• Energy Research

The optical and thermal performances of energy-saving glazing require improvement to reduce peak thermal load and increase solar energy conversion and management efficiency. Herein, it is indispensable to develop novel composite materials that designate the ability to achieve multifunction by thermal load migration as well as radiation transmittance modulation. This study developed a nanoparticle-enhanced phase change material (NEPCM) with spectrally selective and phase change functions. A data-driven algorithm is first developed to evaluate the solar-weighted absorption fraction, integrated irradiance, and spectral irradiance for the considered nanoparticles. The base fluids, nanoparticle diameter, concentrations, and proportions are taken into account in the program, and adjustments to the properties of NEPCM can be easily made. The NEPCM properties exhibit a high blocking performance of near-infrared solar radiation by 30.9%, while keeping visible transmittance at 51.8% using ATO-Al2O3 NEPCM. Furthermore, the photothermal conversion performance of a NEPCM-filled energy-saving prototype window is explored, which yields a heat absorption rate of up to 0.27 °C/min when the solar irradiance is 800 W/m2. In addition, the energy consumption of transparent envelopes with NEPCM filler in a full-scale building is investigated. The results show that NEPCM regulated glazing potentially provides annual heating energy-saving from 5.1 to 41.7 kWh·m−2·year−1 in three representative climatic conditions in different global locations. Outcomes on the spectrally selective capabilities of the energy-saving window provide ideas for advancing the development of low-carbon transparent building envelopes.

Abstract Glazing units are important for providing passive solar gain and air ventilation in buildings, but their thermal performance is very poor compared to other building components, which results that energy loss from building envelope becomes much more drastic when the glazing area is large. Incorporating phase change material (PCM) in the glazing unit is an effective approach to increase its thermal performance. The glazing unit containing PCM can absorb part of the solar radiation for thermal energy storage while letting the visible radiation enter the indoor ambient for daylighting, which results in reduction of the temperature fluctuations and improvement of the thermal comfort of indoor occupants. A lot of researchers investigated optical and thermal performance of window systems containing PCM in buildings. However, there is a lack of published research review including numerical methods of optical and thermal performance and physical parameters of PCM used in the glazing units, especially for the optical performance of glazing units containing PCM. The present work reviews the experimental and simulation researches on the optical and thermal performance of glazing units containing PCM and discusses the employed research methods, mathematical models and important conclusions drawn. Finally, the challenges and future works of glazing units containing PCM are addressed.

Abstract The main objective of this review paper is to present the historical development, current utilization, practices and opportunities of geothermal energy in Algeria. Algeria has relatively abundant geothermal resources of low-enthalpy type that could form part of the total energy network of the country. Algeria is the leading country of the direct use of geothermal energy in Africa with a total amount reaching 54.64 MWt installed thermal power, and also among the first five countries in the world in air conditioning application. The main utilization field of geothermal energy in Algeria is balneology, which accounts for about 82% of the total geothermal power utilization, the remaining 18% of the energy is consumed for other purposes such as space heating, heat pumps and fish farming. In this study, the existing literature and current practices of the Algeria’s geothermal resources are reviewed and it is revealed that geothermal energy development remained almost stagnant over the past two decades in Algeria although there is a large potential and resources available in the country. Furthermore, geothermal energy use and latest technologies around the world have been summarized. This study elucidates the influencing factors in the development of geothermal energy in Algeria and suggests the development roadmap and a number of measures that can enhance the development of this significant energy source.

