Antonia Sonia Alves Cardoso Diniz

Methodology for evaluation of grid-tie connection of distributed energy resources - Case study with photovoltaic and energy storage

The availability of reliable energy sources for all people, especially electricity, indicates an imbalance in the living conditions of a society. Therefore, new systems must be implemented to couple energy storage and renewable energy generation for the grid reliability improvement and increase access to electricity. This paper proposes a methodology to establish a general index focused on the insertion of distributed photovoltaic generation and energy storage using batteries. This methodology was applied in the IEEE 14-bus electric power system with load variation from different energy providers for the period of one year. The simulation results allow of the best performance evaluation to add distributed photovoltaic generation and/or energy storage in a real electric power system in different buses. The proposed methodology will allow planners to at the same time visualize different aspects by means of a single index that includes technical, economic and environmental aspects.

Fundamental Studies of Adhesion of Dust to PV Module Surfaces: Chemical and Physical Relationships at the Microscale

Photovoltaic (PV) module soiling is a growing area of concern for performance and reliability. This paper provides evaluations of the fundamental interactions of dust/soiling particles with several PV module surfaces. The purpose is to investigate the basic mechanisms involving the chemistry, morphology, and resulting particle adhesion to the first photon-incident surface. The evaluation and mapping of the chemistry and composition of single dust particles collected from operating PV module surfaces are presented. The first correlated direct measurements of the adhesive force of individual grains from field-operating collectors on identical PV module glass are reported, including correlations with specific compositions. Special microscale atomic force microscopy techniques are adapted to determine the force between the particle and the module glass surface. Results are presented for samples under dry and moisture-exposed conditions, confirming the effects of cementation for surfaces having soluble mineral and/or organic concentrations. Additionally, the effects of hydrocarbon fuels on the enhanced bonding of soiling particles to surfaces are determined for samples from urban and highly trafficked regions. Comparisons between glass and dust-mitigating superhydrophobic and superhydrophilic coatings are presented. Potential limitations of this proximal probe technique are discussed in terms of results and initial proof-of-concept experiments.

Fundamental studies of the adhesion of dust to PV module chemical and physical relationships at the microscale

PV module soiling is a growing area of concern for performance and reliability. This paper provides evaluations of the fundamental interactions of dust/soiling particles with a several PV module surfaces. The purpose is to investigate the basic mechanisms involving the chemistry, morphology and resulting particle adhesion to that first photon-incident surface The first-time evaluation and mapping of the chemistry of single dust particles from operating PV module surfaces is presented. The first direct measurements of the adhesive force of individual grains are reported, including correlations to the specific surface chemistry. Special nanoscale techniques using atomic force microscopy (AFM) are adapted to determine the force between the particle and the surface. Results are presented for samples under dry and moisture-exposed conditions confirming the effects of cementation for surfaces having organic/soluble mineral concentrations. Additionally, the effects of hydrocarbon fuels on the enhanced bonding and adhesive force of soiling particles to surfaces are determined for samples from urban and highly-trafficked regions. Comparisons between glass and superhydrophobic and superhydrophilic coatings are presented, showing the effectiveness of the lower-surface energy conditions on the particle adhesion. The potential, limitations of this novel proximal probe technique are discussed in terms of the results and initial, proof-of-concept experiments.

Soiling particle interactions on PV modules: Surface and inter-particle adhesion and chemistry effects

The understanding of the fundamental physics and chemistry of dust and the interaction of these soiling fragments with the PV module surface and each other is potentially important to developing viable mitigation approaches. This paper builds on our previous reports and observations investigating individual soiling particle adhesion on PV module glass using microscale proximal probe techniques. Specifically, in this presentation we report on the refinement of those adhesive force measurements by gaining and including information on the contact area of those particles with the surface, the specific chemistry of interactive surfaces, and the quantification of the force values using materials standard. We also investigate the adhesive forces holding the soiling particles together and the effects of the critical parameters of surface compositional properties, moisture (humidity), and hydrocarbons. This allows for the comparisons of the inter-particle adhesion to the adhesive force holding the particle to the glass module surface. These evaluations are performed on soiling particles collected from operating modules in differing climate zones in Brazil and Middle-East Gulf regions.

mc-Si thin films by hydrogen plasma assisted vacuum evaporation

In the present work the effect of auxiliary plasma assistance on the structure, composition and optical gap of e-beam vacuum evaporated silicon thin films is investigated. The films were deposited over glass and Silicon wafer substrates, under argon-hydrogen plasma assisted, to verify also the effect of the H2 content, at substrate temperature of 250 °C. The species present in the plasmas were investigated using Optical Emission Spectroscopy, while the films were characterized by Raman, FTIR and UV-vis spectroscopy. The results show that the deposition of a-Si:H with high hydrogen content and mc-Si:H through the used low temperature plasma assisted vacuum evaporation. The relationship between crystallinity, optical band gap and species in the Plasma is discussed, considering the effect of molecular and atomic hydrogen content in the plasma, as well as a-Si chemical annealing theories.

