*Article* **Research of Load Impact on Energy Consumption in an Electric Delivery Vehicle Based on Real Driving Conditions: Guidance for Electrification of Light-Duty Vehicle Fleet**

**Wojciech Cieslik 1,\* and Weronika Antczak <sup>2</sup>**


**Abstract:** Electromobility is developing rapidly in all areas of transportation, starting with small personal vehicles and passenger cars through public transportation vehicles and ending with noticeable expansion in the area of urban transportation services. So far, however, there is a lack of research determining how the effect of load weight defines the energy intensity of a vehicle under real conditions, especially in the areas of urban, suburban and highway driving. Therefore, this paper presents an analysis of a representative delivery vehicle and its energy consumption in two transportation scenarios where cargo weight is a variable. A survey was also conducted to determine the actual demand and requirements placed on the electric vehicle by transportation companies.

**Keywords:** electric light-duty vehicle; usability of an electric delivery vehicle; real energy consumption

#### **1. Introduction**

For a number of years now, road transport has gone through considerable alteration. Ongoing research on more efficient, yet environmentally friendly powertrains supports the EU's 2030 climate policy implementation [1]. However, most attention is paid to passenger car electrification, overlooking the need for heavy-duty (HDV) and light-duty (LDV) vehicle customization. In compliance with European Environment Agency insights, HDVs, i.e., buses, coaches, and trucks, account for approximately a quarter of the carbon dioxide (CO2) emissions from road transport in the EU. Poland, as a holder of the largest truck fleet in EU, contributes to these emissions for the most part [2]. In order to launch a general road transport transformation, a framework for HDV and LDV electrification should be developed.

Profound discussion regarding electrification of heavy vehicles has considerable potential to direct the further development of electromobility in general. Research conducted in the past drew key conclusions that the crucial parameter influencing electric vehicles energy consumption is their mass [3–5]. In contrast to vehicles with conventional powertrains, where the engine power is the leading light in the fuel consumption rate, performance of vehicles driven by electric motors is not as reliant on the rated motor power. Such a feature, correlated with the high overall efficiency of electric powertrains, may shed light on the success of small EVs, notably evident in urban areas. Electro-micromobility is the central thread of pursuing change in the urban transport structure [6]. Cities worldwide have already experienced adjustments in the used and obtainable means of transport. This trend is intensely fostered through vehicle-sharing systems advancement and broadening the accessibility of electric means of microtransport, just as a couple of examples [7–9]. While micromobility is undoubtedly suitable for city residents' transportation, it will not meet the requirements of the transportation of mass goods. This need should not be omitted, as

**Citation:** Cieslik, W.; Antczak, W. Research of Load Impact on Energy Consumption in an Electric Delivery Vehicle Based on Real Driving Conditions: Guidance for Electrification of Light-Duty Vehicle Fleet. *Energies* **2023**, *16*, 775. https:// doi.org/10.3390/en16020775

Academic Editor: Chunhua Liu

Received: 13 December 2022 Revised: 29 December 2022 Accepted: 4 January 2023 Published: 9 January 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

delivery vans are becoming a more and more common element of urban structures, due to the rapid rise in popularity of online shopping [10].

Scientists have already acknowledged this issue, beginning to conduct examinations verifying the actual suitability of electric vans for delivery and transportation companies. Most of these studies are focused on analyzing a variety of delivery scenarios by means of algorithms and thus proposing the best charging stations' arrangement to overcome battery capacity limitations [11–16]. The conclusions and proposed adjustments are fundamental for reasonable planning of road infrastructure modification; however, they mostly do not consider real driving conditions, including traffic, variable loads, and driving style.

One of the possibilities to conduct research that takes account of the wide range of potential variables is to carry out road tests performed in compliance with the RDE (real driving emissions) procedure. It allows the counting of different road infrastructures, traffic, road slopes, and driving behaviors, simultaneously assuring compliance with European Union regulations test procedures [17]. Thanks to the prescriptive test method, results obtained for the different vehicle and powertrain models can be compared and submitted for analysis. While the RDE tests are focused on reflecting the vehicle's impact on the environment, research that draws on their procedures but omits exhaust emission analysis is referred to as testing RDC (real driving conditions) [18,19]. Such examinations have been performed in the past; however, they regarded combustion engine, hybrid, and electric passenger cars for the most part [20–27]. Thereby, the electrification potential of HDVs and LDVs remains an insufficiently researched subject.

According to the data presented in Table 1, the number of both passenger EVs and large EVs registered in Poland has doubled year on year since 2019. While such an increasing rate is highly desirable, it is clearly seen that large EVs still play a minor role in the global service sector. To reach the goal of climate neutrality, immediate changes in this area are needed.


**Table 1.** Number of registered electric vehicles in Poland in recent years (based on [28]).

<sup>1</sup> **Delivery vans and trucks**; <sup>2</sup> buses; <sup>3</sup> electric bikes, scooters.

Light-duty vehicles, being so far challenging for electrification, remain a common element of the urban landscape and thus have an input into cities' noise and air pollution. Moreover, the demand for the road freight transport has been continuously growing. The necessity to undertake further actions aiming to decarbonize the transport sector has encouraged authors to pursue research on the actual usage potential of electric delivery vans. With the aim of conducting tests possibly akin to real-life driving conditions, a survey has been created. The questionnaire focuses on gathering data that portray the expectations imposed on the delivery vehicles, as well as actions that could possibly spur users to turn to electromobility.

This article consists of six main sections. The first one describes the general research problem and presents the current state of the Polish fleet of various EVs. The second chapter is covers the survey that was disseminated among transport companies and other relevant businesses and data gathered on their demand for electromobility. The third part describes the research objective: details regarding vehicles chosen for tests and the software utilized for data gathering. In the fourth section, a description of the routes driven during examinations and weather conditions on the measurement days can be found. The fifth

chapter is a comprehensive presentation of results and data analysis, while the sixth one contains a conclusion and guidelines for light-duty fleet electrification.

The information gathered throughout the series of driving tests combined with the interviewees' answers may serve as a comprehensive guide for electrification of the lightduty vehicle fleet.

#### **2. Survey Assessment: Guidelines and Demand of Transport Companies for Electromobility**

#### *2.1. Questionnaire Design*

For familiarization with the actual working conditions and the scale of electric delivery vehicle usage, a questionnaire was created. The target group consisted of individuals performing professional duties with the aid of delivery vehicles or representing relevant companies, i.e., delivery and transportation companies, as well as self-employment. The survey investigated interviewees' perspectives on the usefulness of electric delivery vehicles at their current technological level. Moreover, interviewees' perceptions on the ongoing projects fostering electromobility and expectations associated with them were assessed.

