• Energy Research
• Closed Access close
• Embargo close
• Chinese Academy of Sciences close

The influence of elemental sulfur (S(0)) amendment on methylmercury (MeHg) accumulation in rice and the chemical form of Hg in the rhizosphere were investigated under waterlogged conditions in Hg-contaminated soil (the majority of the Hg (˜70%) in forms similar to HgS). Different levels of S(0) addition increased the MeHg accumulation in rice. After a sequential extraction analysis of the chemical forms of Hg in the rhizosphere, the results showed that S(0) addition increased the organic bound Hg and decreased the residual Hg in the soils. An Hg LIII XANES further showed that S(0) addition increased the proportion of Hg in the form of RS-Hg-SR and decreased the proportion of Hg in the form of HgS, indicating that S(0) input may reactivate the non-bioavailable Hg in the rhizosphere and improve the net Hg methylation. These findings suggest that the application of S fertilizers to Hg-contaminated paddy soils may increase the MeHg concentration in the edible parts of crops, which may lead to more potential health problems in humans depending on the crop type. However, our study also suggests that S(0) addition could be an effective measure for mobilizing the insoluble Hg and accelerating the phytoremediation process in Hg-contaminated paddy soils.

Abstract The slag behaviors on the bottom cone are crucial characteristics that relate to the slag blockage in a gasifier. The slag flow and heat transfer model on the bottom cone was built to calculate the slag flow velocity, slag thickness and heat flux density. The results shown the slag flow velocity decreased and the slag thickness increased with the increasing cone angle. The slag heat flux density decreased with the increasing cone angle, and specially, the heat transfer rate of the overall bottom cone decreased significantly with the increasing cone angle. The flow slag residence time model was established to calculate the residence time distribution (RTD) of molten slag, and the results shown the mean residence time decreased with the increasing cone angle. In addition, this study preliminary analyzed the blockage possibility, and the results shown the slag thickness was significantly influenced by the critical temperature interval.

Abstract Investigation of natural convection heat transfer enhancement and entropy generation of nano liquid-metal fluid in a differentially heated cavity is carried out for three types of nanofluids, copper-Ga (Cu Ga), diamond-Ga (Diam-Ga) and carbon nanotubes-Ga (CNT Ga), in which Grashof number varies from 104 to 106 and nanoparticles volume fraction from 0.01 to 0.15. The nanofluid flow is simulated by the two-phase mixture model. The studied results show that the convective intensity, heat transfer and local entropy generation increase with the increase of Grashof number. The average Nusselt number of nano liquid-metal fluid increases monotonically with increasing of Grashof number and nanoparticles volume fraction, and the total entropy generation also increases monotonically. The heat transfer performance of CNT-Ga is the highest, that of Diam-Ga is the second and the Cu Ga is the lowest.

Abstract The mesophase pitch derived graphite foams with low bulk density (L-GF) and high bulk density (H-GF) were spontaneously infiltrated by erythritol to prepare graphite foam/erythritol (GF/erythritol) phase change materials (PCMs) with ultrahigh thermal conductivity for medium temperature thermal energy storage applications. Results of thermophysical properties indicated that thermal diffusivity of the GF/erythritol PCMs can be enhanced by 66 and 117 times as compared with that of pristine erythritol in solid (0.36 mm2/s). This enhancement resulting from three-dimensional ordered network of graphite foam can significantly reduce the charging and discharging time of the PCM storage system. Although H-GF as a matrix can obtain a higher thermal conductivity (68.71 W/(m·K)) than L-GF (40.52 W/(m·K)), the smaller porosity cannot allow more erythritol to be absorbed, and its melting enthalpy (178.4 J/g) is lower than L-GF (266.6 J/g). In addition, the enhancement of thermal conductivity and the increase of interfacial surface area caused by graphite foam structure strongly suppresses the supercooling of erythritol, which can be reduced from 86.0 °C to 53.2 °C. The obtained results demonstrated that the GF/erythritol PCM as a stable PCM is a promising material for medium temperature thermal energy storage applications.

