Off-Grid Heating

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The battle plan for work change in December 2017 with an inside frontal assault, and I couldn’t wait — the notion of finally sleeping indoors— what a novel idea. I adapted to months of living outdoors, sleeping, and working in freezing temperatures. Now, two priorities were on my mind; heat and power.

Choosing a heating method for your off-grid home is not much different than if you lived in the city, except for one important point. You’re not hooked up to the grid, no grid electricity. The electricity that is generated (stored in batteries) usually comes from solar or wind power or a combination of both, which is limited. However, you do have choices for heat, that is, wood stoves, a fireplace, fireplace inserts, gas, or a combination of wood and gas.

Liquified Petroleum Gas (LPG)

Propane usage is most common in rural areas of the United States. An environmentaly friendly fuel compared to natural gas. Natural gas is around 80 to 90% methane, which is extremely flammable. Also, if released into the atmosphere, methane is 25 times that of CO2 measured over 100 years,[1] not good for the planet. However, both are dangerous if released in confined spaces.

Propane is classified as an alternative fuel under the Energy Policy Act of 1992. Price fluctuations are seasonal but can be subject to supply chain disruptions. Moreover, 2% of the energy used in the United States is propane.

There is a multitude of gas heating products on the market that burn both natural gas or propane. In many cases, natural gas units can be converted to propane with a conversion kit.

I selected propane as a secondary source of heat and wood as the primary source. The decision was based in part on the cost of propane, but primarily on aesthetics. What would a cabin be without a real fire? I installed a Rinnai direct vent furnace. With its programmable interface, it can be set to turn on at different times during the day or night. The unit comes in handy anytime I need to leave for an extended period.

Propane and Wood Comparision

The table shown below provides a scenario of how propane vs. wood differs in terms of price and cost. The scenario assumes the following:

  • Wood is seasoned with a water content of 20% or less
  • The efficiency of the wood-burning stove and propane unit is conservative
  • The wood-burning stove and propane unit are properly installed and vented
  • A reasonable estimate of 50 Btus to heat one square foot of cabin space. Climate zone 4, 45-50 Btus/sq ft, and ~875sq ft.
  • The propane price per gallon hovered around $2.50 at the end of December 2017.
FuelFuel Cost
per Unit
Fuel Price
$mBtu
Efficiency
%
Fuel Cost
$/mBtu
Fuel Cost Heating
Season 44mBtu
Wood Stove*$200/cord$5.9765$9.48$417.12
Wood Stove** $200/cord $7.5865$12.03$529.32
Wood Stove*** $200/cord $13.1665$20.89$919.16
Propane$2.50/gal$24.0970$30.31$1,333.64

*Pinion Pine Heat Value 33.5 mBtus/cord
**Douglas Fir Heat Value 26.4 mBtus/cord
***Ponderosa Pine Heat Value 15.2 mBtus/cord

Wood Stoves

Millions of people worldwide use wood stoves for heating and cooking. Approximately 40 million people in the United States and 200 million in Europe use wood stoves primarily for secondary heating.[2] Today, wood-burning stoves are much more efficient in reducing greenhouse gases and particulates.

Catalytic wood stoves

  • Advantages:
    • Longer burn times resulting in less wood consumption and higher efficiency (average 78%)
    • Lower emissions than secondary combustion stoves
  • Disadvantages:
    • Operational learning curve 
    • More maintenance – cleaning catalytic converter
    • Generally more expensive

Non-catalytic or secondary combustion stoves

  • Advantages:
    • Display more flame – ascetically pleasing
    • Less costly than catalytic stoves
    • Lower maintenance requirements
  • Disadvantages
    • Shorter burn times
    • Less efficient (average 71%)
    • Generally more expensive

Hybrid stoves, which are a combination catalytic and secondary features are also offered.

I purchased a secondary combustion wood stove with a heat shield from a dealer in Trinidad Colorado and scheduled a time for a speeding installation. It is a cast-iron firebox covered in basil enamel. Inside it is lined with soapstone, which extends what they call the “HeatLife.” Other specs include the following:

  • HeatLife up to 10 hours
  • Heats up to 1,800 sq ft
  • Produces up to 50,000 BTUs
  • Particulate emissions 2.1 grams/hr or .07407532 ounces/hr

An advantage of using soapstone is the consistency with which it heats up. Add a log before going to bed, and in the morning, the stove will still be generating heat. The soapstone absorbs the heat and radiates it on the backside of the stone. Heating is gradual and consistent; it doesn’t blast you out of the room. I set my cot up directly in front of the stove and enjoyed cozy and warm nights.

Honestly, after installation, I didn’t want to use it. Like a beautiful piece of furniture you polish once in a while but otherwise, just look at it. But soon it was covered in construction dust and after the first fire, I didn’t feel so bad.

The EPA’s website, BurnWise, provides a wealth of information about stoves and other energy-related topics.

Messy but Warm

A neighbor suggested I purchase a stove heat powered fan. Using heat from the stove these fans are a fantastic way to distribute warm air throughout a room without electricity.

References

  1. Chandler, D. L. (2017, January 30). Carbon dioxide isn’t the only one that matters, and the gases vary widely in potency and duration. MIT News. Retrieved from http://news.mit.edu/2017/explained-greenhouse-gases-0130
  2. Carvalhoa, R. L. Jensena, O. M., & Tarelhob, L. A. C. (2016). Mapping the performance of wood-burning stoves by installations worldwide. Energy and Buildings, 127, 658-679

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