Physical-cyber-human framework-based resilience evaluation toward urban power system: Case study from China.

Because the increased frequency, intensity, and duration of extreme weather events have significantly challenged power systems, there has been an increased interest in resilient power systems. This article establishes a multicriteria resilience evaluation framework for urban power systems from a physical-cyber-human system perspective, in which the two principal elements responsible for power system function degradation are described, the three major domains comprising urban power systems are explained, four core capacities that positively contribute to power system resilience are proposed, and 15 (11 objective and four subjective) power system resilience evaluation indicators are identified. Fuzzy hesitant judgment and a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) aggregation method are employed to minimize the expert divergence and maximize the group consensus. A validation method is designed and a comparison with commonly applied performance-based and attributes-based evaluation methods is conducted. The applicability of the evaluation framework is verified using data from four Chinese municipalities: Shanghai, Beijing, Chongqing, and Tianjin. It was found that Shanghai's resilience was the best, and Chongqing's physical resistance disadvantages would result in the greatest difficulties in coping with extreme event disturbances. Physical, cyber, and human domain resilience enhancement strategies are given for different cities separately. This study provides a practical tool to evaluate, compare, and enhance power system resilience for governments and public utilities.

Epidemic versus economic performances of the COVID-19 lockdown: A big data driven analysis.

Lockdown measures have been a "panacea" for pandemic control but also a violent "poison" for economies. Lockdown policies strongly restrict human mobility but mobility reduce does harm to economics. Governments meet a thorny problem in balancing the pros and cons of lockdown policies, but lack comprehensive and quantified guides. Based on millions of financial transaction records, and billions of mobility data, we tracked spatio-temporal business networks and human daily mobility, then proposed a high-resolution two-sided framework to assess the epidemiological performance and economic damage of different lockdown policies. We found that the pandemic duration under the strictest lockdown is less about two months than that under the lightest lockdown, which makes the strictest lockdown characterize both epidemiologically and economically efficient. Moreover, based on the two-sided model, we explored the spatial lockdown strategy. We argue that cutting off intercity commuting is significant in both epidemiological and economical aspects, and finally helped governments figure out the Pareto optimal solution set of lockdown strategy.

1.6 Million transactions replicate distributed PV market slowdown by COVID-19 lockdown.

Solar PV has seen a spectacular market development in recent years and has become a cost competitive source of electricity in many parts of the world. Yet, prospective observations show that the coronavirus pandemic could impact renewable energy projects, especially in the distributed market. Tracking and attributing the economic footprint of COVID-19 lockdowns in the photovoltaic sector poses a significant research challenge. Based on millions of financial transaction records and 44 thousand photovoltaic installation records, we tracked the spatio-temporal sale network of the distributed photovoltaic market and explored the extent of market slowdown. We found that a two-month lockdown duration can be assessed as a high-risk threshold value. When the lockdown duration exceeds the threshold value, the monthly value-added loss reaches 67.7%, and emission reduction capacity is cut by 64.2% over the whole year. We show that risks of a slowdown in PV deployment due to COVID-19 lockdowns can be mitigated by comprehensive incentive strategies for the distributed PV market amid market uncertainties.

Unpacking the effects of natural gas price transmission on electricity prices in Nordic countries.

Since the Russia-Ukraine war in February 2022, European electricity prices have experienced considerable turbulence, primarily attributed to a shortage in the natural gas supply. We investigate the relationship between natural gas prices in the European continent and electricity prices in Nordic countries before and after the outbreak of war. Despite the low proportion of natural gas electricity generation, the empirical analysis reveals both direct and indirect transmission paths for natural gas prices in Nordic countries. Meanwhile, the theoretical analysis demonstrates how Nordic renewable (wind and solar) and other non-gas generators exercise market power through price bidding in the anticipation of an increase in gas prices or a shortage of gas supply, which results in higher electricity prices. Understanding the underlying factors and dynamics driving substantial price fluctuations in the Nordic electricity market is essential for comprehending the intricate interconnections within the European energy landscape.

