Extreme solar overirradiance events: Occurrence and impacts on utility-scale photovoltaic power plants in Brazil

Autores:
DO NASCIMENTO, LUCAS RAFAEL ; DE SOUZA VIANA, TRAJANO ; CAMPOS, RAFAEL ANTUNES ; Rüther, Ricardo
Evento:
Solar Energy
Resumo:

In contrast to the decades-long accumulated experience of photovoltaic (PV) installations in more temperate climates, the effects of some extreme operating temperatures and extreme solar irradiance levels start to become more noticeable with the uptake of large-scale PV in the sunbelt regions of the world. One such effect is caused by extreme solar overirradiance events, which up to now have been reported in the literature much more for their scientific interest than as a potential problem affecting the operational performance of PV power plants. Solar overirradiance events with a time span of tens of seconds or minutes are associated with the high operating temperatures prevailing in the field at many sites where utility-scale PV power plants start to become widespread, deleterious effects can be observed, which will negatively impact the performance of these generators. Using irradiance data from seven solar measuring stations deployed over distinct regions in Brazil, many of which are hosting megawatt-scale PV power plants, this paper reports on several extreme solar overirradiance events, with measured values above 1367 W/m2 up to 1845 W/m2, lasting from many seconds to a few minutes. Analysis of impacts and consequences from these events on the operational performance of PV generators are addressed, mainly focused on combiner box fuses, inverter overload losses, and inverter maximum power point tracker.

Ano:

Optimization of inverter loading ratio for grid connected photovoltaic systems

Autores:
MARTINS DESCHAMPS, EDUARDO ; Rüther, Ricardo
Evento:
Solar Energy
Resumo:

This study is aimed at performing and analyzing the inverter sizing optimization process for large-scale grid-connected solar photovoltaics (PV). The local solar resource was evaluated and compared to the available satellite data. Analyses of the solar irradiance distribution and its potential effects on inverter sizing were performed. The performance of five different, commercially-available PV module technologies was also evaluated by means of remote data analysis of irradiation and temperature, as well as electrical parameters. This was performed using the metrics of energy yield and performance ratio (PR) for PV systems. A methodology was developed for estimating the optimal inverter sizing in the region considering overload losses and economic aspects, aiming at the optimization and cost reduction of PV-generated electricity. Considering the five technologies, the mean yield was 150 kWh/kWp on a monthly basis. The annual PR ranged from 77% to 85% depending on technology. The local solar resource, measured during three years, was compared to five distinct satellite-derived solar databases. Cloud enhancement and cloud edge effects were observed through the monthly solar irradiation distribution over the three years of measurements. Around 28% of the incident annual irradiation was at irradiance levels at or above 1000 W/m2. The methodology developed for the optimal inverter loading ratio (ILR) was applied over one full year of solar generation data for the five technologies. It was observed that for inverter loading ratios commonly used on utility-scale PV power plants (around 120%), the overload losses varied from 0.3% to 2.4%, depending on technology. The optimal ILR for the more traditional crystalline Si PV technology was estimated to be 126%.

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The influence of the solar radiation database and the photovoltaic simulator on the sizing and economics of photovoltaic-diesel generators.

Autores:
DE FREITAS MOSCARDINI JÚNIOR, ERNESTO ; Rüther, Ricardo
Evento:
ENERGY CONVERSION AND MANAGEMENT
Resumo:

This study evaluated the outcome differences when adopting five different solar irradiation databases on the sizing of hybrid solar photovoltaic-diesel generators designed to supply electricity to isolated minigrids. To do this, the two most widely adopted photovoltaic (PV) simulation packages in the market, namely PVsyst® and HOMER Energy® were used. The different origins, data timespan, space and time resolution, of the five most relevant solar irradiation databases available for the region were compared. A case study was presented to illustrate the influences of the solar irradiation database and the solar simulation tool on the resulting PV generator. Furthermore, the hourly behavior of the energy supply to an existing load in a minigrid in the Brazilian Amazon was evaluated, together with the savings in diesel obtained with the resulting PV generator. Evaluating the five options of solar radiation databases, for the same PV plant configuration, variations of up to 19.7% were found in the expectation of PV generation. When the simulation software package was varied, the combined effect (radiation database X PV system sizing tool) showed differences of up to 20.6%. This demonstrates that despite having different algorithms, computational tools have a small influence (less than 1%) on results. These combined differences, taking into account the load curve behavior and the total diesel generation capacity installed at the site, resulted in over 100% differences in the optimum PV generator size in the case study. The total savings in diesel fuel, over a 15-years period, ranged from $ 6.5 million to over $ 16 million (>2.5 times) for the smallest PV system. This demonstrates the importance of the correct choice of database. These evaluations can be extended to minigrids of any size elsewhere. The novelty and originality of this study is to demonstrate and quantify for the first time the influence of the solar radiation database and the PV simulator package on the sizing of PV-diesel generators. The consequences of this study are not only of scientific and academic importance, but of economic and commercial interest as well.

