Chigueru Tiba

Solar radiation in the Brazilian Northeast

The significant increase in recent years of the number of rural electrification systems (some thousands of them do exist) using photovoltaic technology installed in the Northeast of Brazil (1,500,000 km2, approximately 42 million people) used for illumination or water pumping, calls for an improvement on the design procedures in order to reduce the burden of capital costs per unit of generated power. Such objective can be accomplished as long as a better knowledge about the solar resource is achieved, considering how much these applications depend on it.

Solar energy resource assessment — Brazil

Appropriate information on solar resources is very important for a variety of technological areas, such as: agriculture, meteorology, forestry engineering, water resources and particularly for an innovating technology such as solar energy. In the market entry process of an innovating technology such as solar energy, the enlarged and sustained reproduction of this energy strongly depends on the economy and reliability of the demonstrative solar systems installed (within a restricted or wide scale). The economy and reliability of a system are the consequence of a well-prepared project, resulting from an accurate knowledge of the solar resource available. Therefore, knowing the potential of the solar resource accurately is not only a need, it is also an imperative for a larger diffusion and use of the solar energy.

Simulation model of a CPC collector with temperature-dependent heat loss coefficient

Abstract We describe a mathematical model for the optical and thermal performance of non-evacuated CPC solar collectors with a cylindrical absorber, when the heat loss coefficient is temperature-dependent. Detailed energy balance at the absorber, reflector and cover of the CPC cavity yields heat losses as a function of absorber temperature and solar radiation level. Using a polynomial approximation of those heat losses, we calculate the thermal efficiency of the CPC collector. Numerical results show that the performance of the solar collector ( η vs. Δ T f (0)/ I coll ) is given by a set of curves, one for each radiation level. Based on the solution obtained to express the collector performance, we propose to plot efficiency against the relation of heat transfer coefficients at absorber input and under stagnation conditions. The set of characteristic curves merge, then, into a single curve that is not dependent on the solar radiation level. More conveniently, linearized single plots are obtained by expressing efficiency against the square of the difference between the inlet fluid temperature and the ambient temperature divided by the solar radiation level. The new way of plotting solar thermal collector efficiency, such that measurements for a broad range of solar radiation levels can be unified into a single curve, enables us to represent the performance of a large class of solar collectors, e.g. flat plate, CPC and parabolic troughs, whose heat loss functions are well represented by second degree polynomials.

Softwares for designing, simulating or providing diagnosis of photovoltaic water-pumping systems

This paper identifies and evaluates software programs for designing, simulating and providing diagnosis of photovoltaic water-pumping systems available in the world market. The identified software programs were evaluated according to the following general criteria:C1summarizes their relative merits and their commercial availability, their updatedness (or whether they are updateable) and their user-friendliness;C2groups the software specific merits, its versatility and capacity to analyze multiple configurations of photovoltaic water-pumping systems and the completeness of the different parts of the system to be analyzed;C3groups the merits related to the database of parameters needed for running the software, in addition to the possibility of introducing new data;C4deals with the validation of the relevant software, using experimental data.Results for several commercial software programs analyzed according to these criteria are given.

Photovoltaic water pumping systems installer training: a partnership experience between the university and São Francisco hydroelectric power plant

A broad demonstration process of photovoltaic solar technology for the powering of rural areas lacking power and water supply is currently being developed in Brazil. Due to the severe and problematic drought that now impacts an extensive area of Brazil, particularly the northeast region, compromising agriculture and with a more serious consequence affecting water supply for human and animal consumption, emergency actions to mitigate these conditions are being undertaken. For this purpose, the Program for Energy Development in States and Municipalities (PRODEEM) aims to install approximately 800 photovoltaic water pumping systems, of which approximately 236 by mid 1999. The massive process of installation and maintenance of these systems, requires skilled technical staff. In order to accomplish such a broad program, the universities play a key role: the training of human resources. The Group of Research on Alternative Sources of Energy of the Federal University of Pernambuco (FAE/UFPE Group) has a long tradition on human resource training on solar energy, and it was invited to participate in this process by teaching training courses to several groups of middle-level technicians. Some 145 technicians, coming from several states of the northeast involved in the program were trained in only three weeks, after which they installed approximately 86% of the expected systems (225). The systems are now running in the communities. This paper provides a detailed report on the training process, on the course evaluation accomplished by the students, the difficulties and the logistic problems found, and the lessons learned.

