Natural gas, also known as Biogas, a designation that reflects the fact that it is the most environmentally friendly of fuels, consists mainly of methane (about 90%), with small amounts of ethane, propane and other gases. Methane is a simple gas molecule, composed of one carbon atom and four hydrogen (CH4). It is lighter than air and burns almost entirely, only resulting in carbon dioxide and water as by-products of combustion. Methane, which is found in abundance in landfills and dumps, as well as in livestock farms, can be reused as a fuel, cheaper and less polluting than gasoline or diesel.
The acronym GNC stands for Compressed Natural Gas, that is, it is natural gas under pressure. With a clear, odorless and non-corrosive aspect, CNG is being seen as a cheaper, more ecological and more efficient alternative to traditional fuels, gasoline and diesel. CNG is mainly composed of methane which, like gasoline, produces energy by explosion when mixed with air in the engine's combustion chamber. The gas is compressed so that it is possible to store enough fuel in the vehicles, in small tanks, so as not to compromise the autonomy or the available space. Gasoline or diesel engines must be converted to use CNG.
The CNG is stored under high pressure, around 200 bar, in deposits built and approved under conditions that can withstand filling with a maximum pressure of 260 bar and subjected to hydrostatic tests of 300 bar.
They comply with extremely strict safety standards and are made of high-strength materials, designed to withstand impacts and punctures. In addition, they are equipped with a thermal fuse that cuts the circuit and relieves pressure, providing controlled ventilation in the event of a sudden increase in temperature, releasing the remaining gas safely. The pipes are made of stainless steel and the system also includes electronic and mechanical safety valves that control or isolate sections of the high pressure circuit if necessary.
SEAT's TGI (Turbo Gas Injection) technology is one of the most efficient examples on the market, and is already available in several models of the brand. Being developed and produced entirely by the Spanish manufacturer, the TGI system is an integrated factory solution and not a mere adaptation of the engine.
Vehicles with a CNG engine (TGI – Car Terms) operate with the same basic principles as vehicles equipped with a combustion engine. When the engine is started, natural gas flows from the storage tank through an appropriate fuel line. Next to the engine, natural gas enters a pressure regulating device that will reduce it before entering the combustion chamber. Then, a gaseous fuel injection system introduces natural gas into the engine. The sensors and the Electronic Motor Control Unit adjust the air / fuel mixture so that when the spark plug operates, natural gas burns in the most efficient way. There is also a set of specific components that allow a fluid and uninterrupted operation between the modes of operation with gas or gasoline, so that the transition when the gas runs out is imperceptible. On the instrument panel there are light indicators that remind the driver what fuel is in use and what levels are in both tanks. Furthermore, in terms of driving, there are no noticeable differences for those behind the wheel.
The supply is done in a similar way and takes the same time. Only the nozzle of the filling gun is different, being specifically designed to couple with the nozzle. As natural gas is under pressure, storage systems are designed so that no fuel is lost when the vehicle is being refueled. The nozzles of the filling guns fit tightly to the nozzle, for a leak-free seal, as with the valves of an air compressor. The tanks and the nozzle have non-return valves, which prevent natural gas from escaping when the supply ends. The network of service stations is currently growing in the European Union and has a specific community support program. Within the scope of policies to promote the circular economy (roadmap to 2030 document) there are forecasts that point to an exponential growth in the use of natural gas, for example, with the supply network expected to triple in number of stations by 2030.
This is one of the great advantages of a hybrid vehicle. Although the CNG works normally, it has the option of using gasoline in emergency situations allowing to reach a gas station. By the way, in commercial terms, the consumption values of these models are indicated only in kg / 100 km, referring to the CNG and disregarding the eventual consumption of gasoline. In these models it is recommended to exhaust the gas and drive for a few kilometers on gasoline, every 6 months, to keep the circuits in good condition and also to avoid the degradation of liquid fuel in the tank. With forecasts pointing to an exponential increase in the worldwide sales volume of hybrid vehicles, SEAT is positioned at the forefront by betting heavily on the introduction of compressed natural gas (CNG) technology. Produced in the same factory as the Ibiza TGI, on the outskirts of Barcelona, the Arona TGI is the first SUV from SEAT equipped with a propulsion system using compressed natural gas. Both models are equipped with the same three-cylinder engine, with 999 cubic centimeters (cc), 12 valves and a six-speed manual gearbox. With the same power of 90 hp and 160 Nm of maximum torque, the SEAT Arona TGI and SEAT Ibiza TGI guarantee autonomy for 360 km in GNC mode, but can continue on the road when the gas runs out because they have a tank with a capacity of nine liters of gasoline, enough to cover another 150 km.
A GNC vehicle is able to reduce CO2 emissions by about 25% and NOx emissions by up to 75%, compared to the identical gasoline-powered model. For example, SEAT Arona TGI emissions vary between 104 and 115 g / km, according to the current WLTP standard, depending on the size of the tires and wheels and the level of equipment. In Portugal, there are tax benefits for vehicles equipped as standard with a CNG engine, whether purchased by individuals or companies. In addition to the reduction in Vehicle Tax (ISV), for companies there is a reduction in the values of Autonomous Taxation at all levels and a 50% deduction of VAT included in GNC models with a retail price of up to 37,500 euros. In addition, it is possible to deduct half the amount of VAT paid on fuel. In addition to the environmental and tax benefits, GNC technology offers exceptionally low costs per kilometer, up to 50% cheaper than a gasoline model and 30% cheaper than a Diesel, with equivalent engines. To give you a clearer idea, in a comparative analysis, the average cost to travel 100 km with TGI (Turbo Gas Injection) technology allows you to make only 61 km in a model with an engine equivalent to direct injection diesel and only 49 km, less than half, in the case of a gasoline block. SEAT takes the advantage of offering customers a real, effective and modern alternative, offering GNC versions of its models that cost practically the same as the equivalent Diesel variant. In addition, maintenance costs for TGI models are similar to traditional combustion engine vehicles.