Comment by dragontamer | Hacker News Reader

Comment by dragontamer | Hacker News Reader

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The benefits of a car were immediately obvious as soon as supply lines were considered. Feed for horses was something like 30% of all deliveries in a horse-based supply chain.

Railroads run off of coal, but steam-engines were huge. ICE engines were miniature engines that also ran off of a fuel source (eventually settling upon oil, but many different fuel sources were considered in those early days, including electricity).

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Such benefits are not immediately obvious with solar/wind. In particular, USA doubles its electricity usage each day, and then it shrinks down to 50% by nightfall (which does NOT time with the sun, its slightly offset: the 5pm sun loses most of its solar-power but homes are still hot and using a ton of electricity for A/C)

As a baseload plant, solar/wind, even with storage, is a bit unreliable. That's fine, they're a cheap source of energy but you need to consider things like hurricanes: winds too fast so you need to shut off the wind plants (otherwise they'd spin too fast and damage themselves), and the cloud cover so thick you lose most of your solar power.

Since there's no storage mechanism that lasts for days (ex: hypothetical hurricane), you end up needing to build a 200MW gas turbine ("just in case"), +200MW of clean energy.

Note: this is fine. This is probably the best path forward for now. But nuclear is reliable and doesn't need this "natural gas assist". Even if a hurricane sweeps over an area, the nuclear power plants will keep working.

EDIT: The issues come up if someone builds 200MW of solar panels / wind but fails to build any "just in case" energy sources. Which is happening. Their grids will fail when solar/wind inevitably cuts off.

"But nuclear is reliable and doesn't need this "natural gas assist". Even if a hurricane sweeps over an area, the nuclear power plants will keep working."

Actually, they don't.

"As a precaution measure, the reactor shall be shut down at least two hours before the hurricane’s strong winds arrive at the location. Generally this happens when the speed reaches between 70 and 75 mph (between 113 and 121 km/h)." (https://www.foronuclear.org/en/nuclear-power/questions-and-a...)

Also, they need electrical power to keep the reactor cool---typically the power grid and co-located diesel generators, not necessarily the best redundant backup system.

It’s only the older designs that need active cooling.

https://www.technologyreview.com/2019/02/27/136920/the-new-s...

Given how long it took Fukushima to cool down, does this actually do anything appreciable in the two hours before arrival?

I believe it means that, 2 hours before arrival, the reactor is off. Dead. Not generating heat.

They'd need to start shutdown sometime before that.

> ICE engines were miniature engines that also ran off of a fuel source (eventually settling upon oil, but many different fuel sources were considered

Fun fact - Rudolf Diesel's first engines were running on cooking oil. In fact, many diesel engines can operate on vegetable oils without modifications (not long term though). That sounds odd, but from the perspective of "burn hydrocarbons to generate heat", petrol, diesel, oil, body fat, coal or kerosene are all very similar to each other.

Here's a classic Top Gear on it: https://www.youtube.com/watch?v=1lqCwNReU1Y

No, horse breeders argued the supply lines favored horses as horses could be fed by unlimited biofuels instead of limited fossil fuels. Of course, there was a difference in scale, but it’s just false to claim there weren’t major naysayers about automobiles from the horse industry.

People thought fossil fuels were a finite resource back then?

I mean, I wouldn't be surprised if someone thought that, but given the frequency with which oil was being discovered, it seems reasonable that people would have assumed it to be effectively unlimited.

IIRC, people did think we were going to run out of coal back then. A minority, but yes, I do recall some quotes from the 1800s about the exponential growth of coal usage and that people were using too much coal.

But by the time ICE engines were getting invented, it was a done debate IIRC. Horses used to pull trains after all, the steam engine replaced horses in train-usage decades earlier (https://en.wikipedia.org/wiki/Wagonway, for the animal-based predecessor to trains)

Even in the late 1800s when cars were just starting to be used, the ultimate scarcity of fossil fuels (including coal) was explored by Jules Verne who suggested hydrogen as a successor fuel in The Mysterious Island. And local scarcity of fossil fuels was acknowledged since everyone knew that oil wells started reducing output after a few years.

Nikola Tesla spoke glowingly about how we don’t need coal, oil, or gas if we just harness the energy around us (what he meant here was quackery, unfortunately, but wind and solar accomplish very much the same thing). People understood from the beginning that coal, oil, and gas are finite.

First time I've ever heard this claim about horse naysayers. Do you have citations?

Interesting off-topic: according to Vaclav Smil, the number of horses in the USA peaked in the 1930s. In Europe, later still. David Edgerton's book The Shock of the Old talks about horses as well, among other "outdated" technologies.

I wonder if it’s possible to create air conditioning that generates electricity. It seems like you’re removing energy from the air.

Do you mean a heat engine?

Because the "opposite" of air conditioning is just a heat engine (taking "hot" and "cold" source, and using the difference to generate locomotion). In fact, all engines are glorified heat engines: be it a steam turbine, ICE, geothermal, or whatever

When air gets hot, it expands. When air gets cold, it contracts. So heat up air through some mechanism (hot side) to push a piston up. To pull the piston down, either use momentum or the cold-source (cold air contracts, pulling the stuff down).

The sterling engine is the best general purpose demonstration of this, and you can buy such engines for $20 to $100 or so.

ICE engines use gasoline as the hot source. Steam engines use steam (water at 100C) to transfer the heat from the hot source to the needed locations (heat can be from nuclear, coal, or other sources)

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Air conditioning is just this process in reverse. Expand the air forcibly by applying force to the piston. This cools down the air. "Gather" the coldness through some mechanism, which heats up your air inside the A/C unit while cooling whatever is on your "cold plate".

Push the hot air and compress it down. This heats up the air even further: "transfer" the hotness through some mechanism (aka: heat something else up, like the air outside the house). This cools down the air inside your A/C unit.

Now find a fluid that's more efficient at this process than oxygen. Then realize that fluid is terrible for the Ozone layer and write a regulation for a newer, crappier fluid that's less damaging to the Earth, and you have modern A/C units.

> It seems like you’re removing energy from the air.

You're just transferring the hotness somewhere else. Go feel the air that your refrigerator outputs: its far hotter than the air inside. If you measure the energy, its the energy that was "stolen" from inside the refrigerator + the energy "spent" on the heat pump (that compression / decompression cycle takes work, and work generates heat)

We can transfer heat around, but it costs energy. Alternatively, a difference in heat can be used to gather energy, but it will "Average" the temperatures and eventually the hot-source and cold-source will be the same temperature.

We can use fuels to make the hot-source stay really, really hot for long periods of time (as long as we have a source of fuel), and that's basically the design of steam engines / heat engines.

Think of it like water flowing down a hill. The heat is in your room because it flowed down to a cooler space with less energy, just like the water flowed down to a space with less potential energy. Moving that heat back to a higher energy area, back outside, is the same as pumping the water back up a hill. It always takes more than one unit of energy to move one unit of energy back “up”. You can only capture energy if it’s moving “down”.

You might enjoy a physics course, especially if you enjoy calculus, although an entry level course won’t require it.

That’s a great analogy, thanks!

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