Rodrigo Barraza

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• Doctor of Philosophy
• Professor (Associate) at Adolfo Ibáñez University

The new PV technologies, such as bifacial modules, bring the challenge of analyzing the response of numerical models and their fit to actual measurements. Thus, this study explores various models available in the literature for simulating the IV curve behavior of bifacial photovoltaic modules. The analysis contains traditional models, such as singl...

The new PV technologies, such as bifacial modules, brings the challenge of analyzing the response of numerical models and their fit to actual measurements. Thus, this study explores various models available in the literature for simulating the IV curve behavior of bifacial photovoltaic modules. The analysis contains traditional models, such as sing...

Nowadays, public policies in Chile are geared towards the promotion of distributed energy resources (DERs) such as distributed photovoltaic (PV) systems. However, the prevailing socioeconomic context and the lack of incentive to invest in DERs have posed a challenge to achieving the established goals in the coming years. This paper develops a three...

This study presents a novel algorithm to evaluate the power losses in photovoltaic (PV) modules that are exposed to naturally accumulated soiling. The proposed algorithm uses red, green, and blue (RGB) images of the PV modules captured in the visible spectrum and measures features such as the average color intensity and standard deviation from ever...

A discrete 1-D Eulerian and 3-D Lagrangian model was developed to analyze heat transfer in packed beds composed of spherical particles to study a in more detail the solid phase phenomenon. The proposed thermal model simulates the particles using the discrete element method, generating a particle distribution inside the packed bed. It considers dire...

Comprehensive radiation studies on packed beds require the estimation of view factors between the surfaces, which often computationally expensive. This paper proposes a novel method based on Monte Carlo Ray Tracing for high-precision and low time computation processing of view factors in random assemblies of cylindrical packed beds. The Monte Carlo...

The influence of two operations modes in the solar field of a molten-salt power plant was investigated to evaluate how the receiver pipes’ fatigue life changes. Temporal and spatial DNI variation from the WobaS system were integrated with STRAL to obtain the energy flux that heats the working fluid. The temperature distribution over the pipe was ob...

The challenges encountered while concentrating solar radiation from multiple heliostats into a relatively small receiver have inspired numerous aiming methodologies to distribute such concentrated radiation. Likewise, this concentrated radiation, denominated heat flux, needs to satisfy certain constraints that primarily depend on the receiver geome...

This article presents an artificial neural network tool able to quantify the power loss due to soiling and partial shading effects of solar photovoltaic modules in the field, which may play a key factor on an optimal operation and maintenance of PV systems. The proposed approach uses visible spectrum RGB images of multiple solar panels and environm...

The bond calibration method (BCM) was designed as a calibration procedure to determine the effective Young’s modulus (E) of a compact aggregate of discrete bonded particles. By systematically varying the Young’s modulus of each particle–particle link (EB), the BCM adjusts the E of the aggregate, disregarding additional macroscopic parameters such a...

The work addresses the combined effect of temperature difference, longwave atmospheric heat exchanges and solar radiation in the thermal demand produced through walls with radiative insulation. It focuses in the all-year-round performance of a prefabricated wall panel based on multi-layer reflective insulation. The study has been carried out with a...

Solar central receivers have inherently large time constants and time delays caused by their thermal inertia are due to the transport of the heat transfer fluid alongside the panels. This problem is even accentuated if these systems are continuously exposed to direct normal irradiance (DNI) fluctuations. Ensuring an adequate operation of this kind...

This study proposes a business model to obtain a successful off-road machinery retrofit using fuel cell technology by the means of evaluating scenarios using the net present value NPV of the project as a figure of merit. Given the uncertainty of some parameters, such as the price of diesel, cost of hydrogen, and cost of technology. It is proposed t...

Integrating a multi-effect distillation (MED) process with a concentrated solar power (CSP) plant can enable a sustainable solution to meet our global society’s increasing energy and freshwater demands. This integration makes possible the ‘free’ reuse of waste heat from an advanced power block, albeit at slightly reduced thermal efficiency. As such...

Solar simulators have been widely used to characterize the performance of solar photovoltaics cells, which typically have a size of 156 × 156 mm². In order to amplify the testing area, a flexible optimal design method for solar simulators is presented in this study. In this work, 20 quartz tungsten halogen lamps are used with a light filter compose...

Natural vibrations can be harnessed using piezoelectric transducers and converted into electrical energy to power small electronic devices such as sensors network for structural health monitoring. One promising wind energy harvester configuration is a piezoelectric cantilever beam with a bluff body attached at the free end. The strain-induced into...

This paper describes the design of a prosthetic hand for wrist amputations. The mechanism considers the use of three actuators: one each for the movement of the little finger, annular finger, and middle finger. The second actuator controls the index finger, and the third controls the thumb. The prototype is considered relevant as it is able to move...

Research on natural cooling of buildings has produced an extensive scientific bibliography since 1980s. Nevertheless, few examples of complete experimental systems are registered, and rigorous procedures for their dimensioning are currently not available. This work analyses the performance of an air-based low energy radiative cooling system in Chil...

This study proposes a calculation methodology that determines the optimal boundary parameters of the single-diode photovoltaic model. It allows the calculation of the single-diode photovoltaic model when no reference parameter boundaries are available. The differential evolution algorithm, integrated with a step-by-step boundary definition module,...

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid s...

Thermocline tanks using packed-bed of rocks have become feasible candidates for improving the performance of Concentrated Solar Power plants, enabling high operating temperatures and reduced capital costs when industrial byproducts are employed as filler materials and low-cost working fluids, being competitive against molten salts thermal storage s...

