THE GLOBAL POTENTIAL OF HYDROGEN by Pamela Peerce-Landers
Hydrogen may be an attractive replacement for fossil fuels. It can be made from renewable and sustainable resources and its product is water. Its use permits countries to reduce their dependence on imported oil, lessen greenhouse gas emissions and improve air quality. Over 40 nations have active programs including Argentina, Australia, Brazil, Canada, China, the 28-member EU and countries within it, Iceland, India, Japan, Korea, New Zealand, Switzerland, Taiwan, the United States and Venezuela. Although sometimes hydrogen may not be cheaper than the fossil fuel it replaces, individual decisions on its adoption will weigh the strategic and environmental benefits with economics and other local factors. I will summarize and critique a recent review on hydrogen research, review the results of process simulations of some renewable hydrogen production methods and then consider the medium- and long-term roles for hydrogen. Review of Research on Hydrogen Production, Storage and Detection
Dutta recently reviewed hydrogen research with a focus on its use as a fuel for cars and portable electronics. All production methods discussed use renewable or sustainable feeds and energy sources. I have categorized them by feedstock below. Feedstock Examples Mentioned Development Advantages Current Disadvantages Catalyzed thermochemical splitting using solar 4-step process using SO2 or nuclear energy for and NH3 with ZnO & other Uses abundant solar Sunny days required for metal oxide catalysts radiation solar concentrators Uses abundant solar Power source needed on Photovoltaic splitting radiation cloudy days Photochemical splitting Not discussed. Not discussed. Water splitting by microalgae, in particular, 1. Low photochemical Chlamydonomas efficiency. reinhardtii and Uses only water & 2. Serious inhibition of Biophotolysis cyanobacteria sunlight hydrogenase by O2 Hyvolution Project. 2 stage fermentation of Photofermentation sugar beets, molasses, Commericalize and dark fermentation barley straw & thick juice. after 2015. Not discussed. Not discussed. 1. Bacterial activity fluctuated 50% over daily Photofermentation of temp range vs. activity at acetate by bacteria, Can make hydrogen even constant temp. Rhodobacter capsulatus in winter in Ankara. 2. H2 yield just 15% of theory. 3 biodiesel production residues: bioglycerol, Abundant supply of Catalyzed steam bioglycerine-bioethanol cheap bioglycerol from Waste Biomass reforming mixtures & bioalcohols. biodiesel production. Not discussed. Residues from biodiesel Energy recovery production: lipid-extracted important to development Anaerobic microalgal biomass of microalgal biodiesel fermentation residues (LMBR's) industry. Not discussed. Low temperature catalyzed gasification Feedstock: fowl manure Uses waste for feed Not discussed. 1. Yields pure (100%) H2 and clean water using Alkaline inexpensive Ni catalyst. electrochemical 2. Low energy oxidation Urea from urine consumption. Not discussed. Bioelectrochemical production of H2 from Very high H2 recovery Electrohydrogenesis organic waste efficiency from waste Not discussed. Anaerobic fermentation Cheese whey Uses waste for feed Not discussed. Abundant supply of Photocatalytic hydrogen sulfide in Hydrogen decomposition of H2S Use of CdS nanoparticles natural gas plants & as catalyst refineries Not discussed.
Source: S. Dutta, “A review on production, storage of hydrogen and its utilization as an energy resource,” Journal of Industrial and Engineering Chemistry, (2013).
