Mobility Solutions

Hybrids, natural gas, and heat-recovery systems Alternative powertrains for commercial vehicles How much fuel hybrids and heat recovery will save in the future, and why natural gas is already a viable option

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  • September 23, 2014
  • Mobility Solutions
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press release

Voluntary commitment: The European Automobile Manufacturers' Association (ACEA) has pledged to reduce commercial vehicle fuel consumption by one-fifth from their 2005 levels by 2020. This target is based on improvements to existing technologies, but even higher fuel savings could be achieved through the use of heat-recovery systems and electrification technology in commercial vehicles.

“The electrification of commercial vehicles and heat-recovery systems offer significant savings potential. In terms of price, these technologies will be competitive by the end of the decade,” says Wolf-Henning Scheider, member of the board of management of Robert Bosch GmbH.

Waste-heat recovery can save up to 2,000 liters of diesel each year
Potential savings: Today, some 60 percent of the primary energy used to power commercial vehicles is lost as waste heat. A waste heat recovery (WHR) system can recover some of this energy by means of a steam power cycle. This system reduces fuel consumption by up to 5 percent. Depending on vehicle type and total mileage, a WHR system allows up to 2,000 liters of diesel to be saved per year and vehicle.

How it works: In the steam power cycle, ethanol, the working fluid, is fed into a pump where its pressure is increased, and then into evaporators. These absorb the exhaust waste heat and vaporize the ethanol. The resulting vapor drives the expansion machine before continuing into the condenser, where it is returned to its liquid state, while residual heat dissipates into the environment. The ethanol fluid cycles back into the fluid pump. The mechanical energy gained as a result can be used to drive the crankshaft or a generator.

Integration: The mechanical energy converted by the expansion machine can be used to drive the crankshaft, either directly or via a gear unit. Alternatively, the steam turbine can drive a generator that allocates the available electric energy to battery storage or to the electrical system, or it can be used directly for an electrical component in a hybrid vehicle's powertrain.

Hybridization reduces consumption by up to 15 percent
Potential savings: Heavy commercial vehicles account for up to two-thirds of Germany's road freight traffic CO2 emissions. Hybrid systems could significantly reduce fuel consumption and consequently CO2 emissions. With the Bosch hybrid system, a heavy commercial vehicle used for long-distance hauling could save up to 2,500 liters of diesel fuel per year. The reference cycle is the route Stuttgart-Hamburg-Stuttgart, using a 40-ton truck. Depending on the operating strategy, a reduction in fuel consumption of up to 15 percent is possible for delivery runs. For a conventional 12-ton truck with an average consumption of 20 liters per 100 kilometers which covers 50,000 kilometers per year, this means an annual savings of 1,500 liters of diesel.

Customer benefit: With hybrids, fleet operators profit not only from reduced fuel consumption but also from significantly quieter vehicles. Even the most demanding environmental standards can be more easily satisfied than is possible with conventional diesel engines because exhaust gas and particulate emissions are also much lower. In the urban driving cycle, a hybrid vehicle can start in all-electric mode and also cover short distances with zero emissions. The electric energy can also power peripheral systems.

Modular design: Bosch has developed a parallel hybrid system with 120 kW of power for heavy commercial vehicles. Central components for long-haul transport include the electric motor and power electronics. The space-saving electric drive is integrated into the powertrain between the engine and gearbox, so that no extra transmission is needed. It assists the combustion engine, recuperates energy, enables coasting, and makes electric driving possible. The inverter transforms the direct current stored in the battery into alternating current for the motor, and controls the desired torque and engine speed.

Flexibility: The system's modular design means that the components can cover the needs of a wide market, and be adapted to diverse applications in long-haul and multi-drop delivery traffic, as well as in buses. A start-stop function can also be integrated, opening up further fuel-saving potential, especially in urban delivery traffic.

