Energy impact of modifications of a river freight transport system: The upper Mississippi

As an example of analysis of the energy impact of enlarging a river freight-transport system, we consider Locks and Dam 26 near Alton, Illinois, which is the principal bottleneck of the upper Mississippi River. A simple queueing theory model is developed to predict the average delay time prior to processing through the locks as a function of traffic growth rates. Estimates of the energy intensity of freight transport on the upper Mississippi are made from a theoretical model and compared with values published in the literature. The energy impact of the replacement of Locks and Dam 26 is assessed by combining the results of the traffic-flow and energy-intensity models. For a traffic growth rate of 2.5%/yr, the cumulative energy savings (during a 40 yr operating life) of replacing the current facility is nearly 20 × 10¹² Btu. The economic value of the energy savings is 40–85% of the cost differential between repairing the current installation with no increase in capacity and the construction of an entirely new facility with a 100% increase in main locking chamber size.     

Design optimization of a large scale rooftop photovoltaic system

This paper presents the optimization process of a grid connected photovoltaic (PV) system, which is intended to replace a large-scale thermal solar system on the rooftop of a Federal office building. A PV energy conversion model is described. Based on this model, array surface tilt angle and array size are optimized. The optimization method is based on maximizing the utilization of the array output energy, and, at the same time, minimizing the electricity power sold to grid. An effectiveness factor is introduced that takes into account both of these parameters. The array configuration and the output parameters are determined by comparing several PV modules. A 43.2 kW PV system is designed and operational problems such as harmonic effects and anti-islanding are discussed. Finally, the system performance is simulated and through economic analysis it has shown that the cost of PV system can be recouped in 13 years under the current renewable energy incentive program by the state of Illinois.     

Economics of herbaceous bioenergy crops for electricity generation: Implications for greenhouse gas mitigation

This paper examines the optimal land allocation for two perennial crops, switchgrass and miscanthus that can be co-fired with coal for electricity generation. Detailed spatial data at county level is used to determine the costs of producing and transporting biomass to power plants in Illinois over a 15-year period. A supply curve for bioenergy is generated at various levels of bioenergy subsidies and the implications of production for farm income and greenhouse gas (GHG) emissions are analyzed. GHG emissions are estimated using lifecycle analysis and include the soil carbon sequestered by perennial grasses and the carbon emissions displaced by these grasses due to both conversion of land from row crops and co-firing the grasses with coal. We find that the conversion of less than 2% of the cropland to bioenergy crops could produce 5.5% of the electricity generated by coal-fired power plants in Illinois and reduce carbon emissions by 11% over the 15-year period. However, the cost of energy from biomass in Illinois is more than twice as high as that of coal. Costly government subsidies for bioenergy or mandates in the form of Renewable Portfolio Standards would be needed to induce the production and use of bioenergy for electricity generation. Alternatively, a modest price for GHG emissions under a cap-and-trade policy could make bioenergy competitive with coal without imposing a fiscal burden on the government.     

Hydrogen as a long-term,large-scale energy storage solution when coupled with renewable energy sources or grids with dynamic electricity pricing schemes

One of the key challenges that still facing the adoption of renewable energy systems is having a powerful energy storage system (ESS) that can store energy at peak production periods and return it back when the demand exceeds the supply. In this paper, we discuss the costs associated with storing excess energy from power grids in the form of hydrogen using proton exchange membrane (PEM) reversible fuel cells (RFC). The PEM-RFC system is designed to have dual functions: (1) to use electricity from the wholesale electricity market when the wholesale price reaches low competitive values, use it to produce hydrogen and then convert it back to electricity when the prices are competitive, and (2) to produce hydrogen at low costs to be used in other applications such as a fuel for fuel cell electric vehicles. The main goal of the model is to minimize the levelized cost of energy storage (LCOS), thus the LCOS is used as the key measure for evaluating this economic point. LCOS in many regions in United States can reach competitive costs, for example lowest LCOS can reach 16.4¢/kWh in Illinois (MISO trading hub) when the threshold wholesale electricity price is set at $25/MWh, and 19.9¢/kWh in Texas (ERCOT trading hub) at threshold price of $20/MWh. Similarly, the levelized cost of hydrogen production shows that hydrogen can be produced at very competitive costs, for example the levelized cost of hydrogen production can reach $2.54/kg-H₂ when using electricity from MISO hub. This value is close to the target set by the U.S. Department of Energy.     

Biofuel subsidies versus the gas tax: The carrot or the stick?

