Eduardo Lorenzo Pigueiras

Universidad Politécnica de Madrid | UPM · Instituto de Energía Solar (IES)

STC power control of PV module supply requires testing large samples of modules with low uncertainty. This paper analyses the feasibility of outdoor measurements with the modules kept at their operating positions. The classical procedure of recording I‐V curves and translating them to STC in accordance with IEC‐60891:2021 using the cell temperature...

The deployment of bifacial photovoltaic (PV) modules for utility‐scale PV plants has quickly proliferated in recent years. As they can harness the irradiance received at the rear side of bifacial generators—which depends on the albedo of the reflector ground—bifacial modules provide higher productivity than monofacial modules, in exchange for a low...

STC power control of PV modules supply requires testing large samples of modules with low uncertainty. This paper analyses the feasibility of outdoor measurements with the modules kept at their operating positions. The classical procedure of recording I-V curves and translating them to STC in accordance with IEC 60891 using the cell temperature dir...

A pioneer experience with the production and first commercialization of bifacial PV modules was developed by ISOFOTON, a Spanish academic spin-off established in 1981. Bifacial modules based on n-PERT cell technology were produced until 1989. 59 modules from that time were recovered from real installations after about 20 years of outdoor exposure....

In order to mitigate PV power fluctuations, ramp rate control is performed coupling battery energy storage systems to PV plants. In previous works, we developed a method to minimise the power and energy capacity of a battery by considering the probability of occurrence of fluctuations and a penalty imposed in the event of not complying with a certa...

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...

Mismatch losses (MML) in PV arrays have been experimentally investigated by observing the dispersion in the operating voltage of the individual modules under normal operating conditions, that is, with the inverter delivering energy to the grid, and by assuming that in the absence of mismatch, all the modules will have the same operating voltage whi...

This paper recounts an historical record of the origins of bifacial PV modelling in the years between 1983 and 1989. Associated to the first industrial production of bifacial PV modules, that took place in 1984, PV modelling was developed by completing the three stages of an engineering modelling path: model development, experimental validation and...

Open questions remain regarding the use of bifacial photovoltaic (PV) modules, such as how to link the energy-yield modelling of large bifacial PV plants with further on-site measurements campaigns, the effect of the non-uniformity of the rear irradiance, as well as the convenience of varying the geometry of the plants to enhance the bifacial contr...

Photovoltaic (PV) systems can be affected by complex shading. Software solutions have been developed over time, offering an ever-increasing set of simulation possibilities to evaluate the energy losses induced by shading on PV systems. Yet, several practical cases cannot be satisfactorily solved by means of existing tools. This study explores the p...

This article presents a specific procedure to control the standard test conditions (STC) power in photovoltaic (PV) modules. It also shows the results of its application on a supply of approximately 700 000 multicrystalline p‐type silicon BSF technology PV modules made by a worldwide known manufacturer (Tier‐1, Q4 2015). First, during the manufactu...

The current state of the art of photovoltaic (PV) irrigation systems is limited to PV peak powers below 40 kWp, which does not cover the irrigation needs of farmers, co-operatives, irrigator communities, and agro-industries. This limitation of power is due to two main technical barriers: The quick intermittence of PV power due to the passing of clo...

Considering that the current through all the PV modules of a same string is constant, any differences in the electrical behaviour of the modules give raise to differences in the corresponding operation voltages. That opens the door for careful observations of the PV array functioning carried out under normal operation conditions, that is, with the...

Quality control of PV modules in large grid-connected PV plants is typically accomplished by means of indoors testing at qualified laboratories which use solar-simulators. Nevertheless, outdoors on-site measurement of PV modules has several advantages: the devices required to measure the PV modules are much cheaper than solar simulators; the costs...

In-field photovoltaic (PV) module and array characterization is becoming increasingly important within the particular framework of quality assurance procedures at large commercial PV plants. In this context, the correct measurement of the module temperature is critical in order to reduce uncertainty and increase repeatability of results. In the cas...

