There’s a train coming down the track, only this train is running on natural gas, a rare thing in the United States.

By Peter Hildebrandt

California’s  Napa Valley Wine Train is a luxurious wine-tasting and dinner train that goes on short runs up the Napa Valley and back. Converting its engine to run on natural gas (NG) involved replacing diesel injectors with spark plugs. Installing the complete engine package took about three months.

“The most unique thing about the Napa Valley Railroad locomotive is that it’s a throttleless NG engine,” says Scott Jensen, chief designer and projects coordinator with Energy Conversion Inc. (ECI) of Tacoma, WA. “We can achieve near-diesel efficiency by running a skip-fire arrangement. Other people have played with it, but we’ve done it; we make it and sell it, and fortunately we’ve got one going in California.”

The railroad received funding from the Carl Moyer Foundation, which specified that the train must run without diesel. Funds were applied for through the California Air Resources Board (CARB), for this cost-effective pollution reduction program.

A pipeline supplies NG to the facility in Napa, and the railroad has its own compressor for loading fuel into tanks onboard the locomotive. The Napa Valley Wine Train has four SPA-4 Canadian Alco locomotives. Only one of the trains was converted into a 100% NG-dedicated engine. Work started on the AMC EMD engine and its conversion in 2000.

ECI has gone on to do diesel-to-NG conversion projects for locomotives and power generation throughout the world, including such places as Indonesia, Peru, India, Angola, and Thailand, where the pipeline infrastructure is expanding fairly rapidly and the price of gas is roughly one-third that of diesel, according to Jensen. “I think the difference in NG and diesel prices may partly explain why there are so many more NG vehicles outside of the US and why it hasn’t quite caught on here yet,” says Jensen.

According to the Natural Gas Vehicle Coalition (NGVC), as of 2005 there were 130,000 light- and heavy-duty compressed natural gas (CNG) and liquefied natural gas (LNG) vehicles in the United States and 5 million worldwide. Approximately one of every five new transit buses in the United States is powered by natural gas.

Jensen, like the others involved with new NG technology and conversions, is excited about the future and what it holds for this energy source.

“It is safe to say that at current technology levels, new natural gas engines run cleaner. This doesn’t mean they are perfect,” says Jensen. “With more funding for a natural gas infrastructure, engine systems using NG could play a larger role in our transportation system, simultaneously saving fuel, money, our atmosphere, and all the while preserving our fuel security.

“I’m not selling natural gas; I’m selling engine systems that use natural gas,” Jensen adds. “But I think there tends to be a lot of confusion and misinformation out there about natural gas. We have an extensive supply here in North America, and that supply is stable for the long term.”

The United States imports very little natural gas from overseas. According to the US Department of Energy, net imports of NG are approximately 15% of the total used, with almost all the imports coming from Canada. This is one fuel source for which we’re not dependent on foreign sources.

“Any time a fossil fuel is run in an internal combustion engine in an uncontrolled situation, there are opportunities for creating some kind of emissions,” says Jensen. “But when you take the technology and run it toe to toe, in all cases natural gas runs cleaner than any other available fuel source.”

Flexibility in Conversion Systems
The Napa Valley Wine Train was the first US project undertaken by Innovative Technology Group Inc. (ITG). Nowadays ITG completes projects worldwide. It produces a customized or aftermarket solution for plants needing engines to provide their own power. The company installs an onsite system enabling engines to use NG.

ITG makes no changes to the engine itself, according to Raul Llanos, the company’s operations manager. “Our entire process consists of a few steps, and within two weeks we’re usually able to get a system up and running, depending upon the size of the engine involved,” says Llanos. “First we do the thermodynamic analysis, looking at the application, what the client’s specifications are, what’s currently being done with the engine, followed by a summary of what each engine can be expected to do using a particular fuel type, establishing Btus per cubic foot. After an analysis, we tell the client what to expect in terms of gas from dual fuel.

“If the proposal is accepted, the operations and control room are studied, along with the place the engine is situated and what types of communications need to be incorporated into the network.”

When the system is shipped, it includes a programmable logic controller set up for the specific application and mounted either in the control room or next to the engine, depending upon the size of the job. Cabling and sensors are mounted on the engine, as well, along with a special mixing device and the respective gas strain. This is usually installed on the exterior of the engine. The gas is administered through the engine’s air intake.

“This is not high-pressure injection of gas into the engine,” says Llanos. “Instead, it’s low-pressure fumigation through the air intake on the demand; as the engine ramps up its load, it will take the corresponding amount of gas into the engine.”

ITG does both bi-fuel and dual fuel systems. With bi-fuel, a system runs either 100% on one fuel, such as diesel, and then 100% on another fuel like natural gas. In a dual fuel system, since it’s not a closed-loop system, some diesel and some natural gas must be run. Some diesel fuel always must be used to supply the lubrication, according to Llanos. (Dual-fuel installations use diesel fuel as an ignition source and NG as the primary energy.)