A hybrid solar photovoltaic-thermal collector is the combination of a solar thermal unit and a photovoltaic panel for the simultaneous generation of heat and electricity. In these systems, a fluid is used to cool photovoltaic panels and, thus, prevent their reduction of electrical efficiency. The hot fluid leaving the system can also be used in various kinds of engineering applications, from agriculture to heating, ventilation and air conditioning units, and process heat in utilities. Coolants used in photovoltaic-thermal units include air, water and nanofluids, among which air is less efficient than water and nanofluids due to its low specific heat capacity. Although extensive research has been done on the exergy performance of photovoltaic-thermal units, the number of published review articles in this field is very limited. This paper presents a critical review with some recommendations for future research on the topic of exergy examination of water-based and nanofluid-based photovoltaic-thermal units. As a first step, the concept and mathematical exergy relations are introduced. Then, water-based and nanofluid-based photovoltaic-thermal units are exergetically discussed in detail, followed by the description of novel units. At the end of each section, some suggestions are presented for future exergy examination of those types of photovoltaic- thermal units.

Background: The technology of underground in-situ electric heating for oil shale extraction requires a large amount of electrical energy, which is one of the important factors restricting its further development. In this paper, a microgrid system is proposed, which combines renewable energy sources with conventional ones, to supply electricity for the underground in-situ electric heating installations of oil shale. Methods: The system takes the annual net present value as the evaluation index to determine the optimal solution considering the effects of oil shale electric heating well spacing, oil shale extraction area, and diesel price. Significant findings: The results showed that the spacing of electric heating wells plays a significant role in energy requirement, an increment of 271,195.00$ in the average annual costs is noted when 12 m of the spacing is considered instead of 10 m. Moreover, diesel fuel prices remarkably affect the annual costs, and increasing diesel price from 0.4 to 0.8 $ per liter causes an increase of 58.5% in the average annual costs. Furthermore, this situation increases the annual wasted electricity ratio by 2.96-folds. This study provides a useful reference for decision-makers to design the power supply scheme for underground in-situ electric heating of oil shale.

