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This paper describes a new generator's PSS (power system stabilizer) design method. A multi input PSS which is designed by considering several power flow conditions is utilized to achieve a better robustness over a wide range of operating conditions and oscillation frequency, instead of a conventional single input PSS. The parameters of the optimized PSS are obtained by minimizing a performance index based on eigenvalues that shows steady state stability of the power system The method utilizes eigenvalue sensitivities associated with PSS parameters for each pattern of multiple power flow conditions. Simulation results show that the proposed PSS provides a better performance than the conventional PSS.

Gender-specific perceptions and needs are critical to better understanding climate change adaptation capacities of local smallholder communities in Africa and elsewhere. As many rural agricultural practices are heavily impacted by male-centered traditional customs and mores, gender dimensions can determine the level of success for policy interventions. To better understand how and what gender dimensions can be important factors for farmer’s climate change adaptations, this study attempts to examine smallholder farmers’ adaptation needs and perspectives in Ghana’s Upper East Region. A focus group discussion and a questionnaire survey were conducted among 200 smallholder farmers. We found that the female respondents, who mostly belonged to low/middle-income groups, emphasized their urgent need for financial support to improve their income. They needed more farmland as 94% of them had only less than 5 acres to farm. In addition, 91% of the female respondents expressed the importance of being connected to farmers’ mutual-help groups to share information about common farming needs. We also found gender-specific needs for extension services, farm inputs, climate information, mechanization, and infrastructure. Regarding access to resources, the women respondents had little interest in investing more in farming as the land they borrowed could be taken away by male owners. The study recommends the need for gender-specific support initiatives that prioritize social protection and gender equality.

The purpose of this paper is to provide an overview of the engineering methods, tools, design solutions and verification methods used in the design of HVDC converter substations subject to acoustic requirements. The sound generation section of the paper describes how the sound power level radiated from electrical components can be calculated based on the load. The sound propagation section describes how the sources affect the sound pressure level at emission points of interest. A method to break down the acoustic requirement to the component level and practical studies to verify the concordance with the requirements are also illustrated. Different solutions for screening and absorption are described as well as measurement methods. The paper also describes a working method used to fulfil outdoor acoustic requirements. >

AbstractOcean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed “tropicalization”. A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral‐dominated systems. We conducted field surveys and in situ transplants at natural analogues for present and future conditions under (i) ocean warming and (ii) both ocean warming and acidification at a transition zone between kelp and coral‐dominated ecosystems. We show that increased herbivory by warm‐water fishes exacerbates kelp forest loss and that ocean acidification negates any benefits of warming for range extending tropical corals growth and physiology at temperate latitudes. Our data show that, as the combined effects of ocean acidification and warming ratchet up, marine coastal ecosystems lose kelp forests but do not gain scleractinian corals. Ocean acidification plus warming leads to overall habitat loss and a shift to simple turf‐dominated ecosystems, rather than the complex coral‐dominated tropicalized systems often seen with warming alone. Simplification of marine habitats by increased CO2 levels cascades through the ecosystem and could have severe consequences for the provision of goods and services.

In arid to semi-arid regions, vulnerability to climate change combined with the overexploitation of water resources is jeopardizing food security. In the Souss-Massa region in central Morocco, the rural population relies on growing olives for a living. The management of these orchards is mostly traditional under rainfed irrigation, which induces a high level of dependence on climate variability. In the present study, we investigate the long-term trends of the relationship between the observed olive yields and global climate patterns during the period 1973–2014. We apply lagged Spearman’s correlations and cross-wavelet analysis to detect the potential influence of El Niño-southern oscillation (ENSO), the Indian Ocean Dipole (IOD), North Atlantic oscillation (NAO) and Pacific decadal oscillation (PDO) on the yield variability of olive orchards. The results of a Mann-Kendall test show a statistically significant decreasing trend in olive yields during the studied period. Statistically significant negative correlations were observed for (lag = −1) with spring and summer NINO 3.4 and with summer and autumn PDO. No statistically significant correlations between olive yields and NAO and IOD were observed. The results of wavelet coherence between annual olive yields and PDO and ENSO revealed that the highest values of power spectrum coherence occurred during the (lag = 0) spring PDO and (lag = −1) spring ENSO, both with an antiphase relationship. During the studied period, the extreme events of El Niña and El Niño years corresponded to below average yields.

Indonesia is the largest producer of palm oil; it is essential to manage its palm oil industry in a sustainable manner through swapping the oil palm plantation in peatland to mineral soil to reduce the greenhouse gas emissions. This study employed the latest spatial data using the ArcGIS software to analyze the potential area for the land swap option and to calculate the potential reduction in greenhouse gas emissions in Kalimantan, Indonesia. There are 1.08 million ha of oil palm in peatland, while 0.64 million ha of the area in mineral soil under the convertible production forest have the potential for land swapping. Via the land-swap option, emission reductions of 65.43% (from 979.05 MtCO2eq to 336.64 MtCO2eq) for the calculation period of 25 years and up to 61.19% (from 2147.81 MtCO2eq to 833.67 MtCO2eq) for that of 50 years is possible compared to the initial condition. The land swap will also increase the production of fresh fruit bunch (FFB) by 17.16% per year because the productivity of FFB in mineral soil is higher than that of the peatland. Considering that land swaps are costly, policymakers and stakeholders must collaborate to execute the land-swap option for the sustainability of Indonesian palm oil.

Abstract The objective of this study was to investigate the effects of particle size reduction and solubilization on biogas production from food waste (FW). To clarify the effects of volatile fatty acids (VFAs) in the digestion process, the relationship between particle size and VFA accumulation was investigated in detail. For this purpose, substrates of various particle sizes were prepared by bead milling to support hydrolysis. Batch anaerobic digestion experiments were carried out using these pretreated substrates at mesophilic temperature for a period of 16 days. The results of pretreatment showed that the mean particle size (MPS) of substrates ground with a bead mill decreased from 0.843 to 0.391 mm, and solubilization accounted for approximately 40% of the total chemical oxygen demand (total COD) for grinding pretreatment by bead milling. Anaerobic digestion batch experiments revealed that MPS reduced by bead milling at 1000 rpm improved methane yield by 28% compared with disposer treatment. Moreover, this may have increased microbial degradation during the VFA production process with increasing total number of revolutions (operation time × revolutions per minute). However, excessive reduction of the particle size of the substrate resulted in VFA accumulation, decreased methane production, and decreased solubilization in the anaerobic digestion process. These results suggest that optimized reduction of the particle size of the substrate in conjunction with optimized microbial growth could improve the methane yield in anaerobic digestion processes.

Abstract Owing to the high penetration of renewable energy sources, power systems require more flexibility to respond to the fluctuation of variable renewable energy sources. However, flexibility provision by distributed energy resources (DERs) installed on the demand side is a cost-effective measure. In this study, we proposed a scheme that utilizes time-of-use (TOU) electricity rates as an incentive to encourage residential prosumers to provide more flexibility by controlling the DERs. In particular, we developed an energy management system model that applies model predictive control. The TOU rates were designed by an aggregator who traded with markets and prosumers. The DERs of residential prosumers were fuel cells with combined heat and power, CO2 heat pump water heaters, or batteries. Numerical simulations using measured energy demand and insolation data were performed to evaluate the performance of the developed model. According to the results, the developed model could integrate prediction errors and provide flexibility to the grid. Finally, the economies of the aggregator and prosumers were also evaluated.