As Dutta notes, hydrogen storage is key to mobile applications. Ideally, the storage system is lightweight and inexpensive. Solid storage systems must be able to quickly take up and release hydrogen and function for many cycles. The following table summarizes various storage schemes:
H2 Uptake Storage State Class of Material Compound/Reaction Advantages Current Disadvantages 1. Low energy density by volume. 2. Large tanks. 3. High pressure (350- Compressed Hydrogen Hydrogen (H2) Instant availability 700 bars) 1. Energy intensive cryogenic storage 2. Weight of container 1. Instant availability 3. Losses due to 2. High storage venting when not in Liquid Hydrogen 1. High capacity 2. Lightweight 3. Inexpensive 1. Sluggish kinetics 4. Thin films operate 2. Even with thin films, Magnesium Hydride at room temperature full desorption takes 20 Metal Hydrides 5.0 to 7.7% and low pressure Calcium Hydride Not discussed. Insufficient capacity Sodium hydride (NaH) Not discussed. Insufficient capacity Metal catalysts supported on activated 4-fold better than Nickel Catalysts carbon alone Low capacity Magnesium rich Mg-Y- Ni alloys with 18R-type long period stacking ordered phases and very fine YH2 particles Not stated. Improved kinetics Not discussed. 1. Strong H2 adsorption Boron nitride 2. High thermal & Capacities about half Boron compounds nanotubes (BNNT's) 2.5 to 3.0% chemical stability that desired 1. Gaseous boranes in Ammonia borane H2 toxic & could (NH3BH3, interfere with fuel cell AB)/catalyzed Up to 19.6%. catalysts. hydrolytic 7.8% based on 2. AB regeneration dehydrogenation AB and water. High capacity done off vehicle. 1. Hydrogen in water 1. Metal catalyst also converted to H2 nanoparticles doubling H2 yield. aggregate, reducing 2. High purity activity, but use of hydrogen. supports can alleviate 3. NaBH4 solutions this problem. Sodium borohydride very stable, non- 2. NaBH4 regeneration (NaBH4)/catalyzed toxic & non- expensive and done off hydrolysis flammable. vehicle. 1. Insufficient stability. Li-N-H system 2. High desorption involving lithium temperatures. nitride, lithium imide, 3. Potential NH3 lithium hydride and evolution poisons fuel Nitrogen compounds lithium amide High capacity Metal organic Insufficient capacity at frameworks MIL-53 and MIL-101 respectively Not discussed. ambient temperatures Polyphenylenediamine Polyphenylenediamine/ with 1, 2 and 4 wt% Cryogenic 2.7 to 3.0% Not discussed. temperatures 1. Bio-renewable 2. Low adsorption 1. Adsorption requires Pyrolyzed Chicken energy suggests low temperatures Feathers Physisorption easy recovery 2. Insufficient capacity
Source: S. Dutta, “A review on production, storage of hydrogen and its utilization as an energy resource,” Journal of Industrial and Engineering Chemistry, (2013).
For a minimum driving range of 300 miles (500 km.), the U.S DOE's 2017 targets for low pressure hydrogen storage are:
4. Start time to full flow (at 20oC/-20oC):
5. Operational cycle life (1/4 tank to full):
Although a few of the above solid storage systems satisfy the gravimetric density requirement, none meet the kinetic or cycle life standards. Because hydrogen is flammable in concentrations of 4 to 74% in air and prone to leak through containment materials due to its small size, safety requires sensitive, reliable leak detectors. The ideal sensor is quantitative, has a low detection limit, responds and recovers rapidly, is highly selective for hydrogen and minimally affected by cold, moisture and contaminants. Odorants are out because they interfere with fuel cells. The detection methods mentioned were:
Specific Sensing Method Material Class Examples Advantages Disadvantages 1. Helps maintain H2 selectivity in humid 1. Response and recovery sluggish environments. vs. uncoated sensor, taking up to 8 Polymer-coated PMMA-coated 2. Change in resistance minutes at 65% humidity. metal oxide In2O3-doped greatest of 3 coated 2. Decrease in resistance less than Resistance semiconductors sensors. uncoated sensor. 1. Helps maintain H2 1. Response to low levels of H2 in Cytop-coated selectivity in humid dry environments very sluggish. In2O3-doped environments. 2. Decrease in resistance less than 2. Fast recovery uncoated sensor. 1. Helps maintain H2 selectivity in humid environments. 2. Fast recovery & much Fluoropel-coated faster reponse than Cytop- In2O3-doped coated sensor in dry Decrease in resistance less than conditions uncoated sensor. Liquid/solid electrolyte Not discussed Not discussed Heat of Combustion Metal catalyst Pd/Pt catalyst Not discussed Not discussed Acoustic Wave Not discussed Not discussed Thermal Conductivity Not discussed Not discussed
