03-08-2012, 02:46 PM
HYDROGEN FUEL CELLS
HydrogenFuelCell.ppt (Size: 49 KB / Downloads: 176)
Molecular Hydrogen Generation
Three different scales of generation: Central Station, Midsize, and Distributed.
Central Station: 1,080,000 kg/day would support 2M cars. Distributed by pipeline. Generated by fossil fuel or nuclear energy.
Midsize: 21,600 kg/day would support 40k cars. Distributed by cryogenic truck. Generated by natural gas or biomass
Distributed: 480 kg/day would support 800 cars. No distribution system needed. Renewable fuels used.
Carbon Dioxide Sequestering
No advantage to Hydrogen production from fossil fuels as far as reducing Carbon Dioxide is concerned. Yet this is the cheapest method to generate Hydogen.
Currently, only 4% of Hydrogen is from electrolysis; the rest is from coal, oil and natural gas, which contains about 10% CO2 as well as the Hydrogen.
Norway injects CO2 into saline aquifer.
Los Alamos study of CO2 injection into magnesium formations (Peridotites, serpentinite, Gabbro, and Basalt)
Costs about $8 per ton of CO2 disposed. Permanent and no legacy problems for future generations.
CO2 and Hydrogen from fossil fuels
Small increase in cost to capture CO2 when hydrogen produced by fossil fuels.
Using coal as feedstock, sulfur captured along with CO2.
CO2 sequestering and storage costs about $4.00/barrel of oil, $24/ton of coal, $0.54/cubic feet of natural gas.
New infrastructure required to transfer CO2 from H2 production to storage.
Deep ocean already stores CO2, may give it up with warming.
World’s biological storage now 700 billion tons. To double this storage would require doubling vegetation.
Hydrogen production--Renewable fuels
From wind energy. Electrolyze water. Wind is the most cost effective renewable energy source: $0.04 to $0.07/kWh costs about $6.64/kg per H2 if grid back up used.
From Biomass. Only 0.2 to 0.4% of solar energy converted to H2. Costs $7.05/kg by gasification, not including fertilizers and land degradation.
From Solar energy. Either by electrolysis (Photo voltaic) or using photoelectrochemical cell (in a early stage of development). Cost now is $28.19/kg and solar energy is only available 20% of the time.
Hydrogen safety
Small leak more flammable than for gasoline, but more likely to disperse, so ignition less likely.
Static spark can ignite, so ground during transfer.
Detonation more likely than with gasoline because of wider flammable concentration and higher flame speed.
Need high pressure to transfer efficiently: 5-10k psi.
Odorless, burns with a blue flame. Small molecule precludes adding scent molecule.