Original Article Journal of Intelligent Material Systems and Structures 1–11 Ó The Author(s) 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1045389X17730917 journals.sagepub.com/home/jim Experimental sea wave energy extractor based on piezoelectric Ericsson cycles Bin Zhang 1 , Benjamin Ducharne 2 , Bhaawan Gupta 2 , Gael Sebald 2 , Daniel Guyomar 2 and Jun Gao 1 Abstract Recycling ambient energies with electric generators instead of employing batteries with limited lifespans has motivated a large scientist community over two decades. Sea waves exhibit a large energy density. The amount of energy that could be extracted from the sea waves is very high. This work describes a technique of sea wave energy extraction based on a piezoelectric conversion and an analogy with thermodynamic Ericsson loops. By synchronizing external electric field to the maximum and the minimum of the sea wave mechanical stress excitations, the piezoelectric material dielectric hys- teresis loop area is increased corresponding to the maximum of the energy available. In this article, technical solutions are proposed for the in site deployment of the proposed technique (maximum and minimum detection, external electric field source synchronization). Experimental measuring benches have been developed to monitor the sea wave mechanical excitation and to determine precisely the energy-harvesting potential. Adequate dielectric hysteresis model is proposed to numerically determine the best configuration (frequency, amplitude) of electric field to impose. Even if the Ericsson technique requires external electronic devices, the weak consumption of such components allows a large enhancement of the amount of energy extracted compared to a basic piezo element conversion. Keywords Energy harvesting, Ericsson cycle, piezoelectricity, hysteresis, fractional derivative Introduction Ocean movements (waves, marine currents) are an enormous, largely unexploited energy resource; the potential related to this energy extraction is significant. Main researches around this theme are driven by the increasing necessities of finding new sources of renew- able energy. This scientific investigation field is rela- tively undeveloped versus the other well-known renewable energy technologies such as solar or wind. Even if first patterns around this subject have been published during the 18th century (Ross, 1995), the first oil crisis in 1970s has constituted the first real sti- mulator for the sea wave energy extraction (e.g. Salter (1974)). The current special attention set on climate change and the rising level of CO 2 contribute in making the electricity generation from renewable sources an important field of scientific investigation again (Li et al., 2016; Xiang et al., 2015). Worldwide waves are estimated in terms of power resources equal to 2 TW (Thorpe, 1999). It is assumed that almost 15% of the world electricity necessities of today could be provided by sea wave energy. By combining it to marine currents generation, almost 20% of this demand could be ful- filled (Callaghan and Boud, 2006; Duckers, 2004). Lot of reviews on wave energy extractors have already been published (Drew et al., 2009; Previsic et al., 2004). All these articles give an exhaustive inven- tory of the many wave energy devices already existing. Many of them are still under R&D stage, and just a few have been verified at large scale and displayed in the oceans. The LIMPET (Land Installed Marine Power Energy Transmitter) project and Pelamis machine are both two large-scale sea wave energy extractors installed in 2001 and 2008 (McConnell et al., 2004). The first one is a 500-kW shoreline wave power plant 1 School of Mechanical, Electrical & Information Engineering, Shandong University, Weihai, China 2 Laboratoire de Ge ´nie Electrique et Ferroe ´lectricite ´ (LGEF), INSA de Lyon, Villeurbanne cedex, France Corresponding author: Benjamin Ducharne, Laboratoire de Ge ´nie Electrique et Ferroe ´lectricite ´ (LGEF), INSA de Lyon, Ba ˆtiment Gustave Ferrie ´– 8 rue de la Physique, 69621 Villeurbanne cedex, France. Email: Benjamin.ducharne@insa-lyon.fr