I don't see how installing underfloor heating in an existing house can make economic sense. Additionally in older houses the windows tend to be a bit leaky, so the radiators being under the windows is important to prevent unpleasant cold drafts.
Yes, the heat pump will take an efficiency hit for using radiators rather than underfloor heating. I'd say that's just part of the cost of living in an old house.
My father has a wood burning boiler connected to the same water circuit that heats the radiators as his air-water heat pump. Originally when the house was built it was a wood-oil combi boiler, later on the oil burner was ripped out and the heat pump installed (at that point there were government grants available for replacing oil heating with heat pumps).
It does work well, and when it gets cold in the winter and the efficiency of the heat pump drops, he burns wood. But honestly the system is a jungle of pipes and valves, and the guys who did the heat pump installation were unable to wrap their heads around it. Luckily my father is a handy guy so he was able to do it himself.
But I'm thinking if one were to do something like this from scratch, without the history of the existing boiler already being there and installed, I wouldn't bother with it. Just have a few good old school wood stoves with significant thermal mass (masonry heater or whatever you call them in the US) in the house that you can use to provide extra heat when it's cold, and as backup in case there's an electricity outage.
My father has a Mitsubishi air-water heat pump, generating hot water for the iron radiators in the house. Uses R32 refrigerant, not CO2 as in this article, but still. While efficiency is reduced by the need to have decently high temperatures in the radiators, it's still decent-ish. IIRC he still gets a COP of around 2-2.5 when it's -15C outside.
This is in Europe, might be different on the other side of the pond.
I believe there are propane using split AC systems where propane is used only in the outside unit. The outside unit has a heat exchanger transferring the heat to some glycol-water solution which is what then circulates through the inside unit.
If you do positioning in degrees, minutes, and seconds (or decimal minutes which I guess is more common nowadays), a 'natural' length unit for navigation is a minute of longitude, which is the original definition of the nautical mile. And then we get velocity as nautical miles per hour, or knots.
Blame the French for reinventing the wheel instead of, say, using a 1/1000th of a nautical mile as the definition of the metre. Alas, that's all water under the bridge by now.
If you want to do navigation in SI units, the UTM projections (see sibling thread) typically do positioning in metres inside each grid square.
Funnily enough the metre is defined by the globe as well: the arc from the equator to North pole is defined as 10,000 km. I think this might be where the alternative angle metrics came from, which went with the metre:
full circle is 400 grad, so a right angle (10,000 km) is 100 grad.
Then minutes and seconds are factors of 100, so a centesimal minute is 1 km and 1 centesimal second is 10 m.
Originally it was defined like that, but it was fairly quickly redefined as the distance between marks on a prototype platinum bar. It's had a couple of other definitions since then, but it's currently defined "by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit ms⁻¹, where the second is defined in terms of the caesium frequency ΔνCs".
Yes technically speaking there is a different physical reference now but that's where it came from. A bit like how 1 ft is now 304.8mm but that's because it's the size of a human foot (with some historic details no doubt).
> that isn't a change to the definition of the meter
How is it not? it's not a change to the actual distance (well, it is for a sufficient precision), but a change to the definition of the metre is exactly what it is. It's defined relative to the speed of light rather than a random platinum bar length, with the constant picked so that the actual measurement stay the same (up to a certain level of precision).
> What has changed here to make them competitive again?
The article has to be read carefully. "On Actinide's engineering estimates, a single Fortitude machine would provide roughly half the isotope-separation capacity of the U.S. government's current electromagnetic fleet."
The "U.S. government's current electromagnetic fleet" is tiny. Oak Ridge is building a modest plant.[1] Idaho has a benchtop-sized separator. That's what Actinide is comparing against. Not the rows of basketball court sized calutrons from WWII. So the announcement gives the impression of a larger operation than it really is.
> Speaking of which, whatever happened to laser enrichment? That was apparently very promising at some point?
That is a very good question. A company called Silex, and their subsidiary Global Laser Enrichment, has been trying to commercialize this for years.[3][4]
Exactly how they do this is classified.[5]
There's another startup in this area, crawling along, underfunded, but building something.[6]
Meanwhile, URENCO continues to operate a centrifuge plant in New Mexico.[7] URENCO is a
a European company, and seems to be the leader in centifuge technology. Units in France, Germany, the Netherlands, and the US.
