I
enjoy scientific and engineering projects, I have practical homestead
and equipment skills to experiment, and I enjoy sharing what I
learn. With a bit of financil discipline allowing capital
investments that save money over time, I started using shelled court as
a heating fuel.
Specifically, I heated my home office building and Amateur Radio operating building with an alternate fuel source during the Winter of 2001, and this grew into a project to record fuel usage data on how I was actually using BTUs, and compare different fuel sources. This page is a quick reading page of the results with actual numerical comparison. Please credit this web page as the source for any information you relay to others, or link directly to it if you're building a web page.
From the end of September 2000 to mid-April 2001, I heated my 640 ft2 of office space for about 12 hours on each of 55 days (26% of the days). I used 2400 lb wood, which occupied approximately 170 cubic feet (about 1.3 cord). The Oregon Department of Agriculture publishes BTU content of wood per ton. Utah State publishes BTU content and weight of wood per cord. Estimating on the low side, I am guessing I get about 7000 BTU per pound of wood similar to type and condition of what I burn. The "seasoned" wood tables show about 2500 lb weight per cord. I'm showing about 1800 lb per cord, which checks because mine wasn't all hardwood, and within the precision I measured weight and volume of the wood used. Web summaries can help you choose what type of wood to burn.So, I'm burning about 305,000 BTU of wood per heating day,
with about
60% efficiency in my stove, delivering about 183,000 BTU.
Assuming
electricity is 100% efficient, this corresponds to 54 KWH per day (3413
BTU/hr per KW). Using my local winter post-tax rate of 7.8 cents per
KWH,
that's about $4.19 per day I'm not spending on heating my office. Total
savings this winter of $230 compared to electricity - more if
I had
heated more days or longer hours.
My numbers say my wood office stove gives 14,000 BTU/hr. In order to give this numer some meaning, it can be compared to other common heat sources. My small propane heater gives 8,000-14,000 BTU/hr, and my portable electric heaters are 1000-1500 Watt (or 3400-5000 BTU/hr). Corn burners are available in the 30,000 to 200,000 BTU/hr range. My propane barbecue grill is about 40,000BTU/hr.
Websites about corn burning stoves, furnaces, and boilers list corn at
500,000BTU/bushel and propane at 100,000/gallon (a chemistry book and
my
calculator give 90,000/gal, which I'll use for calculations).
I'm
buying bulk propane at $1.25/gal after tax, or using 20 lb bottles
(4.78
gal) for localized heating or barbeques at $11.60 per fill.
[As an
interesting side, this says a 20 lb bottle of propane has about 431,000
BTUs in it. It would last about 11 hours with my 40,000
BTU/hr barbecue
going full speed. Seems about right...]
Comparison Summary of my options:
Corn @ $2.05/bushel, 80% efficient, gives 200,000 BTU per dollar.I've seen others use a wag of 100 million BTU per year to heat an average older farm house. Tracking my home propane use rate through the calendar year of 2000 came up with 107 million BTU. I'm a pretty agressive about turning down the thermostat, so actual usage for others may be higher, but the wag is not far off. To compare annual costs, the cost for 100 million BTU are shown below. If you use more, savings will be more. Although not currently an option for me, I included natural gas data from the Department of Energy in the table below for others to use as a comparison:
Electricity @ $0.08/kWh, 100% efficient, gives 42,700 BTU per dollar.
Propane (bulk) @1.25/gal, 92% efficient, gives 66,600 BTU per dollar.
Propane @$11.60/20lb, 92% efficient, gives 34,100 BTU per dollar.
Wood @$125/cord (local costs), 60% efficient, gives 60,480 BTU per dollar.
|
|
|
| Shelled, dry corn @ $2.05/bushel |
|
| Natural Gas @ $0.93/therm |
|
| Propane, bulk @ $1.25/gal |
|
| Wood, @ $125/cord |
|
| Electricity, @ $0.08/KWH |
|
| Propane, 20lb tanks @$11.60/ea |
|
| Geothermal* |
|
Observations:
Propane has to go up to $1.41/gal before wood is cheaper.*Geothermal is also worthy of comparison (vermontgeo.com, cloverland.com), but it is hard to compare because the the investment profile is very different - you would have to invest a large up front capital and then annually expend only the energy necessary to pump the coolant through the system. I have no direct numbers, but others have compared the cost to lines in my chart above, allowing me to indirectly generate a number for the chart above. I think in the long-run it would be cheaper than even shelled corn. If you can drill wells yourself, a standing column well (SCW) geothermal system may the best for you.
Propane has to go up to $2.00/gal before elec is cheaper.
Propane has to go down to $0.44/gal to beat corn.
Using a local electric heater is cheaper than a local propane heater.
Initial cost outlay for a stove is also something to
consider. A used
full-house
wood furnace may costs as little as $500, while a new corn furnace is
about
$2100. I already have a propane furnace, but expected high
prices
are making me decide between wood and corn. If a year uses
107 million
BTU, there's a $1016 difference in operating costs per year.
It would
take 2 years to recover the cost increase of the corn
furnace. Wood
is mostly free for me, except the 5 hours labor and $10 in tools per
cord,
plus safety concerns. For my kids, handling the corn is much
easier.
Mitigating this somewhat (making the payback period longer) is the consideration that I could have have used the $2100 as additional mortgage payment, saving me 7.5% a year. That's about $330 over 2 years, so add another 4 months on the payback period.
A corn burning stove has an auger motor, a combustion motor, and a convection motor. For the unit I'm looking at, it's a steady 285 Watts while running full bore. My propane house furnace uses about 440 Watts, but according to recorded Home Heating Data Graphs, it only comes on for 16% of the time during a 38 degree day, or an average of 70 Watts.
The corn burner heat output is adjusted by slowing down the blower and auger, as compared to the furnaces digital on/off behavior. Absolute worst case would be if you kept the corn burner on full bore 24 hours per day. In this case, over the course of a 30-day month, the corn burner would use 155 KWH more, or $12 in my case.
Sounds bad, eh? Actually, if you add up the electricity and fuel costs for each hour of operation, you get $1.12 for propane, and $0.22 for corn. The propane furnace kicks out 74,000 BTU and the corn stove kicks out 40,000 BTU. Making this correction to fairly compare them, leaves propane costing me $0.60/hr and corn costing me $0.22/hr. This shows corn is 36% of the cost instead of 30% from the table above. And remember, temperatures colder than 38 degrees make the numbers shift to favor the corn (furnace duty cycle increases and uses more electricity per hour).
Even if you intend to move sooner, consider that many corn burning stoves are zero-clearance UL Approved devices. In other words, you can stand them on your carpet floor, right next to the wall, with bookshelves on both sides. The only modification to your house is a single 5 or 6" hole through an outside wall ..not much more than a dryer vent. Think of this as a wash machine. Even if you sell your house, you can take it with you.
