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- A more efficient technique to power home monitoring systems using controlled battery chargingPublication . Azevedo, Joaquim Amândio; Santos, Filipe EdgarHome energy monitoring has recently become a very important issue and a means to reduce energy consumption in the residential sector. Sensors and control systems are deployed at various locations in a house and an intelligent system is used to efficiently manage the consumed energy. Low power communication systems are used to provide low power consumption from a smart meter. Several of these systems are battery operated. Other systems use AC/DC adapters to supply power to sensors and communication systems. However, even using low-power technology, such as ZigBee, the power consumption of a router can be high because it must always be powered on. In this work, to evaluate power consumption, a system for monitoring energy usage and indoor air quality was developed. A technique is proposed to efficiently supply power to the components of the system. All sensor nodes are battery operated, and relays are used to control the battery charging process. In addition, an energy harvesting system based on solar energy was developed to power the proposed system.
- Energy harvesting from hydroelectric systems for remote sensorsPublication . Azevedo, Joaquim Amândio Rodrigues; Lopes, JorgeHydroelectric systems are well-known for large scale power generation. However, there are virtually no studies on energy harvesting with these systems to produce tens or hundreds of milliwatts. The goal of this work was to study which design parameters from large-scale systems can be applied to small-scale systems. Two types of hydro turbines were evaluated. The first one was a Pelton turbine which is suitable for high heads and low flow rates. The second one was a propeller turbine used for low heads and high flow rates. Several turbine geometries and nozzle diameters were tested for the Pelton system. For the propeller, a three-bladed turbine was tested for different heads and draft tubes. The mechanical power provided by these turbines was measured to evaluate the range of efficiencies of these systems. A small three-phase generator was developed for coupling with the turbines in order to evaluate the generated electric power. Selected turbines were used to test battery charging with hydroelectric systems and a comparison between several efficiencies of the systems was made. Keywords
- Energy harvesting from wind and water for autonomous wireless sensor nodesPublication . Azevedo, J.A.R.; Santos, F. E. S.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.
- Small scale wind energy harvesting with maximum power trackingPublication . Azevedo, Joaquim; Mendonça, FábioIt is well-known that energy harvesting from wind can be used to power remote monitoring systems. There are several studies that use wind energy in small-scale systems, mainly with wind turbine vertical axis. However, there are very few studies with actual implementations of small wind turbines. This paper compares the performance of horizontal and vertical axis wind turbines for energy harvesting on wireless sensor network applications. The problem with the use of wind energy is that most of the time the wind speed is very low, especially at urban areas. Therefore, this work includes a study on the wind speed distribution in an urban environment and proposes a controller to maximize the energy transfer to the storage systems. The generated power is evaluated by simulation and experimentally for different load and wind conditions. The results demonstrate the increase in efficiency of wind generators that use maximum power transfer tracking, even at low wind speeds.