Ano:

Performance assessment of solar photovoltaic technologies under different climatic conditions in Brazil

Autores:
DO NASCIMENTO, LUCAS RAFAEL ; BRAGA, MARÍLIA ; CAMPOS, RAFAEL ANTUNES ; NASPOLINI, HELENA FLÁVIA ; Rüther, Ricardo
Evento:
RENEWABLE ENERGY
Resumo:

Utility-scale photovoltaic (PV) generation is being ramped-up in Brazil in recent years, as a result of intense price reductions. Extreme operating temperatures, high humidity levels, and a blue-biased distribution of irradiance in comparison with the standard ASTM G-173 spectrum, lead to contrasting operational outputs of the various commercially-available PV technologies. The performance assessment of six different PV technologies installed at eight different climatic regions in Brazil is presented. This R&D project evaluates eight identical, 54 kWp Evaluation Sites (ESs), all with the following PV technologies: amorphous-silicon (a-Si), microcrystalline-silicon (μc-Si), cadmium-telluride (CdTe), copper-indium-gallium-diselenide (CIGS), mono- and multi-crystalline silicon (c-Si and m-Si). All installations operate at a fixed-tilt equal to the corresponding local latitude. Electrical and environmental parameters at all sites are measured continuously at 1-s intervals. Results show a detailed energy loss analysis for all technologies. Thin-film PV modules with a low temperature-coefficient of power presented superior performance. Crystalline silicon modules revealed intense degradation in areas with high relative humidity and temperature. Cloud-edge and cloud-enhancement effects of solar irradiance resulted in irradiance peaks of 1823 W/m2, with long overirradiance events which lasted many minutes over 1600 W/m2, resulting in frequent blowing of string fuses when manufacturers maximum fuse ratings were observed.

Ano:

ANÁLISE DE EFICIÊNCIA ENERGÉTICA NO PROJETO DO HOSPITAL UNIMED ALTO VALE EM RIO DO SUL ATRAVÉS DO REGULAMENTO BRASILEIRO DE ETIQUETAGEM

Esse presente trabalho tem como objetivo classificar a eficiência energética de uma edificação hospitalar. Foi aplicado o Novo Método de avaliação da eficiência energética com base em energia primária de edificações comerciais em um Hospital da Unimed localizado na cidade de Rio do Sul, Santa Catarina. Foram avaliados quatro sistemas: envoltória da edificação, sistema de iluminação, sistema de ar condicionado e o sistema de aquecimento de água.

Innovations in the Brazilian regulations for energy efficiency of residential buildings

Autores:
Michele Fossati; Rogério de Souza Versage; Marcio José Sorgato; Roberto Lamberts; Claudia Morishita
Resumo:

The implementation of energy regulations is the strategy most often used by governments to improve the energy efficiency of buildings. Based on Brazilian government incentives initiated in 2001 with Law 10.295, which regulates the National Policy for Conservation and Rational Use of Energy, Brazil has begun to develop methodologies for evaluating the energy efficiency of buildings. In February 2009 the Brazilian Energy Labeling Schemes for Commercial, Public and Services Buildings (RTQ-C) was published followed by the Brazilian Energy Labeling Schemes for Residential Buildings (RTQ-R) in November 2010. This article presents the methodology adopted by RTQ-R, the primary focus of which is the evaluation of naturally ventilated buildings, bioclimatic strategies for encouraging natural ventilation and daylighting, and evaluation of the water heating system. It also presents a review of House Energy Rating Schemes and shows the difference between the Brazilian Scheme and those applied by other countries. These differences are discussed and assessed herein.

