• Energy Research
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Abstract In this paper, a liquid regeneration method by vacuum membrane distillation (VMD) is proposed for the liquid desiccant air conditioning system (LDACs), and the experimental study on this method is carried out. VMD regeneration experiments were carried out with LiCl solution. The effects of temperature, concentration of feed solution, length, number of fiber membranes and vacuum pressure on the membrane flux, mass transfer coefficient, rejection rate and regeneration ability were studied. The results show that the error between experimental and calculation results is reduced from less than 15% to less than 5% by the optimized calculation model. The temperature of feed solution has a great influence on the regeneration performance of VMD, and the regeneration ability of VMD process increases approximately exponentially from about 0.1% to 0.8–1.2% with the increase of regeneration temperature. The VMD regeneration process of LiCl solution is the result of Poiseuille flow and Knudsen diffusion, and Poiseuille flow dominates. Under the same regeneration capacity, the regeneration temperature of 30 wt% LiCl solution is about 7 °C higher than that of 20 wt% LiCl solution, and this temperature difference also increases as the target regeneration amount increases. In order to improve the regeneration effect of high concentration solution, the regeneration temperature can be increased appropriately. The water flux of the membrane decreases with the increase of the length of the membrane. The membrane length of Type1 is 2.1 times longer than Type 2, but regeneration capacity of Type 1 is only 1–1.7 times higher than Type 2. Further, both the water flux and regeneration ability of the solution decrease first and then increase with the increasing number of membranes. Therefore, the reasonable selection of number of fiber membranes can significantly save materials and also improve the regeneration ability.

For artificial irrigation in excess or deficiency, not timely and other shortcomings, the paper expounds the application in agricultural and landscape irrigation system based on the wireless sensor network and single chip computer; at the same time the paper designed system architecture of automatic irrigation system based on wireless sensor network. The hardware of the system adopts CC2430 single chip microcomputer as control core, by the real-time acquisition and processing of data in wireless sensor networks, the control data by wireless way is sent to the irrigation controller. The system can real-time monitor the soil temperature and humidity changes, r realize fine flower required and efficient use of water resources.

Abstract With the implementation of International Maritime Organization's new emission regulations in 2020, it has a huge impact on shipping industry. To meet the strict emission regulations and policies, liquefied natural gas, as a promising fuel, can replace the traditional heavy oil, and effectively and practically act as the main power source of marine engine. When liquefied natural gas is vaporized from −162 °C to room temperature, a large amount of cold energy is released to the outside world. To reuse the cold energy efficiently and economically, a new scheme integrated with organic Rankine cycle, seawater desalination, subzero storage and air-conditioning is proposed through comparison of six solutions. With a series of analysis and comparison, R290, NH3, R32 and R152a are determined as the best working fluids for organic Rankine cycle, subzero storage, seawater desalination and air-conditioning modules, respectively. After optimizing the parameters of the scheme by genetic algorithm, the exergy efficiency, net work and payback period reach 55.91%, 210.3 kW and 4.27 years, respectively, showing excellent thermoeconomic performance. Therefore, the proposed method provides a new idea for cold energy recovery of natural gas engine on ships.

AbstractAs the significant residuals in the sewage treatment system, sludge treatment and reuse play a pivotal impact on the environmental sustainability study in China. In this paper, two sewage sludge treatment systems have been investigated, calculated, and analyzed, including the conventional treatment system (Scenario A) and improved reuse system (Scenario B), respectively. The results demonstrate that (1) Compared to Scenario A, Scenario B is a comprehensive system, which integrates a sewage sludge treatment system and a brick production system for sludge recycling. (2) After considering the brick system (scenario B), on the one hand, the sludge treatment capacity has been enhanced and raised sludge utilization; on the other hand, negative influences have also generated due to the non-renewable resources input and several outputs. (3) In Scenario A and Scenario B, the input resources part reflects the main impact (about 59.6% in the entire emergy value). (4) In this new paper, the UEVs are 2.73E + 11sej/kg and 6.29E + 11sej/kg in Scenario A and Scenario B, respectively. (5) The emergy sustainability indexes (ESI) are 0.012292 and 0.00848, which express the weak comprehensive effects in Scenario A and Scenario B. (6) Scenario B has a more extensive range of change than Scenario A because of the more resource input for the sensitivity analysis. Given the all discussions, there are two effective approaches to be used for perfecting environmental sustainability in the Scenario A system and Scenario B system.

Abstract Photovoltaic-electrodialysis (PV-ED) regeneration is a novel method for liquid desiccant cooling system (LDCS), which has a higher performance than the conventional thermal regeneration method by using solar photovoltaic components to drive an electrodialysis regeneration process. However, there are many defects in the previous proposed single-stage PV-ED system. In this paper, a new double-stage photovoltaic/thermal ED regeneration system is presented. Analysis of the performances of the single-stage and double-stage regeneration system is made and the influential factors are investigated. It reveals that the double-stage PVT-ED regeneration system is more applicable than the single-stage PV-ED regeneration system for liquid desiccant cooling system. Moreover, comparisons between the single-stage system and the double-stage system show that the double-stage system is more energy efficient than the single-stage system under the optimized working conditions.

