Open Access
On the calculation of the STC power of PV generators by using typical monitoring system data
(2017) Muñoz Escribano, Mikel; Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The properly in-field characterization of the power at Standard Test Conditions, PSTC, of PV generators is becoming increasingly important in order to evaluate their performance and its evolution in time. Within the state of art, the PSTC characterization procedures of PV arrays are mainly based on I-V curve measurements or PDC measurements performed by precision wattmeters. Those characterizations are usually carried out during discrete measurement campaigns, which does not allow a continuous tracking of the PSTC evolution. In this paper a new PSTC characterization procedure is proposed which is based on the DC power measurements performed by the own PV inverters connected to the PV arrays. This procedure enables an automatic and continuous calculation of the PSTC, which allows to observe its evolution and to detect possible anomalous trends, premature degradations, etc. The procedure has been validated in several PV generators of the large-scale Amareleja PV Plant (45.6 MWp). As showed in this paper, by using several day data and applying the adequate filters, a high accuracy in the PSTC calculation can be achieved, a similar accuracy to that obtained by using precision wattmeter measurements.
Open Access
Compensation of forecast error in large PV plants with battery storage: associated strategies
(2017) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; Muñoz Escribano, Mikel; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
As penetration rates of utility-scale photovoltaics (PV) increases, large PV plants will participate in the daily wholesale electricity market in the same way that wind farms. Then, PV plant owner can receive some kind of economic penalty depending on the forecast deviation. This opens the way to use a battery energy storage system (BESS) to compensate the prediction errors. Taking advance of the several 1-hour intra-diary market sessions, the PV plant owner can correct the prediction for the next hours. Hence, a 1-hour BESS SOC control can be implemented to avoid large energy requirements. Here we present two novel strategies which allow a large PV-BESS plant to fulfil the programme referred.
Open Access
A comparative study of degradation and performance of thin film photovoltaic generators versus a multi-crystalline generator
(2013) Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
Thin film solar cells (TFSC) are supposed to have higher energy yield rates than crystalline silicon (Si-x) mainly possible by some enhancements like lower temperature coefficient and higher absorption of diffuse light. Although several papers deal with this topic, there are uncertainties and there is no conclusive outcome to their performance compared to Si-x. The aim of this paper is to contribute to the state of the art on this topic providing experimental data of degradation and performance of several commercially available TFSC generators (CdTe, CIGS, a-Si, a Si/µSi) and a conventional Si x. The energy yield of the TFSC generators during two years is compared to the Si-x one which is supposed to be the standard.
Open Access
Ramp-rate control in large PV plants: battery vs. short-term forecast
(IEEE, 2018) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; Cirés Buey, Eulalia; Wang, Guang Chao; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
The changeability in the power produced by utility-scale PV plants caused by shadows due to passing clouds can compromise grid stability. Traditionally, some kind of energy storage systems (ESS) is proposed as the solution to reduce power variations below the limits imposed by new grid codes regulations. However, recent short-term forecast sources open the door to control the variability without batteries, using only inverter limitation. This option entails some energy curtailment losses that has not been yet addressed. This paper quantifies these losses for the first time using a meaningful database of 5 s one year data for a 38.5 MW PV plant in a perfect forecast scenery. Finally, we compare the economic cost of installing a lithium-ion battery vs. the inverter limitation solution. The results obtained indicate that battery-less strategies must not be neglected for ramp-rate control, since they can be more cost-effective using perfect forecast for any ramp value.
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
On the on-site measurement of the degradation rate of crystalline silicon PV modules at plant level
(IEEE, 2018) Pascual Miqueleiz, Julio María; Berrueta Irigoyen, Alberto; 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
This paper proposes a method for measuring the degradation rate of crystalline silicon PV modules at plant level in two different ways as a form of verification. As actual levels of degradation rate have been observed to be as low as 0.2%/a, the uncertainties make it difficult to measure this value accurately at plant level. However, despite the low value, it is still important to know the actual degradation rate due to its impact on energy yield. In this paper, two ways of measuring the degradation rate at plant level are proposed. These two methods, with different uncertainty sources, are proposed to be used jointly in order to have a better approach to the real value. Finally, an example of measurement in a 1.78 MW PV plant is presented.
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
The potential of forecasting in reducing the LCOE in PV plants under ramp-rate restrictions
(Elsevier, 2019) Cirés Buey, Eulalia; Marcos Álvarez, Javier; Parra Laita, Íñigo de la; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
An increasing number of grid codes are requiring the limitation of the PV output power fluctuation over a given time scale. Batteries represent the most obvious solution to smooth power fluctuations, with the corresponding negative impact on the PV energy cost. However, short-term forecasting is currently being proposed as a tool to reduce battery capacity requirements or even completely remove it. Although these solutions decrease or avoid the battery cost, it also entails some energy curtailment losses which obviously raise the final cost of PV energy. This energy losses, currently unknown, are independent of the forecasting accuracy and represent the minimal additional cost in the hypothetical case of a perfect prediction. Thus, this paper compares Levelized Cost of Energy (LCOE) of three ramp-rate control strategies in order to determine which would give the lowest cost: battery-based, ideal short-term forecasting, or a combination of both. Results show that curtailment losses would be small enough to make battery-less strategy an appropriate choice, so it is worthwhile improving short-term forecasting in view of the potential LCOE savings. Database is taken from high resolution measurements recorded for over a year at 8 PV plants ranging from 1 to 46 MWp.
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.