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Research Papers: Air Emissions From Fossil Fuel Combustion

J. Energy Resour. Technol. 2012;134(4):041101-041101-6. doi:10.1115/1.4007483.

The current paper reviews the effects of the oxygenated and nitrogenated additives to see the results of the physicochemical efficiency and performance through engine tests work by gas oil mixtures. The oxygenated compounds used in the formulations compose of 2-methoxy ethyl ether (MXEE), nitromethane, and nitroethane. The presence of ethanol and MXEE significantly alter the characteristics of flash point and distillation curve behaviors and marking up the cetane number, improving the fuel's performance in engine tests. The fuel formulations comprising 2–5% v/v additives, 5–10% v/v ethanol, and diesel 90–95% v/v were produced. The soot formation can be reduced by more than 50%, 30%, and 27% by application of the diesel formulations; E-NE5–10, E-NM5–10, and E-MX5–10, respectively.

Topics: Combustion , Fuels , Diesel , Ethanol , Soot
Commentary by Dr. Valentin Fuster

Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2012;134(4):041201-041201-5. doi:10.1115/1.4007194.

Theoretical and experimental analysis of performance of a solar desalination pond as a second stage of proposed zero discharge desalination processes is considered in this work. Major purpose of this proposed process is producing salt and potable water. Experiments are conducted for brackish wastewater with different salinity content. The relation between temperature variations of brackish water, glass, and base of solar desalination pond with condensation rate are discussed. Results indicate when brackish water temperature is increasing; the average daily production of solar desalination pond is increased considerably. Results of the mathematical modeling show good agreement with experimental data.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(4):041202-041202-7. doi:10.1115/1.4007656.

Generation of distributed wind energy systems is being investigated as an answer to increased energy demand, since these systems achieve both economic and energy benefits. The purpose of the present article is to demonstrate a new method developed by the authors that optimizes the design of a wind production plant. Traditionally, the design strategy is primarily based on maximizing the economic benefit, to the detriment of other technical aspects. This study proposes a plant design method that, in a future with decreased governmental incentives, adapts the daily production curve to the demand curve with minimal decrease in economic benefit—a highly desirable result. This is achieved by installing generators in several locations that have different features of daily wind speed. In this way a better use of the energy is encouraged.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Conversion/Systems

J. Energy Resour. Technol. 2012;134(4):041601-041601-6. doi:10.1115/1.4007253.

In this paper, a multizone model is developed to investigate the performance of an economizer under all conditions. The model primarily determines the economizer’s distribution parameters under all conditions with a small computational cost. Both the steady-state and dynamic behavior are calculated. These results are shown to be accurate and reliable using a computational fluid dynamic (CFD) model and the operational data obtained from a 600 MW boiler unit in Hubei province, China. Additionally, the model is used to predict the distribution characteristics during some fault conditions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(4):041602-041602-5. doi:10.1115/1.4007360.

This work is intended to systematically study an inventory of the anthropogenic heat produced. This research strives to present a better estimate of the energy generated by humans and human activities, and compare this estimate to the significant energy quantity with respect to climate change. Because the top of atmosphere (TOA) net energy flux was found to be 0.85 ± 0.15 W/m2 the planet is out of energy balance, as studied by the group from NASA in 2005. The Earth is estimated to gain 431 terawatts (TW) from this energy imbalance. This number is the significant heat quantity to consider when studying global climate change, and not the 78,300 TW, the absorbed part of the primary solar radiation reaching the Earth's surface, as commonly cited and used at present in the literature. Based on energy supplied to the boilers (in the Rankine cycle) of at least 13 TW, body energy dissipated by 7 × 109 people and their domestic animals, the value of the total world anthropogenic heat production rate is 15.26 TW or 3.5% of the energy gain by the Earth. Based on world energy consumption and the energy dissipated by 7 × 109 people and their domestic animals, the value of the total world anthropogenic heat production rate is 19.7 TW or about 5% of the energy gain by the Earth. These numbers are significantly different from 13 TW. More importantly, the figures are 3.5–5% of the net energy gained by the Earth, and hence significant. The quantity is not 0.017% of the absorbed part of the main solar radiation reaching the Earth's surface and negligible.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(4):041603-041603-6. doi:10.1115/1.4007482.

