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Abstract The future of urban energy systems relies on the transition to “smart energy networks” which incorporate energy storage with renewable energy sources such as wind and solar. Hydrogen provides a desirable energy vector for both energy storage and exchange of energy between energy hubs within a smart energy network. This paper aims to develop a generic mathematical model for the optimal energy management of future communities where hydrogen is used as an energy vector. An energy hub is a novel concept that systematically and holistically considers the energy requirements of both mobility and stationary loads. In order to perform optimization studies, the minimization of capital cost of hydrogen refueling stations and operation and maintenance cost of all energy hubs within the network are considered. The modeling and optimization are undertaken and carried out in the General Algebraic Modeling Software (GAMS). The case study considers four energy hubs consisting of a commercial building, school, residential complex, as well as hydrogen refueling stations. The study investigates the optimal operation of different energy conversion and storage technologies in order to meet the demand of energy. The results showed that the optimum size of electrolyser and hydrogen tank for supplying the hydrogen demand in the energy hub network is two 290-kW electrolysers and four 30-kg tanks, respectively. The average daily strike price of electricity by which the electrolyser operates is $0.036 per kWh and will not operate when the average hourly Ontario electricity price is higher than $0.13 per kWh. The levelized cost of hydrogen produced by hydrogen refueling station is estimated to be $6.74 per kg. Moreover, the optimal operation of energy conversion and energy storage technologies within each hub and the optimal interaction between energy hubs with in the network are also investigated. In addition, it is shown that distributed hydrogen generation is more preferable than H2 delivery in environmental and economic comparison.

Self-thinning theory predicts that decline in density with increasing individual mass should match the exponent of the metabolism–body mass relationship (∼0.9 in salmonids). However, self-thinning assumes energy equivalence (constant energy available to a cohort as it ages), which may be unrealistic for mobile taxa. I evaluate this assumption using a bioenergetic–stream habitat model to assess the sensitivity of available energy and self-thinning slopes to changes in habitat structure (percent pool). Self-thinning slopes across three age-classes of juvenile trout (young of the year, 1+, and 2+) were sensitive to both modelled habitat structure and density-independent mortality rates. Density-independent overwinter mortality generated self-thinning curves similar to those expected from metabolic allometry, even without habitat limitation (density-dependent mortality). Energy available to sympatric cohorts was unequal under most habitat configurations because of size-based differences in swimming performance that affected habitat availability and interference competition (dominance) that allowed resource monopolization by older cohorts. The optimal habitat structure that maximized abundance of the 2+ age-class (and best approximated energy equivalence) was ∼40% pool, but this value was sensitive to density-independent mortality rate and assumptions about the effect of the pool to riffle ratio on invertebrate prey production.

Abstract In this work, the beneficial effect of carbocation scavenger additives on hardwood pretreatment was revealed by significantly improved biomass saccharification: cellulose hydrolysis yield was increased by over 15% after steam pretreatment of poplar, while that was enhanced by more than 48% after dilute acid pretreatment. Besides, the relative contributions of lignin towards enzyme binding and physical barrier effect for proposed mechanisms were quantified. Results indicated that the addition of carbocation scavenger, 2-naphthol-7-sulfonate, resulted in acid groups incorporation of 62.36 mmol/kg to lignin, which mitigated enzyme non-productive binding. Moreover, enlarged biomass porosity and reduced surface lignin coverage were detected through BET and XPS analysis, respectively, which mostly related to the diminished physical barrier effect of lignin. As a result, the lignin inhibitions were significantly suppressed through the addition of carbocation scavenger, giving rise to significantly improved enzymatic hydrolysis of hardwood.

Several rural farms have installed anaerobic digestion systems as manure management systems. Such systems are also used to provide electricity and heating. In these systems, biogas is generated from anaerobic digestion of biomass waste and combusted in a boiler and an engine-generator set, to produce heat and electricity respectively. This paper calculates the size and mode of operation of a biomass waste to energy conversion system that would result in maximum revenue for a given herd size. A Tabu Search optimisation technique is used. A number of equally good solutions are generated. These solutions are plotted on a Pareto front and the best solution is defined as one that lies on this Pareto front. Optimisation of a biomass waste to energy conversion system reduces reliance on electricity from the grid. It also reduces reliance on the use of propane or other fossil fuels for heating.

