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Research Papers

J. Energy Resour. Technol. 2014;136(1):011202-011202-13. doi:10.1115/1.4026267.

In this study, a thermodynamic model of a hybrid electric vehicle battery thermal management system (TMS) is developed and the efficiency of the system is determined based on different parameters and operating conditions. Subsequently, a TMS test bench is used with a production vehicle (Chevrolet Volt) that is fully instrumented in order to develop a vehicle level demonstration of the study. The experimental data are acquired under various conditions using an IPETRONIK data acquisition system, along with other reported data in the literature, to validate the numerical model results. Based on the analyses, the condenser and evaporator pressure drop, compressor work and compression ratio, evaporator heat load and efficiency of the system are determined both numerically and experimentally. The predicted results are determined to be within 6% of the conducted experimental results and within 15% of the reported results in the literature.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2014;136(1):011203-011203-10. doi:10.1115/1.4026201.

During wind farm planning, the farm layout or turbine arrangement is generally optimized to minimize the wake losses, and thereby maximize the energy production. However, the scope of layout design itself depends on the specified farm land-shape, where the latter is conventionally not considered a part of the wind farm decision-making process. Instead, a presumed land-shape is generally used during the layout design process, likely leading to sub-optimal wind farm planning. In this paper, we develop a novel framework to explore how the farm land-shape influences the output potential of a site, under a given wind resource variation. Farm land-shapes are defined in terms of their aspect ratio and directional orientation, assuming a rectangular configuration. Simultaneous optimizations of the turbine selection and placement are performed to maximize the energy production capacity, for a set of sample land-shapes with fixed land area. The maximum farm capacity factor or farm output potential is then represented as a function of the land aspect ratio and land orientation, using quadratic and Kriging response surfaces. This framework is applied to design a 25 MW wind farm at a North Dakota site that experiences multiple dominant wind directions. An appreciable 5% difference in capacity factor is observed between the best and the worst sample farm land-shapes at this wind site. It is observed that among the 50 sample land-shapes, higher energy production is accomplished by the farm lands that have aspect ratios significantly greater than one, and are oriented lengthwise roughly along the dominant wind direction axis. Subsequent optimization of the land-shape using the Kriging response surface further corroborates this observation.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2014;136(1):012005-012005-7. doi:10.1115/1.4026312.

Micro hydropower station is one of the clean choices for offgrid points with available hydropotential. The challenging in this type of energy production is the high capital cost of the installed capacity that is worse for low-head micro hydropower stations. Turbine price is the main problem for this type of energy production. In this research, a simple machine has been introduced instead of conventional propeller turbines. The key is using an axial pump as a propeller turbine. In the present research, a propeller pump was simulated as a turbine by numerical methods. Computational fluid dynamics (CFD) was adopted in the direct and reverse modes performance prediction of a single propeller pump. To give a more accurate CFD result, all domains within the machine control volume were modeled and hexahedral structured mesh was generated during CFD simulation. Complete performance curves of its pump and turbine modes were acquired. For verification of the numerical results, the machine has been tested in an established test ring. The results showed that a propeller pump could be easily run as a low-head turbine. In the next, the goal was to optimize the geometry of the blades of axial turbine runner which leads to maximum hydraulic efficiency by changing the design parameters of camber line in five sections of a blade. The efficiency of the initial geometry was improved by various objective functions and optimized geometry was obtained by genetic algorithm and artificial neural network to find the best efficiency of the turbine. The results showed that the efficiency is improved by more than 14%. Indeed the geometry has better performance in cavitation.

Commentary by Dr. Valentin Fuster

Research Papers: Air Emissions From Fossil Fuel Combustion

J. Energy Resour. Technol. 2013;136(1):011101-011101-7. doi:10.1115/1.4024916.

Precise knowledge on temperature and its fluctuation in combustion systems are among the important energy issues in almost all industrial sectors, energy conversion and power fields. In this study, a spectroscopic technique is used to measure the time-resolved temperature distribution by a comparatively simple optical system that involved two band-pass filters (BPF), and a charge-coupled device with image intensifier (ICCD) video camera. The system was assembled and applied to an acetylene-oxygen premixed flame that are widely used for welding purposes because of very high temperature in such flames. The temperature distribution and its fluctuation directly impact the quality of soldering. The results provided direct visualization of temperature and its fluctuation in the flames that are conjectured to emanate from thermal and hydrodynamic phenomena from chemical reactions in the flame and interaction with surrounding air.