#### *2.2. Data Collection*

The questionnaire was designed with the aid of the Google Forms platform and disseminated online. It was distributed predominantly on media platforms among professional groups and through mailing lists to selected businesses. Video footage promoting the study and encouraging receivers to take part in the survey had been released on YouTube [29] and further advertised on social networks. Additionally, business cards containing references to the questionnaire were produced and spread around university and cooperating car dealers. The survey was available in Polish and disseminated among relevant companies and individuals across Poland. The data were collected from mid-July to mid-August 2022.

#### *2.3. Data Analysis*

A total of 51 responses were gathered. Initially, interviewees were asked about the type of propulsion with which the delivery vehicle is equipped. Obtained data show the predominant usage of CI engines in large cars, having been declared by 83% of the respondents. Delivery cars driven by electric motors were used by only 3% of the respondents, pointing to their still-modest use (Figure 1).

**Figure 1.** Current status of the surveyed fleets in terms of their propulsion system (based on the survey).

The number of collected survey responses represented virtually 1000 delivery vans. Both small fleets, beginning from two delivery vans, as well as large fleets comprising more than 200 vehicles, are included herein (Figure 2).

**Figure 2.** Number of vehicles managed by each fleet and their average daily distance, indicating the potential of different versions of a battery capacity to meet vehicle range requirements as well as the range of electrification potential in particular companies (based on the survey). <sup>1</sup> Electric range ensured by the manufacturer for Toyota Proace Electric with 16" steel wheels. It is highlighted that these figures may not reflect real driving conditions (RDCs). Electric range depends on accessories package, driving style, conditions, speed, load, etc. [30].

As shown in Figure 2. daily distance covered by the delivery vehicle declared by almost a third of respondents exceeds the range declared by the manufacturer for the Toyota Proace Electric with a 50 kWh battery. Greater battery capacity naturally enhances the range, but still does not meet all potential users' needs. It should be highlighted that the theoretical range ensured by the producer is given for the unloaded car with the basic accessories package. Thus, it may be assumed that the predominant part of the electric delivery vans executing delivery or transportation services in real driving conditions, that is, with additional load and greater daily distance covered, will demand recharging during the workday, i.e., while loading or unloading. However, this solution requires infrastructure customization.

Of the examined group, 77% chose cargo vans. That statistic alone points out the reasonableness of the car model choice for the examination. Frequently chosen by users' car bodies included Luton and city vans as well, both being represented by 22% of the answers (Figure 3). This confirms the appropriateness of the choice of research object.

**Figure 3.** Type of light-duty vehicle used in the company (based on own survey).

Commercial vehicles are characterized by a wide variation of construction depending on their intended use, with many models of currently available vehicles available in a variety of bodies. Both passenger and cargo versions are observed, with open or closed cargo area. Selected cars available on the Polish market have been compared with each other by the basic parameters declared by manufacturers. In this way, a summary was created indicating selected electric vehicles and their range according to the WLTP test, depending on battery capacity (Figure 4).

**Figure 4.** List of battery capacities of an electric LDV available on the Polish market, combined with their catalogue range based on the WLTP test [31] (marked with a red, color two versions of the test vehicle varying in battery capacity).

The examined group was roughly equally divided in terms of car loading at the beginning of a workday. Merely 4% of respondents declared to take less than 100 kg of goods (Figure 5). This information should be considered notably, as load is one of the factors affecting an electric car range.

**Figure 5.** The average load at the beginning of a workday (based on own survey).

Interviewees were requested to indicate which of the ongoing projects fostering electromobility could encourage them to modify the fleet of vehicles into electric-powered models (Figure 6). Government subsidy for purchasing electric cars proved to be the most efficient way to raise the interest in electromobility. Moreover, free charging stations, as well as allowance for bus lanes usage, turned out to play an important role for potential electric delivery vehicle users.

**Figure 6.** Factors deciding willingness to modify a fleet vehicle to electric-powered models (based on own survey).

#### *2.4. Conclusions*

Building on the survey answers, the following conclusion can be drawn:


#### **3. Research Object**

The electric vehicle under test was a cargo van-type body structure. Its GVW is 3055 kg, and in the provided version of the equipment for the road tests conducted, the weight of the vehicle was 2115 kg (the weight limits related to the tested vehicle are shown in Figure 7; these values are presented on the basis of the registration certificate, which is an approval document showing the parameters of a specific model, and on the basis of the manufacturer's data). Based on these values, the vehicle's loading ranges were determined, defining the carrying capacity.

**Figure 7.** Mass limits of the tested vehicle (values read from the registration certificate of used in research vehicle) based on [32].

During the tests, the vehicle was equipped with a diagnostic system consisting of a diagnostic computer and a GPS signal recorder (Figure 8). The vehicle was equipped with a 75 kWh battery (optionally, the vehicle can also be equipped with a smaller 50 kWh battery capacity). Despite the available space, larger battery capacities are not available, which is determined by the maximum allowable weight of the vehicle. Data were collected with the use of an OBD diagnostic system and GPS module. The OBD system allowed the gathering of parameters related to the powertrain or the high-voltage battery performance. The frequency of data collection equaled 2 Hz.

**Figure 8.** Schematic of the measurement system including a view of the location of the traction battery [32].

In its current configuration, the vehicle can be loaded with a weight of 940 kg. This weight represents both the weight of the load space goods and the weight of the driver and passengers. Therefore, when taking into account the maximum possible loading weight, it is necessary to take into account the weight of the vehicle's users as well (in the tested version, the homologation specifies three people in the passenger compartment). The research reported in the current work concerns the analysis of the maximum loading weight, that is, the weight of the driver (90 kg) and a cargo weight of 850 kg (Figure 9).

The realized research aims to assess the actual power consumption of an electric delivery car both in real traffic conditions and real driving conditions that include the influence of a load on the powertrain performance. An electric vehicle (EV), contrary to a hybrid (HEV) or a fuel cell (FCEV) vehicle, is characterized by considerably fewer powertrain operating modes. Considering the drive phase only, two modes can be differentiated: drive mode, during which the high voltage battery is discharged and deceleration mode, when the battery is recharged (Figure 10). The high-voltage battery may by charged with the aid of an external power source; however in this research, the charging process analysis is regarded as not a critical element.