Source: S. Dutta, “A review on production, storage of hydrogen and its utilization as an energy resource,” Journal of Industrial and Engineering Chemistry (2013). The hydrophobic Fluoropel-coated indium oxide-doped tin oxide sensor was the most successful resistance sensor mentioned. However, the humidity exceeds 65% at times in many places. Additional work is required at 95% humidity. Dutta's focus was mainly academic. Costs, yields and disadvantages were not always mentioned. Reference was made to various hydrogen programs, pilots, e.g. power-to-gas and process simulation, but no details were provided. Commercialization of hydrogen from renewables, practical solid storage and sensors are well advanced. Water electrolysis accounts for about 4% of hydrogen production. In 2005, Sigurvinsson and Werkoff estimated the total cost of producing hydrogen by alkaline electrolysis in 4 countries for a plant capacity of 11,500 tons H2/yr. The countries were France, Iceland, Norway and the US. The estimates ranged from 1.6 to 5€/kg H2 depending on the cost of electricity which varied from 1 to
2.5€/kg H2. Electricity cost was the highest in the US. Current gasoline prices in these 3 European countries are 6-10€/gal. Since a kg of H2 is equivalent to a gallon of gasoline, when coupled with low cost electricity, water electrolysis can produce hydrogen at prices competitive with gasoline in Europe. Ballard offers biomass-to-fuel cell systems which it claims are competitive with diesel generators for power in remote areas, having a payback period of about 3 years. Regarding solid storage, McPhy Energy has overcome MgH2's kinetics problems. It sells commercial storage systems based on a nanostructured MgH2 graphite composite. Additives accelerate hydrogen adsorption and desorption. It has sold systems in Europe and Japan and is supplying equipment to store more than 1 ton of hydrogen for the INGRID project in Puglia, Italy. Practical hydrogen sensors are not far off. In 2010, researchers at Oak Ridge (ORNL) reported the development of a microcantilever-based hydrogen sensor using a nanostructured Pd/Ag alloy which met most of the DOE's requirements for automotive use. As of May, 2013, this technology had not been commercialized.
Performance Specification Requirement ORNL Sensor Performance Sensitivity Range <0.1% to >4% 0.01-10 % Survivability Limit Linear reponse to 100% H2 Automotive: < 3 sec Reponse Time Stationary: < 30 sec Automotive: < 3 sec Recovery Time Stationary: < 30 sec Automotive: -40 to 125oC Temperature Range Stationary: -20 to 50oC Automotive: 62-107 kPa Pressure Range Stationary: 80-110 kPa Automotive: 0-95% 0-100%, little response to Ambient Relative Humidty Range Stationary: 20-80% changes in humidity Interferent Resistance No false positives Excellent Power Consumption < 1 Watt 0.2-0.5 watts Operating Temperature Room temperature Room temperature Automotive: 6000 hrs. Demonstrated for more than Lifetime Stationary: >5 yrs. 12 months Automotive: 5-10% Accuracy & Repeatability Stationary: 10%
Source: ORNL Fact Sheet, “Optical Hydrogen Sensors for H2 Storage Systems ORNL is also working on optical sensors that don't use Pd. Element One has commercialized visual, reversible leak detection coatings for use in stationary applications coupled with electronic sensors. The color change pinpoints the source of the leak. Companies and governments need information on costs, yields, trade-offs, advantages and disadvantages for decision-making. There are two ways to obtain these data: computer simulations and actual demonstrations. The former is ideal for screening candidate processes, the latter for obtaining actual operating data and experience. Review of Process Simulations of Hydrogen Production from Renewable Sources
An Austrian team conducted process simulations to evaluate various hydrogen production methods. The minimum purity for the hydrogen product was 99.97%, fuel cell quality. The reference technology was steam reforming of natural gas. I have listed the other process below by feedstock. Plant Modelled Feedstock Hydrogen Conversion Feedstock Composition Location Capacity Efficiency Simulation Scenarios Schwechat, Natural gas (NG) Steam reforming OMV oil refinery 26 million kg Reference technology Norsk Hydro 5040 Alkaline water electrolysis electrolyzer Unspecified 382,000 kg Decentralized plant Stuart IMET 1000 electrolyzer Unspecified 47,000 kg Centralized plant for local refueling Steam reforming using Biogas from 1. Unpurified biogas fed to on-site, O instead of air to keep fermentation of decentralized, scaled-down NG 51-62% CH maize, potato peels N from interfering with Energiepark Bruck an der 429,000 kg for reformer. or biowaste 33-43% CO H2 purification biogas plant Leitha, Austria maize 2. Biogas used as fuel & heat source. 