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Next Generation PEM Electrolyser under New Extremes

Periodic Reporting for period 2 - NEPTUNE (Next Generation PEM Electrolyser under New Extremes)

Reporting period: 2019-08-01 to 2021-01-31

Water electrolysis supplied by renewable energy is the foremost technology for producing “green” hydrogen for fuel cell vehicles. The ability to follow rapidly an intermittent load makes this an ideal solution for grid balancing. To achieve large-scale application of PEM electrolysers, a significant reduction of capital costs is required together with a large increase of production rate and output pressure of hydrogen, while assuring high efficiency and safe operation. To address these challenges, a step-change in PEM electrolysis technology is necessary. The NEPTUNE project develops a set of breakthrough solutions at materials, stack and system levels to increase hydrogen pressure to 100 bar and current density to 4 A⋅cm-2 for the base load, while keeping the nominal energy consumption <50 kWh/kg H2. The rise in stack temperature at high current density will be managed by using Aquivion® polymers for both membrane and ion exchange resin. Aquivion® is characterised by enhanced conductivity, high glass transition temperature and increased crystallinity. Dramatic improvements in the stack efficiency will be realised using novel thin reinforced membranes, able to withstand high differential pressures. An efficient recombination catalyst will solve any gas crossover safety issues. Newly developed electro-catalysts with increased surface area will promote high reaction rates. The novel solutions will be validated by demonstrating a robust and rapid-response electrolyser of 48 kW nominal capacity with a production rate of 23 kg H2/day. The aim is to bring the new technology to TRL5 and prove the potential to surpass the 2023 KPIs of the MAWP 2017. The proposed solutions contribute significantly to reducing the electrolyser CAPEX and OPEX costs. The project will deliver a techno-economic analysis and an exploitation plan to bring the innovations to market. The consortium comprises an electrolyser manufacturer, suppliers of membranes, catalysts and MEAs and an end-user.
The project is now at the end of the third year. Work Package 2 has produced a deliverable detailing characterisation and established testing protocols that will be followed in the rest of the work packages. These protocols were used in testing the catalysts and membranes in WP3 and WP4 where there have been some encouraging results, and although not all milestone targets have been achieved, there has been significant progress across all technical work packages. Optimised MEAs have been produced and tested, along with the up-scaling of membrane and catalyst production. A test stack and improved balance of plant has been produced and is ready to test the optimised MEAs produced to the high temperatures and operating pressures specified in the NEPTUNE project aims.

Solvay and CNR have produced journal papers and presented the project at external events, and when there are more results, it is expected that other partners will be able to present these and share the achievements of the project as they are realised.
The project plans to improve electrolysis stack performance with stack operation at a current density >4 A⋅cm-2 (base load) with an average cell potential <1.75 V (85% voltage efficiency), and peak load of 8 A⋅cm-2 (at least 1 h) during duty cycles with Ecell <2.2 V
The operating temperature is planned to be 90 degrees for base-load operation and up to 140 degrees for peak load operation of at least one hour under pressurised conditions.
The hydrogen output pressure will be 100bar for current densities ranging between 0.2 and 4-8 A⋅cm-2
The prototype will be validated with 398 cm-2 active area cells achieving TRL5.
The gas crossover targets are extremely ambitious with the planned maximum hydrogen content in the oxygen stream being under 0.5% across the entire load curve and the loss of faradic efficiency being under 1% with hydrogen purity over 5N.
The electrolyser efficiency will be over 80% against HHV of hydrogen at 4 A⋅cm-2 current density with energy consumption lower than 50 kWh/kg H2.
The prototype will be tested for at least 4,000 hours (cumulative) with targeted degradation rate lower than 5 µV/h at a current density of 4 A⋅cm-2 and less than 10 µV/h at higher current densities (6-8 A⋅cm-2)
Cost reduction is a key part of Neptune and material use will focus on minimisation by use of thin cost-effective short-side chain membranes, low precious metal catalysis and low cost coated titanium cell components and flow-field free bipolar plates designed for cost-effective stack hardware.
The CAPEX is planned to be <1.5 M€/ (t/d H2) achieved by quadrupling operating current density, system simplification and materials use minimisation.
The stack will also be capable of rapid start up (warm <1 s) and (cold <10 s) and partial load behaviour (load range 5%-200% corresponding to 0.2 A⋅cm-2 and 8 A⋅cm-2 operating current densities)
Project Logo
Membrane photo
Test stack photo
Catalyst pictures