Open Access
Gain of bifacial PV modules on horizontal single-axis trackers in desert climates
(IEEE, 2024-11-15) Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA2023-11389
Over the last few years, the demand for bifacial PV modules has continuously increased. However, there are still some aspects regarding their outdoor performance under real conditions that need further investigation. This paper analyzes the bifacial PV modules gain obtained over one year in a horizontally tracked PV power plant located in the Atacama Desert, Chile. The study was carried out over the course of a year for two different types of trackers: a standard tracker as used in the rest of the plant and a tracker that, according to the manufacturer, is specially designed to maximize the production of the bifacial modules. The results show that bifacial PV modules with a conventional tracker are able to gain approximately a 5% in terms of both radiation and production whereas the bifacial PV modules mounted on the special bifacial tracker can gain up to 5.8% and 6.1 % respectively.
Open Access
Analysis of polyamide and fluoropolymer backsheets: Degradation and insulation failure in field-aged photovoltaic modules
(John Wiley & Sons, 2022) Pascual Miqueleiz, Julio María; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Durability of photovoltaic (PV) modules is of great concern not only from the point of view of cost-effectiveness but also from the point of view of safety and sustainability. The backsheet of a PV module is one of the most critical parts of the PV module from the point of view of protection and also one of the most important sources of PV modules' failure; hence, it is of great importance to understand its different forms of failure. In this paper we analyze the case of an 8-MW PV plant, which had suffered a rapid degradation of their PV modules' backsheets. The case is especially relevant as all the PV modules are from the same model and manufacturer but with different backsheet materials (polyamide and fluoropolymer) and different times of exposure: on one hand, all PV modules originally installed in the plant (i.e., 6 years under operation when tested), and also, extra modules that had been stored indoors for replacement and had been mounted in the plant for less than 1 year when tested, serving as reference modules. In this paper we present the signs of degradation of these PV modules after different times of exposure under real operation using different on-field and laboratory tests. We propose different techniques for rapid diagnosis of backsheet degradation so that the problem can be detected at a very early stage, before it results in major energy losses or in safety issues.
Open Access
Design and implementation of a PV installation to measure the optimal orientation of an horizontal single axis tracker under any radiation conditions
(IEEE, 2024-08-30) Arrubla Irigoyen, Mikel; García Solano, Miguel; Marroyo Palomo, Luis; García Gimeno, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Traditional PV tracking systems aim to orient the surface of the modules as perpendicular as possible to the sun. However, in cloudy sky conditions, this tracking strategy does not maximize radiation capture. Some authors have attempted to quantify by simulation the radiation gain that would be obtained at various locations if the position of the modules were always optimal. However, there is no study in the state of the art that has experimentally measured this optimal position or the associated energy gain. This paper presents both a facility and a test specially designed to experimentally measure the optimal tilt angle of a Horizontal Single Axis Tracker (HSAT) oriented in the north-south direction, for any sky condition, and for both monofacial and bifacial PV modules. This facility will allow the experimental validation of theoretical optimal angle tracking models and calculations derived from them.
Open Access
Long-term degradation rate of crystalline silicon PV modules at commercial PV plants: an 82-MWp assessment over 10 years
(Wiley, 2021) Pascual Miqueleiz, Julio María; Martínez Moreno, Francisco; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Lorenzo Pigueiras, Eduardo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Due to high competitiveness in the PV sector, despite the low degradation rate of crystalline silicon PV modules (below 0.5%/year), it is still important for utilities to know its actual value due to its impact on energy yield and hence, profitability, over the lifetime of a PV plant. However, uncertainties related to both the influence of downtime periods due to problems that may appear under normal operation of a commercial PV plant and to the measurement of degradation rates at PV plant level make this a challenging task. In order to obtain a significant value, in this paper, three measuring methods with different uncertainty sources are used for 82 MWp of PV modules on different locations in Spain and Portugal over 10 years. According to the different methods used and PV plants analyzed, excluding PV plants with problems, a range of degradation rates between 0.01 and 0.47%/year has been found. The overall average value observed is 0.27%/year. The findings of this work have also revealed the great importance of good operation and maintenance practices in order to keep overall low degradation rates.
Open Access
Outdoor performance of a CdTe based PV generator during 5 years of operation
(IEEE, 2022) Guerra Menjívar, Moisés Roberto; Parra Laita, Íñigo de la; Marcos Álvarez, Javier; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Together with the huge growth of the traditional crystalline silicon (Si-x) PV manufacturers, other thin-film solar cells have also emerged such as cadmium telluride (CdTe) manufacturers. They are characterized by the fact that they were created to reduce costs and by the scarcity of silicon, from which the rest of the modules are made. Despite they need more space to generate the same amount of energy as crystalline modules, their price is supposed to be much lower, and argue that they have a better performance at high temperatures. However, real comparisons between the outdoor performance of CdTe and Si-x modules have been scarcely addressed in the literature. This paper provides a comparison under real operating conditions of a CdTe photovoltaic generator versus a conventional silicon generator during 5 years of operation in a mid-latitude area, identifying the causes of the differences observed.
Open Access
In-field energy performance of solar PV module made of UMG silicon
(IEEE, 2022) Guerra Menjívar, Moisés Roberto; Parra Laita, Íñigo de la; García Solano, Miguel; Pascual Miqueleiz, Julio María; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC
Upgraded metallurgical grade silicon (UMG-Si) PV modules have failed to make their space in the PV market, which was partly to the uncertainty on their in-field performance that brings the wide disparity of results published over the years. The most-recently developed UMG-Si PV modules have demonstrated similar initial degradation and efficiencies under standard test conditions (STC) to those obtained with conventional solar grade silicon (SoG-Si). Nevertheless, their performance under operating conditions other than STC and its impact on the energy production are key aspects that have not yet been properly characterized in the literature. This article analyzes the in-field performance of a PV generator comprised of recently developed UMG-Si modules. This performance was compared to that of another PV generator comprising standard polysilicon modules. The cells and modules of both types of generators were made by the same manufacturer in the same period and on the same production lines, which guarantees that performance differences encountered are exclusively due to the silicon employed. Contrary to the previous experience, this article reveals that UMG-Si modules do not necessarily present a better temperature performance than today's conventional modules. The analyzed UMG-Si modules presented 1.6% less efficiency under low irradiance conditions, but this different irradiance performance led to an insignificant difference (less than 0.5%) in their energy production. No significant degradation was measured in both UMG-Si and SoG-Si modules during the two-year analyzed period, being the final energy performance of both types of modules essentially the same. These results can be considered as highly representative of the current state-of-the-art of UMG-Si technology.
Open Access
Analysis of a CIS based PV generator versus a multicrystalline generator under outdoor long-term exposure
(IEEE, 2021) Parra Laita, Íñigo de la; Guerra Menjívar, Moisés Roberto; Marcos Álvarez, Javier; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
The worldwide growth of the PV market has been almost exponential during the last years. Together with conventional crystalline (c-Si) PV modules, “new” commercially available PV technologies such as copper indium selenide (CIS) based solar cells have appeared achieving a similar efficiency comparable to c-Si at similar production cost. In addition to the use of cheaper materials, CIS solar cells manufacturers claim some enhancements such as lower temperature coefficient or higher absorption of diffuse light that achieve to reduce the cost of electrical energy. Although several papers deal with this topic, little is known about real comparisons between CIS technology and conventional crystalline at a PV generator level with real test conditions. This paper analyses the in-field performance and degradation of a commercially available CIS solar based PV generator compared to a conventional c-Si one during four years of operation attributing the differences observed to the possible factors that can influence in both technologies.