The development of electromobility in the aspect of the energy infrastructure condition assessment

Electric vehicles are considered emission-free. However, having high-emission and a high degree of electricity demand coverage infrastructure, these vehicles should be considered as internal combustion cars. The purpose of the analysis carried out in this study is to present the state of energy infrastructure in Poland, to determine losses related to energy transmission and greenhouse gas emissions to the atmosphere in relation to unit consumption. Analyzing the data obtained, the emission of the electric vehicle was compared to that of a vehicle powered by diesel oil and fuel with the addition of a biocomponent.


Introduction
Restrictive regulations contribute to the creation of new legal principles in the field of energy, industry and means of transport as these are the main sources of harmful substances emission into the atmosphere. Actions decentralizing the energy sector, in which the client becomes a prosumer are being taken. When using renewable energy sources, the surplus of unused energy is sent to the network. With the current technological solutions, full energy accumulation is not possible and the continuous support of conventional power plants is required to ensure the continuity of electricity supply. In Poland, over 67% of electricity comes from commercial thermal power plants powered by lignite and hard coal. Contemporary electric vehicles use construction solutions that are nearly one hundred years old yet are now coupled with modern computer technologies. Many research institutions constantly conduct studies aimed at improving the operational parameters of the vehicles. However, it cannot be concluded that these types of vehicles are emission-free. This is due to the insufficient amount of clean energy produced. Therefore, in terms of the impact on the environment, electric vehicles should be considered just like any other vehicles with conventional combustion engines. Differences affecting the amount of substances emitted into the atmosphere result from the applied construction solutions, as well as external factors having a direct impact on the operation of the vehicle [1, 10,[15][16][17][18].

Analysis of the national energy infrastructure
The energy infrastructure in Poland consists of commercial power plants, which are divided into hydroelectric and thermal power plants powered by coal or gas. There are also auto producer power plants and the ones using renewable energy sources [1]. Plants powered by hard coal and lignite are considered high-emission power plants. It is estimated that 67.37% of this energy is produced by 16 power plants managed by 4 different operators. Newly built power plants are characterized by high efficiency, amounting to 49.7%. However, the average efficiency of all power units is about 41.08%. Mutual correlation between the gross production efficiency and the emission of dust and greenhouse gases to the atmosphere can be observed [2]. When analyzing power plants with the same power unit capacity, but with the difference in efficiency amounting to 1.10%, a significant reduction of harmful substances can be observed. The emission of dust is reduced by 67.30%, sulfur dioxide by 32.53% and carbon dioxide by 17 Renewable energy sources constitute a very unstable energy sector in Poland. In 2014, the installed capacity was estimated at 15.3% of which the real production value was 6%, which is only 39.21% of the declared capacity. Due to the intermittent character of work caused by changing weather conditions, it is necessary to use large reserves in order to ensure continuity in energy supply to consumers. During the periods of inefficiency caused by significant cloud cover and lack of wind, it is necessary to use the full availability of energy resources from other branches [5].
Apart from low efficiency in power generation, there are also losses associated with distribution and transmission. The losses in networks result from the conversion of electricity into heat. This phenomenon is described by the Joule-Lenz law, which says that the thermal power density of a current in a conductor is equal to the product of its specific conductivity and the square of the electric field strength. The origin of these losses can be classified as no-load and load losses. Based on substitute diagrams, the no-load losses are expressed by the resistance in the transverse branches defined as the square of the voltage at a given location. The load losses are expressed by the resistance in the longitudinal branches, and their value is proportional to the square of the current flowing in a given branch [7].
It is also important to present how differentiated the unit costs of generated and sold energy for individual sectors of the energy industry are. The difference in price may be more than three times greater for producing the same amount of energy [5].

