Biogas as a fuel for passenger cars with an internal combustion engine in view of efficiency potential, driving range and CO2 emission

Abstract

Driven by the demand on the transportation sector to reduce global emissions of carbon dioxide, the potential of biogas as a fuel for passenger cars was tested and simulated. Within the work scope of the joint research program "Virtual Biogas", the production of biogas, the upgrading (= CO2 reduction) and its use was investigated. The project partners Biogas Bruck/Leitha, TU Vienna and Axiom produce biogas and upgrade it according to the requirements of ÖVGW G31, G33 to be able to feed biogas as "biomethane" into the natural gas grid. In that way, biomethane reaches the consumer "virtually" via the infrastructure of the existing natural gas grid. The particularly cost efficient gas permeation upgrading technology was used. The research project included the production of different biogas mixtures with a varying remaining CO2 content. In addition hydrogen and propane were blended into biogas. With a single cylinder research engine, the gas mixtures were tested on an engine test bed in combination with the gas direct injection combustion system, developed by AVL List. By means of gas exchange and thermodynamic engine cycle simulations, the test bed results were transferred to a 4 cylinder engine to create a fuel consumption map. The subsequent complete powertrain simulations allowed the prediction of CO2 emission levels and driving range potentials of fully optimized turbocharged biogas hybrid vehicles. In parallel, due to the potential of increasing the peak firing pressure of the engine, a new piston design was developed, so that it can resist the Diesel-like PFP level in combination with engine speeds of an Otto engine. Due to the fact that methane, the main content of natural gas burns with a 25% lower CO2 emission than gasoline, the combination of natural gas with biogas as a biogenic substitution is very promising in view of climate protection and sustainability. The engine tests and simulations have proven that for a 1590 kg Volkswagen Passat reference car, with a turbocharged gas engine in combination with an optimized hybrid powertrain, the CO2 emission can be reduced to clearly less than 100 g/km. By gradual substitution of natural gas with biogas, the share of fossil CO2 emission can be reduced much further than with other biofuels. In addition, with an optimized gas vehicle, driving ranges, which customers expect from today's gasoline cars, are feasible.