This paper presents a new type of PV structure called delta, ΔS(60). This was developed in order to achieve a constant irradiance daily profile similar to that obtained with a North-South horizontal axis tracker (1xh) since this constancy is essential for a number of PV applications, namely for PV irrigation systems. A comparison between these two...

Potential induced degradation could considerably decrease the performance of photovoltaic systems which operate at high DC voltages. Nonetheless, methodologies for dealing with it in field are not clearly yet defined. This work explains the kinetics of this phenomenon in the field and presents an assessment of its occurrence, detection and predicti...

The quality assurance procedures associated with the financing of large PV plants are becoming increasingly more relevant to the PV scene in general. In this context, PV performance modelling is required in order to predict the energy yield and to rate the operating plant performance. Despite the availability of PV performance models since the earl...

This article presents an analysis on irradiance modelling and its impact on energy estimation uncertainty. In particular, the calculation of the effective in-plane irradiance from broadband horizontal irradiance is assessed. Thirty-one models for irradiance distribution, decomposition, transposition and spectral correction have been considered. The...

This paper presents the IES-UPM experience in the outdoor characterization of PV modules. On days with clear sky conditions, a rather simple device consisting of a thermally-insulated wooden box allows the STC characteristics and the thermal coefficients of PV modules to be measured with low expanded uncertainty (±1.87% in power (k = 2)). Particula...

This chapter will study the dynamics of irradiance and the power delivered to the grid by PV plants in time frames of less than 10 min, paying particular attention to the influence of PV plant size and geographic dispersion on magnitude and duration. We are now going to present some general models which make it possible to simulate the power fluctu...

PV power fluctuations caused by clouds are leading operators of grids with high renewable energy penetration rates to impose ramp rate limitations. Costly battery energy storage systems are used for fulfilling these regulations but the question of the power and energy requirements for accomplishing them has not been fully answered. This work analys...

The invention can be included in the technical field of the methods for calculating the power generated by electrical centres based on intermittent power sources, wherein said method accurately reproduces the dynamic in the power generated by a set of dispersed photovoltaic systems in all the relevant parameters for the operator of the electrical s...

Procedimiento de evaluación de pérdidas energéticas provocadas por sombras proyectadas sobre paneles solares fotovoltaicos. El procedimiento de la invención se basa en sacar partido del almacenamiento de la profundidad de campo (depth buffer) utilizado en las tarjetas gráficas (que permite evaluar qué polígonos quedan ocultos por otros al represent...

Método de detección automática y diagnóstico de fallos de operaciones en instalaciones solaresfotovoltaicas distribuidas. El método solo requiere la medida de los datos de producción de energía, de manera que el material necesario por parte del operador de la instalación fotovoltaica se basa en un equipo capaz de medir la energía producida por las...

The hot-spot phenomenon is a relatively frequent problem occurring in current photovoltaic generators. It entails both a risk for the photovoltaic module’s lifetime and a decrease in its operational efficiency. Nevertheless, there is still a lack of widely accepted procedures for dealing with them in practice. This paper presents the IES–UPM observ...

Método de generación de datos de irradiación solar a partir de datos de producción energética de instalaciones solares fotovoltaicas. El método solo requiere la medida de los datos de producción de energía, de manera que el material necesario por parte del operador de la instalación fotovoltaica se basa en un equipo capaz de medir la energía produc...

Phenomena of overirradiance have been pointed all over the World. This note presents the most extreme enhancement event reported in Brazil, which contains an irradiance reading of 1590 W/m2 measured in São Paulo (latitude 23°32′S) at relatively low altitude (760 m a.s.l.).

Shading reduces the power output of a photovoltaic (PV) system. The design engineering of PV systems requires modeling and evaluating shading losses. Some PV systems are affected by complex shading scenes whose resulting PV energy losses are very difficult to evaluate with current modeling tools. Several specialized PV design and simulation softwar...

