Could natural gas be answer to a clean diesel alternative?
Australia is slow picking up on LNG engine tech
LIKE the greedy farmer Brown from back in medieval times – the bloke who sold his crops for profit but had nothing left to feed his family through the winter – it appears that Australia has committed the bulk of its huge natural gas extraction to overseas markets, leaving inadequate supplies for domestic use. A case of corporate farmer Brown greed.
This seems something of a tragedy when one of the more viable alternative fuels for heavy truck use in the future is natural gas. Many millions of euros and greenbacks have been invested in the natural gas engine technology by truck manufacturers.
In spite of the Turnbull Government’s attempt to stem the rivers of natural gas flowing overseas, the extraction and processing industry is addicted to profit, with 37 million tonnes of LNG exported, worth $16.55 billion, in the 2015-16 financial year
Most of Australian gas goes to Japan, China and South Korea, and gas exporters are busily building increasing markets in Taiwan and India.
And, hard to believe, in 2016 AGL announced the likelihood of spending $300 million to build a gas import facility – talk about coal to Newcastle.
The possibility of importing gas to one of the most gas-rich countries in the world.
Much has been written of electric-powered trucks in recent times, with fast-evolving battery technology. However, all major truck manufacturers have already dipped their toes in the sea of potential they claim for natural-gaspowered engines.
Just about all major truck manufacturers have developed trucks to meet Euro VI emission standards using diesel. However, even cleaner internal combustion engines can be engineered to run on gas.
To date, most of the truck applications for natural gas engines are in the construction, refuse and agitator markets, mostly because fuel storage requirements limit the range of heavy trucks to 1000km or less.
Even to get this range, liquid petroleum gas (LPG) must be used and this must be kept at temperatures below -100 degrees Celsius, requiring complex and heavy thermos-styled fuel tanks.
An option is to use compressed natural gas (CNG), and this requires a tank engineered to hold gas at extremely high pressure, 3000–3600psi (remember a truck tyre runs at about 90psi). The CNG tank is bigger and more costly than a conventional fuel tank and the range for heavy trucks is limited to a few hundred kilometres.
Natural gas is extracted from deep underground, in Australia mostly from desert gas fields and off-shore facilities.
While CNG and LNG are both the same extractive energy source, storage methods differ.
Liquid petroleum gas (LPG) is a different chemical, also called propane, and is used in many vehicles today and has a different composition, coming from petroleum processing.
A natural-gas-powered vehicle obtains its energy through the combustion of what is essentially methane gas and, like diesel, it produces carbon dioxide and water vapour through the internal combustion process.
Natural gas, however, has fewer particulates than diesel and claims to be the cleanest burning hydrocarbon.
LNG and CNG are both considered as viable fuels for vehicles.
CNG, as well as giving more challenges with on-truck fuel storage, requires large investment with refuelling equipment, pumps, tanks, and increased hazards.
LNG is refrigerated to its liquid state and is more than two times as dense as CNG. It can be dispensed from bulk storage tanks and is stored in specially designed insulated tanks that operate at comparatively low pressures on the vehicle.
Use in heavy trucks
China has been a leader in the use of LNG vehicles, with hundreds of thousands of trucks operating today.
In North America the parcel delivery company UPS has a large number of LNG-powered trucks on the road, making an increasing percentage of the company’s 16,000 prime mover fleet.
Europe was slower to pick up LNG as a fuel, possibly because of the difficulty in acquiring the gas, but in the past couple of years has embraced the gas technology.
Cummins launched the Westport ISX12G for heavy trucks back in 2013, based on the ISX12 diesel engine, and it is becoming available in the trucks of the Indiana company’s OEM partners in the US.
The ISX12G can use either LNG or CNG and uses a combustion technology that differs to a traditional diesel burn, using a stoichiometric cooled exhaust gas recirculation (SEGR) combustion technology and a three-way catalyst (TWC).
SEGR combustion uses spark ignition, taking a measured quantity of exhaust gas and passing it through a cooler to reduce temperatures before mixing
Even cleaner internal combustion engines can be engineered to run on gas.
it with fuel and the incoming air charge to the cylinder.
The ISX12 G requires no active after-treatment such as a diesel particulate filter (DPF) or selective catalytic reduction (SCR).
The 12-litre gas engine is available in horsepower ratings from 320–400hp with 1966Nm of torque.
Cummins says the ISX12 G is a dedicated factory-built natural gas engine, but it shares many of the same components as its diesel sibling and operates on 100% clean-burning, low-cost natural gas. Cummins is recommending the gas engine for trucks used in the mixer, dump truck and refuse applications.
Scania launched a natural-gas-powered Euro VI truck in 2014 and is claiming many environmental advantages and lower fuel costs, saying reduced running costs will more than outweigh the higher purchase price in many applications.
In the Scania LNG trucks, the gas is stored on board at -132 degrees Celsius, held in a highly insulated tank surrounded by a vacuum, the whole thing inside another insulating layer – a big thermos tank.
Just last month, Volvo has launched two LNG-powered models, claiming the new trucks have the same performance, drivability and fuel consumption as the equivalent diesel-powered models, with reduced emissions in the range of 20–100 per cent.
The new models are the Volvo FH LNG and the FM LNG, available in 420 or 460hp versions for heavy regional and long-haul operations.
The Volvo LNG tanks can store fuel in a temperature range of -40 to -125 degrees Celsius, with the largest fuel tank giving a range of up to 1000km, similar to Scania.
Volvo says refuelling will take about the same time as filling with diesel.
In the Volvo system, fuel is warmed as it is pumped out of the tank and converted to a gas before it is injected into the engine with a tiny squirt of diesel to aid ignition.
The Volvo G13C engine is a Euro VI in-line six cylinder, 13-litre common rail engine with injector nozzles for gas and diesel.
It is available with an output of 420hp/2100Nm of torque or 460hp/2300Nm of torque.
A range of 1000km requires the 495-litre fuel tank.
Differing from the Scania version, a SCR emissions management system and particulate filter are required to maintain Euro VI compliance.
So natural-gas-powered engines are available today, with the advantages of reduced running costs, less internal corrosion and significantly reduced emissions.
Are we, in gas-rich Australia, likely to see them in any numbers here?
Don’t hold your breath.
COOL DOWN: LNG is carried at below -100 degrees Celsius and requires heavily insulated on-truck fuel tanks.
The Volvo LNG engine uses a minuscule injection of diesel to aid combustion and requires a small diesel tank as well as the LNG storage.
Scania launched natural gas powered trucks in Europe in 2014.
POSSIBILITY IS THERE: The Cummins Westport ISX12 G on show in the US.