• Energy Research

Computational fluid dynamics of variable nozzle ejector has been studied to determine the optimum nozzle exit position for reliable ejector cooling cycle operations. The flow rates of primary and secondary stream were varied to obtain the optimum entrainment ratio under different ranges of operating conditions.The refrigerant R134a was chosen based on the merit of its environmental and performance characteristics, the refrigerant was chosen because currently is used widely in air conditioning system. It was found that the computational fluid dynamics showed that the optimum positioning of nozzle exit position, which was based on the parameters such as pressure inlet variation the temperature inlet. The results obtained after the optimization of the results showed that the optimum nozzle exit position was found at 3 mm from the mixing chamber inlet when the operating conditions pressure inlet, secondary pressure inlet, primary temperature inlet and outlet pressure were at (18bar,6bar,373K,and5.6bar) respectively. Similarly, the range of entrainment ratio was varied between 0.24−1.283 at a constant area ratio, and at varied operating conditions. Keywords: Ejector, Variable nozzle, Cooling system, Entrainment ratio, Turbulence models

The temperature rise in photovoltaic cells causing drop in their open-circuit voltage is a serious issue to be dealt with. A wide range of cooling techniques have been proposed by researchers due to its positive results on electrical efficiency during operation. One of the prominent techniques in the field is using a hybrid photovoltaic thermal (PV/T) design which in turns utilizes a working fluid to extract the heat from the collector. Various PV/T designs have been proposed, most prominently nanofluid and nanofluid with nano-PCM-based PV/T. This paper aims to evaluate the two techniques of cooling a grid-connected PV system and examines the systems electrical and combined efficiency, in addition to performing exergy analysis. The two systems are experimentally tested for outdoors conditions in Bangi, Malaysia. The results show the two systems achieving highest electrical exergies of 73 and 74.52 for nanofluid and nanofluid with nano-PCM, respectively. Both systems achieved higher exergies than water-cooled and conventional GCPV.

Abstract Quantum dot-sensitized solar cells (QDSSCs) are renowned energy devices known for their distinct qualities, including (i) the ability to harvest sunlight that generates multiple electron–hole pairs, (ii) simplicity in fabrication, and (iii) low cost. The power conversion efficiency (η) rates of many QDSSCs are lower than those of dye-sensitized solar cells, reaching a maximum of 12% as a result of narrow absorption ranges and of the charge recombination occurring at the QD– and TiO2–electrolyte interfaces. New types of sensitizers are necessary to be developed to further increase the η of QDSSCs. Semiconductor QDs are the most applicable material for photosensitization because of their high absorption and the obtained emission spectra that can be manipulated by varying dot sizes. This paper presents an overview of recent studies on QDSSC photosensitization and provides suggestions to improve QDSSCs by explicitly comparing different sensitizers. Particular focus is directed on the behavior of several important types of semiconductor nanomaterials (sensitizers such as CdS, Ag2S, CdSe, CdTe, CdHgTe, InAs, and PbS) and other nanomaterials that are TiO2, ZnO, and carbon-based species. These materials are developed to enhance the electron transfer efficiency of QDSSCs. Understanding the mechanism of various photosensitization processes can provide design guidelines for future successful applications.

Malaysia's renewable energy (RE) feed-in tariff (FIT) (REFIT) is a new incentive for energy producers, the effects of which are unclear for investors. This study utilizes archival research method on existing Malaysian policies, plans, strategies, and action plans to present a comprehensive view of the solar aspect of the Malaysian FIT policy. This paper discusses Malaysia's REFIT scheme and the benefits of implementing the FIT policy in the solar sector. The Malaysian solar energy sector can preserve the country's oil and gas reserves, thus reducing carbon production and hindering environmental degradation. This paper examines the advantages and disadvantages of the Malaysian FIT model, and it concludes with an analysis of this design, with a focus on its implications for investors and for society. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 600–606, 2015

Abstract This paper presents design considerations to be taken in designing of a low temperature differential double-acting Stirling engine for solar application. The target power source will be a thermosiphon solar water heater with integrated storage system, which will supply a constant source temperature of 70 °C. Hence, the system design is based on a temperature difference of 50 °C, assuming that the sink is kept at 20 °C. During the preliminary design stage, the critical parameters of the engine design are determined according to the Schmidt analysis, while the third order analysis was used during the design optimisation stage in order to establish a complete analytical model for the engine. The heat exchangers are designed to be of high effectiveness and low pressure-drop, and are made from a 0.015 m tube, while the porosity of the steel wool of 0.722 is used for the regenerator matrix. Upon optimisation, the optimal engine speed is 120 rpm with the swept volume of 2.3 l, and thus the critical engine parameters are found to be the bore diameter of 0.20 m. In addition, the volumes of heater, cooler and regenerator are 1.3 l, 1.3 l and 2.0 l volumes, respectively.

