Promises in direct conversion of cellulose and lignocellulosic biomass to chemicals and fuels: Combined solvent–nanocatalysis approach for biorefinary

This review surveys sustainable one-pot conversion methods of cellulose into two very important platform chemicals such as 5-hydroxymethylfurfural and isosorbide retaining applications in many fields. Various new techniques based on such as ionic liquids, acid functionalized mesoporous materials, organic acids, functionalized nanoparticles, and mechanocatalytic depolymerization was discussed in detail for the very important direct conversion of cellulose to 5-hydroxymethylfurfural. More emphasis is given on a comparative analysis of recently developed all successful methods for 5-hydroxymethylfurfural production from cellulose in terms of efficiency, selectivity and cost-effectiveness. The article also complements on the promising extraction methods for the 5-hydroxymethylfurfural using special solvents. The importance of another very interesting platform chemical, i.e. isosorbide is also addressed. Several factors of cellulose to isosorbide transformation including metal nanoparticle size, crystallinity order of the cellulose, and extraction medium which controls the rate of conversion and product distillation have been addressed. The article also surveys the potential discoveries in one-pot conversion of cellulose into biofuels. The strategies of cellulose and lignocellulose conversions to compounds with liquid fuel's features have been discussed focusing on the production of γ-valerolactone as important intermediates to access liquid hydrocarbons and valeric esters. Cellulose value-chain for the direct conversions to liquid fuels (e.g. cellulose to levulinic acid platform to obtain valeric biofuels) by using supported nanostructured metal catalysts are emphasized. Overall an analysis of the main prospects and constraints related to the several conversion routes are presented including the critical thinking on the technical barriers, commercial promise, and environmental issues.     

Annealing of a magnesium alloy AZ31 after interrupted cold deformation

The isothermal annealing behaviors of a magnesium alloy AZ31, deformed by multi-directional forging (MDF) at ambient temperature to cumulative strains ranging from 0.2 to 1.5, was investigated at 473 K. The deformed microstructure is characterized by several types of twins formed in various directions during MDF and their intersections with one another. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) plots of X_rex-t curves are approximated by a linear relationship with an exponent of 2.6 at early stages of annealing irrespective of prior strains, but always break at long times, leading to lower values of the exponent. The non-linear JMAK plots may result from the inhomogeneity of deformed microstructures. The annealing process is composed of new grain formation at the intersections and subsequent large-distance migration of their boundaries, that is discontinuous static recrystallization (dSRX). The annealing characteristics of the cold-deformed Mg alloy are discussed comparing with the contrastive ones of the hot-deformed alloy.     

An ocean thermal energy conversion based system for district cooling,ammonia and power production

In this study, a novel Ocean Thermal Energy Conversion (OTEC) based tri-generation system that produces ammonia, cooling and power is developed and analysed. This OTEC plant operates on the naturally existing temperature difference that exists in various depths of the ocean. The OTEC plant used in this study is operated using a single-stage ammonia Rankine cycle. The discharge seawater from the condenser in the organic Rankine cycle is used to provide district cooling. Two different operation cases of the analysed system are considered, where for the first case 50% of the power produced is stored in the form of ammonia during the off-peak hours. The second case is for complete power production proposed for peak hours. For the case where 50% of the power produced (case 1) is used to produce ammonia the highest energy and exergy efficiency is found to be 1.37% and 56.17% respectively. As for the case where, only power is produced (case 2) the maximum energy and exergy efficiency of the OTEC plant is found to be 1.83% and 78.02% respectively. The corresponding maximum power production was 6612 kW and 13,224 kW for cases 1 and 2. The maximum hydrogen and ammonia production rate is found to be 94.35 kg/h and 534.7 kg/h at peak efficiency values. The cooling duty at the peak energy and exergy efficiency is found to be 64.4 MW where the condenser temperature is 11.38 °C.     

RTDS implementation of an improved sliding mode based inverter controller for PV system

This paper proposes a novel approach for testing dynamics and control aspects of a large scale photovoltaic (PV) system in real time along with resolving design hindrances of controller parameters using Real Time Digital Simulator (RTDS). In general, the harmonic profile of a fast controller has wide distribution due to the large bandwidth of the controller. The major contribution of this paper is that the proposed control strategy gives an improved voltage harmonic profile and distribute it more around the switching frequency along with fast transient response; filter design, thus, becomes easier. The implementation of a control strategy with high bandwidth in small time steps of Real Time Digital Simulator (RTDS) is not straight forward. This paper shows a good methodology for the practitioners to implement such control scheme in RTDS. As a part of the industrial process, the controller parameters are optimized using particle swarm optimization (PSO) technique to improve the low voltage ride through (LVRT) performance under network disturbance. The response surface methodology (RSM) is well adapted to build analytical models for recovery time (R_t), maximum percentage overshoot (MPOS), settling time (T_s), and steady state error (E_ss) of the voltage profile immediate after inverter under disturbance. A systematic approach of controller parameter optimization is detailed. The transient performance of the PSO based optimization method applied to the proposed sliding mode controlled PV inverter is compared with the results from genetic algorithm (GA) based optimization technique. The reported real time implementation challenges and controller optimization procedure are applicable to other control applications in the field of renewable and distributed generation systems.     

Boron- and nitrogen-doped multi-wall carbon nanotubes for gas detection

The response of pristine, nitrogen and boron doped carbon nanotube (CNT) sensors to NO₂, CO, C₂H₄ and H₂O at ppm concentrations was investigated at both room temperature and 150 °C. N-doped CNTs show the best sensitivity to nitrogen dioxide and carbon monoxide, while B-doped CNTs show the best sensitivity to ethylene. All tubes (including undoped) show strong humidity response. Sensing mechanisms are determined via comparison with density functional calculations of gas molecule absorption onto representative defect structures in N and B-doped graphene. N-CNTs show decreased sensitivity with temperature, and detection appears to occur via gas physisorption. B-CNTs appear to react chemically with many of the absorbed species as shown by their poor baseline recovery and increasing sensitivity with temperature. This limits their cyclability. Overall gas sensitivity is as good or better than post-growth functionalised nanotubes, and used in combination, CNTs, N-CNTs and B-CNTs appear highly promising candidates for cheap, low power, room temperature gas sensing applications.     

Optimal planning for industrial park-integrated energy system with hydrogen energy industry chain

Establishing an industrial park-integrated energy system (IN-IES) is an effective way to reduce carbon emission, reduce energy supply cost and improve system flexibility. However, the modeling of hydrogen storage in traditional IN-IES is relatively rough. In order to solve this problem, an IN-IES with hydrogen energy industry chain (HEIC) is proposed in this paper. Hydrogen production, transportation, and storage technologies are applied in HEIC. Firstly, a novel long-term hydrogen storage model considering different time steps is presented. Secondly, hydrogen compressor models considering different pressure ratios are further employed. On this basis, the impact of the HEIC on the planning and operation results of IN-IES is studied. Finally, the superiority and the effectiveness of the proposed model and planning method are verified by simulation cases.