Search

This paper proposes a simplified method to determine an index to quantify the influence of partial shadings on the performance of BIPV systems based on the relation between the shading percentages and the reduction of the incident irradiation on a given surface. The research is divided in two papers: Part 1: Theoretical study and Part 2: Application in case studies. Part 1 consists in identifying and quantifying the shading on a surface, and relates the fraction of shaded area with the percentage of incident irradiation reduction during the same period, in order to propose a shading index (SI) that represents the energy losses due to shadings on PV systems. The method was developed for a theoretical shaded case study simulated in two cities located at low latitude, tropical regions: Singapore (1.35°N) and Florianópolis-Brazil (27.48°S). Results showed that the shading percentage on the analysed surface on an annual basis is closer to the percentage of incident irradiation reduction at same period than when these values are compared on other time bases, as hourly, daily or monthly. Therefore, in this case, the annual percentage of shading can be adopted as the SI. SI was validated using different computer software packages and it was proved to be a convenient way of estimation the PV generation of similar cases of partially shaded PV systems, that could be used even before the PV electrical desing has been done. [ABSTRACT FROM AUTHOR]

This is the second part of the paper “Simplified method for shading-loss analysis in BIPV systems”. The objective of Part 2 is to apply the simplified method described in Part 1 in order to estimate the influence of partial shadings on the performance of four installed and in operation BIPV systems. The method consists in identifying and quantifying the shading on a surface, relating the fraction of shaded area with the percentage of incident irradiation reduction during the same period, in order to propose a shading index (SI) that represents the energy losses on partially shaded PV systems. SI was validated through the analysed case studies and it was proved to be a convenient way of estimating the PV generation of partially shaded PV systems. This method is independent from the electric configuration and can be used for already installed PV systems, or surfaces under investigation for PV installations, both through manual calculations and also through calculations using dedicated software packages. [ABSTRACT FROM AUTHOR]

Abstract: Photovoltaic (PV) generation depends directly on the amount of radiation received by solar modules at a given temperature, and annual irradiation varies according to site location and PV array position. In this paper, the limitations and the solar irradiation levels received by building surfaces in different positions (with azimuth and tilt angle variation) in capital cities in Brazil are shown, making use of the Brazilian global horizontal solar irradiation data provided by the SWERA (Solar and Wind Energy Resource Assessment) project. These data were processed to generate figures on the irradiation at various PV module orientations and slopes for each city, which show the relative radiation levels received on specific azimuth and tilt angles in relation to the ideal position. Results were validated using four real and operating PV systems. In general, variations in azimuth or slope did not cause large annual irradiation losses up to around 20° tilt angles. This shows to PV system planners that under these fairly flexible conditions it is possible to install PV on any orientation, keeping high levels of annual irradiation, and that limitations in orientation and tilt can be relatively low. It also allows a quick analysis of PV retrofit in building-applied photovoltaics (BAPV), when seeking the best building surfaces to incorporate PV. [Copyright &y& Elsevier]

Abstract: The integration of solar modules on buildings’ roofs and façades is one of the most elegant applications of photovoltaics (PV). With the declining costs of this technology, building-integrated and building-applied photovoltaics (BIPV and BAPV) can efficiently and cost-competitively assist in delivering electricity in urban environments. We have quantified the potential of BIPV and BAPV generators on existing single-family detached residential buildings in Florianopolis–Brazil (latitude 27°S, solar irradiation 1550kWh/m2/year), in supplying each house and a fraction of the local utility feeder''s electricity demands. We have measured and compared the annual output performance of thin-film amorphous silicon, and traditional crystalline silicon solar PV technologies, and proposed solar PV kits to be installed on all of the existing 496 residential buildings roof tops in the mixed residential–commercial area studied. The typical single-family, detached home roof covers can easily accommodate the proposed PV kits, with 87% of these generators yielding at least 95% of the maximum theoretical generation output of an ideally oriented and tilted PV system. Low-pitched, existing roof covers in residential houses represent excellent areas for PV integration at low latitudes. Installing BIPV on all of the available roof areas can make each and every house a net energy-positive building. [Copyright &y& Elsevier]

Abstract: Brazil faces a continuous increase of energy demand and a decrease of available resources to expand the generation system. Residential buildings are responsible for 23% of the national electricity demand. Thus, it is necessary to search for new energy sources to both diversify and complement the energy mix. Building-integrated photovoltaic (BIPV) is building momentum worldwide and can be an interesting alternative for Brazil due its solar radiation characteristics. This work analyses the potential of seven BIPV technologies implemented in a residential prototype simulated in three different cities in Brazil (Natal, Brasília and Florianópolis). Simulations were performed using the software tool EnergyPlus to integrate PV power supply with building energy demand (domestic equipment and HVAC systems). The building model is a typical low-cost residential building for middle-class families, as massively constructed all over the country. Architectural input and heat gain schedules are defined from statistical data (Instituto Brasileiro de Geografia e Estatística—Brazilian Institute for Geography and Statistics (IBGE) and Sistema de Informações de Posses de Eletrodomésticos e Hábitos de Consumo—Consumer Habits and Appliance Ownership Information System (SIMPHA)). BIPV is considered in all opaque surfaces of the envelope. Results present an interesting potential for decentralized PV power supply even for vertical surfaces at low-latitude sites. In each façade, BIPV power supply can be directly linked to local climatic conditions. In general, for 30% of the year photovoltaic systems generate more energy than building demand, i.e., during this period it could be supplying the energy excess to the public electricity grid. Contrary to the common belief that vertical integration of PV is only suitable for high latitude countries, we show that there is a considerable amount of energy to be harvested from vertical façades at the sites investigated. [Copyright &y& Elsevier]