Source reduction or process control of fuel-N conversion into reactive NOx precursors (NH3 and HCN) during pyrolysis process was fundamental and essential for clean thermal utilization of straw wastes. In this study, three typical straw wastes (bean, rice and wheat) were employed to probe formation characteristics and regulatory mechanisms of two target NOx precursors via stage pyrolysis method with the help of XPS and chemical absorption-spectrophotometry analytic techniques. Results demonstrated that consistent formation pathways of NOx precursors were elucidated by direct and indirect conversion of similar fuel-N types – amide-N/amine-N/amino-N (N-A) in straw wastes. Specifically, two NOx precursors were hardly linked with primary pyrolysis of N-A types (direct conversion) while dominantly determined by secondary reactions of subsequent nitrogen intermediates in chars and tars (indirect conversion); secondary reactions referring to hydrogenation of heterocyclic-N in chars and dehydrogenation of amine-N in tars were more responsible for NH3-N and HCN-N, respectively, leading to a maximal total yield of 45-50 wt.%. Consequently, compared to single-stage pyrolysis uniformly, two-stage pyrolysis could manipulate intensities of formation pathways at different pyrolysis stages through employing differential intermediate feedstocks for re-pyrolysis, minimizing the ratio of total yield by about 60 % with a greater effect on HCN-N yield (76-83 %) than NH3-N yield (44-50 %), which exhibited an excellent regulatory capacity on NOx precursors formation for straw wastes. These findings were favorable for developing some insights into emission control of N-containing gaseous pollutants during their thermo-chemical conversion processes.
This study deals with the investigating of the potential of employing two energy storage technologies., i.e. battery storage and pumped hydro storage (PHS), for PV powered supply system on a small island in Sweden. The optimal design of two hybrid PV-Battery and PV-PHS systems are compared and analyzed. Genetic Algorithm (NSGA-II) is employed as the optimization algorithm. Investment cost and loss of power supply probability are considered as objective functions. Number of PV modules and battery capacity are considered as design variables for PV-Battery system and a wide range of design variables including number of PV modules, turbine capacity, pump capacity, volume, installation height and depth to diameter ratio of reservoir, pipes diameters constitute for PV-PHS system. As a result, a hybrid pareto front is proposed for case study, that means, regarding objective functions, designer can decide that which of two systems are more suitable for current case study. The results show that pareto fronts of two hybrid systems intersect each other at a point. In this case, PV-PHS led to the lower pareto front for LPSPs up to about 6.94% and for LPSPs higher than 6.94%, pareto front of PV-PHS system lies above that of PVBattery system. This implies that under LPSPs range of 0- 6.94%, the PV-PHS system resulted in the lower initial cost, therefore, it is better option for the current case study. In contrast, for LPSPs higher than 6.94%, for the same LPSP, PV-Battery system led to the lower investment cost in comparison with PV-PHS, so it can be chosen as a better option regarding designer’s priorities. Also, results show that the proposed strategy can reach a design with the full satisfaction of fluctuating demand and system constraints. In this case, for the yearly average demand of 16.3 kW, the investment cost is obtained to be 2.1M$ and 1.87 M$ for the PV-battery and PV-PHS, respectively. The paper compares in detail the optimal designs and operations obtained for the two hybrid PV-Battery and PV-PHS systems.
Ocean thermal energy has been identified as a good thermal source for electric power generation especially for offshore oil and gas platforms and island energy security. Organic Rankine Cycles (ORCs) are promising systems for conversion ocean thermal energy to electricity; however, the thermal efficiencies still need to be increased. In this work, a dual-pressure ORC is used to improve the thermal efficiency of a closed ocean thermal energy conversion (OTEC) power plant. The evaporation and condensation temperatures of the dual-pressure ORCs are optimized to maximize the net power out. Compared to single-pressure ORCs, the dual-pressure ORCs can reduce the warm seawater temperature drop about 2 °C and generate 28-29% more net power. The working fluid with a higher critical temperature has a lower flow rate for the optimal condition. R600 produces slight high power than the other selected working fluids.
China has launched lots of environmental policies to address the serious air pollution. The effectiveness of such kinds of policies are still in debate. Whether the policy makes a difference or not, this article argues that it highly depends on policy targets recognition. To take the motor vehicle restriction policy as an example, the target of the policy may not only focus on developing the air condition, but also other objectives. This on-hand article conducts a regression discontinuity design to test two goals of Zhengzhou city’s motor vehicle restrictions policy which are efficiency target (“help to complete the political assessment goal”) and legitimacy target (“help to achieve pollution control goal”). This article measures the former goal based on daily data and the latter one based on monthly data, both from Jan. 2016 to Dec. 2018. Air quality is selected by monthly air monitoring station, economic activities data is sorted from the official statistic website, and government action data is collected from the government documents by hand which we follow seriously and scientifically coding rules. Other factors, like climate influences, consumption and production behavior, are also controlled in the experiment. Regression results show that the restriction policy doesn’t make an obvious difference on developing the air quality before and after, but it does have statistically significant effect on helping the urban government to achieve the political assessment goal of the so-called “Qualified days”. The experiment also adjusts the bandwidth of the policy timing. The results obtained were highly robust across a variety of tests. What’s more, to make explanations on the restriction policy failure, this article collects the vehicle selling data and gasoline consumption data during the same period to test the policy spillover effect on consumer behavior. Results show that the driving restriction policy lead to an obvious otherwise slight increase on consumers’ behavior of buying a second car or using the alternative car. This study contributes to empirical evidence and add to a new case of researches on the air pollutants governance and policy evaluation.
