• Energy Research

The sizing of photovoltaic (PV) systems has been a concern since the 1990s, particularly with the trend of inverter undersizing as PV module prices decrease. While many studies have assessed the behavior of AC energy and economic parameters with varying Inverter Load Ratios (ILRs), they often neglect the impact of degradation on system lifetime or fail to analyze how it influences ILR selection in depth. This study examines the relationship between DC loss curves and ILRs, their evolution over time, and their effects on efficiency and Final Yield. Simulating solar resources in 27 Brazilian cities, it evaluates clipping losses and optimal ILR values ranging from 0.8 to 2.0 for 28 recent inverters. The research aims to identify the ILR that minimizes the Levelized Cost of Energy (LCOE) while maximizing Final Yield, revealing variations in optimal ILR ranges across different inverter–city combinations. The optimal ILR was between 1.1 and 1.3 for modern medium- and high-power inverters, while low-power inverters had a range of up to 1.8. The findings highlight that practical ILR considerations can overlook real-world challenges, leaving the system’s full potential untapped.

Abstract - This paper describes a novel methodology for estimating the shading factor and the irradiance in partially shaded photovoltaic arrays. The results indicate that the monitoring of short circuit currents obtained from the IV curves of shaded and unshaded modules can be used to calculate the overall irradiance on partially shaded and not shaded photovoltaic arrays. This new methodology avoids the need to use several irradiance sensors to map the shaded and unshaded regions. Besides that, this paper presents a simple mathematical model to estimate shading losses on SPV arrays at the points of maximum global and local power. The methodology can be described in five steps: the measurement of the IV curve and cell temperature, pre-processing of the IV curve, calculation of the shading factor and irradiance on the shaded and unshaded areas, use of the photovoltaic array model to obtain the simulated IV curve and the shading level distribution in the array. The proposed model was developed using the methodology presented in this work, demonstrating how useful it can be to validate and develop models applied to evaluate the shading effects. Calculated losses are compared to those obtained with models found in the literature. The proposed model is useful for calculating the instantaneous power losses, requiring less information as input than other detailed models, and requiring low computational effort.

Abstract Air conditioning systems (ACSs) represent one of the main demands for electricity in residential, commercial, and industrial buildings. The use of a photovoltaic air conditioning unit (PVACU) represents an attractive application to this demand for reasons such as environmental concerns and the match between diurnal cooling load and solar resource. A PVACU consists of a photovoltaic generator (PVG) that supply an ACS through direct current to direct current and frequency converters, without energy storage. This system considers the natural adjustment of the ACS cooling capacity according to the PVG power. Modeling the ACS, the PVG, and the thermal load (TL) makes possible to evaluate PVACU performance. For this, a small library’s TL and an ACS supplied by a PVG were used as case study. The PVG installed capacity assumes values of 700, 1000, and 1400 Wp. The simulation results show that the PVACU with a 1400 Wp PVG would be sufficient to regulate internal temperature within international comfort standards in the range of 20 °C to 24 °C. According to the data obtained in the simulations, it was possible to conclude that the PVACU has a large potential to be used in air conditioning of other environments in regions with Amazonian climatic conditions.

AbstractThis work presents the utilization of mathematical models which represent the energy processing on Grid-Connected Photovoltaic Systems. Such models are part present on literature and part proposed by the authors. All models are implemented in MATLAB GUIDE code which allows the analysis, helps on the design and permits the operational behavior and energy contribution simulation of GCPV with different sizes. The work also presents comparison between the data generated by the program and some measured data from installed Grid-Connected Photovoltaic Systems.

Abstract In this paper, a fuzzy logic based Mandani-type controller is applied to an industrial frequency converter to couple a photovoltaic generator to a conventional centrifugal pump for water pumping applications. The system operates in closed loop and the DC bus voltage regulation of the frequency converter is done indirectly by varying the speed of the pump according to the power provided by the photovoltaic generator. In order to decrease the number of series-connected modules, the working voltage of the photovoltaic generator (maximum power point voltage) must be as close as possible to the minimum voltage limit required by the frequency converter’s input. The proposed algorithm was embedded in a general-purpose microcontroller. Controller performance was evaluated through tests on an experimental bench that allows simulating different water heads. Experimental results shows that the speed of the proposed fuzzy controller allows the operation close to the lower DC voltage limit imposed by the frequency converter, making possible the use of photovoltaic generators with a reduced number of PV modules in series (in this work, 30% fewer modules). The fuzzy controller regulates the photovoltaic generator voltage throughout the day, avoiding frequency converter limitation due to undervoltage errors, even with sudden changes in irradiance.

This paper presents results of one-year monitoring of AC side electrical parameters and the characterization of local solar radiation at the biggest rooftop PV Power Plant, with an installed capacity of 1.42 MWp, mounted at Mineirão Football Stadium in Brazil. This stadium is one of the sport facilities that hosted 2014 FIFA World Cup and Rio 2016 Summer Olympics Games in the country. Results showed how it is important to study and characterize the solar resource in the region of interest, based on historic data, to provide the understanding of solar radiation and thus project PV power plants with better performance. Furthermore, AC electrical data show the behavior of active, reactive and apparent powers and the influence of the PV system on the power factor at the local grid utility connection point. Finally, PV power plant performance data (as annual final yield, performance ratio and capacity factor) are also presented and compared with data from PVsyst software simulations. The results over the monitoring period were good considering the specificities of the stadium

This paper presents the development stages of a micro-scale system for electricity generation from biomass with 500 W of power. The proposed system is based on an open steam power cycle, whose conception was aimed at seeking solutions to meet the needs for energy supply in isolated communities in the Amazon region. In addition the great biomass potential in the region is an opportunity for the application of biomass energy to increase the economic activity and develop new technologies. The tests performed demonstrate that the steam turbine is the critical component to the commercial-scale feasibility of the presented technology, particularly when it's proposed manufacturing of the system by small regional industries.

Abstract This paper presents a methodology that uses the Monte Carlo Method (MCM) to estimate the behavior of economic parameters which may help decision, considering the risk in project sustainability. In order to show how this methodology can be used, a Grid-Connected Photovoltaic System (GCPVS) of 1.575 kWp, located on the roof top of the laboratory building of the Grupo de Estudos e Desenvolvimento de Alternativas Energeticas – GEDAE, at the Universidade Federal do Para – UFPA, Belem – Para – Brazil, and operating since December 2007, is analyzed. This system was chosen because it was the first GCPVS installed in the Brazilian Amazon Region, being the first risk evaluation on using a renewable energy source connected to the grid in the Region. This work also presents a similar treatment for the case of a stand-alone photovoltaic system (SAPVS) installed in the remote Santo Antonio Village, municipality of Breves, Para, Brazil, considering the risk of investment assumed by an investor in power generation projects with similar characteristics or using other renewable energy sources. The last case allows a better assessment for other important applications of renewable energy in the Amazon Region, where the demand for energy is growing, but is still costly and often not a priority in government actions.

ABSTRACTThis paper presents the main problems found in photovoltaic systems in the Amazon Region and the actions to be performed for restructuring and correcting the operation of such systems. These problems and solutions are exemplified on the basis of the diagnosis and revitalization of the 2.5‐kWp photovoltaic installation that belongs to the central module of the Uacari Floating Lodging House. The paper was accomplished as part of the agreement between the Group of Studies and Development of Energy Alternatives (GEDAE) and the Mamirauá Institute of Sustainable Development to assess several photovoltaic facilities in the area covered by the institute. Concluding the paper, some operational results of the revitalized system are presented. Copyright © 2011 John Wiley & Sons, Ltd.