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With the integration of large‐scale electric vehicles (EVs), more capacities of medium voltage distribution networks need to be released. However, there are limited spaces to build new lines, and voltage violation may happen due to the power fluctuation when EVs charge/discharge in a random way. This study proposes to convert some existing AC medium voltage distribution lines to DC and forms a hybrid AC/DC medium voltage distribution network through connecting existing AC lines with a voltage source converter (VSC). Transfer capacity of lines can be increased through DC distribution and flexible power shift between the AC and DC lines can be achieved, based on which more EVs can be accommodated. Configurations of hybrid AC/DC distribution networks are developed, and the capacities released are quantified. A control scheme, which includes a loss minimisation mode and a voltage regulation mode, is proposed in order to optimise real and reactive power outputs of the VSC. Simulation studies are performed to verify the proposed method.

In this review, we systematically summarizes the activity descriptors of CO2 methanation, the recent advances of SSCs for electrocatalytic CO2 methanation, and in situ characterizations used for tracking the structure change of SSCs during CO2RR.

Abstract In this study, the potential advantages of fuels derived from coffee waste were evaluated and quantified over the entire life cycle. Life cycle evaluation is important for achieving robust understanding because it covers the entire sequence of stages of fuel production and utilization. Coffee waste collection and transport, oil extraction, and biodiesel production and transport are the stages covered under the first life phase, called “well-to-pump.” Extensive engine tests were also conducted to assess the second life phase, “pump-to-wheel.” Environmental, economic, energetic, and technical criteria were encapsulated within the frame of each phase, and various evaluation tools that fit each life stage were adopted. The results showed that coffee biodiesel contributes to an 80.5% reduction in CO2 emissions compared with the hydrocarbon diesel during its life cycle. Moreover, the conversion efficiency of the raw material energy to fuel energy in the case of coffee biodiesel was 10% higher than that of the petro-diesel. An energy amount of 3.45 MJ is associated with coffee biodiesel for each 1 MJ consumed in its life cycle. The economic viability of coffee biodiesel was found to be very sensitive to the price of the coffee solid fuel (biomass pellets). The entire project is feasible only when the price of pellets is 40% of that of wood pellets or higher. Substantial reduction of tailpipe emissions was attained for CO, CO2, and HC, with 45.3%, 5.7%, and 23.6% reductions, respectively, for B20. Reductions of 10.3% and 7.5% were observed in the brake thermal efficiency and brake power, respectively. Thus, coffee biodiesel has significant advantages and potential, and its technological development merits further research.

This paper evaluates the energy and cost benefits for deployment of hybrid indirect evaporative and vapor compression systems for the existing Saudi residential building stock. Both experimental and simulation analyses are carried out to perform large scale energy, environmental, and economic assessments. The energy efficiency of the hybrid system is tested and measured under various operating conditions. The experimental data are then incorporated in a residential building stock model established for Saudi Arabia to quantify the energy, environmental, and economic performance of the hybrid systems relative to the current air conditioning systems. It is found through the testing analysis that the hybrid systems can double of the coefficient of performance of the vapor compression only air conditioning units especially when outdoor air temperatures are high. Moreover, it is estimated that the deployment of hybrid systems for Saudi residential building stocks achieves annual reductions of 51 TWh in electricity consumption and 38 million tons in carbon emissions with an average payback period of less than one year. ; The study presented in this paper is funded by KAUST Cooling Initiative, REP/3988/01-01.

AbstractWhile annual precipitation in much of the US Corn Belt is likely to remain constant, atmospheric vapor pressure deficit (VPD), the driver of crop water loss (evapotranspiration; ET), is projected to increase from ~2.2 kPa today to ~2.7 kPa by mid‐century primarily due to the temperature increase. Without irrigation, it has been hypothesized that the increase in VPD will create a ceiling to future increases in maize yields. We calculated current and future growing season ET based on biomass, water use efficiency, and the amount of yield these levels of ET would support for maize production in the Midwest USA. We assumed that the production of more grain will necessitate a proportional increase in the production of biomass, with a corresponding increase in ET. Here we show that as VPD increases, maintaining current maize yields (2013–2016) will require a large expansion of irrigation, greater than threefold, in areas currently supported by rain. The average predicted yield for the region of 244 ± 4 bushels/acre (15,316 ± 251 kg/ha) projected for 2050, assuming yield increases observed for the past 60 yr continue, would not be possible with projected increases in VPD, creating a water ceiling to maize yields. Substantial increases in maize yields and the production of high yielding grasses for bioenergy will require developing cultivars with greater water use efficiency, a trait that has not been a priority for breeders in the past.