La présente recherche étudie la viabilité technico-économique de deux cas de systèmes énergétiques hybrides pour des solutions énergétiques durables dans une zone urbaine connue pour son ensoleillement abondant. Ces cas impliquent des combinaisons de photovoltaïque (PV) et de biomasse, avec des composants supplémentaires tels qu'un électrolyseur et une pile à combustible (FC). Le cas 1 comprend le PV/biomasse/électrolyseur, tandis que le cas 2 comprend le PV/biomasse/pile à combustible/électrolyseur/batterie, visant à produire de l'électricité et de l'hydrogène. Cet article a analysé les demandes d'énergie industrielle pendant les périodes hors saison, de mi-saison et de haute saison. Le système optimal pour le cas 2 est le plus fiable avec un panneau photovoltaïque de 23645 kW, un générateur de biogaz de 3800 kW, un convertisseur de 3821 kW, une pile à combustible de 250 kW, un électrolyseur de 600 kW, un réservoir de stockage d'hydrogène de 600 kg (Htank) et un système de secours de 30 batteries avec une stratégie d'envoi CC pour les consommateurs hors saison. Pour les utilisateurs en haute saison, le système dispose de 23789 kW de panneaux photovoltaïques, de 3800 kW de générateurs de biogaz, de 3861 kW de convertisseurs, de 250 kW de FC, de 1000 kW d'électrolyseur, de 1000 kg de Htank et de 30 batteries de réserve avec un plan d'expédition LF. Les résultats de la recherche suggèrent que l'utilisation de PV/biomasse/FC/électrolyseur/batterie est une stratégie plus réalisable et économique en raison des avantages du système. L'augmentation estimée du LCOE a été causée par la hausse du taux d'actualisation et des prix du carburant. La presente investigación investiga la viabilidad tecno-económica de dos casos de sistemas de energía híbrida para soluciones energéticas sostenibles en una zona urbana conocida por su abundante luz solar. Estos casos involucran combinaciones de energía fotovoltaica (PV) y biomasa, con componentes adicionales como un electrolizador y una celda de combustible (FC). El caso 1 comprende PV/biomasa/electrolizador, mientras que el caso 2 incluye PV/biomasa/pila de combustible/electrolizador/batería, con el objetivo de producir electricidad e hidrógeno. Este documento analizó las demandas de energía industrial en los períodos de temporada baja, media y alta. El sistema óptimo para el caso 2 es el más fiable con un panel fotovoltaico de 23645 kW, un generador de biogás de 3800 kW, un convertidor de 3821 kW, una pila de combustible de 250 kW, un electrolizador de 600 kW, un tanque de almacenamiento de hidrógeno de 600 kg (Htank) y un sistema de respaldo de 30 baterías con una estrategia de envío de CC para consumidores fuera de temporada. Para los usuarios de temporada alta, el sistema cuenta con 23789 kW de paneles fotovoltaicos, 3800 kW de generadores de biogás, 3861 kW de convertidores, 250 kW de FC, 1000 kW de electrolizador, 1000 kg de Htank y 30 bancos de salas de respaldo de baterías con un plan de despacho LF. Los resultados de la investigación sugieren que la utilización de PV/biomasa/FC/electrolizador/batería es una estrategia más factible y económica debido a los beneficios del sistema. El aumento estimado en el LCOE fue causado por el aumento de la tasa de descuento y los precios del combustible. The present research investigates the techno-economic viability of two cases of hybrid energy systems for sustainable energy solutions in an urban area known for its abundant sunlight. These cases involve combinations of photovoltaic (PV) and biomass, with additional components such as an electrolyzer and fuel cell (FC). Case 1 comprises PV/biomass/electrolyzer, while Case 2 includes PV/biomass/fuel cell/electrolyzer/battery, aiming to produce electricity and hydrogen. This paper analyzed industrial power demands across off-season, middle-season, and peak-season periods. The optimal system for case 2 is the most reliable one with a 23645-kW PV panel, a 3800-kW biogas generator, a 3821-kW converter, a 250-kW fuel cell, a 600-kW electrolyzer, a 600-kg hydrogen storage tank (Htank), and a 30-battery backup system with a CC send-off strategy for off-season consumers. For peak-season users, the system has 23789-kW of PV panels, 3800-kW of biogas generators, 3861-kW of converters, 250-kW of FC, 1000-kW of electrolyzer, 1000-kg of Htank, and 30 battery backup room banks with an LF dispatch plan. The research findings suggest that utilizing PV/biomass/FC/electrolyzer/battery is a more feasible and economical strategy due to system benefits. The estimated increase in the LCOE was caused by the rising discount rate and fuel prices. يبحث البحث الحالي في الجدوى التقنية والاقتصادية لحالتين من أنظمة الطاقة الهجينة لحلول الطاقة المستدامة في منطقة حضرية معروفة بأشعة الشمس الوفيرة. تتضمن هذه الحالات مجموعات من الخلايا الكهروضوئية (PV) والكتلة الحيوية، مع مكونات إضافية مثل المحلل الكهربائي وخلية الوقود (FC). تشتمل الحالة 1 على PV/الكتلة الحيوية/المحلل الكهربائي، بينما تتضمن الحالة 2 PV/الكتلة الحيوية/خلية الوقود/المحلل الكهربائي/البطارية، بهدف إنتاج الكهرباء والهيدروجين. حللت هذه الورقة متطلبات الطاقة الصناعية خلال فترات غير الموسم والموسم المتوسط وموسم الذروة. النظام الأمثل للحالة 2 هو الأكثر موثوقية مع لوحة PV 23645 - kW، ومولد غاز حيوي 3800 - kW، ومحول 3821 - kW، وخلية وقود 250 - kW، ومحلل كهربائي 600 - kW، وخزان تخزين هيدروجين 600 - kg (Htank)، ونظام نسخ احتياطي 30 بطارية مع استراتيجية إرسال CC للمستهلكين خارج الموسم. بالنسبة لمستخدمي موسم الذروة، يحتوي النظام على 23789 كيلو واط من الألواح الكهروضوئية، و 3800 كيلو واط من مولدات الغاز الحيوي، و 3861 كيلو واط من المحولات، و 250 كيلو واط من FC، و 1000 كيلو واط من المحلل الكهربائي، و 1000 كجم من Htank، و 30 بنك غرفة بطارية احتياطية مع خطة إرسال LF. تشير نتائج البحث إلى أن استخدام الكهروضوئية/الكتلة الحيوية/FC/المحلل الكهربائي/البطارية هو استراتيجية أكثر جدوى واقتصادية بسبب فوائد النظام. كانت الزيادة المقدرة في LCOE ناتجة عن ارتفاع معدل الخصم وأسعار الوقود.

