Journal of Energy Engineering

The use of renewable alternative fuels in diesel engines has grown recently. In order to study the effects of different swirl ratios (SRs) on the performance of a diesel engine fueled with n-butanol–diesel blends, the combustion process of a 186FA diesel engine with pure diesel, 20% n-butanol and 80% diesel fuel by volume (BU20) and 30% n-butanol and 70% diesel fuel by volume (B30) fuel at five swirl ratios was simulated using AVL Fire software. The simulation model was validated by comparing the calculation results and experimental results with the in-cylinder pressure, heat release rate, and emissions of soot and nitrogen oxides (${\mathrm{NO}}_x$). This paper analyzes the effects of the different swirl ratios on combustion and emissions characteristics and on the concentration field in the cylinder. The results show that soot generation for the three kinds of fuels gradually decreases with the increase of the swirl ratio (SR). For BU20, the soot mass fraction of SR0.2 was $219\times {10}^{-6}$, and the largest decline in soot generation was 82%. NO emissions first increased and then decreased with the increase of the swirl ratio for BU20 and BU30. For BU20, the NO formation for SR0.2 was $620\times {10}^{-6}$, and when the swirl ratio was 1.8, NO formation reached its highest level of $905\times {10}^{-6}$, increasing by 46%. As a compromise between enhancing power output and reducing emissions, a swirl ratio of 1 was optimal for pure diesel and a swirl ratio of 3.4 was optimal for BU20 and BU30.

A major concern today is the environmental pollution by the emission of gases from vehicles. Biodiesel is a cleaner alternative to petroleum diesel in terms of carbon monoxide (CO), hydrocarbon (HC), and smoke emission. However, biodiesel results in higher nitrogen oxide (NOx) with increasing performance, poor cold weather properties, and relatively low brake-thermal efficiency (BTE), which sets a major disadvantage for its worldwide commercialization. The impact of biodiesel fatty acid contents was studied through various blends of biodiesel so as to discover the optimum fatty acid content for reduced NOx emission and sufficient brake-thermal efficiency. Glycerol tert-butyl ether (GTBE) is a transesterification by-product and a fuel additive that has the potential to serve these issues. Instead of increased BTE maximum, a 10.5% reduction in NOx yield was observed with modified injection pressure and 2.5% GTBE concentration. Modified injection pressure of 240 bar (24 MPa) and 5% GTBE resulted in a maximum of 20% cut in CO emission. All tested biodiesel fuels displayed a decrease in NOx emission with improved BTE at 2.5% and 5% GTBE addition. Injection pressure 220 bar and 240 bar in combination with GTBE enhanced BTE of fuels significantly.

The parabolic trough collector (PTC) is one of the most deployed and cost-effective solar concentrating systems available. The PTC under study is modeled after the LS-2 collector with different geometrically modified absorber tubes. The proposed model is validated using the Sandia national laboratory, AZTRAK, platform results. The absorber tube is modeled for five different geometry configurations: plain tube (smooth tube), longitudinal finned tube, a tube with a porous insert, a tube with a twisted tape insert, and a wavy (converging-diverging) tube. An analysis was conducted to observe the effects of these modifications on the thermal efficiency, Nusselt number, heat transfer coefficient, receiver temperature, and pressure losses. The converging-diverging absorber tube provides the maximum thermal enhancement of 1.16% whereas the absorber tube with porous insert yielded a mean enhancement of 0.89%. The results prove that modifying the inner geometry of the absorber tube leads to increased heat transfer coefficient and a reduction in the circumferential temperature of the receiver. The thermal and exergetic enhancement factors along with the exergetic efficiency are among other parameters investigated.

This study aims to evaluate the thermodynamic performance of an enhanced integrated collector-storage solar (ICSS) or passive photovoltaic-thermal (PVT) system with two reflectors for cooling applications. The solar cooling system includes the single-effect absorption cycle. First, the modeling of the ICSS-PV and the overall cooling cycle is validated. Then, an hourly simulation of a 10-kW absorption cooling cycle is carried out. In addition to supplying a fraction of the cooling load of the proposed system, it can also generate electrical energy. Results indicate that the coefficient of performance (COP) of the system is 0.62. Influence of tank water mass, generator temperature, and evaporator temperature on the hourly performance of cycle were investigated. Accordingly, with increasing tank water mass, the electricity generated by ICSS-PV and the solar coefficient of performance increase whereas the hourly solar fraction and solar exergetic efficiency decrease. With increasing generator temperature, the solar coefficient of performance and solar exergetic efficiency decrease but the solar fraction increases; with increasing evaporator temperature, the COP is increased. Also, Influence of the condenser and absorber temperature on the COP and exergetic efficiency was investigated.

Big data has emerged as an attractive concept in various industry domains. For power engineering, enormous amounts of data from different devices, different geographical locations of the power grid, and different time scales are collected, which creates the research opportunity for power big data. This paper conducted a comprehensive up-to-date literature review and a preliminary discussion of this emerging research topic. The definition, structure, and characteristics of the power big data were introduced. The technical architecture for power big data analysis was elaborated. Typical state-of-the-art applications of power big data were reviewed and discussed. This paper provided a comprehensive review of this promising topic, and a deep insight to help utility companies transform data into information, information into knowledge, and knowledge into wisdom.

This paper presents a comprehensive status investigation of a designed 5.1-kW residential-scale grid-tie photovoltaic energy system (PVES) equipped with an inverter-based status monitoring scheme. Status variations for 19 parameters are monitored every 10 min during the daylight. The data of typical sunny, average, and heavily cloudy days are analyzed to characterize the system status and behavior under various atmospheric conditions. The performance indexes, including different energy yield factors and system losses, are computed following international standards. Unlike other similar studies in literature, the impact of the installed PVES on the low-voltage electrical network is initially investigated at the inverter level, and the compatibility with the emerging requirements and codes to integrate such systems within the electric grid is examined. The average monthly capacity factor is found to be 15.55%. A comparison with other photovoltaic systems worldwide reflects initial good matching.