Hydrogen Production and Delivery
Researchers at NREL are developing advanced processes to produce hydrogen economically from sustainable resources.
Biological Water Splitting
Certain photosynthetic microbes use light energy to produce hydrogen from water as part of their metabolic processes. Because oxygen is produced along with the hydrogen, photobiological hydrogen production technology must overcome the inherent oxygen sensitivity of hydrogen-evolving enzyme systems. NREL researchers are addressing this issue by screening for naturally occurring organisms that are more tolerant of oxygen and by creating new genetic forms of the organisms that can sustain hydrogen production in the presence of oxygen. Researchers are also developing a new system that uses a metabolic switch (sulfur deprivation) to cycle algal cells between the photosynthetic growth phase and the hydrogen production phase.
Contact: Maria Ghirardi
NREL scientists are developing pretreatment technologies to convert lignocellulosic biomass into sugar-rich feedstocks that can be directly fermented to produce hydrogen, ethanol, and high-value chemicals. Researchers are also working to identify a consortium of Clostridium that can directly ferment hemicellulose to hydrogen. Other research areas involve bio-prospecting efficient cellulolytic microbes, such as Clostridium thermocellum, that can ferment crystalline cellulose directly to hydrogen to lower feedstock costs. Once a model cellulolytic bacterium is identified, its potential for genetic manipulations, including sensitivity to antibiotics and ease of genetic transformation, will be determined. NREL's future fermentation projects will focus on developing strategies to generate mutants that are blocked selectively from producing waste acids and solvents to maximize hydrogen yield.
Contact: Pin-Ching Maness
Conversion of Biomass and Wastes
Hydrogen can be produced via pyrolysis or gasification of biomass resources such as agricultural residues like peanut shells; consumer wastes including plastics and waste grease; or biomass specifically grown for energy uses. Biomass pyrolysis produces a liquid product (bio-oil) that contains a wide spectrum of components that can be separated into valuable chemicals and fuels, including hydrogen. NREL researchers are currently focusing on hydrogen production by catalytic reforming of biomass pyrolysis products. Specific research areas include reforming of pyrolysis streams and development and testing of fluidizable catalysts.
Contact: Richard French
Photoelectrochemical Water Splitting
The cleanest way to produce hydrogen is by using sunlight to directly split water into hydrogen and oxygen. Multijunction cell technology developed by the photovoltaic industry is being used for photoelectrochemical (PEC) light harvesting systems that generate sufficient voltage to split water and are stable in a water/electrolyte environment. The NREL-developed PEC system produces hydrogen from sunlight without the expense and complication of electrolyzers, at a solar-to-hydrogen conversion efficiency of 12.4% lower heating value using captured light. Research is underway to identify more efficient, lower cost materials and systems that are durable and stable against corrosion in an aqueous environment.
Solar Thermal Water Splitting
NREL researchers use the High-Flux Solar Furnace reactor to concentrate solar energy and generate temperatures between 1,000 and 2,000 degrees Celsius. Ultra-high temperatures are required for thermochemical reaction cycles to produce hydrogen. Such high-temperature, high-flux, solar-driven thermochemical processes offer a novel approach for the environmentally benign production of hydrogen. Very high reaction rates at these elevated temperatures give rise to very fast reaction rates, which significantly enhance production rates and more than compensate for the intermittent nature of the solar resource.
Contact: Judy Netter
Renewable energy sources such as photovoltaics, wind, biomass, hydro, and geothermal can provide clean and sustainable electricity for our nation. However, renewable energy sources are naturally variable, requiring energy storage or a hybrid system to accommodate daily and seasonal changes. One solution is to produce hydrogen through the electrolysis—splitting with an electric current—of water and to use that hydrogen in a fuel cell to produce electricity during times of low power production or peak demand, or to use the hydrogen in fuel cell vehicles.
Researchers at NREL's Energy Systems Integration Facility and Hydrogen Infrastructure Testing and Research Facility are examining the issues related to using renewable energy sources for producing hydrogen via the electrolysis of water. NREL tests integrated electrolysis systems and investigates design options to lower capital costs and enhance performance.
Learn more about NREL's renewable electrolysis research.
Contact: Kevin Harrison
Hydrogen Dispenser Hose Reliability
With a focus on reducing costs and increasing reliability and safety, NREL performs accelerated testing and cycling of 700 bar hydrogen dispensing hoses at the Energy Systems Integration Facility using automated robotics to simulate field conditions. View the video of the robot, which mimics the repetitive stress of a person bending and twisting a hose to dispense hydrogen into a fuel cell vehicle's onboard storage tank. Researchers perform mechanical, thermal, and pressure stress tests on new and used hydrogen dispensing hoses. The hose material is analyzed to identify hydrogen infiltration, embrittlement, and crack initiation/propagation.
Contact: Kevin Harrison
Hydrogen Production and Delivery Pathway Analysis
NREL performs systems-level analyses on a variety of sustainable hydrogen production and delivery pathways. These efforts focus on determining status improvements resulting from technology advancements, cost as a function of production volume, and the potential for cost reductions. Results help identify barriers to the success of these pathways, primary cost drivers, and remaining R&D challenges. NREL-developed hydrogen analysis case studies provide transparent projections of current and future hydrogen production costs. Learn more about NREL's systems analysis work.
Contact: Genevieve Saur
HydroGEN Energy Materials Network
NREL serves as the lead laboratory for the HydroGEN Energy Materials Network (EMN) consortium.
Remarkable Stability of Unmodified GaAs Photocathodes during Hydrogen Evolution in Acidic Electrolyte, Journal of Materials Chemistry A (2016)
Solar to Hydrogen Efficiency: Shining Light on Photoelectrochemical Device Performance, Energy and Environmental Science (2016)
Reversible GaInP2 Surface Passivation by Water Adsorption: A Model System for Ambient-Dependent Photoluminescence, Journal of Physical Chemistry C (2016)
CO2-Fixing One-Carbon Metabolism in a Cellulose-Degrading Bacterium Clostridium thermocellum, Proceedings of the National Academy of Sciences (2016)
Phosphoketolase Pathway Contributes to Carbon Metabolism in Cyanobacteria, Nature Plants (2016)