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Comment by tajen | Hacker News Reader

But is it carbon-neutral now?

Let's remind the whole picture here: We want to come back to global greenhouse gases emissions on 1990, because they were balanced by nature's absorption. It often happens that the cost of building solar panels, transporting them to the location, disposing them before their estimated time-to-live and getting rid of all their chemicals emit more carbon than we save by using electricity from the solar panels.

Another bias is: By making energy cheaper, does it encourage the use of said energy, thereby offsetting the gains? "I've saved 20% of carbon emissions compared to having a petrol-based SUV" tells another story than "I don't have an SUV".

Greenhouse gas ecology is hard. The only way to avoid doing those analysis would be to tax carbon emissions for the side effects they produce. Then we would be able to just by the cheapest, which would also be the most energy-efficient.

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1) Anthropogenic CO2 emission rates in 1990 were greater than natural sinks could offset.

2) Under any reasonable set of assumptions, rooftop solar PV has significantly lower emissions per kWh than the cleanest fossil sources. In 2014 the IPCC estimated a median value of 41 gCO2-e/kWh for rooftop PV generation vs. 490 for combined cycle natural gas generation.

3) Perhaps some of the CO2 avoidance will be squandered eventually as solar becomes cheaper, thereby encouraging use of more electricity, but so far total electricity use is uncorrelated or even anti-correlated with the presence of rooftop solar generation. "Rooftop solar" and "energy-thrifty building construction/operation" cluster together, so far, rather than displacing each other.

2) Does that include the carbon cost of manufacturing, distributing and installing the tiles?

Yes. Hit up Google Scholar with "life cycle", "co2", and "photovoltaic" as terms if you want to understand in more detail.

This report looks pretty good if you want just one document: https://www.nachhaltigwirtschaften.at/resources/iea_pdf/repo...

It's from the International Energy Agency and it is recent (which is important, because commercial PV technology is evolving rapidly).

You have to manufacture, distribute, and install tar shingles too. Is there some reason to think these costs would be higher for solar tech?

I presume there's a difference in manufacturing between these tiles and normal tiles.

I also presume there's CO2 costs involved in manufacturing solar cells that aren't present in normal shingles.

Perhaps, although i'm quite skeptical about a difference in distribution and installation. And even in the case of manufacturing, one must only consider the delta between them rather than full cost of manufacturing solar.

Possibly. I'm sure solar is resource intensive. OTOH, tar shingles are literally made of petroleum, which is not great either.

You are missing the point. Super long term sustainable energy is very hard. 100% of focus needs to be on just getting the mass market this much closer.

Carbon neutral isn't even in the ballpark of highest priorities given ALONE how difficult this first step is. Carbon neutral will be the obvious next goal in ~1 decade when EV cars, home batteries, and solar panels are more commonplace.

Going for carbon neutral now is equivalent to over investing in solar panels 2-3 decades ago.

As far as I know consumer electricity usage has been on a downward trend for a long time.

Computers, TVs, washing machines etc are increasingly using less power. I think there are limits to how much we can waste. E.g. when food prices drops to half we don't buy twice as much food.

There was a good New Yorker article within the past 2 years that talks about the increase in consumption. One example it used was refrigerators. Back in the 60s, something happened where they got cheaper/more power efficient. Instead of a gradual reduction in power, it increased because people just put the old one in the basement to freeze more stuff. Same is true (I think) with traffic. If we were to make, say, traffic signals more efficient by synchronizing them, or somehow increase capacity on freeways, people would just drive more. Not saying all resources are like this, however.

> If we were to make, say, traffic signals more efficient by synchronizing them, or somehow increase capacity on freeways, people would just drive more.

Or say, invent self-driving cars...

I'm not sure if that's the point you are making, but I'm 100% certain that self-driving cars will increase the number of cars on the road, not decrease it.

