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Re: (ET) [Fwd: [EVDL] The Case for the Electric Tractor] (fwd)

An interesting response below (from Michael). I am a happy ET owner ( 2 tractors) and use a 40 HP John Deere utility tractor to do a lot of work as well. A couple of observations:
The hours run by my diesel utility tractor tend to be "sporadic" and "grouped." In other words, I may not use it for a week or two, then change implements and use it for two or three 8 hour days in a row. This is common in agriculture where there are "triggers" for activities: Its time to plant, the weeds are thick, the corn is too tall to mechanically weed, its time to till, etc. Many tractors are left idle for relatively long periods and then worked intensely for short periods. Some tractors are dedicated to one task (mucking the barn for example), and some are "spares" used to occasionally haul a hay wagon or do light chores like mowing ditches.
This would suggest that any charging system should be capable of very fast charging. Maybe a combination of grid plus solar - if there is time, use solar. If you need the tractor tomorrow morning, use grid. The mix depends on tractor use and economics, but there is no one-size-fits-all solution.
While tractors are heavy, there is a limit to weight. Soil compaction is always a concern. My John Deere diesel weighs in at 3700 pounds without ballast in the tires. Think anyone can engineer an electric tractor that can work all day producing 35 hp at the PTO weighing in at less that 4000 pounds including the battery pack? I can carry a day's worth of energy in two hands - can you do that with a battery pack? Of course its a tiny tractor compared to some large 4wd plow pullers and combines, but I would assume the size of the battery pack necessary to move bigger equipment would be proportionally larger and heavier too. In one respect liquid fuels like diesel are very efficient - they can be carried in a light container and replenished easily in the field as necessary. 10 gallons of diesel doesn't weigh a lot but contains a lot of energy, it's easily transported, and it powers the tractor for a day. Too bad we can't design a cheap battery pack that consumes itself to produce energy leaving nothing behind.
We in the NE and other parts of the US have something that comes around every year called "winter." It has a big impact on solar energy production and battery efficiency, especially when tractors are stored in very cold places. My diesel utility tractor is used as much in the winter as summer to move snow. How does that figure into the calculations of efficiency? I know my ET with a bucket loader (very inefficient electric-hydraulic setup) won't do much work before it is tired in the cold.
Finally, it is great from an engineering perspective to talk about efficiencies. However, that won't sell tractors or cars. What will sell is cents per mile or cents per HP/hour of work as well as the need for additional investment in infrastructure and/or implements to support a conversion to a different way of doing the same job. For example, this would suggest that an electric tractor should NOT use electric implements, but rather PTO driven ones. This might fly in the face of efficiency, but we all have tons of stuff that attaches to a 3 point hitch and is driven by a PTO, and having to change that would be a big investment. Infrastructure engineering (a solar/grid charging solution) will be expensive regardless of efficiency.
Finally, the discussion can always be couched in terms of economic costs and benefits. Regardless of how efficient or inefficient a solar panel might be or how efficient an electric motor might be, a solution will not sell if it can't pay its way. A more efficient solar panel is likely to also be a more expensive one, so efficiency cannot be considered in a vacuum. Maybe the relevant question would be something like " How quickly can an alternate way of doing the same job to produce the same results pay for itself, including all additional investments in infrastructure?" For each application there will be a different "breakpoint" where the costs of the alternate solution are the same as the costs of the current solution.
Frankly, I'm not wildly optimistic about the future of the electric tractor. While electric motors have power characteristics that are useful in tractor applications, and while control systems have come a long way from our old GE relays and discrete transistors, there are a number of problems from weight to the required flexibility to meet widely differing demands for use that may well keep electric tractors on the sidelines. 


At 09:26 AM 8/27/2007, you wrote:


Forwarding my response to the case for the electric tractor....

--

--------------------------------------------------------------
Michael S. Briggs
UNH Physics Department
(603) 862-2828
---------------------------------------------------------------

---------- Forwarded message ----------
Date: Mon, 27 Aug 2007 09:23:47 -0400 (EDT)
From: Michael S Briggs <msbriggs alberti unh edu>
To: ae listproc sjsu edu
Subject: Re: [Fwd: [EVDL] The Case for the Electric Tractor]
Overall I agree with much of that, but I strongly disagree with the claim that a tractor with a 5 kwh battery pack will be able to do the equivalent work as a 
diesel tractor. They are making the significant mistake of just picking 
some
number of hours of operation for the tractor over the course of a year (the
nice round 1,000 hours they assume a tractor is used), and assuming it is used the same amount every day. But, that is not the case at all. During particular 
times of the year, the tractor may be used 8-12 hours a day. With diesel 
fuel
containing roughly 36 kwh/gallon, and let's assume the engine is 30% efficient 
(fairly low for a diesel), that works out to it using 11.1 kwh of energy 
for
each hour of operation. So, even one hour of operation uses twice the 
battery
capacity of the tractor.
Add to that that if the tractor has a 5kwh battery pack, you won't get 
5 kwh of work out of it. Yes, motors are efficient, and some batteries are 
-
but the most common and cheap batteries (lead acid) drop in efficiency
significantly as you try to pull more power out of them - and tilling a 
field
would require significant power, resulting in a substantial drop in efficiency 
(so you may only get 3 or 4 kwh of work out of that 5 kwh battery pack,
depending on how much current you try pulling out of it).
        And if a tractor needs to be used 8 hours a day, that would require
almost 90 kwh of energy - and we are to believe that a tractor with a 5 kwh
battery pack is going to be able to do that?
Bare in mind that I am a fan of electric vehicles, and have an electric lawn tractor myself - which I use for mowing our lawn, not tilling hundreds of 
acres of fields.