The hot-spot phenomenon is a relatively frequent problem occurring in current photovoltaic generators. It entails both a risk for the photovoltaic module's lifetime and a decrease in its operational efficiency. Nevertheless, there is still a lack of widely accepted procedures for dealing with them in practice. This paper presents the IES-UPM observ...

This paper presents the impact of non-homogeneous deposits of dust on the performance of a PV array. The observations have been made in a 2-MW PV park in the southeast region of Spain. The results are that inhomogeneous dust leads to more significant consequences than the mere short-circuit current reduction resulting from transmittance losses. In...

When evaluating the performance of a photovoltaic (PV) system, it is extremely important to correctly measure the plant operating conditions: incident irradiation and cell temperature. At large-size PV plants, the possible dispersion of the plant operating conditions may affect the representativeness of the values measured at one single point. The...

Concentrating Photovoltaics (CPV) is an alternative to flat-plate module photovoltaic (PV) technology. The bankability of CPV projects is an important issue to pave the way toward a swift and sustained growth in this technology. The bankability of a PV plant is generally addressed through the modeling of its energy yield under a baseline loss scena...

To date, the majority of quality controls performed at PV plants are based on the measurement of a small sample of individual modules. Consequently, there is very little representative data on the real Standard Test Conditions (STC) power output values for PV generators. This paper presents the power output values for more than 1300 PV generators h...

Short-term variability in the power generated by large grid-connected photovoltaic (PV) plants can negatively affect power quality and the network reliability. New grid-codes require combining the PV generator with some form of energy storage technology in order to reduce short-term PV power fluctuation. This paper proposes an effective method in o...

Concentrating Photovoltaics (CPV) is an alternative to flat-plate module photovoltaic (PV) technology. The bankability of CPV projects is an important issue to pave the way toward a swift and sustained growth in this technology. The bankability of a PV plant is generally addressed through the modeling of its energy yield under a baseline loss scena...

This paper describes the design of an original twin capacitive load that is able of tracing simultaneously the I–V characteristics of two photovoltaic modules. Besides, an example of the application of this dual system to the outdoor rating of photovoltaic modules is presented, whose results have shown a good degree of repeatability. Copyright © 20...

This paper presents the measurement of the I-V curve of an 800 kW PV generator by means of an own-made capacitive load. Along the lines of some previous works, it is shown that an I-V curve analysis can also be applied to big PV generators and that, when measuring the operating conditions with reference modules and taking some precautions (especial...

This paper presents the measurement of the I–V curve of a 500-kW PV generator by means of an own-made capacitive load. It is shown that I–V curve analysis can also be applied to big PV generators and that when measuring the operation conditions with reference modules and taking some precautions (especially regarding the operation cell temperature),...

A number of findings have shown that the test procedures currently available to determine the reliability and durability of photovoltaic (PV) modules are insufficient to detect certain problems. To improve these procedures, ongoing research into the actual performance of the modules in the field is required. However, scientific literature contains...

The degradation observed on a 7-kWp Si-x photovoltaic array after 17 years of exposure on the roof of the Solar Energy Institute of the Polytechnic University of Madrid is presented. The mean peak power degradation has been 9% over this time, or an equivalent to 0.53% per year, whereas peak power standard deviation has remained constant. The main v...

This paper presents an assessment and evaluation of the costs of operation and maintenance (O&M) in a real PV rural electrification (PVRE) programme, with the aim of characterizing its costs structure. Based on the extracted data of the 5-years operational costs of a private operator, the programme has been analyzed to take out the most relevant co...

This paper analyzes the correlation between the fluctuations of the electrical power generated by the ensemble of 70. DC/AC inverters from a 45.6. MW PV plant. The use of real electrical power time series from a large collection of photovoltaic inverters of a same plant is an important contribution in the context of models built upon simplified ass...

