I'm not really sure what quantity you intend by 250 watts per hour per square meter. Is that just an extraneous per hour? My insolation numbers come from ASHRAE; the article you cite seems consistent.
I believe that biomass is best reserved for high-temperature applications. In my one-earth scenario, that's sufficient reason not to use it to reach a mere 50C. However, perfect may be the enemy of good. The best solutions I see for space heat aren't easy retrofits, and most US biomass residue probably isn't doing anything useful. In the near term, fuel substitution looks like a good idea.
Unfortunately, I don't believe it makes sense to commit pikans for the next 20 years to collecting and splitting wood, between classes. I suppose a dual fuel system is feasable.
How do you get the 1.2M BTU figure? It seems to me that 700 gallons at 100 C only carries 850K BTU above room temperature, and I assume you don't run it that hot.
The static heat capacity of 700 gallons of water in an unpressurized tank is indeed around 850k BTU. The water in our tank will get up to 195 F. However, the dynamic capacity over the course of the day is around 1.2M BTU. That is because we are constantly drawing heat from the system to heat the house and periodically adding new wood to the boiler to replenish the heat that we used. If I add a phase change material to the storage tank then I could store even more heat. By replacing half the water in the tank with say paraffin (melting at 150 F) I could store 5 to 20 times what I store now. I have not needed to do this but it is interesting.
The 250 watts per hour per square meter of solar collector comes from the fact that the total energy collected is averaged over a 24 hour day.
You could add a wood burning boiler to your existing heating system and then use the original system as a backup. I still have my original natural gas fired heater with forced hot air although it never comes on.
Am I correct in understanding that 1.2M BTU is the daily energy use of your heating system? You weren't kidding about getting a good workout splitting wood. I suppose that would make 700 gallons a reasonable tank capacity, for carrying the building through 8 hours without reloading the furnace.
You're still adding an extraneous clause in the units. You want W/m^2 avg, where 1 W/m^2 avg = 86.4 kJ/day/m^2. Your 250 W/m^2 is substantially higher than my 15 MJ/day, but I'm trying to be conservative.
The output of the boiler is 115K BTU per hour. So theoretically, I could make 115K BTU x 24 = 2.76 MBTU per day. The static capacity of the 700 gal water tank is around 850K BTU. At any given instant the maximum amount of heat storage of the tank is 850K BTU
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I believe that biomass is best reserved for high-temperature applications. In my one-earth scenario, that's sufficient reason not to use it to reach a mere 50C. However, perfect may be the enemy of good. The best solutions I see for space heat aren't easy retrofits, and most US biomass residue probably isn't doing anything useful. In the near term, fuel substitution looks like a good idea.
Unfortunately, I don't believe it makes sense to commit pikans for the next 20 years to collecting and splitting wood, between classes. I suppose a dual fuel system is feasable.
How do you get the 1.2M BTU figure? It seems to me that 700 gallons at 100 C only carries 850K BTU above room temperature, and I assume you don't run it that hot.
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The 250 watts per hour per square meter of solar collector comes from the fact that the total energy collected is averaged over a 24 hour day.
You could add a wood burning boiler to your existing heating system and then use the original system as a backup. I still have my original natural gas fired heater with forced hot air although it never comes on.
-v-
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You're still adding an extraneous clause in the units. You want W/m^2 avg, where 1 W/m^2 avg = 86.4 kJ/day/m^2. Your 250 W/m^2 is substantially higher than my 15 MJ/day, but I'm trying to be conservative.
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