Multi-resource dynamic coordinated planning of flexible distribution network.

The flexible distribution network presents a promising architecture to accommodate highly integrated distributed generators and increasing loads in an efficient and cost-effective way. The distribution network is characterised by flexible interconnections and expansions based on soft open points, which enables it to dispatch power flow over the entire system with enhanced controllability and compatibility. Herein, we propose a multi-resource dynamic coordinated planning method of flexible distribution network that allows allocation strategies to be determined over a long-term planning period. Additionally, we establish a probabilistic framework to address source-load uncertainties, which mitigates the security risks of voltage violations and line overloads. A practical distribution network is adopted for flexible upgrading based on soft open points, and its cost benefits are evaluated and compared with that of traditional planning approaches. By adjusting the acceptable violation probability in chance constraints, a trade-off between investment efficiency and operational security can be realised.

Techno-economic assessment of implementing photovoltaic water villas in Maldives.

Solar energy is considered to be an effective measure to alleviate the shortage of power supply in the Maldives. In this paper, a roof photovoltaic (PV) system integrated into water villas in the Maldives was investigated. Three islands-Ayada Maldives, Angaga Island Resort, and JA Manafaru, located in the southern, central, and northern parts of Maldives-were selected for a case study. The potential of PV installations in Ayada Maldives, Angaga Island Resort, and JA Manafaru reaches 1,410, 445, and 742 kW, with corresponding annual power generation of 2.04, 0.64, and 1.12 GWh, respectively. The profits over the life cycle of 25 years of the above three studied islands are 4.86, 1.52, and 2.90 million USD, respectively, with payback periods in the range of 6-7 years.

Refinement and predicting formaldehyde concentrations of indoor fabric: Effects of temperature and humidity.

Indoor air pollution resulting from volatile organic compounds (VOCs) is a significant health concern, especially formaldehyde. Therefore, predicting indoor formaldehyde concentration is essential for environmental control. In this research, the authors develop a thermal and wet coupling calculation model of porous fabric that considers the influence of different phases of wet components and the coupling effect of heat and humidity on formaldehyde migration. We propose a modified calculation method of the formaldehyde mass transfer characteristic parameters of fabric to obtain the diffusion coefficient D and partition coefficient K. The heat and humidity coupling model and formaldehyde mass transfer model of fabric are simultaneously solved, and the authors analyze the influence mechanism of fabric loading rate, fabric type, temperature, and humidity on indoor formaldehyde mass transfer characteristics. We study the variation trend of fabric formaldehyde mass transfer characteristics coefficient and the temporal and spatial distribution of indoor formaldehyde concentration. The theoretical model is applied to practical problems by pre-evaluating the indoor formaldehyde concentration of decorated residential buildings in typical climate areas of China before occupancy. The authors obtain the variation rule of indoor formaldehyde concentration of residential buildings under typical hot and humid climate conditions, building materials, furniture, and fabrics. To provide theoretical support for indoor environmental control and human health protection.

Parameter optimization analysis of rotary electromagnetic vibration energy harvester for performance enhancement under free vibration.

In this paper, three new important aspects of rotary electromagnetic vibration energy harvesting technology (RE-VEH) are concerned and investigated: (i) vibro-electric coupling mechanism of the RE-VEH system is studied through theoretical modeling; (ii) quantitative analysis of system parameters based on numerical simulation method is carried out for the optimal design of RE-VEH; and (iii) dynamic power output performance of the RE-VEH system in free vibration is discussed. The parameter adjusting methods of the RE-VEH system in free vibration mode are obtained through theoretical analysis and numerical simulation. The experimental results show that the power output performance of RE-VEH in free vibration mode matches the numerical simulation results. The simulation and experimental results show that the maximum voltage output and power output of the RE-VEH with different structure parameters under free vibration can be up to the level of 100∼101 V/watt. The above results indicate that RE-VEH in a free vibration environment has significant energy output performance.

