| August 03, 2011 |
Alternative fuels (first of a 3-part series)
Natural gas and propane autogas
These are truly “green” fuels, all-American, cost competitive and loaded with horsepower. For medium- and heavy-duty truck applications, though, these fuels can’t be beat.
By Tom Jackson
It used to be simple. There was diesel, and there was gasoline.
Now there’s gasoline, E10 gasoline-ethanol blend, E15 (maybe), E85, diesel, ultra-low sulfur diesel, B5 biodiesel, B20, B100, propane autogas and natural gas.
And, as if keeping up with all these new fuels wasn’t enough, as an equipment owner or manager you have to come up with different maintenance processes and protocols for each type of fuel. Failure to adapt to the peculiar maintenance requirements of each fuel could compromise anything from a $300 chainsaw, to a $50,000 truck or a $600,000 bulldozer.
There’s a lot to cover in this topic so we’ve broken it down into a three-part series. This month we’ll talk about natural gas and propane autogas used in trucking applications. In the months to come we’ll write about ethanol-gasoline blends and biodiesel.
Which gas is which?
There are a lot of terms thrown about when it comes to describing natural gas and propane, which leads to some confusion. But when drilling companies tap into underground gas deposits, what comes up out of the hole is a mixture of methane, propane, propylene and butane. The important ones for our discussion are methane and propane. Here’s how they compare:
Methane (often called natural gas) has qualities that make it useful as an industrial fuel, but it has to be compressed or chilled to turn it into a liquid, which adds some cost and complexity when used in automotive or truck applications. The acronyms used to describe it as a fuel are CNG (compressed natural gas) or LNG (liquid natural gas). Natural gas has a high octane rating –120 to 130 – which makes it best suited for high-compression engines, built specifically for CNG or LNG. Natural gas has about 20 percent less energy density than diesel but it sells for the equivalent of $1.70 to $1.90 a gallon.
There are a variety of state incentives for natural gas use. To find out what your state offers go to www.afdc.energy.gov/afdc/fuels/natural_gas_laws.html and click on the map.
Propane can be stored as a liquid at relatively low pressure (about 200 psi) and has none of the storage and handling complications of CNG and LNG. It’s the same stuff that powers home heating systems and barbeque grills. Sometimes the acronym LPG (liquefied propane gas) is used to describe it, however for automotive applications the preferred term is now autogas or propane autogas. Propane also has less energy density than gasoline, so to get the same range as a gas engine, propane powered vehicles need larger fuel tanks. But that’s its only drawback. You need a pressurized fuel storage system, different injectors and hardened valve seats to make a propane engine work, but these aren’t difficult to add as retrofits or build into new designs. Propane is currently selling for about $2.15 per gallon equivalent.
For state propane laws and incentives go to www.afdc.energy.gov/afdc/Fuels/propanelaws.html.
One of the most important attributes of propane and natural gas is that they are the best fuels when the goal is to reduce imported oil. Ninety percent of the propane used in the United States is produced in this country, and gas well drilling and exploration is fueling a major boom in heavy construction in Western Pennsylvania, southern and eastern Texas, and Wyoming and Montana. Natural gas already accounts for 24 percent of the electricity generated here.
On the environmental side, natural gas and propane autogas burn much cleaner than gasoline or diesel. Emissions of greenhouse gasses and exhaust pollution are as much as 24 percent lower than traditional fuels on a gallon-per-gallon equivalent.
Ford’s push to propane
Ford has been interested in the alt-fuel universe for quite some time, says Joe Thompson, president of Roush CleanTech. And when the blue oval engineers tasked the Roush engineers to find the best alternative to gasoline in its medium- to heavy-duty trucks and vans the answer came back – propane. Their reasons?
• Performance: Propane performs as well as gasoline in terms of horsepower and torque (see chart below).
• Cost/benefit ratio: The cost of the vehicle hardware is reasonable and lower than any of the alternatives says Thompson. Roush CleanTech on its website (www.roushcleantec.com) has a calculator you can use to figure the propane installation costs for its trucks or vans. In one example it costs about $16,000 to convert a new Ford F-450 or F-550, but 200,000 miles later the owner will save almost $33,000 in fuel costs (compared to gasoline at $3.50 per gallon). As the price of gasoline goes up the payback point comes earlier. The breakeven point typically lands somewhere before the middle of the vehicle’s first lifecycle. The bigger the engine, the better the payoff.
