4 ms·

Honestly what would be better for the environment? A lot of batteries that rarely if ever get used but still need to be replaced? Or storing a bunch of fuel in

Honestly what would be better for the environment? A lot of batteries that rarely if ever get used but still need to be replaced? Or storing a bunch of fuel in a tank? The backup generator should rarely be used. The resources that went into the construction of the generator and tank is probably much less than would go into all those batteries.

hedora 4y ago
I'm sure you're correct, but I'd love to see numbers to back this up. The union of concerned scientists has done this for electric vehicles, which is really useful. I'd also like to see it for low-hour-usage stuff, like tractors, lawnmowers, chainsaws, etc. (Though, honestly, electric chainsaws are way, way better than medium sized gas ones, CO2 footprint be damned.)
- Schroedingersat 4y ago
  The CO2 for the fuel is pretty easy to calculate. It's the 2-4kg or so per litre (depending on where it's sourced). We'll call the carbon footprint of a generator negligible as it's mostly Aluminum (20kg CO2e/kg new or 1kg/kg recycled and steel (2kg/kg), it's maybe 10kg/kW so max 200kg. It will be lost in our error for the dirty fuel source once we use 50kg or so of fuel. The carbon cost of keeping some fuel out of circulation is hard to quantify, and tanks are essentially free so I will call the capacity cost 0. ~3kg/kg for fuel is really convenient because when combined with ICE efficiency, it's about 1kg/kWh This https://climate.mit.edu/ask-mit/how-much-co2-emitted-manufacturing-batteries https://climate.mit.edu/ask-mit/how-much-co2-emitted-manufac... says every kWh of NMC causes 2-16t of emissions. I'm sceptical this applies in 2022 given that $130 only buys 5t of coal, but we'll use it as indicative. So for our generator we have 200P + 4E + 0C where P, E and C are power, total energy used and hours of capacity respectively. If we assume 2C charge rate and 4000 cycle life, our battery is 2400 * max(P/2, C) + 2400/4000E So E = 600C + 6/40E Assuming P is small compared to C, then any capacity used less than ~550 times in the 8 or so years it lasts is better off as a generator. This is a function of the carbon intensity of battery though. At 200kg (https://spiral.imperial.ac.uk/bitstream/10044/1/79316/2/Revised%20Manuscript%20%28clean%29.pdf https://spiral.imperial.ac.uk/bitstream/10044/1/79316/2/Revi...) it's about 50.
- postalrat 4y ago
  In this case though the generator won't be generally running unless external power is cut off. So it won't really be creating CO2.
justsomehnguy 4y ago
> that rarely if ever get used Oh, they would be charged and that degrades them. Also you can just buy more diesel and fill up the tanks but you can't do that with batteries.

hedora 4y ago

I'm sure you're correct, but I'd love to see numbers to back this up. The union of concerned scientists has done this for electric vehicles, which is really useful. I'd also like to see it for low-hour-usage stuff, like tractors, lawnmowers, chainsaws, etc. (Though, honestly, electric chainsaws are way, way better than medium sized gas ones, CO2 footprint be damned.)

Schroedingersat 4y ago
The CO2 for the fuel is pretty easy to calculate. It's the 2-4kg or so per litre (depending on where it's sourced). We'll call the carbon footprint of a generator negligible as it's mostly Aluminum (20kg CO2e/kg new or 1kg/kg recycled and steel (2kg/kg), it's maybe 10kg/kW so max 200kg. It will be lost in our error for the dirty fuel source once we use 50kg or so of fuel. The carbon cost of keeping some fuel out of circulation is hard to quantify, and tanks are essentially free so I will call the capacity cost 0. ~3kg/kg for fuel is really convenient because when combined with ICE efficiency, it's about 1kg/kWh This https://climate.mit.edu/ask-mit/how-much-co2-emitted-manufacturing-batteries https://climate.mit.edu/ask-mit/how-much-co2-emitted-manufac... says every kWh of NMC causes 2-16t of emissions. I'm sceptical this applies in 2022 given that $130 only buys 5t of coal, but we'll use it as indicative. So for our generator we have 200P + 4E + 0C where P, E and C are power, total energy used and hours of capacity respectively. If we assume 2C charge rate and 4000 cycle life, our battery is 2400 * max(P/2, C) + 2400/4000E So E = 600C + 6/40E Assuming P is small compared to C, then any capacity used less than ~550 times in the 8 or so years it lasts is better off as a generator. This is a function of the carbon intensity of battery though. At 200kg (https://spiral.imperial.ac.uk/bitstream/10044/1/79316/2/Revised%20Manuscript%20%28clean%29.pdf https://spiral.imperial.ac.uk/bitstream/10044/1/79316/2/Revi...) it's about 50.
postalrat 4y ago
In this case though the generator won't be generally running unless external power is cut off. So it won't really be creating CO2.

justsomehnguy 4y ago

> that rarely if ever get used Oh, they would be charged and that degrades them. Also you can just buy more diesel and fill up the tanks but you can't do that with batteries.