The use of supercritical carbon dioxide (sCO2) cycle has been proposed as a promising alternative to replace conventional steam Rankine cycle. This study entails the development of a power cycle model to assess the impact of fluctuations on the heat source and environmental conditions on a recompression sCO2 Brayton cycle during off-design operatio...

Several authors have established single-tank packed-bed storage as a promising alternative that can be coupled with renewable thermal energy sources. The use of such systems can ensure a cost reduction of approximately 33%, compared to two-tank systems, which represents the dominating solution for high-temperature storage. Herein, an overview of th...

The performance of solar central receivers is inherently linked to the aiming distribution/cluster of heliostats over the surface of solar receivers. A reliable methodology is necessary to maintain the lifespan of these costly devices. This research presents a method for manipulating the heliostats' aiming within a solar field by using a group beha...

El trabajo aborda la elaboración de un modelo para estudiar la viabilidad de la implantación de los TABS (Thermo Active Buildings Systems) en edificios de oficinas en Chile, de forma que permita sentar las bases teóricas su diseño atendiendo a las circunstancias propias del contexto local, principalmente en diferentes realidades climáticas. Para el...

This study aims to build a potential map for the installation of a central receiver concentrated solar power plant in Chile under the terms of the average net present cost of electricity generation during its lifetime. This is also called the levelized cost of electricity, which is a function of electricity production, capital costs, operational co...

Some of the existing natural gas pipelines in Chile are underutilized; thus, these reservoirs could be utilized as Compressed Air Energy Storage (CAES) systems taking advantages of fluctuations in the price of electricity related to the entrance of renewable energy sources in the electrical market. A thermodynamic and economic-optimization of CAES...

Nowadays, microgrids are gaining importance in electric power generation and distribution environments due to their flexibility, versatility, scalability and the possibility of supplying ancillary services when connected to the grid. They allow for the customization of electric supply for very different types of consumers. Therefore, a new control...

This research presents the experimental and numerical results of a humidification dehumidification (HDH) unit driven by solar energy. The HDH unit is based in a CAOW water-heated configuration. The water is heated using solar thermal flat collectors. The desalination unit is located in the Renewable Energy Laboratory (LER) of the Universidad Técnic...

In the last five years, the Chilean Ministries of Agriculture and Energy developed a national strategy to incorporate renewable energies into various economic sectors. Since 2013, more than 1500 off-grid solar photovoltaic (PV) systems, with power ranging from 1 kW to 3 kW, were installed to drive existing irrigation systems in small and medium-siz...

This study presents a numerical model for a multi-effect distillation (MED) plant driven by solar energy. The model is based on mass, energy, and heat transfer equations applicable to the coupled MED and steam generation plants. The MED plant model has been validated with experimental data from the multi-effect distillation plant of the Plataforma...

Several authors have reported in the literature the benefits of transcritical carbon dioxide regenerative Rankine power cycles using low - and medium - temperature sources. However, their technical potential when driven by solar-thermal collectors has not been fully addressed yet. The methodology presented herein is based on two parametric analyses...

Zeotropic mixtures never have the same liquid and vapor composition in the liquid-vapor equilibrium. Also, the bubble and the dew point are separated; this gap is called glide temperature (Tglide). Those characteristics have made these mixtures suitable for cryogenics Joule-Thomson (JT) refrigeration cycles. Zeotropic mixtures as working fluid in J...

Supercritical carbon dioxide (sCO2) Brayton cycle is an emerging technology to be used as a power block with concentrated solar power (CSP) systems, tower type, sCO2 Brayton cycle has the potential to be competitive with traditional Rankine steam cycle. Most of the studies have been focused on the steady state analysis of this technology. This rese...

Solar thermal towers are a maturing technology that have the potential to supply a significant part of energy requirements of the future. One of the issues that needs careful attention is the heat flux distribution over the central receiver’s surface. It is imperative to maintain receiver’s thermal stresses below the material limits. Therefore, an...

Zeotropic mixtures are widely used in mixed refrigerant Joule–Thomson cryocoolers for various applications such as cryoprobes. Within the Joule–Thomson cycle, multicomponent mixtures exist in a two-phase condition throughout a large portion of the system. Frictional pressure drop correlations for zeotropic refrigerants operating at these conditions...

The use of mixed gas working fluids has become common in Joule–Thomson type cryocoolers for a variety of applications. However, there is a scarcity of data currently available with supporting theory capable of predicting the heat transfer coefficients associated with two-phase, multi-component mixtures at cryogenic temperatures. This paper aims to...

There is a scarcity of data and theory currently available regarding the heat transfer coefficients associated with two-phase, multi-component mixtures at cryogenic temperatures. This paper presents results of research aimed at measuring theconvection heat transfer coefficients for hydrocarbon mixtures (methane, ethane, propane, and nitrogen (for d...

The use of mixed gas working fluids has become common in Joule-Thomson (JT) type cryocoolers for a variety of applications operating in temperatures ranging from 80 to 230 K. The thermal efficiency of mixed gas JT cryocoolers is dependent on the optimization of the gas mixture composition. Most optimization methodologies focus on thermodynamic crit...

This paper describes an experimental facility designed and constructed to measure the heat transfer coefficients and frictional pressure drop in a small diameter, horizontal test section with two-phase, multi-component zeotropic mixtures at cryogenic temperatures. The aim of this facility is to enable the collection of high accuracy data to overcom...