Impact of the current ﬂuctuation on the efﬁciency of Alkaline Water Electrolysis Zsolt Dob  o * ,  Arp  ad Bence Palot  as University of Miskolc, Institute of Energy and Quality Affairs, 3515, Miskolc, Hungary article info Article history: Received 18 September 2016 Received in revised form 7 November 2016 Accepted 20 November 2016 Available online xxx Keywords: Hydrogen production Water electrolysis Current ﬂuctuation abstract The relationship between the electric current ﬂuctuation and the efﬁciency of Alkaline Water Electrolysis (AWE) was analyzed and the results are presented in this paper. Square, triangle, sine and sawtooth current waveforms with various frequency and amplitude settings were applied to a lab scale electrolyser with current densities up to 5000 A/m 2 .A novel, fully automatic measurement and data acquisition system was designed in order to generate thousands of experiments in a short period of time. The results show that non- steady DC current applied to the cell cause efﬁciency loss compared to the steady DC condition at same current density. Furthermore, the efﬁciency loss can be inﬂuenced by 3 parameters of the ﬂuctuating electric current: ripple factor, frequency and mean current density. The detailed results give new insight for the investigation of water electrolysis efﬁciency. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Water electrolysis is one of the simplest methods for hydrogen production [1], but due to cost efﬁciency reasons hydrogen is currently produced mostly from fossil sources [2]. On the other hand, water electrolysis combined with renew- able energy sources can be sustainable, environment-friendly and long-term solution in energy production and consump- tion [3]. One direction of research and development in water electrolysis focuses on increasing the efﬁciency of the tech- nology and decreasing the investment costs at the same time. Several studies are available on the design of an appropriate water electrolysis system [1,4e8], and many of them focuses on a speciﬁc part of the topic, for example the impact of temperature and pressure [9e12], the development of sepa- rator materials [13e16], the development of electrode mate- rials and catalysts [17e23], or the bubbling properties in the electrolyser [24e26]. In these cases, the power supply used to perform the electrochemical reactions is regarded as a source of constant direct current. Several investigations were per- formed using voltage pulses or different voltage waveforms as well [27e35], but the literature reveals, that ﬂuctuations in the current has been studied only intermittently [36e38]. Electroplating is one ﬁeld in electrochemistry, where the difference between the steady DC and pulsed DC is clearly visible. Some electroplating systems need steady DC power input [39e42], and any deviation from DC may cause waste products. Voltage ripple changes the structure of the electro- deposited material, and there are a number of studies about the ripple sensitivity of electroplating [43,44]. On the other hand, there are materials, when pulse current can result in better electrodeposition [45,46]. The “quality” of the used electricity is important for water electrolysis as well. A voltage or current waveform can be easily applied to the electrolyser by using inadequate power supply, while the caused overall * Corresponding author. Present address: University of Utah, Institute for Clean and Secure Energy, 84112, Salt Lake City, UT, USA. E-mail address: zsoltdobo@gmail.com (Z. Dob o). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2016) 1 e8 http://dx.doi.org/10.1016/j.ijhydene.2016.11.142 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Dob o Z, Palot as  AB, Impact of the current ﬂuctuation on the efﬁciency of Alkaline Water Electrolysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.11.142