Diesel engine technology is more efficient than ever before, yet even the most advanced engines currently achieve fuel efficiency of not more than 42%; the rest is lost to a combination of factors, including friction losses, tyre rolling resistance, air drag and significantly, waste heat.
Technologies being employed to recover lost energy include reduced engine idling and start-stop systems, the recovery of kinetic energy through regenerative braking, and waste heat recovery (WHR).
A viable engine WHR system must be not only affordable and durable, but also compact. According to an SAE International technical paper, an ideal application for WHR is on trucks with high mileage and large payloads – indeed, the technology works at its best on engines with high load factors.
One of the forms of waste heat recovery is turbocompounding, which directs the exhaust leaving the turbocharger through a second auxiliary turbine.
Another is based on the Rankine cycle. This comprises a closed-loop system that captures exhaust heat and runs it through a heat exchanger that converts a liquid into a super-heated and pressurised gas. The gas is fed through an expander turbine, whose output can again be harnessed either mechanically or electrically, before being turned back into a liquid in a refrigeration-like heat-exchanging condenser. Most Rankine systems use ethanol as the working fluid.
Norgren is one such company working on commercial vehicle waste heat recovery. The motion and fluid control technologies specialist designs WHR system valves, and views circulation control as essential to WHR success. Mark Sealy, the company’s Engineering Director – Commercial Vehicle Sector, believes that recovering heat is the single biggest opportunity to save fuel and reduce carbon dioxide emissions.
“You can do many, many things with engines and vehicles to improve fuel efficiency, but if you want to make a step change you have to get at the wasted heat. The reason for this is clear – over half of the fuel’s energy is lost as heat. So it’s a very, very significant opportunity,” says Sealy. “Already we have seen a saving of 4% on trucks under real-life road conditions. We have seen as high as 6% fuel savings on engines that run at steady high load.”
These conditions are usually seen in long-distance, heavy-duty trucks, and this is also the segment where fuel costs are operationally most significant. According to Norgren, the business case for WHR still needs to be developed due to a combination of factors. These include technical complexity, the high level of integration needed across truck systems, and the complexities of containing the working fluid (ethanol), within the CV environment.
According to the supplier, bespoke valves are now being designed to improve system viability and improve the controllability of the working fluid. This is primarily to enable energy recovery from more points of the operating envelope. Bespoke designs also help address containment, size and cost considerations.
WHR is designed to reduce emissions and improve fuel efficiency, so the tightening emissions norms in the EU and North America have played an important role for Norgren’s CV business over the last decade.
With Euro VI now firmly in place in Europe, and stringent emissions norms in the US, what does Sealy envisage as the next major step for the CV industry in those markets? “I think we will see cost reduction, and further optimisation. The OEMs will try to reduce complexity, and I think we will see some of them try to remove EGR (exhaust gas recirculation) with improvements in after-treatments. But we do not expect significant new activities on emissions. There is the possibility of a further NOx reduction, but I think it unlikely.”
Alternate fuels are being considered in the commercial vehicle segment as well, which opens up possibilities for hybrids, electric and hydrogen fuel cell-powered trucks. Norgren does feature here as well, producing coolant valves that play a role in managing battery temperature, as well as hydrogen valves and other equipment like air valves and cooling valves for hydrogen fuel cells. However, the company feels that these technologies will be limited to range extenders on fleet vehicles, such as delivery trucks.
“Conventional diesel is still number one. Hybrids will take a long time to become serious because they are just too expensive. Fuel cells will only ever be niche. So the next big thing is natural gas. We see a lot of activity in China and America, and a lot of interest in Europe but not much activity yet,” Sealy says.
“For example, all of the government contracts for city buses in China are LNG (liquefied natural gas) now, already. And our prediction is that one commercial vehicle in three in China, one commercial vehicle in five in America, and one commercial vehicle in ten in Europe, will be natural gas by 2020.”
The company’s focus is currently turning to the less mature markets of Brazil, India, China and Russia, where the contrast with the high emissions norms in the West is notable. Here, there has not been much emphasis on emissions standards, or rather, the adoption of new standards has been on far more relaxed.
Of course, when talking about the BRIC countries, it is important to remember that these are price sensitive markets. They may lag behind Europe when it comes to the ability to reduce emissions, but Norgren expects manufacturers to focus both on targeting European levels of quality, and on the need to meet legal requirements.
“Because it’s a legal requirement, it is a different priority. So, certainly for the next cycle they are prepared to pay for European technology. But we are fully aware that we need to simplify, localise and reduce costs for the future,” Sealy tells Megatrends.
Simplifying and localising may be Norgren’s strategy for developing markets, but there are certain key megatrends shaping the global commercial vehicle industry at large. Sealy cites three in particular that are shaping the supplier’s global strategy. One is the increasingly demanding emissions targets for off-highway vehicles, which have led to the company diversifying into this segment. Another is the implementation of new legal imperatives in Europe and North America for CO2 reduction, which underpin Norgren’s strategy, primarily in WHR, but also in other technologies such as tyre inflation and management technology, and wastegate control.
A third megatrend cited by Sealy is the BRIC countries’ focus on emissions. This may be gaining traction much later than in mature markets, but real change is coming, says Sealy, starting with China. Even in India, where the introduction of higher standards has been delayed owing to various complications including fuel quality, Sealy believes that an emphasis on emissions reductions will come, and that it is a question of when, and not if.