Current study employs mixture of chlorophyll-anthocyanin dye extracted from leaves of Cordyline fruticosa as new sensitizers for dye-sensitized solar cell (DSSCs), as well as betalains dye obtained from fruit of Hylocereus polyrhizus. Among ten pigments solvents, the ethanol and methanol extracts revealed higher absorption spectra of pigments extracted from C. fruticosa and H. polyrhizus respectively. A major effect of temperature increase was studied to increase the extraction yield. The results indicated that extraction temperature between 70 and 80°C exhibited a high dye concentration of each plant than other temperatures. The optimal temperature was around 80°C and there was a sharp decrease of dye concentration at temperatures higher than this temperature. According to experimental results, the conversion efficiency of DSSC fabricated by mixture of chlorophyll and anthocyanin dyes from C. fruticosa leaves is 0.5% with short-circuit current (Isc) of 1.3mA/cm-2, open-circuit voltage (Voc) of 0.62V and fill factor (FF) of 60.16%. The higher photoelectric conversion efficiency of the DSSC prepared from the extract of H. polyrhizus was 0.16%, with Voc of 0.5V, Isc of 0.4mA/cm-2 and FF of 79.16%. The DSSC based betalain dye extracted from fruit of H. polyrhizus shows higher maximum IPCE of 44% than that of the DSSCs sensitized with mixed chlorophyll-anthocyanin dye from C. fruticosa (42%).

Abstract Renewable alternative energy sources are getting more attention due to the depleting nature of non-renewable fossil fuels. Increasing global warming, caused by the combustion of fossil fuels, triggered the intense research in finding out better energy options with low emission. Among the potential energy options, hydrogen is a clean fuel candidate as it simply produces water as byproducts when burning. Hydrogen can be generated from different renewable sources and Asia is one of the continents which is rich in renewable energy resources. The resources, safety parameters, public acceptability, and proper government incentives are the major factors affecting the implementation of hydrogen as an economical energy source in Asian countries. The present review deals with the necessity of employing hydrogen as an alternative fuel, its production paths, storage issues, transportation and the available sources. Special emphasis has been given to the discussion of renewable hydrogen economy in some Asian countries like, Japan, Korea, China, India and Malaysia. The challenges in the execution of hydrogen as an economical fuel in Asia are also highlighted.

Abstract A conceptual design and performance of a dual-purpose solar continuous adsorption system for domestic refrigeration and water heating is described. Malaysian activated carbon and methanol are used as the adsorbent–adsorbate pair. The heat rejected by the adsorber beds and condensers during the cooling process of the refrigeration part is recovered and used to heat water for the purpose of domestic consumption. In a continuous 24-h cycle, 16.9 MJ/day of heat can be recovered for heating of water in the storage tanks. In the single-purpose intermittent solar adsorption system, this heat is wasted. The total energy input to the dual-purpose system during a 24-h operation is 61.2 MJ/day and the total energy output is 50 MJ/day. The latter is made up of 44.7 MJ/day for water heating and 5.3 MJ/day for ice making. The amount of ice that can be produced is 12 kg/day. Using typical value for the efficiency of evacuated tube collector of water heating system of 65%, the following coefficient of performances (COP's) are obtained: 44% for adsorption refrigeration cycle, 73% for dual-purpose solar water heater, 9.1% for dual-purpose solar adsorption refrigeration and 82.1% for dual-purpose of both solar water heater and refrigerator.

The rising demand for renewable energy sources has fueled interest in converting biomass and organic waste into sustainable bioenergy. This study employs a bibliometric analysis (2013-2023) of publications to assess trends, advancements, and future prospects in this field. The analysis explores seven key research indicators, including publication trends, leading contributors, keyword analysis, and highly cited papers. We begin with a comprehensive overview of biomass as a renewable energy source and various waste-to-energy technologies. Employing Scopus and Web of Science databases alongside Biblioshiny and VOSviewer for analysis, the study investigates publication patterns, citation networks, and keyword usage. This systematic approach unveils significant trends in research focus and identifies prominent research actors (countries and institutions). Our findings reveal a significant increase in yearly publications, reflecting the growing global focus on biomass and organic waste conversion. Leading contributors include China, the United States, India, and Germany. Analysis of keywords identifies commonly used terms like "biofuels," "pyrolysis," and "lignocellulosic biomass." The study concludes by proposing future research directions, emphasizing advanced conversion technologies, integration of renewable energy sources, and innovative modelling techniques.