Making the Case for Solar-Powered Electric Tractors

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STEVE HECKEROTH
The Heckeroth handmade solar tractor.

It only makes sense to use solar-powered electric tractors for their eco-friendly ways.

The world is clearly
running out of oil and gas, yet most people ignore the
coming crisis. Food production and distribution in the
industrialized world have become so dependent on petroleum
use, it’s hard to imagine how agriculture will function
without this fuel.

Solar Advantage

The most promising option is solar-powered electric
tractors, which offer several advantages over gas
diesel-powered tractors. Electric motors can operate at
more than 90 percent efficiency, while combustion engines
are less than 15 percent efficient. Electric propulsion is
ideally suited to high torque, slow-speed agricultural
operations. Electric motors have only one moving part and
require little maintenance. Internal combustion engines, on
the other hand, have hundreds of moving parts and require a
lot of maintenance.

Electric motors don’t idle, which saves energy. Plus. while
the vehicle is going downhill or braking, an electric motor
can become a generator and return energy to the battery.
This process, called regenerative braking, further
increases the efficiency of electric propulsion and cannot
be duplicated using other technologies. Electric-wheel
motors eliminate the need for an internal combustion
engine, transmission and differential. allowing new options
in the design of tractors. Mounting an electric motor in
the hub creates a self-propelled wheel that can provide new
levels of versatility and visibility.

If an electric tractor is combined with photovoltaic (PV)
charging, whether on the tractor itself in the form of a
solar panel shade canopy or on the roof of a building, no
other fuel source is necessary. Unbreakable PV panels
and PV roofing that can turn any sunny surface into a power
station are now available with a 20-year warranty.

Photovoltaics provide an ideal energy source for
agriculture because the growing season coincides with the
availability of solar energy.

The biggest obstacle to the performance of most electric
automobiles is battery weight. Unlike automobiles,
tractors depend on weight for traction, thus heavy,
deep-cycle, lead-acid batteries that are inexpensive,
recyclable and long-lived can be used to great advantage in
an electric tractor.

In addition to an onboard battery pack between the traction
wheels, auxiliary battery packs can be loaded on the
tractor’s three-point hitches to balance implement weight
and extend operating time. Electric linear actuators
(no-maintenance screwjacks that push and pull) replace less
efficient hydraulics for steering and for positioning the
three-point hitches. The electric tractor can include a
separate power take-off (PTO) motor that can be sized for
specific needs and operate independent of ground speed.

Even now, when gas and oil are still affordable, there are
many applications for a nonpolluting electric tractor
powered from renewable sources. These include greenhouses
and organic farms where air quality must be high; golf
courses surrounded by expensive homes where noise is a
concern; planting and harvesting where very slow speeds are
necessary; and remote control operation where safety is
important. Solar-electric tractors also have multiple
applications in non-industrialized countries, which lack
fossil-fuel infrastructure and low fuel prices. The
electric tractor can also replace petroleum-powered
generators as a mobile power source in remote areas and in
emergency applications.

Because the electric tractor is made from modular
components, it can be assembled in any small shop and does
not require a large, energy intensive manufacturing
facility.

Agriculture as practiced in the industrialized world today
is far from sustainable. Eighty years of petroleum
dependence has degraded Earth’s life support system to the
point where maintaining air, water and soil quality is no
longer enough. Humanity’s survival depends on regaining
environmental quality. The only source of energy capable of
replacing fossil fuels is the source that made them. The
petroleum resource may last another 50 years, but the sun
won’t burn out for 5.5 billion years. Which resource do you
think makes the most sense?

The Electric Ox

The Electric Ox is a towing tractor aimed primarily at
greenhouse and industrial users. The Electric Ox MP
(multipurpose) model adds attachments, such as a mower
deck, rotary sweeper, snow thrower and dozer blade with a
patented system that claims two-minute exchange times. Both
models offer quiet operation and zero source emissions and
are proving popular for grounds maintenance at schools,
hospitals, retirement residences and high-density housing
sites. The Electric Ox is also a good candidate for some
postal routes, warehouses, golf courses, underground
construction sites and airports.

The 790-pound tractor-no oil, gas, engines, transmissions,
belts and pulleyswill turn inside an aisle 10 feet wide,
will tow up to 6 tons of wheeled cargo, and is available
with either a 36-volt or 48-volt battery pack. The
manufacturer says the 36-volt tractor is equivalent to an
18 horsepower to 20 horsepower gas tractor and provides
five hours of mowing/sweeping or 12 hours of towing at a
top speed of 5 mph. The 48-volt tractor increases the
overall speed and power by 30 percent and run times by 20
percent to 25 percent.

