Large Active Area PEM Electrolysis Stack Test Bed - Design, Data and Development
Authors: Harrison Kevin , Smith Owen , Peters Michael , Terlip Danny 
Published: February 2020

In a growing number of regions around the world, solar and wind generated electricity is a large percentage of the overall supply. In times of low demand and high renewable electricity production energy storage can be deployed to shift the environmentally preferred energy to times of the day/week/month when it is needed most. Additionally, energy storage enables even higher penetrations of naturally varying renewable electricity sources to provide the increasing demand of the planet.
Historically, polymer electrolyte membrane (PEM) electrolysis systems have been limited to small active areas, current density in the range of 1500 mA/cm2 and stack power levels in the 10's of kilowatts. Today, PEM stack active area and current density are both increasing to enable smaller footprints than their alkaline counterparts. Both of these changes are helping to decrease the cost of PEM electrolyzer systems.
The National Renewable Energy Laboratory (NREL) has shown that both PEM and alkaline electrolyzer systems can ramp power up and down very quickly to accommodate the needs of grids with high penetration of renewable electricity installed. In addition, their ability to ramp quickly enables these electrolyzer systems to participate in grid ancillary services aimed at assuring a safe and reliability electrical grid. The 99.99+% purity levels of the hydrogen product from these electrolyzer systems can be used in a number of industries including; fuel cell electric vehicle refueling, stored for use in stationary fuel cell applications, material handling refueling (e.g., forklifts) and can be reacted with carbon dioxide to produce renewable hydrocarbon chains (e.g., methane), which can then take advantage of existing infrastructure.
In a project with DOE, NREL has designed, built and now operates a large active area stack test bed (STB) to support water electrolyzer industry partners. The STB provides a flexible and open platform to allow the quick exchange and testing of stacks, sub-systems and components. The goal of the modular system design is to provide industry a place to develop and validate hardware, process software and sub-system control algorithms to improve electrolyzer system efficiency, response, safety and capital costs.
The electrolyzer stack test bed was commissioned at NREL's Energy Systems Integration Facility (Golden, CO) in third quarter 2014 and then immediately provided factory acceptance testing of three 150 kW PEM electrolyzer stacks built by Giner, Inc. in November. The STB is providing a testing platform for a novel hydrogen drying technique, developed at NREL, to reduce the amount of hydrogen product wasted when the stack is being powered with variable power. In 2015 and 2016, research, development and demonstration work conducted with the STB will focus on improving system efficiency by optimizing balance of plant power requirements, power conversion optimization, grid integration and providing gas for hydrogen infrastructure component validation and 700 bar refueling demand.