Logging wood stove consumption

Emoncms
1

Hi,
using emoncms to record temperatures, solar production and electricity consumption around the house. With winter just around the corner, I have been thinking about a way to log the amount of wood we are burning in the stove (secondary heating source, but still keeps our electricity bill down).
We have a well-defined wood box in the house (known volume) and can make an estimation on the type of wood we are burning (mainly pine or aspen) to get at least an estimate of the energy.
I have a QR-code by the wood box pointing to a simple webpage with a 0%-100% slider for how much wood we have filled and then a radio group for the type of wood. Feeding the volume and calculated energy into an input is already done and I log the inputs into accumulated feeds.
What I’d like to do is graph this in some way and ideally get kWh/day.

Any ideas?
/Mattias

2

wondering if it might be easier to calculate your kWh production by measuring your flue or the fire box temp depending on the type of stove it is … if it a normal radiating wood stove you probable could calculate it quite accurately taking measurement of the ambient and the surface temp of the stove – the same with the flue ( mind you might have to have barometric flue damper so on windy days the draft stays about the same or other damper ) and then using the efficiency scale of your wood stove - 60 - 90% to calculate the kw produced

P=\sigma \cdot A\cdot T^{4}

\sigma , Stefan–Boltzmann constant 5.670 373 (21)×10−8 W·m

here a webpage to help you if you want

http://mb-soft.com/public3/woodstov.html

3

A warning to anyone contemplating this calculation: Don’t mix your units. The Stefan-Boltzmann constant that Stephen quotes is in SI units, the MB-Soft page uses American (non-SI) units.

4

Have been pondering a getting an IR flame detector and aim it at the stove. At normal temperature and adding fuel according to the instructions, the stove has been officially tested to produce 8 kW of heat. I bought an IR flame sensor and aimed it at stove from a couple of meters distance, but no go - the sensor didn’t see the stove burning (probably the glass door).
Another way would be to use a thermocouple on the chimney to see when the stove is operating.
This would probably solve my problem since I can then estimate the stove’s power and log that to a normal power feed in emoncms. Logging the actual volume of fire wood entering the house would allow me to keep tab on consumption.

Thanks,
/Mattias