Neural representation of a solar collector with statistical optimization of the training set

One of the difficulties of using Artificial Neural Networks (ANNs) to estimate atmospheric temperature is the large number of potential input variables available. In this study, four different feature extraction methods were used to reduce the input vector to train four networks to estimate temperature at different atmospheric levels. The four techniques used were: genetic algorithms (GA), coefficient of determination (CoD), mutual information (MI) and simple neural analysis (SNA). The results demonstrate that of the four methods used for this data set, mutual information and simple neural analysis can generate networks that have a smaller input parameter set, while still maintaining a high degree of accuracy.

Monitoring of photovoltaic systems for performance evaluation and fault identification

The sustainability of standalone photovoltaic systems passes through an accompaniment of the systems installed in the field. To subsidize this accompaniment procedures had been developed for monitoring a similar system in a laboratory. The standalone photovoltaic system implanted in the Research Center in Intelligent Energy of the Group of Studies in Energy-CPEI GREEN PUC Minas is similar to the systems installed by Companhia Energetica de Minas Gerais-CEMIG in the schools of isolated communities, inside the solar light program. A simulation of the system was implemented and the aims were to optimize the project and carry out a comparative study with the monitoring results. The procedure for assembly of the monitoring facility consisted of the implantation of the voltage and current sensors, implantation of the irradiance and temperature sensors, installation of the acquisition boards and development of the monitoring program. The results presented here will allow the development of a program of preventive maintenance of the photovoltaic systems installed by CEMIG.

Correction to: A review on electric vehicles and their interaction with smart grids: the case of Brazil

In the original publication, the article was mistakenly published under the category “Perspective”. However, the correct category of the article is “Review”.

Dust in the wind: Soiling of solar devices: Is there a Holy Grail solution?(Conference Presentation)

Soiling, the sedimentation of particulate matter (on the size scale of 1/10 the diameter of a human hair) on the exposed surfaces of solar collectors, is a growing area of concern for solar-system performance, reliability, maintenance, and cost. In the case of photovoltaics (PV), the condition of this first-surface of interaction of the incident photons is critical for ensuring that the maximum-possible light reaches the conversion devices. This paper begins with a more than seven-decade historical look at the research invested into this problem, highlighting the motivation and milestones; the researchers and the progress. The current growing terrestrial markets for solar have brought a new focus on soiling and dust issues. That is because many of these new markets in the solar-rich geographic regions of our world are ironically also in the most dust-rich and soiling-prone ones as well. This paper continues to provide an overview of the status of current research efforts toward understanding the basic soiling mechanisms, the relationships to the PV technology approaches, the geographical differences (highlighting Brasil, India, and the MENA region) in the severity of the problem, the dust physics and chemistry—all relating to the current and future mitigation approaches. Included are some fundamental microscale through nanoscale examinations at how individual dust particles adhere to module glass surfaces—as well as how the particles might stick to each other under certain environmental conditions. These observations are used to show how fundamental science may lead to the macroscale engineering solutions of these soiling problems. This presentation is designed to both overview the soiling area and highlight some of the current and future research directions, speculate on short-term approaches preventing solar showstoppers, and speculate on some “holy-grail” schemes that might lead to the final solutions.

A Model to Estimate Ambient Conditions and Behavior of the Airflow Inside a Solar Chimney

This chapter presents models to estimate the environmental conditions and the behavior of the airflow within a prototype of a small-scale solar chimney located in Belo Horizonte, Brazil. A correlation from the literature for diffuse radiation, based on clearness index and global radiation, was evaluated. A model from the literature was used to estimate the ambient temperature of the device. The results of both parameters were compared with the experimental data. An energy balance was applied to find the heat interactions between the ground, airflow, coverage, and environment, based on the estimated incident solar radiation and ambient temperature. Literature correlations were used to estimate the convective heat transfer coefficients. Consolidated correlations were then applied to estimate the mass airflow rate and outlet temperature of the airflow inside the prototype. The results were compared with the experimental data for 4 days in autumn and good agreements were found. The model was then used to estimate the airflow parameters for 1 year. The analysis performed was transient, with results provided for each hour of the day, for 365 days. These results showed good accordance with the experimental data. The greater differences were found in the mass flow rate at night.