this post was submitted on 03 Sep 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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The thermodynamics of electric vs. internal combustion cars (www.theclimatebrink.com)
submitted 1 week ago by [email protected] to c/[email protected]
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[–] [email protected] 11 points 1 week ago* (last edited 1 week ago) (1 children)

I realize the energy still has to come from the traction battery, but don't most EVs use heat pumps now? The energy use would be the same as using the A/C in the summer (though the battery does have less "oomph" in the winter due to ambient temperature).

My hybrid just uses the engine block as a heat source and storage (coolant pump is electric and circulates coolant through the warm engine block when it's in EV mode and occasionally kicks the engine on to warm it back up when needed). I think the coolant also loops through the motor controller and DC-DC converter which adds a little heat, but not really enough to heat the cabin with alone.

I wonder if it would make sense on EVs to have some kind of "chargeable" thermal mass you could pre-heat while it's charging and extract as you drive (and/or acts as a reservoir the heat pump can draw from)

[–] [email protected] 7 points 1 week ago* (last edited 1 week ago) (2 children)

Yes, heat pumps are really common in new EVs, but I'm not sure if it's most worldwide or not.

Your idea about thermal storage is interesting; I'm very much unclear on whether it would make sense to do that or simply have a bigger battery or some amount of insulation on the passenger compartment.

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

Adding thermal storage would require mass to be added, unless some existing component could be converted to dual-purpose. More mass in an EV means lower range and an increase in the already high vehicle weight.

[–] [email protected] 2 points 1 week ago

And I can't imagine the thermal accumulator + insulation would have a higher energy intensidensity than just the battery alone.

[–] [email protected] 4 points 1 week ago* (last edited 1 week ago) (1 children)

After thinking about it a bit more, a bigger battery would probably be the most practical.

Using my hybrid as a reference point (it uses the whole engine as a thermal mass for heat storage), the stored heat only lasts about 5-10 minutes at most before the engine kicks back on to warm it up again (the controller lets it cool to the lowest "operating" temperature for efficiency). If it could use the full stored heat in the engine, it would probably only be good for another 5 minutes at most. Granted, it's using that heat directly with a traditional heater core rather than feeding a heat pump.

Given that it would be used seasonally and be "dead" weight the rest of the year, I'm not sure adding a thermal mass would be all that practical unless it's something that can be heavily insulated and super-heated beyond the temperatures engines run at or has an additional year-round use.

The only downside to a larger battery is purely a human perception/marketing issue. The extra battery capacity would most likely be advertised in the range, and people would still probably be upset about the reduced range in the winter. It would have to be, ideally, not factored into the range and act as a "reserve" capacity.

Regardless, yeah, better cabin insulation would also help, to a point.

I just work around the problem by not running the heat most of the time (barring the need to defrost/defog). Most of my trips are short, so I just wear my coat/gloves and deal with the cold lol.

[–] [email protected] 2 points 1 week ago

How about using the thermal mass for both heating and cooling? Too bad EVs don't have throwaway power like hybrids, could use the excess to heat/cool the mass as necessary. Probably still not as efficient as raw power storage.

[–] [email protected] 1 points 1 week ago (1 children)

Tangentially, I was looking at the cost of converting an existing house in Arizona to be entirely off-grid solar. The average single-family detached house in the US south uses 16,000kWh annually (the south uses more energy overall than any other region of the country). If I bump that figure up to 20,000kWh--which should allow for a purely electric home with zero gas for heating or cooking--and then plan a system that can produce 200% of my projected power needs, then I need a solar array that's about 30x30 (assuming roughly 20% efficient microcrystalline cells). (The actual array size varies based on where you are installing, since different areas have different annual amounts of sun; being able to produce more power than you project means that you're still producing power on more overcast days.) The solar panels to do that are about $18,000 right now, and have a projected lifespan of 25-40 years, with a .5% loss of efficiency annually. If my current power bill is $100/mo (it's actually more), and I'm currently using about 10,000kWh annually (which I am, but I also heat with a wood stove and have a gas stove for cooking), then over 25 years my electric bill is $30,000, which far exceeds the costs of the solar array alone, for less power.

Food for thought, y'all.

OTOH, living in Arizona has other problems, like, being hours from fucking anywhere, and water.

[–] [email protected] 0 points 1 week ago (1 children)

Rather than doubling your system generation size, it would be better to store the generated electricity. You can have a massive system, but it still won't generate anything at night.

[–] [email protected] 3 points 1 week ago

Two points. First, yes, you need batteries, that kind of a given. Second, increasing the systems generation size means that you can charge batteries while also consuming power. Third, increased generation system size means that you'll still be generating sufficient power during the rare times that southern Arizona is overcast.

You would generally want to be as energy efficient as possible though, because being off-grid does make you vulnerable to insufficient generation capacity at any given time.