Elsevier

Journal of Energy Storage

Volume 23, June 2019, Pages 392-403
Journal of Energy Storage

Review
Advances in alkaline water electrolyzers: A review

https://doi.org/10.1016/j.est.2019.03.001Get rights and content

Highlights

  • A review of the literature regarding the hydrogen production has been performed.

  • A taxonomy proposal considering the H2 production through electrolysis is presented.

  • Different methods of electrolysis are described and compared.

  • Current lines of research to improve alkaline electrolysis technology are outlined.

Abstract

The renewed concern for the care of the environment has led to lower emissions of greenhouse gases without sacrificing modern comforts. Widespread proposal focuses on energy produced from renewable sources and its subsequent storage and transportation based on hydrogen. Currently, this gas applies to the chemical industry and its production is based on fossil fuels. The introduction of this energy vector requires the development of environmental-friendly methods for obtaining it. In this paper, existing techniques are just presented and the main focus is made on electrolysis, a mature procedure. In turn, some developed proposals as previous steps to the hydrogen economy are presented. Finally, some lines of research to improve alkaline electrolysis technology are commented.

Introduction

The world economy is constantly expanding. There are two influencing factors related to that expansion: the population growth and progress in personal comfort. Both factors affect the current fossil economy by increasing consumption and generating greater amount of greenhouse gases (GHG). The International Energy Agency (IEA) indicates a world consumption in 2015 of 9.383 Mtoe (1.1 × 105 TWh). This amount represents an increase of 18.23% and 99.64% over the past ten (2005) and fourty (1975) years, respectively. Besides, CO2 emissions in 2015 were 32.294 MTon, compared to 15.484 MTon in 1975 (109% increment) [1]. This situation is widely accepted as critical, hence worldwide environmental impact studies and environmental protection policies are generated. Moreover, the fact that fossil fuels are neither renewable nor evenly distributed across the globe leads to geopolitical conflicts and unequal situations.

Around the world, proposed solutions focus on the production of renewable energy. However, the share of renewable energies has not grown significantly (from 12.7% in 1975 to 13.5% in 2015). Besides costs issues, the global experience indicates that advances are needed to solve technical problems related to energy fluctuations produced in renewable sources. To achieve high integration of renewable energy, it is necessary to have the ability to accumulate the excess of energy to be consumed at a time when consumption exceeds production. Fig. 1 shows the variety of available technologies for energy storage. While some technologies such as supercapacitors or flywheels are used to store a reduced amount of power (up to 10MW) for a short time (up to an hour) and redeliver it quickly, for the case raised, it is necessary to use other technologies such as Compressed Air Energy Storage (CAES), Pumped Hydro Energy Storage (PHES) or hydrogen.

So far, the most common way to store large amounts of energy is PHES. The biggest disadvantage of this technology is related to its requirements on specific geographical features for installation and political conditions. It is here that among the methods of energy storage, hydrogen production currently takes relevance for its energy density, high energy capacity and transportability [2], [3].

Moreover, in the same direction, there is the concern about pollution in the transportation sector. Along with the development of electric vehicles, the hydrogen appears as an interesting energy vector. Both technologies, electric and H2-based vehicles, share the benefit of eliminating urban pollution and, depending on the original source, reducing or eliminating pollution in the whole process [4]. The union of these two sectors, electricity and transport, generates what is disclosed as hydrogen economy. The hydrogen economy is stated as an integral solution for the problem of producing, storing and supplying energy including all final uses while succeeding in GHG mitigation.

The industrial use of hydrogen dates from almost a century ago with a wide consumption in the chemical and oil industries (89% of consumption share) [5]. However, progress must be achieved in various issues in order to accomplish competitiveness of these technologies and develop this economic concept. Issues such as the efficiency and cost of production, storage and transport, are concepts that several companies, research centers and governments are developing.

Several reviews can be found that present the different technologies related to the use of hydrogen. Abdalla et al. [6] published a review of hydrogen technologies making a detailed explanation and comparison of current storage methods. Zhang et al. [7] present a brief and well-organized compendium of production, storage and electricity generation technologies. Dutta [8] summarizes development models for the hydrogen economy in various countries along with an explanation of hydrogen production, storage and utilization. Mazloomi and Gomes [9] discuss the economic aspects of centralized and distributed production. In addition, they present the risks inherent in the production, storage and distribution stages, proposing possible risk-reduction techniques.

At the same time, there are studies such as [10] that detail the steps to be followed in order to reach a mature hydrogen economy. Among those steps there are the Power-to-Gas [11], [12], the use of fossil hydrogen to power vehicles [13], [14], [15], [16] and the integration of electrolyzers with renewable energies in microgrids [17], [18]. All these developments bring hydrogen technologies taking into account the necessary economic issues in order for it to be sustainable over time. To do this, it will be necessary that companies, governments and research centers cooperate together in this direction [13].

