Running my wood stove fan off panels/batteries

C_Heath

Hey guys

I am a 100% wood furnace user. Last month we had a nasty ice storm and I crippled us for 12 hours. Luckily I have a generator and we didn’t freeze because I kept the fan running on the stove but during all this I got to thinking what if I didn’t have the generator??

So I did some calculations and mind you I suck as calculations but my stove fan operates at 228 Watts. It’s one speed and in the winter will run 24/7 as long as I am burning wood.

By my sometimes inaccurate calculations this ends up be 5.47kwh per day?

I will be running 4 rooftop panels at 1200 Watts into an inverter for the ac stove fan. Now, this is where I run out of talent. How many batteries and what size to power the fan for let’s say 2 to 3 days without a charge in case of clouds or no sun.

Thanks to who takes the time out for this.

C in N.C.

mcgivor

Your calculation is correct, which makes the fan extremely expensive to run with battery backed solar, without doing a calculation, using my daily consumption of~4.5 kW you'll need approximately 16×225Ah golf cart batteries for 2-3 days autonomany. The PV would need to be sized sufficiently to recharge the batteries, being that it is a standby application 1200W would suffice, It would need 12 hours +  of charging to replenish the batteries depending on depth-of-discharge. By contrast a Yamaha EF 1000 IS generator will run the fan for ~ 24 hours on a gallon of gas, cost way less than the batteries alone, probably outlast the batteries, which  have a limited life expectancy 5-7 years, give or take, wether used or not. Not trying to discourage you in any way, but solar energy is not cheap, the only way to offset some of the costs is with a grid tied hybrid system assuming tiered rate structure where load shaving can at least recoup some of the investment in batteries, as well as using excess production, or sell if possible because in float most would go wasted. Batteries sitting  in float, waiting for an outage, would be money wasted. My opinion others may differ.

jonr

Would be cheaper to buy an old fashioned wood stove that doesn't need power.    Maybe consider converting a generator to propane (easier to store for long periods).

Dave Angelini

I stopped using the fan on my wood stove 25 years ago....
How big is the home or cabin?

C_Heath

Dave Angelini said:

I stopped using the fan on my wood stove 25 years ago....
How big is the home or cabin?

My home is 2000 square feet and my stove is brand new and its piped into the ductwork. So its a furnace so to speak. Its the best heat ever so even if I have to just suck it up and use power then so be it. I just wanted to see. After some other calculations, I will probably need around 10 batteries to get the job done. That's a little too many for the application for it to be worth it to me.

Dave Angelini

Mine is the "best heat ever" also. 

westbranch

Is the fan a critical element in the survival of the stove, ie it will be damaged if there is no fan?  our old wood furnace could be used with a smaller fire and removing the end panels on the fan enclosure, and let good old convection distribute the heat, not quite as efficient but  we did not freeze either....BTW this is where the term "Central Heating" is really important, it really does have to be in the CENTER of the house...
.
ADD:  Oh yes there are also the ECO-Fans that use a piezo generator to power the fan once the stovetop is >150*C. 
That is all we use for 2 x 1100 sq. ft . floors

Dave Angelini

Good question Eric!  Since we always design for winter offgrid to minimize electricity there is a flaw with this choice.
The OP should try (if safe to do so) running without the fan. Most offgrid homes even larger than this do not need a fan to heat from a wood stove.
The fan just makes it faster or moves air into rooms with closed doors. Open the doors and test it without the fan!  Good Luck!
The fan here is more than the load of a  good 25 cubic foot refrigerator. Only large systems can absorb these kinds of loads and the reefer is cycling.

wellbuilt

I've been running my house on a little champion genarator since Augest .
 We are there working 3 days a week .
 I get 3 days on a 2 gallon gas can its 50hrs in 3 days 5 bucks . 
 It burns about 11 hrs plus on a gallon of fuel . 
 I think just run a small Jenny if the power goes out

mike95490

Because of this, we designed and built our 2300sf 2 story house with passive heat, from a Masonry Heater

Cold days (mid 30's and below) we burn 40lb of wood. It'd really be less, but Kalifornia has a rule that a damper can now be only 70% closed.  30% of a 8" flue lets a lot of heat out.

pics & info  https://www.facebook.com/media/set/?set=a.383468711726588.86888.120212794718849&type=1&l=c762d10b5f

http://www.mha-net.org/

There are some heaters that can be added to an existing house, most are built as the house is built around it

Dave Angelini

There is masonary heater here Mike that is in a Log home from the 1880's. The place is 3,500 + and the old guy who lives there keeps it really nice. He is up at 4,200 feet and he amazes me for his age. His family has owned the place since way back. He has a full progression of Diesel gensets from when they were first sold. All the old Perkins are in his garage. I was the one who convinced him to get batteries and an XW and he is so happy now having fuel deliveries only once a year.

The really amazing part is that the logs in his home are still quite beautiful. I doubt we can get the preservative in Kalifornia

just starting

I have a magic heat reclaimer uses 36 watts, I put it on this year, I have to clean my stove pipe 3 times a year now, about 1/2" build up with 24/7 burn, home stays nice and warm now