This article is taken from the June 2013 issue of the Fuel Cells Bulletin newsletter – check out the sample Digital Edition.
HySA Infrastructure research projects
The mission of the HySA Infrastructure Centre of Competence is to deliver novel technologies for hydrogen production, storage, and distribution infrastructure. It has a variety of projects under way or planned to meet its cost targets.
Solar-to-hydrogen pilot plant, training facilities
The centre has a Proton OnSite HOGEN-series PEM electrolyser that is being integrated into a 6 kW solar-to-hydrogen pilot plant. The first of its kind in South Africa, the pilot plant includes solar photovoltaic (PV) panels, power electronics, two 15 kWh lead-acid battery banks with charge controllers, and hydrogen storage.
The centre also has a state-of-the-art 400 W solar-to-hydrogen system from German-based Heliocentris. Engineer Charlie Phutha explains that energy from the PV panels will be used to generate hydrogen, with the surplus energy being stored in the battery banks for use during shortfalls.
These installations will be used for training and education purposes in a variety of hydrogen-related technologies, including fuel cells, energy storage, energy management, and combination with batteries.
Future projects will expand the solar PV capacity to 12 kW, and incorporate electrochemical hydrogen compression (EHC) to increase the output pressure to 150 bar. The researchers will also establish the full economical hydrogen cycle, from the production of hydrogen to use by the end-user, and organise renewable hydrogen training seminars.
Renewable hydrogen production
HySA Infrastructure aims to develop a low-cost, locally manufactured hydrogen production system that will be robust and suitable for distributed small-scale applications, like clusters of homes in rural areas, hospitals, or localised fuelling stations.
To this end, the DST has tasked the centre to develop a complete PEM electrolyser system and proprietary short stack. The electrolyser development will target high current density performance (>2 A/cm2, cell voltage <1.8 V) at 80°C with <0.1 mg/cm2 total PGM loading.
The electrolyser design/system will be capable of operating at high pressure (up to 700 bar), with mitigation strategies developed to improve durability. The work will also develop the capability to test and benchmark hardware, with the development of specialised diagnostic tools and methods.
Characterisation tools development for PEM electrolysers
HySA Infrastructure is developing characterisation tools to improve the fundamental understanding of PEM electrolysers. Research scientist Jan van der Merwe says that the characterisation tools will provide a platform to develop and optimise PEM electrolysers and integration of components such as the MEA, gas diffusion electrode (GDE), membranes etc.
The techniques being used include current interrupt (CI), a quick method used in diagnostics to determine membrane resistance. Another tool is electrochemical impedance spectroscopy (EIS), to measure ohmic losses, activation losses, and mass transfer losses. And current mapping (CM) is used to determine the local current density distribution, measuring temperature, water management, flow-field patterns, startup/shutdown effects, and operating pressure.
Electrochemical hydrogen compression (EHC)
A promising possibility for PGM utilisation is as electrocatalysts to electrochemically compress hydrogen, which would reduce hydrogen storage costs. The same principle can also be used for separation of gas mixtures containing hydrogen. The advantages of electrochemical hydrogen compression are solid-state operation (no moving parts), low noise, relatively high efficiency, and its suitability for small-scale applications.
Future work will focus on extending operation to a discharge pressure of 150 bar, developing a high-pressure filling station coupled to the solar-to-hydrogen plant, characterisation of the electrochemical hydrogen compressor, and degradation studies.
Hydrogen storage materials
The work on hydrogen storage materials is being conducted at the CSIR facility in Pretoria, where a state-of-the-art hydrogen storage laboratory is being established. The team is led by Dr Henrietta Langmi, Manager of Key Programme 4, with senior researcher Dr Jianwei Ren.
The lab will enable the synthesis, characterisation, and performance testing of candidate hydrogen storage materials. Initially, materials of interest include carbon and other nanostructures, and metal organic frameworks (MOFs) for physical adsorption (physisorption).
