A number of manufacturers now make stoves
which will burn shelled corn. Although similar to wood stoves,
these new corn burning stoves have been specifically designed
to burn a dry granular fuel, such as shelled corn. Corn burning
stoves & burners have a combustion air fan and a fuel stoker,
both of which are not common in standard wood stove construction.
Why burn corn?
In Ontario we have an abundant
source of dry shelled corn. The corn used as a fuel in corn
stoves does not have to be Grade No. 1, but can be of lower
quality. There are however two requirements of this corn fuel:
- The shelled corn must be dry, preferably
15% moisture content or less. Corn which is higher in moisture
will have a lower heat value per unit weight than "dry"
corn. Moist corn may also cause flow problems through the
fuel loading auger.
- The shelled corn must be free of
fines. Dirty corn which has a lot of fines and cob pieces
will cause problems with the fuel loading auger.
The storage, moving and handling of grain corn
has evolved to a point where there are very few unknowns. Every
year farmers harvest, dry, convey, and store millions of bushels
of corn. The equipment to do all these things is readily available.
Consequently putting a corn storage system together for a home
heating set up is possible with augers, conveyors and storage
bins which are readily available.
Two reasons it is so attractive as a heat source
are that dry shelled corn is so easily handled and in plentiful
supply. Shelled corn also has a high heat energy per unit weight.
Here's how shelled corn measures up to other solid fuels.
Table 1. Heat Energy
of On-Farm Fuel Sources
Shelled Corn
|
7000 BTU/lb
(16,200 kJ/kg) at 15% Moisture Content |
Straw |
6550 BTU/lb (15,200 kJ/kg) Air Dried
|
Corn St over |
7540 BTU/lb (17,500 kJ/kg) Air Dried
|
Wood |
8000 BTU/lb (18,500 kJ/kg) Air Dried
|
You can see from this table that shelled
corn has heat energy close to that of wood.
Basics of Corn Stoves
& Burners Corn burning
stoves are specifically designed to burn a granular fuel. Because
this fuel is metered into the burning chamber, most stoves have
a storage hopper to contain a supply of fuel. In some ways corn
burning stoves are very similar to pellet burning stoves. In
both cases, corn and pellets are very dense. Consequently, neither
of these fuels will burn readily in an open pile in a fire chamber.To
get these fuels to burn, some manufacturers use a small combustion
chamber into which the corn is fed and combustion air is pumped
through. The corn can be either dribbled into this combustion
chamber from above, or it can be stoked into the chamber from
below by means of an auger. The feed rate of this auger can
be adjusted to regulate the amount of corn burned, which in
turn controls the amount of heat produced. The second requirement
for burning to occur is oxygen. In order to support combustion,
oxygen is blown into the combustion chamber by means of a small
fan. The combustion air is usually brought in from outside,
not room air. This combustion chamber is actually quite small
and could easily fit into a child's lunch box.As corn burns
it produces a clinker. Because of the small size of the combustion
chamber the clinker should be removed daily. With practice,
the removal of the clinker can be done without having to shut
down and then relight the stove. A specially designed poker
is used to upend the clinker, then tongs are used to remove
it.
Inside the corn stove, a heat exchanger
is used to remove heat from the flue gases and heat the room
air. A fan is used to move the room air through the stove where
it is warmed. This fan may also help in moving the heat further
away from the stove. A different style of corn stove also
exists which does not use augers to feed in the corn or fans
to provide combustion air or move heated air to the room. By
careful design, these stoves will burn corn at the bottom of
a hopper and radiate heat to the surrounding room. Unlike the
previous type where electricity is used to stoke the fire and
move the heat to the room, these stoves are not affected by
electrical power outages.The type of flue pipe required to vent
the exhaust gases from the stove will depend on the design of
the stove or corn burning appliance. These flue pipes can range
from those commonly used in wood stoves to through-the-wall
vent pipes which actually preheat the combustion air by removing
heat from the flue gases. Follow the manufacturer's recommendations
regarding the type of flue pipe required. It is best to keep
the flue pipe as short and straight as possible (keep the number
of elbows to a minimum) to maximize the stove's performance.
Types of Corn
Stoves A number of different
manufactures are presently making corn burning stoves. They
are available in a variety of sizes and styles. Here are some
of the configurations available:
- Stove (some can be modified as a
fireplace insert)
- Space heater
- Hot air furnace
- Hot water boiler
The size of fuel hoppers also varies greatly.
This hopper size can range from holding one day to ten days
supply of fuel.One thing to consider with the freestanding stove
or space heaters is the surface temperature of exposed metal
parts. This is especially important if there are small children
in the house.
