Near-instant charging.

Irrelevant. You're still limited by supply rates and feed wire heating. Top end li-ion cells can charge in a matter of minutes on the small scale. In practice it's supply rate and cooling that limits you.

Much higher discharge rates

Irrelevant. What, you think cars have multi-megawatt inverters and motors? And again, top-end li-ions can have couple minut discharges.

and that without developing significant heat, because their series resistance is negligible

Slow charge and discharge of li-ions (normal usage) is usually over 99% efficiency. Fast charge is usually 94-97%. Fast discharge is irrelevant because the rest of the car can't handle using multiple megawatts at once (what, you think the car's going to get 0-100 times measured in milliseconds?) Older supercaps are less efficient than older li-ions due to an increase in the internal resistance (more in this in a minute)

Enormously more charge/discharge cycles than anything in battery tech

10 years-ish isn't good enough for you? Fine, reduce the depth of discharge to get 15-20 years. You'll still be an order of magnitude higher energy density than ultracaps.

you could will ultracaps used in a vehicle context to your children

You've been way overstating (and repeating a common mythology) about ultracaps. They don't actually last that long. Here's an info sheet from an ultracap manufacturer. Scroll down to "Life Expectancy".

The life expectancy of supercapacitors is identical to aluminum electrolytic capacitors ... Supercapacitors operated at room temperature can have life expectancies of several years

It's pure nonsense that they last forever. Some are rated for longer. For example Ioxus rates theirs at 10 years. But 10 years is pretty common for higher end EV battery packs, too.

This concept that ultracapacitors are something that you can "gift to your children" is just bull. They degrade, too. Following an exponential degradation curve dominated by increasing internal resistance.. So please stop with this nonsense.

Much wider range of usable performance over temperature; much colder, much hotter.

As per the above, operating out of the ideal temperature range cuts your ultracap lifespan. Commercial ultracaps aren't generally rated for wider temperature operating ranges than high-end li-ions, as you'll see from the various linked caps in this post, which are just a random sampling (for example, the Cooper Bussmann aerogel caps are only rated down to -25C, which is not impressive at all). And there's only a rather small range that's necessary for human-operated vehicles on the surface of the Earth. The ambient temperature outside isn't going to reach cold enough to liquify oxygen or melt zinc.

Much less need for recycling

Show me a single type of ultracap which can be recycled at all.

They can't be overcharged at their rated voltage

Overheating of the supercapacitor can occur from continuous overcurrent or overvoltage charging. Overheating can lead to increased ESR, gas generation, decreased lifetime, leakage, venting or rupture. .... General Safety Considerations: Supercapacitors may vent or rupture if overcharged, reverse charged, incinerated or heated above 150C

They have completely predictable, and 100% stable, discharge curves , so a five year old ultracap performs just as well as a brand new one,

False, as pointed out above, internal resistance rises with time.

In short, please stop with the standard BS mythology of what ultracapacitors are, because it's just not in accordance with reality.

The show-stopper is insufficient energy density

1 1/2 orders of magnitude worse volumetric energy density and 1 1/2 orders of magnitude worse gravimetric energy density, and even worse ratios on price and falling further behind... no, surely they're right around the corner from taking over! Let's ignore the fact that in the lab supercaps are struggling to reach the energy density of lead-acid while batteries are working on beating *gasoline*.... no, clearly the foreseeable future will be supercaps!

It varies, but I think I figured out that on my land it's going to work out to about 6-7 cents per incremental kilowatt hour. Power in my area is primarily geo, though in Iceland as a whole hydro makes a lot more. I think the conversion for gasoline prices is about $7.50 per US gallon.

Sounds like metal fatigue. You have to design to prevent that.

Surely you know that today's ithium ion technology is half an order of magnitude better energy density than when the tech was introduced, and it keeps improving every year. Yes the trend of battery energy density doubling every 8-ish years has continued under li-ion. Li-ion isn't a single chemistry, it's a family.

It's not simply electronics improvements that let the batteries in these devices keep getting smaller and smaller with each generation while battery life improves.

I don't get the obsession with ultracaps. Yes, they're advancing, but not faster than batteries. And they're 1 1/2 orders of magnitude behind on energy density, and even more on price. So why do people always seem to think they're the solution to everything?