Abstract Algae have been considered as a promising biodiesel feedstock. One of the major factors affecting large-scale algae technology application is poor wintering cultivation performance. In this study, an integrated approach is investigated combining freshwater microalgae Chlorella zofingiensis wintering cultivation in pilot-scale photobioreactors with artificial wastewater treatment. Mixotrophic culture with the addition of acetic acid (pH-regulation group) and autotrophic culture (control group) were designed, and the characteristics of algal growth, lipid and biodiesel production, and nitrogen and phosphate removal were examined. The results showed that, by using acetic acid three times per day to regulate pH at between 6.8 and 7.2, the total nitrogen (TN) and total phosphate (TP) removal could be increased from 45.2% to 73.5% and from 92.2% to 100%, respectively. Higher biomass productivity of 66.94 mg L−1 day−1 with specific growth rate of 0.260 day−1 was achieved in the pH-regulation group. The lipid content was much higher when using acetic acid to regulate pH, and the relative lipid productivity reached 37.48 mg L−1 day−1. The biodiesel yield in the pH-regulated group was 19.44% of dry weight, with 16–18 carbons as the most abundant composition for fatty acid methyl esters. The findings of the study prove that pH adjustment using acetic acid is efficient in cultivating C. zofingiensis in wastewater in winter for biodiesel production and nutrient reduction.

Abstract Oil-related events have increased the uncertainty and complexity of the worldwide oil market. This paper investigates the effects of four types of oil-related events on world oil prices, using an event study methodology and an AR-GARCH model. The Internet information concerning these events, which is derived from search query volumes in Google, is introduced in an analytical framework to identify the magnitude and significance of the market response to oil-related events. The results indicate that world oil prices responding to different oil-related events display obvious differentiation. The cumulative abnormal returns, which reflect the influence of the global financial crisis, tend to drop first and then reverse and rise, while the cumulative abnormal returns induced by other oil-related events present a stronger persistent effect. The impact of the global financial crisis on oil price returns is significantly negative, while the impact of the Libyan war and hurricanes is significantly positive. However, the reactions of oil price returns to different OPEC production announcements are inconsistent.

Abstract During the start-up or operation of pool type lead cooled fast reactor, it is probable that loss of flow transient appears from forced circulation or mass flow rate less than that during forced circulation, due to any flow blockage, station blackout or pump malfunction. In this type of scenario temperature distribution and movement of thermal stratification layer will be different from that during loss of flow transient from forced circulation. Computational fluid dynamics (CFD) transient analysis of three-dimensional model of CLEAR-S was performed in this research with the use of commercial code FLUENT to analyze the influence of initial coolant mass flow rate on flow and coolant temperature profile in different constituents of engineering validation facility (CLEAR-S) during loss of flow transient. Firstly, steady state was simulated at mass flow rate equal to 100%, 50% and 25% of the rated mass flow rate respectively. Than loss of flow transient was simulated after started from the steady state of 100%, 50% and 25% of the rated mass flow rate as t = 0sec respectively to understand the movement and temperature distribution of thermal stratification within the pools of CLEAR-S. Results showed that after loss of flow transient from 100%, 50% and 25% mass flow rate, LBE in the hot pool was distributed into five to six layers of different temperatures and temperature of LBE on both sides of stratification layer increased with the decrease of initial mass flow rate. As time progressed hot pool stratification layer proceeded upward and width of top most layer of LBE with high temperature reduced which ultimately vanished after giving birth to a new layer at hot pool bottom. Stratification initiated from DHR outlet in the cold pool after loss of flow transient from 100% mass flow rate. Thermal stratification was observed to be started at heat exchanger (HX) outlet during loss of flow transient initiated form 50% and 25% of mass flow rate. Temperature of LBE on both sides of stratification layer increased with the decrease of initial cold pool mass flow rate of CLEAR-S. With the proceeding of time Stratification layer raised upward and top most layer vanished.

Abstract Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.

Abstract In order to maximize the operation profit while maintaining the service quality, an effective energy management scheme is highly needed for the Photovoltaic-assisted Charging Station (PVCS). Considering the uncertainty of Electric Vehicle (EV) charging demand and PV power output, it will be challenging to determine the charging power for EVs to make informed real-time decisions. In this study, an online energy management method leveraging both offline optimization and online learning is proposed. In order to maximize the self-consumption of Photovoltaic (PV) energy and decide the power supplied from the power grid with Time-of-Use (TOU) pricing, here online learning is coupled with the rule-based decision-making to obtain a real-time online algorithm. The knowledge base for online learning is derived and updated from the results of offline optimization after every operation day. The PVCS located at workplace parking lots is used as an example to test the proposed method. The simulation results show that the method can be implemented without the information on future PV power and charging demand. The obtained results are close to the optimal results from offline optimization.