**Figure 10.** Drive train operating modes while driving (- —electric drive motor, - —inverter, - —traction battery, - —on-board charger/DC-DC voltage transformer, - —ancillary battery, -—reduction gear) [32].

#### **4. Measurement Route and Conditions**

Research was conducted in compliance with RDC (real driving conditions) test requirements, which are shown in Table 2 in detail, and effective traffic regulations.


**Table 2.** Real driving conditions shorter test requirements [33].

The marked route, depicted in Figure 11, met the RDC test requirements imposed by the European Union regulations. Thereby it consisted of the urban, rural and motorway sections, closely selected in accordance with the requirements imposed for the particular route sectors (Figure 12).

**Figure 11.** Route driven during the examinations.

**Figure 12.** Route divided into particular sections (S\F—Start/Finish).

Tests were performed with the aid of an electric delivery van in Poznan (Poland) and its vicinities. The car was driven by only one driver throughout the tests, thus eliminating the influence of the driving manner on the gathered data. The length of the route averaged 100 km. The highest elevation, amounting to 131 m, was reached on the highway, while the lowest point, equal to 51 m, was encountered in the urban area (Figure 13). Thereby, the general elevation difference totaled 80 m.

**Figure 13.** The elevation pattern throughout the route.

Each drive included stopovers determined by the infrastructure of the particular route's sectors. Naturally, drives along the motorway inheld no stops. However, due to the traffic lights and intersections encountered in the urban and rural sectors, in each drive several dozen stops were registered. As an example, during one of the tests 40 stops were enforced in the urban area (Figure 14) and 6 ones in the rural route, giving eventually the total of 46 stopovers along the route.

**Figure 14.** Stops enforced by the infrastructure in the urban section along the marked route.

Drives were carried out on the working days at the hours of moderate traffic. They were realized in July 2022. Although the measurements were conducted at an interval of more than two weeks, during the period of varying temperatures, the temperature circled around 25 ◦C when the tests were conducted (Figure 15). During the recordings, the settings of the comfort systems including air conditioning were set at the same level.

**Figure 15.** Ranges on measurement days [based on [34] and authors' own measurements].

#### **5. Research Results**

The presented test results are representative of the two examined cases that differ in the cargo load set in the vehicle's rear compartment. The fundamental research question of this research paper was to define the load impact on the energy consumption in the real driving conditions. For this reason, two extreme cases have been considered. The first one assumed 100% of the maximum load (the addition of the driver weight and the cargo weight equal to 940 kg). As a matter of the second case the cargo area was emptied, thus the only loading constituted the driver's weight. For both cases, full battery charge at the beginning of the drive was assured.

Both rides met the requirements of the test under real traffic conditions (guidelines shown in Table 2). The basic parameters for the proportion of the road in the urban, rural and motorway route are shown in Figure 16. Some differences can be seen in the two runs, consisting especially in the varying values and characteristics of maintaining a constant speed in freeway driving, but this did not adversely affect the fulfillment of the test requirements. Varying driving conditions, traffic volumes are taken into account in the test procedure allowing the two measurements to be compared.

The general number of stops differs between the drives as well as between the particular sections of the route. Such state is a direct result of a road infrastructure, that is, the number of junctions, and naturally of the current traffic intensity. The number of stops during the drives equals respectively: for the test with a 100% of a maximum cargo load—38 stops, and for the test with a 0% of a maximum cargo load—40 stops.

**Figure 16.** The course of RDC test in different driving mode with defining basic parameters for meeting test requirements.

By analyzing parameters essential to determine the energy flow in a vehicle, the authors compiled tests parameterization in terms of a particular drive phase share (acceleration -a+, constant speed—a0, deceleration—a−) and a stopover share. For both drives these values, depicted in Figure 17, are similar and thereby allow us to make a reliable assessment regarding the actual load influence on the powertrain's energy consumption.

**Figure 17.** Comparison of the phase motion share during the RDC test regarding the variable cargo load.

An electric vehicle is characterized by two states of drivetrain operation: the drivetrain consumes or generates energy from/to a high voltage battery. With respect to the route parameters in the real driving condition test, therefore, the time and distance intervals in which the vehicle consumes or generates energy were determined—presented in Figure 18 (periods in which the vehicle does not consume energy from the battery during standstill are not recorded—in most cases, at standstill, the battery is also discharged for vehicle comfort purposes—air conditioning).

**Figure 18.** Parameterization of time- and route-dependent energy consumption and recovery for individual phases of the RDC test.

For the both measurement runs, the highest energy recovery values are determined for urban driving conditions, but it should be pointed out that the procedure counts energy recovery/consumption with respect to vehicle speed, so any braking from highway or suburban route speeds automatically enters into the sum of energy recovery for suburban and urban routes, respectively. Nevertheless, it should be noted that in each case the loaded vehicle recorded higher shares of both time and distance of energy recovery, which is confirmed by the energy flow results shown in Figure 19. Greater time or distance of energy recovery resulting also in higher values of recovered energy to the battery did not result in lower energy consumption, as higher vehicle load results in higher energy consumption in the acceleration phase. The higher the speed of the vehicle, the smaller this difference is between runs. In city driving conditions, energy consumption is almost 20% higher for a loaded vehicle than for an empty one. When driving on the highway, this difference

decreases to about 8%. However, taking into account the higher energy recovery for a vehicle loaded with a mass of cargo, these differences decrease in the total energy flow.

**Figure 19.** Energy consumption balance in terms of different cargo load.

A loaded vehicle is characterized not only by the total amount of energy consumed at a higher level than a vehicle moving unloaded. Also, the individual operating points (energy intensity of the drivetrain) reach higher values, which is noted in area 1 in Figure 20. It can also be seen that the temporary energy recovered to the battery during braking is higher (area 2 in Figure 20) compared to the unloaded vehicle. Despite the unloaded vehicle reaching higher speeds on the highway, the energy flow is at a lower level (area 3 in Figure 20).

**Figure 20.** Energy flow areas segmented by speed ranges for different vehicle payload levels.

Based on the above short-term energy consumption maps, the maximum ongoing energy consumption was determined, which indirectly determines the use of the propulsion system. Due to the limitations of the OBD system's measurement monitor, the drive engine's operating parameters were not determined in the current work (this will be done in future work). Instead, the maximum values presented indicate that the energy consumption from the battery in practically every speed range is higher for a loaded vehicle (Figure 21).

