Carlos D. Rodríguez Gallegos

National University of Singapore | NUS · Solar Energy Research Institute of Singapore

This paper proposes an approach to optimize sizing and placement of photovoltaic solar panels (PV) and batteries in systems which employ diesel generators (DGs) as their only source of electrical energy, forming a PV hybrid system. Three objectives have been defined: reduction of the levelized cost of electricity (economic objective); levelized CO2...

This paper proposes a new optimization approach for the metallization design of solar cells and modules. While previous works have only optimized a maximum of two parameters at a time (which might lead to the loss of the optimal solution), we developed a graphic user interface tool in MATLAB called Photovoltaic Grid Optimizer (PV‐GO) which is able...

In many locations, grids are energized only by diesel generators (DG-only systems). Due to the requirements such as cost reduction and performance improvement, solar panels and batteries have increasingly been introduced into these grids. Nonetheless, many initiatives to hybridize the grids are still thwarted because of the high initial investment....

The present work studies the features of photovoltaic systems (PV) formed either by monofacial or bifacial crystalline p-type Si-based solar modules. To determine which module technology would be more favorable worldwide, a total of 55 locations around the globe are analyzed considering their weather profiles, market situation, and module electrica...

Multijunction solar cells offer a path to very high conversion efficiency, exceeding 60% in theory. Under ideal conditions, efficiency increases monotonically with the number of junctions. In this study, we explore technical and economic mechanisms acting on tandem solar cells. We find that these mechanisms produce limitations that are the more pro...

Solar panels are exposed to various pollutants in outdoor environments, such as dust, sediment, and bird excrement, which can cause the power generated by the panels to drop by up to 50%. To accurately estimate the power generated by photovoltaic (PV) systems, it is necessary to take into account the effects of soiling on the panels. In this paper,...

This study investigated variation in condensation (dew) and its effect on PV soiling, on a global level. Qualitatively, it is well known that condensation plays several roles in PV soiling: capillary adhesion and cementation cause dust particles to stick to the surface of modules, while run-off of dew droplets can clean them. However because outdoo...

As the installation of solar-photovoltaic and wind-generation systems continue to grow, the location must be strategically selected to maintain a reliable grid. However, such strategies are commonly subject to system adequacy constraints, while system security constraints (e.g., frequency stability, voltage limits) are vaguely explored. This may le...

High and continuously increasing photovoltaic (PV) penetration in distribution network introduces many potential power system problems. One of the most important, and often the first to arise, is overvoltage issue. Although many measures have been proposed and implemented to solve the problem, a standardised metric to assess their economic viabilit...

Solution processed SnO2 film has been demonstrated to be an efficient electron transporting layer for perovskite solar cells owning to its outstanding opto-electric properties. At the same time, SnCl2, SnCl4 and their hydrates are the most widely used tin sources for depositing SnO2 films. Herein, we demonstrate that tin oxalate (SnC2O4) can functi...

Interface engineering is a feasible strategy to passivate the defects located at both the surfaces and grain boundaries of the perovskite films. In this work, gentian violet, which is composited of a positive charged amine group and a negative charged Cl⁻ ion, is selected to engineer the MAPbI3/SnO2 interface. The gentian violet modified SnO2 film...

In photovoltaic power ratings, a single solar spectrum, AM1.5, is the de facto standard for record laboratory efficiencies, commercial module specifications, and performance ratios of solar power plants. More detailed energy analysis that accounts for local spectral irradiance, along with temperature and broadband irradiance, reduces forecast error...

Climate crisis is arguably the biggest challenge that the world is currently facing. Extreme weather events are becoming more frequent while the continuous rise in sea level is putting billions of lives will be at risk. Solving the climate crisis requires global carbon emission to peak by 2025, which means that carbon-intensive fossil fuels must be...

Together with rising renewable energy generation, energy storage installation is also growing, both at utility scale as well as behind the metre. Behind-the-metre energy storage systems (ESS) are netted out with load and is not dispatchable by the power system operators, making them invisible. While works in the literature have investigated the ben...

In the last two decades, the number of strategies for planning the maintenance of power systems have increased considerably. As societal dependence on power system infrastructure continues to grow, there is an increased need to identify the best practices in the field of power system maintenance planning to ensure the continued reliable operation o...