This paper provides an analytical framework to examine the relative efficiencies of a revenue-neutral biofuel subsidy and a gas tax in the presence of pre-existing distortions and growing substitutability between fuels. Both policies are set to achieve a targeted reduction in gasoline use at the state level. The model is then calibrated for a small open economy such as Illinois which is one of the largest producers of biofuels such as ethanol in the U.S. The main result of the paper shows that raising the biofuel subsidy use reduces overall welfare by more than a higher gas tax, both aimed to achieve a targeted reduction in pure gasoline. The relative efficiency of the higher gas tax is primarily due to it exacerbating the pre-existing distortion in the biofuel market by less than the subsidy. Moreover, for current parameter estimates welfare improving policy combinations for achieving a targeted amount of energy security are higher gas taxes combined with lower biofuel subsidies and a lower tax on income. However, the preference for a gasoline–labor tax swap shrinks as the elasticity of substitution between the two fuels rises.     

Development and application of BioFeed model for optimization of herbaceous biomass feedstock production

An efficient and sustainable biomass feedstock production system is critical for the success of the biomass based energy sector. An integrated systems analysis framework to coordinate various feedstock production related activities is, therefore, highly desirable. This article presents research conducted towards the creation of such a framework. A breadth level mixed integer linear programming model, named BioFeed, is proposed that simulates different feedstock production operations such as harvesting, packing, storage, handling and transportation, with the objective of determining the optimal system level configuration on a regional basis. The decision variables include the design/planning as well as management level decisions. The model was applied to a case study of switchgrass production as an energy crop in southern Illinois. The results illustrated that the total cost varied between 45 and 49 $ Mg⁻¹ depending on the collection area and the sustainable biorefinery capacity was about 1.4 Gg d⁻¹. The transportation fleet consisted of 66 trucks and the average utilization of the fleet was 86%. On-farm covered storage of biomass was highly beneficial for the system. Lack of on-farm open storage and centralized storage reduced the system profit by 17% and 5%, respectively. Increase in the fraction of larger farms within the system reduced the cost and increased the biorefinery capacity, suggesting that co-operative farming is beneficial. The optimization of the harvesting schedule led to 30% increase in the total profit. Sensitivity analysis showed that the reduction in truck idling time as well as increase in baling throughput and output density significantly increased the profit.     

The role of energy storage in accessing remote wind resources in the Midwest

Replacing current generation with wind energy would help reduce the emissions associated with fossil fuel electricity generation. However, integrating wind into the electricity grid is not without cost. Wind power output is highly variable and average capacity factors from wind farms are often much lower than conventional generators. Further, the best wind resources with highest capacity factors are often located far away from load centers and accessing them therefore requires transmission investments. Energy storage capacity could be an alternative to some of the required transmission investment, thereby reducing capital costs for accessing remote wind farms. This work focuses on the trade-offs between energy storage and transmission. In a case study of a 200 MW wind farm in North Dakota to deliver power to Illinois, we estimate the size of transmission and energy storage capacity that yields the lowest average cost of generating and delivering electricity ($/MW h) from this farm. We find that transmission costs must be at least $600/MW-km and energy storage must cost at most $100/kW h in order for this application of energy storage to be economical.     

Application of probabilistic wind power forecasting in electricity markets

This paper discusses the potential use of probabilistic wind power forecasting in electricity markets, with focus on the scheduling and dispatch decisions of the system operator. We apply probabilistic kernel density forecasting with a quantile‐copula estimator to forecast the probability density function, from which forecasting quantiles and scenarios with temporal dependency of errors are derived. We show how the probabilistic forecasts can be used to schedule energy and operating reserves to accommodate the wind power forecast uncertainty. We simulate the operation of a two‐settlement electricity market with clearing of day‐ahead and real‐time markets for energy and operating reserves. At the day‐ahead stage, a deterministic point forecast is input to the commitment and dispatch procedure. Then a probabilistic forecast is used to adjust the commitment status of fast‐starting units closer to real time, on the basis of either dynamic operating reserves or stochastic unit commitment. Finally, the real‐time dispatch is based on the realized availability of wind power. To evaluate the model in a large‐scale real‐world setting, we take the power system in Illinois as a test case and compare different scheduling strategies. The results show better performance for dynamic compared with fixed operating reserve requirements. Furthermore, although there are differences in the detailed dispatch results, dynamic operating reserves and stochastic unit commitment give similar results in terms of cost. Overall, we find that probabilistic forecasts can contribute to improve the performance of the power system, both in terms of cost and reliability. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessment of an Integrated Gasification Combined Cycle using waste tires for hydrogen and fresh water production

In this paper, an Integrated Gasification Combined Cycle (IGCC), which uses waste tires as a feedstock, for power, hydrogen and freshwater production is modeled using both EES and Aspen Plus software packages and assessed thermodynamically. During the study, it is found that tire gasification is a viable solution for leftover tire waste in the world. Furthermore, the novel integration of a multi effect desalination plant, driven by the excess heat from the combined cycle, further increases the systems plant efficiency. The hydrogen production to feed rate ratio is found to be 0.154, which is competitive to high-quality coals, such as Illinois No.6, making waste tires an excellent feedstock to produce hydrogen. The net power production output from the combined cycle is 14.5 MW which was driven by the excess thermal energy of the syngas. The water distillate production rate from the forward flow multi-effect desalination plant at the set conditions is found to be 0.99 kg/s. The systems overall energy and exergy efficiencies obtained are 58.9% and 57.4%, respectively.     