**Figure 21.** Maximum values of energy flow in speed intervals steps of 10 km/h.

The greatest energy recovery is realized in urban speed intervals, but this is due to the frequency of braking in urban driving conditions. Instantaneous maximum energy recovery values are highest in the 60–90 km/h speed range. Energy recovery for speeds below 10 km/h is marginal, so below this speed it is necessary to use the vehicle's conventional braking system.

#### **6. Summary**

The presented research made it possible to determine the usability of an electric delivery vehicle in real traffic conditions with extreme load options. The conclusions of the presented work are presented below:


**Figure 22.** Effect of cargo weight on estimated range in different phases of the RDC test.

Based on the research presented, guidelines and conclusions were determined for transportation companies interested in modernizing their vehicle fleets:


**Author Contributions:** Conceptualization, W.C. and W.A.; methodology, W.C.; formal analysis, W.C. and W.A.; investigation, W.C. and W.A.; writing—original draft preparation, W.C. and W.A.; visualization, W.C. and W.A.; writing—review and editing, W.C. and W.A.; supervision, W.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Poznan University of Technology, grant 0415/SBAD/0337.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** The authors of this article would like to thank Toyota Professional Bo ´nkowscy for the provision of a vehicle for research.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Abbreviations**


#### **References**


**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

**Andrzej Szałek <sup>1</sup> , Ireneusz Pielecha 2,\* and Wojciech Cieslik <sup>2</sup>**


**Abstract:** The search for fossil fuels substitutes forces the use of new propulsion technologies applied to means of transportation. Already widespread, hybrid vehicles are beginning to share the market with hydrogen-powered propulsion systems. These systems are fuel cells or internal combustion engines powered by hydrogen fuel. In this context, road tests of a hydrogen fuel cell drive were conducted under typical traffic conditions according to the requirements of the RDE test. As a result of the carried-out work, energy flow conditions were presented for three driving phases (urban, rural and motorway). The different contributions to the vehicle propulsion of the hydrogen system and the electric system in each phase of the driving route are indicated. The characteristic interaction of power train components during varying driving conditions was presented. A wide variation in the contribution of the fuel cell and the battery to the vehicle's propulsion was identified. In urban conditions, the share of the fuel cell in the vehicle's propulsion is more than three times that contributed by the battery, suburban—7 times, highway—28 times. In the entire test, the ratio of FC/BATT use was more than seven, while the energy consumption was more than 22 kWh/100 km. The amounts of battery energy used and recovered were found to be very close to each other under RDE test conditions.

**Keywords:** hydrogen vehicle; energy flow; hybrid powertrain; real driving conditions

#### **1. Introduction**

The use of hydrogen for energy production can be particularly important for industries that are difficult to convert to electric power. This is especially relevant for transportation and industrial production. Currently, most hydrogen is produced from natural gas without CO2 capture during production (CCS—Carbon Capture and Storage). Beyond 2030, hydrogen production from this source with CO2 capture is not expected to increase significantly, as this process will only become cost-competitive when CO2 emission fees are around USD 90 per ton. In contrast, hydrogen from renewable electricity is and will only be cost-effective if low-cost excess electricity is used. Furthermore, it is assumed that in major hydrogen-consuming regions, hydrogen production from biomass will only play a minor role [1].

Depending on the raw materials used in hydrogen production and the amount of CO2 emissions accompanying this process, the produced hydrogen is labeled by colors. Gray hydrogen is produced from fossil fuels, and the associated CO2 is released into the atmosphere. When a process is used to capture CO2 that is infused, for example into a mine shaft, the hydrogen is referred to as blue. If renewable energy and a CO2-free process are used to produce hydrogen, the resulting hydrogen will be referred to as green hydrogen.

For producing hydrogen from fossil fuels, steam reforming and gasification processes are used. The efficiency of these processes, their mass scale of production and the inexpensive price of raw materials result in a low price of hydrogen. On the other hand, however, they require additional hydrogen purification processes. For hydrogen produced from

**Citation:** Szałek, A.; Pielecha, I.; Cieslik, W. Fuel Cell Electric Vehicle (FCEV) Energy Flow Analysis in Real Driving Conditions (RDC). *Energies* **2021**, *14*, 5018. https://doi.org/ 10.3390/en14165018

Academic Editor: Woojin Choi

Received: 19 July 2021 Accepted: 11 August 2021 Published: 16 August 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

fossil fuels to have a purity above 99%, it must be purified in an enrichment step. This technology is currently used on an industrial scale primarily as a pressure swing adsorption (PSA). The contamination of hydrogen with hydrogen sulfide has a huge impact on the durability of fuel cells, while the carbon monoxide content affects the voltage generated by the cell.

Current hydrogen production is for chemical applications where it is fully consumed. The demand generated by transport using hydrogen will be covered by the newly established production facilities. The processes used there qualify the product as green hydrogen, giving the desired effect of zero-emission transport at the same time.

A dominant process in producing green hydrogen is electrolysis. As a result of water electrolysis, hydrogen and oxygen are extracted with very high purity, above 99.999%. This fact is used in direct hydrogen production on the spot of the hydrogen fueling station for fuel cell vehicles, without the need for further purification. However, to obtain such pure hydrogen, the water must be preconditioned. The current energy efficiency of hydrogen production by electrolysis is about 75%.

According to the International Energy Agency [1], the structure of world hydrogen production consists of about 48% hydrogen produced from natural gas, 30% from oil and 18% from coal. The remaining 4% is produced by the electrolysis of water.

Hydrogen has a significantly higher energy density value than batteries (in terms of mass and volume), which benefits the vehicle storage capacity and affects the driving range of the vehicle. Taking these advantages into account, hydrogen fuel cells or internal combustion engines powered by hydrogen can be used in passenger cars, vans, trucks buses and other means of transport (Figure 1).

**Figure 1.** Comparison of range and payload for hydrogen and battery technology in means of transportation [2].

The BEV systems can be used in small passenger vehicles where the daily mileage limit is quite low. With respect to trucks, the use of FCEVs starts to be very beneficial. Fuel cells require far fewer raw materials in the production stage than electrochemical batteries. An additional advantage is the lack of the use of cobalt and the limited use of platinum (compared to internal combustion engine vehicles).