Ano:

Assessment of technical and economical viability for large-scale conversion of single family residential buildings into zero energy buildings in Brazil: Climatic and cultural considerations

Autores:
Miguel Pacheco; Roberto Lamberts
Evento:
Energy Policy
Resumo:

This paper addresses the viability of converting single-family residential buildings in Brazil into zero energy buildings (ZEBs). The European Union and the United States aim ZEBs implementation to address ‘peak oil’ and environmental concerns. However, literature shows no agreement on a consensual definition of ZEB. Seeking a Brazilian ZEB definition, this paper addresses PassivHaus and thermal comfort standards for hot climates, source metrics for ZEB, Brazil′s energy mix, residential energy end uses and Brazilian legal framework for residential photovoltaic (PV) generation. Internal Rate of Return for PV systems in two Brazilian cities is calculated under various scenarios. It shows grid parity was reached from April 2012 to November 2012 assuming residential electric tariffs of that period and the financial conditions given by the Brazilian government for the construction of new dams in the Amazon and the lowest rates offered by Brazilian banks to private individuals. Governmental decision to lower electric residential tariffs in November 2012 reduced the scope of grid parity. Later revocation of a tax exemption in April 2013 ended grid parity in Brazil. It concludes, conversely to developed countries, it is the volatile Brazilian energy policy, instead of economical barriers, the main obstacle for ZEB viability in Brazil.

 

Ano:

Developing energy consumption benchmarks for buildings: Bank branches in Brazil

Autores:
Edward H. Borgstein; Roberto Lamberts
Evento:
Energy and buildings
Resumo:

The energy consumption of buildings is an area of increasing importance, and developing economies like Brazil must start to consider the energy performance of existing buildings. The publication of national energy benchmarks is a fundamental step for understanding energy consumption in commercial buildings and developing energy efficiency programmes. A voluntary data gathering initiative by the Brazilian Sustainable Construction Council (CBCS) is producing the data necessary to develop national benchmarks. A methodology for benchmark development is proposed, using both statistical data and energy audit data to benchmark end-use energy consumption, with the use of wet-bulb cooling degree hours for climate correction. Benchmarks and climate corrections are developed for the energy consumption of bank branches in Brazil. A simple linear regression analysis of data from 1890 bank branches in 57 different climates provides the energy consumption benchmark, while thermal simulation of building performance is used to validate the results and provide an end-use breakdown in the different climates studied. This work provides the foundation for further work to develop and publish national benchmarks in other typologies.

Ano:

A procedure for analysing energy savings in multiple small solar water heaters installed in low-income housing in Brazil

Autores:
Thalita Giglio; Roberto Lamberts; Miriam Barbosa; Mariana Urbano
Evento:
Energy Policy
Resumo:

Due to government subsidies, Brazil has witnessed an increase in the installation and use of small solar water heating systems in low-income housing projects. Although the initiative has reduced the load curve during peak times due to the reduced use of electric showerheads, measurement and verification (M&V) are needed to validate the savings. M&V procedures should take into account the social and economic variability of low-income housing developments. To improve M&V in low-income housing projects, this paper presents a methodology for identifying homogeneous subgroups based on their energy-saving potential. This research strategy involved a cluster analysis designed to improve the understanding of what energy savers and other influencing factors exist. A case study in Londrina Brazil was undertaken with 200 low-income families. Five clusters, created based on savings potential, were defined. The results showed that only two clusters demonstrated good electricity savings, representing 47% of families. However, two clusters, or 37%, did not provide satisfactory savings, and the other 16% did not provide any consumption history due to previous use of illegal city electricity connection practices. Therefore, studies confirm the need for a detailed measurement of the representative subgroups to assess the influence of human behaviour on potential SWHS-induced savings.

Ano:

Characterisation of representative building typologies for social housing projects in Brazil and its energy performance

Autores:
Maria Andrea Triana; Roberto Lamberts; Paola Sassi
Evento:
Energy Policy
Resumo:

In Brazil the housing deficit is around 5.5 million houses. To address this need, the government created a programme called “My house, My life”. The main subsidies of the programme are for families earning up to three times the minimum wage. In order to formulate strategies for more energy efficiency buildings, it is necessary to understand the thermal and energy performance of what is being built. This article defines representative projects for typologies being built in the Brazilian social housing sector through the analysis of 108 projects considering two groups of income levels and investigates the thermal and energy performance of the representative projects in relation to the Regulation for Energy Efficiency Labelling of Residential Buildings in Brazil for two bioclimatic zones. Five representative building models were defined. Considering the most common features found on the sample, the study suggests the importance of addresing energy efficiency measures on the sector since current building techniques for social housing shows a tendency towards a low performance in relation to the thermal and energy performance criteria of the Energy Labelling especially for lower income projects. This provides a basis for future policy and allows for more in depth studies within the sector.

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