We consider the energy-efficient transmission of traffics with hard delay constraint over wireless ad hoc networks. We adopt a cross-layer design approach and develop a route configuration method such that the average energy cost for packet delivery is minimized while maintaining the required delivery ratio. In particular, we allow the intermediate nodes to drop a packet when the node has performed certain number of unsuccessful retransmissions. Based on the physical channel state information, we formulate and solve an optimization problem to jointly configure the transmitting power for each transmitting node and the retransmission limit over each hop. The resulting route configuration solution achieves minimum energy consumption for message delivery while guaranteeing an acceptable quality of service (QoS) level. Numerical results demonstrate the effectiveness and efficiency of our route configuration algorithm regarding both energy saving and statistical QoS guarantee.

Abstract The paper reports the development of a computer program that solves the thermal energy exchange and pressure drop characteristics for bayonet-element heat exchangers. The prime motivation for the study was to aid the design of a heat exchanger for the externally-fired combined cycle (EFCC) energy generation process. The essential feature of this high-efficiency process is the CMC (ceramic matrix composite) bayonet-tube gas–gas heat exchanger for use with shell-side temperatures up to 1600°C. It is envisaged that similar heat exchangers can be designed for applications in the metallic extraction and production industries. The program, named COHEX (composite heat exchanger), solves the basic governing equations of the exchanger. It makes use of a numerical iterative approach from an initial tube-side outlet temperature estimate to converge to a solution. For given inlet conditions, the program evaluates the heat transfer between the shell-side and tube-side streams and arrives at the outlet conditions. This two-part paper presents a computational solution method using accepted techniques for conduction, convection and radiation in the high temperature heat exchanger. Part A addresses the technological background of the EFCC application and the theoretical content of COHEX in terms of accuracy and sophistication of the code. The second part of this paper reported here, part B, describes the experimental facilities used to gather data in order to validate the program output. A comparison of computed and experimental data is presented. The paper progresses to illustrate the effects of parameter variation on heat exchanger output.

Abstract Significantly higher efficiencies for 129I measurement by Accelerator Mass Spectrometry (AMS) would be possible if 129I3+ ions could be counted at terminal voltages as low as 1 MV. However, at M/Q = 3, the molecular interference was anticipated to be severe; this has prevented the use of charge 3+ from being adequately considered. Instead, charge 5+ has been used at higher terminal voltages because of the minimal interference. During a recent performance assessment with charge state 3+, a background of 129I/127I ≈ 10−14 was readily obtained and few 86Sr2+ and 43Ca1+ ions were encountered. This surprising result is possibly due to the very low binding energy and consequent poor stability of anions such as CaSr− and Ca 3 - . Some triply charged molecular ions were found in the energy spectrum at lower stripping gas pressure but their interference with the detection of 129I3+ was readily suppressed with the Ar gas stripper operated at normal thickness. It now appears that as long as the prepared AMS samples are of good chemical purity, the molecular fragments can be expected to remain quite low in intensity and readily resolved by the final detector. As a result, charge state 3+ can be used for 129I measurements at lower terminal voltages with higher overall efficiency.

Mode of operation, designs of pressure vessels, and the manufacturers of commercial and pilot HPP equipment are reviewed in this chapter. The range of available and new commercial HPP machines for different groups of food producers is presented. The process economics, energy requirements along with the considerations on how to select the HPP unit are discussed.

Abstract A series of five amorphous fluorinated alumina catalysts ( F Al ratios between 0–3) was investigated with respect to their potential to convert acetylene to high-octane fuel components. Tests were performed in a tubular flow reactor at 1 atm. The effects of temperature (573–673 K), space velocity (1200–3600 h−1), and initial concentration of acetylene (5–15%) on catalyst activity were examined. Catalyst performance was also correlated with the acidity of the five catalysts.

A statistically designed set of experiments was run in a continuous downflow fixed-bed reactor to evaluate the intrinsic kinetics of the formation of methanol, higher alcohols, total hydrocarbon, and carbon dioxide from synthesis gas under a range of experimental conditions. To eliminate mass-transfer resistance, a multiwalled carbon nanotube (MWCNT)-supported K-promoted trimetallic sulfided Co−Rh−Mo catalyst was used in the particle size range of 147−210 μm. To predict the reaction rate for higher alcohol synthesis, the power law model was used for the reaction between CO and H2 on the catalyst surface. The operating conditions, such as reactor temperature (T), pressure (P), gas hourly space velocity (GHSV), and H2/CO molar ratio, were varied in the ranges of 275−350 °C, 800−1400 psig (5.52−9.65 MPa), 2.4−4.2 m3 standard temperature and pressure (STP) (kg of catalyst)−1 h−1, and 0.5−2.0, respectively. The data of this study are well-fitted by the power law model. The activation energies of ethanol and hi...