• Pumps often free for fleets. Propane pumping station costs vary but average about $20,000 to $50,000. But many of the gas companies such as Ameri-Gas, Ferrellgas and Heritage Propane will put in a pumping station for free in return for the fuel contract, even if you have a relatively small fleet, as few as eight trucks in some cases. In addition to propane costing less than gasoline, end users who have their own propane pumps can collect a 50-cent-a-gallon tax rebate from the Federal government. Note that this tax credit may expire at the end of this year unless Congress decides to renew it.
Keep it simple
Roush CleanTech also chose the propane route because of its mechanical simplicity, Thompson says. Basically, all you change is the fuel tank, the fuel lines and the fuel injectors. For retrofits on some earlier models of Ford trucks and vans, hardened valve seats and new heads may be required as propane lacks the lubricity of gasoline. On conversions from the factory for new vehicles the hardened valve seats come as part of the package.
Most commercial users of propane fuel run what’s called a “hub-and-spoke operation” – in other words, the trucks or vans leave the yard or warehouse every morning and return to the same place every night. And the hub is where the refueling station is located.
(One point of clarification: Roush CleanTech makes these propane systems for Ford trucks and vans only; for other brands consult with a dealer or third party retrofitter. A list of those can be found at the end of this article.)
The fuel lines run up into a solid billet aluminum fuel rail. This is a single machined piece. It doesn’t have the seams and multiple pieces of a gasoline fuel rail, which might leak under propane’s pressurized system. Robust injectors and a screw-in design for the fuel filler neck (to maintain pressurization during fueling) round out the hardware spec sheet.
Roush CleanTech has also developed a fuel pressure control modulator that regulates the pressurization throughout. It backs off the fuel pressure in the injector at idle and clears out the fuel lines when the vehicle is not running. Roush is also one of only two companies that Ford allows to have access to their factory software codes. This enables them to do custom calibrations of the factory control module for better diagnostics and help make the propane engine management identical to gasoline.
Fuel tanks and range
Roush CleanTech designed its tanks in two sizes to make sure you get good range. For example, the Ford F-150 offers an underbed configuration that holds about 20 gallons and a larger in-bed tank with a 46-gallon capacity. At 11 to 12 mpg, that gives the smaller tank at least 220 miles of range, and the big tank can take you more than 500 miles before refueling.
This brings up the most important consideration in evaluating the suitability of propane for your fleet. Most commercial users of propane fuel run what’s called a “hub-and-spoke operation” – in other words, the trucks or vans leave the yard or warehouse every morning and return to the same place for every night. And the hub is where the refueling station is located.
That’s not to say you can’t get propane anywhere other than your own pump. There are more than 2,500 propane refueling stations across the country. For the locations of these go to www.drivealternatives.com, or www.afdc.energy.gov/afdc/locator/stations.
There are no additional service or maintenance steps to take with propane powered vehicles, and Thompson recommends you stick with the factory service intervals on things like oil, coolant and filter changes. What you may find, however, is that your oil stays in better shape longer with a propane engine. That’s because the lower carbon content of propane, means less soot accumulating in the oil, and soot levels are often the determining factor in oil life. You’ll also keep your spark plugs cleaner since there is less carbon buildup. And propane, as it changes from a liquid in the tank to a gas in your injectors, helps keep your engine cool, especially the intake valves.
The Texas Railroad Commission has reported a 50-percent reduction in maintenance costs from running propane as compared to gasoline in its vehicles. If you want to extend drain intervals, however, do so only with the blessing and advice of your truck or van dealer.
Natural gas vehicles worldwide
With just 122,000 natural gas vehicles currently, North America is far behind the rest of the world in their adoption of this resource. Here are some of the leaders:
Pakistan: 2.3 million
Argentina: 1.8 million
Iran: 1.7 million
Brazil: 1.6 million
The environmental community, once supportive of natural gas, has turned against it citing concerns over underground water pollution caused by the drilling method known as hydraulic fracturing or “fracking.” But given that the gas in these formations sits thousands of feet underground and most water sources are 100 feet deep, the issue remains debatable. In 2010 the Pennsylvania Department of Environmental Protection issued a report that said: “No groundwater pollution or disruption of underground sources of drinking water has been attributed to hydraulic fracturing of deep gas formations.”
Additional sources for propane conversion
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