After reading some of the threads on using electric heating elements to brew, I was curious how electric brewing compares to using a propane burner, both in terms of time and money. So, I did some thermodynamics homework and this is what I discovered. Feel free to point out any flaws you see. This wasnt my best subject although its nice to finally find a use for it.
First, here are a few definitions to establish a common framework for this discussion.
It takes 1 BTU/hr to raise 1 lb of water 1 deg F.
1 gallon of water weighs 8.3 gallons, so it takes 8.3 BTU/hr to raise 1 gallon 1 deg F.
1kW = 3414 BTU/hr
So, to raise 5 gallons of water from 60 F to boiling would require 5*152*8.3=6308 BTU/hr.
This analysis does not take into account any thermal loss (cooling) because the loss would vary based on outside temperature, material of the vessel, surface area of the opening, etc. Regardless if you use electricity or propane, insulating your hot liquor tank and brew kettle will help you achieve your target temperature more quickly and maintain that temperature with less energy.
Propane burners are rated on BTU/hour or simple BTUs. They range from 35k-200k BTU/hr. This is the amount of energy produced by burning the propane, but not necessarily transferred to heat the water. So, it is not a perfectly efficient transfer to your HLT or boiling kettle. There will be further loss from the vessel itself since it is not a perfect conductor. It is difficult to determine the actual amount of energy produced by the burning propane that actually makes its way into heating the water. Therefore, I will make an assumption that only 50% of the energy produced by a propane burner actually heats the water. A quick google search turned up the King Kooker turkey fryer produces 54K BTUs/hr. Adjusting for efficiency, the propane burner provides 27,000 BTU/hr (54,000*.70). Based on this value, the propane burner could bring 5 gallons of 60 F water to boil in 14 minutes (6308/27,000*60min). Obviously, a more powerful burner will heat water more quickly, but with greater fuel consumption.
Electric heating elements are usually measured in watts or kilowatts (kW). A 4kW heating element would provide 13,656 BTU/hr (remember, 1kW = 3141 BTU/hr). The electric heating element would be much more efficient at transferring its energy into heating the water because it is submerged in the water and has negligible loss. Therefore, the 4kW electric element could bring 5 gallons of 60 F water to boil in 27.7 minutes (6308/13,656*60min).
However, which heat source is more cost effective?
Propane contains 21,622 BTUs per pound. (www.propanegas.ca/FileArea/PGAC/Propane properties.pdf )
Therefore, a 20 lb tank of propane would have 432,440 BTUs of energy. That is enough to run your 54K BTU propane burner for approximately 8 hours. Assuming $20 per tank, propane use costs $2.50/hr.
According to my last electric bill, I paid $.18 per kilowatt hour after taxes and fees. Using a 4kW electric heating element for one hour would use 4 kW hours of electricity and cost $.72/hr.
Electricity is certainly less expensive to operate but more costly in terms of time. Using my example above, electric brewing would increase the time to reach strike temperature for your mash by 10 minutes (21 min for electric vs. 10.6 min for propane). It would take an additional 6 minutes to reach boil after the sparge (12 min for electric vs. 6.06 min for propane). Sparge water can be heated during the mash so there is no time savings associated with propane. Overall, for a 5 gallon batch, you can expect to save about 16-20 minutes using propane over electric.
The only drawback to electric brewing I can think of is ready-made equipment is difficult to acquire. Propane turkey fryers with 28-32 quart pots are commonplace and relatively easy to operate. From what I have seen on the forums, most electric brewers use home-made equipment that can be dangerous if you dont know what you are doing. If you chose to explore brewing using electricity, take appropriate safety precautions and understand the associated risks.
In conclusion, electric brewing offers an affordable alternative to propane. Although it may add a few minutes to your brew session, it offers the flexibility to brew indoors and in confined spaces where propane use would be unwise and likely dangerous. Finally, you dont have to worry about running out of propane, as I am sure we have all done or will do during a brewing session.
First, here are a few definitions to establish a common framework for this discussion.
It takes 1 BTU/hr to raise 1 lb of water 1 deg F.
1 gallon of water weighs 8.3 gallons, so it takes 8.3 BTU/hr to raise 1 gallon 1 deg F.
1kW = 3414 BTU/hr
So, to raise 5 gallons of water from 60 F to boiling would require 5*152*8.3=6308 BTU/hr.
This analysis does not take into account any thermal loss (cooling) because the loss would vary based on outside temperature, material of the vessel, surface area of the opening, etc. Regardless if you use electricity or propane, insulating your hot liquor tank and brew kettle will help you achieve your target temperature more quickly and maintain that temperature with less energy.
Propane burners are rated on BTU/hour or simple BTUs. They range from 35k-200k BTU/hr. This is the amount of energy produced by burning the propane, but not necessarily transferred to heat the water. So, it is not a perfectly efficient transfer to your HLT or boiling kettle. There will be further loss from the vessel itself since it is not a perfect conductor. It is difficult to determine the actual amount of energy produced by the burning propane that actually makes its way into heating the water. Therefore, I will make an assumption that only 50% of the energy produced by a propane burner actually heats the water. A quick google search turned up the King Kooker turkey fryer produces 54K BTUs/hr. Adjusting for efficiency, the propane burner provides 27,000 BTU/hr (54,000*.70). Based on this value, the propane burner could bring 5 gallons of 60 F water to boil in 14 minutes (6308/27,000*60min). Obviously, a more powerful burner will heat water more quickly, but with greater fuel consumption.
Electric heating elements are usually measured in watts or kilowatts (kW). A 4kW heating element would provide 13,656 BTU/hr (remember, 1kW = 3141 BTU/hr). The electric heating element would be much more efficient at transferring its energy into heating the water because it is submerged in the water and has negligible loss. Therefore, the 4kW electric element could bring 5 gallons of 60 F water to boil in 27.7 minutes (6308/13,656*60min).
However, which heat source is more cost effective?
Propane contains 21,622 BTUs per pound. (www.propanegas.ca/FileArea/PGAC/Propane properties.pdf )
Therefore, a 20 lb tank of propane would have 432,440 BTUs of energy. That is enough to run your 54K BTU propane burner for approximately 8 hours. Assuming $20 per tank, propane use costs $2.50/hr.
According to my last electric bill, I paid $.18 per kilowatt hour after taxes and fees. Using a 4kW electric heating element for one hour would use 4 kW hours of electricity and cost $.72/hr.
Electricity is certainly less expensive to operate but more costly in terms of time. Using my example above, electric brewing would increase the time to reach strike temperature for your mash by 10 minutes (21 min for electric vs. 10.6 min for propane). It would take an additional 6 minutes to reach boil after the sparge (12 min for electric vs. 6.06 min for propane). Sparge water can be heated during the mash so there is no time savings associated with propane. Overall, for a 5 gallon batch, you can expect to save about 16-20 minutes using propane over electric.
The only drawback to electric brewing I can think of is ready-made equipment is difficult to acquire. Propane turkey fryers with 28-32 quart pots are commonplace and relatively easy to operate. From what I have seen on the forums, most electric brewers use home-made equipment that can be dangerous if you dont know what you are doing. If you chose to explore brewing using electricity, take appropriate safety precautions and understand the associated risks.
In conclusion, electric brewing offers an affordable alternative to propane. Although it may add a few minutes to your brew session, it offers the flexibility to brew indoors and in confined spaces where propane use would be unwise and likely dangerous. Finally, you dont have to worry about running out of propane, as I am sure we have all done or will do during a brewing session.