The current price of hydrogen for end-user transport in Europe ranges from EUR 5 to EUR 9.5 per kg, depending on the region. The lowest price is due to the fact that it is produced as a waste product in industrial chemical processes, while the highest price is a contractual price intended to equate the cost of operating a fuel cell car with a spark ignition (SI) engine.

According to the Hydrogen Council [3], the price of hydrogen for fuel cells will decrease by about 60% for the end user over the next decade. This will occur in regions with access to cheap natural gas and the ability to store captured CO2. In addition, with an increased demand for hydrogen, the cost of hydrogen supply over the coming decade

could decrease by as much as 70%. As a result, the cost of distributed hydrogen in 2030 could be in the range of USD 4.5–6 per kg. A comparative analysis of refueling vehicles with conventional fuels, hydrogen and recharging batteries at the filling station shows (Figure 2) that this time is significantly shorter for conventional fuels and hydrogen than electric vehicles, while hydrogen provides a much greater driving range than in the case of electric vehicles. Additional factors favoring hydrogen as a fuel are the investment costs associated with the construction and size of refueling stations.

**Figure 2.** Comparison of refueling performance and investment rates for traditional and near-future fuels [2].

According to the Hydrogen Council, the CO2 emission of hydrogen pathways (the well-to-tank stage) from natural gas via SMR (steam methane reforming) was ~75 g/km, accounting for ~60% of the total CO2 emissions of a FCEV from lifecycle perspective [4]. Most hydrogen today is produced from fossil fuels and emits carbon (grey hydrogen). For producing low-carbon hydrogen from natural gas with CCS, the following two technology options exist: steam methane reforming (SMR) and autothermal reforming (ATR) [3]. SMR combines natural gas and pressurized steam to produce syngas, which is a blend of carbon monoxide and hydrogen. ATR combines oxygen and natural gas to produce syngas. This process can easily capture up to 95% of CO2 emissions. ATR technology is typically used for larger plants compared with SMR technology. Based on the data presented in [5], CO2 emission during hydrogen production is (kg CO2−e/kg H2): coal gasification (no CCS)—12.7–16.8; coal gasification and CCS (best case)—0.71; SMR (no CCS)—8.5; SMR and CCS (best case)—0.76.

The data compiled by the International Council on Clean Transportation Europe [6] show that the average real-world fuel (kg) and electricity consumption (kWh/100 km) values for lower medium and SUV segment cars registered in the European Union are, respectively, BEV: 20.6 and 21.9 kWh and FCEV: 1.0 and 1.2 kg.

In a study, the authors of [6] stated that the life cycle for GHG emissions of average gasoline- and diesel-powered ICEVs (internal combustion engine vehicle) are very similar and range from 226–227 g CO2 eq./km for small, 245–246 g CO2 eq./km for lower medium and 266–288 g CO2 eq./km for SUV segment cars. The emissions from FCEV vehicles looks similar to the following: of medium segment, 202 g CO2 eq./km (from natural gas) and 55–60 g CO2 eq./km (from renewable hydrogen). However, the data presented in [7] show that in some European countries, the amounts of the average carbon footprint over a lifetime (segment D) are significantly different: Germany—426 g CO2 eq./km and France—112 g CO2 eq./km. This is mainly due to the way in which hydrogen is produced. When the electrolysis is powered by 100% renewable energy, the gain in emissions from hydrogen production makes it possible to reach the BEV level (80 g CO2 eq./km).

As hydrogen in gaseous form has a very low density (0.089 kg/m3) and is significantly lighter than air, it is usually stored compressed. In vehicle propulsion applications, to increase the energy density, two standards are usually used for hydrogen storage pressure, that is 35 MPa, which corresponds to a density of 23 kg/m<sup>3</sup> and 70 MPa, which corresponds to a density of 38 kg/m3. For a pressure of 35 MPa, the volumetric energy density of hydrogen is 2.8 MJ/dm3, while for a pressure of 70 MPa, the energy density is 4.7 MJ/dm3.

Hydrogen fuel cell power cars started to reach the US consumer market already in 2014. Official U.S. sales of Hyundai's cars began in June 2014, Toyota's in October 2015 and Honda's in December 2016 (primarily in the state of California).

"Global Market for Passenger Hydrogen Fuel Cell Vehicles" conducted a study at the beginning of the HFCV sale, which projected that by the end of 2020, global sales would amount to more than 27,500 passenger cars powered by hydrogen fuel cells. In 2020 alone, 8500 units were sold [8]. A barrier to the development of this drive has been identified as the lack of available hydrogen refueling infrastructure. The report also indicated that sales of hydrogen-powered cars and SUVs will increase in the coming years. Last year, more than 8500 of such vehicles were sold, which was the highest annual sales rate ever recorded. It should be noted that such high sales in 2020 were achieved despite the huge economic slowdown experienced by the automotive industry during the SARS-CoV-2 pandemic. Consequently, sales of passenger cars and SUVs, light commercial vehicles and full-size trucks and buses are expected to grow very rapidly in the coming years [8].

In 2020, the global number of hydrogen refueling stations was 553; it is planned that in 2021 this number will increase by another 221 stations. In Europe, there are 200 stations (including 100 in Germany), in Asia—275 and in North America—75. The most dynamic development of this technology is observed in Germany, China, Korea and Japan [9].

#### **2. Analysis of Hydrogen Usage in Internal Combustion Engines and Fuel Cells**

The automotive deployment of hydrogen is currently in two application areas (a) as a fuel in internal combustion engines and (b) as a fuel in fuel cells.

Research on hydrogen-powered internal combustion engines began in the 1930s [10]. A broad spectrum of categorization of a hydrogen internal combustion engine (HICE) based on typical injection and ignition strategies was presented by Yip et al. [11]. Typical solutions involve the indirect injection of hydrogen into the intake tract. The second technical solution is the direct injection of hydrogen into the cylinder [12] or the use of both variants [13]. It is realized in spark-ignition [14] and compression-ignition engines as well.

Smirnov and Nikitin [15] conducted studies of hydrogen ignitability in closed chambers. Models of hydrogen combustion were proposed and verified with reference to pre-mixed and non-premixed combustion and detonation models.

One form of using hydrogen in an internal combustion engine is its co-combustion with the following other fuels (dual–fuel systems): gasoline [16], diesel [17], natural gas [18,19], methanol [20,21] or as an additive to other fuels (butanol [22], natural gas [18] or fuel mixtures [23]).