Exergy analysis of Illinois No. 6 coal

The projected increase in coal utilization in utility power plants makes it desirable to refine customary evaluations of coal which are based on the First Law of Thermodynamics. Presented in this paper is a Second Law or exergy analysis of Illinois No. 6 coal. A theoretical analysis is carried out and the quality of coal is calculated. The methodology, although applied to Illinois No. 6 coal, should be applicable to other coals or non-homogeneous fuels.     

Analysis of oil prices’ interaction in the USA based on complex networks

This paper focuses on a new method of converting multidimensional time series into complex networks. Compared with the previous studies, this method puts different variables into the same high-dimensional system, not only can study the properties of individual variables but also can investigate the correlation between different variables and its dynamic evolution process. Taking the monthly crude oil price data of 23 regions in the United States as a sample, a complex network diagram of crude oil market prices was constructed in this paper. Through the study of network node degree, clustering coefficient and betweenness, this paper analyzes the linkage between crude oil markets. It is shown that the Illinois region is very important in the interaction of oil prices in the 23 regions of the USA. North Slope region in the network diagram is the middle junction of different node groups. This research can provide theoretical support for policy-making in the energy market.     

Simulation studies of the membrane exchange assembly of an all-liquid,proton exchange membrane fuel cell

A model has been designed and constructed for the all-liquid, sodium borohydride/hydrogen peroxide fuel cell under development at the University of Illinois at Urbana-Champaign. The electrochemical behavior, momentum balance, and mass balance effects within the fuel cell are modeled using the Butler–Volmer equations, Darcy's law, and Fick's law, respectively, within a finite element modeling platform. The simulations performed with the model indicate that an optimal physical design of the fuel cell's flow channel land area or current collector exists when considering the pressure differential between channels, and the diffusion layer permeability and conductivity. If properties of the diffusion layer are known, the model is an effective method of improving the fuel cell design in order to achieve higher power density.     

Impact of plug-in hybrid electric vehicles on power systems with demand response and wind power

This paper uses a new unit commitment model which can simulate the interactions among plug-in hybrid electric vehicles (PHEVs), wind power, and demand response (DR). Four PHEV charging scenarios are simulated for the Illinois power system: (1) unconstrained charging, (2) 3-hour delayed constrained charging, (3) smart charging, and (4) smart charging with DR. The PHEV charging is assumed to be optimally controlled by the system operator in the latter two scenarios, along with load shifting and shaving enabled by DR programs. The simulation results show that optimally dispatching the PHEV charging load can significantly reduce the total operating cost of the system. With DR programs in place, the operating cost can be further reduced.     

Optimal design of advanced drop-in hydrocarbon biofuel supply chain integrating with existing petroleum refineries under uncertainty

This paper addresses the optimal design of an advanced hydrocarbon biofuel supply chain integrated with existing petroleum refineries. Three major insertion points from the biofuel supply chain to the petroleum refineries are investigated and analyzed, including bio-intermediates co-processed with crude oil, bio-intermediates co-processed with refinery intermediates, and finished biofuels blended with conventional petroleum products. A multiperiod, mixed-integer linear programming model is proposed that accounts for diverse conversion pathway, technology, and insertion point selections, biomass seasonality, geographical diversity, biomass degradation, demand distribution and government incentives. This model simultaneously optimizes the supply chain design, insertion point selection, and production planning. In addition, the conversion rate, operation cost associated with insertion points in petroleum refinery, as well as the biomass availability and product demand are modeled as fuzzy numbers to account for the data uncertainty. A fuzzy possibilistic programming approach is applied to this model, where possibility, necessity and credibility measures are adopted according to the decision makers' preference. This model is illustrated by the county level case study of Illinois. Compared to traditional biofuel supply chains, advanced hydrocarbon biofuel supply chain integrating with existing petroleum refinery infrastructure significantly reduces capital cost and total annualized cost.     

