Thermodynamic Limits of the Use of PCM Simultaneously in Photovoltaic Modules and in Building

Permiso obtenido por la institución para subir el documentoThe paper quantifies the thermodynamic limits on the energy and exergy use that would result from the use of PCM in photovoltaic BIPV modules versus not using PCM, by limiting module temperature to 298 K and the thermal energy use in buildings according to a set of hypotheses. The results obtained have been extended to six different climates. The results show that the maximum use of PCM depends heavily on the climate, therefore in hot climates as Seville, Cairo and Nairobi, the improvements in energy efficiency are very important (multiplied from 6 to 9 times), while in cold climates as London and Helsinki, the improvements are not that significant (multiplied from 1.5 to 2 times). The exergetic efficiency improvements range of about 5% for all climates, due to the low operating temperature of the PCM. These materials requirements are significant, ranging between 31 and 193 kg/m2, with thicknesses between 3.9 and 24.2 cm/m2

High Vapor Transport Deposition: A Novel Process to Develop Cu2ZnSn(SxSe1–x)4 Thin Film Solar Cells

Kesterite thin film solar cells are known to be a promising cost-effective solution because they are based on earth-abundant and environmental compounds. However, it is known that their best efficiency (12.6%) has not been improved since 2013, meanwhile other thin-film solar cells have demonstrated that their performance has been enhanced continuously. The main drawbacks to explain this situation is the narrow process window of this compound and simultaneously, the high composition and thermal control needed to avoid intrinsic defects in the p-type layer. The high vapor transport deposition process has not been explored yet by kesterite thin film solar cell developers. Herein, we present the results obtained using a design of a new vacuum deposition method similar to close space sublimation, which reported excellent results in CdTe. The main advantages of this novel process are: 1) to achieve a high deposition rate; 2) to be able to deposit precursor materials and to carry out the sulfur-selenization in the same process chamber, avoiding the two steps used in the sequential process; 3) to provide a high accuracy in the chemical composition control; and 4) simple design using commercial components to facilitate its scalability for large production

Influence of Degradation Processes in Lead–Acid Batteries on the Technoeconomic Analysis of Photovoltaic Systems

Most technoeconomic feasibility studies of photovoltaic (PV) systems with batteries are mainly focused on the load demand, PV system profiles, total system costs, electricity price, and the remuneration rate. Nevertheless, most do not emphasise the influence degradation process such as corrosion, sulphation, stratification, active material seeding, and gassing on battery lifetime, efficiency, and capacity. In this paper, it is analysed the influence of the degradation processes in lead–acid batteries on the technoeconomic analysis of PV systems with and without battery. Results show that Net Present Value (NPV), Payback Period (PBP), and Discounted PayBack Period (DPBP) have a heavy dependence on the assumptions about the value of the battery performance parameters according to its degradation processes. Results show NPV differences in the range from −307% to 740%, PBP differences in the range from 9% to 188%, and DPBP differences in the range from 0% to 211%

Comparative analysis of domestic water heating thermosiphon systems tested according to the Standard ISO 9459-2

Permiso concedido para subir el documentoThe Standard ISO 9459-2 is a standard for the characterization of thermal performance of domestic water heating systems without auxiliary heating. In this study, 18 domestic water heating thermosiphon systems have been tested according to this international standard. The objective of the paper is to carry out a comparative analysis of the results obtained in these systems as a function of their volume and type of heat exchanger (tubular and double jacket). A comparative analysis of systems performance will be carried out by calculating the performance without thermal loss (a1/A) and solar fraction fSOL in different reference locations for different volume/area ratios. Also, a comparative analysis of systems performance and solar fraction will be carried out at different locations between a tubular heat exchanger tank and a double jacket heat exchanger tank. The different values obtained will be compared for the storage tank’s heat loss coefficient (Us). It will determinate the useful energy (energy with temperature above 45ºC) for the degree of mixing in the storage tank during a draw-off test

Thermodynamic Limits of the Use of Solar Energy for Cold Production

Permiso obtenido de la institución para subir este documetnoThe paper quantifies the thermodynamic limits on the energy and exergy use that would result from the use of PCM in photovoltaic BIPV modules versus not using PCM, by limiting module temperature to 298 K and the thermal energy use in buildings according to a set of hypotheses. The results obtained have been extended to six different climates. The results show that the maximum use of PCM depends heavily on the climate, therefore in hot climates as Seville, Cairo and Nairobi, the improvements in energy efficiency are very important (multiplied from 6 to 9 times), while in cold climates as London and Helsinki, the improvements are not that significant (multiplied from 1.5 to 2 times). The exergetic efficiency improvements range of about 5% for all climates, due to the low operating temperature of the PCM. These materials requirements are significant, ranging between 31 and 193 kg/m2, with thicknesses between 3.9 and 24.2 cm/m