Mike

--

--------------------------------------------------------------
Michael S. Briggs
UNH Physics Department
(603) 862-2828
---------------------------------------------------------------

On Fri, 24 Aug 2007, JS wrote:

>
>
>  Here is an interesting article from Global Public Media.
>
>  ----------------------------------------------
>  The Case for the Electric Tractor
>
>  30 Jun 2007
>  The Case for the Electric Tractor
>  Christoffer Hansen and Jason Bradford
>  Post Carbon Institute - Energy Farms Program
>
>  The discourse has been heating up around biofuel for well over a year
>  now. The classic food versus fuel debate has been engaged recently by
>  the United Nations, while scientists, climate change experts, and
>  farmers begin to question the scale and logistics of biofuel
>  replacement of the current liquid fuel demand.
>
>  This June, one of us (Dr. Jason Bradford) interviewed Lawrence
>  Berkeley National Laboratory staff scientist and Post Carbon Fellow
>  David Fridley on the bi-weekly radio show the Reality Report. The
>  topic for the interview: "The Myths of Biofuels" finds Bradford and
>  Fridley engaged in a devastating analysis of the scale and logistics
>  of replacing our current fossil fuel demand with ethanol and
>  biodiesel. In short, a large scale industrial biofuel system will
>  wreak havoc on the soil, require an entirely new distribution
>  infrastructure (due to the corrosive nature of ethanol), not easily
>  adapt to the current fleet of USA autos, will compete heavily with
>  food production and natural ecosystems that are seen as potential
>  cellulosic biofuel feedstocks, and will do little to actually replace
>  the current (or future) energy demands of liquid fuel.
>
>  Two weeks later, the Reality Report picked up where the Fridley show
>  left off and we both joined Yokayo Biofuels President, Kumar Plocher
>  on the show. The question was: If biofuel is not going to be
>  sustainable on a large industrial scale, then would a local biofuel
>  system be an appropriate response to the limitations of long-distance
>  transport and petrol dependent methods of cultivation and processing
>  of biofuel? If biofuel is produced for local consumption how much land
>  would be needed, what crops would be used, and how would they be
>  processed? Again, simple math painted a picture of an inflated hope
>  and hype. We ran the numbers and with the 35,000 acres (14,000
>  hectares) of remaining prime farm land in Mendocino County
>  approximately 84,900 acres (34,000 ha) would be needed to replace
>  current county diesel consumption if canola was used as the prime
>  feedstock.
>
>  Additionally, approximately 231,100 acres (94,000 ha) of farm land
>  would be needed to replace the current gasoline consumption with
>  corn-based ethanol. It doesn't really matter much which crops, or
>  combination of crops, are considered--the land base isn't available to
>  support a biofuel industry even on a local scale that meets current
>  fuel demand. These analyses also absurdly assume the use of all
>  agricultural land for fuel production, leaving no room for food! This
>  is unconscionable and not the direction that any serious farmer or
>  environmentaly aware person desires to advocate.
>
>  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. Vegetable oils and ethanol are useful
>  products and should not be omitted from agricultural production, but
>  their uses require further consideration. Why do we have to burn these
>  useful feedstocks when they have multiple alternate uses? Should
>  biodiesel production be limited to the reuse of waste food oil?
>
>  In an article published by AlterNet, David Morris from the Institute
>  of Local Self Reliance makes two important observations related to the
>  uses of vegetable oils and plant-based sugars that are consistent with
>  the position of the Local Energy Farm Program. Morris suggests that
>
>  "human nutrition is the highest use of plants, followed by medicinal
>  uses and possibly clothing [and?] we should first use biomass to
>  substitute for industrial products that use fossil fuels rather than
>  for the fuels themselves. [W]hile there is insufficient biomass to
>  displace a majority of fuels; there is a sufficient quantity to
>  displace up to 100 percent of our petroleum and natural gas-derived
>  chemicals and products. And these are much higher value products."
>
>  Additionally, he recognizes that: Electricity, not biofuel, will be
>  the primary energy source [note: we consider electricity an energy
>  carrier, with wind, solar radiation, etc. being renewable sources] for
>  an oil-free and sustainable transportation system. But biofuel can
>  play an important role in this future as energy sources for backup
>  engines that can significantly reduce battery costs and extend driving
>  range.
>
>  While biofuel might remain a short-term transition technology, it is
>  being recklessly advocated by the United States Senate as a panacea
>  for the liquid fuel appetite. One response is to advocate appropriate
>  uses of biofuel, including its role in agriculture. Another is to
>  adapt to new information and seek alternate ways of powering crucial
>  societal infrastructure. One such component is a relocalized
>  agricultural system.
>
