…As the hype around biofuel already begins to dissipate, serious researchers and planners are advocating curtailment of long distance transport and the adoption of electric vehicles as one of the most sustainable options to replace the work and carbon footprint of the internal combustion engines.
…Post Carbon Institute’s Energy Farm Program is addressing the tension between food vs. fuel, or land vs. energy. In our search for ways to reduce these tensions comes the latest Energy Farm Demonstration Project: The Electric Tractor.
We have made connections with activist and inventor Stephen Heckeroth and are seeking to test cutting edge agricultural equipment for a post-petroleum world. The electric tractor does not compete for food and prime agricultural land for fuel, has a significantly reduced carbon footprint, increases the scale of acreage that can be cultivated, and is easy to operate for the 50 Million New Farmers that Richard Heinberg is calling for in the coming century. Stephen is not the only person who has made the electric tractors. John Howe has been working on retrofits of agricultural equipment powered by electricity.
This week we took a (petroleum-powered) scenic drive through the redwoods to the Mendocino coast to visit Stephen Heckeroth and demo his “Solar Electric Tractor.”
…Let’s run through some numbers to help us evaluate the land requirements of electric tractors versus tractors operating with biofuel. Electric motors are about 90% efficient at converting energy to work, and solar panels are the most efficient way of converting radiant sunlight energy into electricity (approaching 20% vs 1% or much less for plants). Stephen’s tractor can hold 5 kWh of battery packs that will give the same kind of performance in terms of work over a year as the 1700 gallons of diesel fuel in a small tractor. 5 kWh of batteries can be recharged each day with a 1 kW photovoltaic system covering about 40 sq ft (3.7 sq meters) of roof space. By contrast, 43,000 sq ft (4,000 sq m) are in an acre (which is 0.4 hectares).
In terms of fuel dollars, 1700 gallons of diesel cost about $5,100 in 2007. Installing a 1 kW photovoltaic system might cost about $10,000. By investing once in double the annual cost of fuel, a farmer could power a tractor for decades.
Not only does this appear to be an economically wise investment, but electric tractors are a pleasure to use. As you would expect from an electric motor there is no diesel exhaust emissions and no loud engine noise. While driving the tractor we could actually hear birds chirping (a rare experience when operating heavy machinery). With an electric tractor there is no longer a need for engine oil or oil filters, a radiator and coolant, no need for fuel filters, no engine overhauls, and it offers a lower operating cost ($0.50) to charge the 5KW battery pack.
…We plan to put the tractor through its paces and provide data that farmers will find useful as they begin to evaluate the efficacy of this exciting technology. Although in theory we should have great performance from an electric tractor, a lot of questions exist related to how long the tractor can work (similar to the range of an electric car) and whether or not the machine has enough power for the rigorous demands of cultivation. …