This paper provides an overview of the hydrogen production technologies, specifically emphasizing production from alkaline electrolysis. Mueller-Langer et al. [19] in their techno-economic assessment assure that natural gas steam reforming, coal and biomass gasification and water electrolysis will play a significant role in the short and medium term. Besides, electrolysis occupies until today a dominant position as it is the only technology that can use directly the power surplus from renewable and fluctuating energies like wind mills or solar panels [7] so it has a concrete perspective on the use of this type of energy as the axis of the hydrogen economy. Among CO2-neutral H2 production, electrolysis highlight because it produces high purity hydrogen and it has an infrastructure already developed being a well-established technology [20], [21]. In the same direction, alkaline electrolysis is a mature and reliable technology which stands out from other types of electrolysis based on cost and simplicity [22].

The remainder of this paper is organized as follows. In Section 2, hydrogen production technologies are compared according to efficiency, costs and environmental consequences. After that, in Section 3, water electrolysis, as the most certain solution for ecofriendly hydrogen production, is described. Then, in Section 4, necessary developments in alkaline electrolyzers in the short and long term are displayed. Finally, conclusions in Section 6 reinforce the necessity to advance research to achieve the reduction of pollution through the hydrogen economy.

Fig. 2 shows the different methods of hydrogen production presented in Section 2. It highlights the approach outlined in this paper, explaining its organization.

Section snippets

Hydrogen production methods

There are several methods of hydrogen production with different stages of development. Currently, its production is mainly based on the reforming of fossil fuels (78%) and coal gasification (18%). From the pending 4% of alternate resources, the main technology is the electrolysis of water as a byproduct from chlor-alkali process [23], [24]. Despite the current use of hydrogen produced by the last process, this technology will not be considered in the analysis because in the long term and taking

Water electrolysis

Electrolysis is the method through which the water molecule is separated into hydrogen and oxygen by applying an electric current [42]. Although there are different methods, which are introduced below, they share the same global reactionH2O(l)H2(g)+12O2(g).

Developments in alkaline electrolysis

In recent decades, advances have been made in this type of electrolyzers called as advanced alkaline electrolyzers. The most important points of development are [21]:

  • Zero-gap configuration. It consists of minimizing the distance between electrodes to reduce the ohmic losses.

  • New materials for the diaphragm. Previously made of asbestos, the use of inorganic membranes is investigated. Some are based on antimony polyacid impregnated with polymers [78], on porous composite composed of a polysulfone

Discussions

As presented in the current review, there are interesting alternative methods for the production of hydrogen with virtually zero emissions, among them highlighting the production from biomass and electrolysis. Its biggest disadvantage is the economic cost superior to industrial processes such as the SMR in both construction and operation. It can be seen that these three technologies will coexist in the medium term, waiting for the proportion of SMR to gradually decrease, generating two

Conclusions

The search for alternative methods of power generation and transport has developed the concept of hydrogen economy. While today hydrogen is obtained mainly from hydrocarbons, new technologies to achieve lower GHG emissions are being developed and consolidated. This paper summarizes the different methods of hydrogen production with emphasis on the current status of alkaline electrolysis. Among hydrogen methods, electrolysis stands out for ease of connection to renewable energies, obtainable

References (131)

  • O. Schmidt et al.

    Future cost and performance of water electrolysis: An expert elicitation study

    Int. J. Hydrogen Energy

    (2017)
  • D.-Y. Lee et al.

    Life cycle greenhouse gas emissions of hydrogen fuel production from chlor-alkali processes in the United States

    Appl. Energy

    (2018)
  • J. Holladay et al.

    An overview of hydrogen production technologies

    Catal. Today

    (2009)
  • T. Paulmier et al.

    Use of non-thermal plasma for hydrocarbon reforming

    Chem. Eng. J.

    (2005)
  • K. Kovács et al.

    A novel approach for biohydrogen production

    Int. J Hydrogen Energy

    (2006)
  • P. Parthasarathy et al.

    Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield - a review

    Renew. Energy

    (2014)
  • S.E. Hosseini et al.

    Hydrogen production from renewable and sustainable energy resources: Promising green energy carrier for clean development

    Renew. Sustain. Energy Rev.

    (2016)
  • J. Levene et al.

    An analysis of hydrogen production from renewable electricity sources

    Solar energy

    (2007)
  • R. Bhandari et al.

    Life cycle assessment of hydrogen production via electrolysis - a review

    J. Cleaner Prod.

    (2014)
  • Y. Zhang et al.

    Microbial electrolysis cells turning to be versatile technology: Recent advances and future challenges

    Water Res.

    (2014)
  • M. Carmo et al.

    A comprehensive review on PEM water electrolysis

    Int. J. Hydrogen Energy

    (2013)
  • M. Laguna-Bercero

    Recent advances in high temperature electrolysis using solid oxide fuel cells: A review

    J. Power Sources

    (2012)
  • I. Vincent et al.