I've been expecting something big to happen in the laser enrichment area since the 1990s, but it never has. This suggest that it either doesn't work very well or is being suppressed because it works too well.
A friend of mine was involved with AVLIS and Pu-AVLIS. There were/are significant counterproliferation concerns with them. I'm not sure if that has anything to do with the lack of major commercialization, but I wouldn't find it shocking if it were true. As I understand it, it's one of those technologies that the US doesn't strictly need, but we really don't want the Iranians (or similar weapons-pursuing state) to have it.
It's a U.S. national security policy to prevent countries which don't already have capabilities to enrich uranium or reprocess spend nuclear fuel from aquiring such capabilities.
Technologies which have low energy consumption and need only small space and therefor are easier to hide, such Laser isotope separation, US wants to restrict to any country, even allies.
>"A centrifuge plant does one thing, costs billions, and takes years to stand up. Our machines cost a few hundred thousand dollars, produce material within months, deploy anywhere, and are able to be reconfigured in a matter of days to separate various isotopes as they are needed," said Robert Mendelsohn, co-founder and CTO of Actinide.
The obvious thing to consider is throughput and yield/loss. A centrifuge plant can produce kilograms of material and doesn’t fundamentally misplace any material, although it may struggle to extract all the inputs that are the correct isotope. A calutron needs to ionize every single atom, accelerate it to an appropriate energy, deflect it, and decelerate it without losing it. And it needs to deal with inadvertently multiply-charged ions. And if you’re dealing with radioactive source material, you need to deal with the atoms that embed themselves in your apparatus.
At least uranium isn’t actually all that radioactive.
This is a bit uncharitable to the concept of a centrifuge here. The Iranian nuclear program seems to have centrifuges that are a lot smaller and cheaper, and you can certainly build one that meets these needs.
yeah they don't talk about cleaning them either... that's a massive problem in this kind of ion separation techniques, things splatter and stick everywhere.
> What has changed here to make them competitive again?
Nothing. This is a company that specializes in making medical isotopes, which is something Calutrons are good for - you need high levels of enrichment in a single step, you don't need to process large quantities, and the energy consumption doesn't matter. Any talk of using it for reactor fuel production is pure PR spin.
Take these numbers with a grain of salt because I got them by chatting with AIs, but if you're producing electricity from HALEU, then centrifuges require reinvesting <1% of the output, whereas historical calutrons required 200% (useless) and modern technology could potentially bring that down to 10%.
So calutrons will always be less energy efficient than centrifuges, but if the capital cost and construction time is low enough, calutrons might still be economically viable.
But you weren't going to ask the LLM, and now you know something you weren't aware of. Seems no different than someone reporting what they found out in a Google Search, as long as they disclose that they used an LLM (as long as they used one that actually searches the web, but pretty sure even ChatGPT Free does that these days).
> but pretty sure even ChatGPT Free does that these days).
It can do, but won't do so reliably; and the guessing it does if it's not grounding with a search is still like someone in a pub saying "I recon…". Admittedly, a Cambridge pub like the Carlton Arms used to be when I lived there (sometimes I'd be the only one at the table who wasn't studying for a PhD), but still, pub.
Even if you ignore my LLM numbers, "what percent of a reactor's output must be reinvested to enrich its own fuel?" is a meaningful contribution to the discussion.
But are your numbers reliable? By your own admission you don't know. So you aren't contributing expertise but rather the brief use of a tool that everyone has ready access to and which doesn't necessarily return reliable answers. AKA noise, at least from the perspective of a community like HN.
This site is intended to be a discussion between people. If we wanted to consult some other resource, we would go do that. Injecting unverified information is not a contribution to a discussion between people, especially if it isn't coming from a human source.
A number of years ago I implemented xoshiro256** for the GFortran compiler. Previously it used Marsaglia's KISS generator, which wasn't bad but perhaps no longer state of the art on the TESTU1 etc. tests. Additionally, xoshiro256** can be used in parallel by multiple threads; that took a bit of clever hacking to work around the limitations of the Fortran intrinsics API.
A lot of jurisdictions have laws that say electric cars must emit thatbnoise while driving. Which is basically because you might not be able to hear them over the louder sound of gas cars. I hope that that requirement can go away if we get to near 100% electric.
Yes, the heat pump will take an efficiency hit for using radiators rather than underfloor heating. I'd say that's just part of the cost of living in an old house.
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