Identification of ESS Degradations Related to Their Uses in Micro-Grids: Application to a Building Lighting Network with VRLA Batteries

This paper presents a study about power profiles of micro-grid with highly intermittent sources and their impacts on energy storage system (ESS). The first step of the work consists in generating the ESS power profiles thanks to a new optimal sizing algorithm. Our approach allows to size the ESS and the renewable energy sources (RES) using a power/energy considerations to generate charging and discharging profiles regardless ESS specifics parameters. In a second step, we review the potential damages on Valves Regulated Lead Acid Batteries (VRLAB). This technology has been chosen because it is the most used ESS in case of stationary applications for urban MG with RES integration. We propose some criterion to quantify the batteries stresses generated by MG working operations. Therefore, we give recommendations to enhance the VRLAB lifetime in both micro-grid design and energy management. Our method has been applied to the photovoltaic production and lighting network consumption profiles of the LAAS-CNRS building integrated photovoltaic. We compare four possible configurations of ESS and RES: two determined thanks to Pareto optimisation method and two critical cases corresponding to the minimal and the maximal values of ESS size into all the possible configuration tested.

INSTRUMENT DEVELOPMENT OF MATHEMATICS LEARNING OUTCOMES BY THE RASCH MODEL IN ELEMENTARY SCHOOL TO SUPPORT THE IMPLEMENTATION OF THE 2013 CURRICULUM

This research aims to produce a grid design of mathematics learning outcomes instruments at the elementary school level in implementing the 2013 Curriculum. This research is expected to bring about the availability of grid design and supporting devices for the implementation of elementary school mathematics learning outcomes instruments. Output which obtained in this study is to help teachers in the development system of assessment that is sustainable, focussing on aspect of the analysis of the level of difficulty gains and the level of ability of students to use the model of Rasch. The sustainability implementation of Curriculum 2013, which may involve the heads of schools, teachers and students and the other relevant. In terms of the effectiveness, fostering sustainable used as the focus of a major system development as an instrument to validate test by the teacher and doing test try limited to the four schools in Palu. At the first stage, the design of instrument is carried out in the form of lattice and grain instruments, pieces of observation and questionnaires, test the construct, and the revision of the group of teachers and students of the school elementary grade IV. Result of test respondents (elementary School students in Palu) obtained that the point about the difficulty is the question number 26 (S26) with a value logit 2,08. While the matter of the most easily is the matter of number 3 (S3) with a value logit -1,84. Result output tables obtained information that does not exist grain matter which does not meet all the requirements fit (oufit MNSQ, outfit ZSTD and Pt Mean Corr) so that the point about including category fit or appropriate.

Hybrid RANS/LES of a generic high-lift aircraft configuration near maximum lift

Purpose The paper aims to assess the feasibility of locally turbulence-resolving flow simulations for a high-lift aircraft configuration near maximum lift. It addresses the aspects of proper grid design and explores the ability of the hybrid turbulence model and the numerical scheme to automatically select adequate modes in different flow regions. By comparison with experimental and numerical reference data, the study aims to provide insights into the predictive potential of the method for high-lift flows. Design/methodology/approach The paper applies numerical flow simulations using well-established tools such as DLR's (German Aerospace Center) TAU solver and the SOLAR grid generator to study “Improved Detached Delayed Eddy Simulations” of the Japan Aerospace Exploration Agency (JAXA) Standard Model at two angles of attack near maximum lift. The simulations apply a hybrid low-dissipation low-dispersion scheme and implicit time stepping with adequate temporal resolution. The simulation results, including pressure distributions and near-wall flow patterns, are assessed by comparison with experimental wind-tunnel data. Findings Apart from demonstrating the general feasibility of the numerical approach for complex high-lift flows, the results indicate somewhat improved maximum lift predictions compared to the Spalart–Allmaras model, which is consistent with a slightly closer agreement with measured pressure distributions and oil-flow pictures. However, the expected lift breakdown caused by an increasing inboard separation in the experiment is not well captured. Originality/value The study not only provides new insight into the feasibility and promising potential of hybrid turbulence-resolving methods for relevant high-lift aircraft flows but also indicates the need for further research on the numerical sensitivities, such as grid resolution or flow initialization.

Environmental Hotspot Assessment for a PV Mini-Grid Design: A Case Study for Malawi

The United Nations Sustainable Goal 7, access to affordable and clean energy, is unlikely to be achieved, with an estimated 600 million people still without access to electricity by 2030. One potential route to support this goal is through the use of mini-grids to provide electricity in densely populated rural areas for which grid connection is not possible. This paper presents the results of a life cycle assessment of a mini-grid, designed for construction in Malawi. It analyses the cradle to end of use for this mini-grid configuration, for a grid sized for lighting, refrigeration and phone charging, and for a grid sized for electric cooking (e-cooking). The results suggest that for lighting configuration, the main contributors to environmental impact are the poles, the overhead cabling, and the PV panels. The use of a chromium-based preservative is the main issue for the poles, and a switch to concrete poles can deliver significant benefits. When the grid is sized for e-cooking, the PV panels become the greatest contributor. Adding a diesel generator to the mini-grid configuration can reduce number of panels required and hence the environmental impact, but only if the generator is used for no more than 2 h per day.

Design of Grid-connected and Stand-alone Photovoltaic Systems for Residential Energy Usage: A Technical Analysis

Towards realizing the United Nations sustainable development goals, access to clean, cheap and reliable energy, especially electricity, has been considered as one of the vital indices in any community. Hence, this paper presents the design analysis of both a grid-connected and an offgrid photovoltaic (PV) systems for household users in the highly residential city of Ogbomoso in Nigeria using PVGIS software. For the off-grid design, it is estimated that, given a total daily load of 9.57 kWh, a 3.5 kWp PV array size and a battery capacity of 86 kWh are enough to power the load with 5 days of autonomy and 70% depth of battery discharge. For the grid-connected PV system, the annual energy output for a building-integrated PV system is found to be around 4006 kWh; and a total of eight PV modules (each rated 250 Wp, 30.93 V) are stringed to arrive at the desired capacity of 2 kWp. In terms of performance, the performance ratio (PR) of a building integrated grid-tied PV system at the study location was found to be 71.2% while for a free-standing PV system, the PR was 75%.