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Coherence in Photosynthesis It is unclear how energy absorbed by pigments in antenna proteins is transferred to the central site of chemical catalysis during photosynthesis. Hildner et al. (p. 1448 ) observed coherence—prolonged persistence of a quantum mechanical phase relationship—at the single-molecule level in light-harvesting complexes from purple bacteria. The results bolster conclusions from past ensemble measurements that coherence plays a pivotal role in photosynthetic energy transfer. Hayes et al. (p. 1431 , published online 18 April) examined a series of small molecules comprised of bridged chromophores that also manifest prolonged coherence.

No mundo atual em que vivemos, em constante mudança, o setor dos transportes tem um papel crucial na atividade económica mundial. Contudo, representa um consumo elevado de recursos energéticos e ainda é um dos principais responsáveis pela emissão de gases com efeito de estufa. A mobilidade elétrica e eletrificação das frotas contribuiu para uma redução direta da emissão de gases, representando uma vantagem sobre os veículos com motores de combustão interna. Todavia, a limitação dos sistemas de armazenamento de energia elétrica em termos de autonomia (número de quilómetros percorridos) ainda é um dos maiores entraves a uma maior penetração no mercado dos veículos elétricos. No setor mais específico dos autocarros elétricos, em particular o autocarro de aeroporto, esta desvantagem é amplificada não só pela dimensão e peso, mas também pelos sistemas auxiliares de aquecimento, ventilação e ar-condicionado (AVAC) inerentes a este tipo de veículos. O presente trabalho tem por objetivo a análise e otimização da eficiência energética do modelo e.Cobus, um autocarro de aeroporto. Para alcançar o objetivo foram estudadas algumas unidades e.Cobus em condições reais de operação e analisadas as potências e consumos de energia das diferentes cargas, criando diversos dataset’s. Com os dataset’s elaborados, e recorrendo à plataforma de aprendizagem máquina WEKA, e aplicação de alguns algoritmos, foram desenvolvidos modelos de previsão do consumo de energia que permitiram otimizar a capacidade de armazenamento energético (baterias) destes autocarros, em função da utilização e local geográfico

MgO/H2O/Mg(OH)2 chemical heat storage of waste energy from industrial processes is a promising technology in view of a more efficient use and saving of primary energy sources. A new approach was used to develop a hybrid heat storage material made of magnesium hydroxide (Mg(OH)2) and exfoliated graphite (which is used to improve the heat transfer with its high thermal conductivity). Mg(OH)2 nanoplatelets were directly grown on graphite surface via a deposition–precipitation method to increase the compatibility between the two materials. The material thus obtained, named DP-MG, was experimentally tested to determine its heat storage and output capacities. An improvement of the material efficiency was obtained with a higher storage capacity at lower reaction temperature and a higher heat output rate.

AbstractClimate change and land‐use change are two major drivers of biome shifts causing habitat and biodiversity loss. What is missing is a continental‐scale future projection of the estimated relative impacts of both drivers on biome shifts over the course of this century. Here, we provide such a projection for the biodiverse region of Latin America under four socio‐economic development scenarios. We find that across all scenarios 5–6% of the total area will undergo biome shifts that can be attributed to climate change until 2099. The relative impact of climate change on biome shifts may overtake land‐use change even under an optimistic climate scenario, if land‐use expansion is halted by the mid‐century. We suggest that constraining land‐use change and preserving the remaining natural vegetation early during this century creates opportunities to mitigate climate‐change impacts during the second half of this century. Our results may guide the evaluation of socio‐economic scenarios in terms of their potential for biome conservation under global change.

An aerodynamic shape optimization method for a horizontal axis wind turbine is developed and verified through experimentation with a laboratory-scale wind turbine. Our method is based on matching the rotor's and the coupled generator's torque. Prior to shape optimization, an initial rotor design is established with a hybrid use of Schmitz and blade element momentum theories. The experimental verification of the developed method is conducted with a small-scale wind turbine; thus, the operating Reynolds number is one order of magnitude lower than large-scale wind turbines. Therefore, a high-lift low-Re airfoil, namely, SG6043, is selected for the blade along the whole span. The shape is optimized by determining the optimum chord and cumulative pitch angle distributions by manipulating the tapering and twisting of the blade. The objective of the optimization is to maximize the turbine's power coefficient Cp, while maintaining the torque equal to that of the generator. The generator's characteristics are found through experimentations which are conducted apart from the wind tunnel experiments. During the optimization process, the local aerodynamic forces on the blade are calculated by interfacing the optimization program with XFOIL; thus, the torque and power can be calculated for the rotor at each iteration step. The optimized turbine performance is evaluated under a design and off-design operating condition. The performance verification experiments are carried out in the wind tunnel with a specially designed setup. A comparison of the measured and computed performance shows good agreement.

Capítulos en libros This paper assesses the scalability and replicability of smart grid projects, by means of the identification of limitations and barriers faced by these projects. Factors have been identified that impact a project s scalability and replicability by means of a review of demonstration projects. The factors are of technical, economic, regulatory and social acceptance nature, and they describe requirements for scalability and replicability. Data was collected from ongoing European smart grid demonstration projects through the use of an elaborated questionnaire on the identified factors. Which allowed to quantify the status quo to what extent projects have taken these factors into account. Dew to their nature the derived factors can be categorized in technical, economic and regulatory & stakeholder related factor areas The obtained results allowed the identification of barriers, i.e. limitations regarding the scalability and replicability of smart grid projects. In particular projects face barriers regarding the absence of standards, the physical limits of the existing infrastructure, the absence of cost-benefit analyses, the neglect of varying macro-economic factors, stakeholder involvement and from the dependency of projects on regional or national regulatory frameworks and market designs. info:eu-repo/semantics/publishedVersion

This work proposes a methodology for predicting the typical daily load profile of electricity usage based on static data obtained from surveys. The methodology intends to: (1) determine consumer segments based on the metering data using the k-means clustering algorithm, (2) correlate survey data to the segments, and (3) develop statistical and machine learning classification models to predict the demand profile of the consumers. The developed classification models contribute to make the study and planning of demand side management programs easier, provide means for studying the impact of alternative tariff setting methods and generate useful knowledge for policy makers.

The potential of offshore wind energy has been commonly recognized and explored globally. Many countries have implemented and planned offshore wind farms to meet their increasing electricity demands and public environmental appeals, especially in Europe. With relatively less space limitation, an offshore wind farm could have a capacity rating to hundreds of MWs or even GWs that is large enough to compete with conventional power plants. Thus the impacts of a large offshore wind farm on power system operation and security should be thoroughly studied and understood. This paper investigates the impacts of integrating a large-scale offshore wind farm into the transmission system of a power grid through VSC-HVDC connection. The concerns are focused on steady-state voltage stability, dynamic voltage stability and transient angle stability. Simulation results based on an exemplary power system are presented and analyzed.