The article presents the current state of the CNG market used as an alternative fuel for car engines. Attention was paid to European Union directives requirements and the current state of the directives’ fulfillment. The economic aspect of CNG usage was analyzed and the approximate costs of driving 10,000 km on different fuels in the last four years were presented. The PtG process which uses electric energy (hydrogen production) and carbon dioxide captured from the flue gas for the production of synthetic methane were discussed. The scheme of the SNG plant with the indication of its most important components was presented, and attention was paid to the mutual complementation of PtG technologies with carbon dioxide capture technology. The benefits of synthetic methane production are presented and the use of compressed natural gas to power engines in vehicles has been described. First, the focus was on the single-fuel use of CNG in bus and truck engines, paying particular attention to the ecological aspect of the implemented solutions. It has been shown that the use of compressed natural gas will reduce almost 100% of the particulates emission from the combustion process. The advantages and disadvantages of the alternative fuel supply are given. Next, the aspect of dual-fuel use in diesel engines was analyzed on the example of a smaller engine. The degree of reduction of harmful compounds emission from the combustion process is shown. Finally, attention was paid to the possible scale effect, referring to the number of motor vehicles in Poland.

The uncertainty in the supply of crude oil, increasing the number of vehicles and rising air pollution, especially in urban areas, has prompted us to look for alternative fuels. It is understood that using Compressed Natural Gas (CNG) in IC engines could be a mid-term solution to these problems. It is well established that CNG has better combustion characteristics and low emissions compared to conventional gasoline and diesel fuel. In the present study, an experiment was conducted to evaluate the engine performance and exhaust emissions using various percentages of CNG in dual fuel mode. CNG was mixed in the intake manifold’s air stream, and diesel was injected after the compression of the CNG air mixture. This paper presents experimental results of 40%,60%, and 80% CNG in the air stream. Engine performance and emissions are presented and discussed at a speed of 1200 rpm to 1500 rpm in steps of 50 rpm. The results of the experiments showed that adding CNG to diesel engines in dual-fuel combustion significantly impacted performance and emissions. Compared to single diesel fuel combustion, dual fuel combustion increases brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) at all CNG energy shares and engine speeds. Carbon monoxide (CO) and hydrocarbon (HC) emissions were increased, while nitrogen oxide (NOX) and smoke opacity were decreased in dual fuel combustion compared to single diesel fuel.

Transport drogowy oraz morski oparty jest głównie na wykorzystaniu paliw ropopochodnych, tj. ropie naftowej, benzynie oraz LPG (Liquefied Petroleum Gas). Światowe zasoby ropy naftowej stale się kurczą i przewiduje się, ze wystarczą na kilkadziesiąt lat. Ponadto stale zwiększające się obostrzenia dotyczące emisji spalin powodują, że silniki są coraz bardziej skomplikowane, co przekłada się na wyższy koszt oraz niższą niezawodność. Dlatego też zauważalny jest trend w celu poszukiwania alternatywnych paliw do zasilania pojazdów. Obecnie można wyróżnić trzy kierunki rozwoju technologii: zasilanie energią elektryczną, wodorem lub gazem ziemnym. Ze względu na fakt niskiej pojemności baterii, co przekłada się na niski zasięg pojazdów i poważne trudności z magazynowaniem wodoru oraz niską efektywność termodynamiczną ogniw, najbardziej perspektywicznym kierunkiem wydaje się zasilanie pojazdów gazem ziemnym. Zasoby gazu ziemnego są znacznie większe w porównaniu do ropy naftowej. Ponadto spalanie gazu ziemnego praktycznie eliminuje emisję szkodliwych dla zdrowia tlenków azotu, siarki oraz cząstek stałych. Jest on również paliwem powszechnie dostępnym, ze względu na znaczne pokrycie terytorium Polski rurociągami. Jednakże ze względu na niską gęstość energii gazu ziemnego w warunkach otoczenia, wymaga on specjalnego przechowywania – może być magazynowany jako gaz sprężony do ciśnienia ponad 200 barów (CNG – Compressed Natural Gas) lub w postaci skroplonej (LNG – Liquefied Natural Gas). Pozwala to na zwiększenie gęstości energii do poziomów porównywalnych od oleju napędowego i benzyny. Dodatkowym zagadnieniem jest możliwość wykorzystania chłodu pochodzącego z odparowania LNG do celów klimatyzacyjnych lub chłodniczych. Jest to jednak uzasadnione w przypadku transportu ciężkiego, gdzie strumień gazu jest relatywnie wysoki.

This article presents the results of an assessment of the potential for the use of CNG in Poland as a fuel for passenger cars powered by an internal combustion engine fuelled by petrol or diesel. The basis for assessing the potential was an analysis of the economic efficiency of converting a passenger car fuelled by petrol or diesel to a dual-fuel vehicle by installing a CNG system. On the basis of available literature data, the vehicle structure was characterised using the following criteria: vehicle age, engine capacity, car-segment, type of fuel used and kerb weight. The average fuel consumption (petrol or diesel) of the vehicle before conversion was determined on the basis of specially developed statistical models. The conversion and operating costs of a vehicle fuelled with conventional fuel and with CNG (after vehicle conversion) were estimated on the basis of a stochastic simulation model using probability density distributions of vehicle parameters and the Monte Carlo method. The vehicle parameters were estimated so that the obtained set of vehicles reflected the actual structure of passenger cars in Poland. The estimated costs of vehicle conversion (purchase and installation of a CNG system) and its subsequent operating costs made it possible to assess the economic efficiency of the car conversion process. The potential use of CNG as a fuel for combustion cars was estimated by comparing the operating costs of a vehicle before conversion and the operating costs of a vehicle after conversion, taking into account the costs of conversion. Analogous calculations were carried out for the conversion of a vehicle to run on LPG, i.e. the most important competitor to CNG.