Check my calcs! How quick will electricity pay for itself?

[lschiavo]

3712 BTU needed (8lbs/gal * 8 gal * 58deg)
11000 BTU used (about)

34% efficiency.

Well, that is fairly close to your original estimate. The 75% manufacturer ratings obvioulsy do not reflect delivered efficiency. Is a burner really only 75% efficient itself?

Do you by chance have an aluminum pot to compare? Thermal conductivity of Aluminum is 237. 304 stainless is only 16.3. I think this would have to make quite a difference. I think with some pots they sandwich a layer of aluminum between stainless on the bottom for this purpose.

 

[DKershner]

Well, that is fairly close to your original estimate. The 75% manufacturer ratings obvioulsy do not reflect delivered efficiency. Is a burner really only 75% efficient itself?

Do you by chance have an aluminum pot to compare? Thermal conductivity of Aluminum is 237. 304 stainless is only 16.3. I think this would have to make quite a difference. I think with some pots they sandwich a layer of aluminum between stainless on the bottom for this purpose.

Lol, I have a crazy thin aluminum pot but I think the diameter is too small to fit on my stand, it would fall into the hole.

When I used to use it to make beer, the heating was crazy fast, but it also lost heat like crazy. Not bad for a boil/cool, but I wouldn't want it as a MLT/HLT.

The "Tri-Clad" or whatever you want to call them is made for even heat distribution over the bottom, not increased conductivity. The layer of aluminum spreads the heat over the whole source which then is transmitted slowly through the top layer of stainless. It is for scorching reasons, but mostly unnecessary for beer. Love it in my cooking pots though, though the middle layer is copper, not aluminum.

 

[shadowmage36]

lschiavo, what units are your thermal conductivities listed in? Those look close to what I know for those materials in W/m/*K, though I think your aluminum is a bit high and your stainless value is a bit low. Not by much, though, and you're certainly in the right order of magnitude.

 

[Ichthy]

Kershner

This may be a tad off topic but thought I'd throw this out there. If you're wanting to save money on propane I may have a solution depending on your setup.

I use a turkey fryer with the original stand and brew 5 gal batches. I noticed that a bunch of heat was pouring out of the sides and bottom of my stand. I bought some roof flashing and all-thread to make a heat shield. I bolted the all thread to my stand's legs (for the flashing to rest on) and made a cylinder out of the flashing that is tall eneough that my kettles are entirely enclosed (up to the handles). The flashing extends below the factory wind guard. I now use ~2-3 lbs of gas per brew session now and I'm starting with 50F water. The $8 I spent on flashing and all-thread paid for itslef in about two brew sessions.

Don't know if this will be of use for your setup, but it made my brewery a hell of lot more cost effective.

Cheers

 

[DKershner]

Ichthy, a wind screen is a cost effective way to get more heat to the pot, no doubt. I already have a pretty ideal setup as far as wind screening and heat direction is concerned, about 5 1/2" but for a turkey fryer it is truly a great idea.

Thank you for helping though, but the idea is not how to make my propane setup better, but more to explore other opportunities. If anyone has any ideas on how to improve the setup like ichthy did, I am always open though.

So you have an idea:

 

[lschiavo]

lschiavo, what units are your thermal conductivities listed in? Those look close to what I know for those materials in W/m/*K, though I think your aluminum is a bit high and your stainless value is a bit low. Not by much, though, and you're certainly in the right order of magnitude.

I just did a quick google to compare. I cant find the site again but I believe those were the units.

 

[artbrau]

I always assumed nat gas is cheaper than electric (I know most of the comments refer to propane) but I was really struck by the observation that in a HEx setup all the heat has to go through the liquid before it can be "wasted" while it is is obvious that my gas burners are heating more than just the liquid - How much more is the 64 kwh question. I don't know how to measure it but I did the basic cost calcs. Gas heat wastage has to be enormous the justify the cost difference! Here's what I found in Northern NJ:

Electric cost: $0.1703/kwh
Gas cost: $1.2389/therm
1 therm = 29.31 kwh

So 1 therm of electricity costs about $5.00! Zoiks! That's a 4x cost advantage for gas.
Does that seem right?

I can piss away 3 units of gas for every one that goes into my brew before electricity is competitive. With that fact it doesn't seem like I have to get too crazy measuring thermal efficiencies of my system. It would not change the result.

I need to figure out how to power my TV with gas.

 

[lschiavo]

I always assumed nat gas is cheaper than electric (I know most of the comments refer to propane) but I was really struck by the observation that in a HEx setup all the heat has to go through the liquid before it can be "wasted" while it is is obvious that my gas burners are heating more than just the liquid - How much more is the 64 kwh question. I don't know how to measure it but I did the basic cost calcs. Gas heat wastage has to be enormous the justify the cost difference! Here's what I found in Northern NJ:

Electric cost: $0.1703/kwh
Gas cost: $1.2389/therm
1 therm = 29.31 kwh

So 1 therm of electricity costs about $5.00! Zoiks! That's a 4x cost advantage for gas.
Does that seem right?

I can piss away 3 units of gas for every one that goes into my brew before electricity is competitive. With that fact it doesn't seem like I have to get too crazy measuring thermal efficiencies of my system. It would not change the result.

I need to figure out how to power my TV with gas.

Your calcs seem correct. Your electric rate is about 25% higher than mine so that makes quite a difference to start

 

[lschiavo]

U

I always assumed nat gas is cheaper than electric (I know most of the comments refer to propane) but I was really struck by the observation that in a HEx setup all the heat has to go through the liquid before it can be "wasted" while it is is obvious that my gas burners are heating more than just the liquid - How much more is the 64 kwh question. I don't know how to measure it but I did the basic cost calcs. Gas heat wastage has to be enormous the justify the cost difference! Here's what I found in Northern NJ:

Electric cost: $0.1703/kwh
Gas cost: $1.2389/therm
1 therm = 29.31 kwh

So 1 therm of electricity costs about $5.00! Zoiks! That's a 4x cost advantage for gas.
Does that seem right?

I can piss away 3 units of gas for every one that goes into my brew before electricity is competitive. With that fact it doesn't seem like I have to get too crazy measuring thermal efficiencies of my system. It would not change the result.

I need to figure out how to power my TV with gas.

Your calcs seem correct. Your electric rate is about 25% higher than mine so that makes quite a difference to start with.

You likely aRe "pissing" away up to 75% of the gas you are burning. That would depend on your system of course. If that were the case gas and electric would be about equal for you. No motivation to change.