Simulation studies of co-combustion of hydrogen with diesel fuel by Babayev et al. [17] indicate that (a) compressed ignition hydrogen reacting jets are fundamentally different from diesel jets, (b) both the free-jet and the global mixing modes govern the compressed ignition hydrogen combustion cycles and (c) jet-mixing combustion is more effective and should be maximized in compressed ignition H2 engines.

A common solution is to use fuel cells together with internal combustion engines in Range Extender systems. Such a solution presented by Chubbock and Clague [24] involves a package of two fuel cells with a total power of 7.8 kW (the FC power mass index is 0.2 kW/kg) and a tank for storing 1.5 kg of hydrogen. The system uses a three-cylinder internal combustion engine with a displacement of 660 cm3 and a power output of 30 kW (operating as a power generator system).

The fuel cells used in the first prototype vehicles (in 2002) achieved a volumetric power factor of 1.0 kW/dm<sup>3</sup> with a mass power factor of 0.75 kW/kg [25]. In the FCHV model (in 2008), these ratios were 1.45 kW/dm3 and 0.9 kW/kg, respectively. The first-generation Toyota Mirai had values of 3.1 kW/dm<sup>3</sup> and 2 kW/kg, while the new generation of the Mirai vehicle achieves 5.4 kW/dm<sup>3</sup> (4.4 kW/kg excluding end plates) and 5.4 kW/kg, respectively [26].

Honda used 130 kW fuel cells in the Clarity model, for which the volumetric and mass power factors were 3.1 kW/dm<sup>3</sup> and 2.0 kW/kg [27,28].

Although the parameters and metrics of fuel cells are known, there is a lack of analysis on energy consumption in typical road tests by fuel cell powered automotive vehicles. There are few publications on different vehicles [29] or other research tests [30]. Therefore, the aim of this paper is to fully analyze the energy flow in the Real Driving Condition test (based on the Real Driving Emissions test) and, additionally, to analyze the use of fuel cells, a high-voltage battery and an electric motor.

#### **3. Materials and Methods**

#### *3.1. Research Objects*

The research was conducted using a Toyota Mirai first-generation vehicle (Table 1). The vehicle uses components from Toyota's hybrid vehicle models mass-produced since 1997. These components consisted of the vehicle's power management unit, known as the power controller and the voltage converter, both used from a third-generation Prius model; the traction electric motor was taken from a Lexus RX 450h hybrid model; and the high-voltage battery was taken from a Toyota Camry model.


**Table 1.** Toyota Mirai powertrain system [31,32].

The vehicle was equipped with a stack of 370 fuel cells creating a 114-kW power output. Two hydrogen tanks with a pressure of 70 MPa were used in the vehicle (Figure 3). This produced the highest unit mass power density of compressed hydrogen. The voltage from the fuel cell stack is converted to 650 V and powers an AC electric motor.

**Figure 3.** Toyota Mirai hydrogen system component layout (based on [33]).

The generation of the fuel cell used in this model has a volumetric energy density 28 times higher than that of the first generation used by Toyota. The first generation had a volumetric energy density of only 0.11 kW/dm3, while the one used in the tested Mirai model is 3.1 kW/dm3. This was achieved, partly due to the design of the cell stack with a configuration that allows internal self-humidification, using the circulation of water produced in each cell. This feature eliminated the need for a humidifier, significantly reducing the volume of the entire cell stack.

The vehicle has two tanks of 120 and 122 dm3, holding a total of 5 kg of hydrogen (Table 2). The calculated ratio of the mass of hydrogen, at maximum hydrogen filling, to the empty mass of the tanks is 5.7%.

**Table 2.** Parameters of hydrogen tanks used in Toyota Mirai [34].


The use of the Fuel Cell Boost Converter (FDC) from the hybrid model in the Mirai enabled the use of an inverter and an electric traction motor, already used in series-produced hybrid vehicles. In addition to these components, an Intelligent Power Module (IPM) was also used [33].

The high-voltage battery used in this model has the same function as in the hybriddrive models. Its main role is to accumulate the energy regenerated during braking [35]. The energy stored in the battery is used to power the powertrain during vehicle startup and during acceleration [36]. This keeps the instantaneous hydrogen consumption at a very low, or zero, level compared to if the energy was generated by the fuel cell alone. Since the mass of the vehicle is 1850 kg, the designers used a 244.8 V traction battery to ensure adequate performance. Since Toyota uses nickel-metal hydride batteries for a majority of its hybrid models, the same battery was used for the model Mirai. The battery structure contains 34 modules with 6 cells of 1.2 V each.

#### *3.2. Research Equipment and Methodology of Determination of the Energy Flow*

The measurements were performed using a specialized, dedicated diagnostic tester utilizing the OBD (on-board diagnostics) connector. The research used data provided by one of the vehicle systems—the hybrid control. This system operates using selected vehicle data, fuel cell stack, parameters of the electric motor and the parameters of the high-voltage battery. The vehicle driving conditions were determined based on the measurements of the vehicle speed and the data sampling time. The resolution was 1 Hz.

The assessment of the energy flow was carried out based on the measurements of the engine speed and load, the speed and torque of the electric motors/generators, the battery voltage and the current (including the boost voltage).

Using the above measurement data, the following quantities were determined:

• energy flow (urban, rural, motorway):

$$
\Delta \mathbf{E}\_{\mathbf{i}} = \int\_{\mathbf{t}=0}^{\mathbf{t}=\mathbf{t}\_{\text{max}}} \mathbf{U}\_{\text{BAT}} \cdot \mathbf{I}\_{\text{BAT}} \, \mathbf{dt} \tag{1}
$$

the instantaneous energy flow values ΔEi were divided in accordance with the following criteria:

• discharging (urban, rural, motorway):

$$
\Delta \mathbf{E}\_{\rm dis} = \int\_{t=0}^{t=t\_{\rm max}} \mathbf{U}\_{\rm BAT} \cdot \mathbf{I}\_{\rm BAT} \mathbf{d}t \; (\text{if } \Delta \mathbf{E}\_{\rm i} < 0) \,\tag{2}
$$

• charging (urban, rural, motorway):

$$
\Delta \mathbf{E}\_{\rm ch} = \int\_{t=0}^{t=t\_{\rm max}} \mathbf{U}\_{\rm BAT} \cdot \mathbf{I}\_{\rm BAT} \mathbf{d}t \text{ (if } \Delta \mathbf{E}\_{\rm i} > 0 \text{ and } \mathbf{T}\_{\rm reg} \ge 0),
\tag{3}
$$

• regenerative braking (urban, rural, motorway):

$$
\Delta \mathbf{E\_{reg}} = \int\_{t=0}^{t=t\_{\text{max}}} \mathbf{U\_{BAT}} \cdot \mathbf{I\_{BAT}} \,\mathrm{dt} \left(\text{if } \Delta \mathbf{E\_i} > 0 \text{ and } \mathbf{T\_{reg}} < 0\right),
\tag{4}
$$

where UBAT—voltage (V), IBAT—current (A), dt—time interval (h), Treg—braking torque (Nm); • boost value (urban, rural, motorway):

$$\text{boost} = \frac{\text{U}\_{\text{HV}}}{\text{U}\_{\text{LV}}} \tag{5}$$

where ULV—low voltage side (V) and UHV—high voltage side (V).