Carbon mitigation potential afforded by rooftop photovoltaic in China.

Rooftop photovoltaics (RPVs) are crucial in achieving energy transition and climate goals, especially in cities with high building density and substantial energy consumption. Estimating RPV carbon mitigation potential at the city level of an entire large country is challenging given difficulties in assessing rooftop area. Here, using multi-source heterogeneous geospatial data and machine learning regression, we identify a total of 65,962 km2 rooftop area in 2020 for 354 Chinese cities, which represents 4 billion tons of carbon mitigation under ideal assumptions. Considering urban land expansion and power mix transformation, the potential remains at 3-4 billion tons in 2030, when China plans to reach its carbon peak. However, most cities have exploited less than 1% of their potential. We provide analysis of geographical endowment to better support future practice. Our study provides critical insights for targeted RPV development in China and can serve as a foundation for similar work in other countries.

A review of vibration energy harvesting in rail transportation field.

In this paper, we review, compare, and analyze previous studies on vibration energy harvesting and related technologies. First, the paper introduces the basic aspects of vibration energy acquisition in the railway environment, including vibration frequency, train speed, energy flow in the train, and vibration energy harvesting potential. Generally, the methods for scavenging vibration energy caused by passing trains can be divided into four categories: electromagnetic harvesters, piezoelectric harvesters, triboelectric harvesters, and hydraulic harvesters. The structure, output performance, merits, and disadvantages of different energy harvesting strategies are summarized and compared. The application of vibration energy harvesters is explained as supplying power to monitoring sensors on the line side and the vehicle side. Finally, the paper addresses the challenges and difficulties that have not been completely resolved in the current research literature, including system stability, durability, and economy. Some recommendations to fill these research gaps are put forward for further investigation.

Vectorized rooftop area data for 90 cities in China.

Reliable information on building rooftops is crucial for utilizing limited urban space effectively. In recent decades, the demand for accurate and up-to-date data on the areas of rooftops on a large-scale is increasing. However, obtaining these data is challenging due to the limited capability of conventional computer vision methods and the high cost of 3D modeling involving aerial photogrammetry. In this study, a geospatial artificial intelligence framework is presented to obtain data for rooftops using high-resolution open-access remote sensing imagery. This framework is used to generate vectorized data for rooftops in 90 cities in China. The data was validated on test samples of 180 km2 across different regions with spatial resolution, overall accuracy, and F1 score of 1 m, 97.95%, and 83.11%, respectively. In addition, the generated rooftop area conforms to the urban morphological characteristics and reflects urbanization level. These results demonstrate that the generated dataset can be used for data support and decision-making that can facilitate sustainable urban development effectively.

Carbon footprint of oil products pipeline transportation.

As climate issues gradually attract public attention worldwide, the operation and construction of oil product pipelines have been attached with new energy-saving and emission-reduction targets. Though previous studies concerning Life Cycle Assessment of oil and gas pipelines have estimated the carbon footprint to some extent, there is a lack of researches that take the characteristics of oil products pipelines into consideration. Oil products pipelines undertake the task of delivering various products to downstream demand locations, which differs greatly from other pipeline transportation systems as back-to-back sequential delivery is adopted. In this paper, a detailed Life Cycle Assessment model is established to analyze carbon emissions of oil products pipeline system from construction to disposal as well as its impact on soil environment. Data from practical pipes is adopted as the case study to reflect emissions produced in different stages, and the amount of total and unified emissions of different pipes provided through the proposed model is within the range of 2.78 to 4.70 tCO2e/t·km. Then, sensitivity analysis is carried out to identify the driving factors of emissions. According to the calculation results, pipe length, diameter and throughput turn out to be the dominating factors, and an empirical formula is derived for future planned pipes. Relevant recommendations are put forward based on the results to help reduce emissions from oil product pipe transportation.

Using Existing Infrastructure to Realize Low-Cost and Flexible Photovoltaic Power Generation in Areas with High-Power Demand in China.