Module temperature is one of the main factors that directly influence photovoltaic energy production, and therefore, its precise modelling is of foremost relevance. However, most of the temperature models in the literature fail to acknowledge the transient effect due to the heat capacity of the PV module, as they instead model the temperature based...

Energy production of perovskite-based photovoltaic (PV) technology can be increased not only by improving device efficiency of perovskite solar cells (PVSCs) but also by innovative concepts such as bifacial and tandem configurations which require low-damage and highly transparent top electrodes. Herein, we report an amorphous CdO-In2O3 alloy film w...

Bifacial Photovoltaic (PV) modules are up taking an important market share of PV industry in the next few years. Rear surface irradiance modeling imposes significant challenges, as it lacks in reliable and standardized datasets. Besides, irradiance contribution and distribution depend highly on location and mounting conditions. A standardized metho...

In comparisons of solar photovoltaic performance, variation in the spectrum of sunlight is often neglected. A single spectrum, AM1.5, is used as the standard condition both for comparison of competing solar cell technologies and evaluation of energy generation from solar power plants. The addition of solar spectrum variation provides a more relevan...

As solar finds itself installed in further flung climes, so it must operate in harsher conditions. PV CAMPER, a collaborative effort including some of the world’s leading academic and research institutes, has set itself the aim of uncovering data to help drive the industry forward. Here, members of PV CAMPER discuss some of their preliminary findin...

Although the integration of solar photovoltaic (PV) systems is gaining widespread acceptance, the intermittency and instability of PV power generation lead to several operational challenges. PV power generation can be impacted by multiple environmental factors, such as the soiling of solar PV panels. There are some conventional methods proposed to...

Based on the behavior of the quantum particles, it is possible to formulate mathematical expressions to develop metaheuristic search optimization algorithms. This paper presents three novel quantum-inspired algorithms, which scenario is a particle swarm that is excited by a Lorentz, Rosen–Morse, and Coulomb-like square root potential fields, respec...

Many places around the globe are not connected to the mains utility grid as it may not be cost effective due to several factors, such as geographical conditions and low load demand, among others.

This work discusses some of the current limitations in the PV field and proposes strategies to address them by applying optimization approaches.

For solar cells and modules to collect the energized electrons and transfer them to an external circuit to deliver the energy, metallic contacts are necessary to be printed (fingers and busbars when fabricating the solar cells) and soldered (interconnector ribbons when fabricating the modules).

Dispatch strategy (also known as scheduling) refers to the operation and power control of the different energy sources in a system. In this study, the sources correspond to the PV system, battery system and diesel generators.

Solar cells correspond to the basic unit where the photovoltaic effect takes place.

Among the different materials for solar cells, Si crystalline based are the ones that dominate the current market (>90% [1, 2]).

This paper proposes a new method to optimize the scheduling of off-grid systems composed of solar panels, batteries, and diesel generators in real time. The approach takes into account the load and irradiance forecasted values for the near future to determine the optimal power generation and the operation of the different energy sources which achie...

This paper presents the methodology and preliminary results from a global study on solar over-irradiance events, which are more frequent than previously believed and can negatively impact utility-scale PV operations. Data from five test sites in Florianópolis and Brotas de Macaúbas in Brazil, Bernburg in Germany, Albuquerque, in the USA and Loughbo...

This book presents a study to determine the current limitations in the area of Photovoltaics (PV) as a source of renewable energy and proposes strategies to overcome them by applying optimization approaches in three main areas, namely related to photovoltaic solar cells, modules, and systems. These include grid metallization design of Si-based sola...

This report aims to describe the activities of the PV CAMPER initiative throughout the year of 2020, including the establishment of the collaborative database and the launch of different research projects.

Photovoltaic (PV) back-of- module (BoM) temperature measurements or estimations are key factors for the performance analysis and modeling of photovoltaic (PV) systems. Accurate module temperature estimation leads to more accurate energy yield predictions that are key determinants of investment value. Even though temperature prediction models have b...