Commentary by Dr. Valentin Fuster

Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2014;136(1):011201-011201-5. doi:10.1115/1.4026280.

Performance prediction of thermoelectric generators (TEG) is an important work in thermoelectrics and a physical model is quite necessary. Now basic thermoelectric phenomena have been expounded explicitly, modeling a TEG is an accessible work. However, the Thomson heat (which is a second-order effect) is usually neglected in device-level TEG analyses. And the dealing with the output power expression without Thomson heat is improper in some studies. Based on a thermoelectric model which considers basic thermoelectric effects, as well as the thermal resistances between the thermocouple and the heat source, heat sink, reasonable expressions of Thomson coefficient and Seebeck coefficient are proposed. The output power expression without Thomson heat is analyzed and redressed. With and without Thomson heat, the output power and energy efficiency are calculated at different thermal conditions. Some new results distinct from the past ones are presented. At last, in order to testify the physical model, a BiTe-based thermoelectric module is tested and an ANSYS model is built.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Conversion/Systems

J. Energy Resour. Technol. 2013;136(1):011601-011601-5. doi:10.1115/1.4025020.

Distributed combustion has been shown to provide significantly improved performance with near zero emissions for stationary gas turbine applications. Characteristics of distributed combustion include uniform thermal field in the entire combustion chamber (improved pattern factor), ultra-low emissions of NOx and CO, low noise, enhanced stability, and higher efficiency. Distributed combustion with swirl have been investigated to determine the beneficial aspects of such flows on clean and efficient combustion under simulated gas turbine combustion conditions with ultra-low NOx emissions. Results are presented here on the impact of employing dual injection of air and fuel in contrast to single injection. Dual and multi-injection is of great importance for combustor design scale up as to maintain flow similarities. Results showed that careful implementation of dual injection can result in emissions as low as single air/fuel injection method. With adequate fuel injection strategy, further reduction in emissions has been demonstrated. Results obtained on pollutants emission with dual injection and different fuel injection strategies at various equivalence ratios showed ultra-low emission (<5 PPM NO and <15 PPM CO) and high performance. OH* chemiluminescence revealed relative position of the flame within the combustor under various conditions for further improvements in distributed combustion conditions and to further reduce NOx emission.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):011602-011602-11. doi:10.1115/1.4024858.

This paper presents the results of the application of an advanced thermodynamic model developed by the authors for the simulation of Organic Rankine Cycles (ORCs). The model allows ORC simulation both for steady and transient analysis. The expander, selected to be a scroll expander, is modeled in detail by decomposing the behavior of the fluid stream into several steps. The energy source is coupled with the system through a plate heat exchanger (PHE), which is modeled using an iterative sub-heat exchanger modeling approach. The considered ORC system uses solar thermal energy for ultralow grade thermal energy recovery. The simulation model is used to investigate the influence of ORC characteristic parameters related to the working medium, hot reservoir and component efficiencies for the purpose of optimizing the ORC system efficiency and power output. Moreover, dynamic response of the ORC is also evaluated for two scenarios, i.e. (i) supplying electricity for a typical residential user and (ii) being driven by a hot reservoir. Finally, the simulation model is used to evaluate ORC capability to meet electric, thermal and cooling loads of a single residential building, for typical temperatures of the hot water exiting from a solar collector.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2013;136(1):012001-012001-6. doi:10.1115/1.4024918.

Potable water is becoming scarce in many areas of the planet as the human population pushes past 7 × 109. There is an increasing need for electric power since electricity is essential for modern development and progress. Traditionally, condenser cooling systems for power plants use seawater or freshwater in conjunction with cooling tower technology. Seawater is used in plants near the sea or ocean, and seawater condenser cooling systems are typically open systems. More recently, air-cooling has been implemented and undergoing evaluations. Predictably, during the summer season in hot, semidesert and desert areas, air-cooling would not prove very efficient. Ironically, these areas would require the most fresh, potable water if the population and/or population density is large. The need for additional power generation units to satisfy consumer demands, and hence more cooling capacities, creates a problem for utilities. The current work researches the feasibility of using seawater cooling systems in the United States of America that are far from the sea. Five such locations have been identified as possibilities. Such a system has proven successful in South Florida. This system utilizes a series of cooling canals, used to dissipate the condenser heat to the surroundings. Relevant statistics of such a canal include water flow rate, total capacity, and MW of generators (both fossil-fueled and nuclear steam generators) the system is designed to cool. Additional statistics include the possible need to top-up (both amount and frequency of water required to maintain canal surface levels) or whether local natural rain water is adequate to replace evaporation and loss. Logistical information includes the estimated size of land required to accommodate the cooling canals. In estimating the canal system size and concomitantly the land required in other parts of the country, there is the tacit assumption that the thermal capacity of the surrounding land is about the same, and that the thermal conductivities of the different types of soil, and the heat transfer coefficients between the seawater and the canal are similar.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012002-012002-6. doi:10.1115/1.4024768.

