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The acceptability, energy consumption, and environmental benefits of electric vehicles are highly dependent on travel patterns. With increasing ride-hailing popularity in mega-cities, urban mobility patterns are greatly changing; therefore, an investigation of the extent to which electric vehicles would satisfy the needs of ride-hailing drivers becomes important to support sustainable urban growth. A first step in this direction is reported here. GPS-trajectories of 144,867 drivers over 104 million km in Beijing were used to quantify the potential acceptability, energy consumption, and costs of ride-hailing electric vehicle fleets. Average daily travel distance and travel time for ride-hailing drivers was determined to be 129.4 km and 5.7 h; these values are substantially larger than those for household drivers (40.0 km and 1.5 h). Assuming slow level-1 (1.8 KW) or moderate level-2 (7.2 KW) charging is available at all home parking locations, battery electric vehicles with 200 km all electric range (BEV200) could be used by up to 47% or 78% of ride-hailing drivers and electrify up to 20% or 55% of total distance driven by the ride-hailing fleet. With level-2 charging available at home, work, and public parking, the acceptance ceiling increases to up to 91% of drivers and 80% of distance. Our study suggests that long range BEVs and widespread level-2 charging infrastructure are needed for large-scale electrification of ride-hailing mobility in Beijing. The marginal benefits of increased all electric range, effects on charging infrastructure distribution, and payback times are also presented and discussed. Given the observed heterogeneity of ride-hailing vehicle travel, our study outlines the importance of individual-level analysis to understand the electrification potential and future benefits of electric vehicles in the era of shared smart transportation.

Aquifer thermal energy storage (ATES) is a cost-effective technology that enables the reduction of energy use and CO2 emissions associated with the heating and cooling of buildings by storage and recovery of large quantities of thermal energy in the subsurface. Reducing the distance between wells in large-scale application of ATES increases the total amount of energy that can be provided by ATES in a given area. However, due to thermal interference the performance of individual systems can decrease. In this study a novel method is presented that can be used to (a) determine the impact of thermal interference on the economic and environmental performance of ATES and (b) optimize well distances in large-scale applications. The method is demonstrated using the hydrogeological conditions of Amsterdam, Netherlands. Results for this case study show that it is cost-effective to allow a limited amount of thermal interference, such that 30–40% more energy can be provided in a given area compared to the case in which all negative thermal interference is avoided. Sensitivity analysis indicates that optimal well distance is moderately insensitive to changes in hydrogeological and economic conditions. Maximum economic benefit compared to conventional heating and cooling systems on the other hand is sensitive, especially to changes in the gas price and storage temperatures.

Abstract With the large-scale integration of the distribution generations (DGs) and the increasing medium-voltage and low-voltage DC power demands, multi-terminal hybrid AC/DC microgrid has drawn great attention from researchers around the world. In order to reduce the number of power conversion stages and meet DC transmission demands under different DC voltage levels, this paper proposes a four-terminal interconnection scheme of the hybrid AC/DC microgrid, connecting one medium-voltage AC (MVAC) terminal, one medium-voltage DC (MVDC) terminal and two low-voltage DC (LVDC) terminals. The proposed interconnection scheme includes a modular multilevel converter (MMC) as the main interlinking converter of the MVAC grid and MVDC microgrid, and a series of dual active bridges (DAB) converters as two isolated LV DC microgrid interfaces. It has more flexibility for power supplies, especially MVDC transmission, and a more robust tolerance for unequal power distribution between the two LVDC Microgrids. To realize the DC capacitor voltage balancing control, an improved energy control method is proposed in this paper. The proposed method keeps DC capacitor voltage balance and AC current zero on the MVDC transmission lines, which contributes to the stability of the MVDC microgrid. In addition, the symmetry of the AC currents is also guaranteed with this control method. Validation results of a four-terminal hybrid AC/DC microgrid verify the effectiveness of the proposed microgrid and control scheme.

Abstract Grate-firing technology is one of the commonly used technologies for municipal solid waste incineration, which recovers energy and largely reduces the volume of the solid wastes for landfilling. In grate-fired incinerators, the solid wastes are packed in the fuel bed on the grate, where the major heterogeneous conversion takes place. A proper modeling of the fuel conversion process in the bed not only benefits an in-depth understanding of the in-bed incineration but also facilitates the freeboard simulation. In this paper, a comprehensive model is developed to simulate solid wastes incineration in a packed bed, which advances the state-of-the-art with corrected boundary conditions, homogeneous reactions, and calculation method for pyrolysis products. The model is first validated by a simplified analytical problem. Then, the model is validated in detail by a dedicated experimental study in literature, in which the pyrolysis and gas combustion front and the subsequent char oxidation front both propagate from the bed surface to the grate due to the abundant oxygen availability in the fuel bed. The model also outperforms a latest modeling study in literature for reproducing the same experimental study. Finally, a model-based parametric study is conducted to investigate the effects of solid waste particle sizes and solid waste incineration in high-altitude areas. This paper also clearly explains the methods to transfer the packed-bed model to travelling grates and to accommodate the different waste fractions in real municipal solid waste, in order to make the model applicable to travelling grate-firing of real municipal solid wastes.