Issues and challenges of integrating intermittent renewable energy from large photovoltaic (PV) systems have been a significant area of study. Numerous research works have analyzed the impacts of solar PV on the grid and highlighted various aspects to be the limiting factors for PV penetration. This two-part review paper assesses the overall power...

This article models the performance of photovoltaic tracking algorithms worldwide, based on the overall insolation collection, by comparing two tracking algorithms, namely tracking the sun (TS) and tracking the best orientation (TBO). In general, the latter is expected to receive higher irradiance with the drawback of requiring a higher installatio...

As the number of photovoltaic (PV) installations across the world keeps on increasing, their impacts on power systems are becoming more visible and more severe. In this two-part review, the implications of high PV penetration on the stability and reliability of power systems are comprehensively assessed. This paper, the first of the two, reviews th...

In this article, electroluminescence (EL) imaging is applied to characterize monocrystalline silicon photovoltaic (PV) modules under indoor and outdoor conditions. EL images of PV modules are analyzed to extract dark saturation current density and series resistance for individual cells within the module. These individual solar cells’ parameters tog...

This work presents a worldwide analysis on the yield potential and cost effectiveness of photovoltaic farms composed of monofacial fixed-tilt and single/dual (1T/2T) tracker installations, as well as their bifacial counterparts. Our approach starts by estimating the irradiance reaching both the front and rear surfaces of the modules for the differe...

Silicon-based multi-junction (tandem) technology is one potential route to the next breakthrough for terrestrial photovoltaic conversion. Significant progress has been made in tandem solar cells. To move forward, development of tandem module technology is essential. Here, we theoretically compare five possible tandem module architectures with multi...

The number of distributed energy resources (DERs) deployed in distribution systems has been rapidly increasing in recent years. Consequently, many researchers have proposed to utilise the DERs for local reactive power support. Yet, the expansion of infrastructure necessary to allow communication among the DERs, and with a centralised controller, ha...

A fast and non-destructive method based on electroluminescence (EL) imaging is presented to extract the front side resistive loss for individual cells within a crystalline silicon photovoltaic module. As the local luminescence intensity of a solar cell is an exponential function of local voltage, the voltage distribution along individual ribbons wi...

Albedo, the diffuse reflectivity of a surface, is an important quantity in photovoltaic (PV) performance evaluation and simulation, especially for bifacial module technologies. Our paper reports on a comparative study of albedo measurements at multiple sites worldwide. The Authors compare state-of-the-art methodologies used within the research coop...

Herein, we introduce the value of efficiency (VOE)—a metric defining the allowable cost for innovation by analyzing the co-dependence of levelized cost of electricity (LCOE) on manufacturing cost and efficiency. Historically, VOE values have dropped rapidly and will further, yet slower, decline in the future. Additionally, VOE values for residentia...

This work proposes an approach to optimize the grid metallization design (number, width, and height of fingers, as well as number and width of busbars and interconnector ribbons) of monofacial and bifacial photovoltaic (PV) Si-based solar modules mounted at a fixed tilt. We aim to optimize the module energy generation at the locations where they wi...

Electric Vehicles have been receiving increasing attention. As the number of electric vehicles increases, uncoordinated charging of electric vehicles can lead to voltage and frequency instability in microgrids. Various methods have been proposed for electrical vehicle coordination, where most of them focused on controlling active power. Vehicle-to-...

With the increasing adoption of photovoltaic systems (PVs) in distribution grid, many researchers and grid operators have proposed and started to utilise PV inverters for local reactive power compensation (RPC). The local RPC has been shown to reduce losses in the system, and to help maintain voltage within acceptable range. Moreover, RPC using PV...

Laser ablation using ultrashort pulses is becoming more relevant in the fabrication of solar cells due to their ability to produce well-defined grooves. In this work, laser grooving of dielectric layers using laser pulses of 480 femtosecond and 515 nm (green) wavelength at various pulse fluences and pulse overlaps is presented. The dielectric is ei...

Photovoltaic system (PV) inverters have been frequently utilised for reactive power support in the literature. Although the benefits of PV reactive power for the grid have been quantified, the costs incurred by the PV owner have largely been ignored. This work combines the findings from power electronics research and power system economics to formu...

