7 Future fuels;Availability of alternative fuels remains a challenge: Volvo Group
September 1, 2008
WASHINGTON, D. C. - Volvo Group stole the show at the Washington International Renewable Energy Conference (WIREC) held here this spring. The company dominated the trade show floor, with a massive dis...
READY AND WILLING: Volvo has already developed the trucks, now it needs the fuel to provide CO2-neutral transport options, the company claims.
WASHINGTON, D. C. –Volvo Group stole the show at the Washington International Renewable Energy Conference (WIREC) held here this spring. The company dominated the trade show floor, with a massive display that took up one entire wall. The highlight of the exhibit was the unveiling of seven alternative fuel-powered trucks that are completely carbon-neutral and adapted for use in North America.
The exhibit garnered the attention of US president George W. Bush, who took time to tour the display and speak with Volvo executives about their pursuit of carbon-neutral transport solutions.
Truck News first reported on the seven alternative fuels being pursued by Volvo Group from Brussels, Belgium last September (see the November, 2007 issues of Truck News or Truck West for the full report. Archives can be viewed online at www.
But unlike the trucks first displayed in Belgium, the trucks showcased at the WIREC show were adapted for North American use. Volvo officials were also able to delve more deeply into each of the alternative fuels, highlighting the pros and cons of each. The fuels showcased by Volvo Group were evaluated based on a set of seven criteria: climate impact; energy efficiency; land use efficiency; fuel potential; vehicle adaptation; fuel cost; and fuel infrastructure.
Synthetic diesel can be used today with no vehicle adaptation required, said Anthony Greszler, vice-president, advanced engineering with Volvo Powertrain North America. It can be used on its own or blended with traditional diesel.
Synthetic diesel meets existing fuel standards, with the exception of lubricity requirements which are inferior to those of regular diesel. Greszler said this can be easily corrected by using lubricity additives. The challenge will be to get the cost of synthetic diesel production in line with that of traditional diesel, Greszler noted.
On the plus side, synthetic diesel produces very little CO2, offers improved performance over today’s diesel (including an operating range that’s equal to that of regular diesel) and there is no need for vehicle adaptation.
The use of biodiesel is already prevalent in the trucking industry today. Greg Shank, co-ordinator lubricants, fuels and coolants technology with Volvo Powertrain said one of its greatest challenges is the use of a wide variety of feedstocks during biodiesel production.
“All those different feedstocks can cause different problems,” said Shank.
Biodiesel also comes with a fuel economy degradation of 5-10%, Shank pointed out. And it has corrosive properties which can eat away at elastomers, causing fuel system problems. There are also some well-documented cold weather operability issues that have plagued early adopters of biodiesel.
Shank also pointed out biodiesel tends to become ineffective after as little as six to nine months in a storage tank. There’s also a popular school of thought that biodiesel increases NOx, a pollutant targeted by the US Environmental Protection Agency.
Having said all that, Shank pointed out that biodiesel is an attractive option because its cost premium can be offset through government incentives in some regions, it’s already available, it boasts an operational range nearly equal to traditional diesel and very little vehicle adaptation is required.
Ethanol is the most common biofuel used in the world today, explained Greszler, but that doesn’t mean it is without its issues. Ethanol has inherently low cetane levels, which must be offset with the use of additives. It also suffers a lack of energy density compared to traditional diesel.
“Ethanol’s operating range is reduced because it has less energy,” explained Greszler, noting ethanol reduces operating range by as much as 60%.
Ethanol and methanol are also difficult to ignite, so Volvo has added ignition additives as well. Volvo also added catalysts to its ethanol-and methanol-powered trucks to control high concentrations of hydrocarbons and carbon monoxide. Volvo engineers also contend that ethanol and methanol are more corrosive than traditional fuels.
Like each of the fuels being explored by Volvo, methanol and ethanol do have their redeeming qualities. Most notably, the fuels produce very little CO2, particulate matter and NOx. However, when all criteria are evaluated, Shank said methanol and ethanol do not measure up well compared to other options when conducting a complete well-to-wheel analysis. These options score particularly poorly in the land use efficiency category.
Of all the alternative fuels discussed by Volvo officials at a seminar on the subject, it was Dimethylether (DME) that excited them the most. Volvo’s Greszler said “Volvo has been investigating DME for a few years.”
DME is a gas that’s handled in liquid form at low pressure, formed through the gasification of biomass (black liquor generated by the pulp industry is an ideal source). It’s already being used in Asia, but Greszler admitted “Very little is heard about it here.”
As with all other alternative fuels, there are significant sacrifices when using DME, most notably viscosity and lubricity, Greszler explained. He added DME will dissolve some rubber and plastic components. It also offers a greatly-reduced operating range compared to diesel – you’ll only get about 55% as far down the road on a tank of DME compared to diesel.
“However, we do want to say DME is a fuel that can compete head-on with diesel in many areas,” Greszler said. No changes are required to the base engine, but the fuel system must be upgraded with a special fuel pump and injector. And the tanks must be designed to liquid natural gas (LNG) standards.
But Greszler said that performance-wise, DME is equal to or better than today’s diesel. He also noted no diesel particulate filter (DPF) is required and the engines and fuel will eventually cost about the same as today’s.
Other benefits include: high torque at low engine speeds; low CO2 emissions; reduced noise levels; and a simplified exhaust aftertreatment system, sans DPF. While Volvo is excited about the prospect of DME, Greszler admitted “It will take longer to build the infrastructure than it will take us to get the vehicles ready.” In the short-term, it will likely only be suitable for local distribution applications where a truck can be fueled up at one central location.
In addition to liquids, there are also gaseous options available for future CO2-neutral transport, including biogas which can be extracted from sewage treatment plants and landfill sites. Gaseous options boast reduced engine noise and biogas has the added benefit of recycling man-made waste.
Biogas has a low cetane index, Greszler explained, meaning ignition must be triggered via a spark plug or a diesel pilot injection system. Unfortunately, biogas (and hydrogen for that matter) have low energy content. If used in a compressed gas state, the fuel suffers from a reduced operating range. When used in liquid form, it has the tendency to evaporate.
Biogas + Biodiesel
Biogas may have too many challenges to overcome on its own, but it can also be used in conjunction with biodiesel, according to Volvo officials. In this case, the two fuels are housed in separate tanks. A small percentage of biodiesel (10%) is used to achieve compression ignition.
Biogas options eliminate the need for a DPF and they offer good throttle response and low exhaust emissions, Greszler pointed out.
Hydrogen + Biogas
Biogas can also be mixed with hydrogen. In Volvo’s case, an 8% mixture of hydrogen is used. Pros include very low well-to-wheel CO2 emissions, the elimination of particulates and smoke, good throttle response and as with other gaseous options, reduced engine noise. This option is well-suited for urban applications, Greszler said.
As witnessed at WIREC, there are
many options available to the trucking industry to achieve CO2-neutral transport. Volvo has proceeded with developing trucks that can utilize each of the seven most promising alternatives, despite the fact there is currently no widespread availability of most of these fuels.
“Availability is crucial. That’s certainly going to be limited for a number of years,” Greszler admitted. “But we see a lot of potential for second generation biofuels.”
In the short-term, Volvo officials said the most logical approach is to blend emerging alternative fuels with traditional fossil fuels.
“We can do that immediately and gain some immediate benefits,” Greszler said.