A new methodology is developed for local entropy generation analysis of turbulent flows using large eddy simulation (LES). The entropy transport equation is considered in LES and is solved along with continuity, momentum, and scalar transport equations. The filtered entropy equation includes several unclosed source terms that contribute to entropy generation. The closure is based on the filtered density function (FDF) methodology, extended to include the transport of entropy. An exact transport equation is derived for the FDF. The unclosed terms in this equation are modeled by considering a system of stochastic differential equations (SDEs). The methodology is employed for LES of a turbulent shear layer involving transport of passive chemical species, energy, and entropy. The local entropy generation effects are obtained from the FDF and are analyzed. It is shown that the dominant contribution to entropy generation in this flow is due to combined effects of energy transfer by heat and mass diffusion. The FDF results are assessed by comparing with those obtained by direct numerical simulation (DNS) of the same layer. The FDF predictions show favorable agreements with the DNS data.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Extraction From Natural Resources

J. Energy Resour. Technol. 2012;134(4):041701-041701-8. doi:10.1115/1.4007193.

In developing a wave energy converter (WEC), assessing and rating the device is a difficult, but important issue. Conventionally, a large scaled device (maybe large enough for accommodating a power takeoff (PTO) system) or prototype device is needed to be tested in wave tanks or in seas in different wave conditions so that a power matrix for the device can be defined using scaling or interpolation/extrapolation methods. Alternatively, a pure numerical simulation in time-domain may be used for assessing the power capture capacities of wave energy devices. For the former, it is convincing, but can be especially difficult in the early stages of development, when small scaled models are normally used; and for the latter, the pure numerical simulation may not be very reliable and convincing, especially when the dynamic problem is very complicated. In this paper, a method for assessing the captured wave power for a device from its power capture response is presented. In the proposed method, a measured or calculated linear power capture response of the device is combined with wave spectrum to compute the average captured power function. Once the average captured power function is obtained, the overall average captured power corresponding to the wave state can be easily calculated. If a linear power capture response is obtained from a model test, the power assessment based on this proposed method can be very convincing and reliable. To illustrate the application of the proposed method, an example of a fully linear dynamic system, including the linear hydrodynamics of the floating structure and a linear power takeoff, is considered. For such a system, the frequency-domain analysis can be employed to obtain the performance of the floating device under waves and the power takeoff system. The hydrodynamic performance of the wave energy converter is then used to define the power capture response and to calculate the average captured power functions in different sea states. Then, the captured power of the device in different sea states, i.e, the power matrix, can be calculated, and accordingly, the device can be assessed and rated. To validate the proposed method, a time-domain analysis is also performed for a cross-check. In the time-domain analysis, the hydrodynamic coefficients and responses are first assessed in frequency-domain, and then transformed into the relevant terms by means of impulse response functions for establishing the time-domain (TD) equation. By comparing the results from frequency-domain and time-domain analyses of irregular waves, it can be concluded that the proposed wave energy capture assessment method can be used in assessing or rating the device.

Commentary by Dr. Valentin Fuster

Research Papers: Energy From Biomass

J. Energy Resour. Technol. 2012;134(4):041801-041801-11. doi:10.1115/1.4007484.

Torrefied biomass is a green alternative to coal, and thus the interest in the torrefaction process is rising fast. Different manufacturers are offering different patented designs of torrefier with data on varying operating and process conditions each claiming their superiority over others. The choice of torrefaction technology has become exceptionally difficult because of a near absence of a comparative assessment of different types of reactors on a common base. This work attempts to fill this important knowledge gap in torrefaction technology by reviewing available types of reactors, and comparing their torrefaction performance common basis and examining the commercial implication of reactor choice. After reviewing available patent and technologies offered, torrefiers are classified broadly under two generic groups: indirectly heated and directly heated. Four generic types of reactors, convective heating, fluidized bed, rotating drum and microwave reactor were studied in this research. Convective and fluidized beds have direct heating, rotating reactors has indirect heating while microwave involves a volumetric heating (a subgroup of direct heating) mechanism. A standard sample of biomass (25 mm diameter × 64 mm long poplar wood) was torrefied in each of these types of reactors under identical conditions. The mass yield, energy density and energy yield of the wood after torrefaction were measured and compared. Rotating drum achieved lowest mass yield but highest energy density. The difference between two direct heating, convective heating and fluidized beds was small. Microwave provided only localized torrefaction in this series of tests. Indirectly heated reactors might be suitable for a plant near the biomass source while directly heated plant would give better value at the user end.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2012;134(4):042001-042001-9. doi:10.1115/1.4007659.