88-90% CH Same as above except CO removed 1-1.6% CO from feed. 1. Centralized plant. 2. Feed upgraded to natural gas quality and fed to grid. Fast Internally 1. Tar-free gas fed to on-site, Circulating decentralized, scaled-down NG gasification of Fluidized Bed for Güssing, reformer. wood chips Steam reforming gasification 915,000 kg 2. Gas used as fuel & heat source. Same as above except CO removed from feed using scrubber. 1. Centralized plant. 2. Feed upgraded to natural gas quality and fed to grid. Hydrolyzed mash of Dry wt% glucose 1.Decentralized. maize (M) or potato & starch: 52% Coupled dark & Assume 80% 2. Vacuum to limit H level which peels (PP) (PP), 100% (M) photofermentation Theoretical layout None 394,000 kg for both steps inhibits microbial activity Coupled dark 80% in dark Dry wt% glucose fermentation and biogas fermenter. Hydrolyzed mash of & starch: 52% fermenter to make CH - 70% in biogas 1. Decentralized. potato peels (PP), 100% (M) Theoretical layout None 202,000 kg fermenter. 2. Heat & electricity made in gas engine. 1. Decentralized. 2. Heat made in gas boiler 1. Decentralized. 2. CO removed. Gas fed to on-site steam reformer
Source: A. Miltner, et. al., Journal of Cleaner Production, 18, S52-61 (2010). Conventional steam reforming of natural gas was the most energy efficient process based on both the lower heating value (LHV) of the dry raw materials and the total energy in: 0.78 MW H2/MW raw material in and 0.8 MW H2/MW total energy in, respectively. The efficiency for alkaline electrolysis was 0.62 MW H2/energy in. It was assumed that electricity for electrolysis came from a sustainable source. Since water has no LHV, when comparing the various renewable processes studied, all efficienies below are in MW H2/MW total energy in. Of the bio-processes, steam reforming of biogas from the fermentation of maize was the best. The range for the 3 scenarios was 0.49-0.53, increasing with the purity of the biogas. Potato peels were a close second. The energy efficiency for biowaste was only 0.2. The energy efficiency for steam reforming gas from wood chips was about 20% lower than for biogas from maize or potato peels. Interestingly, energy efficiencies for the coupled dark/photofermentation of biomass sugars and starch were only about 10% lower than for centralized steam reforming of gas from wood chips, all being in the range of 0.3. However, as the authors noted, these processes were penalized by not using, or not being able to use, any of the gas or residues to self-supply heat as was done in the biogas fermentation schemes, suggesting these efficiencies could be improved.
Of the renewable technologies, alkaline electrolysis was the most energy efficient, besting processes using biofeedstocks by 20-60%. It also eliminates any conflict between using land for food vs. feedstock. However, a sustainable, reliable source of cheap power is needed for electrolysis to be economical. Though 50% less energy efficient in terms of the hydrogen produced, wood chips are appealing because they are waste. Pilots of Hydrogen Production from Renewable Sources The EU has just 2% of the world's reserves of natural gas. So, producing hydrogen from renewables is of interest. In 2007, there were 123 hydrogen demonstration plants in EU countries—27% of those in Germany. Although much has likely been learned, key information like the total cost of hydrogen production is too sensitive to publish. In April, 2012, Idex started up a pilot in Japan with a daily capacity of 7,200 Nm3 hydrogen from 15 dry tons of wood chips. The government provided 71% of the 2.1 billion yen needed to build the facility. BMW and the South Carolina Research Authority (SCRA) shared the cost of a $1 million pilot to study the feasibility of producing hydrogen from landfill gas to fuel BMW's Spartenburg fleet of material handlers. Medium-Term Roles for Hydrogen (Within 15 Years)
