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Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2019;142(1):011201-011201-9. doi:10.1115/1.4044124.

The explicit model of the energy yield with respect to irradiance and cell temperature of a photovoltaic (PV) system can be apprehended using pvsyst software. Building on this data, this paper addresses performance challenges for JA Solar, JAP6 (DG) 60-235 solar PV module driving a load of Enphase, IQ6-60-x-240 grid inverter. The data modeling reflects correlation of 62% between panel temperature and output efficiency. Researchers in the past have claimed that extreme temperature exposure as one of the main impediment in decline of solar panel's life span and figured 25 °C as the ideal temperature for optimum yield. This research proposes the Internet of things (IoT)-based smart solar energy system (SES) for smart cities that automatically tune the low-powered cooling unit to lower panel's temperature to outmatch energy yield and augment solar panels life. The analog design of the cooling mechanism is set up for temperature range from −10 °C to 85 °C using hybrid op-amp proportional–integral–derivative (PID) controller and heat sink/fan with surface mount temperature sensor to maintain module temperature. The experiment analysis showed improvement of 1.7% to 2.99% in output efficiency after considering 1.8 W total power intake of the cooling circuit relative to the pvsyst v6.74 results. To access temperature data of solar panel and output current along with in-built system's current consumption, IoT accreditation is done using node MCU and Wi-Fi module.

Commentary by Dr. Valentin Fuster

Research Papers: Combustion of Waste/Fluidized Bed

J. Energy Resour. Technol. 2019;142(1):011401-011401-8. doi:10.1115/1.4044193.

Surrogate municipal solid waste (MSW) has been prepared to represent high plastic content waste with low fixed carbon in order to be utilized for feedstock for the gasification and pyrolysis. The major components are plastic (PE and PP), food and kitchen waste, and paper, whereas the minor components are textile, rubber, and biomass. Reactions were conducted in small drop tube fixed bed reactor with isothermal reaction temperature at 700, 800, and 900 °C. Steam was supplied as the gasifying agent for the main purpose of producing hydrogen-rich gas. Pyrolysis was also conducted at the same condition to observe the characteristic differences. Producer gas, including H2, CH4, and CO, of both the reactions was a function of the temperature, whereas CO2 showed a reversed trend when the reaction temperature was increased. Simple kinetic models of those gaseous formations were studied for describing the related parameters. It is challenging to determine the kinetics of the individual gas generation while most kinetic studies have focused on mass deterioration. The commonly used kinetic model of nucleation of Avrami–Erofe'ev (A2) could well predict the mechanism of the gas formation of gasification. In parallel, the pyrolysis conformed to the A3 model due to the slower rate of char and tar decomposition when the gasifying agent was absent. The activation energy of each gaseous species and the fitting of experimental data with the selected models are examined in this study.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2019;142(1):012001-012001-11. doi:10.1115/1.4044220.

A Kalina cycle is coupled to an ejector refrigeration cycle to generate power and refrigeration outputs, simultaneously. Ejector refrigeration cycle is driven by the heat which is extracted from a high-temperature/pressure stream of Kalina cycle working fluid since the energy content of this fluid stream is not directly utilized in power production in the Kalina cycle. Supplied heat to the proposed combined cycle is produced by combustion of biomethane which is obtained from anaerobic digestion of biomass, namely, food waste. System reactions to altering operation conditions (entrainment ratio, condenser pressure, evaporator pressure, and superheating degree) in terms of refrigeration production, power production, energy efficiency, exergy efficiency, and exergy of produced power and refrigeration are analyzed. The results are reported for R290, R134a, and R152a working fluids of the ejector refrigeration cycle and an extensive discussion of the results are provided. It is shown that the entrainment ratio strongly affects the thermal and exergy efficiency results. The highest thermal and exergy efficiency results are performed when R290 and R134a are used, whereas the lowest thermal and exergy efficiencies are obtained when R152a and R290 are used as the refrigerant, respectively.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2019;142(1):012201-012201-11. doi:10.1115/1.4044058.

Fossil fuel consumption provides a negative impact on the human health and environment in parallel with the decreased availability of this valuable natural resource for the future generations to use as a source of chemical energy for all applications in energy, power, and propulsion. The diesel fuel consumption in the transport sector is higher than the gasoline in most developing countries for reasons of cost and economy. Biodiesel fuel offers a good replacement for diesel fuel in compression ignition (CI) diesel engines. Earlier investigations by the authors revealed that a blend of 70% amla seed oil biodiesel and 30% eucalyptus oil (AB70EU30) is the favorable alternative renewable fuel blend that can be used as a fuel in diesel engines. With any fuel, air/fuel mixing and mixture preparation impact efficiency, emissions, and performance in CI engines. Minor adjustments in engine parameters to improve air/fuel mixing and combustion are deployable approaches to achieve good performance with alternative fuel blends in CI engines. This paper provides the role of a minor modification to engine parameters (compression ratio, injection timing, and injection pressure) on improved performance using the above mixture of binary fuel blends (AB70EU30). The results showed that the use of AB70EU30 in modified engine resulted in higher brake thermal efficiency and lower brake specific fuel consumption compared to normal diesel for improved combustion that also resulted in very low tailpipe emissions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;142(1):012202-012202-12. doi:10.1115/1.4044123.

