1,721,028 research outputs found
Performance and Thermal Analysis of Organic Photovoltaic Modules in Outdoor Conditions
No full textOrganic photovoltaic (OPV) modules are an emerging, innovative and low-cost solution to convert sunlight into electricity. Their flexibility and semi-transparency make OPV modules a suitable solution even in applications that cannot be based on traditional photovoltaic (PV) technologies. However, high ageing rate, short lifetime and low efficiency have limited their diffusion. This paper presents two outdoor test campaigns designed to assess and to compare with traditional silicon-based PV technologies the power output of OPV modules operating in real environmental conditions. OPV modules, as well as silicon-based PV modules, were operated at their maximum power point for several days: data collected demonstrated that OPV power output is slightly enhanced by the cells temperature at low irradiance, while at high irradiance the temperature coefficient of power is close to zero. Unlike silicon-based PV technologies, quite constant maximum power point voltage regardless the OPV cells temperature justifies the latter result
An Overview of Data-Driven Methods for the Online State of Charge Estimation
No full textIn the last years, the drift toward electric mobility and the need for renewable energy penetration placed the batteries and their control in a prominent position. A critical parameter for the battery management system (BMS) is the state of charge (SOC) of the battery pack. This paper gives an overview of the trends of the last 5 years of SOC estimation, using data-driven estimation methods. Due to the evolution of electronic materials and the abundance of available data, data-driven methods became popular and advantageous
A review on dynamic wireless charging systems
No full textThe increasing diffusion of Electric Vehicles (EVs) is driving academic and institutional research towards exploring different possible ways of charging vehicles in a fast, reliable and safe way. For this reason, Wireless Power Transfer (WPT) systems have recently been receiving a lot of attention in the academic literature. In particular, the Dynamic Wireless Charging (DWC) system is subject of the research of many teams because it gives to the vehicles the possibility to increase their driving range and decrease their battery size, which are the main problems of the EVs. This work reviews the two main structure used for the exchange of the power, the lumped and the stretched track. Furthermore, the main drawbacks and advantages of these two solutions are highlighted and a feasible application of them is discussed
Ground fault analysis in a microgrid scenario
No full textMicrogrids are based on the same grounding schemes generally adopted in the low voltage radial distribution grids. Unlike traditional distribution grids, in islanded microgrids the neutral grounding becomes a complex problem due to different operating configurations. All the electrical devices connected to the microgrid must be modeled to guarantee the access to the neutral point and their models have to be easy to include in the whole microgrid model. The Voltage Behind Reactance model is here introduced to meet these requirements in the synchronous machine modeling, and the complete model of a benchmark islanded microgrid is developed. The line-to-ground fault transient under different neutral grounding configuration are analyzed
Implementation of Nonlinear Controller to Improve DC Microgrid Stability: A Comparative Analysis of Sliding Mode Control Variants
Full text linkElectricity generation from sustainable renewable energy sources is constantly accelerating due to a rapid increase in demand from consumers. This requires an effective energy management and control system to fulfil the power demand without compromising the system’s performance. For this application, a nonlinear barrier sliding mode controller (BSMC) for a microgrid formed with PV, a fuel cell and an energy storage system comprising a battery and supercapacitor working in grid-connected mode is implemented. The advantages of the BSMC are twofold: The sliding surface oscillates in the close vicinity of zero by adapting an optimal gain value to ensure the smooth tracking of power to its references without overestimating the gains. Secondly, it exhibits a noticeable robustness to variations and disturbance, which is the bottleneck of the problem in a grid-connected mode. The stability of the presented controllers was analyzed with the Lyapunov stability criterion. Moreover, a comparison of the BSMC with sliding mode and supertwisting sliding mode controllers was carried out in MATLAB/Simulink (2020b) with real PV experimental data. The results and the numerical analysis verify the effectiveness of the BSMC in regulating the DC bus voltage in the presence of an external disturbance under varying conventional load and environmental conditions
Stability Analysis and Optimal Energy Management of a Stand-Alone Hybrid Micro-Grid
