Abstract

In recent years, the diagnostic and sensing field has put forward higher requirements for portable, sustainable and clean power sources for small electronic devices, which promoted the research and development of new micropower sources. Paper-based microfluidic fuel cell (PMFC) has gradually become the most promising micro power source because of its simple structure, low cost and zero pollution. In this paper, we have studied the effect of Nafion content in catalyst layer on the output performance of PMFC, and further explored the reaction mechanism of PMFC under different Nafion solution distribution. The results show that using the catalyst layer prepared by mixing 0.4 mL Nafion solution will produce a higher maximum current density and peak power density. Additionally, with a constant amount of Nafion solution, the prepared catalyst layer with extra 0.2 mL Nafion solution spraying on its surface can greatly reduce the starting time without affecting the performance of the fuel cell.

Abstract

The kinetics of CO2 /C3H8 hydrate at the temperature of 275.6K-277.6K and pressure of 2MPa-3MPa was investigated. To improve the rate of hydrate formation and water conversion, cyclopentane (CP) with a volume ratio of 0.05-0.25 was employed as a promotor. The results demonstrated that higher pressure leads to more hydrate formation due to higher driving force. Moreover, the addition of CP can significantly accelerate the hydrate formation under a low pressure of 2MPa. The highest gas uptake with a CP/liquid phase ratio of 0.25 was 4.5 times higher than without CP. The findings in this study could provide insights on selecting appropriate conditions which improve the kinetics of hydrate formation to achieve the purpose of hydrate-based desalination.

Abstract

The presence of barriers, mainly related to the information and economic spheres, limits the diffusion of industrial energy efficiency. To overcome this situation, industrial decision-makers should perform comprehensive assessments of energy efficiency measures, including the analysis of the contextual dimension in which their adoption should be embedded. Indeed, contextual characteristics have been shown to strongly influence the descriptive characteristics of energy efficiency measures and their multiple impacts coming from their adoption, e.g., by increasing their criticality based on distance from the firms’ core business or on firm size. Given the lack of in-depth analysis in the literature, this empirical study represents an initial exploratory analysis of the influence of the context on the adoption of energy efficiency measures. The results clearly point to the need for future research on the topic and the development of a framework for industrial decision-makers and policy-makers to systematically analyse the influence of contextual characteristics on the descriptive characteristics of energy efficiency measures and their multiple impacts on operations, productivity and overall firm’s sustainability.

Abstract

Urban decarbonization is a crucial step for China to achieve the goal of carbon neutrality. It is essential to adjust the energy structure and increase the proportion of new energy in the energy structure for cities. This paper aims to construct a technical and economic model to evaluate the emission reduction potential and economic impact of the photovoltaic (PV) and photovoltaic plus electric vehicles (PV+EV) systems in Shenzhen city. It is found that both systems can reduce emissions, the PV+EV system can reduce carbon emissions by up to 45%, and the costs can be reduced by 25%. The construction of this system is cost-effective for achieving the carbon neutrality target.

Abstract

This paper addresses the techno-economic viability of rooftop PV systems with batteries in Brazil for low voltage prosumers under net metering. Besides the traditional metrics NPV and LCOE, two additional indices adequate for battery systems are considered: the LCOS that measures cost, and the LVOS – Levelized Value of Storage, defined in this paper to assess the value that storage adds to a PV system. The study is conducted in software SAM of NREL, which allows to simulate systems performance over their lifetime and include the effect of equipment and parts replacement, degradation, and other operational aspects. Systems under net metering and TOU tariffs located in two Brazilian state capitals, one with very good solar radiation and high energy tariffs and the other with worse conditions, are assessed. Results suggest that the inclusion of storage can provide acceptable returns over investment only when justified by technical reasons.