This paper proposes a new method to determine the sizing and siting of diesel generators (DGs), photovoltaic solar panels (PV) and batteries for off-grid systems. In this work, the objective is to reduce total system cost while fulfilling the load demand and maintaining power quality of the system, among other constraints. This is achieved by emplo...

This study presents an innovative design for the optimal sizing, placement, and dispatch approach of distribution static var compensators (D-SVCs) in a radial power distribution system to improve the technical and economic aspects of the grid. The approach incorporates the total harmonic distortion (THD) effects into the assessment with the presenc...

This work proposes an analytical approach for reactive power dispatch and energy arbitrage in grid-connected distribution systems with distributed energy resources. The comprehensive approach minimizes the operational cost of the system while incorporating the price of electricity, cost of reactive power, reactive power charge, line losses, and ene...

Previously in “Reconciling solar forecasts: Geographical hierarchy” [Solar Energy 146 (2017) 276–286], we have demonstrated that by reconciling the forecasts obtained from a geographical hierarchy (formed by levels such as transmission zones, distribution nodes, PV plants, subsystems and inverters), more accurate forecasts can be obtained as compar...

With the increasing adoption of photovoltaic systems (PVs) in distribution system, many researchers and commercial companies have proposed to utilise PV inverters for local reactive power compensation (RPC). However, the technical and economic competitiveness of the inverters have not been compared against traditional reactive power devices such as...

This work analyses the economic and technical impact of local reactive power provision in grid-connected microgrids with distributed energy resources. Costs of reactive power provision by photovoltaic systems and battery energy storage systems are explicitly formulated and an objective function incorporating the costs is proposed. The advantage of...

This paper reports on the ablation and microstructuring properties of dielectric layers using a high average power femtosecond and nanosecond laser sources. The dielectrics investigated include SiNX, AlOX/SiNX stack and thermal SiO2/SiNX stack deposited on planar n-type silicon wafer. Initially, single pulse ablation properties such as threshold fl...

Photovoltaics (PV) degradation is a key consideration during PV performance evaluation. Accurately predicting power delivery over the course of lifetime of PV is vital to manufacturers and system owners. With many systems exceeding 20 years of operation worldwide, degradation rates have been reported abundantly in the recent years. PV degradation i...

This paper proposes a new method to determine the placement and sizing of diesel generators (DGs), photovoltaic solar panels (PV) and batteries for off-grid systems. In this work, our objective is to reduce the total system cost while fulfilling the load demand and mantaining the grid power quality, among other constraints. This is achieved by empl...

With increasing complexity and unpredictability in power systems, optimization of power dispatch is now more important than ever. It is imperative to overcome the challenges brought about by the rise of renewable energy sources (RES) and electric vehicles (EVs) and to capitalize on the opportunities that they present. The aim of this paper is to gi...

As photovoltaic systems (PV) and electric vehicles (EVs) are becoming more widespread, it is now possible to utilize them to provide reactive power support. To capitalize on this possibility, continuous reactive power optimization from PV and EVs' stationary chargers has been proposed and optimized using particle swarm optimization in this paper. A...

The scope of this paper is to analyze the performance of a homemade dye sensitized solar cell (DSSC) which presents a high potential based on its low fabrication costs and wide application field. In this investigation, the procedure to create a homemade DSSC is given. Its parameters are analyzed obtaining an efficiency of 26.4•10-4% (IV measurement...

The behavior of a photovoltaic solar array is investigated by performing a simulation in Simulink (MATLAB). The modeling of the system is based on the one diode model (in which the solar cell’s equivalent circuit is composed by a current source, diode, series and parallel resistance). The simulation results show how the series and parallel connecti...

This study summarizes the results of several medium scale cell experiments on the new dispensing machine, demonstrating cell efficiencies of up to 19.7% on industrial Cz Al-BSF material. Latest enhancement of the dispensing device further allowed for a significant reduction of wet paste laydown of down to 70 mg for the front contact finger grid whi...

In this paper, the potential of contact geometries applied by dispensing, single and double screen printing, are analyzed with respective modeling and simulations at cell and module level. Industrial Cz-Si p-type 156x156 mm² Al-BSF cells are processed to compare the measured values with the estimated ones. A parallel ten nozzle fine line unit is us...