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Abstract Important aspects of electricity system planning are overall yearly electricity consumption and information about variations in consumption. These variations will influence the capacity that has to be installed, as well as the type and quantity of fuel that will be used. Using only economic, socio-economic, technical and meteorological indicators, we have developed a model that can predict the hourly load shape. This model is based on a division of the total electricity-consumption into 60 economic sectors and electrical appliances. For each of these sectors, a load shape is formed. Summation over sectors then gives the total hourly electricity consumption pattern. To test this model, the hour-to-hour load shape of the Dutch public grid for 1980 was formulated and compared with the actual load shape. The root-mean-square difference between the estimated and actual load shapes is 5% of the mean hourly load. The accuracy of the estimated maximum load for every week is of the same magnitude as that used for electricity-supply system planning over the short term. We conclude that our model can be used for long-term load shape forecasting.

Abstract Energy storage has the potential to reduce the fuel consumption of ships by loading the engine(s) more efficiently. The exact effect of on-board energy storage depends on the ship functions, the configuration of the on-board power system and the energy management strategy. Previous research in this area consists of detailed modelling, design, and comparisons of specific on-board power systems for explicitly defined operational profiles. The necessary inputs for these studies are rarely known initially however, since the effect of energy storage on the fuel consumption is not necessarily always positive, it is essential to know the limitations of fuel savings obtained by an on-board energy storage early in the design stage. To that effect, the paper proposes a set of algebraic formulas for the equivalent specific fuel consumption of on-board power systems equipped with electrical energy storage, which give a quick estimation of the maximum fuel savings obtainable. Depending on the specific fuel consumption of the prime mover, the loading point of the system and the use scenario of the battery, relative efficiency improvements can vary between −48% and 57%. A set of design guidelines is also proposed based on the obtained results.

This research was performed to study the anode reaction in a molten carbonate fuel cell. Chronoamperometry experiments and impedance measurements were carried out at gold and nickel flag-type electrodes in a 62 mole percent (m/o) Li{sub 2}CO{sub 3}/38 m/o K{sub 2}CO{sub 3} eutectic carbonate mixture at 923 K as a function of gas composition (H{sub 2}/CO{sub 2}/H{sub 2}O), and as a function of temperature between 823 and 1073 K. The i {minus} {radical}t extrapolation technique, generally applied to evaluate chronoamperometry results, is shown to yield systematic errors for the hydrogen oxidation studies in molten carbonates. A direct fit of the Gerischer-Vielstich relation yields more reliable results for gold. The current responses on Ni cannot be described by the Gerischer-Vielstich relation. The high reaction orders for hydrogen (0.7 to 1.0), medium for carbon dioxide (order 0.5), and the low or even negative reaction order for water (0 to {minus}0.25), indicate the hydrogen oxidation follows a Volmer-Heyrovsky-type mechanism on gold flag electrodes. The reaction rate at a nickel electrodes was found to be too high to be studied accurately using impedance measurements and chronoamperometry on flag electrodes. In spite of the poor accuracy reaction orders indicate that a final chemical reaction ismore » the rate-determining step in the reaction mechanism on nickel. The activation energy for the exchange current density was found to be in the order of 80 kJ/mol with a tendency to be higher for the gases richer in hydrogen. The activation energy for the Warburg coefficient (diffusion) was found to be about {minus}15 kJ/mol.« less

Nedstack manufactures and commercialises PEM fuel cell stacks for a wide variety of applications, from backup power to transportation, with more than 1000 PEM fuel cell stacks sold. The company also has extensive system integration experience, including the installation and operation of a 70 kW power plant at a chlor-alkali factory in the Netherlands, and a 1 MW unit in operation at a Solvay chemical plant in Belgium.

Abstract Knowledge of flame responses to acoustic perturbations is of utmost importance to predict thermoacoustic instabilities in gas turbine combustors. However, measuring transfer functions linking acoustic quantities upstream and downstream of flames is very challenging in practical systems and these measurements can significantly deviate from state-of-the-art models. Moreover, there is a lack of studies investigating the effect of hydrogen enrichment on the response of natural gas (NG) flames. In this work, measurements of flame transfer matrices (FTM) of turbulent H2/NG flames in an atmospheric combustor featuring an axial swirler burner have been performed, allowing us to unravel the transition between FTM in fully premixed (FP) and in technically premixed (TP) conditions. Furthermore, imaging of OH* chemiluminescence and OH-Planar Laser Induced Fluorescence are obtained for characterizing the topology of the flame for varying H2 fraction and mixing conditions. Transfer matrices are measured using the multi-microphone method for H2 fractions ranging from 12% to 43% in power. Afterwards, the flame transfer functions (FTF), which linearly relate the coherent fluctuations of the heat release rate to the acoustic velocity oscillations, are obtained from the FTM by using the Rankine-Hugoniot jump conditions across the flame. Using the OH* chemiluminescence intensity as a surrogate for the heat release rate, the FTF based on this optical measurement is also extracted and compared to the one exclusively obtained with the multi-microphone method. As expected, the two different methods are in very good agreement for the FP case and significantly differ for the TP case. Indeed, chemiluminescence fluctuations cannot be directly linked to heat release rate fluctuations when the acoustic forcing induces equivalence ratio fluctuations at the flame, making the optical method unusable for TP configurations. We also show that the two methods agree in the high end of the explored excitation frequency range and we provide an explanation to this intriguing finding. Moreover, we investigate the sensitivity of the FTM measurement to the estimate of the speed of sound in the rig in FP conditions. Finally, the measured FTFs are fitted with FTF models based on multiple distributed time delays. This allows us to explain the frequency dependence and the hydrogen fraction dependence of the gain and the phase in FP and TP conditions.

