Initialization of a Multi-objective Evolutionary Algorithms Knowledge Acquisition System for Renewable Energy Power Plants

pp. 185-204The design of Renewable Energy Power Plants (REPPs) is crucial not only for the investments' performance and attractiveness measures, but also for the maximization of resource (source) usage (e.g. sun, water, and wind) and the minimization of raw materials (e.g. aluminum: Al, cadmium: Cd, iron: Fe, silicon: Si, and tellurium: Te) consumption. Hence, several appropriate and satisfactory Multi-objective Problems (MOPs) are mandatory during the REPPs' design phases. MOPs related tasks can only be managed by very well organized knowledge acquisition on all REPPs' design equations and models. The proposed MOPs need to be solved with one or more multiobjective algorithm, such as Multi-objective Evolutionary Algorithms (MOEAs). In this respect, the first aim of this research study is to start gathering knowledge on the REPPs' MOPs. The second aim of this study is to gather detailed information about all MOEAs and available free software tools for their development. The main contribution of this research is the initialization of a proposed multi-objective evolutionary algorithm knowledge acquisition system for renewable energy power plants (MOEAs-KAS-FREPPs) (research and development loopwise process: develop, train, validate, improve, test, improve, operate, and improve). As a simple representative example of this knowledge acquisition system research with two selective and elective proposed standard objectives (as test objectives) and eight selective and elective proposed standard constraints (as test constraints) are generated and applied as a standardized MOP for a virtual small hydropower plant design and investment. The maximization of energy generation (MWh) and the minimization of initial investment cost (million €) are achieved by the Multi-objective Genetic Algorithm (MOGA), the Niched Sharing Genetic Algorithm/Non-dominated Sorting Genetic Algorithm (NSGA-I), and the NSGA-II algorithms in the Scilab 6.0.0 as only three standardized MOEAs amongst all proposed standardized MOEAs on two desktop computer configurations (Windows 10 Home 1709 64 bits, Intel i5-7200 CPU @ 2.7 GHz, 8.00 GB RAM with internet connection and Windows 10 Pro, Intel(R) Core(TM) i5 CPU 650 @ 3.20 GHz, 6,00 GB RAM with internet connection). The algorithm run-times (computation time) of the current applications vary between 20.64 and 59.98 seconds.S

Real energy payback time and carbon footprint of a GCPVS

Grid connected PV systems, or GCPVS, produce clean and renewable energy through the photovoltaic e ect in the operation stage of the power plant. However, this is the penultimate stage of the facilities before its dismantlement. Before starting generating electricity with zero CO2 emissions, a negative energy balance exists mainly because of the embodied energy costs of the PV components manufacturing, transport and late dismantlement. First, a review of existing studies about energy life cycle assessment (LCA) and Carbon Footprint of PV systems has been carried out in this paper. Then, a new method to evaluate the Real Energy Payback Time (REPBT), which includes power looses due to PV panels degradation is proposed and di erences with traditional Energy Payback Time are analysed. Finally, a typical PV grid connected plant (100 kW nominal power) located in Northern Spain is studied in these sustainability terms. This facility has been firstly completely modelled, including PV modules, inverters, structures and wiring. It has been also considerated the energy involved in the replacement of those components with shorter lifespan. The PV panels degradation has been analysed through the comparison of normalised flash test reports on a significant sample of the installed modules before and 5 years after installation. Results show that real PV degradation a ect significantly to the Energy Payback Time of the installation increasing slightly a 4:2% more the EPBT value for the case study. However, along a lifespan of 30 years, the GCPVS under analysis will return only 5:6 times the inverted energy on components manufacturing, transport and installation, rather than the expected 9:1 times with the classical estimation

Net Energy Balance and Smart Grids in Spain: Integration with PV Systems

En este documento se presentan las principales configuraciones y reglamentos técnicos en España sobre Net Energy Balance Systems y Smart Grids. Esta falta de instalaciones es bastante interesante para los futuros desarrollos de fuentes de energía verde, especialmente fotovoltaicas. Los principales beneficios son la reducción de las pérdidas de energía en el sistema de distribución, la optimización de los recursos energéticos y un mejor seguimiento de la oferta de energía y la demanda de energía. Las redes inteligentes y los sistemas de equilibrio energético neto son las últimas tendencias en generación y distribución de energía eléctrica. Sus beneficios están ampliamente demostrados y contribuyen a reducir las emisiones de CO2 a la atmósfera y aumentar las tasas de eficiencia. La falta de apoyo público a la generación de energía fotovoltaica hace obligatorio buscar nuevos puntos de vista. Sin piensos en las políticas arancelarias, las enormes plantas fotovoltaicas no son atractivas hoy en día. Debemos centrarnos en los sistemas pequeños implementados en Smart Grids y apoyados con estrategias de Net Energy Balance. Esta es otra manera de apoyar la generación de energía verde y tiene grandes beneficios para los usuarios domésticos