Smart glass is such that its properties may be changed by application of a potential across it. The change in properties may be engineered to alter the amount of heat energy that can penetrate the glass which provides heating and cooling design options. Therein lies its potential in energy savings. Smart glass may be classified into three types: electrochromic, suspended particle, and polymer dispersed liquid crystal (PDLC). Each of these types has their own mechanisms, advantages, and disadvantages. Electrochromic smart glass is the most popular, currently it utilizes an electrochromic film with an ion storage layer and ion conductor placed between two transparent plates. The electrochromic film is usually made of tungsten oxide, owing to the electrochromic nature of transition metals. An electric potential initiates a redox reaction of the electrochromic film transitioning the color and the transparency of the smart glass. Suspended particle smart glass has needle shaped particles suspended within an organic gel placed between two electrodes. In its off state, the particles are randomly dispersed and have a low light transmittance. Once a voltage is applied, the needle particles will orient themselves to allow for light to pass through. PDLC smart glass works similarly to the suspended particle variety. However, in PDLC smart glass, the central layer is a liquid crystal placed within a polymer matrix between electrodes. Similar in behavior to the suspended particles, in the off position the liquid crystals are randomly dispersed and have low transmittance. With the application of a voltage, the liquid crystals orient themselves, thereby allowing for the transmittance of light. These different smart glasses have many different applications, but with one hindrance. The requirement of a voltage source is a major disadvantage which greatly complicates the overall installation and manufacturing processes. However, the integration of photovoltaic (PV) devices into smart glass technology has provided one solution. Photovoltaic films attached in the smart glass will provide the necessary voltage source. The photovoltaic film may even be designed to produce more voltage than needed. The use a photovoltaic smart glass system provides significant cost savings in regards to heating, cooling, lighting, and overall energy bills. Smart glass represents a technology with a great deal of potential to reduce energy demand. Action steps have been identified to propagate the popular use of smart glass.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012003-012003-10. doi:10.1115/1.4024855.

Dual fuel pilot-ignited natural gas engines are identified as an efficient and viable alternative to conventional diesel engines. This paper examines cyclic combustion fluctuations in conventional dual fuel and in dual fuel partially premixed combustion (PPC). Conventional dual fueling with 95% (energy basis) natural gas (NG) substitution reduces NOx emissions by almost 90% relative to neat diesel operation; however, this is accompanied by 98% increase in HC emissions, 10 percentage points reduction in fuel conversion efficiency (FCE) and 12 percentage points increase in COVimep. Dual fuel PPC is achieved by appropriately timed injection of a small amount of diesel fuel (2–3% on an energy basis) to ignite a premixed natural gas–air mixture to attain very low NOx emissions (less than 0.2 g/kWh). Cyclic variations in both combustion modes were analyzed by observing the cyclic fluctuations in start of combustion (SOC), peak cylinder pressures (Pmax), combustion phasing (Ca50), and the separation between the diesel injection event and Ca50 (termed “relative combustion phasing”). For conventional dual fueling, as NG substitution increases, Pmax decreases, SOC and Ca50 are delayed, and cyclic variations increase. For dual fuel PPC, as diesel injection timing is advanced from 20 deg to 60 deg BTDC, Pmax is observed to increase and reach a maximum at 40 deg BTDC and then decrease with further pilot injection advance to 60 deg BTDC, the Ca50 is progressively phased closer to TDC with injection advance from 20 deg to 40 deg BTDC, and is then retarded away from TDC with further injection advance to 60 deg BTDC. For both combustion modes, cyclic variations were characterized by alternating slow and fast burn cycles, especially at high NG substitutions and advanced injection timings. Finally, heat release return maps were analyzed to demonstrate thermal management strategies as an effective tool to mitigate cyclic combustion variations, especially in dual fuel PPC.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012004-012004-6. doi:10.1115/1.4024718.