“Our company’s emphasis is in the combustion aspects of the process,” says Llanos. “We analyze through proprietary simulation and analysis the so-called ‘sweet spot’ for each engine and its relative application.”

Prior to doing any type of engine conversion, ITG evaluates the applications and the fuels being used to provide the correct amount of gas that the engines can take. “There are limitations to the amount of gas that may be placed into a diesel engine,” says Llanos. “Not all diesel engines run or behave the same on natural gas; some take more and some less,” says Llanos. “We’ve converted engines up to 12.6 megawatts. These engines are used primarily for manufacturing processes, often running 24 and seven.”

ITG converts engines for plants that make cement, polyester, steel, tires, shrimp farm pumps for water recycling, and standby/emergency support generation for data centers. The engines run on different fuels, including heavy fuel oil (HFO), diesel, high-sulfur or low-sulfur content diesel, NG, or biogas. “The capabilities that we have in terms of analyzing the combustion process help us determine the proper mixing for each engine in its application,” says Llanos.

An engine running 100% on diesel will work at a certain percentage of substitution once the NG is introduced into the engine. Typically this may be around 60% NG to 40% diesel or vice versa. “Somewhere in there, there’s a happy medium for the operator,” says Llanos.
“The significant changes are that it essentially retains the same operating characteristics of the diesel engine while incorporating the virtues of a dedicated gas engine: You achieve the best of both worlds. In addition to reduced emissions and reduced cost for maintenance, there’s less lube and oil as well as extended life of the engine.”

ITG had participated in the international marketplace more than the domestic one because of the abundance of diesel engines or HFO used for prime power for many international industrial customers. “Our product fits very well into those marketplaces, because when you’re replacing 50% to 60% of the diesel or HFO with natural gas, the savings on those long-run-use engines are significant,” says Joseph Renner, ITG director of business development. “We’ve recently been involved in a project in Wyoming where they have two engines, Caterpillar 3512s involved in drilling for natural gas wells. Those two engines on a dual-fuel natural gas system will save that company close to $400,000 per year in fuel costs—just from those two engines. The company also has another 250 engines just in that Wyoming well field alone.”

ITG infuses the NG along with air and ignition, proportionately, in a small stream into the air intake. This is so that the engine is pulling the NG into the cylinder and the diesel fuel is actually the igniter of the NG. “The engine recognizes the proper rpms and combustion, and it throttles back its own diesel supply,” says Renner. “Typically, with the 100% air mixture of a diesel engine, we are taking up the percentage of the stream of air at a rate of 1.75 to 2.25 of the total air going to the engine as NG.”

ITG looks at each engine prior to the conversion, engine modeling on each one in order to establish a baseline for what the manufacturer suggests for 100% diesel use, cylinder temperature, exhaust temperature, and how it is going to the engine in the way of air and fuel. The company also studies the types of diesel fuels being used: high sulfur, low sulfur, bio-fuel, or HFO. Thermodynamic modeling of the engine allows for the study of substitution rates on each.

“We’re always looking for the optimal running conditions for an engine, such as the correct temperatures, pressures, horsepower, and the proper amount of fuel for the proper amount of power coming out of the back of that engine,” says Renner.

“But significantly, if you over-substitute on fuel, you’ll ‘crater’ your emissions; they’ll become worse. We’ve never run into another company that does all the modeling we’ve done. We have on staff a Ph.D. scientist out of Los Alamos National Laboratory who does all our modeling and computational fuel dynamics, among other things.

“Engines, in practice, do not operate consistently, meaning there are constant changes as demands rise and fall. Too much NG in an engine leads to secondary detonation within a cylinder, the phenomenon we all experience in college with old clunkers that kept firing after the ignition was turned off. That’s not good for the engine.

“Fuel mapping enables us to avoid physically going out and having to cut off the NG supply to the engine. The efficiencies we describe our engines as running at, with percentages of NG and diesel, are ones that the engines are running at.”

Conversion to Dual Fuel in Campus-Type Setting
The Watchtower Educational Center in Patterson, NY, has a Caterpillar 3508 Series Diesel generator with 1,000-horsepower capability. ITG made it into a diesel-NG dual fuel system. The center serves approximately 1,000 people in the 25 buildings on the site. The facility’s other two generators are 100% natural gas. With this diesel–NG equipment, the facility generates 725 kW at 13,200 V. Installation of this conversion system has enabled the operation to substitute close to 30% of its diesel fuel with NG.

“Diesel sources are more expensive for us than NG, so this was our initial concern, to try to save some funds by going with this technology,” says Juan Marta, operations manager at the facility.

“It has worked out well for us; we use it primarily for peak shaving, running an engine eight to 10 hours per day just to shed some of the peaks throughout the day. It’s more than just backup; it cuts down on our bill significantly. That’s our strategy at the moment. We have primary boilers and generators, and all the buildings are tied together.” The facility saves several thousand dollars per month on its power bill by using this approach, according to Marta. A local pipeline supplies the NG.

