«Only half so much CO2 allowed»
According to Christian Bach, Head of Empa’s Internal Combustion Engines Laboratory, there is a low-carbon alternative fuel available – natural gas or biogas. The less carbon in the fuel, the less CO2 emitted, and in the case of processed biogas (for example compogas) drive systems can actually be pretty much CO2-neutral. Bach made use of the Swiss Federal Office for the Environment’s Greenhouse Gas Inventory to show that road traffic is responsible for producing the greatest fraction of CO2 emissions – 30% of the total – followed by domestic and industrial usage. In addition, contrary to the intended reduction in CO2 emissions, over the past few years levels have actually increased. “There are only three means of rectifying this situation – by changing human behaviour, improving vehicle fuel consumption rates and by using fuels which release as little CO2 into the atmosphere as possible. The first option is by far the most difficult one.”
A natural gas powered automobile emits between 20 to 30 per cent less CO2 and by using biogas this figure improves to 70%. Only fuels which have a high knock resistance and high combustion temperatures can be used to power car engines, Bach informed the audience. For low temperature applications such as heating buildings or hot water supplies other energy sources such as waste heat can be used. Methane, the main constituent of natural gas and biogas, is therefore practically the ideal fuel.
Because of the low energy density of natural gas, however, the range of gas-fuelled cars – about 300 to 400 km – is currently rather less than that of a petrol powered car of comparable performance. This apparent disadvantage could in fact turn out to be a blessing in disguise, forcing automobile developers to create more fuel-efficient drives. Otherwise gas-fuelled cars would hardly stand a chance in today’s automobile market. “Because of this, gas-fuelled cars actually reverse the trend towards ever larger passenger cars, which will have an additional positive effect on CO2 emission levels”, explained Bach.
Currently Empa, together with the ETH Zurich and industrial partners, is developing a natural gas hybrid drive called «CLEVER» (for «Clean and Efficient Vehicle Research»), which for the same output power as a petrol fuelled engine, will use 20 per cent less fuel and emit 45 per cent less CO2. “We urgently need vehicles which emit only half as much as today’s petrol and diesel powered ones, otherwise we will never solve the problem”, according to Bach.
In collaboration with the PSI and various industrial companies, Empa is also developing a vehicle called «hy.muve» (for «hydrogen driven municipal vehicle») to meet the needs of communal service organizations. Powered by a fuel cell drive, «hy.muve» is intended to make the jump from laboratory to practice. Christian Bach hopes that it will open doors for the use of hydrogen as a fuel, a very promising source of energy.