reduce energy demand for heating water in the tank.
Article
Construction & Building Technology
Tomasz Cholewa, Marco Dell'Isola, Laura Canale, Giorgio Ficco, Pawel Michnikowski, Alicja Siuta-Olcha, Aleksandra Olszewska, Gabriela Sadowska, Marzenna R. Dudzinska
Summary: This study compared the heat cost allocation methods in two multifamily buildings and found that buildings with heat cost allocators were able to achieve 24.2% lower heat consumption compared to buildings without heat cost allocators. Furthermore, it was demonstrated that by reducing the supply temperature of the heating medium, additional energy savings could be obtained.
ENERGY AND BUILDINGS
(2022)
Article
Green & Sustainable Science & Technology
Tomasz Cholewa, Alicja Siuta-Olcha, Andrzej Smolarz, Piotr Muryjas, Piotr Wolszczak, Lukasz Guz, Martyna Bocian, Constantinos A. Balaras
Summary: Accurately predicting and regulating energy supply to buildings can improve energy efficiency, but there is currently no low-cost, easy-to-install and operate system for forecasting and controlling heating systems for existing buildings. This study shares the experiences of implementing a forecast control system in two buildings in Poland, taking into account actual energy models, heating systems, user behavior and preferences, and weather forecasts. The system achieved an average energy savings of 15%.
JOURNAL OF CLEANER PRODUCTION
(2022)
Article
Green & Sustainable Science & Technology
Alicja Siuta-Olcha, Tomasz Cholewa, Miroslaw Gomolka, Piotr Kolodziej, Dorte Skaarup Ostergaard, Svend Svendsen
Summary: This paper presents the results of several years of field research on the modernization of existing district heating systems in 13 multi-family buildings. The study showed that decommissioning bifunctional area substations and using compact heat exchanger thermal stations with weather automation can significantly improve energy efficiency.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2022)
Review
Energy & Fuels
Constantinos A. Balaras, Elena G. Dascalaki, Ioanna Psarra, Tomasz Cholewa
Summary: The European Union (EU) and its member states are committed to reducing primary energy consumption and emissions in line with the Paris Agreement. This paper reviews different methods of calculating the primary energy factor (PEF) for electricity and provides correlations for projecting future PEF values. Case studies are presented for Greece and Poland.
Article
Energy & Fuels
Tomasz Cholewa, Alicja Siuta-Olcha, Anna Zyczynska, Aleksandra Specjal, Pawel Michnikowski
Summary: Heat cost allocation is commonly used in existing buildings supplied by centralized sources of heating/cooling and provided with individual metering systems. However, fairness in this process depends on the methods used to allocate costs among dwellings. This paper presents different methods for estimating maximum and minimum variable heating costs in multifamily buildings, based on input data availability. The authors also provide recommendations on the accuracy of the proposed methods.
Article
Construction & Building Technology
Tomasz Cholewa, Alicja Siuta-Olcha, Andrzej Smolarz, Piotr Muryjas, Piotr Wolszczak, Lukasz Guz, Martyna Bocian, Gabriela Sadowska, Wiktoria Lokczewska, Constantinos A. Balaras
Summary: The priority for achieving carbon neutral buildings by 2050 is to improve energy efficiency in existing buildings by using easily applicable measures based on long-term field research. One such measure is the forecast control of heating systems, which can be integrated into existing weather based controls. However, there is a lack of long-term evaluation and detailed analysis of this system, which hinders its widespread adoption. This paper presents data from a long-term field evaluation of an innovative forecast control of heating systems, showing significant energy savings and short payback time.
ENERGY AND BUILDINGS
(2023)