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture (USDA). USDA is an equal opportunity provider and employer. Mass, energy, and exergy balances are analyzed for bio-oil production in a bench-scale fast pyrolysis system developed by the USDA’s Agricultural Research Service (ARS) for the processing of commodity crops to fuel intermediates. Because mass balance closure is difficult to achieve due, in part, to the system’s small size and complexity a linear programming optimization model is developed to improve closure of elemental balances without losing the overall representation of the pyrolysis products. The model results provide an opportunity to analyze true energy and exergy balances for the system. While energy comparisons are based on heating values, exergy flows are computed using statistical relationships and other standard techniques. Comparisons were made for a variety of biomass feedstocks including energy crops and various byproducts of agriculture and bioenergy industry. The mass model allows for proper accounting of sources of mass loss and suggestions for improved system performance. Energy recovery and exergetic efficiency are compared for a variety of pyrolysis product utilization scenarios including use of biochar and noncondensable gases as heat sources. Exergetic efficiencies show high potential for energy utilization when all the pyrolysis product streams can be recycled to recuperate their internal energy. The exergy analysis can be beneficial to developing exergetic life cycle assessments (ELCA) for the fast pyrolysis process as sustainable technology for advanced biofuels production.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2014;134(4):042002-042002-1. doi:10.1115/1.4007663.

The above referenced paper is being retracted from the Journal of Energy Resources Technology because of unrebutted allegations that it contains confidential and proprietary information used without permission.

Commentary by Dr. Valentin Fuster

Research Papers: Environmental Aspect of Energy Sources

J. Energy Resour. Technol. 2012;134(4):042101-042101-8. doi:10.1115/1.4007486.

Urban heat island intensity (UHII) is calculated as the spatially averaged temperature difference between an urban and its surrounding rural area. This concept, however, provides an umbrella for a range of diversified ideas that include the temperature difference between the densely developed urban area and least developed area or between two different built-up areas. There are also averages for the season, for the year, for multiple years, etc., and UHII quoted for the day and another for the night. The objective of this work is to examine the urban heat island effect for cities around the world, using readily available data. The innovation is in using data from the Landsat satellites for different cities previously not studied. Thermal images of the Earth were obtained and analyzed to produce surface-temperature maps. These maps showed that the temperature in the urban environments were significantly higher than the temperature in the surrounding countryside, a defining characteristic of urban heat island. Furthermore, the urban and rural areas in the images were separated and analyzed individually to quantitatively measure the temperature difference. It was found that the UHII could be 0.3–5.1 °C for the eleven cities investigated. Miami and Shenzen are two cities which seem to have been missed in previous studies because they were limited in their scope and responsibilities, and their methods required much more resources for the longer term studies. It is not the claim here that a UHI is definitively established by the analysis presented of the Landsat satellite data. The present work demonstrates the use of a possible planning tool in terms of understanding where urban areas may be subjected to additional heat. Our use of the method shows that a UHI is probably taking place at the time of observation, and precautionary notices should be sent out to the community to take preventative measures to ensure their health and wellbeing. The minimal resources required is the demonstration shown by our work of the usefulness of this method.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2012;134(4):042201-042201-6. doi:10.1115/1.4007252.

