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The potential of renewable energy should be fully exploited in the transportation sector to achieve a cleaner production. Therefore, this paper proposes an on-grid hybrid hydrogen refueling and battery swapping station powered by wind energy. This novel concept can promote the development of low-carbon emission vehicles including hydrogen-based vehicle and battery electric vehicle. During the daily operation of the station, the multiple uncertainties may lead to a higher operational cost. To address this problem, a hybrid stochastic/distributionally robust optimization method is proposed to handle different uncertainties for the energy management problem. The first type of uncertainties can be depicted by a certain distribution, i.e. electricity price and wind power, which is processed by a stochastic optimization method. The second type of uncertainties is associated with human behaviors and is difficult to find its probability distribution, i.e. the hydrogen demand of hydrogen-based vehicles, so the second type is processed by a distributionally robust optimization method. The overall objective is to minimize the total operational cost of the station, which also considers the battery swapping station overstock punishment. Because a reasonable battery swapping scheduling can reduce the waiting time of users and operational cost of the station. The results indicate that the proposed method can effectively address the conservatism of solutions as its total operational cost is 4.4% lower than that of the hybrid stochastic/robust optimization method under a high confidence level.

This paper proposes a distributed finite-time secondary controller to achieve average voltage regulation and proportionate current sharing within a finite settling time for autonomous network of dc microgrids. It is employed by using a distributed finite-time control approach which maintains average voltage regulation of the system facilitating proportionate current sharing simultaneously by virtue of dynamic consensus between its neighbors. The proposed scheme ensures an improved performance over the conventional distributed secondary methods by reducing overshoots and chattering which is significant for critical operation of the loads. The proposed control strategy is simulated in MATLAB/Simulink environment to test link-failure resiliency, plug and play capability, and controller performance under communication delays within a tolerable upper bound on delay determined using time-delay analysis. Moreover the effect of variable time delays in different transmission medium is also simulated to test the practicality of the approach. This strategy is further tested on a 500-W FPGA-based experimental prototype to validate the control approach under different scenarios.

Production of biomass and phycocyanin (PC) were investigated in highly pigmented variants of the unicellular rhodophyte Galdieria sulphuraria, which maintained high specific pigment concentrations when grown heterotrophically in darkness. The parental culture, G. sulphuraria 074G was grown on solidified growth media, and intensely coloured colonies were isolated and grown in high-cell-density fed-batch and continuous-flow cultures. These cultures contained 80-110 g L(-1) biomass and 1.4-2.9 g L(-1) PC. The volumetric PC production rates were 0.5-0.9 g L(-1) day(-1). The PC production rates were 11-21 times higher than previously reported for heterotrophic G. sulphuraria 074G grown on glucose and 20-287 times higher than found in phototrophic cultures of Spirulina platensis, the organism presently used for commercial production of PC.

Chaotic switching is a newly evolve randomization method which suppress the conducted electromagnetic interference generated within the DC-DC converter. It can also suppress the spectral peaks present in the frequency band effectively by spread spectrum technique and spread it over the wide range of frequency band implying electromagnetic interference (EMI) suppression. In this article, a chaotic pulse width modulation technique based on randomized carrier frequency modulation with fixed duty ratio is generated through field programable gate array for suppressing the conducted electromagnetic interference generated within the Luo-converter. A hardware prototype of Luo-converter is developed in order to analyze EMI reduction through power spectral density analysis by comparing both traditional periodic PWM switching and chaotic PWM switching. The results obtained from the hardware setup shows significant reduction of EMI with chaotic switching as compared to traditional pulse width modulation switching under both boost and buck operation of Luo-converter.

A European project started at the end of 1992, in which, in addition to current methods, trained sensory panels were used to investigate office buildings all over Europe. The main aim of this EC-Audit was to develop assessment procedures and guid-ance on ventilation and source control, to help optimize energy use in buildings while assuring good indoor air quality. In each of nine countries, six or more office buildings were select-ed. Measurements were performed at five selected locations in each building. The buildings were studied while normally occu-pied and ventilated to identify the pollution sources in the spaces and to quantify the total pollution load caused by the occupants and their activities, as well as the ventilation systems. The investi-gation included physical and chemical measurements, assessment of the perceived air quality in the spaces by a trained sensory pan-el, and measurement of the outdoor air supply to the spaces. A questionnaire for evaluating retrospective and immediate symp-toms and perceptions was given to the occupants of the buildings. The building characteristics were described by use of a check-list. The annual energy consumption of the buildings and the weather conditions were registered. This paper presents results and conclusions of the audit in 56 buildings in Europe. However, the analysis and discussions of the results are a summary of the work done, and are focused mainly on comparison between sensory assessments and the other meas-urements performed. Furthermore, this paper brings the results of the study based on a two-factor analysis. A paper dealing with results on a multifacto-rial analysis is in preparation.

The increasing use of Variable Stiffness Actuators (VSAs) in robotic joints is helping robots to meet the demands of human-robot interaction, requiring high safety and adaptability. The key feature of a VSA is the ability to exploit internal elastic elements to obtain a variable output stiffness. These allow the joints to store mechanical energy supplied through interaction with the environment and make the system more robust, efficient, and safe. This paper discusses the design of leaf springs for a sub-class of VSAs that use variable lever arm ratios as means to change their output stiffness. Given the trade-off between compactness and the maximum energy storage capacity, the internal springs’ dimensions and material choice are assessed through a theoretical analysis and practical experiments.

This study investigated methane yield via anaerobic digestion of multi-component substrates based on mixtures of biodegradable single-component substrates with cow dung as main component. Bench and full-scale digestion experiments were carried out for both single and multi-component substrates to identify the relationship between methane yield and substrate composition. Results from both bench- and full-scale experiments corresponded well and showed that using multi-component substrates increases the methane yield much more than what would be expected from digestion of single substrates. Process stability as indicated by gas production, pH and NH(4)(+) concentration variations were also improved by using multi-component substrates compared to digestion of single-component substrates. The results, thus, suggest that assessment of methane yield for multi-component substrates cannot reliably be based on methane yields for corresponding single-component substrates but should instead be measured directly.