Specialized metallurgical processes – compositions for use therei – Compositions – Loose particulate mixture containing metal particles
Reexamination Certificate
2000-03-13
2003-07-08
Mai, Ngoclan (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Loose particulate mixture containing metal particles
Reexamination Certificate
active
06589312
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the storage, transportation, and distribution of hydrogen and other low density fuels using nanoparticles.
BACKGROUND OF THE INVENTION
Hydrogen for use in fuel cells (and possibly as a fuel in internal combustion engines) appears poised potentially as the next major evolution in energy usage. Unfortunately, safely storing hydrogen and other low molecular weight fuels is currently very difficult and expensive. Such fuels are now stored in pressurized tanks or in hydride storage systems. Hydride storage is far safer than compressed hydrogen gas storage, and safer even than gasoline on an equivalent-energy basis (Reilly, J.
J. Sci. Amer
. 1980, 242(2), 2). However, hydrides carry both weight and cost penalties versus compressed hydrogen. As another alternative, hydrogen can be created as needed by reformers, but efficiencies are reduced. Hydrogen vehicle systems' space and weight penalties versus gasoline are about 5 times the space if stored as compressed gas, or still 3 times the space plus between 40 to 470 extra pounds of weight if stored as a metal hydride, even after taking into account the greater efficiency of hydrogen fuel cells (HFCs) versus gasoline internal combustion engines (ICEs). Additionally, these space limitations require storage to be closer to passengers, compounding safety concerns.
These storage limitations penalize not just on-board vehicle storage and vehicle range, but also the capacity for overall transportation and distribution of hydrogen versus gasoline or other existing fuels, and its storage prior to use. These limitations in turn limit where, how efficiently, and how cleanly hydrogen can be produced. For example, hydrogen generation onboard vehicles from methanol or gasoline reformers cuts total emissions only 7-35%, while steam reforming at service stations would reduce emissions by 40%, and remote generation would reduce emissions by 60-70%, given a practical and economical storage method. A better method of both on-board storing, and transporting and distributing, of hydrogen, including pure HFC vehicles would have a significant and broad positive impact on this emerging new industry.
Generation of hydrogen at the site of remote electric power generating plants and then shipment of the hydrogen to markets using economical storage systems could entail less energy loss than if electricity is transmitted to local service stations for generating hydrogen on site. Cheaper natural gas costs could also be accessed by generating hydrogen closer to the sources of gas. Economies of scale of larger volume hydrogen production could be realized. Transmission-distribution wires in many cases could be avoided. And attendant air pollution could be removed from the local area urban centers, where smog is the principal concern. Renewable energy supplies (solar, wind, etc.) could also be accessed given an economic transportation system.
Stationary HFCs are likely to be introduced in homes and industry concurrently with vehicular use. Because manufacturing costs of HFCs and hydrogen generators will both decline with the volume permitted by introduction of HFCs to the vehicle market, HFCs should simultaneously begin penetrating homes and industry, for both heating and electricity. Whereas the proton exchange membrane (PEM) HFC is targeted for vehicles, with an efficiency of about 50% versus 25% for the ICE vehicle, still higher-efficiency fuel cells are being developed for stationary use, with efficiencies of 60-80%, versus 30-60% for conventional power generation (the upper ends of ranges in both cases including cogeneration). These stationary fuel cells include the molten carbonate, phosphoric acid, solid oxide, alkaline, direct methanol, and other fuel cells.
HFCs for portable power products, such as, but not limited to computers, can be introduced concurrently with vehicular use; again, riding the cost and technology curves developed for HFCs and hydrogen generation for the other markets. These stationary HFC markets, portable power product markets, and vehicle HFCs will all require hydrogen to be safely, inexpensively, and conveniently delivered, as well as stored before use.
HFC's main problems are vehicle range, safety, and hydrogen fuel availability. These problems are all in turn aspects of the problem of hydrogen storage. A HFC system may achieve the same range as for gasoline ICE (a usual target being 380 miles), but 3-5 times the space and possibly far greater weight are required compared to gasoline. The extra space required also adds to real or perceived safety concerns. These space and weight penalties also affect the ease of transportation and distribution of hydrogen, which in turn makes vehicle range concerns still more sensitive. The space and weight limits, and associated safety concerns, represent the largest negatives for HFCs.
Most critical is the space required for compressed hydrogen storage. Hydrogen today is stored at 2,000-2,500 psi (14-17 mPa) and requires large, heavy containers. Even at 5,000 psi, the standard currently being pursued for development in the auto industry, the space required is still about 5 times that of gasoline, even after allowing for the greater efficiency of the HFC versus the ICE. Table 1 summarizes these limits, along with weight limitations of the various systems.
This greater space requirement either limits the vehicle's range between refueling—especially important with a limited hydrogen infrastructure—and/or requires storage closer to passengers, raising safety concerns.
TABLE 1
Space and Weight of Fuel and Tanks for 380 Mile/Tank Range Vehicle
5000 Psi
Gasoline
Hydrogen
Hydride
Mileage
29 mpg
64 mpg (2.2 times
64 mpg (2.2 times
gasoline ICE)
gasoline ICE)
Gallons
13 gallons
4.7 kilograms
4.7 kilograms
Tank Size
14 gallons
Volume
1.87 cubic ft.
9.36 cubic ft.
5.7 cubic ft.
Volume versus
—
5 times
3 times
Gasoline
Weight Fuel
73 lbs.
10.3 lbs.
10.3 lbs.
Weight Tank
29 lbs.
100 lbs.
140-570 lbs.*
Total Weight
102 lbs.
110 lbs.
150-580 lbs.*
Weight versus
—
Similar
+40-470 lbs.*
Gasoline
*Lower weight is magnesium hydride; higher weight is more economical and currently practical iron-titanium hydride.
Source: “Onboard Compressed Hydrogen Storage,” by Brian James, C. E. Thomas, and Franklin D. Lomax, Jr., Directed Technologies, Inc, Arlington, Va., February 1999.
If hydrogen gas were compressed to 10,000 psi (also being considered for development), it would occupy about the same space as liquid hydrogen; but this is still about 3 times that of gasoline. However, even pressurizing to 5,000 psi may raise some significant safety concerns, and pressuring to 10,000 psi, when and if economically possible, might simply add to those concerns. Liquid cryogenic hydrogen storage requires very low temperature of −253° C.
Liquid cryogenic hydrogen, which takes up 3 times the space than gasoline, is impractical due to the extremely low temperatures required (minus 423 degrees Fahrenheit), the energy and cost that must be expended to liquefy hydrogen (approximately doubling its delivered cost), and the losses during storage as the liquid hydrogen slowly boils off and escapes. Some such losses might also occur in 10,000 psi compressed hydrogen gas.
Hydrogen has many safety concerns. Hydrogen must in any case be compressed to a significant pressure, since uncompressed hydrogen (i.e. , at atmospheric pressure) has only 1/1330 the energy density, and thus takes 1330 times the space, of gasoline. The onboard vehicular storage of hydrogen gas at any pressure raises safety concerns in the event of an accident, since the storage tank must be far stronger than that for gasoline to prevent rupture. The sudden release of such highly compressed gas could itself pose a significant safety hazard in the event of an accident, spewing an instantly flammable cloud.
Slower leaks likewise pose an ongoing concern. This is especially true since parking indoors would create its own safety problems, which would require re-engineering buildings. This is because hydrogen rise
Brumlik Charles J.
Snow David G.
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