• Energy Research

This paper presents an improvement of the tuning process of the holistic control published by the authors in previous research to achieve a seamless transition among three operation mode changes and load transients. The proposed tuning approach reveals an improvement in the energy consumption of the Battery Energy Storage System (BESS) during all operation mode transients compared to the holistic control. For this aim, the system addressed is a BESS with the capability to ride through three operation modes of interest: the grid-connected mode as an inverter, the grid-connected mode as a rectifier, and the islanded operation mode. The LCL filter design by using the Butterworth polynomial approach is presented in more detail, and its smooth inherent transient response is preserved when the tuning of the controller gains is carried out by using the same polynomial approach but now including the integral action within the Butterworth polynomial. To reveal the reduction in energy consumption, the closed-loop transfer functions of each mode were used to compare the previous holistic control and this new one named by the authors as the “improved holistic control”. The closed-loop system fulfills the frequency and voltage thresholds of the IEEE 1547-2018 standard seamlessly. The simulation runs were conducted on the PSCAD/EMTDC to evaluate the seamless transition among the operation mode changes and load steps. The experimental results in a 617 W, 120 VL−L three-phase converter prototype are included to demonstrate the validity of the improved holistic control.

Abstract This article reports on changes in climate science, social science, public administration, and policymaking over the past twenty-five years. It responds to Gene I. Rochlin's “retrospective examination” of energy research and the social sciences. In 2014, we find that social scientists are still disadvantaged by policymaker biases and inaccessible deliberative systems, but also better poised to conduct original humanistic energy research and produce targeted social change interventions. We review promising social scientific advancements, particularly in the realm of citizen action research. We conclude with the case study of evidence-based practice, a model from the health field that illustrates how climate change and energy research, practice, and policymaking could benefit from the inclusion of social science perspectives and methods.

Electrification of the transport sector and massive installation of renewables are seen as two cornerstones for achieving a carbon neutral energy system. Nevertheless, uncontrolled electric vehicle charge combined with fluctuating energy production could induce power quality issues and system inefficiencies, causing an opposite outcome. Thus, in order to make sure that the energy system could benefit from electric mobility and renewable energy sources installation, proper design and control strategy of the charging stations is crucial. The aim of this study is to implement an optimal design methodology for an Electric Vehicle charging station located at a workplace. PV peak power, Electric Energy Storage capacity with retired Electric Vehicle batteries and number of charging columns to install are optimally defined targeting the carbon neutrality of the charging station operation. Two different charging strategy are implemented and compared to quantify the influence of the control approach on the final optimal charging station configuration. Moreover, energy demand and production uncertainties are taken into account in the production of the input data. The obtained results suggest that an optimal control strategy allows to have always a greater emission reduction and to downsize the PV and Electric Energy Storage capacity needed to achieve the carbon neutrality of the EV charging process.

By using a non-local model, fluid simulations can capture kinetic effects in the parallel electron heat-flux better than is possible using flux limiters in the usual diffusive models. Non-local and diffusive models are compared using a test case representative of an ELM crash in the JET SOL, simulated in one dimension. The non-local model shows substantially enhanced electron temperature gradients, which cannot be achieved using a flux limiter. The performance of the implementation, in the BOUT++ framework, is also analysed to demonstrate its suitability for application in three-dimensional simulations of turbulent transport in the SOL. Comment: Accepted version. Corrected normalization in (6). This is an author-created, un-copyedited version of an article accepted for publication in Plasma Physics and Controlled Fusion. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.1088/0741-3335/55/5/055009

It is easy for adversaries to mount node replication attacks due to the unattended nature of wireless sensor networks. In several replica node detection schemes, witness nodes fail to work before replicas are detected due to the lack of effective random verification. This paper presents a novel distributed detection protocol to counteract node replication attacks. Our scheme distributes node location information to multiple randomly selected cells and then linear-multicasts the information for verification from the localized cells. Simulation results show that the proposed protocol improves detection efficiency compared with various existing protocols and prolongs the lifetime of the overall network.