>  We should remember that biofuel was originally produced by farmers for
>  on-farm use. Just because you can power an internal combustion engine
>  on bio-blends does not necessarily mean that it is a suitable energy
>  replacement or clear cut solution to salvage the industrial model
>  which is so deeply dependent on cheap liquid petroleum.
>
>  Before agriculture began to juggle the burdens of constant soil
>  degradation, increased mechanization, and cheap labor (see Steinbeck's
>  'Grapes of Wrath'), animals were used for the cultivation of crops.
>  However, like a biodiesel tractor, some land must be dedicated to
>  feeding a team of horses. On good pasture land it is estimated that 5
>  acres (2 ha) of land is needed per horse. Marginal land could require
>  about 13 acres (5 ha) per horse, and possibly much more.
>
>  Similarly, to produce 1000 gallons (3,800 liters) of biodiesel
>  requires the cultivation of 10.25 acres (4 ha) of canola. This is
>  assuming you have access to processing equipment and methanol (which
>  is normally derived from natural gas). Whether you consider horses,
>  oxen or biofuel to reduce dependence of fossil fuels, cropland is used
>  that will often compete with land needed to grow food.
>
>  For example, data from the Nebraska Tractor Test Laboratory shows that
>  the performance of small, modern tractors at around 20 hp requires
>  about 1.7 gallon (6.4 liters) of diesel fuel per hour of work. If we
>  estimate that a tractor will be in use about 1000 hours per year, this
>  would require 1700 gallons (6,400 l) of fuel. In biodiesel terms, it
>  would take 17 acres (6.9 ha) of prime crop land to grow the fuel for
>  one small tractor per year. Of course we should also think about how
>  much land such a tractor could cover in a year. A small tractor could
>  cultivate about 25 acres (10 ha) in those 1000 hours, meaning that
>  after fuel crop use only 8 acres (3.2 ha) would remain for non-fuel
>  crops.
>
>  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." Stephen has been working on alternatives
>  to fossil fuel use in both his private and professional life since
>  1970. His company, Homestead Enterprises, has been doing electric
>  tractor conversions since 1993, and has become an internationally
>  recognized consultant on industrial and agricultural electric
>  equipment. In 1996-97, Ford-New Holland commissioned Homestead
>  Enterprises to build an electric tractor prototype. In 1997-98, a
>  Japanese company, Eifrig Ltd. Commissioned another prototype. A fully
>  functional design was completed in July 1998 and several provisional
>  patent applications were filed in August 1998.
>
>  As Stephen points out: Our future is only as sustainable as the tools
>  we use to get there. The daily energy income from the sun is gigantic
>  and it is feasible to use already existing renewable energy
>  infrastructure to "re-fuel" the Electric Tractor. If the farm has yet
>  to invest in renewable energy infrastructure, it is also possible to
>  charge the batteries with standard 110V power (or 240 volts in other
>  parts of the world).
>
>  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 5kWh
>  battery pack. There is a 1500W charger/inverter on the tractor and a
>  complementary AC power outlet. This is a useful feature because it
>  allows the use of electrical equipment in the field (e.g. sorghum
>  press, or thresher and winnower). The ability to process certain crops
>  in the field (like sorghum) is a good way to circumnavigate the need
>  to transport large amounts of material to a central processing
>  facility.
>
>  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. To test the machine we will attempt to run a
>  dryland grain demonstration in Willits, CA. We intend to plant a fall
>  crop of wheat or oats using a disk, harrow, and seeder. These classic
>  implements used to be horse-drawn and do not require the intense
>  energy that PTO (Power-Take-Off) implements require (less draw-down on
>  the battery bank). The over-winter rains will help to get the crop
>  established without relying on intensive irrigation and we plan to
>  come back in the next summer to harvest and process the cereal crop.
>  The experiment is two-fold in which we get a chance to demonstrate and
>  produce grains with minimal amounts of fossil fuel and high energy
>  inputs while also collecting data related to operation time and power
>  capacity of the prototype electric tractor.
>
>  Aside from John Howe and Stephen Heckeroth, we have not heard of other
>  people using electric tractors for other than mowing; we hope that
>  many are out there. We would like to hear from you. We invite readers
>  to check our numbers and the assumptions above and please tell us how
>  realistic we are, based on your data, calculations and experience.
>
>  If you want to see Stephen's tractor in operation, check out this link.
>
>  For more information about the Willits/Brookside Energy Farm and about
>  the electric demonstration, please contact Dr. Jason Bradford or
>  Christoffer Hansen.
>
>  For more information about the Energy Farms Program, please contact
>  Julian Darley, President Post Carbon Institute (email or call 1 800
>  590 7745)
>
>
>
>


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