Cost of Heating with Corn
Before you can accurately compare
heating with corn to other heating fuels you have to look at
a number of factors. Not only is price of the fuel important,
but also the heating efficiency of the heating system and the
energy content of a unit of each fuel.
Here is a formula which you can use to calculate
your cost per Million BTU's of useable energy. This formula
takes into account all these factors:
- Cost per unit of fuel
- Energy content per unit of fuel
- Seasonal heating efficiency
Cost per Million BTU's of useable energy
=
(Cost Per Unit Of Fuel x
1,000,000) ÷ (Energy Content Per Unit Of Fuel (BTU) x Seasonal
Heating Efficiency)
Where: Cost per unit of fuel is in
Dollars Energy Content Per Unit of Fuel in BTU's Seasonal Heating
Efficiency is in decimal form ie (70% = 0.7)
Example:
Lets look at an example where you are using corn at $2.50 per
bushel in a stove which has a seasonal heating efficiency of
60%. What is the cost per million BTU's of useable energy?
Corn Cost = $2.50 per bushel Energy content per bushel
= 7000 BTU/lb x 56 lb/bu. = 392,000 BTU Seasonal Heating
Efficiency = 60% = .6
Dollars per Million BTU's Useable
Energy =
(Cost per unit of fuel ($) x 1,000,000) ÷ (Energy
Content Per Unit Of Fuel (BTU) x Seasonal Heating Efficiency)
=($2.50 x 1,000,000) ÷ (392,000 x .6)
= $10.63
Therefore to supply one million BTU's
of heat to the house costs $10.63 when this stove operates at
60% efficiency, burning corn at $2.50 per bushel. The average
older home requires approximately 100 million BTU's of useable
energy per year. When you do the calculations for your situation,
keep in mind that the price charged per bushel of corn may vary
from the market price when small quantities are purchased. Check
the prices carefully before doing these calculations.
Table 2.
Heat Content and Heating Efficiency of Various Fuels
Fuel Type |
Energy Content
per Unit |
Seasonal Heating
Efficiency |
Shelled Corn
|
7000 BTU/lb. (16,200 kJ/kg)
|
70% - 85%
|
56 lb./Bushel
|
392,000 BTU/56 Pound Bushel
|
|
48 lb./Bushel
|
336,000 BTU/48 Pound Bushel
|
|
Furnace Oil
|
36,700 BTU/L (38,700 kJ/L)
|
70% - 85%
|
Propane
|
25,300 BTU/L (26,900 kJ/L)
|
70% - 85%
|
Natural Gas
|
35,700 BTU/M3 (37,700 kJ/M3)
|
70% - 85%
|
Electricity-Resistance
|
3413 BTU/KWh (3600 kJ/kwh)
|
100%
|
Air Source Heat Pump
|
C.O.P. = 2.75
|
275%
|
Water Source H.P.
|
C.O.P. = 4.0
|
400%
|
Wood
|
8000 BTU/lb. (18,500 kJ/kg)
|
60%
|
Limitations
of Burning Corn for Heat
Possibly the first and most important limitation
of corn as a fuel is the stove itself. If the stove uses augers
to feed the corn into the combustion chamber and fans to maintain
combustion and move heated air to the room then an electrical
power interruption will shut the stove down. Very simply with
this style of stove, no electrical power means no heat from
your corn stove. Some stoves require a manual reset after a
power interruption, as a safety feature. Second, since most
house layouts do not allow the free movement of air through
the house, a centrally located stove will not heat the whole
house. If this is your case, size the stove to heat the room
where the stove is located. Oversizing the stove will result
in the room housing the stove becoming unbearably hot.
Corn Stove Buying
Criteria When purchasing
a corn stove there are some questions which you should answer:
- (What is the heat output of the
stove? Do you know how much heat you require to maintain
the heated space at the desired temperature? If you are
trying to heat your whole house with a stove or space heater,
does the house layout allow for the convective movement
of heat through the whole house? Most newer houses are not
built to allow convective air movement. What is the size
of the fuel hopper? Will it require filling on a daily,
weekly or biweekly schedule? What is the seasonal heating
efficiency of the corn stove? Does the unit meet UL and
CSA standards? Does the unit have hot exposed surfaces which
could cause burns to skin? What type of exhaust venting
is required? Does it require a chimney with a flue liner
or can a combination flue/fresh air vent pipe be used? Are
you prepared to clean out the clinker daily and clean the
heat exchanger of ash on a weekly basis? Will the stove
handle granular solid fuels other than shelled corn? This
is important in the event that the economics of burning
corn become unattractive or an alternative low cost pelleted
fuel becomes available. Will this corn burning appliance
be a primary heat source or act as a supplementary heat
source? Stoves with small fuel hoppers will not keep a house
warm for long periods of time, unattended.
- How will corn be stored for winter
operation?
|