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Almost all of the hydrogen produced in the U.S. today is by steam reforming of natural gas and for the near term, this method of production will continue to dominate. Researchers at NREL are developing a wide range of advanced processes for producing hydrogen economically from sustainable resources. These R&D efforts fall into five major categories:
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Biological Water Splitting
Certain photosynthetic microbes produce hydrogen from water in their metabolic activities using light energy. Photobiological technology holds great promise, but because oxygen is produced along with the hydrogen, the technology must overcome the limitation of oxygen sensitivity of the hydrogen-evolving enzyme systems. 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. A new system is also being developed that uses a metabolic switch (sulfur deprivation) to cycle algal cells between a photosynthetic growth phase and a hydrogen production phase.
Recent presentations and papers:
- Algal Hydrogen Photoproduction, Maria Ghirardi and Michael Seibert (2003) (PDF 645 KB)
- Molecular Engineering of Algal Hydrogen Production, Michael Seibert et al. (2002) (PDF 741 KB)
- Cyclic Photobiological Algal Hydrogen Production, Maria Ghirardi et al. (2002) (PDF 303 KB)
Contacts: Maria Ghirardi (303) 384-6312, Mike Seibert (303) 384-6279
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 PEC system produces electricity from sunlight without the expense and complication of electrolyzers, at a solar-to-hydrogen conversion efficiency of 12.4% lower heating value (LHV) 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.
Recent presentations and papers:
- Photoelectrochemical Water Splitting, John Turner (2003) (PDF 1.19 MB)
- Photoelectrochemical Systems for Hydrogen Production, K. Varner et al. (2002) (PDF 724 KB)
Contact: John Turner (303) 275-4270
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.
Recent presentations and papers:
- Fluidizable Catalysts for Hydrogen Production from Biomass Pyrolysis/Steam Reforming, Kimberly Magrini-Bair et al. (2003) (PDF 1 MB)
- Fluidizable Catalysts for Producing Hydrogen by Steam Reforming Biomass Pyrolysis Liquids, Kimberly Magrini-Bair et al. (2002) (PDF 751 KB)
- Hydrogen from Post-Consumer Residues, Stefan Czernik (2003) (PDF 922 KB)
- Hydrogen Production from Post-Consumer Wastes, Stefan Czernik et al. (2002) (PDF 387 KB)
- Hydrogen from Biomass-Catalytic Reforming of Pyrolysis Vapors, Robert J. Evans (2003) (PDF 1.93 MB)
- Engineering Scale Up of Renewable H2 Production by Catalytic Steam Reforming of Peanut Shells Pyrolysis Products, Robert J. Evans et al. (2002) (PDF 531 KB)
Contacts: Kim Magrini-Bair (303) 384-7706, Stefan Czernik (303) 384-7703, Bob Evans (303) 275-3708
Solar Thermal Water Splitting
NREL researchers have demonstrated that highly concentrated sunlight can be used to generate the high temperatures needed to split methane into hydrogen and carbon. Concentrated solar energy can also be used to generate temperatures of several hundred to over 2,000 degrees at which thermochemical reaction cycles can be used 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 that enhance the production rates significantly and more than compensate for the intermittent nature of the solar resource.
Recent presentations and papers:
- High Temperature Solar Splitting of Methane to Hydrogen and Carbon, Jaimee Dahl et al. (2003) (PDF 696 KB)
- Rapid Solar-thermal Dissociation of Natural Gas in an Aerosol Flow Reactor, Jaimee Dahl et al. (2002) (PDF 428 KB)
Contact: Allan Lewandowski (303) 384-7470
Renewable Electrolysis
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.
NREL's Distributed Energy Resource Test Facility is an ideal location for examining the issues related to renewable energy sources and hydrogen production via the electrolysis of water. The facility offers the flexibility of interconnecting various renewable sources to electrolyzers and their hydrogen-producing stacks. NREL is testing integrated electrolysis systems and investigating options for improved designs that will lower capital costs and enhance performance of the naturally varying power input from renewable sources to the electrolyzer.
Learn more about NREL's renewable electrolysis research and the wind-to-hydrogen project, which uses electricity from wind turbines and solar panels to produce hydrogen.
Contact: Kevin Harrison (303) 384-7091 or Ben Kroposki (303) 275-2979
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