Synthetic data were analyzed to determine the most cost-effective tomographic monitoring system for a geologic carbon sequestration injection site. Double-difference tomographic inversion was performed on 125 synthetic data sets: five stages of CO2 plume growth, five seismic event regions, and five geophone arrays. Each resulting velocity model was compared quantitatively to its respective synthetic velocity model to determine accuracy. The results were examined to determine a relationship between cost and accuracy in monitoring, verification, and accounting applications using double-difference-tomography. The geophone arrays with widely varying geophone locations, both laterally and vertically, performed best.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2013;136(1):012201-012201-8. doi:10.1115/1.4024856.

A fluidized bed reactor has been developed which uses a two-step thermochemical water splitting process with a peak hydrogen production rate of 47 Ncm3/min.gFe at an oxidation temperature of 850 °C. Of particular interest, is that a mixture of iron and zirconia powder is fluidized during the oxidation reaction using a steam mass flux of 58 g/min-cm2. The zirconia powder serves to virtually eliminate iron powder sintering while maintaining a high reaction rate. The iron/zirconia powder is mixed in a ratio of 1:2 by apparent volume and has a mass ratio of 1:1. Both iron and zirconia particles are sieved to sizes ranging from 125 μm to 355 μm. The efficacy of zirconia as a sintering inhibitor was found to be dependent on the iron and zirconia mean particle size, particle size distribution and iron/zirconia apparent volume ratio. At 650 °C, the oxidation of iron powder with a mean particle size of 100 μm and a wide particle size distribution (40–250 μm) mixed with 44 μm zirconia powder with an iron/zirconia apparent volume ratio of 1:1 results in 75–90% sintering. In all cases, when iron is mixed with zirconia, the hydrogen production rate is not affected when compared with the pure iron case assuming an equivalent mass of iron is in the mixture. When iron powder is mixed with zirconia, both with a narrow particle size distribution (125–355 μm), the first oxidation step results in 3–7% sintering when the reactions are carried out at temperatures ranging between 840 and 895 °C. The hydrogen fractional yield is high (94–97%). For subsequent redox reactions, the macroscopic sintering is totally eliminated at 867 and 895 °C, although the hydrogen fractional yield decreases to 27 and 33%, respectively. It is demonstrated that mixing iron with zirconia in an equivalent mass ratio and similar particle size range can eliminate macroscopic sintering in a fluidized bed reactor at elevated temperatures up to 895 °C.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012202-012202-13. doi:10.1115/1.4024717.

Interest is growing in the benefits of homogeneous charge compression ignition engines. In this paper, we investigate a novel approach to the development of a homogenous charge-like environment through the use of porous media. The primary purpose of the media is to enhance the spread as well as the evaporation process of the high pressure fuel spray to achieve charge homogenization. In this paper, we show through high speed visualizations of both cold and hot spray events, how porous media interactions can give rise to greater fuel air mixing and what role system pressure and temperature plays in further enhancing this process.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012203-012203-9. doi:10.1115/1.4024974.

An experimental investigation of methane fuel oxycombustion in a variable compression ratio, spark-ignited piston engine has been carried out. Compression ratio, spark-timing, and oxygen concentration sweeps were performed to determine peak performance conditions for operation with both wet and dry exhaust gas recirculation (EGR). Results illustrate that when operating under oxycombustion conditions an optimum oxygen concentration exists at which fuel-conversion efficiency is maximized. Maximum conversion efficiency was achieved with approximately 29% oxygen by volume in the intake for wet EGR, and approximately 32.5% oxygen by volume in the intake for dry EGR. All test conditions, including air, were able to operate at the engine's maximum compression ratio of 17 to 1 without significant knock limitations. Peak fuel-conversion efficiency under oxycombustion conditions was significantly reduced relative to methane-in-air operation, with wet EGR achieving 23.6%, dry EGR achieving 24.2% and methane-in-air achieving 31.4%. The reduced fuel-conversion efficiency of oxycombustion conditions relative to air was primarily due to the reduced ratio of specific heats of the EGR working fluids relative to nitrogen (air) working fluid.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012204-012204-11. doi:10.1115/1.4024861.