Abstract

Flexible thin-film micro combustion-thermoelectric coupled (tf-MTC) device which composed of annular thin-film thermoelectric generator (ATTEG) and catalytic combustor based on Pt nanoparticles shows the potential to provide power for the portable electronic devices. The tf-MTC with in suit heat source directly attached on the ATTEG shows a great reduction of heat loss without the mechanical contact between TEG and heat source. The device shows higer power output for the higher quality temperature input of the catalytic combustion when compared with the flexible thermoelectric device without in situ heat source, and is suitable for various application scenarios for the flexibility and small size. Methanol and ethanol were chosen as the fuel of catalytic combustion for the study of the output performance of the coupled device to find out the appropriate application scenarios. This paper mainly explored the difference of output performances of the coupled device with methanol and ethanol. With the consideration of the characteristics of methanol and ethanol during catalytic combustion based on Pt nanoparticles. Multicycle test with on and off state of the reactant mixture was applied to methanol, and single cycle test with long time use was applied to both methanol and ethanol. The results of multicycle test showed similar repetitive typical temperature and output performance of the tf-MTC device. An obvious increase of output performance was obtained during single cycle test of the tf-MTC device with ethanol when compared with methanol. The output voltage and the maximum output power reached 0.201 V and 2.38 μW, respectively. The results indicates both methanol and ethanol are suitable for the tf-MTC device as power generator, and different output performances paly a guiding role of the choice of the fuel for different application scenarios.

Abstract

Proton exchange membrane fuel cells are promised to be the future choice for transportation power systems. Start-up procedure has significant impacts on fuel cell degradation. Most damages induced by start-up procedure relate to the hydrogen/air interface inside fuel cell. Studying on hydrogen/air interface is crucial for start-up degradation mitigation. It is difficult to monitor the internal distribution and transfer of hydrogen and oxygen by experiments. Therefore, this paper establishes a three-dimensional two-phase fuel cell model to simulate the gas concentration distribution in anode compartment, and proposes a start-up purging strategy by injecting hydrogen into the anode. The hydrogen/air interface removal process is simulated and visualized. Subsequently, the impacts of initial residual oxygen concentration and hydrogen flow rate on air removal in anode compartment are studied. It is proved that decrease initial oxygen concentration and increase hydrogen injection flow rate can significantly shorten the purge time. However, small flow rate of hydrogen injection is more economical for start-up purging when residual oxygen concentration is small. The results found in this paper can guide the experimental study of start-up purging strategy, and enrich high-performing and long-lasting design application theory of fuel cell.

Abstract

With the growing penetration of RES, more flexibility is required in power system. District heating system with large capacity is able to offer flexibility to power system. Based on the model of a district heating system built by heat current method, this work proposes a quantification method to evaluate the flexibility of district heating system, which is a hybrid algorithm utilizing simulations and dichotomy method. Quantitative indicators including average power shifting capability and available storage capacity are defined to describe the flexibility. The results of case study present the flexibility of system under a general working condition. Then, influence factors are discussed that with the increase of dispatch time and decrease of the time of heat migration delay, the storage capacity of heating network increases.

Abstract

Due to serious wind power network security such as the randomness and suddenness of wind speed, and the current wind speed forecasting cannot meet the industrial demand, it is urgent to realize the influence of wind speed forecasting. In this article, the short-term forecast of wind speed is revised. The structure and prediction method, combined with historical NWP (numerical weather forecast) wind speed and historical measured wind speed and other related data, established an online modification model for short-term wind speed forecasting. The model uses historical NWP wind speed as model input data, and historical measured wind speed as output data. First, train the model in an offline environment to test the effect of the model; secondly, train the model in an online environment and modify the model dynamically; finally, get the optimal short-term NWP wind speed forecast modification model. Using the established modification model, the historical NWP data of a wind spot in North China was modified. Compared with the original NWP data, the accuracy was improved by 0.861 m/s, which proved the effectiveness of the NWP modification method. At the same time, it proves the effectiveness of the online model and reduces the model’s dependence on historical data.

Abstract

Electrochemical CO2 reduction reaction (CO2RR) involves complicated processes spanning multiple scales, so understanding their effects on device performance is highly desired. Here, we present a multiscale strategy to predict the performance of an Ag-based H-type cell. The multiscale model consists of 1-D macro model, microkinetic model, and density functional theory (DFT) model. Free energy and barriers for CO2RR and hydrogen evolution reaction (HER) over Ag(111) surface are first obtained from the DFT model. These energy values are then used to determine the reaction rates for CO2RR and HER in the microkinetic model. These reaction rate values are finally imported into the macro model containing aqueous species. Using this multiscale model, we predicted the distribution of products and the partial current densities. We also described how factors such as CO2 coverage, the adsorption energy of H2O, and cathodic voltage affect electrochemical performance. Simulations under different CO2 pressures are being implemented, which is of great significance for understanding the mechanism of high-pressure electrochemical reduction of CO2. The investigation of electrochemical CO2RR presented in this work is helpful for the rational design of a high-performance CO2RR system.