The power generated by large photovoltaic (PV) plants is of an intermittent nature, due to cloud passage, which can create considerable fluctuations in output. Therefore, if the penetration of PV power in the overall electricity system is high enough, these fluctuations could have a serious effect on the quality and safety of the power supply. This...

The quality and the reliability of the power generated by large grid‐connected photovoltaic (PV) plants are negatively affected by the source characteristic variability. This paper deals with the smoothing of power fluctuations because of geographical dispersion of PV systems. The fluctuation frequency and the Maximum fluctuation registered at a PV...

This paper reports on the IES-UPM experience from 2006 to 2010 in the field of the characterization of PV arrays of commercial large PV plants installed in Spain within the framework of the profitable economic scenarios associated to feed-in tariff laws. This experience has extended to 200 MW and has provided valuable lessons to minimize uncertaint...

This paper presents a review of back-tracking geometry not only for single axis but also for two-axis tracking and analyses the corresponding energy gains. It compares the different back-tracking strategies with the ideal tracking in terms of energy yield concluding, on the one hand, that back-tracking is more useful for single horizontal axis than...

The power generated by large grid-connected photovoltaic (PV) plants depends greatly on the solar irradiance. This paper studies the effects of the solar irradiance variability analyzing experimental 1-s data collected throughout a year at six PV plants, totaling 18 MWp. Each PV plant was modeled as a first order filter function based on an analysi...

Field data of soiling energy losses on PV plants are scarce. Furthermore, since dirt type and accumulation vary with the location characteristics (climate, surroundings, etc.), the available data on optical losses are, necessarily, site dependent. This paper presents field measurements of dirt energy losses (dust) and irradiance incidence angle los...

The variable nature of the irradiance can produce significant fluctuations in the power generated by large grid-connected photovoltaic (PV) plants. Experimental 1 s data were collected throughout a year from six PV plants, 18 MWp in total. Then, the dependence of short (below 10 min) power fluctuation on PV plant size has been investigated. The ana...

This paper presents a simple mathematical model to estimate shading losses on PV arrays. The model is applied directly to power calculations, without the need to consider the whole current–voltage curve. This allows the model to be used with common yield estimation software. The model takes into account both the shaded fraction of the array area an...

This paper presents the key points to assure the sustainability of a PV water pumping program that has supplied 5 million m3 of water in the last 12 years to approximately 40 000 people. Key aspects for success have been the proper consideration of user's priorities, rigorous technical quality assurance, and maintenance structure set up. The presen...

The irradiance fluctuations and the subsequent variability of the power output of a PV system are analysed with some mathematical tools based on the wavelet transform. It can be shown that the irradiance and power time series are nonstationary process whose behaviour resembles that of a long memory process. Besides, the long memory spectral exponen...

Currently, the know-how and experience concerning the behavior and reliability of large tracking photovoltaic (PV) plants is scarce. Information such as the availability rate is rarely known. Acciona Solar PV plants installed in Navarra (Spain) in the frame of the Spanish utility grid constitute a representative source of information. The scope of...

A review of existing studies about life cycle assessment (LCA) of PV systems has been carried out. The data from this review have been completed with our own figures in order to calculate the energy payback time (EPBT) of double and horizontal axis tracking and fixed systems. The results of this metric span from 2 to 5 years for the latitude and gl...

Energy yield and occupation of land are two parameters that must be optimized when designing a large PV plant. This paper presents the results of simulating the energy yield of flat panels for some locations and different tracking strategies as a function of the ground cover ratio. Some interesting results for design purposes, such as the optimal s...

This paper details an investigation into the appearance of hot-spots in two large grid-connected photovoltaics (PV) plants, which were detected after the visual inspection of trackers whose energy output was decreasing at anomalous rate. Detected hot-spots appeared not only in the solar cells but also in resistive solder bonds (RSB) between cells a...

In the current photovoltaic market, the importance of module quality control process is growing although its implementation in large size plants is not evident and it can also produces delays in the setting up of the power plant. In this article, the authors describe a simple module testing process aimed to be applied in the field. It allows more t...