Bottom line, though, is that battery tech isn't likely to continue to hold its ground for much longer

Citation needed. I follow battery tech pretty closely, and I see absolutely no signs of it slowing down; if anything, it seems to be speeding up, at each step, from theoretical concepts all the way own to commercialization of new technologies (for example, silicon anodes used to be only a lab tech, now they're starting to increasingly be used in commercial cells). There's many dozens to hundreds of majority improved li-ion anodes, cathodes, electrolytes, and membranes in the lab, in various stages of commercialization, from brand new to company-with-funding-is-setting-up-production-lines. And then there's a couple dozen different next-generation non-li-ion technologies. Li-air is usually the most heralded of these, offering the potential for greater range per kilogram than gasoline (even ignoring how dramatically smaller and lighter electric drivetrains are than gasoline drivetrains - not sure why people always ignore this when comparing "range"). However, li-air isn't my favorite; at least in the shorter-term, I'd say my favorite is probably lithium-sulfur. There's actually been a couple prototype devices powered by them, such as a solar airplane; they have superb energy density already but they need to get the lifespan up - which is precisely what's been happening in the lab.

Companies have been pumping water (usually wastewater or seawater) down wells since the start of the latter half of the 20th century, to restore pressure in oil reservoirs. So how is this anything new and anything connected with fracking?

Also, I don't unerstand why people make such a big deal out of these minor earthquakes which are general to small too feel even if you're paying attention for them. The amount of energy they're dealing with is only in the ballpark of these tiny quakes; compared to a large earthquake, it'd be like a mouse trying to push a boulder off a cliff. Either the boulder is ready to go or it's not, the mouse makes essentially no difference.

Normally I'd disagree with you, because most manufacturers these days buy so many of their parts from 3rd party manufacturers, they're the ones that profit from replacements. But given how much Tesla manufactures in-house, and how with each generation they keep putting more emphasis on keeping it all in-house, there may be some truth to that.

None of those things apply to the design. There's no drywall; the plans for the home are of a "steampunk" style, with conduits for wiring/piping visible but done decoratively. Hence replacing them doesn't involve ripping out drywall. It's a highly open floor plan; anyone in the future can put up additional walls if they want smaller rooms, but otherwise it's wide open.

As for why? If I'm building something, I want it to outlive me. I want future generations to see it. When most everything else from our current era is long gone, I want that which I did to still be standing. Is that so strange? It's like planting a sequoia. You'll never live to see it be a giant. But if you plant it in a place where it can thrive, it'll endure for people to enjoy for hundreds of generations.

Haha, brilliant! ;) It's a carbon offset program! ;)

No problem :) I first did my own research, then met up with the president of the Icelandic Concrete Association, who's pretty excited about the project, to discuss it further. The project is going to be unusual in quite a few ways, for example, it's going to be what's called an "umbrella earth home", and we're going for a natural cave/steampunk look to it (based on an idea that the concrete guy had, we're going to use high pressure water on the interior after the concrete sets to remove the outer layers of cement from the gravel, leaving it looking like rough rock on the inside). It may not be a first in the world, but it'll be a first for Iceland. :)

I've been thinking about the long term on everything with the project. For example, instead of drilling a well to pump from, I'm having the cold water come from a persistent natural spring up on the mountainside about half a kilometer away, naturally filtered through gravel and sand (my excavator operator is working on it as we speak, actually), so it takes no power to run and should last very well. Wells are standard where I am but I found I could get water from the spring for about the same price, maybe even less.

I'm not an expert, but the steel is protected from corrosion in most forms of concrete due to the mildly alkaline chemistry of the concrete.

Gee, I wish I'd written something like:

The cement carbonates at a relatively constant rate (give or take somewhat depending on various factors like moisture), a given depth per year, which brings it down to a more neutral pH, which then when it gets to the steel allows the steel to rust

;)

And if you throw on sacrificial metal [wikipedia.org], you can keep that steel corrosion-free indefinitely.

Galvanic protection of concrete is rather tricky versus something like a ship's hull, the electric potential depends a lot on its environment, even where it is in the structure, and if there's too little it doesn't protect and if there's too much you cause electrolysis of the water in the cement (it's a hydrate), which leads to hydrogen embrittlement of the steel. And it's usually not some single electrode, it's generally a lot of separate cast electrodes or are applied to the concrete as a coating, so it's a big issue to replace/redo. And if you don't, it rusts and falls apart.

I strongly prefer passively stable structures. :) Something that could be completely forgotten and still be there after a thousand years.

The question is not whether you "can", it's what it costs and what constraints it imposes. It's possible to make an EV that goes a good chunk of a thousand miles, it'd just be a totally impractical absurdly-expensive monstrosity.

No question that batteries are advancing - usually a gravimetric energy density doubling every 8 years or so. But the trend for volumetric isn't as impressive, and the price changes per watt hour are far less predictable. Sometimes the next generation which improves your battery stats is more expensive than the previous one. Sometimes it's cheaper. Overall the trend is negative, but it's very bumpy and not as fast.

I saw a Tesla store in Reykjavík the other day. Haven't seen a Tesla on the roads, but still, neat to know that they're here. :)

Shortening a car is usually bad for aerodynamics, which is bad for range. Lowering the roofline reduces the frontal area, which increases the range, but are you sure there'd be enough headroom if you did that?