A state-of-the-art spray modeling methodology is presented. Key features of the methodology, such as adaptive mesh refinement (AMR), advanced liquid–gas momentum coupling, and improved distribution of the liquid phase, are described. The ability of this approach to use cell sizes much smaller than the nozzle diameter is demonstrated. Grid convergence of key parameters is verified for nonevaporating, evaporating, and reacting spray cases using cell sizes down to 1/32 mm. Grid settings are recommended that optimize the accuracy/runtime tradeoff for RANS-based spray simulations.

Topics: Sprays , Simulation
Commentary by Dr. Valentin Fuster

Research Papers: Hydrogen Energy

J. Energy Resour. Technol. 2013;136(1):012601-012601-13. doi:10.1115/1.4024915.

Catalytic systems play an important role in hydrogen production via ethanol reforming. The effect of Ni loading on the characteristics and activities of Ni/Al2O3 catalysts used in pure ethanol steam reforming are not well-understood. Two series of catalysts with various Ni loadings (6, 8, 10, 12, and 20 wt. %) were prepared by impregnation (IMP) and precipitation (PT) methods and were tested in reforming reactions. The catalysts were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDAX). Powder XRD patterns of all the catalysts exhibited only NiO. Lower Ni loading catalysts were more efficient in H2 production, as evidenced by the finding that a 6 wt. % Ni catalyst, synthesized via the PT method, yielded 3.68 mol H2 per mol ethanol fed. The high surface area and small crystallite size of the low Ni loading catalysts resulted in sufficient dispersion and strong metal-support interactions, which closely related to the high activity of the 6 PT catalyst.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2013;136(1):012901-012901-10. doi:10.1115/1.4024857.

Erosion measurements in multiphase slug and annular flow regimes have been made in a horizontal 76.2 mm (3-in.) diameter pipe. These flow regimes are selected since they produce higher metal losses than other flow regimes, and they also occur for a wide variety of operating conditions. Experiments are performed with superficial gas velocities ranging from 15.2 m/s (50 ft/s) to 45.7 m/s (150 ft/s) and superficial liquid velocities ranging from 0.46 m/s (1.5 ft/s) to 0.76 m/s (2.5 ft/s), for liquid viscosities of 1 cP and 10 cP. Three different sand sizes (20, 150, and 300 μm sand) were used for performing tests. The shapes of the sand are also different with the 20 and 300 μm sand being sharper than the 150 μm sand. Erosion measurements are obtained using electrical resistance (ER) probes which relate the change in electrical resistance to the change in the thickness of an exposed element resulting from erosion. Two probes are placed in a bend and another probe is placed in a straight section of pipe. The probes in the bend are flat-head probes, and they are placed flush with the outer wall in the 45 deg and 90 deg positions. The probe in the straight pipe is an angle-head probe which protrudes into the flow with the face placed in the center of the pipe.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012902-012902-8. doi:10.1115/1.4025258.

The use of pumping methods in offshore applications has become common especially in viscous oil production. This follow from the fact they present better efficiency and higher production rate than other lift methods when used in the same conditions, for instance gas lift. Thus, a lift method that has been often used on this scenario due to its satisfactory results is the subsea electrical submersible pump (subsea ESP). This article presents the modeling and simulations of petroleum production facilities equipped with subsea ESP using a commercial software package, the pipesim® from Schlumberger. The production facilities consist of a single vertical producing well completed through its whole thickness in an offshore reservoir. It has been proposed two configurations differing only on the location of the equipment. In the first case, the subsea ESP was installed inside the wellbore and, in the second case on the seabed downstream the wet X-tree. The production rate was simulated for both cases, allowing comparison of the results of each configuration.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2013;136(1):012903-012903-11. doi:10.1115/1.4025019.

Gas compressibility factor or Z-factor for natural gas system can be determined from Standing-Katz charts using the pseudocritical gas pressure and temperatures. These charts give accurate values for Z-factors. Reservoir simulation softwares need accurate correlations to estimate the values of Z-factor; one of the well-known correlations is Dranchuk and Abou-Kassem (DAK) Correlation. This correlation gives large errors at high gas reservoir pressures, this error could be more than 100%. The error in estimating Z-factor will lead to big error in estimating all the other gas properties such as gas formation volume factor, gas compressibility, and gas in place. In this paper a new accurate Z-factor correlation has been developed using regression for more than 300 data points of measured Z-factor using matlab in addition to other data points at low pressure and temperature from Standing-Katz charts and DAK correlation. Old correlations give good estimation of Z-factor at low gas reservoir pressures below 41.37 MPa (6000 psia), at high pressures the error started to appear. The developed correlation is a function of pseudoreduced pressure and temperature of the gas which makes it simpler than the existing complicated correlations. The new correlation can be used to determine the gas compressibility factor at any pressure range especially for high pressures the error was less than 3% compared to the measured data. The developed correlation is very simple to be used, it just needs the gas specific gravity that can be used to determine the pseudocritical properties of the gas and at last the Z-factor can be determined. A new formula of reduced gas compressibility was developed based on the developed Z-factor correlation which in turn can be used to determine the gas compressibility.