Performance Indicators for Sun-Tracking Systems: A Case Study in Spain

pp. 292-302Current PV cells technology takes advantage mainly from beam radiation. In this context the sun-trackers are such devices for efficiency improvement. On the other hand, projected shadows between devices make mandatory to increase the distances between mounting systems. Thus, the land’s capacity for mounting PV panels can be dramatically decreased. This fact conducts us to wonder where the optimum efficient point is. First, in this paper different types of sun-tracking systems are classified according to the movement they perform (cinematic classification). Further, three real PV installations-fixed, horizontal-axis tracking and dual-axis mount tracking—located in the same geographical area in Spain (they are approximately under the same weather conditions) are analyzed. These installations have been studied in order to establish which one is the most efficient and affordable—Specific Energy Production (SEP) and Performance Ratio (PR) analysis. PVGIS solar radiation estimate tool has been used for comparing the theoretical radiation potential on each plant. The land requirements have been considered in the analysis of the Ground Cover Ratio (GCR) and the Surface Performance Ratio (SPR). Moreover, comparing three main financial indicators let us carry out a financial study: Payback Time (PBT), Net Present Value (NPV) and Internal Rate of Return (IRR). In the case study, final annual energetic results demonstrate that the dual-axis plant shows a relevant SEP advantage, but if we take into account the land occupied for this sort of devices we find much more profitable the horizontal-axis sun-tracking system, with a SPR value 4.24% higher than the fixed system we have studied. Its PBT is also a 22% lower than the dual-axis tracking installationS

Sun‐trackers profitability analysis in Spain

pp.1010-1022El objetivo principal de este estudio es analizar el rendimiento de los dispositivos de seguimiento solar en comparación con los sistemas de placaplana fija utilizando datos de un software de predicción de irradiación ampliamente utilizado (PVGIS). Analizamos los parámetros típicos comosuma diaria y mensual de irradiación global (HdandHm) o la producción media diaria y mensual estimada de electricidad (EhandEm) y también sus costos asociados y requisitos de tierra (generalmente descritos por la relación de cobertura del suelo,GCR ). Se observó que la influencia de estos dos últimos parámetros es bastante importante para el cálculo del tiempo de amortización de toda la instalación. Como resultado final, se concluye que aunque el rastreador de doble eje permite el máximo rendimiento energético, un 38% más alto que un sistema fijo en promedio, si tenemos en cuenta el valor GCR y calculamos la relación de rendimiento super-cara, la más eficiente configuración es el rastreador solar de eje horizontalS

New device for the simultaneous measurement of diffuse solar irradiance on several azimuth and tilting angles

A device is proposed for the measurement of diffuse solar irradiance on tilted surfaces pointing-to as well as fixed on the equatorial direction. Most commercial devices are not designed for this purpose. Here, we present a specific design for a system based on a single multi-lobe shadow-ring that allows us to measure diffuse irradiance with several tilted pyranometers – from 60 to 90 degrees from the horizontal plane – and on different azimuth angles. This first prototype allows us to measure in the four cardinal directions. The ring is designed to minimize the covered celestial dome observed by each sensor. Moreover, the complete device needs a very small installation area and its simplicity means it is inexpensive and easy to operate. The measurements have subsequently to be corrected with a geometrical correction factor that takes into account the portion of the sky vault blocked by the shadow-ring. These measurements are essential for estimating solar potential on tilted surfaces – such as building façades – and for improving current anisotropic solar models, among many other applications.Spanish Government (grant ENE2011-27511

Multi-dimensional barrier identification for wind farm repowering in Spain through an expert judgment approach

.Spain was one of the pioneers in the deployment of wind energy systems worldwide and thus since 2014 has a potential for repowering that reaches between 3.3 and 8.7 GW in 2021 (12%–32% of its current installed wind capacity). However, despite the technical and economic advantages, we have observed little interest from promoters in the repowering of already amortized wind farms. The aim of the proposed study is to depict the background framework of barriers for repowering wind farms, which is specially affecting to Spain, but that can also extend to other EU countries. Therefore, we conducted a systematic survey study with academics, promoters, financial experts, manufacturers, operators, maintainers and policymakers to identify and understand the existing real and practical barriers. As a result, we have identified 34 major barriers covering five categories: technical issues, economics, environmental considerations, social concerns, and regulatory and administrative hurdles. We then asked the experts to rate these barriers based on their impact or relevance. We found that the experts agree that regulatory and administrative barriers have the maximum impact, while economic, environmental and technical barriers have only a mid-high impact. Therefore, we can conclude that, in general, the Administration must develop a concise and stable regulatory framework for all RES, especially for repowering projects, and carry out a review of both the technical requirements and the incentives schemes, with a focus on energy efficiency.S