In previous work, it is reported that increased dilution at midrange injection pressures produces longer first stage combustion duration. There is also corresponding decreases in nitric oxide concentrations and smoke number with respect to a reference conventional combustion mode. Continuing this effort, the objective of this study is to investigate the effect of injection pressure on the first stage ignition duration under low temperature combustion (LTC) conditions. A sweep of injection pressure is performed and the resulting heat (energy) release profiles are examined. The ignition delay behavior is expected based on changing injection pressure, but the first stage ignition duration does not follow expected trends based on initial literature review. It is postulated that the influence of injection pressure on the local equivalence ratios is causing the observed behavior. The appropriate measurement and analysis tools are not available to the authors to confirm this postulation. A literature review of work investigating ignition conditions in low temperature combustion modes is used to support the postulation made in this study.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;134(4):042202-042202-10. doi:10.1115/1.4007485.

On-road transportation contributes 22% of the total CO2 emissions and more than 44% of oil consumption in the U.S. technological advancements and use of alternative fuels are often suggested as ways to reduce these emissions. However, many parameters and relationships that determine the future characteristics of the light-duty vehicle (LDV) fleet and how they change over time are inherently uncertain. Policy makers need to make decisions today given these uncertainties, to shape the future of light-duty vehicles. Decision makers thus need to know the impact of uncertainties on the outcome of their decisions and the associated risks. This paper explores a carefully constructed detailed pathway that results in a significant reduction in fuel use and greenhouse gases (GHG) emissions in 2050. Inputs are assigned realistic uncertainty bounds, and the impact of uncertainty on this pathway is analyzed. A novel probabilistic fleet model is used here to quantify the uncertainties within advanced vehicle technology development, and life-cycle emissions of alternative fuels and renewable sources. Based on the results from this study, the expected fuel use is about 500 and 350 × 109 l gasoline equivalent, with a standard deviation of about 40 and 80 × 109 l in years 2030 and 2050, respectively. The expected CO2 emissions are about 1360 and 840 Mt CO2 equivalent with a spread of about 130 and 260 Mt CO2 equivalent in 2030 and 2050, respectively. Major contributing factors in determining the future fuel consumption and emissions are also identified and include vehicle scrappage rate, annual growth of vehicle kilometres travelled in the near term, total vehicle sales, fuel consumption of naturally aspirated engines, and percentage of gasoline displaced by cellulosic ethanol. This type of analysis allows policy makers to better understand the impact of their decisions and proposed policies given the technological and market uncertainties that we face today.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Wells-Drilling/Production/Construction

J. Energy Resour. Technol. 2012;134(4):043101-043101-8. doi:10.1115/1.4007658.

This paper presents a simple analytical method to model the non-Darcy flow effect on the production performance of hydraulically fractured wells by modifying the fracture conductivity. The method is suitable to conveniently incorporate the non-Darcy flow effect in a production prediction model usually used for fracture treatment design and optimization. The method is validated against published information of field productivity and production prediction by other complex methods. The method is then used to demonstrate that the non-Darcy effect is one of the major sources for the loss of fracture conductivity, even at a low flow rate well, and hence the source for discrepancy between the predicted and actual productivities. Finally, the implication of neglecting the non-Darcy effect in fracture treatment optimization is also investigated, emphasizing the need to incorporate this effect even for low flow rate wells.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Energy Resour. Technol. 2012;134(4):044501-044501-8. doi:10.1115/1.4007086.

This study evaluates the integral use of the sugarcane bagasse on the productive process of a cogeneration power plant in an Ecuadorian Sugar Company. Thermoelectric power plants burning biomass require a large initial investment and, for example, this initial investment requires $800/kW, which is double the initial investment of a conventional thermoelectric power plant that is $400/kW, and almost similar to the initial cost of a hydroelectric power plant that is $1000/kW. A thermoeconomic study was made on the production of electricity and the sales of the exceeding 27 MW average. From the results, it was concluded that generated electricity costs are $0.0443/kW h, in comparison with the costs of the supplied electricity through fossil power plants with values in the range $0.03–$0.15/kW h and hydroelectric power plants with a value of about $0.02/kW h. Cogeneration power plants burning sugarcane bagasse could contribute to the mitigation of climatic change. This specific case study shows the reduction of the prospective emissions of greenhouse effect gases in the amount of 55,188 ton of CO2 equivalent per year.

Commentary by Dr. Valentin Fuster

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