Our current society is facing challenges in both sustainability and environmental pollution due to fast urbanization, limited resources, and increasing senior population. Smart cities which aim to increase efficiency and convenience would not be able to solve fundamental challenges caused by urban lifestyles. In 2013, the Universal Village concept was proposed to enhance human-nature harmony through prudent use of technologies and to address the eco-challenges due to fast urbanization.This paper first studies the environmental implications due to urban lifestyles and proposes the suitable UV framework and detailed content of universal village lifestyle in order to address the eco-challenges. The paper then evaluates the development of current smart city technologies and assesses their validity with regard to the concept of Universal Village through systematic studies of several major intelligent systems.Specifically, this paper discusses the subject of connectivity from four perspectives: mutual interaction, feedback loop, dynamic information loop, and material cycle. The paper evaluates whether information feedback loops could be formed for these major systems, and also explores the mutual interaction and dependence among the seemingly independent major systems. We discover that mutual interaction connects the aforementioned systems into an interconnected network and naturally forms dynamic information loops in which the decision of one system may be the required input of another system or vice versa. This implies that proper functioning of these systems requires extensive information sharing among them. One event might dynamically trigger different events. The last connectivity is a material cycle. We explore the whole life cycle of products, including impact from lifestyle, customers’ need, product design, cloud manufacturing, sale channel, feedback collection from customers, reuse and recycling, scrapping, to final waste-disposal, etc., and study how to reduce the demand for resource and waste during the procedure. The idea is to include the perspective of UV lifestyle when designing products: considering the possibility in proactively reducing the need, sharing a product with different people, reusing product parts into the manufacturing, recycling reusable components of finished products before the products’ being fully disassembled, etc. The advantage is to reduce the need for products and to avoid manufacturing the same components from raw materials directly, which demands less resource.In summary, connectivity, as discussed from the four perspectives, would greatly contribute to the effectiveness and efficiency of our connected smart systems. Dynamic information loop helps coordinate resource allocation, decreases the collective costs, and reduces demand of natural resources from the natural environment, resulting in less damage to the environment which ultimately enhances system-wide harmony between human and its natural environment, and leads to human happiness in general.

China has committed to achieve net carbon neutrality by 2060 to combat global climate change, which will require unprecedented deployment of negative emissions technologies, renewable energies (RE), and complementary infrastructure. At terawatt-scale deployment, land use limitations interact with operational and economic features of power systems. To address this, we developed a spatially resolved resource assessment and power systems planning optimization that models a full year of power system operations, sub-provincial RE siting criteria, and transmission connections. Our modeling results show that wind and solar must be expanded to 2,000 to 3,900 GW each, with one plausible pathway leading to 300 GW/yr combined annual additions in 2046 to 2060, a three-fold increase from today. Over 80% of solar and 55% of wind is constructed within 100 km of major load centers when accounting for current policies regarding land use. Large-scale low-carbon systems must balance key trade-offs in land use, RE resource quality, grid integration, and costs. Under more restrictive RE siting policies, at least 740 GW of distributed solar would become economically feasible in regions with high demand, where utility-scale deployment is limited by competition with agricultural land. Effective planning and policy formulation are necessary to achieve China’s climate goals.

In order to achieve the Paris Agreement goals of keeping the temperature rise well below 2 °C or even 1.5 °C, all countries would need to make fair and ambitious contributions to reducing emissions. A vast majority of countries have adopted reduction targets by 2030 in their Nationally Determined Contributions (NDCs). There are many alternative ways to analyze the fairness of national mitigation contributions. This article uses a model framework based on six equity principles of effort-sharing, to allocate countries’ reduction targets under global emissions scenarios consistent with meeting the Paris climate goals. It further compares these allocations with the NDCs. The analysis shows that most countries need to adopt more ambitious reduction targets by 2030 to meet 2 °C, and even more for 1.5 °C. In the context of 2 °C, the NDCs of the United States of America and the European Union lack ambition with respect to the approaches that emphasize responsibility; China's NDC projection falls short of satisfying any approach in 2030. In the context of 1.5 °C, only India, by implementing its most ambitious efforts by 2030, could be in line with most equity principles. For most countries, the NDCs would use most of their allowed emissions space for the entire 21 st century by 2030, posing a major challenge to transform to a pathway consistent with their fair contributions in the long-term.