Technical note On the development of spatial⧸temporal solar radiation maps: a Brazilian case study

This work summarizes recently published information on the solar resource of Brazil. We describe the spatial distribution of solar radiation and its relationship with climatic and geographical conditions. In order to harmonize the information in terms of type of instruments, time recording period and data processing methods, a careful selection of records from the data base was made. Density of recording stations is reasonable in the south, southeast and northeast regions of the country, while in the west center and north regions the density of stations is rather poor. The procedure to elaborate the maps of daily solar radiation, monthly and annual average is described. Consideration of the measuring period of the monthly averages, used to elaborate the contour maps, shows that they meet the requirement that 90% of averages are inside the strip of ±7.5%, centralized on the average of very long period measurements. We present one map with the localization of the recording stations and one annual and 12 monthly contour maps, describing daily solar radiation levels over the whole territory. Spacing among the contour lines is (±2 MJ⧸m2 day). Annual average of solar radiation lies within the interval of ((18±2) MJ⧸m2 day), except in the northeast region where values higher than (20 MJ⧸m2 day) are found. Two regions with levels of (16 MJ⧸m2 day) are also observed. The highest monthly average values (24 MJ⧸m2 day) are observed in the state of Rio Grande do Sul, southern end of the country, in the summer season (December and January). The lowest values in the country (8 MJ⧸m2 day) are observed in June and July (winter in the southern hemisphere), on the extreme south coastline of the same state, Rio Grande do Sul, below 32° south latitude.

Spatial Interpolation of Daily Solar Irradiation, Through Artificial Neural Networks

This work proposes an alternative for generation of synthetic series of daily solar irradiation from spatial interpolation using artificial neural networks (ANN). The estimations were obtained using geographic variables and meteorological variables, that are easily available. The data were measured between 2001 and 2006 in seven Brazilian localities of semi-arid tropical climate, in Northeast Region of the country. The estimations were carried out for the months of November, one of the months of higher incidence of solar irradiation in the region. For each locality a daily temporal series was estimated founded on what was learned from the experimental sequences of the other six localities. The daily solar irradiation calculated series when compared with the experimental series produced RMSE between 11% and 19%, depending on the local. The auto correlations of first order also are well reproduced with maximum deviation of 17%. Finally, the monthly accumulated irradiation values, calculated and experimental, have maximum deviation of 8%, thus, demonstrating their aptitude as input for long term solar system simulation.

A Gis-Based Decision Support Tool for Renewable Energy Management and Planning in Semi-Arid Rural Environments of Northeast of Brazil —General Description and Methodology

This work describes the development of a system of management and planning elaborated on a GIS platform (Geographic Information System) and is directed to decision makers, be they administrators, planners or consultants in renewable energy. It was conceived to deal with the management and planning of photovoltaic solar systems, biomass and aeolic energy in rural regions of the Northeast of Brazil. The prototype of the GIS tool covers an area of 183,500 km2 (in a second phase it will be extended to 1,561,178 km2) and it is made up of two main blocks: management of installed renewable energy systems and planning of insertion of new renewable energy systems. The system was mainly developed for PV systems as a possible tool of support for the management and planning of the Program of Energetic Development of the States and Municipalities (PRODEEM), a program of insertion of large scale photovoltaic solar energy (thousands of systems), in the rural environment, directed by the Ministry of Mines and Energy of Brazil. The tool for the management of the photovoltaic systems permits the execution of the technical analyses that are involved in the different combinations of the following layers of information: PV systems installed for the purpose of application (energetic, water pumping and others), identification of systems components, identification of component failures, maintenance and training posts, map of monthly mean solar irradiation, infrastructure access, electric transmission lines and distance from a given municipality to the nearest maintenance post. All the maps above can be combined in such a way that information at state or municipal level can be obtained. Additionally, in all the circumstances above, resulting thematic maps as well as issue reports can be printed. The tool for planning the insertion of new photovoltaic systems permits the execution of the technical analyses that are involved in the different combinations of the following layers of additional information: daily solar irradiation on the collector plane for the month of minimum solar irradiation, indices of non-electrified rural areas, indices of human development and localization of subterranean water wells. For each municipality there is the possibility of simplified dimensioning of the following systems: autonomous systems and systems interconnected to the electric network and for pumping water for a given demand and for a given manometric height. Finally the architecture of the GIS system for management and planning of renewable systems is open and permits a credential researcher to update data from diverse data banks and to program operations between thematic maps which were not previously foreseen. Due to limitation of the space only the general description and the methodology of development of the project will be described. The description of the software and its use for management and planning of the insertion of renewables sources of energy will be presented in other works.

Estimation of Hourly Ultraviolet Solar Irradiance in the Semi-Arid Northeast Region of Brasil

Two computational codes, SPCTRAL2 and SMARTS2, were used for estimating ultraviolet solar irradiance in a locality of the semi-arid region of the Northeast of Brazil. The softwares presented simplicity of use, precision and relative ease in obtaining the input variables: zenith angle, atmospheric pressure in relation to sea level, relative humidity of the air, amount of precipitable water, total ozone and the aerosol optic depths (AOD). All these variables are measured in conventional meteorological stations, except for the aerosol optic depth. The AOD was measured with an apparatus that was constructed with a narrow band LED sensor, centered in 555nm which measures the monochromatic radiation transmission through the terrestrial atmosphere, which can be described by Beer’s law. The measurements for obtaining the AOD were carried out during the months of December, 2006 and January, 2007 for Pesqueira-PE (Longitude-36.77° and Latitude 8.4°) semi-arid region of Pernambuco, at intervals of 10 and 10 minutes, simultaneously. The ultraviolet solar irradiation was measured with a TURV (Total Ultraviolet Radiometer) Eppley Pyranometer on a minute scale.