State-of-the-art review of erosion modeling in fluid/solids systems

Erosion in fluidized-bed combustors, commercial process units used to burn coal cleanly, has surfaced as a serious issue that may have adverse economic effects. The evidence suggests that the key to understanding this erosion is detailed knowledge of the coupled and complex phenomena of solids circulation and bubble motion. The FLUFIX computer code has been developed for this purpose. Computed hydrodynamic results compare well with experimental data (including the bubble frequency and size and the time-averaged porosity and pressure distributions) taken in a thin ‘two-dimensional’ rectangular fluidized beds containing a rectangular obstacle and a few-tube approximation of the International Energy Agency Grimethorpe tube bank ‘C1’ configuration.

Six representative erosion models selected from the literature, comprising both single-particle and fluidized-bed models are critiqued. A methodology is described whereby the computed hydrodynamic results can be used with such erosion models. Previous attempts (none involving fluidized beds) to couple fluid mechanics and erosion models are reviewed. The energy dissipation models are developed, and are shown to generalize the so-called power dissipation model used to analyze slurry jet pump erosion. It is demonstrated, by explicitly introducing the force of the particle on the eroding material surface, that impaction and abrasive erosion mechanisms are basically the same. In doing so, it has been possible to unify the entire erosion literature developed for over a century.

Linkage is made to two previously developed single-particle erosion models: Finnie's and Neilson and Gilchrist's. The implementation methodology, which can be applied to any erosion model, be it single-particle or fluidized bed, is summarized. The monolayer energy dissipation (MED) erosion model is developed. The erosion rates computed from the EROSION code are compared with each other and for the cold few-tube approximation of the IEA Grimethorpe tube bank ‘C1’ fluidized-bed experiment, and with other available erosion data literature to validate the calculations. The simplified closed form MED (SCFMED) erosion models and erosion guidelines are developed using semi-empirical correlations in order to allow quick engineering estimates of erosion. Alternative methodologies to couple hydrodynamics and erosion using the kinetic theory of granular flow and discrete element method (DEM) models are briefly reviewed.

Finally, a critical review of the integrated experimental and computational fluid dynamics (CFD) pressurized fluidized-bed hydrodynamics and erosion research ongoing at Chalmers University is presented. This body of work has been influenced by the research at Argonne National Laboratory (ANL) and Illinois Institute of Technology (IIT) and reinforces the trends and conclusions reported in this review.     

High-pressure, high-temperature oxidation of toluene

The high-pressure single pulse shock tube (HPST) at the University of Illinois at Chicago has been used to study the oxidation of toluene at reflected shock pressures from 22 to 550 bar and temperatures from 1210 to 1480 K. Experiments were performed for dilute stoichiometric, Φ=1, and rich, Φ=5, reagent mixtures. Stable species were analyzed using gas chromatography and gas chromatography/mass spectrometry. The resulting data set is the first that provides species concentrations over such extremes of pressure, temperature, and stoichiometry, and it serves as an excellent base for the validation and refinement of future detailed chemical kinetic models. Two literature models for the oxidation of toluene that have been validated against atmospheric pressure turbulent flow reactor and jet stirred reactor data were used to simulate the experimental data. Several modifications were made to one model to more accurately simulate the high-pressure/high-temperature experimental data. The modified model reproduces the Φ=1 experimental data well and forms the first step in the development of a more comprehensive model for toluene combustion validated over wide ranges of temperature and pressure.     

High pressure study of 1,3,5-trimethylbenzene oxidation

The high pressure and high temperature kinetics of the 1,3,5-trimethylbenzene oxidation were investigated in the High Pressure Single Pulse Shock Tube at University of Illinois at Chicago. Experiments were performed at nominal reflected shock pressures of 20 and 50 atm, for three different equivalence ratios (Ф = 0.51, 0.95 and 1.86) and for a temperature range of 1017–1645 K. A variety of stable species ranging from aliphatic hydrocarbons to single ring and polycyclic aromatic hydrocarbons were sampled from the shock tube and analyzed using standard gas chromatographic techniques.A detailed chemical kinetic model was developed to simulate the fuel and oxygen decay and the stable intermediate species profiles as obtained from the high pressure oxidation experiments. The model shows satisfactory predictions for the formation and consumption of most of the major intermediates.     

基于Shapley值的云南省能源消费综合预测方法研究

对未来的能源消费进行准确的预测,既能为能源政策及规划的制定提供科学的依据,也是能源发展战略目标制定的基础性工作.通过指数平滑模型和系统动力学模型分别对云南省能源消费进行预测,进一步运用合作博弈中的Shapley值方法,通过分配总误差来确定综合预测模型中各预测模型的权重,以此构建综合预测模型,并对云南省能源消费总量进行预测.预测结果表明,该综合预测模型的预测精度高于选定的各项预测模型,对能源消费的预测是可行、有效的.