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By Dan Crummett
Progressive Farmer Contributing Editor
The diesel engine has been around for 120 years. New technology and a variety of fuels help it stay strong. (DTN/The Progressive Farmer photo by Jim Patrico)
The first diesel engine sputtered to life 120 years ago in Germany. It didn't take long for it to become the dominant workhorse on farms.
Today, there is a lot of talk about alternative new ways to power farm vehicles. But based on the efficiency and reliability of the rugged diesel engine -- and the fuel infrastructure that supports it -- diesel power will be king for a long time to come.
In fact, compression-ignited compounds are likely to remain the dominant "growth fuel" between now and 2035, along with increasingly efficient diesel engine technology, according to recent reports from the International Energy Agency.
DIESEL FUEL SOURCING
Product managers of OEM farm equipment say, "Where the diesel fuel comes from" will probably be a major change in coming years.
While petroleum-based diesel fuel will remain the bulk of the supply in the U.S., equipment makers say increasing use of biodiesel will make a difference on the farm because of its renewable nature and agronomic base.
Glenn Farris, AGCO's market manager for biomass interests, says renewable sources like soybean and corn oils are the basis for 2 billion gallons of diesel fuel today. Soon, three projects (by DuPont and International Energy Agency in Iowa, and Abengoa in Kansas) will be making ethanol out of corn stover.
"While we have new sources [of diesel] coming on line, the path of least resistance likely will be the use of the fuel and engine infrastructure that does not have to be modified," he explained. "Biodiesel is interchangeable with petroleum diesel, so it's compatible with existing engines. The only technological tweak necessary is to make certain it works with Tier 4 catalytic devices and regeneration cycles," Farris explained.
Additionally, biodiesel answers one of the unintended consequences of the EPA's mandate to remove sulfur from the nation's diesel fuel supply -- a lack of lubricity. Sulfur is a natural lubricant in diesel fuel. But engine fuel systems and valve-train components suffered when federal mandates limited sulfur levels to 15 parts per million in ultralow-sulfur diesel. That required engine redesign and improvements in crankcase lubricants. Biodiesel at mixtures as low as 1% with petroleum diesel can add the lubricity needed for adequate engine protection.
Factor in biodiesel's 3.2:1 favorable energy balance (including farming, fertilizer and processing requirements), and it's easy to see that its future is bright.
ENGINE EFFICIENCY
Diesel engines have always held an edge over their spark-ignited counterparts in the ability to wring power out of "liquid BTUs," partially because of the heat of their ignition process and partially because of the higher energy content of diesel fuel. While makers of both types of engines recently have made great strides in fuel efficiency, giant steps in additional efficiency will require some changes to the traditional tractor or combine engine and drive line.
In 2007, John Deere introduced a research tractor model at Agritechnica, Germany's global farm equipment show. The E Premium machine was powered with a diesel engine but produced an abundance of electricity using an efficient engine flywheel-mounted generator rather than a traditional belt-driven alternator. That electricity powered the tractor's coolant pump, compressors, fuel pumps and possible electric implements. In 2011, Deere introduced an updated version of its research hybrid, the 6210 RE. At the 2013 Agritechnica, Fendt unveiled a research hybrid of its own, the X Concept.
AGCO's Antti Marttinen, product manager Global Engine Installation, says farmers will see more of the diesel-electric model in the long-term
"Short-term, emission technology and related efficiencies [for straight diesel machines] are to be expected," he explained. "Long-term, however, diesel-electric designs will add efficiency by reducing waste heat in engine operation.
NO MORE HYDRAULICS
"Right now, a diesel engine can convert about 40% to 50% of a fuel's energy content to useful work," he says. "Then, that [lost] power begins being absorbed by transmissions, hydraulic systems and the parasitic drag of engine accessories. The diesel-electric model would save many of those losses by eliminating power-robbing engine accessory drives and today's cumbersome and power-consuming hydraulic systems.
"Imagine running electrical lines from a tractor to a mower instead of hydraulic lines. The mower can be designed to be lighter and more compact, there are no hydraulic lines and motors involved, and the fuel efficiency of the diesel engine driving everything has been improved."
Marttinen says his company has experimented with a diesel-electric RoGator sprayer -- each wheel had its own electric motor -- and found significant fuel economy improvements. In that case, however, he says the technology for immediate mass production was "too expensive." As fuel costs climb and technology improves, however, Marttinen says such machines are a distinct possibility. "The technology exists," he added.
Fuels of the Future
There are a number of fuels available for heavy-duty engines, and most have been used in engine test labs and, in some cases, practical application.
Here's a review of what's out there and why they probably won't power your farm equipment soon:
HYDROGEN: While hydrogen burns cleanly and is readily abundant, it has properties that so far have made it highly problematic for heavy-duty equipment or over-the-road applications. It can be used in an internal combustion engine and is a prime fuel in fuel-cell technology -- which has yet to produce power in economically feasible amounts for practical heavy-duty power requirements. As an internal combustion engine fuel, hydrogen must be compressed; but with current technology, a hydrogen tank the size of a 100-gallon diesel fuel tank on an 18-wheeler would provide enough fuel for only a 100-mile trip.
New Holland is currently testing a hydrogen fuel cell tractor on its research farm in Italy.
NATURAL GAS: While the supply of natural gas has increased significantly with the advent of modern petroleum exploration and production practices, its use as either a compressed product (CNG) or a super-cold liquefied fuel (LNG) presents Storage problems. CNG must be stored on a vehicle in high-pressure tanks at between 3,000 and 4,500 pounds per square inch (psi). LNG is a low-pressure fuel but must be stored on the vehicle in liquid form at about 230 psi and at extremely cold temperatures. Both clean-burning fuels have been successfully used in specialized vehicles, particularly CNG for intercity transport buses (Cummins Westport NG engines) and LNG for over-the-road trucking in specialized trucks operating in special corridors equipped with LNG fueling stations. The downside of natural gas and diesel technology is they require a certain amount of diesel fuel to begin the ignition process -- mandating an engine with two fuel systems.
LIQUEFIED PETROLEUM GAS: Liquefied petroleum gas (commonly known as "propane") is a clean-burning fuel that can power tractors, trucks and other heavy-duty equipment, but it has several disadvantages. It is heavier than diesel fuel on a per-energy basis, it has less energy per unit than diesel fuel and it must be compressed for storage. Propane is a byproduct of the petroleum-refining process, so its price is tied to other petroleum products. And, like natural gas, propane requires an electronic or pilot ignition system to work in compression-ignited engines.
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