n. 2/2021 35 TECHNOLOGY me taglio e mulching dell’erba, con trincia a coltelli o elicoidale, biotriturazione, aspirazione foglie e trasporto materiali) e di quella stradale (per piccole escavazioni e movimentazioni con benna e pala frontali e rimozione neve, anche con turbina), il costruttore mette a disposizione una serie di attrezzi per alcune operazioni tipiche di campo aperto, come una zappatrice (anche in versione interrasassi), un piccolo coltivatore e un erpice rotante, eventualmente completato con una seminatrice. La velocità massima del veicolo è di 16 km/h, e può affrontare pendenze sino al 15%. Oltre ad una presa di corrente a bordo da un chilowatt per l’attacco di utensili esterni, è disponibile anche una “pensilina” dotata di pannelli fotovoltaici e inverter con accumulatore, per rendere indipendente (e gratuita) la ricarica del pacco batterie. Analogamente, la Gianni Ferrari di Reggiolo (RE) ha in produzione due modelli di trattorini rasaerba full-electric, rispettivamente con piatto di taglio ventrale (GTM+) e frontale per mulching (GSR+). In particolare, quest’ultimo monta 3 lame da 112 cm di larghezza di lavoro, che ruotano a motors of 24 HP overall, powered by a 48 V Li-ion battery pack with 18 kWh capacity: the first is dedicated to traction, while the second is used to drive the connected machines. Recharging the batteries takes just over 8 hours with a power of 1.2 kW, but the time can be halved if the available power doubles. In addition to typical processing in the maintenance of green areas (such as cutting and mulching grass, with blades or helical mulchers, biocrushing, suction of leaves and transport of materials) and road maintenance (for small excavations and movements with bucket and front shovel and snow removal, also with turbine), the manufacturer offers a series of tools for some typical open field operations, such as a hoe (also in the stone burier version), a small cultivator and a power harrow, possibly completed with a seeder. The maximum speed of the vehicle is 16 km/h, and it can tackle slopes up to 15%. In addition to a one-kilowatt on-board power socket for attaching external tools, there is also a "shelter" equipped with photovoltaic panels and an inverter with accumulator, to make the recharging of the battery pack independent (and free of charge). "Similarly, Gianni Ferrari of Reggiolo (RE) has two models of full-electric lawn tractors in production, one with a ventral cutting deck This is a fundamental characteristic of batteries, and refers to the amount of energy that can be stored per unit mass (or volume). The main reason that still hinders a wide diffusion of electric vehicles is precisely this peculiarity, which still "pays the price" compared to fossil fuels. For example, when it is subjected to combustion in diesel engines (i.e. its lower calorific value is taken into account), one kilogramme of diesel develops almost 12 kWh of energy, compared to 0.3-0.4 kWh of energy stored in the same mass of the best current battery. In other words, in principle the energy density of diesel fuel is a good 30-40 times higher than that of the most advanced batteries available today. For a more realistic comparison, however, it is also necessary to take into account the actual use of the two solutions applied to vehicles, i.e. to consider the important energy losses of the endothermic engine due to its normal operation (substantially in the form of heat, generated by internal friction and contained in the exhaust fumes), much more intense than the electric engine. In addition, the latter’s typical performance means that the overall performance of the vehicle is significantly better than when operating with the endothermic powertrain. Ultimately, the advantage of the fossil fuel supply is reduced to 12-15 times, which however remains a huge "gap" for the current batteries, especially if we think of agricultural applications, where an optimal autonomy of the machine, i.e. the tractor, should provide up to 10-12 hours of heavy work per day (for example to perform a deep plowing). While fossil fuel powered engine technology is now largely mature, battery powered electric motor technology is evolving and shows great promise in terms of increased efficiency. Many studies are underway for new types (in some cases even revolutionary) of battery, able to greatly increase the energy density. For example, solid electrolyte lithium/ceramic batteries and even more so zinc/air or other metals/air batteries bode well for their development, not only because of the increase in energy density, but also because of other multiple characteristics that must necessarily be considered, such as recharge times, service life, performance at low and high temperatures, heat dissipation due to the Joule effect, etc. The energy density of batteries Struttura di base delle nuove batterie litio/ceramica e zinco/aria (in questo caso nel formato a pastiglia) Basic structure of the new lithium/ceramic and zinc/air batteries (in this case in tablet format)
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