Energy density and the challenges of electrification for heavy duty vehicles
Feb 13, 2019
The topic of electrification for truck and buses comes up more and more frequently when we talk with people interested in the EV supply chain; while the prospects for battery powered passenger cars and light duty vehicles are by now fairly clear, we see a more nuanced story for larger vehicle classes. In this spotlight we examine the key issues and practical applications for electrification within the heavy and medium duty space.
We have recently teamed up with heavy duty and non-road powertrain experts KGP to launch our new EV Energy Density Monthly Assessment. This publication tracks the development of battery pack sizes across vehicle classes and for the industry as a whole and this spotlight draws on this research. If you would like to learn more about the assessment register your interest here and we will be in touch to discuss.
The push towards electrification of heavy duty vehicles is essentially driven by three factors. The first is the long-standing trend in the commercial vehicle and haulage industry towards greater efficiency and lower total cost of ownership. Commercial vehicles are operated as business assets that are expected to generate a return, with fuel a major cost input.
The second factor is the pressure from legislators for emissions control, both in terms of carbon-reduction and fuel efficiency, but more importantly to improve ambient air quality standards particularly in urban areas. The third arises from the corporate social responsibility concerns of major fleets and operators, with a desire to act, and be seen to act, in an environmentally ethical manner.
As such there is a sizeable opportunity for an economically viable solution for the electrification of commercial vehicles, but also major obstacles to overcome. The key challenge, as ever, is range. Heavier vehicles require greater power, and exponentially so if they are pulling significant payloads. As such the kWh requirement per Km for heavy duty trucks and buses is around 1.1-1.3 kWh/Km depending on the type of vehicle, and for medium duty 1.0 kWh/Km or less. Compared to 0.2 kWh/km and less for passenger cars and light duty vehicles.
For heavy duty this equates to a battery size of around 800-1,000kWh to deliver 800 km (500 miles) of range. Even at battery prices approaching USD100 per kWh this represents a huge cost for the vehicle. Equally important are weight and space considerations, at current energy densities the battery weight to achieve this range would be in the region of 5,000-6,000 kg, equivalent to a payload loss of 5-10% depending on the truck compared to diesel. In addition charging times would be in the order of several hours using current fast charging technology.
The fact remains that the incumbent technology, the diesel engine, provides significantly greater energy density than lithium-ion at present. For example, a 1,000 litre diesel fuel tank weighing 800 kg would deliver the same energy as a current 20,000 kg lithium-ion battery. Further, the major successes for electrification in larger vehicle classes seen to date, urban buses operating on a closed route with batteries of around 300 kWh, have largely been driven by subsidies and non-economic factors.
Despite this there is still a strong case for electrification for medium and heavy duty commercial vehicles. Trucks with ranges of 150-300 km, with batteries in the order of 100-200 kWh, are likely to play an increasing role in urban areas where air quality concerns are higher, and therefore emissions restrictions are most stringent. This will primarily be for ‘last mile’ delivery, and for vocational vehicles that operate on a local route and return to a depot for re-charging on a regular basis. In the meantime work continues to increase energy density and range for heavier vehicles, with 500 kWh a seemingly realistic target over the coming 3-5 years.