In recent decades, ensuring efficient thermal control of electronic components (ECs) has emerged as a critical concern. To address this, phase change materials (PCMs) are increasingly utilized to augment passive thermal management efficiency. In this work, a two-dimensional numerical study is conducted to investigate the melting of the PCM (n-eicosane) composited with metal foam (MF) and/or nanoparticles (NePCM) in a rectangular heat sink. The volume averaging technique based on the thermal equilibrium model is formulated for transient simulations. The impact of various parameters such as MF type, pores per inch (PPI), porosity, concentration of nanoparticles, and combination of NePCM and MF is investigated. Results show that the PCM/Copper foam composite with high porosity (0.95) and low PPI (10PPI) based heat sink provided a high rate of heat transfer and a more uniform melting process, which results in a drop in the electronic component temperature by 20.44 °C, and shortens the melting time by 648 s as compared to the pure PCM-based heat sink. In addition, the maximum effective thermal conductivity improvement of PCM is found to be 98% for Copper foam, with an effective latent heat reduction of 92.46%. Furthermore, outcomes reveal that using MF alone could notably enhance the melting performance. However, the addition of nanoparticles to cases involving MF, regardless of the nanoparticle volume fraction, adversely affects the melting performance of PCM. This indicates the negligible effect of nanoparticle insertion in the presence of MF. Therefore, in the context of this research, the cooling of the electronic component is primarily influenced by heat transfer through conduction than natural convection.

Abstract This numerical work examines the impact of an external magnetic field on the hydrothermal aspects of natural convection of a power-law non-Newtonian nanofluid inside a baffled U-shape enclosure. The enclosure is heated from the bottom and cooled from the baffles while the other walls are thermally insulated. Sinusoidal profile is chosen to describe the temperature distribution along the bottom wall. A comprehensive analysis is conducted to study the influence of pertinent parameters including Rayleigh number (Ra), Hartmann number (Ha), nanoparticle volume fraction (ϕ), aspect ratio of cold baffles (AR), inclination angle, and power-law index (n) on the flow and heat transfer characteristics in detail by using Galerkin finite element method. The obtained results show that the impact of n on the Nusselt number (Nu) is considerable for Ra=106 and inappreciable below this value. The influence of n and Ha on the heat transfer is significant when Ha is smaller than 30. For Ha

In this study, a phase change material (PCM) was integrated to a partition wall between the sunspace and the room of a detached house to reduce energy use. To find the optimal sunspace configuration, various phase transition temperatures, glazing types, and locations of PCM in the partition wall and the presence of active shading were evaluated in terms of energy saving and consumption in Mediterranean climate. Furthermore, economic and CO2 emission analyses were conducted to reveal potential savings for the optimal sunspace-PCM design. The optimal phase transition temperature was found as 27 ? for cooling and 21 ? for heating application, regardless of the location of the PCM in the wall. A glass with low U-value and high SHGC was beneficial in winter, whereas a glass with high U-value and low SHGC was appropriate in sum-mer. Not using an active shading device in summer increased energy consumption, but the negative effect was compensated by effective exploitation of the latent heat content of the PCM. In the yearly energy analysis, the optimal phase transition temperature was 27 C and the PCM was located at the front of the partition wall. A glazing type with high SHGC and high U-value (SG-1), or low SHGC and low U-value (TG-2) was recommended to minimize the annual energy demand. A reduction in CO2 emissions of 98 kg was achieved with the optimal configuration compared to a case without sunspace.