A centimetre-scale bi-directional wind turbine for energy harvesting applications: design and experimental tests

Abstract

In this work, new cm-scale wind turbines for powering sensor nodes devoted to monitoring/diagnostic of railway vehicles are designed, built and tested in a wind tunnel. Two rotors, having four airfoil blades with a diameter of 3 and 4 cm, are designed following the blade element momentum-based approach. The two rotors, tested in a wind tunnel, reach a power coefficient (without considering the losses in the conditioning circuit) ranging between 20% and 30%, in line with the maximum values of the Schmitz theory; the correspondence between the numerical estimates and the experimental data is discrete. The 4 cm diameter rotor, once connected to a conditioning circuit, reaches a maximum net efficiency of about 15%, equal to the maximum value found in the literature, but with a 13,5 cm diameter rotor. Considering the practical application on trains and the fact that the rotor has to work for two opposite velocity directions (it must be bi-directional), a 4 cm diameter symmetrical rotor with a constant blade pitch and flat plate blade section is also built. With the symmetric rotor, we can observe that the generated power is about 50% lower than that produced by the same rotor with airfoil blades. Finally, the turbine is set inside a duct to protect it and increase performance. The tests performed on this ducted turbine (4 cm diameter, symmetric) allow us to understand that the duct significantly increases the performance of the rotor in downwind conditions, from 1% to 6%, while it is almost irrelevant in upwind conditions. Moreover, the diffuser increases the efficiency by about 20%, while the contraction cone does not significantly modify the performance of the turbine.

Miniature water flow energy harvester based on savonius-type microturbine: an experimental study

“…Referring to table 1, the turbine implemented in this work has a diameter 2.56 times smaller than the ones in [2,4] and 5.1 times smaller than the ones in [1,3,19]. Moreover, it presents a cross-section of only 1.25 cm 2 to the flow and this is significantly smaller than the cross-section of any other device reported in literature to our knowledge.…”

“…Nowadays, energy harvesting (EH) plays an increasingly vital role in powering autonomous microsystems. Among other methods of harnessing energy, EH from fluid flow has emerged as a potential solution for powering wireless sensors in pipeline networks [1][2][3][4][5], eliminating the need for batteries or costly and impractical wired monitoring schemes. Especially in water infrastructure, these sensors contribute to water quality monitoring [6] and structural health monitoring [7] by tracking quantities like temperature, pressure, pH and the concentrations of a variety of chemicals [8].…”

“…The harvester had a rotor diameter of 2 cm, and a permanent magnet machine with an axial flux design was incorporated within the protective enclosure resulting in a 3.2 cm external diameter. More recently, a wind energy harvester with a 5 cm rotor diameter that could generate 40.7 mW at 15 m s −1 wind speed was presented by Fang et al [20], while Tomasini et al reported an airflow harvester with a 4 cmdiameter rotor for powering sensors used in railway vehicles [3]. The latter device can reach a remarkably high net efficiency of about 15% when connected to a PMC.…”

Principales túneles de viento en la investigación sobre energía eólica alrededor del mundo

“…Iowa State University 3 [19] City University of Hong Kong 3 [20] ABRI, National Cheng Kung University 3 [21] DAA, National Cheng Kung University 3 [22] North China Electric Power University 3 [23] Portland State University 2 [24] Ruhr-Universität Bochum 2 [25] Technion Flow Control Lab 2 [26] TU Delft 2 [27] Beijing University of Aeronautics & Astronautics 1 [28] China Aerodynamic Research and Development Center 1 [29] IET, Chinese Academy of Sciences 1 [30] Inter-University Research Centre on Building Aerodynamics and Wind Engineering 1 [31] Technical University of Denmark 1 [6] Huazhong University of Science and Technology 1 [32] Iowa State University, Icing Wind Tunnel 1 [33] WiST Lab, Iowa State University 1 [34] Von Karman Institute 1 [35] Department of Engineering Science, National Cheng Kung University 1 [36] Netherlands Organisation for Applied Scientific Research (TNO) 1 [37] Politecnico di Milano, "Sergio De Ponte" Wind Tunnel 1 [38] Kyushu University, Open Circuit Wind Tunnel 1 [39] TU Delft, Open Jet Facility 1 [40] University of Liege 1 [41] University of Oldemburg 1 [42] Vrije Universiteit Brussel 1 [35] Revisión de la investigación en los túneles principales Túnel de viento de sección abierta, Mie University…”

Portable Photovoltaic Power Generation System for Applications along the Railway and Its Improved Efficiency by Automatic Dust Removal by Foldable Solar Energy Collector

“…Moreover, wind energy is convenient to harvest along railways. For example, Tomasini et al [ 10 ] proposed a wind energy collector based on a centimeter‐scale bidirectional wind turbine. Experiments verified that placing the turbine inside a 4 cm diameter pipe provides protection while improving system performance by 1% to 6%.…”