Commentary by Dr. Valentin Fuster

Technology Review

J. Energy Resour. Technol. 2013;136(1):014001-014001-9. doi:10.1115/1.4024715.

Energy is a big challenge in the coming years. The global population is increasing. Not only are there more people in the world, but the human drive to increase living standards have increased individual energy demands. Growing energy needs were typically met by finding new sources of fossil fuels. People have fortunately begun to realize the adverse environmental impact of burning fossil fuels and that this practice cannot be maintained indefinitely, leading to renewed interest in photovoltaic technologies. The discovery of the photoelectric effect brought hope to the objective of helping to fill the world energy needs with an already continuously delivered source. The discovery of the photoelectric effect was the birth of the idea, but it was the development of the crystalline silicon cell that marked the beginning of the industry. The cost and inefficiency of these solar panels have prevented them from becoming an economically competitive form of everyday power generation. Cost was reduced with the introduction of amorphous silicon thin-film cells despite slightly lower efficiencies. Their lower manufacturing costs have allowed solar energy to be included in more applications; the costs have not been reduced enough to compete with current grid rates. The current trend in research suggests that the application of nanotechnology may be the awaited break needed to break this cost barrier. Nanotechnology promises to reduce cost because they require less controlled conditions, which will greatly reduce the cost per cell, and the initial cost of a new cell type. Nanoscience and nanotechnology are being researched and developed to help solve problems that have prevented the use of other promising technologies, and improving efficiencies of those technologies that have been developed. The addition of nanoparticles to the matrix is a possible way to improve electron transport, and nanotubes could be used in conjunction with nanoparticles. The science of interactions and addition of nanoparticles and their function in solar photovoltaic cells is known, but still developing. Nanoscience has produced proof-of-concept photovoltaic cells made of small perfect crystals, rather than large, perfect silicon crystals that are more expensive to produce. Nanowhiskers are being experimented as new antireflective coating. Sensitizing dyes are being used to increase the range and location of the wavelengths that can be absorbed to be more favorable to sunlight, allowing the use of materials that lack this key characteristic. Quantum dots could be an improvement to these dyes, as the smaller particles will have the added benefit of having multiple electrons created per photon without impeding electron transfer. Recent research has also shown a method to transform optical radiation into electrical current that could lead to self-powering molecular circuits and efficient data storage. The many possible applications of nanotechnology make photovoltaic cells a promising pursuit.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Energy Resour. Technol. 2013;136(1):014501-014501-5. doi:10.1115/1.4024860.

Two-dimensional (2-D) visualization of hydroxyl (OH) radical in combustion of biofuel made of waste rice bran oil (called W) mixed with octanol (called O) at different mixture ratios were examined in a laboratory scale facility using planar laser-induced fluorescence (PLIF) diagnostics. Rice bran oil has a composition similar to that of peanut oil, with 38% monounsaturated, 37% polyunsaturated, and 25% saturated fatty acids. The ratio of this biofuel to octanol fuel examined was W90/O10, W75/O25, and W60/O40. The chemical species generated from within the combustion zone were analyzed from the spontaneous emission spectra of the flame in the ultraviolet to visible (Uv-Vis) range. The spatial distribution of Nitric Oxide (NO) and OH, denoted as OH*, were identified from the spectra. Two-dimensional (2-D) distributions of flame temperature were obtained using a thermal video camera. The experimental results showed the temperatures to range from 600 °C to 1400 °C. The highest temperature was obtained using W60/O40 waste/octanol fuel mixture. A practical burner commonly used in Indonesia, called semawar, that have a built-in preheating system was used for the combustion of biofuels.

Commentary by Dr. Valentin Fuster

Errata

Commentary by Dr. Valentin Fuster

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