• Energy Research

The political upheaval and the civil war in Libya had a painful toll on the operational reliability of the electric energy supply system. With frequent power cuts and crumbling infrastructure, mainly due to the damage inflicted upon several power plants and grid assets as well as the lack of maintenance, many Libyans are left without electricity for several hours a day. As the country has a staggeringly immense potential of solar energy, it is inevitable to exploit such potential, to avert system-wide blackouts. This paper investigates the use of small-scale PV systems in local communities as non-wires alternative (NWA), offering excess energy exchange within local/neighboring microgrids (MGs) for reliable electric power supply. Different combinations of PV/storage/diesel distributed generations (DGs), with grid-interface options, were applied on a case study of a typical dwelling in the Eastern Libyan city of Benghazi. Technical and financial feasibility assessments were carried out to contrast between various supply combinations. Sensitivity analysis of the PV-grid system was also conducted using Net Present Value (NPV) and the payback time indicators to determine the impacts of Feed-in Tariff (FiT) rates, financial incentives, electricity tariff, and inflation rate on the economic viability of the PV grid system. Results show that the PV-grid system has a promising potential under reasonable set of varying system parameters. On top of its social and environmental-friendly advantages, the PV-battery system is found to be more economical when adopted as a standalone NWA solution as compared to the diesel generator option, even at the lowest diesel price. The PV-grid system does not only provide a short-term remedy to the rolling blackouts in Libya but also enhances system operational reliability by providing a NWA to rundown or shattered grid infrastructure, thus bolstering energy provision in residential neighborhoods.

Previous works revealed that cross-corrugated absorber plate design and jet impingement on a flat absorber plate resulted in a significant increase in the performance of a solar air heater (SAH). Involving these two designs into one continuous design to improve the SAH performance remains absent in the literature. This study aimed to evaluate the achieved enhancement on performance parameters of a SAH with jet impingement on a corrugated absorber plate. An energy balance model was developed to compare the performance parameters of the proposed SAH with the other two SAHs. At a clear sky day and a mass flow rate of 0.04 kg/s, the hourly results revealed that the max fluid outlet temperatures for the proposed SAH, jet-to-flat plate SAH, and cross-corrugated plate SAH are 321, 317, and 313 K, respectively; the max absorber plate temperatures are 323.5, 326.5, and 328 K, respectively; the maximum temperature differences between the absorber plate and fluid outlet are ~3, 9, and 15 K, respectively; the max efficiencies are 65.7, 64.8, and 60%, respectively. Statistical t-test results confirmed significant differences between the mean efficiency of the proposed SAH and SAH with jet-to-flat plate. Hence, the proposed design is considered superior in improving the performance parameters of SAH compared to other designs.

This study investigates the technical and cost-effective performance of options renewable energy sources to develop a green off-grid telecommunication tower to replace diesel generators in Malaysia. For this purpose, the solar, wind, pico-hydro energy, along with diesel generators, were examined to compare. In addition, the modeling of hybrid powering systems was conducted using hybrid optimization model for energy (HOMER) simulation based on techno-economic analysis to determine the optimal economically feasible system. The optimization findings showed that the hybrid high-efficiency fixed photovoltaic (PV) system with battery followed by 2 kW pico-hydropower and battery are the optimal configurations for powering off-grid telecommunication towers in Malaysia with the lowest net present cost (NPC) and cost of energy (COE). These costs of NPC and COE are more down than diesel generator costs with battery by 17.45%, 16.45%, 15.9%, and 15.5%, respectively. Furthermore, the economic evaluation of the high-efficiency solar fixed PV panels system annual cash flow compared to the diesel generator with the battery system indicated a ten-year payback period.

Abstract Solar technology is a promising renewable option and essential towards a sustainable energy future. PV power systems represent a major part of solar technology. The efficiency of a PV module is limited by many factors such as ohmic losses between solar cells, solar radiation, high module temperature, dust and packing factor. A combined PV/T concept was proposed to reduce the thermal stress of PV module by recovering the heat of high PV module temperature and use it for thermal applications. After decades of continuous research and development (R&D) aspects on PV/T, many researchers reported lower PV electrical efficiency, lower thermal efficiency and lower PV/T efficiency for it than the two separate systems. That is why, the product reliability of the PV/T system does not succeed in penetrating the market due to technical, cost and size barriers such as materials, design, manufacturing techniques, initial cost, installation cost and the bulk size of the system. Since the PVT concept failed to increase the electrical and thermal efficiencies concurrently, it would be more appropriate if the R&D community refocuses its efforts again on the heat dissipation option instead of the costly heat recovery option to regulate the high PV module temperature. The aim of this review is to provide an insight into the role of passive and active techniques in the thermal regulation of PV module temperature. The study will shed light on the temperature reduction range that is possible by the available passive and active heat dissipation approaches. Also, the effectiveness of passive approaches in lowering the temperature of the PV module when compared to active approaches will be highlighted as well. In addition to this overall study, this review will include a discussion of the effectiveness of passive and active approaches in the context of PVT collector, thus supporting the argument towards the potential of passive approaches when compared to active approaches. The outcomes of this study are detailed in the lessons-learned section and future research priorities are highlighted in the conclusion section.

Abstract The high temperature of PV modules is one of the major factors that affect the PV system performance. The PV/T collector is proposed mainly to recover the heat of the high PV module temperature using conventional working fluids (water/air). Nanofluids (NFs) would help enhance the heat transfer/heat removal. The effect of NFs on enhancing the electrical/thermal efficiency of the PV/T collector besides the fluid's outlet temperature were investigate theoretically and experimentally. Fluent simulation tool together with energy balance equations were used. Three rounds of analysis were performed. Firstly, the optimal design of “sheet and tube” thermal absorber was determined using water as the base fluid. Secondly, the PV/T performance aspects using three types of NFs (CuO, SiO2, and ZnO) and water, were compared. Thirdly, the life cycle cost analysis/profit gain were applied to examine the feasibility of the grid connected PV/T-NF. The results showed that the optimal design of the PV/T thermal absorber requires 11 rectangular tubes per module, and the optimal rectangular tube dimensions are 24 mm (width) and 15 mm (depth). The results also revealed that the NF-SiO2 showed outstanding enhancement compared to other types of NFs and water. In addition, the results revealed that using NF- SiO2 in the PV/T collector reduced the PV module temperature from 65 °C to 45 °C and increased the outlet temperature from 35 °C to 44 °C, leading to an electrical and thermal efficiency enhancement of 12.70% and 5.76% respectively at a solar irradiance of 1000 W/m2. Payback analysis and profit gain of grid connected PV/T- NF (SiO2) system, grid connected PV/T- water system, and (grid connected PV + solar thermal) system were found (8 yrs, 10218.137 $; 11 yrs, 5518.518 $; 15 yrs, 3816.873 $), respectively. This indicated that the grid connected PV/T-NF (SiO2) system is economically feasible compared to the other systems despite the additional initial cost of the expensive NFs and the customized heat exchanger.

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.