Invited Discussion

J. Energy Resour. Technol. 2004;126(1):1-5. doi:10.1115/1.1653768.

World Commission on Environment and Development, 1987. Our Common Future, Oxford University Press.Elkington, J., 1962, Cannibals with Forks, Capstone Publishing, Carson, R., Silent Spring, Houghton Mifflin, New York City.Wilson, E. O., 2002, The Future of Life, Knopf, N.Y.UNEP, 2002, Global Environmental Outlook 3, Earthscan Publications.Becker, L., 2002, Repeated Blows, Scientific American, p. 78.Scientific American, 2001, Extinctions, p. 42.Mannion, A. M., 1999, Natural Environmental Change, Routledge, London.UNPD, WorldPopulationProspects.www.un.org/esa/population/publications/wpp200/highlights.pdfwww.worldbank.org/poverty/mission/up2.htm.Lomborg, B., 2001, The Skeptical Environmentalist, Cambridge University Press.Edwards, J. D., 2001, EMARC, Twenty First Century Energy, Dept. Geological Sciences, Univ. Colorado.Deffeyes, K. S., 2001, Hubbert’s Peak, Princeton University Press.Schollnberger, W. E., 1998, Projections of the World’s Hydrocarbon Resources and Reserve Depletion in the 21st. Century, Houston Geological Society Bulletin.www.earthsummit2002.org.OGP/IPIECA, Industry as a Partner for Sustainable Development, 2002 www.ogp.org.uk Report prepared for the 2002 World Summit on Sustainable Development.Oil in the Sea III: Inputs, Fates, and Effects, 2002, National Academy Press.International Tanker Owners Pollution Federation (ITOPF) report 2002, www.itopf.com/stats.html.Gerhard, L. C., Harrison, W. E., and Hanson, B. M., (Editors) 2001, Geological Perspectives of Global Climate Change, AAPG studies in Geology #47.IPCC Third Assessment Report of Working Group 1, 2001, www.ipcc.ch/pub/spm22-01.pdf.Petit, J. R., Jouze, J., et al. 1999, Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core in Antartica, Nature. (see also www.grida.no/climate/vital/02.htm)Environmental Benefits of Advanced Oil and Gas Exploration and Production Technology, USDOE, October 1999, report #DOE FE 0385.www.unepwcmc.org.Arscott R. L., 2003, Sustainable Development in the Oil and Gas Industry, JPT, Aug. and Sept. 2003 (2 parts), SPE paper #83062, San Antonio.

Commentary by Dr. Valentin Fuster


J. Energy Resour. Technol. 2004;126(1):6-12. doi:10.1115/1.1649247.

Benzene emissions occur during marine vessel loading operations. These emissions are regulated in several countries. Accordingly, we developed a one-dimensional benzene diffusion model advancing in the vertical direction within cargo tanks. Unlike other models, the model presented in this paper is based on a 1/10 scale modeling of eddy diffusion at the liquid surface during initial loading operations and advection under the tank roof during final loading operations. The model input parameters include loading rate, flow rate, cargo tank size, and temperature dependent saturated concentrations. The validity of the model is demonstrated by comparisons with onboard measurements. Other models exist. However, they are based on empirical estimates rather than rational modeling.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):13-20. doi:10.1115/1.1627366.

A numerical study of NOx reduction for a Direct Injection (DI) Diesel engine with complex geometry, which includes intake/exhaust ports and moving valves, was carried out using the commercial computational fluid dynamics software KIVA-3v. The numerical simulations were conducted to investigate the effects of engine operating and geometrical parameters, including fuel injection timing, fuel injection duration, and piston bowl depth, on the NOx formation and the thermal efficiency of the DI Diesel engine. The tradeoff relationships between the reduction in NOx and the decrease in thermal efficiency were established.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):21-29. doi:10.1115/1.1647130.

Thermodynamic, geometric, and economic models are developed for a proton exchange membrane (PEM) fuel cell system for use in cogeneration applications in multi-unit residential buildings. The models describe the operation and cost of the fuel processing sub-system and the fuel cell stack sub-system. The thermodynamic model reflects the operation of the chemical reactors, heat exchangers, mixers, compressors, expanders, and stack that comprise the PEMFC system. Geometric models describe the performance of a system component based on its size (e.g., heat exchanger surface area), and, thus, relate the performance at off-design conditions to the component sizes chosen at the design condition. Economic models are based on data from the literature and address the cost of system components including the fuel processor, the fuel cell materials, the stack assembly cost, the fuel cost, etc. As demonstrated in a forthcoming paper, these models can be used in conjunction with optimization techniques based on decomposition to determine the optimal synthesis and design of a fuel cell system. Results obtained using the models show that a PEMFC cogeneration system is most economical for a relatively large cluster of residences (i.e. 50) and for manufacturing volumes in excess of 1500 units per year. The analysis also determines the various system performance parameters including an electrical efficiency of 39% and a cogeneration efficiency of 72% at the synthesis/design point.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):30-39. doi:10.1115/1.1650390.

