Optimization Models for islanded micro-grids: A comparative analysis between linear programming and mixed integer programming

This paper presents a comparison of optimization methods applied to islanded micro-grids including renewable energy sources, diesel generators and battery energy storage systems. In particular, a comparative analysis between an optimization model based on linear programming and a model based on mixed integer programming has been carried out. The general formulation of these models has been presented and applied to a real case study micro-grid installed in Somalia. The case study is an islanded micro-grid supplying the city of Garowe by means of a hybrid power plant, consisting of diesel generators, photovoltaic systems and batteries. In both models the optimization is based on load demand and renewable energy production forecast. The optimized control of the battery state of charge, of the spinning reserve and diesel generators allows harvesting as much renewable power as possible or to minimize the use of fossil fuels in energy production

Distributed Storage for the Provision of Ancillary Services to the Main Grid: Project PRESTO

AbstractThis paper presents the three-year PRESTO research project (2013-2015). PRESTO is a self-funded project developed by the Department of Energy of Politecnico di Milano in cooperation with FIAMM Storage, Elvi Energy and MCM Energy Lab (an Italian spin-off). Within the project, experimental tests and numerical simulations were performed in order to evaluate the effectiveness of an Energy Storage System (ESS) in the provision of ancillary services to the main grid. This paper focuses specifically on the experimental and numerical analyses carried out in the project to develop an innovative control law for the primary frequency regulation, able to maximize the performances of the regulating service and effectively manage the ESS state of charge

Harmonic Analysis of Output Filters for Grid Connected Converters in Battery Energy Storage Systems

Battery Energy Storage Systems, as well as many distributed generation systems, use voltage source inverter as interface with the grid. These converters require a filtering section to reduce current harmonics injected to the grid. Usually, harmonic filter is a series inductance connected between grid and inverter. Higher order filters can provide better harmonic attenuation at lower switching frequency and reduce filter size, with potential benefits for high power applications. This paper deals with the sizing and the frequency response of three different harmonic filters suitable to reduce the ripple in the grid current waveform. Dynamic simulations of a 100 kW Battery Energy Storage System highlight the better performance of high order filters

<i>Saccharomyces cerevisiae</i> as a Tool for Studying Mutations in Nuclear Genes Involved in Diseases Caused by Mitochondrial DNA Instability

Mitochondrial DNA (mtDNA) maintenance is critical for oxidative phosphorylation (OXPHOS) since some subunits of the respiratory chain complexes are mitochondrially encoded. Pathological mutations in nuclear genes involved in the mtDNA metabolism may result in a quantitative decrease in mtDNA levels, referred to as mtDNA depletion, or in qualitative defects in mtDNA, especially in multiple deletions. Since, in the last decade, most of the novel mutations have been identified through whole-exome sequencing, it is crucial to confirm the pathogenicity by functional analysis in the appropriate model systems. Among these, the yeast Saccharomyces cerevisiae has proved to be a good model for studying mutations associated with mtDNA instability. This review focuses on the use of yeast for evaluating the pathogenicity of mutations in six genes, MPV17/SYM1, MRM2/MRM2, OPA1/MGM1, POLG/MIP1, RRM2B/RNR2, and SLC25A4/AAC2, all associated with mtDNA depletion or multiple deletions. We highlight the techniques used to construct a specific model and to measure the mtDNA instability as well as the main results obtained. We then report the contribution that yeast has given in understanding the pathogenic mechanisms of the mutant variants, in finding the genetic suppressors of the mitochondrial defects and in the discovery of molecules able to improve the mtDNA stability

A yeast-based repurposing approach revealed modulation of dNTP pool as a therapeutic target to treat mitochondrial DNA depletion syndromes

Mitochondrial DNA Depletion Syndromes (MDS) are a group of clinically heterogenous and often severe diseases characterized by a reduction of the mitochondrial DNA (mtDNA) copy number in affected tissues. There are still no satisfactory therapies and, since mitochondrial diseases, taken individually, are rare, therapeutic strategies with potential general applicability to several mitochondrial diseases would be desirable. Yeast has proved to be an excellent model for the study of the mechanisms underlying mitochondrial pathologies and also for the discovery of new therapies thanks to the development of a high–throughput yeast-based assay. We identified ten drugs active against MPV17 disorder modelled in yeast, whose homologous gene is SYM1. MPV17/SYM1 encodes a non-selective channel in the inner mitochondrial membrane whose physiological role and nature of the cargo remains elusive. Recessive mutations in this gene cause a hepatocerebral form of MDS and Navajo neurohepatopathy. All the ten molecules identified determine a concomitant increase of both mitochondrial dNTP pool and mtDNA stability strongly suggesting that the reduced availability of DNA synthesis precursors is the cause of the mtDNA deletion/depletion in Sym1 deficiency. We also assessed the effect of these molecules on mtDNA stability of two additional MDS yeast models characterized by mutations in MIP1 and RNR2, orthologs of the human genes POLG and RRM2B, respectively, extending the potential use of these drugs to other MDS patients. As a drug repurposing approach of FDA-approved drugs was used, this could speed up a possible clinical use of the drugs