The present work is an experimental investigation that aims at studying the effects of different fuel additives on the soot volume fraction and temperature in a well-defined vertical laminar diffusion flame configuration, and these additives include a diluent (argon) that suppresses the formation of soot and a soot promoter (acetylene) that accelerates and intensifies the soot formation. Three different measuring techniques are employed throughout the whole experimental program, namely, a high-resolution digital camera (up to 3.7 fps) for flame visualization, a bare wire Pt/Pt-13% rhodium fine thermocouple of 15 µm wire diameter for measuring the mean gas temperature inside the flame region and a laser system for measuring the in-flame soot volume fraction. The results indicated that the soot inception zone (deep dark parabolic shape) occurs at the immediate vicinity of the burner. The soot oxidation zone is characterized by high luminosity, and it begins after the fuel is largely consumed. The increased percentages of acetylene in the fuel mixture would lead to extending the length of this zone to ultimately occupy the whole visible flame length, where the luminosity becomes independent of the amount of soot. The temperature within the soot surface growth zone (orange color) continues increasing but at a lower rate that reflects the domination of diffusion combustion mode. Limited partial oxidation may be anticipated within this zone due to the relatively high temperature, which is not high enough to cause luminosity of the soot particles.

Commentary by Dr. Valentin Fuster

Research Papers: Heat Energy Generation/Storage/Transfer

J. Energy Resour. Technol. 2019;142(1):012401-012401-10. doi:10.1115/1.4044192.

Calculation process of some reservoir engineering problems involves several passes of full-order numerical reservoir simulations, and this makes it a time-consuming process. In this study, a fast method based on proper orthogonal decomposition (POD) was developed to predict flow and heat transfer of oil and water in a reservoir. The reduced order model for flow and heat transfer of oil and water in the hot water-drive reservoir was generated. Then, POD was used to extract a reduced set of POD basis functions from a series of “snapshots” obtained by a finite difference method (FDM), and these POD basis functions most efficiently represent the dynamic characteristics of the original physical system. After injection and production parameters are changed constantly, the POD basis functions combined with the reduced order model were used to predict the new physical fields. The POD-based method was approved on a two-dimensional hot water-drive reservoir model. For the example of this paper, compared with FDM, the prediction error of water saturation and temperature fields were less than 1.3% and 1.5%, respectively; what is more, it was quite fast, where the increase in calculation speed was more than 70 times.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2019;142(1):012901-012901-12. doi:10.1115/1.4043856.

Ensemble Kalman filter (EnKF) is one of the powerful optimization schemes for production data history matching in petroleum engineering. It provides promising characterization results and dependable future prediction of production performances. However, it needs high computational cost due to its recursive updating procedures. Ensemble smoother (ES), which updates all available observation data at once, has high calculation efficiency but tends to give unreliable results compared with EnKF. Particularly, it is challenging to channel reservoirs, because geological parameters of those follow a bimodal distribution. In this paper, we propose a new ES method using a channel information update scheme and discrete cosine transform (DCT). The former can assimilate channel information of ensemble models close to the reference, maintaining a bimodal distribution of parameters. DCT is also useful for figuring out main channel features by extracting out essential coefficients which represent overall channel characteristics. The proposed method is applied to two cases of 2D and 3D channel reservoirs and compared with EnKF and ES. The method not only provides reliable characterization results with clear channel connectivity but also preserves a bimodal distribution of parameters. In addition, it gives dependable estimations of future production performances by reducing uncertainties in the prior models.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;142(1):012902-012902-7. doi:10.1115/1.4044122.

During the drilling of shale formations, drilling fluids can intrude into the wellbore, raise the pore pressure, and lead to wellbore instability. Based on the thermodynamic theory, a new model was established to calculate pore pressure. The model considers the effects of solute diffusion and solution convection and conducts sensitivity analyses. The results show that the drilling fluid activity significantly affects the pore pressure distribution. The pore pressure under high drilling fluid activity will increase rapidly in the early stage. Low drilling fluid activity can effectively suppress the growth of pore pressure. And a low effective diffusion coefficient of solute and a high membrane efficiency also help to reduce pore pressure. Therefore, reducing drilling fluid activity should be conducted in priority in drilling fluid design. Lowering its solute effective diffusion coefficient and increasing its viscosity can also be considered as auxiliary methods.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;142(1):012903-012903-9. doi:10.1115/1.4044226.

Chelating agent solutions have been proposed as effective fluids for enhancing oil production. Different recovery mechanisms are reported for increasing the oil recovery during chelating agent flooding. The aims of this work are to identify the possible recovery mechanisms during chelating agent flooding in carbonate reservoirs and to investigate the in situ CO2 generation as a potential recovery mechanism during the injection of chelating agent solutions into carbonate reservoirs. The contribution of CO2 on enhancing the oil recovery was determined using experimental measurements and analytical calculations. Several measurements were conducted to study the contribution of each mechanism on enhancing the oil recovery. Coreflooding tests, zeta potential measurements, CO2 generation, and interfacial tension (IFT) experiments were carried out. Also, analytical models were utilized to determine the impact of the injected chemicals on reducing the capillary pressure and improving the flow conditions. In flooding tests, two chemicals (EDTA and GLDA) were injected in a sequential mode and the chemical concentration was increased gradually. In addition, a comparative study was performed to evaluate the effectiveness of EDTA and GLDA solutions to enhance oil recovery. Several parameters were investigated in this paper including incremental oil recovery, in situ CO2 generation, hydrocarbon swelling, IFT, wettability alteration, permeability enhancement, productivity index, and chemical cost. The obtained results show that GLDA chelating agent has better performance than EDTA solutions for enhancing the oil recovery when the same concentrations are used. Also, the in situ generation of CO2 shows a significant impact on improving the oil recovery from carbonate reservoirs during chelating agent flooding. In the literature, the reported recovery mechanisms of using chelating agents are the IFT reduction, wettability alteration, and rock dissolution. Based on this work, injecting chelating agent solutions at low pH can lead to involve additional recovery mechanisms due to the CO2 generation, the additional mechanisms are hydrocarbon swelling, viscosity and density reduction, and oil vaporization.

Commentary by Dr. Valentin Fuster

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