#### **4. Results**

#### *4.1. Driving Test Evaluation*

The main problem of a constantly developing industry is its negative impact on the environment. Transportation is one of the most rapidly changing industries, and it significantly affects the concentration of hazardous substances in the air. To reduce the impact of vehicles on the environment, increasingly stringent standards for exhaust emissions are being introduced and solutions are being developed to minimize vehicle emissions. Exhaust emission standards are set to control the pollutants emitted from automotive vehicles around the world. Exhaust emission values are measured under conditions in an established type of the approval test. This part of the vehicle certification process is responsible for the environmental performance of the vehicle and is the same for all passenger cars. The course of the test corresponds to the most likely road conditions, and the tests performed, which are the same for all vehicles, authorize the comparison of emission results between them. Nowadays, the focus is more and more on road testing, i.e., testing under real driving conditions. These tests have now been integrated into European Union regulations under the name RDE (Real Driving Emissions) [37,38]. These are made

to best reflect the actual operating conditions of the vehicle in terms of environmental aspects. The research presented in this paper omits the analysis of exhaust emissions (which, in a fuel cell vehicle, is zero), focusing on the analysis of the energy consumption of a modern propulsion system based on RDE test standards. With this in mind, the authors refer to this test by the acronym RDC (Real Driving Conditions) [39,40]. Due to increasing electrification of vehicles, comparative work on the energy consumption of propulsion is extremely important for the development of the transportation field. The RDC (RDE) test procedure is universal within the European Union and can be carried out on selected sections of a road that meet the basic requirements. The route is divided into three sections corresponding to the speed of urban, rural and motorway driving conditions. The test was performed with the FC vehicle in Warsaw (Poland) and met all the requirements, as shown in Figure 4.

**Figure 4.** Course of the RDC test with characteristics phases (S = 102.8 km, t = 114.5 min).

#### *4.2. State of Charge (SOC) Change Analysis*

The drive system of the Toyota Mirai is equipped with a high-voltage nickel-metal hydride battery. During driving, the battery is charged and discharged due to the characteristic parameters of the route, such as the amount of acceleration and braking in a given section of the route. The energy recovered during braking can be reused to power the vehicle, as is the case in hybrid and electric vehicles. The study identified the areas with the highest and lowest average battery charge levels (Figure 5a).

**Figure 5.** Changes in battery SOC: (**a**) with averaged values for travel phases; (**b**) in relation to travel speed.

As the driving speed increases, resulting in less braking zone, the high-voltage battery reaches lower average charge levels. Of course, this value is dependent on the characteristics of the route, since a single slowing of the vehicle results in a significant increase in recovered energy. Despite the direct response of the level of charge to vehicle driving parameters, the total SOC fluctuation area is in the range of 53–60%, which is a small range of the full battery capacity of 1.6 kWh. Slight variations of the SOC are characteristic of hybrid powertrains, where the engine (in the case of the vehicle under study, a fuel cell) is the main source of propulsion. The battery is supposed to mainly store energy from recovery modes or excess energy production by the powertrain.

The largest changes in battery charge are recorded in the range of driving speeds up to 60 km/h (which corresponds to urban driving speeds), where the highest average charge was recorded at the same time (Figure 5b). The change in battery charge level oscillates in the range of ΔSOC = 7.06% over the entire test interval.

#### *4.3. Powertrain Performance Evaluation*

In a hybrid vehicle, the energy for propulsion comes from two sources. The range of the propulsion power source in the intervals of each stage of the RDC test route was determined in the tested vehicle. The battery and fuel cell power consumption conditions shown in Figure 6a,b indicate areas of battery-only operation and areas of dual power source cooperation in the vehicle drive. At low vehicle speeds in the 0–10 km/h range, the propulsion energy comes from the battery. Higher vehicle speeds result in the fuel cell starting to work in the power generation process. An increase in vehicle speed increases both the instantaneous maximum values of the powertrain energy demand and the average values in each speed window with an interval of every 10 km/h (Figure 7).

**Figure 6.** Powertrain usage conditions: (**a**) battery, (**b**) fuel cell; with a specific subdivision of the test phases.

**Figure 7.** Average and maximum changes in battery (discharge and regeneration) and fuel cell contributions during each phase of the RDC test.

Due to the individual driving parameters, some speed ranges recorded lower energy consumptions, however, the justification for these results should be found in the temporary driving conditions, for example, the lowest average energy values were obtained in the speed range 41–50 km/h, this speed usually occurs only in transition states between acceleration and deceleration to the maximum speed of the urban speed range. Over a wide range of speed ranges, similar energy recovery values were recorded for both the urban and rural sections, indicating the versatility of energy recovery at varying speeds.

#### *4.4. Evaluation of Electric Drive Operating Conditions and Energy Consumption*

The energy to operate the vehicle comes mainly from the fuel cell, transient situations caused by acceleration additionally consume energy from the high-voltage battery, but in total, due to energy recovery to the battery during braking, the energy flow from this source becomes neutral. The small changes between EC\_ALL and EC\_FC are due to the inclusion of changes in battery discharge (EC\_BATT) and battery recharge due to recovery regenerative braking (EC\_REC), according to the following equation:

$$\text{EC\\_ALL} = \text{EC\\_FC} - \text{EC\\_BATT} + \text{EC\\_REC} \tag{6}$$

In this way, the difference between EC\_ALL and EC\_FC is not significant because the battery usage and recharge is close to zero. These conditions are illustrated in Figure 8.

**Figure 8.** Energy consumption conditions in the RDC test phases (ECU—energy consumption in urban phase, ECR—energy consumption in rural phase, ECM—energy consumption in motorway phase).

