On the 17th May 2018, the European Commission presented legislation for the first ever mandatory reductions in CO2 emissions from trucks, coaches, and buses, FMT emission performance standards for new heavy-duty vehicles. The legislation sets out a 2 step target, requiring a reduction of 15% by 2025 and 30% by 2030. Emissions will be modelled using the VECTO tool and applied on a fleet basis. This can be found here [link to external site]. CO2 is a by-product of combustion of fuel, so reducing CO2 emissions also means improving fuel efficiency. Initially, the regulations just apply to heavy trucks 16 Tons and above, but in 2022 will be extended to include lighter trucks of 7.5 Tons and above, buses and coaches.
Manufacturers will also earn super credits for Zero (tailpipe) Emission vehicles i.e. Fuel Cell or Fully Electric that will help them to offset emissions from their other vehicles and can reduce their fleet average by a maximum of 3%. The legislation now provides a level playing field for manufacturers to make investments in technology to improve the efficiency of their trucks, whereas in the past manufacturers have been unwilling to make investments that might make the initial purchase price of the truck higher than another manufacturer who was not making the same investments.
What does this mean in practice, trucks already use highly efficient diesel engines so how can these huge improvements in efficiency be achieved?
Manufacturers will be obliged to invest in technology improve efficiency significantly; failure to deliver the CO2 reductions will result in potentially very large fines. This will mean widespread adoption of technologies such as electrified engine ancillaries to reduce parasitic loses and cost-effective 48V mild hybrids. It will also lead to increased development of more full hybrid vehicles and zero emission offerings.
Despite using a highly efficient engine, there are some simple low hanging fruits in a typical commercial vehicle powertrain when looking for ways to improve efficiency, the truck powertrain has a number of key engine driven parasitic loads:
- Engine thermal management and HVAC system which includes large fans and pumps
- Power assisted steering pump
- Air compressor that provides compressed air for the brakes and suspension
Because these systems are driven directly by the engine they are difficult to accurately control as their operating speed is linked to the engine speed. This can lead to issues such as extended engine warm up, lower than desired engine operating temperatures and increased thermal cycling as the engine temperature bounces around the thermostat opening point. This happens due to engine driven coolant pumps and fans running when not required with no or very poor control. The engine and the ancillary systems are also typically optimised for maximum efficiency and performance at the peak torque/load point. When operating off this point the efficiency of the devices is significantly reduced all driving cycles involve an element of transient operation, even those in long-haul trucking.
There are also significant opportunities for energy recovery under braking through the use of high power smart motor/generator units instead of conventional alternators. In 2016 AVID successfully demonstrated a 48V MHEV delivery truck concept, this vehicle featured a fully electrified ancillary system and a smart motor generator for energy recovery under braking and torque assistance under acceleration. Extensive testing was carried out to fully understand the benefits of electrification of all the vehicle sub-systems. Fuel savings of over 25% were achieved on an extra-urban driving cycle and 28% on an urban driving. These savings were possible due to AVID’s highly efficient electrified ancillaries and smart and integrated system control. AVID estimates that a further 3% could have been gained by implementing engine start/stop on this truck, taking the total fuel saving potential to around 30%. More information on this 48V Hybrid System can be found here. Whilst on a car it would not be even be considered to have a 48V MHEV plugin, on a truck this can bring some great benefits as the shore power supply can be used to pre-condition the engine, all but eliminating the daily morning warm-up regime and also operate the HVAC system to eliminate the need for engine idling.
48V provides much greater utility than the existing truck 24V system, whilst it is possible to electrify some systems at 24V the power requirements of devices such as the steering pump, air compressor, and HVAC is beyond what is practical to deliver on a 24V system as the currents are too high, increasing the voltage to 48V halves the current, leading to more efficient devices, lighter weight components and wiring systems and the possibility to deliver more power to key systems. A 48V system can be run in parallel with the 24V system in exactly the same way 48V systems are run in parallel to 12V systems in the passenger car industry, minimising the vehicle platform engineering costs.
The 48V MHEV technology delivers cost-effective fuel-saving potential in many different mission profiles, however in some cases, it will be necessary to go further to full hybrid systems, with an operating voltage of over 350V, in this case, a high power electrical machine will be used in conjunction with the engine. The AVID EVO motor is an ideal example of a high power electric motor that can be easily integrated into a full hybrid system by inserting it between the engine and transmission due to its short axial length. Having a more powerful hybrid system means more power can be recovered under braking and more torque can be put into the drive-line under acceleration. This will also give the opportunity for some zero emission operation of the truck. Efficient full hybrid systems also need fully electrified ancillary systems, in some cases a 48V electrified ancillary system can be cost-effectively combined with a 400V hybrid system. The 48V ancillaries being lower cost than their HV equivalents but still able to deliver the performance required and offering performance and weight saving benefits compared to 24V components.
The ultimate solutions will also see fully electric heavy-duty trucks with no combustion engine. Using either battery storage if the energy density of the batteries can be improved to the extent required to cover the typical mission profile of the truck or using Fuel Cell systems to generate the electricity and on-board hydrogen storage to improve operating range. Of course, a fully electric truck requires fully electric ancillary systems for powertrain thermal management electric fans, pumps and heating, electrically driven air compressors for brakes and suspension and steering pumps or assistance motors. The higher requirement for traction torque to match that of the diesel engine means the market for very torque dense electric motors is set to grow significantly. Around 2,000 Nm of torque or more is required, which can be delivered to the wheels through a variable speed or fixed ratio gearbox. There are several different concepts ranging from the multi-motor approach, where individual motors are used to drive each wheel (used by both Nikola and Tesla) and the conventional differential and axle are deleted to more conventional single or dual motor approach where the conventional axle is retained and a multi-speed gearbox such as those being developed by Eaton is used. There are pro’s and cons to each approach, but in both cases, the motors must be compact and lightweight so as to not impact further on payload capacity which will already be under pressure by the addition of a large battery pack or fuel cell system. Again Torque dense machines such as the AVID EVO electric motor offer excellent potential for the xEV truck market and open up a variety of packaging options due to their high torque to volume and weight performance.
If you would like to discuss electrification strategy for trucks and other heavy-duty vehicles or the new EU regulations for CO2 reduction in more detail contact AVID today.