Introducing a new type of fuel for transportation, whether for automobiles, trucks, trains or ships is a rare occurrence. Companies whose bottom line is directly impacted by the price of gasoline and diesel are considering natural gas as a fuel and are increasingly realising the economics are too compelling to be ignored.
In 2013, the spark-ignited Cummins Westport 11.9 L ISX12 G engine was launched to supply the regional haul truck industry in North America and is currently the only option for original equipment manufacturers (OEMs) in North America who want to offer a natural gas option in the medium-to-heavy duty segment.
With the launch of the ISX12 G, on board natural gas storage is key. All natural gas engines – whether they operate with spark ignition or through dual fuel (DF) technology – run on compressed natural gas (CNG). However, fuel can be stored as either CNG or LNG.
The choice between CNG and LNG
The decision about fuel storage on a Class 8 truck depends on driving range, terrain, fuelling access and vehicle weight. For light duty vehicles and return-to-base operations (such as in the refuse sector), CNG is the more obvious choice as the driving distances are predictable and vehicles can fill up overnight without affecting operable time.
For trucks in the medium to heavy duty segment, the choice is more complex. CNG tanks, for example, need greater space and weight allowances, to provide enough fuel for long distance travel over difficult or varied terrain. Cold LNG, however, provides more energy in a given space than either CNG or warm (saturated) LNG. The point at which the choice between storing fuel as CNG or LNG becomes crucial for fleets is around the 250 mile per day mark.
LNG tank system
Westport recognised the gap in the market for an LNG tank system which allows medium and heavy duty trucks to take advantage of the benefits of cold LNG: a further range and less weight than the equivalent amount of CNG storage.
The Westport iCE PACK™ LNG tank system is optimised for spark ignited (SI) and DF engines. With the iCE PACK, fleets can use cold LNG fuel stored at -150°C (2 bar). This technology includes a pump which supplies fuel to the engine under all operating conditions.
Most LNG tanks rely on tank pressure to supply fuel to the engine – as tank pressure increases, fuel vapour is released to decrease pressure and feed the engine. However, as the engine size increases, the engine demands more fuel, and tank pressure naturally declines during normal operation, which leaves the engine susceptible to fuel starvation.
Tank pressure during normal operation
The iCE PACK’s pump does not rely on tank pressure. It monitors the tank pressure and if it climbs greater than 150 psi, it releases vapour into a vaporiser, engine filter and regulator and feeds the engine fuel at 100 psi. If tank pressure falls below 150 psi, it releases liquid and follows the same process to feed the engine fuel at 100 psi.
All LNG is stored cold at the liquefaction plant at <1 psi. Typical tank solutions require fuel providers to warm up the LNG from the delivery temperature and pressurise it to >120 psi before dispensing. This involves an extra step for the fuel provider and can result in fuel loss back to the station during the equalisation process.
Since the iCE PACK accepts warm or cold LNG, fuel providers do not have to warm fuel for trucks to be able to fill up. This opens up more fuelling infrastructure flexibility for fuel providers and fleets.
The benefits of cold LNG
Using cold LNG allows trucks to fill up faster and drive further – it provides up to 10% more operating range compared to tanks using warm LNG. Filling the iCE PACK with cold LNG also enables longer storage time than warm LNG – it doubles hold times from five to ten days.
The iCE PACK is currently installed at Westport’s facility in Louisville, Kentucky. The entire system is on board and includes the LNG tank, hydraulic power module, integrated gas module, and driver display.
Once installation is complete, the truck is shipped to the dealer for fleet delivery. Orders are made through OEM dealers.
The Westport iCE PACK LNG tank system was launched with major OEMs in 2013 and is currently available on a variety of leading truck models including: Freightliner, Peterbilt, Kenworth, Volvo and Mack with both the Cummins Westport ISX12 G (400 hp) and the 8.9 L ISL G (320 hp) natural gas engines.
Written by Wesport. Adapted to house style by Ted Monroe
Read the article online at: https://www.lngindustry.com/liquid-natural-gas/21022014/westport_introduces_its_westport_ice_pack_lng_tank_system_/