It’s not rare to see a tank of anhydrous ammonia (NH3) in a farmyard. But it would be to see a farmer fuelling up a tractor from it. Even though it’s a well-known source of fertilizer, few realize it is also a potential engine fuel. And as off the wall as that might seem to some, it’s far from a new idea.
NH3’s history as a fuel source dates back a long way. In 1935 a patent was issued for a system that burned ammonia and hydrogen in a regular internal combustion engine. During World War II, people in Belgium burned it mixed with coal gas as a substitute for diesel fuel, and in the 1960s, NASA’s experimental X-15 rocket planes used it, along with liquid oxygen, as a propellant.
Recently, the Saskatchewan Research Council (SRC) has experimented with NH3 use in diesel engines. “It has some real benefits over hydrogen. It can be stored inexpensively and more densely.” says Sheldon Hill, manager for the Alternative Energy Development Business Unit at the SRC.
The SRC’s research looked at using NH3 in a dual-fuel diesel engine. “We did some engine testing using anhydrous ammonia and diesel in an Isuzu Duramax direct-injection diesel engine with common-rail injection,” says Hill. “This engine is commonly used in General Motors diesel-powered pickup trucks. Anhydrous ammonia was successfully used to displace over 50 per cent of the diesel used at various loads.”
At higher concentrations, though, it conflicted with the engine’s electronic control system and the engine lost efficiency, suffering from incomplete combustion in the cylinders. But the SRC’s program did not continue to look at ways that problem might be overcome. “We were limited on budget, so we couldn’t do a full evaluation,” notes Hill. However, the SRC is only one of many groups turning their attention to NH3. “There is a lot of interest developing in the use of NH3 as a fuel,” he adds.
The Iowa Energy Center (IEC), at the University of Iowa, has conducted research using an older model John Deere tractor converted to run on 95 per cent NH3 and five per cent biodiesel. The diesel component is required to ignite the NH3 in the cylinders.
“What we were trying to find out is how much ammonia in terms of energy per cent can we put into an unmodified diesel engine,” says Norman Olson, Beacon Facility director at the IEC. “What we found out is we can run 95 per cent ammonia and run it (the engine) at 110 per cent load.” That highlights the suitability of ammonia fuel as a potential fuel.
And while the experiment didn’t look at further minimizing exhaust emissions, Olson doesn’t think that will be a problem. “Emissions issues are going to be very easy to take care of,” he adds. “Obviously we’re going to have very low carbon emissions and almost no particulates. There’ll be a little NOx or residual ammonia, but a low-cost catalytic converter takes care of those.”
While the experimental John Deere is still operating at the University’s farm, the IEC is now working with a newer direct injection diesel engine. It’s experiencing some of the same difficulties the SRC encountered with its Duramax tests. “That one is proving to be a little more difficult to run, but we’ll get there” says Olson. “(So far) the older design works better.”
According to information published by the Ammonia Fuel Network website, converting a regular gasoline engine to run on an NH3-gasoline mixture only requires a conversion kit similar to what is required to use other compressed gases. Although none are yet commercially available, a U.S.-based company, Icom, which makes propane conversion kits, expects to introduce one soon.
“We’re in development for a specific large gasoline engine,” says Albert Venezio, Icom’s chairman. “In February, we’ll take everything we learn there and apply it to another engine. It’s a bit of a process the first time you do an engine (type).” After fine tuning the overall design, a conversion kit can then be modified to fit other similar engines.
By mid-2011, the company expects to be able to offer con- version kits for selected engines through its established dealer network in Canada. Initially the kits will be for a dual-fuel set up, but the company expects to release a mono-fuel ammonia kit later. Venezio adds that the company will focus much of its initial efforts on farm and industrial equipment, and the kits will be intended for fuel-injected rather than carbureted engines.
Olson says people involved in researching ammonia as a fuel consider it “the other hydrogen,” because it offers most of that fuel’s advantages with few of its limitations. And he believes NH3 could be more easily adopted.
Among those advantages are efficient and simple fuel storage, something hydrogen researchers have been trying to develop for their fuel for some time. NH3 also contains 50 per cent more energy per gallon than hydrogen. But despite that, NH3 still has only 52 per cent as much energy as gasoline. “There is currently nothing that approaches the energy density of fossil fuels,” comments Hill.
And just like hydrogen, NH3 can be used to power some fuel cells that generate electricity. But the biggest advantage may be that commercial NH3 storage and distribution systems currently exist to handle the fertilizer market, and they could service a rural NH3 refuelling network. So far, hydrogen distribution systems are limited at best.
Most NH3 is now produced from natural gas. That ties its cost to the fluctuating price of energy. Even at that, its cost per BTU has consistently remained slightly lower than gasoline according to the IEC’s findings. But there are many other ways to create it. It can be refined from biomass material, Including cellulose using commercially-available technology. “We can produce more BTUs per acre of ammonia than ethanol,” notes Olson.
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