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The oxidation of water is essential to the sustainable production of fuels using sunlight or electricity, but designing active, stable and earth-abundant catalysts for the reaction is challenging. Now, a complex containing five iron atoms is shown to efficiently oxidize water by mimicking key features of the oxygen-evolving complex in green plants.

Forecasting and acquiring of short-term demand for frequency control reserve is a significant driver of cost for transmission system operators (TSO). A method is presented of identifying the significance of different factors by analyzing the correlation between historical data of actual reserve activation and renewable energy feed-ins, planned and unplanned power plant outages, vertical load, renewable energy forecasting errors and balancing energy provision. Application of this method shows that balancing energy has a moderate influence on the activation of secondary reserve. It has also been found that for minute reserves, corresponding activation of secondary reserves shows weak influence. Quarter-hourly prior activation of reserves also has a significant influence on the demand for control power. The analysis shows insignificant correlation between the investigated factors and the demand for secondary control reserves and minute reserves.

This work addresses the problem of energy consumption time series forecasting. In our approach, a set of time series containing energy consumption data is used to train a single, parameterised prediction model that can be used to predict future values for all the input time series. As a result, the proposed method is able to learn the common behaviour of all time series in the set (i.e., a fingerprint) and use this knowledge to perform the prediction task, and to explain this common behaviour as an algebraic formula. To that end, we use symbolic regression methods trained with both single- and multi-objective algorithms. Experimental results validate this approach to learn and model shared properties of different time series, which can then be used to obtain a generalised regression model encapsulating the global behaviour of different energy consumption time series.

An analysis of scientific publications on solar energy was conducted to determine whether public interest in the subject is mirrored by more intense research in the area. To this end, the research published by Spain and Germany, the two EU countries with the highest installed photovoltaic capacity, was analyzed based on Web of Science data. The results show that: solar output has risen substantially; solar research has a greater impact (measured in terms of citations) than publications on other renewables such as wind power; scientific production on solar energy is high in Germany and Spain, which together account for 51% of the total in the EU-27; the pattern of topics researched in the two countries is very similar; and their international collaboration is more intense than the world average and higher than in countries such as the USA, China or Japan. Collaboration between them is likewise intense. The main conclusion is the divergence in Germany and Spain between solar energy demand/output growth, being exponential, and the growth of research papers on the subject, which is linear

This research examines the economic implications of different designs for a national low carbon fuel standard (NLCFS) for the road transportation sector. A NLCFS based on the average Carbon Intensity (CI) of all fuels sold generates an incentive for fuel suppliers to reduce the measured CI of their fuels. The economic impacts are determined by the availability of low carbon fuels, estimates of which can vary widely. Also important are the compliance path, reference level CI, and the design of the credit system, particularly the opportunities for trading and banking. To quantitatively examine the implications of a NLCFS, we created the Transportation Regulation and Credit Trading (TRACT) Model. With TRACT, we model a NLCFS credit trading system among profit maximizing fuel suppliers for light- and heavy-duty vehicle fuel use for the United States from 2012 to 2030. We find that credit trading across gasoline and diesel fuel markets can lower the average costs of carbon reductions by an insignificant amount to 98% depending on forecasts of biofuel supplies and carbon intensities. Adding banking of credits on top of trading can further lower the average cost of carbon reductions by 5%–9% and greatly reduce year-to-year fluctuations in credit prices.

AbstractThe aim of this work is to characterize a 5MWe Fresnel solar power plant at different areas of Algeria Sahara. These areas have been chosen for comparison by shifting the plant in different locations; namely HassiR’mel, Tamanrasset, Beni-Abbes, and El Oued. Theoretical modeling has allowed the determination of mirror optimum number to avoid shadowing effects, blocking and cosine effect. Mirror optimum number was estimated at 40 mirrors. Furthermore, a simulation was carried out on a time scale, regarding insolation, “field” and “receiver” systems. The simulation results are depicted on annual basis. Efficiency, annual energy generation and the cost per kWh are evaluated. Indeed, the calculation of efficiency differs from a site to another with values of 15.7%, 11.8%, 11.6% and 10.4%, respectively for Tamanrasset, El Oued, Beni-Abbes, HassiR’mel. Thermal performances, technical and economic results have been also evaluated for the said sites.

The division of return stroke current among the arresters and groundings of two unenergized test distribution lines, one horizontally configured and the other vertically configured, was studied at the International Center for Lightning Research and Testing in Florida. The division of return stroke currents for the vertically configured line was initially similar to the division on the horizontally configured line: at the time the return stroke current reached peak value (after one microsecond, or so) the two closest arresters/grounds on both lines passed about 90% of the total current. However, the time during which the return stroke current flowed primarily through the closest arresters to the neutral conductor was significantly shorter on the vertically configured line. On that line, the arrester current was about equally divided among all four arresters after several tens of microseconds. The arrester current division as a function of time measured on the vertical line was successfully modeled using the published VI-characteristic, while the division on the horizontal line after some tens of microseconds was only successfully modeled if the residual voltage of the two arresters closest to the current injection point was reduced by 20%. Based on the triggered lightning current division observed on our line, the minimum energy absorbed in each of the two arresters closest to the strike point during a typical natural first stroke is estimated to be 40 kJ.

SignificanceMarginal emissions of CO2from the electricity sector are critical for evaluating many climate policies. We provide estimates of marginal CO2emissions for electricity use in the United States that vary by region, hour of day, and year to year. Despite a decrease in average emissions over the last decade, marginal emissions have increased. We apply our estimates to an analysis of the Biden administration’s target of having electric vehicles make up 50% of new vehicle purchases by 2030. We find that, without significant and concurrent changes to the electricity sector far more substantial than those over the last decade, the increase in electricity emissions is likely to offset more than half the emission reductions from having fewer gasoline-powered vehicles.