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21 January 1998
For Immediate Release

Integrated Storage System Certified for CNG Vehicles

This past December The Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md., in conjunction with Lincoln Composites, Lincoln, Neb., completed a 3-year effort to advance the state-of-the-art in compressed natural gas (CNG) storage with a full safety-certified unit called the Integrated Storage System (ISS).

Work on the ISS is a task under APL's Advanced Natural Gas Vehicle (ANGV) program, cost-shared by the U.S. Department of Energy's Office of Advanced Automotive Technologies and the Gas Research Institute. The goal of the ANGV program is to advance the technology and expand the marketplace of light-duty natural gas vehicles (NGVs).

With the ever-growing concern about "greenhouse" gases, U.S. dependency on foreign oil, and the increase in demand for oil in emerging nations, the need to accelerate the growth of NGVs is apparent. Natural gas has many advantages over petroleum. Its reserves are vast and widely distributed throughout the world, it does not need a costly refinery to render it into a vehicle fuel, it is easily distributed by a vast existing network of pipelines, and it is ultra-clean in burning.

In spite of these advantages, NGVs have remained in the limited "niche" markets of transit buses, delivery vans, and some taxis. This limitation is largely a result of the cost, weight, size, and vehicle packaging considerations associated with existing CNG storage cylinders. Development of the ISS is intended to remedy this limitation and permit widespread use of natural gas technology in passenger cars.

The Integrated Storage System partitions the roles of pressure containment and tolerance to damage, and it optimizes each role through the use of composite materials and an innovative package design.

ISS uses lightweight, all-composite, high-strength (3,600 psi service pressure) pressure cells (i.e., cylinders) encapsulated in an impact-absorbing foam within a high-strength fiberglass shell.

The pressure cells employ a unique hybrid overwrap of high-strength carbon and super-tough glass filaments that are wound with an epoxy resin around a gas-impermeable High Density Polyurethane (HDPE) thermoplastic liner. The pressure cell overwrap thickness is optimized based on safety, weight, and cost.

The ISS outer shell, in concert with the impact-absorbing polyurethane foam, unitizes the pressure cells into a single container and provides protection from external impact as well as from environmental exposure. The ISS shell is a low-cost fiberglass vinyl ester laminate with rigid urethane foam co-cured within the shell structure to form a lightweight, high-strength structure. The interior of the shell is similar to that of an egg crate in the protection it affords to the pressure cells. The outer shell is formed using the Seemann Composites Resin Infusion Molding Process (SCRIMP). The high-density polyurethane foam is similar to that used in automotive interiors.

The ISS is assembled at the factory as an inseparable container. As a single container, the unit has one manual service valve, one solenoid, and a thermally activated pressure relief device all in a highly integrated gas control unit. The gas control unit is safeguarded from impact with a high-strength fiberglass cover that is removable for component service. The cover also serves to capture any outgas leakage and port it to a safe area.

Similar in shape to a conventional gasoline tank, the ISS is attached to the vehicle chassis with steel straps. This method of attachment simplifies assembly-line logistics and allows the vehicle's "crumple-zone" to work as intended in the event of a severe rear-end collision.

The ISS has been designed and tested to comply with the Federal Motor Vehicle Safety Standard FMVSS #304, Compressed Natural Gas Fuel Container Integrity, and the American National Standard Institute, American Gas Association Standard, ANSI/AGA NGV3.1-1995, Fuel System Components for Natural Gas Powered Vehicles. These requirements have been meet through an exhaustive series of tests including hydrostatic burst, pressure cycling, bonfire, drop impact, filling in extreme cold, roadway vibration, and gunfire.

Application of ISS in a dedicated, natural gas-powered mid-size sedan is another facet of the ANGV Program. Work is ongoing among APL, Chrysler Corporation, and other OEM suppliers on a technology demonstration prototype that is scheduled to make its public rollout in the Fall of 1998.



For more information contact

For more information, contact APL Public Information Officer Helen Worth; phone: 240-228-5113 or 410-778-5113. For technical inquiries, contact John Wozniak (APL) at 240-228-5744, or W. Dick (Lincoln Composites) at (402) 465-6548.