Freight must reduce its emissions by 80% to 2050 whilst growing volumes by 230%. Many of the solutions are known and follow the Avoid Shift Improve (ASI) model, but the originators [Schipper and Marie (1999)] had a fourth letter F for Fuel (ASIF). So today’s webinar looks at the options by starting with the basics.
Link to webinar: https://aems.clickmeeting.com/ff
Combustion and conversion losses
As the controversy over diesel NOx emissions showed, all tests can be gamed, so how do we know which source of motive power is most efficient? Well we can make some basic assumptions:
- The higher the compression ratio and temperature the more heat / work we will get out of a given amount of fuel.
- Electric is generally more efficient than internal combustion because you lose so much energy to heat in combustion
- Thus electric is 90-95% efficiency, petrol 20% with some exceptions such as GDI at up to 40%, diesel ranges from 30-50% and turbines up to 50+%.
Your mileage will vary, every application is different, you wouldn’t use diesel inside your house and you are unlikely (yet) to use an electric powered aircraft (but they are on the way).
Useful work: torque vs power
In freight what we want is pulling power, the more weight we can move in one go the better. Electric motors offer more torque from zero revs with an overall efficiency of 85% compared to Internal Combustion Engine (ICE) at best of 40% (probably more like 20% in reality).
A complex process, so lets simplify it (with apologies to my physics teacher, masters lecturers and fuel chemists everywhere)
- How to compare? Need a common unit = kWh
- Cost for useful work would be Price/kWh ÷ conversion/combustion efficiency
- Or for diesel at €1.33/Litre ÷ 10.169kWh/L = 13c/kWh ÷ .30 = 43c/kWh of work
- Electricity can cost more per kWh than diesel e.g. 19c/kWh ÷ .90 = 21c/kWh of work
As we say in the webinar, you need to be sure whichever fuel you choose is available, cost effective, clean or green? Choose one aspect, there’s no one perfect fuel (yet).
1.What do you want to do? No magic wand – pick one:
- Lowest cost – most profitable
- City access (cleanest & quietest)
- Greenest (lowest CO2)
2.Is the fuel available where and when you need it?
3.Are there any grants or tax breaks?
- For the vehicle
- For the infrastructure
- For the fuel – how long will tax break last?
4.Is there a first mover advantage / customer contract?
5.Is the fuel or its infrastructure subject to regulator approval?
You also need to consider maturity of the fuel, its infrastructure and vehicle availability.
A good article from Prof David Cebon at SRF In Cambridge on the Hydrogen vs Battery Electric for trucks debate: http://www.csrf.ac.uk/2020/02/blog-long-haul-lorries-powered-by-hydrogen-or-electricity/