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Tractor Operates On Sun Power

Solar-powered tractors make sense to John Howe. The extra weight of the batteries adds traction, and the sun is strongest in the summer when tractor use is the greatest. His solar panel-equipped Cub Cadet can pull a 6-ft. harrow or haul a load of hay without burning an ounce of gas.
  "The nine deep cycle batteries add about 500 lbs. to the 1700 to 1800-lb. Cub," says Howe. The battery pack provides the energy equivalent of about half a gallon of fuel, he adds.
  He can do about an hour of heavy tillage or up to 6 hours of stop-and-go work without recharging. A full recharge takes 6 to 8 hours by solar panel.
  Howe knows his solar-powered tractor isn't economically feasible for most farming situations. The author of "The End of Fossil Energy," he built the tractor out of concern for sustainable energy production. He thinks its day will come, as the price of oil is driven higher and the cost of transportation makes local food production more important.
  "If you were doing micro farming with small food plots to feed a community, a small tractor like this is all that would be needed," says Howe.
  He selected a Cub tractor to experiment with largely because of its direct 1-to-1 drive pto. This meant he could tie into the entire drive train, including full use of the transmission, by applying power to the pto end of the straight line drive shaft. Opening the pressure plate stops it from also rotating the crankshaft and pistons.
  He mounted three 175-watt Sharp solar panels with an area of 60 by 100 in. on a roof framework above the entire tractor to supply up to 5 amps@100 volts for 0.5 kwh peak power output. He then mounted the battery packs alongside the front frame. The 10-kilowatt electric engine mounts under the seat and connects to the pto with a cogged belt and two pulleys at a 6:1 ratio. The smaller pulley is a pto shaft extension that Howe machined down to handle the cogged timing belt.
  For added braking power, he also installed a disk brake on the rear drive shaft pulley and installed a separate brake pedal on the tractor to operate it. The extra braking was needed, he says, when pulling large loads.
  To return to use of the gas engine, he simply removes the drive belt and closes the pressure plate. For hydraulic power, Howe mounted a hydraulic pump on the front of the gas motor. When he needs hydraulic power, he removes the spark plugs from the gas engine and disengages the clutch. This allows the electric motor to rotate the crankshaft and the hydraulic motor.
  Howe estimates that he gets 13 1/2 hp with his solar-powered tractor. Key to its efficiency is the $800 pulse width controller. It chops current into very short pulses, which gives the operator very efficient control of power use. The motor itself cost about $500, as did the batteries.
  "I really love it for picking up hay bales and hauling hay," says Howe. "It can haul a huge load of hay up a hill, and any time the sun is out, it's refueling. The solar array acts like a trickle charger."
  Contact: FARM SHOW Followup, John Howe, Howe Engineering Co., 298 McIntire Rd, Waterford, Maine 04088 (ph 207 583-4800; email: howe@megalink.net).


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2005 - Volume #29, Issue #4