The analysis of the means of transport emission
The act on electro mobility is aimed at popularizing electric means of transport. An electric vehicle, unlike a combustion vehicle, does not have a strictly defined "exhaust emission" and its actual values depend on the energy system in a given country [8]. On the basis of the above analysis, taking into account the condition of the energy infrastructure in Poland, it can be assumed that the coefficient of the energy origin from high-emission sources is α = 0.75. Therefore, it is possible to estimate the amount of harmful substances emitted into the atmosphere, taking into account the losses at the distribution stage and the share of highemission sources in the energy system. Having approximate data on emissions and losses, it is possible to estimate the amount of greenhouse gases emitted by electric vehicles and compare them to conventional vehicles powered by diesel oil and fuel enriched with biocomponents.
On the basis of the summary of the most popular electric vehicles available in Poland and their technical parameters, it is possible to determine the emission of individual substances into the atmosphere, which is emitted due to the vehicle being supplied with electricity [9]. Energy consumption in electric vehicles, which is directly related to the emission of carbon dioxide, sulfur dioxide and nitrogen compounds, is influenced by, among others: • power and number of propulsion engines, • the weight of the vehicle • weather conditions, • ,aerodynamic drag coefficient, • type of tires used. The difference in "the emission" of harmful substances in relation to the network from which the energy is taken amounts to a maximum of 6%. This contributes to a slight fluctuation in greenhouse gas emissions by changing the voltage of the network that powers the vehicle.
On the basis of the above analysis, electric vehicles can be compared to conventional combustion vehicles powered by diesel fuel or a mixture of biocomponents with diesel fuel.
The study was conducted for a passenger car of up to 3.5 t of maximum permissible laden mass with a 1.6 HDI diesel engine [12]. As the basis for the analysis, all considerations have been narrowed down to one of the criteria, which is carbon dioxide emission. The average value of CO 2 emitted for a vehicle with a diesel engine is 114 g km [11]. However, after the modification of the controller, which influenced the boost pressure of the turbocharger and the increase of the fuel dose enriched by volume by 10% of fatty acid methyl esters [12], the emission was reduced by 1.036% compared to the serial settings, which translated into the production of 109.867 g km of carbon dioxide [13]. The Audi E-Tron vehicle with a CO 2 average emission at the level of 209.395 g km , assuming that the share of high-emission power plants α = 0.75, showed the emission higher by 47.53% than the modified diesel engine, which additionally showed power and torque increase measured on the wheels with a dynamometer [12].

Summary
On the basis of the analysis carried out in the study, it can be concluded that the emission of harmful substances into the atmosphere produced by coal-fired power plants, which are the basis of the national power industry, covering up to 75% of the energy demand, has an average efficiency of 41.08%. The losses related to the transmission and distribution on networks of various voltage contribute to the greater amount of carbon dioxide emitted in order to produce 1 kWh of energy. In the case when the real efficiency of renewable energy sources is only 39.21%, it is necessary to use energy reserves from other energy sectors. This directly translates into air quality, as alarms are raised in many places about exceeded permissible values which is harmful to health [14].
Due to the insufficient infrastructure of low-emission energy sources, electric vehicles mostly use electricity generated in coal-fired power plants. Considering their emissivity like other motor vehicles is justified because electric vehicles are powered by the energy generated from coal. A passenger car equipped with a 1.6 HDI diesel unit powered by a mixture of diesel oil and fatty acid methyl esters, as well as a modified engine controller shows 47.53% lower CO 2 emission than the Audi E-Tron electric vehicle. Assuming that the vehicles will cover the distance of 20,000 km per year, the difference in the amount of carbon dioxide emitted will amount to 1,990.56 kg. The analysis shows that the interference in the diesel engine control unit and the change of power supply brings measurable benefits in the form of improvement of operating parameters and the reduction of CO 2 emission by over 1%. An electric vehicle gains an ecological advantage when it is charged directly from installations based on renewable energy sources. An example is a home photovoltaic installation, thanks to which the amount of energy loss is significantly reduced. Due to different weather conditions, the efficiency of the system changes, thus influencing the time of charging the vehicle.
At the same time, other operational criteria for means of transport [15][16][17][18][19][20][21][22] should be taken into account, which in the overall analysis and assessment of this issue are equally important.