The application of a decomposition methodology to the synthesis/design optimization of a stationary cogeneration proton exchange membrane (PEM) fuel cell system for residential applications is the focus of this paper. Detailed thermodynamic, economic, and geometric models were developed to describe the operation and cost of the fuel processing sub-system and the fuel cell stack sub-system. Details of these models are given in an accompanying paper by the authors. In the present paper, the case is made for the usefulness and need of decomposition in large-scale optimization. The types of decomposition strategies considered are conceptual, time, and physical decomposition. Specific solution approaches to the latter, namely Local-Global Optimization (LGO) are outlined in the paper. Conceptual/time decomposition and physical decomposition using the LGO approach are applied to the fuel cell system. These techniques prove to be useful tools for simplifying the overall synthesis/design optimization problem of the fuel cell system. The results of the decomposed synthesis/design optimization indicate that this system is more economical for a relatively large cluster of residences (i.e. 50). Results also show that a unit cost of power production of less than 10 cents/kWh on an exergy basis requires the manufacture of more than 1500 fuel cell sub-system units per year. Finally, based on the off-design optimization results, the fuel cell system is unable by itself to satisfy the winter heat demands. Thus, the case is made for integrating the fuel cell system with another system, namely, a heat pump, to form what is called a total energy system.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):40-46. doi:10.1115/1.1653752.

Several empirical assumptions deriving from observations and measurements of the physical processes are involved in the modeling of Solid Oxide Fuel Cells (SOFCs). An insight of the main models proposed in the literature is given to present the characteristics and limits of these assumptions for the various existing configurations. The basic structure and equations of the models are discussed in details, focusing particularly on the parameters that are to be set to achieve reliability and accuracy. According to this discussion, a zero-dimensional model for a tubular Solid Oxide Fuel Cell (SOFC) is then presented. The model demonstrates good capability in predicting SOFC characteristic curves as they appear in the literature.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):47-53. doi:10.1115/1.1628677.

This paper presents a direct method for determining natural frequencies of lateral modes of vibration for marine risers in deep water. This method applies to marine risers that are vertical, relatively straight, and attached at both ends. The method is particularly useful for determining natural frequencies of higher modes that are sometimes difficult to obtain analytically or numerically. Comparisons of numerical results with published data show that even though the method of solution is approximate, the calculation procedure gives useful engineering results. The algorithm is based on classical vibration theory and can easily be programmed on portable computers for direct use on offshore oil rigs.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):54-62. doi:10.1115/1.1649971.

Accurate prediction of slug length distribution and the maximum slug length in a hilly terrain pipeline is crucial for designing downstream separation facilities. A hilly terrain pipeline consists of interconnected uphill and downhill pipe sections, where slugs can dissipate in the downhill sections and grow in the uphill sections. Furthermore, new slugs can be generated at the dips (bottom elbows) and dissipate at the top elbows. Although existing steady-state models are capable of predicting the average slug length for pressure drop calculations and pipeline design, they are incapable of predicting detailed flow characteristics such as the maximum slug length expected at the exit of a hilly terrain pipeline. A transient slug tracking model based on a quasi-equilibrium formulation was developed to track the front and back of each individual slug, from which individual slug lengths are calculated. The model was verified with large-scale two-phase flow hilly terrain experimental data acquired at the Tulsa University Fluid Flow Projects (TUFFP). The results show a fairly accurate match between the model predictions and experimental data.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):63-71. doi:10.1115/1.1649740.

A deterministic quantitative model has been developed to compare the technical, economical and environmental feature of various electric power generating plants. The model, which is based on matrix operations, is used in evaluating the various aspects of energy sources available for electricity generation systems in a developing country. Several energy sources which could be considered for production of electricity to meet current and future electricity demands have been chosen. These will include fossil fuel fired, nuclear, and natural-renewable energy power plants. And, a set of criteria for optimized selection includes five area of concerns: energy economy, energy security, environmental protection, socio-economic development and technological aspects for the electric power generations. The model developed in this study is applied to the Indonesian’s electric power sector development. Most of the data required are obtained from various sources related to power industry in Indonesia, such as the electricity generating authority of Indonesia (Perusahaan Listrik Negara, PLN), Government of Indonesia, World Bank, Asian Development Bank, United Nations, and other sources, both in published and public domains. The result of this study will be a ranking of energy sources for Indonesia power generation systems based on the Euclidean composite distance of each alternative to the designated optimal source of energy.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2004;126(1):72-81. doi:10.1115/1.1625396.

For the present work, a numerical simulation of the 100% oxy-firing combustion process inside an industrial aluminum remelting reverb furnace is presented. Three different configurations were analyzed: (i) a staged combustion process with parallel injection jets for oxygen and natural gas, (ii) a staged combustion process with a divergent jet for the oxygen, and (iii) a non-staged combustion process, with parallel jets. In all the cases, the injections were directed towards the aluminum bath, which was maintained at constant temperature. The numerical procedure was based on the finite volume formulation. The κ-ε model of turbulence was selected for simulating the turbulent flow field. The combustion process was calculated based on the finite rate models of Arrhenius and Magnussen, and the Discrete Transfer Radiation model was employed for predicting the radiation heat transfer. The numerical predictions allowed the determination of the flame patterns, species concentration distribution, temperature and velocity fields. This kind of analysis can be a powerful tool for evaluating design options such as the type, number and positioning of the burners. The present work illustrates a preliminary comparison of three types of burners. From the results obtained, the staged combustion process with a divergent jet presented the best configuration, since the flame length was not too long as to damage the refractory wall. Further it presented the largest region with low water vapor concentration close to the aluminum surface.

Commentary by Dr. Valentin Fuster

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