University of São Paulo: Urban centers have the potential to generate wind energy with turbines on top of buildings

FORA survey made at the Institute of Energy and Environment (IEE), in partnership with the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG), both from USP, demystifies the idea that wind energy can be generated only by giant turbines installed in areas open, where the winds are constant and unilateral. The study showed that winds that strike urban centers, amidst buildings, can also be sources of clean and renewable energy. This was the conclusion of a master’s thesis whose proposal was to evaluate the wind potential of installing small wind turbines (APPs) in a building located in the central region of São Paulo, where wind conditions are unstable, turbulent and low speed due to the presence of obstacles.

Research
The sensors for collecting anemometer data – wind direction, speed, intensity, constancy and temperature – were placed in meteorological towers installed on top of the 18-story building of the São Paulo State Department of Finance, in the neighborhood da Sé, central area of ​​São Paulo. Measurements took place from 2014 to 2018. Every day, every five minutes, for a period of four years, these variables, which help to estimate the wind turbine’s power generation capacity, were captured and analyzed.

Compiled the wind data, the average wind speed found during the analyzed period was 3.92 m/s (meters per second). In the months of September, October and November, the wind speed reached the best indexes, around 5.0 m/s, between the hours of 13 and 20 hours; the months of May, June and July had the worst rates.

With the data in hand, the researcher crossed the variables found with the power curve (chart that indicates the electrical power available in the wind turbine for different wind speeds) provided by the manufacturer of four models of small wind turbines – Skystream 3.7, Proven 2.5, Raum 3.5 and Hoyi 300. Of these models, the turbine with the best energy efficiency was the Proven 2.5, with energy generation estimated at 4,330 kilowatts (kWh)/year. Assuming that the average residential consumption in Brazil is around 152 kWh/month, it would be possible to easily supply two homes with the energy generated by Proven.

WIND TURBINE PRICE R$ INSTALLATION R$ POWER GENERATION

The period for the return on investment, if the Proven 2.5 wind turbine were installed on site, would be relatively high, it would take around 16 years for the equipment (40 thousand reais) and installation (3,000 reais) to be fully paid for. According to the researcher, one of the reasons for the lack of economic viability of the installed project was the fact that the wind turbines were imported and had a high cost. National wind turbines were not used in the research due to lack of information on power curves provided by industries. According to Hussni, this would be an opportunity for the development of small national wind turbines optimized for low speed winds and installation on tops of buildings.

Brazil on the world stage
Brazil occupies a privileged position on the world stage in terms of wind power generation capacity. According to the Global Wind Energy Council (GWEC), the country is in eighth position in the ranking of the ten countries with the highest total installed capacity of wind energy. Even with all this potential, Leonardo Hussni recalls that academic research related to the integration of small turbines in consumer units is incipient in Brazil. The changes made to the legislation enacted by the National Electric Energy Agency (Aneel) on “Distributed Generation” led to further research on the subject being developed.


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