Heavy-duty trucks such as 18-wheelers are virtually all powered by diesel engines. They account for a significant portion of worldwide greenhouse gas emissions but little has been done to curb their climate-change-inducing exhaust.
A new way of powering these trucks could drastically curb pollution, increase efficiency, and reduce or even eliminate their net greenhouse gas emissions. The concept involves using a plug-in hybrid engine system in which the truck would be primarily powered by batteries but with a spark ignition engine (instead of a diesel engine). That engine, which would allow the trucks to travel the same distances as today's conventional diesel trucks, would be a flex-fuel model that could run on pure gasoline, pure alcohol, or blends of these fuels. Compared to a diesel engine vehicle, a gasoline-powered vehicle produces only a tenth as much nitrogen oxide (NOx) pollution, a major component of air pollution.
In addition, by using a flex-fuel configuration that allows it to run on gasoline, ethanol, methanol, or blends of these, such engines have the potential to emit far less greenhouse gas than pure gasoline engines do and the incremental cost for the fuel flexibility is very small. If run on pure methanol or ethanol derived from renewable sources such as agricultural waste or municipal trash, the net greenhouse gas emissions could even be zero.
In order to match the efficiency of diesels, a mix of alcohol with the gasoline, or even pure alcohol, can be used and this can be processed using renewable energy sources. Detailed computer modeling of a range of desired engine characteristics, combined with screening of the results using an artificial intelligence system, yielded clear indications of the most promising pathways and showed that such substitutions are indeed practically and financially feasible.
In both the present diesel and the proposed flex-fuel vehicles, emissions are measured at the tailpipe after a variety of emissions-control systems have done their work, so the comparison is a realistic measure of real-world emissions. The combination of a hybrid drive and flex-fuel engine is a way to enable the introduction of electric drive into the heavy truck sector by making it possible to meet range and cost requirements and doing it in a way that's clean.