Hybrid cars are best for city driving but vehicles powered by natural gas are preferable in rural and superhighway travels to cut emissions, a Swiss study shows.
Swiss research institute Empa, working for the Federal Office for the Environment, conducted an investigation into the carbon dioxide emissions of hybrid cars and natural gas-fueled vehicles as the European Union seeks to meet its emission reduction targets.
The study finds that in terms of carbon dioxide emissions, both hybrid cars and natural gas cars perform significantly better than gasoline- or diesel-fueled vehicles. Under mixed city and country driving conditions, both vehicles offer reductions of up to 25 percent compared with conventional gasoline-fueled automobiles.
However, the study found that hybrids do better in inner-city driving than natural gas vehicles which are more suited for highways and long-distance country driving.
One reason for the hybrid’s good performance in cities is its ability to capture the kinetic energy of motion when the vehicle slows down or stops – a technology called regenerative breaking.
Most current hybrid vehicles feature this technology to boost the vehicle’s ability to run longer on its electric motor. The stop-and-go driving needed for city roads is optimal for energy generation using regenerative breaking.
Compared with conventional gasoline cars, hybrids achieve up to twice the efficiency in city driving, leading to less fuel consumption and even less carbon dioxide emissions.
However, driving in superhighways is a different matter. The study says that motorway driving or rural driving in a hybrid shows little savings in terms of fuel consumption or carbon dioxide emissions.
This is possibly because of the inadequacy of the energy generated through regenerative braking. In fact, on big motorways, the study says there were no difference between a hybrid and a gasoline engine vehicle.
Natural gas-fueled vehicles are practically identical to gasoline-fueled vehicles. However, they generate less carbon dioxide emissions because natural gas contains less carbon than gasoline. In addition, they emit around 20 percent to 25 percent less carbon than gasoline-fueled vehicles.
During rural driving conditions, natural gas-fueled cars and hybrids are equally “clean” while on the motorway, the former were found to actually emit less carbon dioxide than hybrid cars.
