Useless measurement of the day

[fivemack]

If I reach down with a camera and take a flash photo of the gas meter, I can read the figures much more easily than if I bend down and use my eyes; also, I have a permanent record.

So now I know that it takes 1.15m^3 of gas, for which I pay 50p, to heat a languorous warm bath [1]. Possibly I need to get a better deal from my gas company.

Time for some nostalgic Elementary Chemistry. Natural gas is basically methane, molecular weight 16; I hope I can assume the cubic metres I'm charged for are of 1-atmosphere gas, so 0.024m^3 per mole, so 1.15m^3 is 48 moles, or about 750 grams.

Methane yields 900kJ per mole when burned, so 44 megajoules, which is enough to heat 100kg of water by, ah, 4.2kJ/kg/C, about 100C ... since I am not more thoroughly boiled than a lobster, I feel there's an inefficiency somewhere. I've no idea how much water there is in a languorous bath; my water is unmetered and my curiosity doesn't extend to filling the bath using a measuring-jug, and besides I tend to run some water out and run hot water in as the bath cools.

I've contributed 48 moles of CO2 at 44 grams per mole to the atmosphere, or rather over two kilos; offsetting this at a rate of £9 a ton costs about 2p per bath or three pounds a year, which makes me wonder why the gas company doesn't just offset all its CO2 emissions, produce an environmentally sound press release on recycled paper, and raise prices 5% to more-than-cover it.

[1] I cannot help thinking that I've misspelled that, and sung the praises of a warm bath full of large grey aggressive monkeys of the sort that haunt Indian railway stations. More, or less, fun than a barrelful of monkeys?

Comments

[shimgray.livejournal.com]

...so by my reckoning, it takes about twice as much gas as water to heat the bath. Something seems odd there.

[del-c.livejournal.com]

The answer is that while turning the Earth to shit is a trivially-neglectable externality, 5% extra cost does intolerable damage to shareholder value.

I think I've found what I'm going to be a crank about as an old man: corporate personhood and fiduciary responsibility. Everything I see wrong with the world, without exception, I see it comes back to that. I'm either right about that or the Brain Eater's got me, and neither prospect is very comforting.

[crazyscot.livejournal.com]

Gas is not a very efficient fuel, and it's not pure methane anyway. A lot of the heat produced by the combustion goes out the flue rather than into the water, and some heat is lost in the journey from boiler to bath.

[senji.livejournal.com]

The cost of CO2 emission offsetting would increase if that much of it was done.

[fivemack.livejournal.com]

How does that work?

My guess is that at the moment my CO2 emission offset is paying Georgia for closing down the Monumental but Inefficient Steel Works Imeni Josef Stalin, which they don't need much pecuniary incentive to do, or planting trees in Honduras.

Is something as small as nPower's contribution to Britain's domestic natural gas consumption going to fill every hillside in Honduras and close down every inefficient factory in the former Soviet Union, and force people to reduce CO2 emissions in some more expensive way?

[senji.livejournal.com]

As I understand it, and I could well be wrong, the current CO2 emission offset market is mainly picking off the very low hanging fruit, and with the very small demand for the product they're actually barely succeeding in funding the projects that they're doing. If the demand goes up a hundred-fold (which it would do if any major supplier started offsetting everything) then they'd actually have to look for projects, plus there'd be an incentive for them to charge just a little bit more to do the projects better.

[scat0324.livejournal.com]

Household gas supplied to the Eastern region yesterday had a calorific value of 39.2 (http://www.nationalgrid.com/uk/Gas/Data/misc/reports/calorificvalue.htm) megajoules per cubic metre, so actually slightly more energy than you calculated. Also Anglian think an average bath is 80 litres (http://www.anglianwater.co.uk/index.php?contentid=119#ptop) so less that you guessed.

Are you sure (http://www.thisismoney.co.uk/help-and-advice/article.html?in_article_id=413987&in_page_id=15) your gas meter reads in cubic metres?

[ipsi-digit.livejournal.com]

I think gas water heaters are just that inefficient. In a parallel linear flow heat exchanger like normal water heaters use, for draft purposes the pipe exhaust temperature will always be much warmer than the heated water. What heat goes up the flue pipe is wasted energy. If they were to use a counter-flow design instead the efficiency would be much better. But that requires a small fan to force the gases to move through the heat exchanger. I still think the overall efficiency would be greater, since small fans only need 20 to 50 watts,