Este trabalho apresenta uma análise acerca da obtenção de edifícios de energia zero (EEZ) em duas residências construídas sob o programa do governo federal brasileiro “Minha Casa Minha Vida” na cidade de Tijucas/SC, localizada na região da Grande Florianópolis. Como estimativa para consumo energético foram utilizados os métodos prescritivo e simplificado presentes na nova proposta para avaliação da eficiência energética das edificações, a Instrução Normativa Inmetro para Edificações Residenciais (INI-R).
Performance compromises of building-integrated and building-applied photovoltaics (BIPV and BAPV) in Brazilian airports
Civil aviation is a large and growing contributor to greenhouse gas emissions. The airports that host commercial flights are often national landmarks and architectural showcases. They are typically large, horizontal and free of shading, and are also ideally suited for the integration of photovoltaic (PV) systems for onsite generation of clean and renewable electricity. While ground-mounted PV generators should be designed for optimum performance, PV systems integrated on buildings should also consider aesthetics. We have analysed building-applied and building-integrated PV systems (BAPV and BIPV). In BAPV, optimised PV module orientation and tilt angles were proposed for maximum annual output, while in BIPV, modules were accommodated respecting the existing architecture of airport buildings. Two Brazilian airports were analysed, comparing the performance of BAPV and BIPV using two “off-the-shelf” PV technologies. On average, both the installed peak power and the energy generation density were found to be higher for BIPV (100% and 87%, respectively), while the final annual energy yield was 7% higher for BAPV. A compromise of pleasant integration and small energy losses was reached, which can assist in convincing clients and the public more than an ideally tilted and oriented PV generator that impacts negatively on the building's aesthetics.
Photovoltaics (PV) and electric vehicle-to-grid (V2G) strategies for peak demand reduction in urban regions in Brazil in a smart grid environment
Vehicle-to-grid (V2G) energy transfer in a smart grid environment opens a new revenue opportunity for electric-drive vehicles (EVs), and might reduce grid operation costs in demand-constrained urban feeders where peak-electricity prices are high. This paper analyses the peak demand energy market for V2G in the urban region of Florianópolis, Brazil. The article describes known V2G-concepts and introduces two different dispatch strategies developed for the Brazilian energy market in the light of new tariff regulations, which are expected to go into effect starting in 2014. It turns out that electric-drive vehicles may be used as a grid-stabilisation strategy, but the announced tariff regulations may lead to a destabilisation if there are too many cars offering their internal storage for V2G grid support. Adequate energy policy strategies must be introduced to avoid the conflicting interests that might stem from the different perspectives of grid operators and EV owners. In contrast to previous analyses, this research assumes the battery degradation as a function of depth of discharge (DOD), which is known for a specific battery.
Limitations in solar module azimuth and tilt angles in building integrated photovoltaics at low latitude tropical sites in Brazil
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.
The influence of government strategies on the financial return of capital invested in PV systems located in different climatic zones in Brazil
The Brazilian territory is irradiated with solar energy ranging from 1500 to 2300 kWh/m2/year, compared to 900 to 1850 kWh/m2/year in Germany, France, Italy and Spain. Despite that, photovoltaic (PV) technology is only now starting to penetrate the Brazilian electricity mix. Until recently, the high costs of PV generation had prevented this technology from competing in Brazil. However, the consistent PV price reductions and the worldwide scale reached, has brought attention to the Brazilian planners and actions have been taken recently in Brazil to help PV start its progress. In this paper, two of the recent government actions are analyzed, namely the National Electrical Energy Agency ANEEL Resolution RN482/2012, and the announcement of support by the Brazilian Development Bank offering loans at low interest rates for solar PV projects. The effects of these actions for residential PV systems are positive where the conventional electricity tariff is high with respect to the average in the country, and less relevant elsewhere. We compare these tariffs with the calculated Levelized Cost of Energy of rooftop PV generation. The influence of these policies on the return on investment of residential rooftop PV generation is studied for different climatic zones in Brazil.
Challenges such as partial shading and non-optimal tilt and azimuthal deviations are common in building-integrated photovoltaic systems (BIPV). Therefore, it is important to be aware of the consequences on systems performance metrics, namely annual specific yield and performance ratio for these specialised applications. This paper describes detailed analyses of shading effects, irradiation resource availability and module temperature on the performance metrics of individual subsystems of a rooftop BIPV installation in a high-rise building embedded in a high-density environment in Singapore. The study indicates that a shading analysis during the design phase can highly improve PV systems performance by giving careful consideration about shaded modules to optimise the PV module string design.
PV power conversion and short-term forecasting in a tropical, densely-built environment in Singapore
With the substantial growth of solar photovoltaic installations worldwide, forecasting irradiance becomes a critical step in providing a reliable integration of solar electricity into electric power grids. In Singapore, the number of PV installation has increased with a growth rate of 70% over the past 6 years. Within the next decade, solar power could represent up to 20% of the instant power generation. Challenges for PV grid integration in Singapore arise from the high variability in cloud movements and irradiance patterns due to the tropical climate. For a thorough analysis and modeling of the impact of an increasing share of variable PV power on the electric power system, it is indispensable (i) to have an accurate conversion model from irradiance to solar power generation, and (ii) to carry out irradiance forecasting on various time scales. In this work, we demonstrate how common assumptions and simplifications in PV power conversion methods negatively affect the output estimates of PV systems power in a tropical and densely-built environment such as in Singapore. In the second part, we propose and test a novel hybrid model for short-term irradiance forecasting for short-term intervals. The hybrid model outperforms the persistence forecast and other common statistical methods.
Energy performance evaluation of a net plus-energy residential building with grid-connected photovoltaic system in Brazil
The proposition of Net Plus-energy Buildings (NPEB) leads to the need to carry out studies of load matching in contrast with the grid impacts of distributed generation (DG). This paper performs simulations with the EnergyPlus software tool concerning a NPEB operating in four Brazilian metropolitan areas. The analyses include photovoltaic (PV) performance parameters and Load Matching and Grid Interaction indicators (LMGI). New grid impact indicators are defined in order to study the impacts of DG in the power grid. In the second stage, the work investigates economic aspects under net metering supporting. Results show the annual amount of electrical demand covered by PV varies from 29 to 51% with more potential in situations with higher PV production and higher cooling load, and the annual PV electricity that supplies the loads varies from 24 to 36% according to the seasonal variations of PV-load correlation. The levels of exported electricity into the grid are high in Brazil with annual mean power peaks surrounding 0.7 but can surpass 0.8 in the sunniest periods. The economy demonstrates the building achieves grid parity from 6 to 18% discount rates and the payback time is given for different scenarios of investment costs, discount rates and electricity tariffs.
Anthropogenic haze, caused at least in parts by forest and agricultural land clearing fires in Sumatra (Indonesia), is occasionally causing air quality issues in Singapore, located 150–300 km east of the majority of these “hot spots”. The resulting air pollution partially blocks sunlight from reaching the ground, and consequently affects the electric power generation of solar photovoltaic (PV) systems in Singapore. In this work, a methodology is presented to estimate the haze-induced reduction of the light intensity reaching PV panels and the corresponding loss in the electric energy yield. An assessment of a major haze event in June 2013 is the basis for the loss analysis, which takes into account data filtering techniques in order to isolate cloudless conditions for inter-comparison between clear and hazy days. Data from previous years in non-hazy conditions serve as baseline for the determination of the clear sky conditions for Singapore. The novel method is further applied to investigate the power output of ten PV systems in Singapore during the June 2013 haze event. It is found that poor air quality levels during this event caused yield losses of PV systems in Singapore in the range of 15–25%.