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On paper that is sometimes true, and gas companies try to lean in hard on that. Gas can do 480 gCO2/kWh vs. coal's 800+. But when you include wellhead and pipel
by acidburnNSA 4y ago
On paper that is sometimes true, and gas companies try to lean in hard on that. Gas can do 480 gCO2/kWh vs. coal's 800+. But when you include wellhead and pipeline losses of methane they end up looking almost exactly equal, according to many studies. So it's not really progress. Also, half the CO2 of coal is nowhere even close to acceptable. We need things that do about 1/20th the carbon of coal or less, so wind, solar, nuclear, hydro, geothermal, tidal only. Gas is out.
- kragen 4y agoamusing units √(kilowatt hour / 480 g) = 2700 m/s √(kilowatt hour / 800 g) = 2100 m/s 480 g is 60% of 800 g so i guess my vaguely remembered percentage was about right wrt co₂ reduction i think carbon capture is probably going to be necessary
- acidburnNSA 4y agoGrams CO₂-equiv emitted per kWh of electricity generated are the units used by everyone, e.g. the IPCC to quantify the carbon intensity of energy sources. E.g. for a graph of data from IPCC, see [1]. Again, 480 is not all-inclusive. If you look at the whole system, gas is no better than coal, due to wellhead and pipeline leaks of methane, a potent greenhouse gas. [1] https://whatisnuclear.com/img/lifecycle-carbon-emissions-nolabel.png https://whatisnuclear.com/img/lifecycle-carbon-emissions-nol...
- kragen 4y agoi wish they'd use si units like kilograms per joule, or joules per kilogram, which works out to s²/m² and permits direct comparison with the energy density of fuels a kilowatt hour per 800 g works out to 4.5 megajoules per kilogram, which makes it easy to see that we're in the right ballpark (the energy density of coal itself is less than an order of magnitude higher) and that we're talking about delivered work rather than just thermal power
- acidburnNSA 4y agoI disagree. Sometimes when you're trying to quantify something specific, it's best to use units that are topical. If you want to talk about how much CO₂ the production of a kWh of electricity (not heat) that different sources of electricity use, mass CO₂ per kWh electric generated is the most useful and intuitive unit. Differences in thermal efficiency, etc. do not matter if you're focused on getting a kWh-electric for the smallest amount of lifecycle CO₂. This is especially important when comparing non-thermal sources (hydro, wind, solar) alongside thermal sources.
- kragen 4y agothe difference between kilowatt hours per gram and joules per kilogram also does not matter if you're focused on getting a kilowatt hour electric for the smallest amount of lifecycle carbon dioxide; a kilowatt hour per gram is precisely 3.6 gigajoules per kilogram, nothing more, nothing less. the only benefit of using the 'topical' units is an unnecessary risk of calculation errors and other kinds of confusion this nonsense about topical units is the reason that medieval merchants would measure certain kinds of cloth in flemish ells of 27 inches and other kinds of cloth in english ells of 45 inches; silver was weighed in troy ounces of 480 grains, drugs were weighed in apothecaries' drams of 60 grains (or apothecaries' ounces, which were the same as troy ounces), and foods were weighed in drams of about 27.3 drams, or avoirdupois ounces of 437½ grains kilowatt hours and grams per kilowatt hour are the modern equivalent of apothecaries' drams
- kragen 4y agoexcuse me, avoirdupois drams are 27.3 grains, not 27.3 drams
- legulere 4y agoThere’s also some methane emissions from coal that you need to consider.