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AbstractThe wave load on potential offshore wind farms off Norway is studied by the use of a numerical wave refraction model. The model estimates trajectories of wave energy (rays) for waves propagating in water with varying surface velocity. The calculations indicate that for southerly and southwesterly winds the majority of shoreward propagating waves will converge in the coastal area off southwestern Norway. For offshore wave propagation directions equal to 180o and 210o, respectively 88% and 72% of the shoreward propagating rays approaches land south of Ålesund on the western part of Norway. For westerly and northerly winds the distributions are approximately uniform. It is further found that in the case of southerly or southwesterly winds, waves approach- ing the southern part of Norway are frequently misaligned with the wind. This will result in an increased bending moment of the masts. For offshore wave propagation direction between 180o and 240o the calculations indicate that approximately 24% of the rays reaching the coast of Norway along its southwestern part deviates by more than 45o of offshore propagation direction.

Currently, the PV solar sector represents approx. 2% of worldwide annual electricity production (https://webstore.iea.org/world-energy-outlook-2018), and therefore, is just at the verge of becoming visible in most countries. As the PV sector becomes increasingly visible to the next order of magnitude sometime in future, representing 20% in the electricity mix and beyond, it is now a good time to discuss reliability, predictability, and performance of PV power plants and as a consequence, the improvement potential for financial returns. Building on this train of thought, this article will provide a short introduction of PV power plant risks, predominantly related to technical performance. The question of risk mitigation measures will then be discussed: On the one side, quality assurance is a viable risk mitigation measure. However, even with quality assurance measures implemented, there are limitations when it comes to backstopping financial losses in the event that the performance deteriorates more than predicted and warranted by the manufacturers, or if the manufacturers or EPC's are no longer in business when incidental power degrades beyond calculated limits. Insurance solutions seem to provide an additional risk mitigation measure. Most insurance solutions on the market, however, only cover against externally induced risk exposures, e.g. severe weather, theft. Most of these insurance solutions follow a certain minimum standard. A few insurance products offer performance insurances where general cover is less standardized. All this triggers the question of how to look at insurance solutions. The interests of an insurance company are generally different than those of the insured stakeholders. These different viewpoints will be discussed, and selected warranty and insurance aspects will be considered. Recently, approximately 3500 insurance claim cases were statistically analyzed (http://www.pvstatlab.rwth-aachen.de/index.php/PVScan-project.html). Selected results of this analysis will be discussed. The article closes with an outlook of how insurers can likewise mitigate their risk exposure − in the end, insurers are only as good as the balance of the solvency resulting from their business model, or in the terminology of the insurance sector, the loss ratio must be at an acceptable level. This is where IECRE, the IEC System for Certification to Standards Relating to Equipment for Use in Renewable Energy Applications (https://www.iecre.org/), offering an international standard for certification − and in future − a rating system for PV power plants on a system level comes into play.

Abstract GeV–TeV gamma-rays and PeV–EeV neutrino backgrounds provide a unique window on the nature of the ultra-high-energy cosmic rays (UHECRs). We discuss the implications of the recent Fermi-LAT data regarding the extragalactic gamma-ray background and related estimates of the contribution of point sources as well as IceCube neutrino data on the origin of the UHECRs. We calculate the diffuse flux of cosmogenic γ-rays and neutrinos produced by the UHECRs and derive constraints on the possible cosmological evolution of UHECR sources. In particular, we show that the mixed-composition scenario considered in Globus et al., which is in agreement with both (i) Auger measurements of the energy spectrum and composition up to the highest energies and (ii) the ankle-like feature in the light component detected by KASCADE-Grande, is compatible with both the Fermi-LAT measurements and with current IceCube limits. We also discuss the possibility for future experiments to detect associated cosmogenic neutrinos and further constrain the UHECR models, including possible subdominant UHECR proton sources.

AbstractAn automatic pump is developed using low water‐head hydropower. The energy conversion efficiency η of the gas‐water energy conversion equipment is the focus. In this equipment, low‐head water normally drains to the vertical downcomer. When water particles separate via gravity, a vacuum is generated, and air is mixed into the water spontaneously. High‐pressure gas is ultimately produced at the end of the pipe. To discuss the effects of the air intake pipe diameter, river drop and water flow rate on η, a full‐scale experiment is conducted, and an analytical solution based on the separation of water particles is derived. The air intake pipe diameter has almost no effect on η, but η changes dramatically as the water flow rate varies. Meanwhile, η initially increases and then decreases as the river drop increases. These findings enable the development of a method for low water‐head hydropower utilization.

One of the greatest challenges facing the recycling of Al-based alloys is handling Fe incorporation. The formation of Fe-rich phases has negative impacts on the mechanical behavior and may limit the usage of recycled alloys. In this context, V addition is regarded as a potential solution since it can inhibit the formation of such phases. However, the microstructure evolution of V-modified Al-based alloys is not fully understood, especially when different solidification cooling regimes are considered. Thus, this work investigates the microstructure and tensile properties of an Al-7Si-1Fe [wt.%] alloy modified with a 0.5 wt.%V addition. Directionally solidified samples were produced and subjected to microstructure analysis and tensile tests. It was found that the addition of V reduces the fraction of β-AlFeSi particles because of the formation of new V-rich phases. This was determinant to improve the tensile properties for faster cooling conditions during solidification. For moderate and slow cooling regimes, however, the V-containing alloy had a less favorable mechanical behavior due to the formation of larger β-AlFeSi particles. Finally, quantitative relationships are proposed for the prediction of tensile properties from microstructural parameters using multiple linear regression analysis.

Black Carbon (BC) is an absorbing aerosol which has significant impact on the Earth - Atmosphere radiation balance and hence on climate. The variation of BC mass concentration and contribution of fossil fuel and biomass burning have been investigated over the Indian ocean sector of the Southern Ocean during austral summer. BC mass was in the range of 300-500 ng m-3 between 23.3oS to 24.5oS followed by decrease in BC to 150 ng m-3 as moving to higher southern latitudes till 41oS latitude. An increase in BC mass from 250 to 450 ng m-3 was found between 41 and 50oS due to trap of air masses by cyclonic wind and transport of aerosols from the southern part of African and eastern Madagascar regions. Higher BC concentration (250-350 ng m-3) was observed in the latitude range of 57-60oS which can be attributed to convergence of north-westerly and south-easterly winds. The dominant contributor to BC was fossil fuel, which was > 80% during half of the total observations, while > 20% biomass burning contributed to one fifth of observations. The coastal Antarctic region showed higher BC mass concentration with mixed type of contributions of biomass and fossil fuel. Such accumulation of BC near the Antarctic coast can have a crucial impact on the sea-ice albedo which significantly affect the Antarctic climate system locally and global climate in general.

Non-thermal plasma (NTP) has been introduced over the past several years as a promising method for nitrogen oxide (NOx) removal. The intent, when using NTP, is to selectively transfer input electrical energy to the electrons, and to not expend this in heating the entire gas stream, which generates free radicals through collisions, and promotes the desired chemical changes in the exhaust gases. The generated active species react with the pollutant molecules and decompose them. This paper reviews and summarizes relevant literature regarding various aspects of the application of NTP technology on NOx removal from exhaust gases. A comprehensive description of available scientific literature on NOx removal using NTP technology is presented, including various types of NTP, e.g. dielectric barrier discharge, corona discharge and electron beam. Furthermore, the combination of NTP with catalyst and adsorbent for better NOx removal efficiency is presented in detail. The removal of NOx from both simulated gases and real diesel engines is also considered in this review paper. As NTP is a new technique and is not yet commercialized, there is a need for more studies to be performed in this field.