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Hot flue gas evaporation technology is an effective strategy for zero liquid discharge of desulfurization wastewater. However, there is a potential risk that heavy metals such as Hg may be released from the wastewater during evaporation, disrupting the original balance of the power plant or even exceeding the Hg emission standard. Wastewater evaporation and Hg release behavior were obtained using a single droplet drying system. At an evaporation temperature of 300 °C, approximately 18.5% of Hg was released in the constant wet-bulb temperature period, and the remaining was released in the following evaporation periods. Furthermore, a fixed-bed experiment, in combination with density functional theory calculations, was used to investigate the possible migration mechanisms of released Hg. The results revealed that high HCl concentration, introduced fly ash, and precipitated evaporation products play a crucial role in the fate of Hg, and 85.3% of Hg finally turned into less harmful particulate-bound Hg. This study provides a new and effective strategy for evaluating the migration process of pollutants in wastewater treatment. Moreover, it will serve as an essential reference for advanced wastewater treatment and heavy metals control technologies in the future.

This paper presents a new security-constrained multiobjective optimal dispatch (SC-MOOD) framework for an economic and reliable operation of microgrids. The framework is developed based on a computationally effective multiobjective optimization technique, Pareto concavity elimination transformation (PaCcET). The new method considers grid steady-state and dynamic constraints while solving the optimal dispatch in both grid-connected and islanded modes. The constraints consist of power balance, voltage magnitude, line flows, power generation, frequency, and voltage transients. The proposed framework finds the most economic operating solutions to not only minimize the generation cost but also minimize the reliability cost. In this paper, the PaCcET is utilized to solve the SC-MOOD. The PaCcET uses an extraordinary transformation to first transfer all the points from a multiobjective space to a transformed objective space. It then solves a linear combination of transformed objectives using a single-objective optimizer to find all the nondominated points of the original multiobjective space. The performance of the new framework is verified using the simulation results in a microgrid with several distributed energy resources in both grid-connected and islanded modes. The results are then compared with two multiobjective optimization techniques, nondominated sorting genetic algorithm II and multiobjective particle swarm optimization, as two well-known benchmarks.

In this work, the effect of the current-collector structure on the performance of a passive direct methanol fuel cell (DMFC) was investigated. Parallel current-collector (PACC) and other two kinds of perforated current collectors (PECC) were designed, fabricated and tested. The studies were conducted in a passive DMFC with active membrane area of 9 cm2, working at ambient temperature and pressure. Two kinds of methanol solution of 2 M and 4 M were used. Results showed that the PACC as anode current-collector has a positive effect on cell voltage and power. For the cathode current-collector structure, the methanol concentration of 2 M for PECC-2 (higher open ratio 50.27 %) increased performance of DMFC. But the methanol concentration of 4 M led to an enhancement of fuel cell performance that used PACC or PECC-2 as cathode current-collector.

Abstract With the improvement on materials performance gradually reaching its bottleneck, more and more works focus on optimizing the device structures to seek further performance enhancement of thermoelectric (TE) devices. This paper proposed an analytical model to calculate the performance of thermoelectric generators (TEGs) with varied leg cross-sections considering temperature-dependent material properties. The explicit expressions of output power and efficiency are derived and the model is verified by finite element method (FEM). Furthermore, the optimization of leg geometry for higher device performance is performed based on the presented model, the results show that the key to maximum output power is to minimize the leg resistance; and increasing the leg volume may simultaneously raise the output power and efficiency. In addition, we apply the presented model to optimize the leg shape of a commercial TEG module and find that the optimized geometry can simultaneously achieve an enhancement up to 43.1% for output power and 9.67% for efficiency. The presented model thus may be useful in designing high-performance TEGs and shed considerable light on the principles of TEG design.