Combination with WHR: Powertrain concepts for heavy goods vehicles that incorporate waste-heat recovery and hybrid-vehicle technologies represent a promising approach for the future, since both systems have individual strengths that can be utilized at different points in the operating cycle. Whereas in hybrid mode the savings potential is relatively limited on long overland routes with few changes in elevation, the consistently high level of waste heat can be easily recovered. Conversely, hybrid powertrains offer a significant reduction in fuel consumption when traversing mountainous regions or other routes requiring frequent gear changes.

CNG powertrains for commercial vehicles
Monovalent: There is an increasing trend toward the use of monovalent engines that run exclusively on natural gas in commercial vehicles. In these vehicles, natural gas is injected at a pressure of roughly 7 bar into the intake manifold of a converted diesel engine. For the combustion of the air-natural gas mix, the engine is also fitted with spark plugs and ignition coils. CNG-powered commercial vehicles emit up to 20 percent less CO2 than equivalent diesel trucks and very low levels of particulates. Commercial vehicles equipped with CNG engines are also cheaper to run over the engine's service life, enabling operators to achieve potential cost savings of around 50 percent compared with a conventional diesel engine.

DualFuel with diesel and natural gas: For commercial vehicles, Bosch offers a combined natural gas and diesel system that allows up to 90 percent of diesel to be replaced with natural gas. Here, the diesel injection system acts like a kind of liquid spark plug. As it ignites the gas, there is no need for any additional ignition system.

Fleet customers: Compared with conventional diesel engines, DualFuel systems with a natural gas and diesel system emit 15 to 20 percent less CO2 as well as less particulate matter. And given that natural gas is less expensive than diesel fuel, fuel savings up to 50 percent can be achieved during the vehicle's service life. Vehicles with Bosch DualFuel systems can also be run purely on diesel, and are thus suitable for areas with a limited natural gas infrastructure.

Market: Bosch offers a complete range of components for natural gas engines including control units, sensors, and injection valves. Market growth is dependent on the expansion of infrastructures – whether in the United States, with its many CNG service stations along interstate highways, or in China, with its local networks. Natural gas powertrains are already competitively priced.

Click here to find further information

First and foremost, the Bosch stand (Hall 17, Stand B12) at the 65th IAA Commercial Vehicles in Hannover is about efficiency. We are using smart solutions to make conventional commercial-vehicle powertrains not only cleaner, but also increasingly economical. And with technologies for alternative powertrains and fuels, Bosch has the future clearly in its sights. In addition, we show how in-vehicle and internet connectivity can help simplify logistics and make truck use even more efficient.

Mobility Solutions is the largest Bosch Group business sector. In 2015, its sales came to 41.7 billion euros, or 59 percent of total group sales. This makes the Bosch Group one of the leading automotive suppliers. The Mobility Solutions business sector combines the group’s expertise in three mobility domains – automation, electrification, and connectivity – and offers its customers integrated mobility solutions. Its main areas of activity are injection technology and powertrain peripherals for internal-combustion engines, diverse solutions for powertrain electrification, vehicle safety systems, driver-assistance and automated functions, technology for user-friendly infotainment as well as vehicle-to-vehicle and vehicle-to-infrastructure communication, repair-shop concepts, and technology and services for the automotive aftermarket. Bosch is synonymous with important automotive innovations, such as electronic engine management, the ESP anti-skid system, and common-rail diesel technology.

The Bosch Group is a leading global supplier of technology and services. It employs roughly 375,000 associates worldwide (as of December 31, 2015). The company generated sales of 70.6 billion euros in 2015. Its operations are divided into four business sectors: Mobility Solutions, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 440 subsidiaries and regional companies in some 60 countries. Including sales and service partners, Bosch’s global manufacturing and sales network covers some 150 countries. The basis for the company’s future growth is its innovative strength. Bosch employs 55,800 associates in research and development at 118 locations across the globe. The Bosch Group’s strategic objective is to deliver innovations for a connected life. Bosch improves quality of life worldwide with products and services that are innovative and spark enthusiasm. In short, Bosch creates technology that is “Invented for life.”

Further information is available online at and,

PI8640 - September 23, 2014

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