Hydrogen Production, Compression, Storage, and Utilization: Systems Integration and Infrastructure
LaboratoryNational Renewable Energy Laboratory (NREL)
Capability ExpertKevin Harrison, Mike Peters, Danny Terlip
Node Readiness Category1: Low-Temperature Electrolysis (LTE)
The end-use of renewably produced hydrogen varies based on application but the end-use needs to be considered when designing and interfacing hydrogen production, compression and storage systems. Renewable hydrogen, powered by inherently variable sustainable sources (e.g., wind and solar), would result in variable hydrogen output flow that could cause downstream system issues without proper system engineering. Typical end-uses for hydrogen include: transportation, material handling equipment (forklifts), ammonia production, methanation, or direct injecting into the natural gas pipeline. Each of those end-uses comes with its own pressure and flow requirements that need to be addressed. For example, a light-duty hydrogen fueling station needs to have hydrogen pressurized up to 875 bar. Typical systems take hydrogen input at a low pressure (7 – 20 bar) and compress in two stages (7 bar - 400 bar - 875 bar) to reach their target pressure for either fueling material handling equipment (400 bar) or light-duty fuel cell electric vehicles (875 bar). Hydrogen storage and mechanical compressors need to be sized with the variable flow from a renewably-powered hydrogen generator in mind. A functionality and cost analysis can create opportunities for system optimization.
NREL can provide hydrogen system integration testing at their Hydrogen Infrastructure Testing and Research Facility, located within ESIF. NREL's electrolyzer stack test bed is capable of testing PEM electrolyzer stacks up to 4,000 A DC, 250 V DC, and 30 bar. NREL's stack test bed is capable of simulating variable (i.e., renewable) profiles that connect directly with hydrogen station hardware. The hydrogen station includes multiple types of mechanical compressors and storage tanks that can be used to simulate material handling or light-duty vehicle end-uses of hydrogen. Also, NREL has an active project with Southern California Gas Company that is demonstrating operating a bio-methanation system with variable hydrogen input (simulated PV) to produce methane (with hydrogen as in intermediate step).
Through proper flow control and system modeling NREL is able to simulate any of the mentioned end-uses of hydrogen. Stack DC power levels can be provided up to 1 MW, with ancillary AC loads (e.g., pumps) provided separately. Current hydrogen production rate is 2 kg per hour from low-temperature electrolysis. Production capacity will be upgraded in 2016 to 5 kg per hour with the installation of a 250 kW PEM electrolyzer stack. Medium pressure (20 to 400 bar) compressor flow rates are limited today to about 3 kg per hour and high pressure (400 to 875 bar) about 18 kg per hour. Existing hydrogen storage quantities support research at the following capacities and pressures; 100 kg at 20 bar, 80 kg at 400 bar and 60 kg at 875 bar (for a total of 240 kg stored on-site).
Co-funded between the DOE Fuel Cell Technologies Office and NREL, the modular electrolyzer stack test bed (with full variable power control) coupled with hydrogen compression, storage and refueling station and (future) bio-methanation project make it unlike any system in the world. Furthermore, NREL's hydrogen production, infrastructure and bio-methanation projects allow for real-life hydrogen utilization to be analyzed using experimental data and established techno-economic analysis methods. Hardware-in-the-loop enables both internal and external users to generate and validate models using actual feedback data from hardware generated in real-time. External users can control NREL's electrolysis system using a novel real-time dynamic simulator (RTDS) that has been validated with Idaho National Lab.
Grid integration testing is not feasible either with the existing utility or in a hardware test bed. Power hardware-in-the-loop (PHIL) allows for high fidelity testing by simulating the unfeasible components (utility grid) with a model while simultaneously operating hardware (electrolyzer) that feeds data to the model. NREL has demonstrated this capability in a joint project with Idaho National Lab (INL) where a remote grid model running at INL controlled the 120kW PEM electrolyzer at NREL based on grid conditions. This PHIL test bed could be connected to any remote grid simulator.
Advanced grid services, power converters and controllers that would allow electrolyzers to reduce power consumption and participate in grid services must be validated prior to significant deployment. The test bed at NREL allows for modeling these systems and controllers in a simulated environment first and then testing with actual electrolyzer hardware and grid models. These models can then be integrated with varying levels of renewable and conventional energy generation to determine the system's response to varying grid conditions. Additional testing capabilities are available by linking multiple labs within the building on a common AC and DC buss network. Experiments can be run in separate labs depending on the need, yet still be connected to each other.
The equipment is being partly utilized for multiple DOE-sponsored, CRADA- and TSA-funded research projects. However, there exists floor space and equipment availability for new projects. We are currently collaborating with industry (electrolysis companies, power companies, car companies), and other national labs on hydrogen-related projects. The capability is located in ESIF user facility and hence it facilitates external users.
Hydrogen production, compression and storage systems at the ESIF were intentionally designed to be flexible open platforms to accommodate complex research activities. The integrated systems provide researchers the ability to configure, test and innovate to optimize electrical, thermal and fuel systems in ways never available before.
NREL's Hydrogen Infrastructure Testing and Research Facility
NREL's Electrolyzer Stack Test Bed