Development of a Hand-Held Disk Mower Powered by Solar Energy

ABSTRACT
The current study was conducted to develop a hand held solar powered disk mower by DC motor through a dry battery charged from a solar power plant by modifying a gasoline-powered machine in an attempt to study the possibility of using solar energy instead of fossil fuel for operating agricultural machinery to overcome the deficit of traditional energy resources and reduce the greenhouse gases and its negative environmental impact. The experimental tests included two tests, firstly preliminary test which performed to identify the morphological and mechanical properties of alfalfa, to obtain the required data for developing a hand held mower and selecting its main components that include “DC motor; battery and solar charger controller. As well as, determine the torque requirement for the cutter disk rotating main shaft. Also; study the state of battery charge to the selected suitable battery. Secondly field tests to evaluate the performance rate; efficiency; energy consumption and operating costs of the developed solar powered machine compared with the gasoline powered machine under field conditions. Two main parameters were studied during the field test; cutter disk rotational speed (3600, 6000, 9000 rpm) and Plant density (˂ 6000, 6000-9000, ≥ 12000 plant /m2). The results of the preliminary test indicated that, the alfalfa average stalk height; stalk diameter were 75 cm; 4 mm and the plant density was ranged between 6000 to 12000 plant/m2. The maximum cutting force was 130 N recorded with stalk diameter 4 mm. As well as; the applied torque on the cutter disk shaft recorded when the DC motor fixed directly with the cutter disk ranged between 0.6366 and 0.2546 N.m. The state of charge (S.O.C) of the selected dry battery “12 voltage”, it continue to operate efficiently for about one hour, at charge level 100% "full charge", in which the voltage was 14 V then gradually decreases to the level of 20% "full discharge" then the voltage was 8 volts. The current from the dry battery fluctuated between the maximum of 14 amperes during the cut-off phase to a minimum of 4 amperes during return back (without cutting). The result of field tests indicated that; the actual performance rate with the gasoline powered machine (before modified) was 0.209 fed/h recorded with plant density 6000 plant/m2 and cutter disk rotational speed 3600 r.p.m. on the other hand; the highest actual performance rate (after modification) was 0.088 fed/h recorded at the disk rotational speed 9000 rpm with plant density 6000 plant/m2; and The highest performance efficiency was (85%) recorded with the plant density 6000 plant/m2 at the disk speed 9000 rpm. As well as, the energy requirements for the solar powered machine ranged between 4.431 to 4.454 kw.h/fed. While it was ranged between 15.11 to 19.6 kw.h/fed for the gasoline powered machine. The operating cost was 4.076 L.E/h. and 53.5 L.E/fed; by using the solar powered machine; that reduce the total operating cost L.E/h by 80 % compared with the gasoline powered machine.