Emission Control Can Often Drive Development
ESI, a McKinney, TX–based company founded in 1999 and incorporated in March 2003, studied the latest regulations in emissions issued by the EPA. Its goal was to find a cost-effective solution for improved air quality and energy security.

“We found in studies that heavy-duty diesel engines contributed 40% to 45% of the nitrous oxides and particulate matter emissions in the transportation space,” says Jim Cole, vice president of marketing and sales.

“There also did not seem to be an evergreen solution to the existing installed-base, older diesel engines,” he says. “Those available used bolt-on kits for alternative fuel use, resulting in less power, less torque, unpredictable durability, and questionable customer satisfaction.”

ESI wanted to offer diesel-core engines converted to NG using as much of the existing diesel platform as possible. These could be “specified” as a new engine for a new truck chassis or as a new engine replacement in older diesel trucks powered with a similar engine footprint. What ESI came up with was a brand-new, model year 2006, OEM [original equipment manufacturer]-dedicated, natural gas engine [Phoenix NG 7.6L] meeting and exceeding current air-quality regulations.

ESI gasifies an older, heavy-duty diesel engine, the target being the Navistar DT466 (pre 2003), found in school buses, refuse trucks, beverage trucks, food trucks, or standby generator systems. “The idea is, if you have one of those in your truck, we can pull that old diesel out and put ours in,” says Cole. “It fits perfectly. We took the old diesel 466, redesigned it, and engineered it to a brand-new, current year, natural gas engine by applying spark plugs, lowering the compression from 17–1 down to 10.5–1. ESI engines have full, two-year, OEM warranty (100% parts and labor) and five-year emission warranty.”

This Texas company cryogenically treats heat-sensitive components (e.g. pistons, rings, valves) to offer customers engine durability and to accelerate the process for the EPA certificate of conformity and the CARB executive order for MY2006 sales.

“Our engine today is the cleanest heavy-duty engine in the nation by using those numbers relative to the two types of emissions,” says Cole. “This can be verified by pulling up the CARB and/or EPA Web site to compare against any heavy-duty engine, be it CNG or diesel.”

To date, ESI has repowered two Class-7 beverage trucks in Houston, a 2002 dump truck in California, and four beverage trucks from a large beverage fleet. ESI is developing business relationships in China, Bangladesh, and India.

In addition to the fuel being much less expensive, the maintenance on such engines is less, thanks to the low levels of carbon contained inside and because of the lower engine compression that once was housed in a high-compression diesel platform. Their oil and filter changes are up to three times less than traditional diesel engines, according to Cole.

“We design the engine before sending it out to one of three locations that manufacture the engines to our specifications,” says Cole. “We get the core of that older diesel engine from our engine exchange program and engineer it back to OEM specs or better before placing our new components inside: basically, an engine swap-out.

“The key to our improved engine performance and low emissions is our electronic control unit that offers the drivers on-demand performance. Unlike kits that bolt on, we map our software to the hardware we install. Our engine performance is better than what the diesel used to be.”

ESI uses 3,600-psi CNG tanks and takes the gas to a fuel regulator where its deregulated down to less than 90 psi and then sprayed into a throttle body where CNG injectors ignite the mist. This is one of the reasons, along with other patented hardware, ESI has brought its emissions lower than most heavy-duty engines in use today, according to Cole.

As far as sound goes, Cole says ESI’s converted engines start up like a car, sound like a car, and are equally as quiet. Whereas regular diesel engines are loud, ESI’s are up to 13 decibels quieter, if not more. “In addition to that, the engines have greater torque, more acceleration, and a higher horsepower,” says Cole.

ESI is targeting areas where local CNG dispensers are located. In Dallas and in Houston there are many around. ESI teams with the local fueling provider and CNG upfitters that can help provide a fuel-diversity solution for the fleet owner.

“There are over 1,500 CNG dispensers out there, but they are located around things like airports or major cities,” says Cole. “However, if a customer wants to have their own, they can actually tap into the existing natural gas pipeline offered by someone like Atmos Energy or any others and set up their own filling station compressing their own NG.”

There are big reasons for doing this: Fuel is inexpensive; an outfit uses what is needed on demand and doesn’t have to store it; it is clean as it comes from out of the ground; and CNG is much safer than diesel or gasoline, according to Cole.

“Many people don’t know that,” says Cole. “There’s never been a fatality associated with CNG. Many get it mixed up with propane. Diesel has an auto-ignition of 450 degrees Fahrenheit, whereas CNG’s is 1,350 degrees Fahrenheit.”

Safety aside, the DOE states that a number of natural gas vehicle owners report an engine life two to three years longer than that ofgasoline or diesel vehicles, as well as extended time between required maintenances. So, one hopes, those trains, vehicles, and engines will be around long enough to confirm the improved track record.

Peter Hildebrandt is a writer specializing in science and engineering topics.

DE - March/April 2007