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Comment by jonasvp | Hacker News Reader

You're making a big assumption that simply doesn't hold: it's not a matter of "let's switch to renewables and keep everything else the same". Fossil fues have an energy density that's unparalleled anywhere else in nature and most renewables are simply riding off of that (the machines, factories, trucks and ships producing and transporting wind towers and solar cells are not and won't be running on electricity). Read up on EROEI (energy returned on energy invested) if you're interested in the topic.

I just read a calculation how automatic milking machines will turn a tidy profit on milk into a loss with energy costs per kwh just 10 cents higher. Milking by hand will be _more_ profitable with that small a difference.

So it's controversial because doing something about climate change involves massive changes to our way of life. Not simply switching your SUV for a Tesla, we're talking up to and including economic collapse and deindustrialization.

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A 1GW coal plant requires a 100-car trainload of coal every three days.

A 1GW conventional nuclear plant is refueled by a single 18-wheeler truck, every year and a half.

A 1GW fast reactor or thorium reactor would require only one ton of fuel, about the size of a beachball, once a year. A lump of fuel smaller than a golfball would provide all the energy you need for your entire life, transportation included.

Fossil fuels still have the best energy density for cars and airplanes, but for large ships or anything stationary, nuclear is far superior. And not just for electricity; several GenIV designs run hot enough for process heat.

Retooling would be a better word. Saul Griffit (via Bret Victor[0]), calls switching to clean energy "more like retooling for World War II, except with everyone playing on the same team". The scale of expenditure and impact on the economy seems appropriate.

[0] - http://worrydream.com/ClimateChange/

Not to forget that WWII was a war won by oil. Whoever was able to mobilize the most energy (in the form of oil) could win (a great book about that: Oil, Power and War[0]). Retooling in the face of declining energy availability will be a different matter.

[0]: https://www.chelseagreen.com/product/oil-power-and-war/

We're not going to face declining energy availability for the next few decades. Fighting climate change is in big part a retooling of the energy production, which makes it tricky, but we still have enough dirty sources to burn to replace them with clean ones. Also, at least for now, we're not bombing each other's oil stores too much, so there's that.

Fossil fuels have an energy density that’s peanuts to Uranium. And lucky for us, there’s enough of it in the oceans to power humanity for centuries. If oil does get expensive enough and the ROI flips for economies of scale to apply to nuclear generation, we will have enough energy for SUV-sized flying Teslas in a century, no problem.

By the way, the EROEI of fossil fuel is terrible. Do you know how much energy was required to turn all that organic matter into oil? A single gallon of gas requires 98 tons of plants to grow, then be buried, and then pressured and heated until they become oil, then finally be dug out and refined.

Totally. This was a one-time gift of fifty million years of sunshine and we burned it all off over a time span of about 300 years.

Machine and factories producing solar cells don't run on electricity? What do they run on?

Diesel, fuel oil and coal. Admittedly, the latter mostly goes through a power plant to turn into electricity first - with the concomitant losses on the way.

EROEI of fossil fuels is pretty pathetic. It has been going down over time for the last 100 years. It won't take more than 30 years until oil hits an EROEI of 1. If you had followed any of the trends of renewable technology then you should be aware that economic collapse and deindustrialization are easily avoidable. Maybe there will be 10 days in a year that the most energy intensive factories will have to shut down due to a combination of low wind and solar but this also means on 10 other days in the year there will be an excess of energy.

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