This study develops a new concept involving using the existing infrastructure for photovoltaic (PV) generation to reduce the costs associated with increased land use and to avoid curtailment due to the mismatch between power supply and demand. We establish a method to estimate the technological potential and economic performance of the PV systems deployed in coal-fired power plants in China. The potential capacity of the examined 1,082 units in China reaches 4 GWe, which is equivalent to 32% of China's newly installed distributed PV capacity in 2019. A total of 87% of PV systems achieve plant-side grid parity compared with desulfurized coal benchmark electricity prices. To the best of our knowledge, this is the first study that investigates the use of rooftops and coal storage sheds in power plants to facilitate low-cost, flexible PV power generation, thus opening a new channel for future PV generation development.

The role of adsorbed oleylamine on gold catalysts during synthesis for highly selective electrocatalytic reduction of CO2 to CO.

The low-coordinated sites of electrocatalysts favour hydrogen evolution, while the edge sites are active for CO2 reduction. Oleylamine is used to stabilize nanoparticles by adsorbing on the low-coordinated sites. The hydrogen evolution reaction was dramatically suppressed and the FECO remained >93% from -0.4 to -0.8 V (vs. RHE) when oleylamine ligands existed on the surface of a gold catalyst. More H+ and electrons were involved in the CO evolution reaction, which changed the rate-limiting step from single-electron transfer to the chemical reaction step. The results establish that the surface-adsorbed surfactants during catalyst synthesis have an important effect on CO2 electrocatalytic reduction.

Self-preservation strategy for approaching global warming targets in the post-Paris Agreement era.

A strategy that informs on countries' potential losses due to lack of climate action may facilitate global climate governance. Here, we quantify a distribution of mitigation effort whereby each country is economically better off than under current climate pledges. This effort-sharing optimizing approach applied to a 1.5 °C and 2 °C global warming threshold suggests self-preservation emissions trajectories to inform NDCs enhancement and long-term strategies. Results show that following the current emissions reduction efforts, the whole world would experience a washout of benefit, amounting to almost 126.68-616.12 trillion dollars until 2100 compared to 1.5 °C or well below 2 °C commensurate action. If countries are even unable to implement their current NDCs, the whole world would lose more benefit, almost 149.78-791.98 trillion dollars until 2100. On the contrary, all countries will be able to have a significant positive cumulative net income before 2100 if they follow the self-preservation strategy.

Annual performance analysis and comparison of pellet production integrated with an existing combined heat and power plant.

Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials (wood chips and solid hydrolysis residues) are studied. The year is divided into 12 periods, and the integrated biorefinery systems are modeled and simulated for each period. The annual economic performance of three integrated biorefinery systems is analyzed based on the simulation results. The option of pellet production integrated with the existing CHP plant with the exhaust flue gas and superheated steam as drying mediums has the lowest specific pellet production cost of 105 €/t(pellet), the shortest payback time of less than 2 years and the greatest CO(2) reduction of the three options. An advantage in common among the three options is a dramatic increase of the total annual power production and significant CO(2) reduction in spite of a small decrease of power efficiency.

Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxides.

Mixed oxides of TiO(2)-MgO obtained by the sol-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst, TiO(2)-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.

Intensification of biodiesel synthesis using zigzag micro-channel reactors.

Zigzag micro-channel reactors have been fabricated and used for continuous alkali-catalyzed biodiesel synthesis. The influences of the main geometric parameters on the performance of the micro-channel reactors were experimentally studied. It has been found that the zigzag micro-channel reactor with smaller channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional stirred reactors, the time for high methyl ester conversion can be shortened significantly with the methyl ester yield of 99.5% at the residence time of only 28 s by using the optimized zigzag micro-channel reactor, which also exhibits less energy consumption for the same amount of biodiesel during biodiesel synthesis. The results indicate that zigzag micro-channel reactors can be designed as compact and mini-fuel processing plant for distributive applications.