The Conference on Sustainable Development of Energy, Water and Environment Systems (SDEWES) in 2015 returned to its hometown, Dubrovnik, and once again served as a significant venue for scientists and specialists in different areas of sustainable development from all over the world to initiate, discuss, share, and disseminate new ideas.At the 10th SDEWES Conference, about 500 participants from 64 countries delivered total 541 contributions - 5 invited lectures, 3 panels, 49 regular sessions, 17 special sessions and 5 poster sessions, aimed at deepening the knowledge body and scientific understanding, improvement of long-term scientific assessments, strengthening of scientific capacities around the world and at ensuring that the sciences are responsive to the emerging international, European, regional and national challenges.The dedicated Energy special issue includes 24 papers, which traditionally cover a range of energy issues - higher renewables penetration and various technologies and fuels assessments at energy supply side, as well as, energy efficiency in various sectors, buildings, district heating, electric vehicles and demand modelling at energy demand side. Also, a review paper is included, which analyses selected SDEWES contributions published in the special issues of leading scientific journals and highlights their provisions towards addressing the challenges of energy security in twenty first century.The Guest editors believe that the selected papers and the addressed issues will considerably extend the knowledge body published in Energy journal and will be of interest to its readers.The Guest editors would like to thank all the reviewers who have made most valuable and highly appreciated contributions by reviewing, commenting and advising the authors. Special thanks should go to the administrative staff of the Energy journal for their excellent support.

Abstract In the framework of the European project SSH2S, a solid-state hydrogen storage tank - fuel cell system was demonstrated as Auxiliary Power Unit (APU) for a light duty vehicle. In this work, we have assessed the environmental impacts and the costs of the system developed. Following an eco-design approach, we have identified the processes mostly contributing to them and we have suggested possible improvements. By performing a Life Cycle Assessment (LCA), we found that, when the electricity consumption for hydrogen gas compression is included into the analysis, a solid-state hydrogen storage tank has similar greenhouse gas emissions and primary energy demand than those of type III and IV tanks. However, the resources depletion is higher for the solid-state system, even though the inclusions of the end of life of the APU and the recycling of the materials may result in different conclusions. The costs of an APU equipped with a solid-state hydrogen storage tank are significantly higher, about 1.5–2 times the systems based on type III and IV tanks. However, mature technologies are compared with a prototype, which has much room for optimization. To improve both the environmental and economic performances of the APU, a reduction of structural materials for both the solid-state hydrogen tank and Balance of Plant is recommended.

Abstract The worldwide energy demand has been continuously increasing, thus requesting more sustainable alternatives to the rapidly depleting fossil fuels. Therefore, biofuels such as hydrogen, bioethanol and biodiesel are gaining more importance as a renewable and pollution-free solution, which might give a significant contribution to the future energy mix. In recent years, the exponential growth of biodiesel production has led to a glycerol glut, however, according to some authors, crude glycerol might represent a suitable, abundant and low-priced feedstock for fermentation technologies. In this study we performed an energetic and economic assessment of an innovative process, which is under development in our lab, for the bioconversion of crude glycerol into ethanol and hydrogen. Ongoing experiments showed the possibility to reach at least 26 g/L of ethanol, together with 9 L of hydrogen, in non-sterile conditions and without nutrient supplements. Since kinetics and ethanol concentration need to be further improved, we performed this study with a view to evaluate the possibility of reaching economic viability. Results showed that with 26 g/L of ethanol and a retention time as high as 120 h, the calculated energy cost would be about 0.019 €/kW hth and 0.057 €/kW hel, considering the contribution of both, hydrogen and bioethanol. Moreover, bioethanol cost would be as low as 0.21 €/L, even without taking into account the possible hydrogen revenues. These results are very promising and suggest that the process has reasonable chances to achieve economic viability, thus deserving further attention. The procedure followed in this work provided a realistic and concrete target to pursue in the future lab experiments, in order to bring this technology closer to the market.