That will just clog roads more, doesn't matter how much you mechanize it. Self driving cars will induce massive amounts of demand piled atop the latent demand that already exists for driving on nearly every arterial and freeway in cities, and even if everything was perfect, with cars driving at an optimal 45mph with minimal stopping distance, you can only move 2200 cars an hour per lane [1] and that scales non-linearly, as you add lanes to highways and arterial streets, throughput drops exponentially due to lane switching.

Now, self driving cars could get us closer to that 2200 cars an hour figure, but there is so much pent up demand for a magical faster option (latent demand) that when those marginal efficiency gains occur, there will be a flood of new vehicular traffic on the roads that will fully negate said efficiency gains, and likely exacerbate said issues since the tolerance for time spent in traffic will significantly increase for autonomous vehicle owners due to being able to do another task while your car drives for you.

[1] - http://www.fhwa.dot.gov/ohim/hpmsmanl/appn2.cfm

Indeed, that's the point I was hinting at: self-driving cars have the potential to increase carbon emissions, even the electric ones, due to increased usage and congestion.

Has Elon Musk publicly addressed this issue at all?

Self-driving cars are inevitable, so they may as well be electric. But if Tesla pulls the industry into the self-driving age before the majority of cars are electric they could actually be doing more harm than good. Perhaps self-driving cars should be required to be electric.

If we'll use them as "self-driving taxis" more than personal cars — if you're not attached to a specific "your" car — some nice things might start happening:

(1) multi-modal mass transit/car mixing becomes more attractive.

(2) transit can optimize for high-frequency mini/microbus formats rather than least-number-of-employed-drivers. this is less optimal from road-occupation POV but can be a win if it makes more people actually use transit?

(3) required parking space drastically decreases. Reaping the benefits will take a LONG time, but we'll be able to go back to denser cities?

This is called induced demand, whereby something that is plentiful will be utilized since it was built. Commonly, people say "Build it and they will come!" which is all the more true for roads.

Building a freeway or expanding it actually creates more traffic, since it lowers the cost of driving (time & gas) and when building a new freeway you actually create new traffic flows in unexpected ways. Building extra lanes actually causes more cars than those lanes could ever conceivably handle to pour onto the roadway due to the latent demand [1], and the most viable path forward is to create other avenues for said latent demand for transport to be serviced.

Ideally, you will build better mass transit infrastructure, with a sizable light rail network and feeder bus lines in the suburbs. Traffic will not get better due to this in any way, shape or form, but it will lessen the number of additional cars that end up traversing the streets every year, and prevent some additional load.

What this will do though is prevent your local economy from strangling itself in its own traffic, since your community is now providing more than one transport option. The only enemy of transit is density in the US, where we require massive swaths of land be set aside for unused parking that ultimately severely disadvantages every mode of transport, since it forces cities to be more spread out and dense construction to be very costly (underground parking construction costs are insane vs building above ground sqft).

[1] - https://www.wired.com/2014/06/wuwt-traffic-induced-demand/

From personal experience, I can tell you that I wasn't as anal about turning off lights in unoccupied rooms after switching to lower wattage bulbs. If someone left a light on in the basement, I'd figure it wasn't worth the extra trip down the stairs to turn it off -- especially if that light burning 24x7 only cost me a buck a month.

Although as a counterpoint, after getting a hybrid car, I'm not really making extra trips, even though it is saving me about $150 a month in gas. But that is more due to time budget than anything else.

It often happens that the cost of building solar panels, transporting them to the location, disposing them before their estimated time-to-live and getting rid of all their chemicals emit more carbon than we save by using electricity from the solar panels.

You think this happens with modern panels? Even low estimates put the EROI at something more like 4, with other people figuring 15-20 (of course it depends on where they are installed. EROI is better in Phoenix than Seattle).

> "I've saved 20% of carbon emissions compared to having a petrol-based SUV" tells another story than "I don't have an SUV".

or the inverse: "why should I feel guilty for my consumption since consuming resources is required to be alive?"

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