This study presents the clockspeed analysis of a peer group comprising six major integrated US energy companies with substantial US interstate natural gas pipeline business activities: El Paso, Williams, NiSource, Kinder Morgan, MidAmerican and CMS Energy. For this peer group, the three clockspeed accelerators have been benchmarked at both corporate level and gas transmission business level, using time-series analysis and cross-sectional analysis over a 6-year period (2002–2007). The results are visualized in so-called clockspeed radargraphs. Overall corporate clockspeed winners – over the performance period studied – are: Williams, El Paso and Kinder Morgan; MidAmerican is a close follower. Corporate clockspeed laggards are: CMS Energy and NiSource. The peer group ranking for the natural gas transmission business segment shows similar clockspeed winners, but with different ranking in the following order: Kinder Morgan, MidAmerican and El Paso; Williams is a close follower. Clockspeed laggards for the natural gas transmission segments coincide with the corporate clockspeed laggards of the peer group: CMS Energy and NiSource (over the performance period studied); laggards of the past may become clockspeed leaders of the future if adjustments are made. Practical recommendations are formulated for achieving competitive clockspeed optimization in the US gas transmission industry as a whole. Recommendations for clockspeed acceleration at individual companies are also given. Although the US natural gas market is subject to specific regulations and its own geographical dynamics, this study also provides hints for improving the competitive clockspeed performance of gas transmission companies elsewhere, in other world regions.

Psychrophilic anaerobic treatment is an attractive option for wastewaters that are discharged at moderate to low temperature. The expanded granular sludge bed (EGSB) reactor has been shown to be a feasible system for anaerobic treatment of mainly soluble and pre-acidified wastewater at temperatures of 5--10 degrees C. An organic loading rate (OLR) of 10--12 kg chemical oxygen demand (COD) per cubic meter reactor per day can be achieved at 10--12 degrees C with a removal efficiency of 90%. Further improvement might be obtained by a two-module system in series. Stabile methanogenesis was observed at temperatures as low as 4--5 degrees C. The specific activity of the mesophilic granular sludge was improved under psychrophilic conditions, which indicates that there was growth and enrichment of methanogens and acetogens in the anaerobic system. Anaerobic sewage treatment is a real challenge in moderate climates because sewage belongs to the 'complex' wastewater category and contains a high fraction of particulate COD. A two-step system consisting of either an anaerobic up-flow sludge bed (UASB) reactor combined with an EGSB reactor or an anaerobic filter (AF) combined with an anaerobic hybrid reactor (AH) is successful for anaerobic treatment of sewage at 13 degrees C with a total COD removal efficiency of 50% and 70%, respectively.

Abstract Climate change is a major challenge for the energy sector, particularly for wind energy onshore and offshore. Climate models are the only tool which is able to produce physical-based projections of future changes in response to increasing greenhouse gas emissions. In the present study, the Western Iberian offshore wind resource is analysed for present and future climates, using a set of regional climate models (RCMs) simulations produced in the framework of the CORDEX experiment at 0.11° resolution (∼12 km), and a regional climate simulation produced with the WRF model at higher resolution (9 km). All these simulations are firstly, evaluated against wind buoy measurements and Cross-Calibrated Multi-Platform (CCMP) wind data, and used to generate two high quality multi-model ensembles based on the individual model’s performance. The results of the WRF simulation and of the two multi-model ensembles are then used to describe the wind resource both for the present and future climates, according to the RCP4.5 and RCP8.5 emission scenarios. This allows the assessment of the climate change signal on the offshore wind and to provide an uncertainty measure of these projections. The vast majority of climate models project reductions of wind speed and wind power for all seasons, with the exception of summer. For the RCP8.5 emission scenario the multi-model ensembles project reductions in power density of around 7% for winter, 4% for spring and 12% for autumn, and increases of 5% for summer. In the latter, and increase up to 20% in power density is forecasted for the Iberian northwest coast. This is sufficient to offset the yearly balance, in as much as no change is expected at a yearly scale for this area. For the remaining west Iberian coast, a yearly reduction of less than 5% is estimated. These results are shared by the two multi-model ensembles and by WRF higher resolution simulation (9 km). The projected changes have the consequence of reducing the annual cycle of power density availability and of its yearly mean values. Finally, for the less aggressive scenario, RCP4.5, the changes have the same signal but with smaller values.

Global emission inventories with 1°x 1°resolution were compiled for nitrogen oxides (NO + NO2, together denoted as NO(x)), ammonia (NH3) and nitrous oxide (N2O) emissions. For NO(x) the estimated global anthropogenic emission for 1990 is about 31 million ton N year-1. The major anthropogenic sources identified include fossil fuel combustion (70%, of which the major sources are road transport and power plants) and biomass burning (20%). Natural sources contribute about 19 million ton N year-1, mainly lightning and soil processes. For NH3the estimated global emission for 1990 is about 54 million ton N year-1. The major sources identified include excreta from domestic animals and wild animals, use of synthetic N fertilisers, oceans and biomass burning. About half of the global emission comes from Asia, and about 70% is related to food production. For N2O the major sources considered include fertilised arable land, animal excreta, soils under natural vegetation, oceans, and biomass burning. The global source of N2O is about 15 million ton N2O-N year-1of which about 30% is related to food production. All three inventories are available on a sectoral basis on a 1°x 1°grid for input to global atmospheric models and on a regional/country basis for policy analysis.