Energy Conversion and Management 194 (2019) 55–74

Contents lists available at ScienceDirect

Energy Conversion and Management

journal homepage: www.elsevier.com/locate/enconman

Performance study of a Helical Savonius hydrokinetic turbine with a new T

deflector system design
⁎
Mabrouk Mosbahia,b, , Ahmed Ayadia, Youssef Chouaibic, Zied Drissa, Tullio Tucciarellid
a
University of Sfax, Laboratory of Electro-Mechanic Systems (LASEM), National School of Engineers of Sfax (ENIS), B.P. 1173, km 3.5 Soukra, 3038 Sfax, Tunisia
b
University of Tunis, Higher National Engineering School of Tunis (ENSIT), Avenue Taha Hussein Montfleury, 1008 Tunis, Tunisia
c
Higher Institute for Technological Studies of Sidi Bouzid, Tunisia
d
University of Palermo, Department of Civil, Environmental, Aerospace and Materials Engineering (DICAM), Viale delle Scienze, 90128 Palermo, Italy

A R T I C LE I N FO A B S T R A C T

Keywords: The use of renewable energy sources has becoming a necessity to generate electricity. Helical Savonius rotors
Helical Savonius rotor have been preferred for small-scale hydropower generation. Numerous studies were carried out to improve the
Deflector system performance of the Helical Savonius rotor which has not been fully explored. In this paper, an experimental
Rotor performance study was carried out to evaluate the performance of a Helical Savonius water rotor in an irrigation channel. In
Power coefficient
order to enhance the performance of the studied water rotor, a new deflector system design was proposed.
Torque coefficient
Validation
Different configurations of the proposed deflector system were tested numerically using the commercial software
ANSYS FLUENT 17.0. Without a deflector system, the maximum power coefficient is found to be equal to 0.125
at tip-speed ratio of 0.7. Using the optimal configuration of the new deflector system, the maximum power
coefficient reaches 0.14. The utilization of this new design system is predicted to contribute towards a more
efficient use of flows in rivers and channels for electricity production in rural areas.

1. Introduction For enhancement, the numerical and experimental forecasts of the Sa-
vonius rotors performance are important to be debated.
Nowadays, energy is the most important need of human. It is es- Recently, many researchers have presented various techniques to
sential in every activity of daily life including access to basic neces- improve the Savonius rotor performance using numerical and experi-
sities, health and education [1]. Many methods are available to produce mental approaches such as the optimization of the geometrical para-
energy for humanity on the Earth. Fossil fuels are the most used energy meters of the rotor. The aspect ratio, the overlap ratio, the blades
sources since they are characterized by an easy exploit and an effective profile and the blades number are the main factors that have a direct
cost [2]. However, the burning of these fuels increases the concentra- effect on the efficiency of the Savonius rotor. For example, Mabrouki
tion of greenhouse gases such as carbon dioxide in the atmosphere et al. [10] developed an experimental study of a water Savonius rotor
[3–4]. Indeed, the reserves of fossil fuels are started to decrease. To with two buckets. The experimental study was conducted in a hydraulic
reduce greenhouse gas emissions and to provide sustainable energy test bench. Different overlap ratios were studied which ranging from 0
services, renewable energy sources are increasingly recommended and to 0.3. As a result, the authors noted that the overlap ratio has an im-
used to produce green power [5–6]. Among all renewable energies, pact on the rotor performance. In fact, they confirmed that the max-
small-scale hydropower is a renewable source to create electricity from imum value of the power coefficient was obtained with an overlap ratio
rivers using rotors which are fixed on the river side [7–8]. These rotors value equal to 0.3. Patel et al. [11] carried out an experimental study to
create electricity using the kinetic energy of natural water resources analyze the effect of the aspect ratio, the overlap ratio and the end plate
instead of potential energy. This is why the turbines are called “zero- on the performance of a Savonius hydrokinetic rotor. In their work,
head” or “in-stream”. Savonius water rotor has superiorities in com- they tested different overlap ratios ranging from 0 to 0.174. For each
parison to other water rotors such as simple design, self-starting ability overlap ratio, they investigated different values of aspect ratio. As re-
and low cost [9]. However, this rotor suffers low hydrodynamic per- sults, they concluded that the performance of the Savonius rotor can be
formance which is an interesting topic to be investigated and enhanced. improved by the use of closed ended vanes. In addition, they noted that

⁎
Corresponding author at: University of Sfax, Laboratory of Electro-Mechanic Systems (LASEM), National School of Engineers of Sfax (ENIS), B.P. 1173, km 3.5
Soukra, 3038 Sfax, Tunisia.
E-mail address: mabrouk.mosbahi@gmail.com (M. Mosbahi).

https://doi.org/10.1016/j.enconman.2019.04.080
Received 18 February 2019; Received in revised form 15 April 2019; Accepted 26 April 2019
0196-8904/ © 2019 Elsevier Ltd. All rights reserved.