A key focus, in line with the HySA goals, is to develop storage materials that utilise the unique properties of PGMs to enhance storage capacity and reduce charge and discharge times.
One promising alternative method for hydrogen storage is physisorption of molecular hydrogen on the large surface of porous nanostructures, which may lead to storage systems that operate at moderate temperature and pressure, and provide high charge/discharge rates. To this end, HySA Infrastructure is synthesising and characterising metal organic frameworks, with the aim of enhancing the binding energy of hydrogen to the material and achieving high hydrogen storage capacities without compromising other desirable properties.
The group is also investigating tailored, PGM functionalised carbon nanostructures for hydrogen storage, with templated carbon materials being examined. This project is executed based on the ‘hub-and-spoke’ model in collaboration with the University of Stellenbosch.
The HySA Infrastructure team is also investigating the use of chemical carriers, i.e. the concept of transporting hydrogen as an easily decomposed chemical. Research is focused on the delivery of liquid carriers such as ammonia (see below) and formic acid (HCOOH) to the end-user site, with decomposition to generate hydrogen on demand, possibly with compression and buffer storage of the hydrogen.
Ammonia to hydrogen
The thermocatalytic decomposition of ammonia (NH3) has been identified as an attractive way to produce CO-free hydrogen for PEM fuel cell applications. However, the main challenge has been to develop a low-cost, high-activity catalyst for incorporation into a compact reformer that can decompose NH3 at a rate that satisfies hydrogen flow requirements and other system performance criteria at low temperatures.
Mixed oxides have emerged as a new class of support materials that can be used to reduce the support acidity. The HySA Infrastructure project addresses the incorporation of a selected oxide support onto the matrix of a PGM-containing catalyst, as well as the reactor design choice (e.g. a microchannel reactor).
PhD candidate Steven Chiuta is developing a microchannel ammonia fuel processor to generate onsite hydrogen via ammonia decomposition. This project at NWU aims to address the present lack of an adequate infrastructure for generating and delivering hydrogen to drive PEM fuel cells at off-grid telecom base stations, which are currently powered by diesel generators.
Hydrogen production using SO2 electrolysis
The hybrid sulfur process can be used to produce low-cost hydrogen, via electrolysis using a proton-exchange membrane (PEM) to electrochemically react water and SO2 gas to produce hydrogen and sulfuric acid. NWU research scientist Andries Kruger explains that HySA Infrastructure is involved in benchmarking electrolyser components such as the MEA, membranes, electrocatalysts etc. from collaboration partners (such as the University of South Carolina in the US) and various other suppliers.
A collaboration with the University of Stuttgart in Germany includes synthesis of state-of-the-art PEMs and MEAs, while work with the Kurchatov Institute in Russia includes performance comparison of the electrolysers.
Current projects include the commissioning of a fully automated and dedicated SO2 system for the evaluation of impurities such as H2S gas on the performance of the electrolyser with respect to catalyst degradation and long-term operation effects. Removal of emission gases such as SO2 from the atmosphere can also be achieved using SO2 electrolysis.
The South African hydrogen strategy is focused primarily on maximising PGM beneficiation, while at the same time fulfilling other important objectives such as environmental and developmental imperatives. The Department of Science & Technology’s strategy and established structures are executed through its HySA programme.
Three HySA Centres of Competence – HySA Catalysis, HySA Systems Integration & Technology Validation, and HySA Infrastructure – have been established , with core staff now in place, and Directors with recognised experience have been appointed. After the initial establishment of these structures and the approval of business plans, the centres are accelerating and scaling up their activities.
The next steps will include an opportunity to form public-private partnerships with industry, and collaborative research and development activities with local and international partners.
This article was written with significant assistance from Dr Dmitri Bessarabov, Director of HySA Infrastructure, and his colleagues while on a visit to Potchefstroom for the official opening of the HySA Infrastructure facilities at the end of May.
The sources for this article include Dr Bessarabov’s presentation at the 19th World Hydrogen Energy Conference in June 2012 in Toronto, as well as HySA Infrastructure documents and other presentations.