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Wednesday, November 5, 2014

Reducing propane used for heating my workshop over the years

http://www.arttec.net/Solar/Propane_use/Propane_by_season_CHART.GIF
Click image for larger version
Maine winters can be brutally cold with temperatures remaining below freezing for months and dipping into the subzero temperatures Fahrenheit at times.  I have kept accurate records of my propane deliveries for my workshop so that I can track the efficiency of the solar heating system I designed and built.   The chart above shows propane statistics since the winter of 2001/02.  Clearly I have reduced my propane consumption by about 75%.  Fiscally you can see that my annual heating cost for propane has dropped from around $1000 to around $450 over the years while the cost of propane has generally increased peaking at just over three dollars per gallon in 2010/11.  

The first year I was here I had moved to Maine from California and was setting the thermostat higher because I had not yet adapted to this cold climate.  Since then I have reduced the temperature setting from 70°F in my workshop down to around 60°F, while in my small 160 ft.² office upstairs I keep the thermostat at 70°F during my working hours and set it back to 62°F at night.

My super insulated building is about 1260 square feet and the propane is used to automatically augment the solar heating system.  As the stored heat from the 80 gallon solar storage tank drops below 140F a Bosch Aquastar propane heat on demand unit ramps up it's flame to maintain a 140F feed to the ground floor radiant slab and 2nd floor baseboard radiators.  The design goal for the solar heating system is that it can heat the building exclusively from solar on sunny days while temperatures outside remain above freezing.   When temperatures drop below freezing I use propane and the wood stove to augment the solar.  

In 2006 I installed an efficient wood stove on the ground floor.  I began by burning just small amounts of scrap wood and have increased the amount of fire wood that I burn up to over 1 cord per season.  I light a fire in the wood stove most mornings in the winter to reduce the my use of propane, on colder days I light 2-3 fires.  By burning wood in a clean burning wood stove from trees felled on my property I am just shortening the carbon cycle of the wood that would naturally decay and release carbon eventually.  So this is basically carbon neutral.  


We installed an automatic backup generator that runs on propane in 2008.  Power outages range from under an hour to over a week as a result of Maine winter storms and wind events.  I estimate that the generator uses over 20 gallons/day, so it can impact our seasonal propane usage.  The winter of 2010/11 was particularly cold, and we were also without power for several days (66.5 hours of generator run-time for the season) so this explains the increased propane consumption for that season.  The generator is necessary so that my wife and I can maintain our home-based businesses and power essentials such as our well pump.  (Incidentally I have Web-enabled my power sources so that I can get email/text messages when the generator starts or stops and when utility power fails and returns)

Overall I am pleased that I have dramatically reduced my use of fossil fuel for heating my building.  I also enjoy the sweat equity of cutting and splitting firewood, as they say it warms you twice.  The first time when you cut, split and stack the wood and later when you burn it.