For 2011, the IEA reported the breakdown of global energy use was: 19% electricity generation, 30% transportation and 51% heating. Medium-term, hydrogen can play significant roles in generating electricity and powering vehicles. Generating hydrogen using wind, solar and geothermal energy can help manage the grid. Stored hydrogen can be fed to fuel cells (HFC's) to produce electricity in times of peak use. There are many power-to-gas pilots operating today. Remote and backup power are attractive applications. Some hydrogen systems require a site visit only once every 5 years making them ideal alternatives to diesel generators in remote areas. India is installing 65,000 base transceiver stations (BTS) annually. China has approved fuel cells for its BTS's. Because they are very reliable and furnish high quality power, HFC's are perfect backup systems for data centers, hospitals, prisons, etc. where power outages are intolerable. Hydrogen is also ideal for commercial fleets because they use centralized fueling stations. These include buses, port and local delivery trucks, forklifts and airport ground service vehicles. Performance is the same or better and refueling is fast. A few companies make hydrogen-powered cars. Currently, these are very expensive and have limited availability due to the high cost of HFC's and the lack of an adequate hydrogen infrastructure. Both problems can be solved. Recently, ACAL Energy announced it had successfully removed 80% of the Pt from its HFC's, reducing their cost 30%. A prototype was operated continuously for 9,000 hours. I believe that the high cost projections for building hydrogen fueling stations stem from assuming that they would have to replace existing gas stations one-for-one. There are 170,000 gas stations in the US. Nissan and Tesla are each building just 100 fast charging stations to cover 98% of the US and parts of Canada. Hydrogen stations in California cost about $1 million each, so an adequate national
network could be built for $100 million. The key is affordable, adequate capacity home refueling. Long-Term Roles for Hydrogen
Eliminating fossil fuels for electricity generation and transportation is possible. Although some companies are using hydrogen for space heating, converting all homes seems unlikely because of the availability of free fuels, e.g. scrap wood. For centralized renewable electricity generation, hydrogen's most likely role is energy storage to balance the variability in wind and solar sources. Centralized hydrogen production and distribution through repurposed natural gas pipelines is more probable where natural gas is scarce, like Europe. Germany has successfully coated existing natural gas pipelines and used them for hydrogen. Replacing diesel in long-haul trucks is more likely for large companies having depots scattered throughout the area where hydrogen stations can be located. The cost can be mitigated by the maintenance savings derived from eliminating the engine, transmission, cooling and emission systems. More rapid adoption might be achieved by combining HFC's with Li-ion batteries. The batteries provide propulsion and are charged by the HFC's and regenerative braking. Refueling with hydrogen takes a few minutes vs. 45 minutes plus to charge the batteries using a fast charger. Hybrid cars could eliminate the need for home hydrogen refueling as the batteries could be charged by electricity. Vision Motors uses this technology in its Tyrano trucks. Hydrogen-powered trains and ships have been demonstrated and may be long-term candidates. Conclusions Many countries are actively pursuing hydrogen as a replacement for fossil fuels in electricity generation, grid management, transportation and heating. Those with low fossil fuel reserves and high fuel costs are more likely to embrace hydrogen for strategic and environmental reasons. Considerable progress has been made in hydrogen generation from renewables, solid storage and leak detection equipment. Future challenges include:
1. Continuing to improve hydrogen economics by reducing the cost of hydrogen generation, fuel
2. Greatly increasing the availability of solid storage systems; 3. Developing robust, inexpensive sensitive, selective, long-lived hydrogen sensors with short
4. Building hydrogen fueling networks; and, 5. Eliminating the need for subsidies.
This last item is very important to the future of hydrogen because cash-strapped entities lose patience. The Czech Republic, Greece and Italy have all cut subsidies. Uncertainties exist in Australia and India. In some US states, all-electric car owners are being assessed a fee for road use since they pay no gas taxes. Similar measures would likely be enacted for hydrogen car owners.
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THURSDAY SPEAKERS Michael Gurevitz Symposium on “toxins and ion channels” Thursday 27 July “Mechanisms and specificity in the interaction of scorpion toxins with voltage-gated sodium channels” Michael Gurevitz was born in 1946 in Germany and received his BS, MSc and PhD degrees at the Hebrew University of Jerusalem. He spent six years (1981-1986)