    Low cost hydrogen production by anion exchange membrane electrolysis: A review

    Renew. Sustain. Energy Rev.

    (2018)
  • L. An et al.

    Mathematical modeling of an anion-exchange membrane water electrolyzer for hydrogen production

    Int. J. Hydrogen Energy

    (2014)
  • X. Tang et al.

    Noble fabrication of Ni-Mo cathode for alkaline water electrolysis and alkaline polymer electrolyte water electrolysis

    Int. J. Hydrogen Energy

    (2014)
  • M. Faraj et al.

    New LDPE based anion-exchange membranes for alkaline solid polymeric electrolyte water electrolysis

    Int. J. Hydrogen Energy

    (2012)
  • H. Ito et al.

    Pressurized operation of anion exchange membrane water electrolysis

    Electrochim. Acta

    (2019)
  • B. Bauer et al.

    Anion-exchange with improved alkaline stability

    Desalination

    (1990)
  • A. Buttler et al.

    Current status of water electrolysis for energy storage, grid balancing and sector coupling via power-to-gas and power-to-liquids: A review

    Renew. Sustain. Energy Rev.

    (2018)
  • S. Grigoriev et al.

    High-pressure PEM water electrolysis and corresponding safety issues

    Int. J. Hydrogen Energy

    (2011)
  • S.Y. Gómez et al.

    Current developments in reversible solid oxide fuel cells

    Renew. Sustain. Energy Rev.

    (2016)
  • M. Felgenhauer et al.

    State-of-the-art of commercial electrolyzers and on-site hydrogen generation for logistic vehicles in South Carolina

    Int. J. Hydrogen Energy

    (2015)
  • M. Schalenbach et al.

    A perspective on low-temperature water electrolysis challenges in alkaline and acidic technology

    Int. J. Electrochem. Sci.

    (2018)
  • J. Divisek et al.

    Improved construction of an electrolytic cell for advanced alkaline water electrolysis

    Int. J. Hydrogen Energy

    (1985)
  • S. Meyer et al.

    Transition metal carbides (WC, Mo2C, TaC, NbC) as potential electrocatalysts for the hydrogen evolution reaction (HER) at medium temperatures

    Int. J. Hydrogen Energy

    (2015)
  • Q. Feng et al.

    A review of proton exchange membrane water electrolysis on degradation mechanisms and mitigation strategies

    J. Power Sources

    (2017)
  • S. Sun et al.

    Investigations on degradation of the long-term proton exchange membrane water electrolysis stack

    J. Power Sources

    (2014)
  • A. Kusoglu et al.

    Mechanical behavior of fuel cell membranes under humidity cycles and effect of swelling anisotropy on the fatigue stresses

    J. Power Sources

    (2007)
  • M. Chandesris et al.

    Membrane degradation in PEM water electrolyzer: Numerical modeling and experimental evidence of the influence of temperature and current density

    Int. J. Hydrogen Energy

    (2015)
  • C. Rakousky et al.

    An analysis of degradation phenomena in polymer electrolyte membrane water electrolysis

    J. Power Sources

    (2016)
  • H. Vandenborre et al.

    Alkaline inorganic-membrane-electrolyte (IME) water electrolysis

    Int. J. Hydrogen Energy

    (1980)
  • P. Vermeiren et al.

    Evaluation of the Zirfon separator for use in alkaline water electrolysis and Ni-H2 batteries

    Int. J. Hydrogen Energy

    (1998)
  • K. Onda et al.

    Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis

    J. Power Sources

    (2004)
  • C. Ziems et al.

    Project presentation: design and installation of advanced high pressure alkaline electrolyzer-prototypes

    Energy Procedia

    (2012)
  • A. Roy et al.

    Comparison of electrical energy efficiency of atmospheric and high-pressure electrolysers

    Int. J. Hydrogen Energy

    (2006)
  • F. Allebrod et al.

    Alkaline electrolysis cell at high temperature and pressure of 250oC and 42bar

    J. Power Sources

    (2013)
  • J. Ganley

    High temperature and pressure alkaline electrolysis

    Int. J. Hydrogen Energy

    (2009)
  • O. Ulleberg

    Modeling of advanced alkaline electrolyzers: a system simulation approach

    Int. J. Hydrogen Energy

    (2003)
  • H. Barthels et al.

    Phoebus-Jülich: an autonomous energy supply system comprising photovoltaics, electrolytic hydrogen, fuel cell

    Int. J. Hydrogen Energy

    (1998)
  • A. Ursúa et al.

    Static-dynamic modelling of the electrical behaviour of a commercial advanced alkaline water electrolyser

    Int. J. Hydrogen Energy

    (2012)
  • Cited by (388)

    View all citing articles on Scopus
    View full text