Cláudio Dias Campos

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.

Fuzzy Coefficients and Fuzzy Preference Relations in Models of Decision Making

Analysis of models is considered as part of a general approach to solving a wide class of optimization problems with fuzzy coefficients. This approach consists in formulating and solving one and the same problem within the framework of interrelated models to maximally cut off dominated alternatives. The subsequent contraction of the decision uncertainty region is based on reduction of the problem to multiobjective decision making in a fuzzy environment with applying techniques based on fuzzy preference relations. The results of the paper are of a universal character and are already being used to solve power engineering problems.

Fuzzy Preference Relations and Multiobjective Decision Making

Analysis of models is considered as part of a general approach to solving optimization problems with fuzzy coefficients. This approach consists in formulating and solving one and the same problem within the framework of mutually interrelated models with constructing equivalent analogs with fuzzy coefficients in objective functions alone. The use of the approach allows one to maximally cut off dominated alternatives. The subsequent contraction of the decision uncertainty regions is based on reduction of the problem to models of multiobjective decision-making in a fuzzy environment with the use of fuzzy preference relation techniques for analyzing these models. Three techniques are considered in the paper. The first technique is of a lexicographic character and consists in step-by-step introducing criteria (fuzzy preference relations). The second technique is based on building of a membership function of a subset of nondominated alternatives with simultaneous considering all preference relations. The third technique is related to aggregating membership functions of subsets of nondominated alternatives corresponding to each preference relation. The results of the paper are of a universal character and are already being used to solve problems of power engineering and management.

Delay-dependent H∞ control stabilization of linear systems with time-varying delays 1

Abstract This paper proposes a Linear Matrix Inequality (LMI) approach to the robust H ∞ control stabilization problem of uncertain continuous- or discrete-time linear time-invariant systems with time-varying delays in the state vector and control input. It is derived sufficient delay-dependent conditions for the control stabilization problem, where both the size of the time-varying delay and the size of its time derivative (applicably only in the continuous-time case) play a crucial role for the closed-loop stability with a guaranteed H ∞ level. The solutions that are found for the H ∞ control problem are similar or less conservative, when compared to others approaches.

IPUC's Technological Fair: Space of opportunity and experience for new technologies and space from perceptions of social impacts of technologies

This paper aims to show the IPUCs Technological Fair, an event that is held twice a year by Polytechnic Institute of Pontifical Catholic University of Minas Gerais - IPUC, is currently in its 6th edition. The creativity and innovation of most of these projects from engineering students frequently result in simple and low cost solutions. These projects involve around one thousand students from several areas of engineering of IPUC and they are exposed in the bustling fair. Both issues gained in joining the formation team to work with the challenges of the poverty and development sustainable. The creation of the group IEEE SIGTH PUC Minas was a natural way. The presentations of prototypes and research results are the main advantage of the fair. Various topics have being worked, such as, entrepreneurship including the entrepreneurship social, the accessible and assistive technology, medical technology and of the health, therefore Humanitarian Technology. Renewable resources with several kinds of applications Interdisciplinary Projects can providing to engaged students important skills of self reflection, communication with others forms of the knowledge and holistic view.

Customizing conventional computer peripherals in the benefit of low income individuals with disabilities: Step by step procedures to make by yourself

Aware of the gap that exists between the social rights protected by laws and its full enjoyment, a multidisciplinar team composed of engineers, educators and brazilians students, joined to develop assistive technology products that contribute to the inclusion of people with disabilities, especially those low-income people. This paper presents a successful experience of this team on the development of valuable technology assistive products with low-tech. Construction procedures that describe how to transform conventional computer peripherals such as mouses and keyboards in custom devices for people with physical disabilities will be presented in details. These procedures were conceived in order to design functional, durable and low-cost products. The group uses the Internet in order to publicly disseminate their knowledges and projects.