Green spaces require frequent watering, increasing the pressure on water resources. The use of native plants in landscaping reduces the risks of biological contamination, contributing to preservation of Brazilian biodiversity and provides the value of sustainability in urban green areas. Of these native plants, a restricted number are native lianas which are adapted to Brazilian climate and available on the market. In this regard, the selection and recommending of native plants which are efficient in use of water for planting in urban areas constitute an effective strategy for conservation of water resources. Thus, the purpose of this study was to evaluate the growth and development of I. cairica plants submitted to water deficit. For a period of 100 days after transplanting, plants of this species were grown with watered at pot capacity except for 30 days (from the 30th to the 60th day) when four water deficits (25, 50, 75 and 100% pot capacity) were applied. During all regimes of water deficiency applied, there was a 100% survival rate. After reestablishment of water regime the species recovered its growth, even that was submitted to the 25% of pot capacity. It testify that I. cairica is resistant to low water availability. Os espaços verdes necessitam de irrigações freqüentes, aumentando a pressão sobre os recursos hídricos. A utilização de plantas nativas em paisagismo diminui os riscos de contaminação biológica, contribui para a preservação da biodiversidade brasileira e propicia a sua valorização sustentável em áreas verdes. Destas, um número restrito são de lianas nativas aclimatadas e disponíveis no mercado. Nesse sentido, a seleção e indicação de plantas nativas eficientes no uso da água para implantação em paisagismo constituem-se uma estratégia eficaz na conservação dos recursos hídricos. Assim, buscou-se avaliar o crescimento e desenvolvimento de plantas de Ipomoea cairica submetidas a déficit hídrico. Ao longo de 100 dias após o transplante, plantas dessa espécie foram cultivadas com irrigação em capacidade de vaso, exceto por 30 dias (do 31º ao 60º dia) quando se aplicou quatro regimes hídricos (25, 50, 75 e 100% de capacidade de vaso). Durante o período de deficiência hídrica, houve 100% de sobrevivência, em todos os regimes hídricos aplicados. Após o restabelecimento hídrico, a espécie retomou seu crescimento, mesmo a que foi submetida a 25% da capacidade de vaso. Isto prova que I. cairica é resistente a baixa disponibilidade hídrica.

Abstract Biome boundaries are expected to be sensitive to changes in climate and disturbance, because it is here that ecological communities are at environmental, ecological or disturbance limits. Using palaeoecology to study ecosystem dynamics at biome boundaries provides opportunities for understanding ecosystem resilience or sensitivity at ecologically meaningful timescales, and under varying climatic and disturbance conditions. The fynbos biome is a megadiverse Mediterranean type shrubland, found only in South Africa, that is threatened by climate change, land-use change and invasion by alien species. We used palaeoecological records from the semi-arid and mesic boundaries of the fynbos biome to test hypotheses regarding ecosystem resilience over timescales of centuries to millennia. We hypothesised that fynbos would expand at its mesic boundary at the expense of afrotemperate forest under drier and / or more fire prone conditions. In contrast, we hypothesised that at the semi-arid boundary, fynbos would expand at the expense of succulent karoo under wetter and cooler and / or more fire-prone conditions. Contrary to our expectations, the fossil pollen record at both biome boundaries showed remarkable stability at centennial - millennial timescales. To explain our results, we generated new hypotheses exploring possible mechanisms that might confer resilience. At the mesic (temperate) boundary, we suggest that decreased seasonality of rainfall during drier phases favoured fire and fynbos persistence, while in wetter periods, increased seasonality of rainfall resulted in enhanced summer drought stress, inhibiting forest expansion. At this boundary, internal reorganisation from grassy to proteoid fynbos states conferred resilience through resistance. At the succulent karoo boundary, we suggest that increased aridity was offset by less seasonality of rainfall, which enhanced biomass and allowed fire to persist, favouring persistence of fynbos. At this boundary, fynbos sensu stricto retreated during arid phases but recovered during climate amelioration, consistent with resilience through recovery. In both cases, this mega-diverse, disturbance-adapted flora provided a range of traits that enabled fynbos to persist despite environmental perturbation. Our findings agree with general observations that for ecosystems in regions of ample resource availability (i.e. at the mesic boundary), biotic interactions and disturbance tend to become more important in ecosystem dynamics, whereas in regions of scarce resources (in this case water scarcity at the semi-arid boundary) abiotic stress is more important. Our findings contribute to debates over the mechanisms that confer resistance and resilience to environmental change. Understanding and conserving the processes and mechanisms underpinning its resilience will be critical to effective conservation planning.

Abstract Si-wafers for solar cells were cast in a size of 50 × 46 × 0.5 mm 3 by a direct casting method. A graphite mold coated by boron nitride (BN) powder was used in order to prevent the reaction between carbon and the molten silicon. Without any coating, the reaction of the Si melt to the graphite mold was very severe. In the case of BN coating, SiC was formed in the shape of tiny islands on the surface of the Si wafer by the reaction between the Si-melt and the carbon of the graphite mold at high temperature. The grain size was about 1 mm. The efficiency of the Si solar cell was about 0.5% under AM1.5 conditions. It was lower than that of a Si solar cell fabricated with a common single- (sc, 3.0%) and poly-crystalline (pc, 1.0%) Si wafer, which showed much lower efficiency than that of other commercial pc- or sc-Si solar cell (10–15%).

Abstract We study the propagation of combustion waves through porous samples in which two reactions occur. The first is a gasless solid-solid reaction between two solid species in the porous solid matrix to form a solid product, while the second is a solid-gas reaction in which gas delivered to the reaction site through the pores of the sample reacts with one of the solid species to form both solid and gaseous products. We consider the case of coflow filtration, in which the direction of gas flow is the same as the direction of propagation. The gas, consisting of both chemically active and inert components, filters to the reaction zone through the product region thus transferring heat from the high-temperature products to the unburned mixture. Using kinetics motivated by large activation energy considerations we determine the structure of a uniformly propagating combustion wave and, in particular, such important characteristics as the propagation velocity of the wave, the burning temperature and the compo...