this post was submitted on 03 Mar 2024
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Discussion of climate, how it is changing, activism around that, the politics, and the energy systems change we need in order to stabilize things.

As a starting point, the burning of fossil fuels, and to a lesser extent deforestation and release of methane are responsible for the warming in recent decades: Graph of temperature as observed with significant warming, and simulated without added greenhouse gases and other anthropogentic changes, which shows no significant warming

How much each change to the atmosphere has warmed the world: IPCC AR6 Figure 2 - Thee bar charts: first chart: how much each gas has warmed the world. About 1C of total warming. Second chart: about 1.5C of total warming from well-mixed greenhouse gases, offset by 0.4C of cooling from aerosols and negligible influence from changes to solar output, volcanoes, and internal variability. Third chart: about 1.25C of warming from CO2, 0.5C from methane, and a bunch more in small quantities from other gases. About 0.5C of cooling with large error bars from SO2.

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Energy efficiency of active travel (walking, cycling, ebike) compared to an electric car (slrpnk.net)
submitted 9 months ago* (last edited 9 months ago) by [email protected] to c/[email protected]
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[–] [email protected] 1 points 9 months ago* (last edited 9 months ago) (1 children)

I think many people peddle just as hard on an electric bike, so the 5.5 kWh/km is a given, the rest is the energy required to go faster. Since air resistance increases with the square of the speed, it might very well be the case that 14 kWh/km at 25 km/h is more efficient than what the human alone would need to deliver for the same speed.

Edit: I failed to take into account that for the human at the same level of effort the power remains constant, not the energy per kilometer. Going faster at the same power output would reduce the energy expenditure per kilometer for the human to about 4 kWh/km, which would indicate that 10 kWh/km is being delivered by the motor to go faster.

That being said, it might be the case that they just calculated the energy needed to move the bicycle without taking the energy efficiency of the digestive system into account.

[–] [email protected] 5 points 8 months ago (1 children)

I just did a quick of my statistics. My bike typically provides an average of 100W in my hilly 28km commute (both ways) that takes about 1h15 minutes. That's less than 5Wh/km.

I'm using a fairly high setting, too, and judging by the fact that I don't break a sweat at all, I'm 100% sure I'm not pedaling as hard as I do on a regular bike.

[–] [email protected] 1 points 8 months ago

If my calculations are right, at that speed with the numbers from the graph, that would put the energy requirement at about 10 kWh/km. That means that with your motor delivering half of that, the human output actually matches up pretty well with the graph. I’m saying output, because I’m convinced that the graph doesn’t take the calories being burned into account and only shows the work being done to move the bicycle.