1. Field of the Invention
This invention relates to storage vessels for compressed fluids. More specifically, it relates to light-weight storage vessels conformable to a desired geometry.
2. Brief Description of the Related Art
As the prices of gasoline continue to rise and the damaging effects of exhaust fumes exerted into the atmosphere by gasoline combustion engines come to the forefront of public attention, natural gas vehicles rapidly gain popularity. According to some estimates, currently, more than 15 million vehicles worldwide are fueled by compressed natural gas (CNG), and their number is growing. CNG has a much lower emission profile than any other fossil fuel, while providing comparable mileage per gasoline gallon equivalent (GGE), making it an attractive environmentally-friendly alternative to gasoline and diesel. Natural gas is fairly abundant in many parts of the world, including the United States, and commonly costs only a fraction of the price of gasoline, making CNG an astute choice from an economic perspective.
Natural gas vehicles face a number of issues that must be resolved to facilitate a widespread adoption of this technology. One major problem arises with respect to storage of CNG in a vehicle. Gas is typically stored in spherical or cylindrical vessels because of their inherent abilities to resist internal pressures. Conventional CNG tanks are made of steel, making them very heavy and unwieldy. For automobiles, cylindrical CNG tanks are generally placed in the trunk, where they occupy considerable volume and add excess weight. Accordingly, what is needed is a light-weight storage vessel capable of withstanding high internal pressures and conformable to desired geometries better suitable for unobtrusive placement in vehicles.
This problem was recognized by others, but was addressed through inferior approaches. For example, patent no. EP0633422 discloses a CNG storage vessel that may be formed to different shapes. The storage vessel relies on a number of internal I-beams that are welded or diffusion bonded to the interior walls of a vessel, which is made of superplastic material. Such design creates a number of problems. The I-beams add additional weight, while welding may weaken the structure and create failure points, therefore, compromising the safety of the tank when it is filled with a highly pressurized gas. Accordingly, the solution offered by EP0633422 has several serious flaws, all of which are eliminated in the present invention.
A similar solution to the one provided by EP0633422 was offered by U.S. Pat. No. 5,323,953 assigned to the automotive giant Rolls-Royce. This prior art reference teaches a multi-layer sheet metal sandwich structure with a predetermined pattern of solid state diffusion bonds between all neighboring layers. The diffusion bonds reinforce the vessel, thus making it suitable for containing highly pressurized gas. This design employs heavy sheet metal and diffusion bonds, which increase the weight of the vessel.
The present invention utilizes a much different design that eliminates the aforementioned drawbacks present in the prior art. In view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.