No full textThis paper presents the analysis of different spinning reserve calculation and allocation methods applied to an islanded hybrid power plant supplying the city of Garowe, in the North of Somalia. The preliminary analysis of the partially stochastic power flows, related to renewable energy system generators and load demand, allows to set minimum requirements to ensure the grid stability. Three criteria for the calculation of the spinning reserve and for its allocation on the generators involved in primary and secondary frequency regulation are here proposed and analyzed
Sustainable campus: Renovation of lighting fixtures for the reduction of CO2emissions
No full textThe work deals with the reduction of CO2emissions in school rooms of Politecnico di Milano, through the upgrading of lighting fixtures, in the context of the Città Studi Campus Sostenibile project. The aim is to provide an extensible intervention strategy to all the buildings of Politecnico di Milano and, more generally, to the School Construction, starting from the analysis of a limited number of buildings. Starting from the energy analysis of the current status in order to formulate the most appropriate methodologies for each classroom, three classifications have been suggested: age or generation, illuminance and energy. Two methods have been developed, with the purpose to design new efficient lighting systems. These strategies have led to a large reduction of consumption and, thus, to a reduction of CO2emissions improving also the lighting comfort
Characterization of Bifacial Photovoltaic Modules Based on I-V Curves Outdoor Measurement
Full text linkPhotovoltaic (PV) systems are well known for their simplicity of design, environmental friendliness, and low maintenance. Among the PV technologies, the behaviour of bifacial PV modules was studied in this research. Measurements of the I-V curves were carried out in the SolarTechLAB test facility at the Department of Energy of Politecnico di Milano, Italy, to detect the bifacial PV module behaviour, mainly in terms of power performance. In particular, I-V and power-voltage curves were measured at different tilt angles to consider several irradiance and cell temperature levels with both sides uncovered as well as with the back side covered. This last configuration was tested to evaluate the contribution of the rear face in the overall photoelectric conversion process. The comparison between the bifacial and monofacial operations highlighted that the power at the maximum power point of the bifacial operation can increase up to 13%. At the same time, leaving the rear face free allows for reducing the bifacial cell temperature up to about 6°C
Design and performance analysis of pads for dynamic wireless charging of EVs using the finite element method
Full text linkIncreasing problems of air pollution caused by petrol-fueled vehicles had a positive impact on the expanded use and acceptance of the electric vehicles (EVs). Currently, both academic and institutional researchers are conducting studies to explore alternative methods of charging vehicles in a fast, reliable, and safe way that would compensate for the drawbacks of the otherwise beneficial and sustainable EVs. The wireless power transfer (WPT) systems are now offered as a possible option. Another option is the dynamic wireless charging (DWC) system, which is considered the best application of a WPT system by many practitioners and researchers because it enables vehicles to increase their driving ranges and decrease their battery sizes, which are the main problems of the EVs. A DWC system is composed of many sub-systems that require different approaches for their design and optimization. The aim of this work is to find the most functional and optimal configuration of magnetic couplers for a DWC system. This was done by performing an investigation of the main magnetic couplers adopted by the system using Ansys®Maxwell as a finite element method software. The results were analyzed in detail to identify the best option. The values of the coupling coefficients have been obtained for every configuration examined. The results disclosed that the best trade-off between performance and economic feasibility is the DD-DDQ pad, which is characterized by the best values of coupling coefficient and misalignment tolerance, without the need for two power converters for each side, as in the DDQ-DDQ configuration
Outdoor Performance of Organic Photovoltaics: Comparative Analysis
Full text linkOrganic photovoltaic (OPV) solar cells represent an emerging and promising solution for low-cost clean energy production. Being flexible and semi-transparent and having significant advantages over conventional PV technologies, OPV modules represent an innovative solution even in applications that cannot be based on traditional PV systems. However, relatively low efficiencies, poor long-term stability, and thermal issues have so far prevented the commercialization of this technology. This paper describes two outdoor experimental campaigns that compared the operation of OPV modules with traditional PV modules—in particular crystalline silicon and copper–indium– selenium (CIS)—and assessed the OPV modules’ power generation potential in vertical installation and facing towards the cardinal directions
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