Hydrogen as an energy vector to optimize the energy exploitation of a self-consumption solar photovoltaic facility in a dwelling house

Solar photovoltaic (PV) plants coupled with storage for domestic self-consumption purposes seem to be a promising technology in the next years, as PV costs have decreased significantly, and national regulations in many countries promote their installation in order to relax the energy requirements of power distribution grids. However, electrochemical storage systems are still unaffordable for many domestic users and, thus, the advantages of self-consumption PV systems are reduced. Thus, in this work the adoption of hydrogen systems as energy vectors between a PV plant and the energy user is proposed. As a preliminary study, in this work the design of a PV and hydrogen-production self-consumption plant for a single dwelling is described. Then, a technical and economic feasibility study conducted by modeling the facility within the Homer Energy Pro energy systems analysis tool is reported. The proposed system will be able to provide back not only electrical energy but also thermal energy through a fuel cell or refined water, covering the fundamental needs of the householders (electricity, heat or cooling and water). Results show that, although the proposed system effectively increases the energy local use of the PV production and reduces significantly the energy injections or demands into/from the power grid, avoiding power grid congestions and increasing the nano-grid resilience, operation and maintenance costs may reduce its economic attractiveness for a single dwelling. Keywords: Hydrogen, Solar photovoltaics, Energy vector, Power storage, Smart grids, Nano-grid

Shadow-band radiometer measurement of diffuse solar irradiance: Calculation of geometrical and total correction factors

Among the various methods of measuring diffuse solar irradiance, shadowing devices are ones of the most commonly used in solar research all over the world. These instruments work with a basic pyranometer, properly calibrated for the measurement of solar irradiance, with a shadowing element, which can be a disk or a band (Drummond’s shadow-band), that prevents the direct incidence of solar beam irradiance on the sensor. This method is capable of precise measurements, but sensor outputs have to be corrected, so as to quantify the amount of diffuse irradiance that the band blocks from reaching the sensor. Several authors have advanced different expressions for this correction factor, most of which only apply to horizontal and equator-oriented tilting pyranometers. In this work, we present a general approach to calculate the geometrical correction factor for a tilted sensor, oriented towards all possible azimuth and zenith angles, which permits the measurement of solar diffuse irradiance on any tilted and oriented surfaces. Furthermore, five total correction models are adapted for measurement in any given direction and evaluated on vertical walls pointing the four cardinal directions. Our results show that geometrical correction improves the Mean Bias Difference (MBD), the Root Mean Squared Difference (RMSD) and the l0:99 statistics by 60%, 62% and 56%, respectively, in contrast with the raw data. The LeBaron et al. model gives the most accurate figure for total correction according to MBD, RMSD and l0:99 statistics, with promising average performances of 97%, 91%, and 96%, respectivelySpanish Government (grant ENE2011-27511

Ambulatory surgery in orthopedics: experience of over 10,000 patients

PurposeThe concept of day surgery is becoming an increasingly important part of elective surgery worldwide. Relentless pressure to cut costs may constrain clinical judgment regarding the most appropriate location for a patient’s surgical care. The aim of this study was to determine clinical and quality indicators relating to our experience in orthopedic day durgery, mainly in relation to unplanned overnight admission and readmission rates. Additionally, we focused on describing the main characteristics of the patients that experienced complications, and compared the patient satisfaction rates following ambulatory and non-ambulatory procedures.MethodsWe evaluated 10,032 patients who underwent surgical orthopedic procedures according to the protocols of our Ambulatory Surgery Unit. All complications that occurred were noted. A quality-of-life assessment (SF-36 test) was carried out both pre- and postoperatively. Ambulatory substitution rates and quality indicators for orthopedic procedures were also determined.ResultsThe major complication rate was minimal, with no mortal cases, and there was a high rate of ambulatory substitution for the procedures studied. Outcomes of the SF-36 questionnaire showed significant improvement postoperatively. An unplanned overnight admission rate of 0.14 % was achieved.ConclusionsOur institution has shown that it is possible to provide good-quality ambulatory orthopedic surgery. There still appears to be the potential to increase the proportion of these procedures. Surgeons and anesthesiologists must strongly adhere to strict patient selection criteria for ambulatory orthopedic surgery in order to reduce complications in the immediate postoperative term