Confirmation of the above statement regarding the main use of the fuel cell for vehicle propulsion is provided by an analysis of the energy flow shares (discharge and charge) per vehicle speed for the battery (Figure 9). It can be concluded that in selected speed ranges, the regenerated energy is equal to the energy consumed during driving or acceleration. However, it should be remembered that this graph only shows the energy flow from the battery and the fuel cell is also used for propulsion, which generates much more energy to drive the vehicle. The drive characteristics also indicate that braking energy recuperation only occurs until 8 km/h, below which the vehicle decelerates using the conventional braking system. The highest energy consumption from the battery was recorded for accelerating the vehicle from a standstill when the fuel cell is not yet generating the required propulsion power. In the presented single RDC test, the total energy recovered is 322 Wh more than the energy consumed; therefore, the energy recovery system is highly efficient (the battery does not require an external source of charge to obtain the energy needed to drive the vehicle—part of the energy also comes from the operation of the fuel cell, what is indicated later in this article).

**Figure 9.** Shares of battery energy use during discharge and charge in relation to driving speed.

Complementing the presented summary evaluation of the powertrain during the RDC test is a discussion of energy flow on selected instantaneous single vehicle acceleration and deceleration states. Based on Figure 10, it is possible to describe the following characteristic operating points of the drive system:


**Figure 10.** Interaction of powertrain components during driving of Toyota Mirai (selected events on road).

**Figure 11.** Analysis of a selected single acceleration process of a FC vehicle.

Regardless of the energy source, the wheel propulsion is provided entirely by the electric motor. It is, therefore, important to recognize the operating conditions of the drivetrain (Figure 12). During the entire RDC test, the powertrain generates 83.7% of the vehicle's propulsion and 16.3% of the energy is recovered during braking. During both propulsion and braking of the vehicle, the powertrain operates within the voltage range of mainly 300–350 V—achieving more than 60% of the total time share. Individual operating points generate higher voltages in the range of 350–652 V; however, the total share of these values is much lower (these are noted at intervals of higher vehicle speeds or higher powertrain loads). The maximum torque achieved during the test was 216 Nm, which is 65% of the max torque claimed by the manufacturer; therefore, the drivetrain in the RDC test does not require maximum torque to complete the run. The regenerative braking characteristics indicate a constant braking torque in the electric motor speed range 1500–9000 rpm at the level of 15 Nm. Regenerative braking is only possible down to a speed of about 7 km/h.

**Figure 12.** Characteristics of an electric motor in relation to its operating voltage.

The charging and discharging conditions of the high-voltage battery are shown in Figure 13. Although the nominal voltage is reported as 244.8 V, its operating conditions indicate much larger positive fluctuations around this value. The minimum value fluctuates around 240 V, but the maximum value far exceeds 300 V. The operating conditions of the battery indicate that it is possible to receive about 26 kW of power when discharged. During its charging, much higher power values were obtained (more than 32 kW), indicating slightly different charging and discharging conditions (with similar current values); the voltage variations are around 20 V.

**Figure 13.** Characteristics of a high voltage battery.

The version of the first-generation Toyota Mirai powertrain presented in this paper includes a Fuel Cell Boost Converter. This is a significant change from the powertrain presented in 2008 (designated as Toyota FCHV adv). This means that the fuel cell using boost can largely self-power the vehicle's electric motor. The operating conditions in Figure 14 indicate that at a fuel cell current value of about 100 A, the converter maintains a voltage of 650 V. For current values from about 200 A, the converter converts voltage from the cell to the maximum level of 650 V. The voltage–current characteristics of the fuel cell indicate voltage values of 200–300 V at no load to about 200 V at maximum current values of over 350 A. The power characteristics of the fuel cell do not have a typical maximum; therefore, increasing the current increases its power. Thus, applying voltage amplification at a specific current value, in this case at about 100 A, effectively increases the power directed to the electric motor.

**Figure 14.** Current–voltage characteristics of a fuel cell and its voltage converter.

An evaluation of the total energy flow in the Toyota Mirai drive system is shown in Figure 15. The contribution of the HV battery in the individual phases of the RDC test is not large—as the driving speed increases, the contribution decreases. For the entire test, the share of battery utilization is about 13%. The share of energy recovery to the battery (regenerative braking and fuel cell charging) is slightly higher. The larger values of energy recovered to the battery apply to each phase of the test—approximately 0.6 percentage points on average. This shows that in the entire driving test, slightly more energy was supplied to the battery than was used. Energy flow analysis shows the vehicle consumed 22.285 kWh in the test. However, the fuel cell "produced" 22.60 kWh, which is indicated in Figure 15—as 101.5% of the total energy consumed. This difference is due to the energy recovery to the battery. Summarizing the energy flow in the RDC test, it should be stated that the contribution of the fuel cell to the vehicle's propulsion is more than 70%. The rest is half, indicating the battery's contribution and energy recuperation.

**Figure 15.** Energy consumption conditions for the RDC test phases and the entire RDC test.

#### **5. Conclusions**

Modern hybrid drives that use a fuel cell instead of an internal combustion engine as the main source of propulsion are now a trend in the development of future zero-emission automotive. The advantage of fueling the vehicle quickly is a key advantage over electric vehicles, which take much more time to charge depending on the charging type. Fuel cells are a multipurpose source of electricity that can be converted to electric drive in basically any type of propulsion system; therefore, the research presented above is important because

of the recognition of the energy balance of such vehicles. The widespread use of fuel cells in automobile, truck and even maritime transport brings significant benefits. However, the global use of this type of propulsion depends on the development of a hydrogen re-fueling infrastructure. The study determined at what ranges the drive is realized with a fuel cell, and in what ranges a high-voltage battery is engaged. The operating conditions of these systems have been specified.

The above analysis of the operating conditions of the hydrogen vehicle propulsion system under real traffic conditions (according to the RDE test procedure) indicates the following:


**Author Contributions:** Conceptualization, I.P. and A.S.; methodology, A.S., I.P. and W.C.; validation, I.P., W.C. and A.S.; formal analysis, I.P., W.C. and A.S.; investigation, I.P.; resources, A.S.; data curation, I.P. and A.S.; writing—original draft preparation, I.P., W.C. and A.S.; visualization, I.P., W.C. and A.S.; supervision, I.P. and A.S.; project administration, I.P. and A.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** The authors wish to thank Toyota Motor Poland for providing the vehicles for the road tests.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

