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Adsorption Technology Could Be NGV Fueling Breakthrough

A fueling tank technology advance by a Northern California-based startup that promises to make it easier to fuel natural gas vehicles (NGV) at relatively low pressures at home could hold the key to a mass market for NGVs. A state-approved test of a vehicle is ongoing by Fremont, CA-based Cenergy Solutions, and other tests are coming with its partners.

Cenergy COO Gary Fanger told NGI on Thursday that he hopes to be marketing the company's fueling system to fleets and some consumer markets by the end of this year. He said the technology has the potential to slash the fueling tank and operating costs, along with providing a more flexible, safer fueling system that can be more readily molded to fit the contours of the vehicles in which it is installed.

"Operating at 500 psi compared to 3,600 psi makes a huge difference," Fanger said. "Ultimately, we have the complete system, although we still need some approvals for the compressors; our tanks can be filled at any fueling station."

The key to the potential breakthrough is "adsorbent natural gas (ANG)," which has been around for the last two decades, but several technological challenges have kept it from potential commercialization until now, Cenergy officials said.

"Adsorbed natural gas simply makes the physical storage and performance of the fuel delivery work better on board the vehicle," said Chris Galati, an engineer with one of Cenergy's research partners, Portland, OR-based NW Natural. "It allows more CH4 molecules in the gas to readily adhere to the surface of tanks, and the more surface area you can create, the more molecules you can contain in a tank."

For Galati this is "exciting" for two reasons, he told NGI on Thursday. It allows the "squeezing" of more gas into a tank to extend the range between refueling, and it allows storage of the same amounts of gas at lower pressure.

"You can get a lot more at 800 psi [Cenergy touts less than 500 psi] than you could at a standard tank at 3,600 psi," Galati said. "You're getting a lot more range at lower pressure, and that can lead to lower compressor costs up to 20%, so there are some really exciting options around ANG."

Coined by a German physicist in the late 19th century, "adsorption" is a surface-based process, compared to the more common "absorption" in which a whole fluid permeates or is dissolved by a liquid or solid.

Boasting a patent-pending technology, Cenergy's ANG system promises greater single-fill fueling ranges with compressed natural gas (CNG) tanks based on lower pressure requirements, according to Cenergy. The ANG system controls the adsorption and release of natural gas going into the fueling tanks and optimizes the volumes of methane that can be contained in and eventually released from the fuel cylinder.

The technology can be used in "many of the fueling cylinders now in operation," Cenergy said. Fanger is touting his technology as a "game changer" for the NGV industry, which currently is focused on the fleet vehicle market. ANG could broaden the market for NGVs.

Cenergy said it has so far tested its ANG technology on a passenger vehicle with an 8.1-liter General Motors (GM) engine for more than 10,000 miles, working in collaboration with Seattle-based nano engineering specialists at EnerG2. The firm specializes in working with polymer-based carbon materials for high-performance energy storage.

"We're trying to eliminate the gasoline-driven vehicle, and our partnership and collaboration with Cenergy Solutions is certainly pushing us down that path," said EnerG2 CTO Aaron Feaver as part of an announcement from Cenergy.

EnerG2 holds the patented adsorbent and Cenergy the patent-pending equipment that makes the system operable, storing large amounts of natural gas at low pressures. Most of the stored CNG is under 800 psi, which means vehicles could be fueled from home or business pressured natural gas systems.

Using the 8.1-liter GM engine test vehicle, with the largest GM engine ever built, Cenergy has subjected the test vehicle to heavy payloads, high altitude and cold weather, logging more than 10,000 miles with a fueling range  of more than 440 miles, using the ANG cylinders.

Galati said NW Natural intends to bench test and then field test in one of its NGV fleet vehicles the Cenergy-EnerG2 technology this spring and summer. "We think it works in theory, and now we're going to get some empirical evidence to support our theory," he said.

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