This paper developed a new control strategy of distributed battery storage in response to price signal as an effective way of demand side management, using dynamic programming algorism to calculate the hourly power use from grid. An office building in Shenzhen, China was studied, verifying the feasibility of the control strategy. The result turned out that the total electricity cost can be saved by 28.1% comparing with a system without distributed battery storage, and by 8.1% comparing with a system where the distributed battery storage operates in the strategy of constant grid power taking.
Furthermore, the relationship of electricity cost with battery size and maximum charging/discharging power was studied. Based on the model, capacity and maximum charging/discharging power of battery fit well with a segmented linear model, in the range of practical application. The maximum charging/discharging power of battery storage system and minimum electricity fee could be fitted into a quadratic polynomial model. These findings could provide information and give reference for battery storage system design and operation.
Many studies have been conducted to illustrate the production of formic acid (FA) utilizing carbon dioxide (CO2) in an economically viable manner, but the environmental impact has not received much attention. When CO2 is used to produce FA, greenhouse gas including CO2 will be reduced although the economics of FA production utilizing CO2 is lower than that of conventional production using fossil fuel. To achieve a sophisticated understanding of CO2 utilization, this study focuses on life cycle assessment (LCA) for analyzing the environmental impacts of FA production. Based on new process simulation data for CO2-based FA production, we compare the environmental impact results of CO2-based FA to fossil-based FA. LCA has been conducted in consideration of five petrochemical companies located in the industrial complex of Korea to ensure the potential availability of sources.
Flue gas quench (FGQ) at advanced combined heat and power (CHP) plays a vital role by linking flue gas (FG) cleaning and wastewater treatment. In this paper, we have performed a detailed mass balance of pollutants in the flue gas and the process water with and without FGQ at a CHP plant. The results show that the system with FGQ puts less wastewater load (about 74 tonnes/day) together with less pollutant load on the municipal wastewater treatment plant (MWWTP) than the system without FGQ. Meanwhile, it results in fewer burdens on the external water use.
Internal short circuit (ISC) plays an important role in lithium-ion battery safety accidents. However, the mechanism of how ISC triggers thermal runaway is still unclear yet. We implant the shape memory alloy device into jelly-roll to trigger ISC and analyze the thermal and electrical behaviors under different ISC types and SOC variance conditions. The ISC resistance is identified by using the no-salt battery based on the electrochemical impedance spectroscopy tests. The proposed resistance identification method benefits further ISC mechanism and modelling research.
Use of a cheap, non-edible feedstock would reduce the biodiesel production cost and make the process economically viable. This study investigated the production of fatty acid methyl ester (FAME) using both acid (sulfuric acid, H2SO4) and base (sodium hydroxide, NaOH) catalysts. Techno-economic analysis was performed to assess the commercial feasibilities of acidcatalysed biodiesel production from waste shark liver oil (WSLO) and alkali-catalysed biodiesel production from refined vegetable oil in Oman. Historically, the discarded WSLO was used to proof wooden boats, but now these applications are no longer required as modern boats are made of fiberglass. Hence,the excess WSLO derived from these discarded shark livers in the fishing industry could instead be utilised for biodiesel production. This would be environmentally beneficial as it converts a waste into a product. Aspen HYSYS-V9 was used to simulate both production types at plant capacity of 12,000 te/y and lifespan of 20 years. Net present values (NPVs) of US $34.8 and US $4.9 million were obtained for the acidcatalysed process using WSLO and the alkali-catalysed process using refined vegetable oil, respectively. The internal rate of return (IRR) was calculated to be 260% for the acid-catalysed process and 56% for the alkalicatalysed process. Sensitivity analysis was also conducted to show the effect of certain variables on the NPV of both biodiesel production types. It was concluded that the biodiesel selling price has more effect on the NPV than the glycerol variation price, whereas the triglyceride feedstock purchase prices have the largest influence on the NPV of the two processes.
This study involves the application of artificial neural network (ANN) as an intelligent approach to predict the output power of one alpha-type Stirling engine under some operating conditions. One ANN model had been developed based on experimental data from published literature. Output power as one of the performance indicators, was chosen as a response to input parameters, heat source temperature, engine speed and charging pressure. A multi-layer feed-forward network with a back-propagation algorithm had been proposed for such a prediction. The ANN model had been proven to be desirable in accuracy for predicting the output power by comparing the model results with experimental ones under the same operating conditions. This work would provide an effective approach based on ANN technique for solving complex design problems either with linear or nonlinear nature.