There was a time when all of the talk of an alternative to the internal combustion engine (ICE) centred around battery-powered vehicles, whether it be cars or trucks.
Yet, after several years of attempting to make electric vehicles work as well as those that they are intended to replace, there is a growing awareness that managing energy in the form of electricity cannot meet the demands of modern machinery as well other fuels can.
The promise of better batteries with greater capacity and less weight has failed to materialise, so the field is being left to lithium ion batteries, and all of the problems now being associated with them.
Little surprise then, that attention is turning to alternative fuels to run ICE vehicles on, rather than replacing the entire engine.
Following this route has the huge advantage of retaining all of the drivetrain and engine components if the fuel is a straight drop-in replacement for diesel, yet there is some uncertainty as to whether fuels such as hydrotreated vegetable oil (HVO), will become available in sufficient quantities.
Hydrogen emerges as frontrunner
Hydrogen is another fuel that is being increasingly talked about, and two companies in particular were highlighting their latest engines at LAMMA, which are configured to run on the gas.
The manufacturers concerned were JCB, which has been enthusiastically promoting hydrogen for a while now, and Kubota, a company that sells its engines to many other OEMs, and is therefore taking a broader and more modest approach to alternative fuels.
Both companies have taken a similar approach to the use of hydrogen, in that they have adopted existing engines rather than build anew.
The bottom ends have stayed the same, although the top piston rings on the the JCB motors have been changed.
Most of the work has been done in adapting the induction manifold, placing spark plugs in the head and getting it all to work together.
JCB is quick to point out that one reason hydrogen has taken so long to be adopted, is because the first attempts to convert big gas guzzlers in America simply fed it through a carburettor.
Technology to the rescue
Both this company and Kubota have used modern timing and injection technology to introduce hydrogen into the airstream just as it enters the cylinder, in a method known as porting.
This is claimed to ensure a perfect mix of air and gas on the induction stroke, enabling rapid combustion at the appropriate moment – a moment that necessitates the use of a spark plug rather than relying on compression to ignite the fuel.
What neither company is willing to talk about too much at present is the actual operating parameters of their respective engines.
JCB tells us that the engine’s running temperature is reduced, thus avoiding the creation of N oxides (NOx), but the exact compression ratio is not divulged.
No NOx
This elimination of NOx emissions obviates the need for any exhaust gas treatment, therefore, the engines come at a lower unit cost, are lighter, and need less space.
Meanwhile, Kubota is now happy to talk about the specific power output of its unit, which is 114hp, first announced at Conexpo 2023 in March last year.
It is a 3.8L unit that has been adapted to run on several alternative fuels, giving the company a degree of flexibility that is essential to a supplier of engines to a large number of OEM companies, each facing different legislation and fuel availability in various parts of the world
Yet, there is still a reliance on selective catalytic reduction (SCR) as an exhaust treatment, indicating that Kubota has not made any great alteration to the engine’s combustion characteristics.
Adapting to hydrogen
The hydrogen adaptation is further variant of the WG series of engines, with the WG3800 being the largest of them.
It was developed in conjunction with Denyo, a leading genset company in Japan.
Being stationary, gensets are an ideal application for hydrogen, as it is a notoriously difficult gas to store and feed to an engine.
Being the smallest molecule, it can find its way past many seals and through standard pipe unions.
However, according to Daniel Grant, division manager for Kubota engines in Europe, fuel systems are now robust enough for tractor and construction vehicles, although the infrastructure for production and distribution has yet to be put into place.
The retained parts, such as the block, are painted green on the JCB unit
A major criticism of hydrogen combustion engines is that they are a lot less efficient than hydrogen fuel cells, which do not share the same thermal energy losses.
So, it might be asked, why has Kubota and JCB, amongst others, gone ahead down the combustion route? The simple answer is cost.
Those that back fuel cells tend to overlook the expense of what they propose.
Fuel cells are expensive to manufacture due to the platinum catalyst vital to their function, and that catalyst will need replacing throughout the life of the cell.
EVs with tanks
Vehicles that run on fuel cells are basically electric vehicles with hydrogen tanks rather than batteries.
They will have a novel powertrain, which will need a new servicing infrastructure, something that will not be cheap to implement.
Hydrogen ICE vehicles will retain much of what is already familiar to service personnel, with just extra training on the fuel system required, an expense that will be more easily absorbed.
It is for these reasons that hydrogen combustion is now seen as an alternative, rather than fuel cells, but that may change if cheaper catalysts are developed, an area of ongoing research.
Both JCB and Kubota are taking this alternative forward with enthusiasm, for neither believe that batteries are the whole answer to reducing our dependency upon fossil fuels – a sentiment that is now prevalent throughout the tractor and machinery industry.
Other companies working on the hydrogen engine include TAFE which was showing a 55hp tractor at Agritechnica, although no details were given, while Cummins is working on larger engines, one of which is already developing 290hp.