When analysing the influence of shade on photovoltaic (PV) systems, the intuitive assumption is that conversion architectures with more inverters, such as string- and module-inverters, will have lower energy losses associated with partial shading of the generators. However, other phenomena which can affect a system's response to shade, for example,...

En el mercado fotovoltaico actual, es cada vez mayor la importancia de procesos de control de calidad de módulos, si bien la realización de los mismos para centrales solares de gran tamaño conlleva problemas de implementación y puede acarrear retrasos. En este artículo se describe un procedimiento de medida de módulos fotovoltaicos destinado a ser...

Low concentration devices along with standard (one sun) modules represent an attractive option to reduce the cost per kilowatt-hour in photovoltaic installations. This paper deals with the energy gains obtained over a year by two of such devices: a 2 × V-trough concentrator and a 1·5 × single flat mirror structure. The experiment was mounted on a t...

Several authors have analysed the changes of the probability density function of the solar radiation with different time resolutions. Some others have approached to study the significance of these changes when produced energy calculations are attempted. We have undertaken different transformations to four Spanish databases in order to clarify the i...

In October 2002, under the auspices of Spanish Cooperation, a pilot electrification project put into operation two centralised PV-diesel hybrid systems in two different Moroccan villages. These systems currently provide a full-time energy service and supply electricity to more than a hundred of families, six community buildings, street lighting and...

This study develops a proposal of method of calculation useful to estimate the energy produced by a PV grid-connected system making use of irradiance-domain integrals and definition of statistical moment. Validation against database of real PV plants performance data shows that acceptable energy estimation can be obtained with first to fourth stati...

Although PV pumping is a mature technology, current PV pumping programmes show reliability deficiencies. This paper proposes procurement specifications and testing procedures in order to assure the technical quality of this kind of system. Testing facilities following the motto ‘keep it as simple as possible’, in order to make their application eas...

This paper describes the practical design of a portable capacitive load based on insulated gate bipolar transistors (IGBTs), which is used to measure the I–V characteristics of PV arrays with short-circuit currents up to 80 A and open circuit voltages up to 800 V. Such measurement allows on-site characterization of PV arrays under real operating co...

Inverter features are reviewed from a PV systems perspective, with a view to contributing to possible codes, procurement specifications and testing procedures, in order to assure the technical quality of these systems. A laboratory testing campaign has been carried out on a representative set of 16 currently available inverters and a set of the mos...

This paper presents the experience of a PV pumping project being carried-out in the South of Morocco since 1997. At present, the project has reached 18 villages, affecting 15 000 people. Total involved photovoltaic power is 46 kWp, and the total volume of pumped water since the installation of the systems approaches 0.7 × 106 m3. About half the PV...

Degradation phenomena can remain unnoticed over long periods in stand-alone PV systems, before eventually causing service interruption. Problems include battery capacity reduction because of ageing, PV array capacity reduction because of wiring corrosion or excessive dirtiness, and mis-adjustment of controller set-points. This underlines the practi...

IntroductionMovement between Sun and EarthSolar Radiation ComponentsSolar Radiation Data and UncertaintyRadiation on Inclined SurfacesDiurnal Variations of the Ambient TemperatureEffects of the Angle of Incidence and of DirtSome Calculation ToolsIrradiation on Most Widely Studied SurfacesPV Generator Behaviour Under Real Operation ConditionsReliabi...

Different information sources on solar radiation data are usually available for a same site. Significant discrepancies can be observed between these different sources, leading to a certain taste of incertitude. An in-depth analysis of such a problem reveals that this is coherent with the natural and unavoidable variability of the solar radiation ph...

This work experimentally evaluates some of the most referenced methods to estimate the global irradiance incident on tilted surfaces from measured global horizontal irradiance. Angular and spectral effects are also considered for the estimation of the "effective irradiance" to be used by PV modules in PV installations. Angular effects of pyranomete...