The transport sector makes an important contribution to climate change in the form of carbon dioxide (CO₂) and greenhouse gas emissions due to the dependency on fossil fuels for vehicles that rely on internal combustion engines. Therefore, it is important to adopt more environmentally friendly vehicles, such as battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) powered by hydrogen [1].

All BEVs comprise an electric motor and a battery that powers the electric motor. The BEVs can be charged at home (outlet) or at a charging station.

FCEVs are powered by the chemical reaction of oxygen and hydrogen in the fuel cell, storing electricity and driving the motor with this energy. FCEVs have the advantage of longer travel distances and shorter charging times compared to BEVs [2].

Considering the fact that the number of BEVs and FCEVs sold has increased in recent years due to support from local governments and because car manufacturers focused their attention on these ecofriendly vehicles, it is important to determine the impact on the environment regarding CO₂ emissions due to their fuel ^{[3][4][5][6][7]}[3,4,5,6,7].

The toxic emissions of these vehicles while driven are zero. However, the ecofriendliness of a BEV depends on the power mix, which refers to the composition ratio of the electricity generation sources powering it [2]. The ecofriendliness of an FCEV depends on the production of its fuel, hydrogen. Most of the total hydrogen production is performed via the steam reforming of natural gas and other fossil primary energy, and only a small amount is based on renewable energies ^[3][4][5][3,4,5].

