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Abstract: It is well-known that wireless sensor networks (WSNs) promise to revolutionise the way the authors can interact with the physical world. However, the deployment of these systems in practical environments is very limited because of power constraints. Systems based on solar, vibrational and thermal energy are the most used in WSN applications and only a few studies consider the wind for energy harvesting. Another important source of energy is the water flow. In the context of the WSN, it was found that there are practically no systems using such source. The purpose of this study is to evaluate the use of small-scale wind and hydro generators for energy harvesting to power wireless sensor nodes. For this purpose, the power coefficients and the output power of several horizontal-axis and Savonius wind turbines were determined. Systems based on Pelton and propeller turbines were constructed to evaluate the effect of some parameters in small-scale power generation.
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1 Introduction
The deployment of a network with hundreds or thousands of small and low-cost sensor nodes allows the monitoring of several physical world parameters. Currently, in practical situations the sensor nodes are powered by batteries or are connected to the power grid. The batteries may allow several days or months of operation, but hardly provide long-term operation. The changing of batteries for networks with many elements is not practical. A promising solution to overcome this limitation is to harvest energy from the environment [1, 2]. These harvesting systems should provide enough energy to power a sensor node that requires an average power consumption below a milliwatt up to several hundred milliwatts. These systems must also be compact.
In recent years, several approaches for energy harvesting from the environment to power wireless sensor networks (WSNs) have been considered. Much research has been applied to solar energy harvesting [3-7]. Assuming a typical solar panel with 15% of efficiency, the power available from photovoltaics is 15 mW/cm2 at midday outdoors [8]. Commercial solar panels usually provide 5-10 mW/cm2. Another popular source for energy harvesting is vibration, usually available in built environments. The schemes to generate electricity from vibration may include electromagnetic, electrostatic and piezoelectric conversion [8-10]. Energy harvesting from vibrations is commonly characterised by a small...