Carbon Footprint Enhancement of an Agricultural Telehandler through the Application of a Fuel Cell Powertrain

In recent years, the scientific community has deeply investigated the effects of anthropic activities in terms of environmental pollution, as well as the consequences on human health, climate change and economics [1,2,3,4,5,6]. Indeed, almost all human acitivities involve systems that are sources of emissions. The emissions produced can differ in quantity, depending on the specific pollutant or greenhouse gas under consideration, for the different sectors of anthropic activity. Industry, agriculture and transport sectors are characterized by high emission levels due to the adoption of internal combustion engines, which are required to accomplish several tasks. Indeed, internal combustion engines (ICEs) are one of the major contributors to air pollution, mainly due to fuel extraction processes and by-products of combustion [7,8]. In this context, several efforts are made, both from academic and industrial worlds, to study and develop innovative powertrains with lower emission levels, in order to reduce the impact related to the transport sector [9]. These efforts are supported by policies that will force the introduction of electric and alternatives powertrains as substitutions for their traditional diesel and gasoline counterparts [10]. If this trend already has a clearly visible effect on passenger cars, with several countries experiencing a quick introduction of electric vehicles on the market [11], the sector of Non-Road Mobile Machinery (NRMM) will still be at an earlier stage of electrification, even if studies have demonstrated that these vehicles have a high impact in terms of life cycle emissions [12,13]. The reason for that is related to the operative requirements that these vehicles must fulfill, with high productivity and endurance that represent a barrier to the development of pure battery electric powertrains [14]. As a consequences, several studies focused on hybrid powertrains [15,16,17,18,19]. Indeed, the hybridization of the powertrain allows for a downsizing of the thermal unit, which can lead to a higher efficiency and better fuel economy. Moreover, the adoption of a smaller engine can allow for simplier aftertreatment systems since the emission limits are usually defined according to the rated power of the ICE. As a consequence, different manufacturers have presented prototypes of hybrid off-road vehicles [20,21]. However, hybrid powertrains featuring the presence of an internal combustion engine still produce several harmful pollutants in the exhaust. To overcome this limit, an alternative solution for the electrification of the sector of NRMM is represented by fuel cell powertrains [22,23,24,25,26,27,28]. Fuel cell hybrid electric powertrains have gained attention due to their characteristics that combine the advantage of having approximately zero local emissions with high endurance and low refuelling time [29]. These properties, along with the high energy density of hydrogen, are of particular interest for the sector of NRMM. As a consequence, fuel cells, powered using hydrogen or other fuels, such as ammonia, are a promising solution to decarbonize the so-called hard-to-abate sectors, such as the marimite one [30]. Indeed, fuel cell powertrains can operate for several hours straight, which is a severe operational requirement for off-road vehicles, without having the issue of range anxiety. Moreover, fuel cell systems have higher efficiency with respect to thermal engines; thus, a better fuel economy is expected. From an economical point of view, using hydrogen as fuel can allow for energy independence and self-sufficiency, along with the possibility of defining circular economy scenarios [31]. The most promising type of fuel cell for vehicular applications is the proton-exchange membrane fuel cell (PEMFC), due to its high efficiency, low working temperature, compactness and long operational life [32,33]. However, the benefits of introducing fuel cell systems in terms of greenhouse gases emission reduction strongly depends on the hydrogen production method [34,35,36], with production through steam methane reforming that, at present, is the most adopted one and contributes to more than 60% of the global hydrogen production [37]. Other issues related to fuel cell systems are represented by their high purchasing costs and the inadequate state of the hydrogen refuelling network, which are two of the major challenges that must be addressed in the near future to promote their diffusion [38,39]. From an applicative point of view, fuel cell powertrains can have different topologies. Indeed, to avoid the fast degradation of fuel cells, one or more auxiliary units, generally batteries or supercapacitors, should be introduced to the powertrain to help manage sudden changes in the external load [40]. Indeed, fuel cell degradation is related to start and stop cycles, idling, high power conditions and load changes [41]. With the introduction of other power sources comes the mandatory development of an energy management strategy (EMS) that must determine how the electrical power requested by the electric motor is split among the different units [42]. Given these premises, in the present paper a fuel cell hybrid electric powertrain for a off-road heavy duty vehicle, namely a telehandler, is presented. The specifications of the traditional vehicle under investigation are defined according to existing and commercially available models. In detail, the Merlo Turbofarmer 42.7 vehicle was taken as a reference for the analysis [43]. This vehicle was designed specifically for agricultural applications. These vehicles are characterized by the presence of an hydraulic system for the actuation of the mechanical arm, thus the total load is determined by the sum of the power requested by the driveline and the power requested by the hydraulic system [44]. The powertrain architecture is composed of a PEMFC and a battery pack, with DC-DC power converters for the connection of both the fuel cell and the battery pack with the DC bus. As for the EMS, a simple power follower strategy was developed. Numerical models of both the fuel cell powertrain and the traditional counterpart were built in MATLAB/Simulink. Simulations were carried out to evaluate performances and fuel consumptions, in order to compare the two powertrains. Moreover, the environmental impacts, considering the global warming potential, of the two powertrains were compared using Well-to-Wheel (WtW) coefficients for both Diesel and Hydrogen. This paper is structured as follows: Section 2 introduces the case study and the proposed fuel cell powertrain, Section 3 presents the numerical models used for the simulations, Section 4 describes the EMS and the simulated work scenario, Section 5 shows and discusses the results obtained from the simulations, and finally Section 6 summarizes the conclusions.