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ref: -0 tags: co2 capture entropy carbon dioxide date: 09-22-2019 00:46 gmt revision:1 [0] [head]

How much energy is thermodynamically required to concentrate CO 2CO_2 from one liter of air?

CO 2CO_2 concentration is 400ppm, or 0.4%. 1l of air is 1/22.4 or 44mMol. From wikipedia, the entropy of mixing is:

Δ mixS=nR(x 1ln(x 1)+x 2ln(x 2)) \Delta_{mix} S = n R (x_1 ln(x_1) + x_2 ln(x_2)) where x 1x_1 and x 2x_2 are the fraction of air and CO 2CO_2 (0.996 and 0.004)

This works out to 9.5e3J/K9.5e-3 J/K . At STP, 300K, this means you need only about 2.9J2.9 J to extract the carbon dioxide.

A car driving 1 km emits about 150g carbon dioxide. This is 3.4 moles, which will diffuse into 852 moles of air, or 19e3 liters of air (19 cubic meters). To pull this back out of the air then you'd need at minimum 55.3 kJ.

This is not much at all -- a car produces 100kW mechanical power, or 100kJ every second, and presumably it takes a minute to drive that 1km. But such perfectly efficient purification is not possible.

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ref: notes-0 tags: CO2 global warming carbon dioxide indonesia brazil date: 03-14-2008 21:34 gmt revision:0 [head]

From the New Yorker, Feb 25:

  • "Just two countries - Indonesia and Brazil - account for ten percent of the greenhouse gasses released into the atmosphere. "
  • "During the next twenty-four hours the effect of losing forests in Brazil and Indonesia will be the same as if eight million people boarded airplanes at Heathrow airport and flew en mass to New York. "

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ref: notes-0 tags: energy carbon CO2 hot water heater. date: 02-25-2008 23:36 gmt revision:2 [1] [0] [head]

How much carbon dioxide (CO2) is released to heat the water for a 5-minute shower?

  1. assumptions
    1. water enters your house at 45F, and you heat it to 100F.
    2. the energy efficiency of your hot water heater is 87%, and we ignore the cost of static thermal losses.
    3. you live in the southeast like me, which is predominantly powered by coal-fired plants. These plants release about 0.8kg/kwh of CO2 ref
    4. transmission of energy from the power plant to your home is 90% efficient
    5. you have a shower head that flows at a rate of 2.2 gallons/minute
  2. result: 2.2gpm -> 138.6 ml/sec -> * 31C temp rise -> 4.2kw -> 0.31kg CO2.
    1. that's about equivalent of driving 4 miles in a 30mpg car. (gasoline CO2 release = 2.4kg/gallon)

  • Interesting analysis. I'm surprised how much CO2 is used by those 5-minutes of delicious, delicious hot shower! --joeyo