Angular Dependence of Photonic Crystal Coupled to Photovoltaic Solar Cell

Photonic crystals have the advantage of minimizing thermal losses from solar cells, reflecting the solar radiation that is not absorbed by the photovoltaic device. To optimize this optical response, photonic crystals are designed considering the relative position of the Bragg peak and the bandgap of the solar cell, under normal incident irradiation conditions. The aim of this research article was to determine experimentally the optical limits of a solar cell coupled to a photonic crystal acting as beam splitter. For that purpose, the photovoltaic system was characterized under indoor and outdoor conditions; angular dependence of the irradiation source was determined in each case, and both results were compared with good agreement. Moreover, other parameters such as irradiation spectrum and polarization of the light were investigated. The main conclusion is that photovoltaic performance is highly affected by the Bragg peak shifting and the profile is distorted, due to the angular dependence with the sun. These experimental limits must be considered at the early design stage to avoid performance losses

Experimental Comparison of Different Global Irradiation Models with and without Sun Tracking for the South of Spai

Permiso obtenido por la institución para subir este documentoIt is very unusual to have global irradiance data for a tilted surface and even more for a surface with a perfect sun tracking. The most common available data is the global horizontal irradiance, thus it is necessary to convert the available data into the desirable inclination. The purpose of this paper is to analyse the different response of the radiation models that are used to calculate the global irradiance in static surfaces and in surfaces with a perfect sun tracking (two axis). For that end 10 years of measured data has been utilized. The combination of methods that better approaches to the experimental values is the one formed by Orgill - Hollands and Perez for stationary surfaces and mode- Temps-Coulson for two-axis tracking

Variaciones en el comportamiento de equipos solares prefabricados en función de la zona climática, de acuerdo a la norma ISO 9459-2

Este trabajo se apoya en los ensayos realizados por un estudiante de máster de la universidad de Sevilla. Estos ensayos proveen de valiosos datos de características de equipos solares. El objeto de este trabajo es determinar la relación de la energía absorbida por un sistema de captación solar en diferentes climas con 4 parámetros participantes en el cálculo, variando estos de una manera que se aprecie su influencia y así poder determinar el ajuste óptimo de estos para cada zona climática. Todo ello enmarcado en las condiciones de ensayo y cálculo descritas en la norma UNE-ISO 9459-2. El método descrito en la norma se implementa en una herramienta informática que permita un cálculo iterativo y condicionado. El software elegido es Microsoft Excel. Una hoja de cálculo permite el cálculo de la energía absorbida por el sistema a lo largo de un año, así como una presentación fácil, rápida e intuitiva de los resultados y de los datos tanto climáticos como de los equipos utilizados. Los datos climáticos utilizados son: - Temperatura del agua de red. - Irradiación. - Horas de luz. - Temperatura ambiente diurna y nocturna. Mientras que los datos de los equipos utilizados son: - Características técnicas (área de apertura, volumen de acumulación,…) - Coeficiente de pérdidas térmicas del acumulador (Us). - Gráfica Q-H (parámetros a1, a2 y a3). - Perfiles de extracción f(V) y g(V). El método de cálculo se ha aplicado a cuatro ciudades distintas, cada una representa unas condiciones climáticas de Tª y radiación opuestas. Estas ciudades son Atenas, Davos, Estocolmo y Wurzburg. Entre los resultados del análisis de sensibilidad llevado a cabo se pueden destacar: - Mayor importancia de la Gráfica Q-H frente a los demás, especialmente de a1. - Decreciente importancia de Us frente a un consumo creciente. - Ínfima influencia de la optimización de los perfiles de extracción f(V) y g(V). Por último se han intentado reflejar las relaciones entre los parámetros experimentales y las características técnicas de los equipos con los datos disponibles para poder sugerir el mejor ajuste posible de los equipos solares para las dadas condiciones climatológicas

Impact of Energy Losses Due to Failures on Photovoltaic Plant Energy Balance

Photovoltaic (PV) plant failures have a significant influence on PV plant security, reliability, and energy balance. Energy losses produced by a PV plant are due to two large causes: failures and inefficiencies. Knowing the relative influence of energy losses due to failures and energy losses due to inefficiencies on the PV plant energy balance contribute to the optimization of its design, commissioning, and maintenance tasks. This paper estimates the failure rates, grouped by components, and the relative impact of the failures on the PV plant energy balance through real operation and maintenance follow-up data of 15 PV plants in Spain and Italy for 15 months. Results show that the influence of failures in energy losses of all analysed PV plants is low, reaching a maximum value of 0.96% of the net energy yield. Solar field energy losses only represent 4.26% of all failure energy losses. On the other hand, energy losses due to inefficiencies have represented between 22.34% and 27.58% of the net energy yield

Experimental evaluation of the solar radiation gains over photovoltaic cells due to the use of tio2 treated surfaces. Applications to photovoltaic systems with micro-inverters

Permiso para subir el documento obtenido por la institución.In building integrated photovoltaic (PV) systems, the reflection of the solar radiation by the walls of the buildings may cause a non-uniform distribution of the incident radiation on the different PV modules. However, by using micro-inverters at strings levels, electricity production may increase instead of provoking losses by mismatching. For this purpose, the maximum possible solar gain due to reflections is required. The annual profit of the solar radiation depends on factors such as climate, latitude and the relative position of the cell to the reflective surface. In the location of Seville (Spain), the gain on a PV cell generation due to radiation reflected by a TiO2 treated perpendicular surface reaches a 13% for an entire year. Therefore, it is well demonstrated that using micro-inverters not only involves a loss reduction of a solar installation but also to obtain a profit from the solar radiation that cannot be achieved with centralized inverters