2. Battery Electric Vehicles and Hydrogen Fuel Cell Vehicles

A comparison between electric and hydrogen vehicles by considering their life cycle assessment was performed in [1]. In [2], the CO₂ emission reduction potential of BEVs in China was investigated. The results show that in 2030, the emission in the transportation sector will be lower. In [3], the CO₂ emissions associated with the deployment of EVs in Saudi Arabia (considering the energy mix) were investigated. The results showed that the replacement of 1% of petrol cars with EVs reduces emissions by 0.5%. A study was performed in [4] that investigated if the target for reducing emissions in 2050 in the United Kingdom is achievable. The results showed that plug-in hybrid electric vehicles should not be used by 2050 in order to comply with the target. A comparison of the CO₂ emissions between internal combustion engines and EVs was performed in [5] for the Canary Islands. The results were similar, with the emissions being lower for the EVs only if the renewable energy sources had a high share in the power mix. Another study performed in [6] estimated that the CO₂ emissions are 56% lower for BEVs when compared with internal combustion engines. In ^[7][8][7,8], the total life-cycle greenhouse gas (GHG) emissions produced by passenger cars were investigated. The results showed that combustion engine vehicles emit the highest amount of GHG emissions, while BEVs can reduce these emissions by 89%. In ^[9][10][11][9,10,11], the impact of EVs on the emissions inside the European Union was investigated. The results showed that these emissions will not be reduced if fossil fuels still have a significant share in the power mix. The emissions of BEVs in Poland were investigated in ^[12][13][14][12,13,14]. The results show that the emissions are comparable with those of conventional combustion vehicles due to the high share of fossil fuel power plants in the power mix. A comparison of the CO₂ emissions for PHEVs and BEVs was performed in [15]. In [16], the charging infrastructure, technology, and issues related to charging station identification were reviewed. The losses during charging were investigated in [17], with the losses being higher for single-phase charging (20.42%) when compared to three-phase charging (12.79%). In [18], the consumer preferences for electric vehicles and FCEVs were estimated; then, the greenhouse gas emissions were determined considering the power mix in South Korea. The results show that the reduction in greenhouse gas emissions was 4.7% when compared with the target for 2030. In [19], different hydrogen production methods were compared by considering environmental and economic aspects, with the results being better for electrolysis associated with renewable energy sources. The consumer preferences for electric and hydrogen vehicles were also investigated in ^[20][21][20,21]. The total cost of ownership of hydrogen vehicles was analyzed in [22]. A vehicle de-sign and total cost analysis for three types of fuel cell vehicles (simple fuel cell, hybrid fuel cell with regenerative brakes, and hybrid fuel cell with rooftop photovoltaics) were presented in [23]. Vehicles with an internal combustion engine, BEVs, and FCEVs were compared in [24] by considering uncertainties such as user and acceptance behavior, the security of the supply, and transport requirements. The fuels used in transport, namely, electricity and hydrogen, were analyzed and compared in [25]. The simulation and lifecycle assessment of electric vehicles and FCEVs was performed in ^[26][27][26,27] by considering different hydrogen production methods. The barriers to the acceptance and use of hydrogen vehicles were analyzed in [28]. The development and possible challenges regarding adopting hydrogen vehicles, such as infrastructure and ownership cost, were investigated in ^[29][30][29,30]. In [31], the potential hydrogen demand was determined, and an optimization model was determined in order to achieve the best production/demand cost for hydrogen. The demand for hydrogen in 2030 and the flexible electrolysis production that lowered the operating costs and CO₂ emissions were simulated in [32]. The design for a hydrogen fueling station that integrated an ejector was presented in [33], and the proposed model was evaluated, with the results showing an improvement in energy efficiency. The fueling infrastructure of FCEVs was analyzed in ^[34][35][34,35], while in [36], a planning model was developed for a hydrogen supply infrastructure combined with renewable energy sources. In [37], the production cost and emissions for hydrogen from fossil fuels (coal and gas) and renewable energy sources were determined. In [38], a comparison of the emissions for hydrogen vehicles was performed by considering different scenarios between 2010 and 2050. The lowest total emissions were for FCEVs that used gaseous hydrogen. A comparison of two sampling methods for a 70 MPa hydrogen refueling station was presented in [39]. The types of fuel cells for a hydrogen vehicle were presented in [40], while in ^[41][42][43][41,42,43], the ways in which hydrogen is produced and the emissions in the hydrogen production process were analyzed. Control strategies were developed in ^[44][45][44,45] for fuel saving in FCEVs. In [46], the power consumption of refueling stations was optimized by considering the number of tanks and the volume and pressure in the tanks. In [47], the possible advantages and disadvantages of the use of hydrogen vehicles in an urban environment were investigated. An off-grid charging station was designed in ^[48][49][48,49] for electric and hydrogen vehicles using solar power. In [50], a stochastic model was designed in order to determine the unit commitment of the power sources and storage of an energy hub that included parking lots for hydrogen vehicles. The operation cost of the energy hub was reduced by 27.58% by considering demand response, by 12.68% when storage systems were used, and by 2.9% when hydrogen vehicles were used. The optimal planning of an islanded microgrid that comprised electric vehicles, hydrogen vehicles, and storage was studied in [51] for different weather conditions. The planning of an integrated power, hydrogen, and gas network that included hydrogen vehicles was optimized in ^[52][53][52,53]. The optimal scheduling of microgrids that comprised hydrogen vehicles in real-time and day-ahead power markets was determined in [54]. The operating cost of an integrated electricity and gas network for electric and hydrogen vehicles was minimized in [55] by considering different availability and capability scenarios. The optimization of biomass-based hybrid hydrogen/thermal energy storage system operation for a building and hydrogen vehicles was analyzed in [56] by considering two strategies: power demand with hydrogen load and thermal demand with hydrogen load. Power demand with hydrogen load obtained better results by considering the primary energy consumption saving ratio, annual total expenditure reduction ratio, and CO₂ emission reduction ratio. A multi-objective optimization was performed in [57] for hybrid renewable energy systems that included BEVs and hydrogen vehicles. The supply performance results were better when only the hydrogen vehicles were connected, while the grid integration, economic, and environmental aspects were better when only the BEVs were connected. The urban heat island intensity and CO₂ emissions in an urban city, considering different mobility concepts (conventional, electric, and hydrogen vehicles), regular power mixture, and power supplied only by wind turbines, was analyzed in [58]. The hydrogen vehicles fueled from a regular power mix had higher heat island intensity and CO₂ emissions. The CO₂ emissions were lower when the electric and hydrogen vehicles were powered with electricity generated from wind turbines. A management scheme was developed in [59] for a building that included solar, wind, and battery storage units, as well as electric and hydrogen vehicles, such that the cost of energy consumption was minimized. The air quality impact of FCEVs that were supplied in a considerable manner by renewable energy sources was investigated in [60], while in [61], the challenges regarding measurement were identified for the hydrogen industry, such as sampling, metering, quality control, and assurance.