Lake Qinghai has shrunk and then expanded over the past few decades. Quantifying the contributions of climate change and human activities to lake variation is important for water resource management and adaptation to climate change. In this study, we calculated the water volume change of Lake Qinghai, analyzed the climate and land use changes in Lake Qinghai catchment, and distinguished the contributions of climate change and local human activities to water volume change. The results showed that lake water volume decreased by 9.48 km3 from 1975 to 2004 and increased by 15.18 km3 from 2005 to 2020. The climate in Lake Qinghai catchment is becoming warmer and more pluvial, and the changes in land use have been minimal. Based on the Soil and Water Assessment Tool (SWAT), land use change, climate change and interaction effect of them contributed to 7.46%, 93.13% and −0.59%, respectively, on the variation in surface runoff into the lake. From the perspective of the water balance, we calculated the proportion of each component flowing into and out of the lake and found that the contribution of climate change to lake water volume change was 97.55%, while the local human activities contribution was only 2.45%. Thus, climate change had the dominant impact on water volume change in Lake Qinghai.

Abstract Electrodialysis (ED) is an alternative to the conventional thermal regeneration of high-salt solutions used in air conditioning systems (ACSs). In this work, a simplified mathematical model was developed to describe the solute and water transport. The solute hydration number and free water content were proposed to characterize the solute hydration properties. A laboratory-scale ED regeneration system was set up to investigate the regeneration performance of three kinds of high-salt solutions (aqueous LiCl, LiBr and CaCl2 solutions) at various initial concentrations and current densities. The results demonstrate good agreement between numerical and experimental findings. The initial concentration and applied current density have great impacts on ED performance. Firstly, higher initial concentration generally results in lower membrane permselectivity, current efficiency, solute and water transfer rate, and higher energy consumption. Secondly, higher current density has a positive effect on solute and water transport but leads to more energy consumption. The solute hydration number and free water content both decrease with increasing initial concentration. The appropriate mass concentrations of 15%, 25% and 15% are respectively suggested for aqueous LiCl, LiBr and CaCl2 solutions when applying ED in ACSs to ensure responsible performance.

Abstract This study was targeted on investigating the facilitations of the combined pretreatment of acid washing and torrefaction on the co-production of syngas and phenols-rich bio-oil. Comparison of raw and modified samples indicated that combined pretreatments not only effectively removed the bulk of alkali and alkaline earth metals but also improved the fuel properties by decomposing unstable hemicellulose. Then, via the catalytic reforming of activated carbon catalyst, CO-rich syngas and phenols-rich bio-oil were obtained simultaneously. The optimal products was acquired from the acid-washed sample which torrefied at 240 °C (labeled as AT240). This syngas contained the maximal CO concentration of 61.86%, and its yield reached 174.34 mL/g. In bio-oil, relative content of phenolic compounds was 91.44%, in which the phenol occupied 71.72%. Quantitative analysis revealed the quantity of phenol in AT240 was 1.74 times of raw bio-oil. Furthermore, mechanism of combined pretreatment on catalytic co-production of syngas and phenols was proposed and discussed in this paper

In order to analyse the influences of substrate and electrode on the performance of microbial fuel cell-coupled constructed wetland (CW-MFC), the electrical generation efficiencies, the decolourization mechanism of reactive brilliant red X-3B, and the microbial communities in the anode were investigated. The closed circuit reactor fed with a mixture of X-3B and glucose (166.7 mg/L X-3B and 140 mg/L glucose) (the mixture CC reactor) got a decolourization rate of 92.79%, which was higher than the open circuit reactor (the mixture OC reactor) and the reactor fed with X-3B (the X-3B reactor). The mixture CC reactor got a maximum power density of 0.200 W/m(3), which was much higher than the X-3B reactor. The intermediates produced by X-3B decolourization were further degraded in CW-MCs. The PCR-denatured gradient gel electrophoresis analysis indicated the dominance of Proteobacteria-like 16S rRNA gnen sequences. The brightest band was detected to be dominant by a Lactobacillus kefiranofaciens-like sequence. The electrogenic bacteria-associated sequences, such as Geobacter metallireducens and Desulfobulbaceae, both existed in the closed circuit and the open circuit reactors, accompanied with Desulfobacterium sp., Klebsiella sp., Aminobacter sp., Flavobacterium sp., Thauera aromatic, and Sphingomonas sp. The abundances of Geobacter sulfurreducens and Betaproteobacteria in the mixture CC reactor were 32.2% and 7.2%, respectively, and were higher than those in the mixture OC reactor. In summary, substrate and electrode can promote the performance of the CW-MFC and have effects on the microbial community in the anode of the CW-MFC.