The Electric Ox models use a single pedal for acceleration
and regenerative braking. Jim Laidlaw, president of
Electric Tractor Corporation, says, “Regenerative braking
allows us to capture and use energy that is otherwise lost
during slowing or braking … and eliminates the need for
traditional mechanical brakes and the maintenance
associated with them.” This feature is integrated with an
automatic braking system that sets a parking brake when the
vehicle is motionless, the foot is off the pedal or faults
occur in the control system.

Optional 900-watt or 1,500-watt inverters enable the
Electric Ox to act as a silent, standalone power source for
120-volt power tools, pumps, lighting and motors at remote
sites.

The 36-volt Electric Ox ($7,350, U.S. dollars) and the
48-volt unit ($8,250) include horn, gauge, hour meter,
lights, onboard charger and suspension seat. Inverters are
$795 (900 watts) and $995 (1,500 watts). Attachments
include a 44-inch mower deck ($1,495), sweeper blade/brush
($1,150) and 48inch dozer blade ($475).

For more information, visit the website Electric Tractor, or write Electric Tractor Corporation, Baden, Ontario.


The Heckeroth Handmade Solar Tractor

Steve Heckeroth has been building and testing solar tractor
prototypes since 1992. His latest design, shown at left and
below, includes the specifications in the box below and
features a multiposition seat that allows the tractor to
perform a multitude of operations, which otherwise only
could be accomplished with several conventional machines.
All the controls are mounted on the arm rests, connected
only by small flexible wires to radio control transmitters.

Multiple Seat Tractor Positions

Forward high position: The same as
on conventional tractors but allows unobstructed visibility
for operations like precision cultivation.

Reverse seat position: Here the solar electric tractor can replace
several other conventional machines. Loaders and forklifts
are designed to put weight on the traction wheels and take
weight off the steering wheels for optimum performance.
High-end commercial mowers are configured to put the
implement out front for visibility and maneuverability. The
operation of other implements, like post-hole diggers and
backhoes, can also benefit from the reverse seat operation.

Planting and harvesting:
The seat can be mounted on the mid or rear three
point-hitch and raised or lowered for planting and
harvesting operations.

Hundreds of pounds of seedlings or
harvested crop can be stored on accessible trays, and the
other available three-point-hitch can be used at the same
time to carry a water tank, cultivator or bed-preparation
implement.

Off tractor position:
The relative ease of operating an electric vehicle by
remote or computer control allows the seat to be removed
from the tractor. This makes the electric tractor suited
for repetitive agricultural operations, bomb disposal, mine
sweep, toxic cleanup and some road maintenance
applications.

To learn more about the potential of this brilliant
tractor design, go to www.renewables.com.
Somebody should buy the rights from Steve
and put this baby into production.
If you are seriously interested in this possibility,
you can contact Steve at tractor @ renewables.com.
Please note that Steve cannot respond to individual
requests
for instructions on how to build
this tractor. He is now dedicating all his
time and energy to the development of photovoltaic
roofing products. — MOTHER


Electric Tractor Specifications

  • Two 10-horsepower, variable speed wheel motors for 60 horsepower of traction
  • Separate 500 to 1,000 rpm power takeoff (PTO) motor will run all standard PTO and three-point hitch implements
  • Onboard five kilowatt-hour battery pack for all day light-duty applications, such as planting and harvesting.
  • Standard Category 1 front and rear three-point hitches, Each use two linear actuators (1,500-pound capacity)
  • Adjustable seat with controls on arm rests
  • Total weight under 2,000 pounds
  • 11 by 24-inch traction wheels
  • 5 1/2 by 16-inch steering wheels
  • Overall dimensions: 110-inch to 12-inch adjustable length, 87-inch height, 48-inch to 72-inch adjustable width
  • Zero turning radius steering
  • 20-inch ground clearance

The Sun Horse: A Solar Powered Garden Tractor

This nifty Sun Horse is a solar-charged,
walk-behind electric tractor that can plow, seed, cultivate
and haul. It provides plenty of power for a large garden
without noise, emissions, slow starting and high
maintenance. The basic unit sells for $2,250 and various
attachments are available.