This study focuses on the preparation of camphene/palmitic acid mixture as novel phase change material for the first step of composite-based phase change materials. Camphene–palmitic acid-based composite phase change materials (PCMs) for thermal energy storage were prepared by vacuum impregnation method. The maximum incorporation percentage for camphene–palmitic into pyroclastic, fly ash, barite and marble powder were found to be 33.09, 55.5, 31.5 and 35.96 %, respectively. The differential scanning calorimetry analysis revealed that the composite PCMs were suitable applicants for building applications in terms of their appropriate phase change temperatures and extensive latent heat values. The SEM results showed that the homogeneity of the samples is good, and according to supporting materials porosity formation is observed. Thermal cycling test indicated that the form-stable composite PCMs have good thermal reliability and chemical stability although they were subjected to 2,000 melting/freezing cycling.

Abstract A waste heat air drying system, including a top closed air drying cycle and a bottom organic Rankine cycle (ORC), is proposed, considering the temperature matches during the humid air sensible heat and latent heat recovery processes. In the top air cycle, the waste heat is used as heat source. In the bottom ORC, the sensible heat and latent heat in the humid air of the top cycle are recovered to generate power and get rid of the moisture. The results showed two key parameters, including the working composition and the evaporating pressure of the bottom ORC, influence thermal matching of the humid air waste heat recovering process, and then on overall energy saving performance of the proposed system significantly. Using the zeotropic mixtures as working fluids of the bottom ORC is a better way with the air relative moisture content lower than 0.2, compared to that of using pure working fluids. While, using the pure working fluid is better with the air relative moisture content over 0.2. The optimal evaporating pressure of the bottom ORC is obtained, to achieve the maximal specific net power output and total thermal efficiency of the drying system.

This paper studies the impact of combining wind generation and dedicated large scale energy storage on the conventional thermal plant mix and the CO2 emissions of a power system. Different strategies are proposed here in order to explore the best operational strategy for the wind and storage system in terms of its effect on the net load. Furthermore, the economic viability of combining wind and large scale storage is studied. The empirical application, using data for the Irish power system, shows that combined wind and storage reduces the participation of mid-merit plants and increases the participation of base-load plants. Moreover, storage negates some of the CO2 emissions reduction of the wind generation. It was also found that the wind and storage output can significantly reduce the variability of the net load under certain operational strategies and the optimal strategy depends on the installed wind capacity. However, in the absence of any supporting mechanism none of the storage devices were economically viable when they were combined with the wind generation on the Irish power system.

For mitigating the urgency of constructing power plant, alleviating supply pressure of power company, electricity scheduling of customers is a very important issue, wherein to promote demand response is a key factor. The demand response is mainly through electricity price publicized by utility company to guide customers in electricity scheduling, and by use of price negotiating mechanism, to reach mutual benefits for both sides of demand and supply. The paper proposes a method of minimizing tariff for customers through changing elastic load use time intervals where customers' electricity use time is divided into inelastic and elastic intervals by electricity use characteristics. In the paper, customer's one day electricity used is assumed to conduct simulation, by genetic algorithm, comparing variations among scheduling and tariff under different electricity use limitation situations. As shown in the results, it is found that through elastic load use time interval changes, minimum tariff objective can be reached, and feasibility of the proposed method is verified.

Abstract Geothermal energy resources are considered to be one of the main contributors to clean, renewable and low-risk energy production. However geothermal power production may result in some greenhouse gas (GHG) emissions. Injection of GHGs into geothermal reservoirs can be used to reduce these emissions, providing reservoir pressure support and possibly improve reservoir permeability. To understand the migration and behavior of injected gases in the reservoir and to forecast gas breakthrough, simulation studies are required. This work investigates the possible impacts of infield reinjection of CO2 in two-phase liquid-dominated geothermal reservoirs using an earlier 3D numerical model of the Wairakei-Tauhara system as a representative case study. Wairakei-Tauhara is an interesting case study as it has been operated with no reinjection for most of its lifetime. The work investigated the impact of various scenarios of separated geothermal water and CO2 reinjection on reservoir sustainability. The breakthrough of CO2 was also monitored since it can result in higher gas production and lower power generation. The modelling results showed that the injection of CO2-water mixture helps to maintain the reservoir's pressure, but, at the same time, it may suppress natural recharge and boiling, which results in reduction of the enthalpy of the produced fluid.