• 16 Posts
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Joined 1 year ago
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Cake day: June 11th, 2023

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  • Summary:

    But then, in the geologically abrupt space of only a few decades, this great river of ice all but halted. In the two centuries since, it has moved less than 35 feet a year. According to the leading theory, the layer of water underneath it thinned, perhaps by draining into the underside of another glacier. Having lost its lubrication, the glacier slowed down and sank toward the bedrock below.

    /…/

    “The beauty of this idea is that you can start small,” Tulaczyk told me. “You can pick a puny glacier somewhere that doesn’t matter to global sea level.” This summer, Martin Truffer, a glaciologist at the University of Alaska at Fairbanks, will travel to the Juneau Icefield in Alaska to look for a small slab of ice that could be used in a pilot test. If it stops moving, Tulaczyk told me he wants to try to secure permission from Greenland’s Inuit political leaders to drain a larger glacier; he has his eye on one at the country’s northeastern edge, which discharges five gigatons of ice into the Arctic Ocean every year. Only if that worked would he move on to pilots in Antarctica.

    It’s not wild at all. :) The plan makes sense from a physical perspective, but should not be implemented lightly because:

    • it’s extremely hard work and extremely expensive to drain water from beneath an extremely large glacier
    • it doesn’t stop warming, it just puts a brake on ice loss / sea level rise

  • If the motor mount is hackable with reasonable effort, and the motor controller’s interfaces are open, then in principle… yes.

    Yet in reality, companies build extremely complicated cars where premature failure of multiple components can successfully sabotage the whole. :(

    I’ve once needed to repair a Mitsubishi EV motor controller. It took 2 days to dismantle. Schematics were far beyond my skill of reading electronics, and I build model planes as an everyday hobby, so I’ve seen electronics. Replacement of the high voltage comparator was impossible as nobody was selling it separately. The repair shop wanted to replace the entire motor controller (5000 €). Some guy from Sweden had figured out a fix: a 50 cent resistor. But installing it and putting things back was not fun at all. It wasn’t designed to be repaired.

    Needless to say, replacing a headlight bulb on the same car requires removing the front plastic cover, starting from the wheel wells, undoing six bolts, taking out the front lantern, and then you can replace the bulb. I curse them. :P

    But it drives. Hopefully long enough so I can get my own car built from scratch.



  • Interestingly, warfare also has the effect of:

    • causing houses to be abandoned, necessitating houses elsewhere while the abandoned ones likely get bombed

    • decreasing the number of future consumers, whose future footprint would depend on future behaviour patterns (hard to predict)

    • changing future land use patterns, either due to unexploded ordnance or straight out chemical contamination (there are places in France that are still off limits to economic activity, because World War I contaminated the soil with toxic chemicals), here in Estonia there are still forests from which you don’t want trees in your sawmill because they contain shrapnel and bullets from World War II

    I have the feeling that calculating the climate impact of actual war is a difficult job.

    But they could calculate the tonnage of spent fuel and energy, that would be easier.







  • The transfer to electricity could be done by using the heated mass to heat a hot pumped liquid or using transfer rods made of a solid material with a high heat transfer coefficient.

    Alternatively, heat can be extracted by pumping liquid metal (sodium, tin, low-temperature eutectic alloys) in a pipework of copper (if there is chemical compatibility with copper). But handling liquid metal with a magnetic pump isn’t typically done on the DIY tech level.

    To be honest, I tried a fair number of experiments on the subject, including low-temperature Stirling motors. They’re difficult to build well. I would recommend plain old steam turbine. Steam means pressure, pressure means precautions (risk of bursting, risk of getting burned), but modern approaches to boilers try to minimize the amount of water in the system, so it couldn’t flash to steam and explode.


  • I have superficially researched both options (with the conclusion that I cannot use either, since my installation would be too small, and would suffer from severe heat loss due to an unfavourable volume-to-surface ratio - it makes sense to design thermal stores for a city or neighbourhood, not a household).

    I’d add a few notes:

    1. A thermal store using silicate sand is not limited by the melting point of the sand, but the structural strength of the materials holding the sand. You can count on stainless steel up to approximately 600 C, more if you design with reserve strength and good understanding of thermal expansion/contraction. Definitely don’t count on anything above 1000 C or forget the word “cheap”. I have read about some folks designing a super-hot thermal store, but they plan to heat graphite (self-supporting solid material) in an inert gas environment.

    2. Heat loss intensifies with higher temperatures, and the primary type of heat loss becomes radiative loss. Basically, stuff starts glowing. For example, the thermal conductivity of stone wool can be 0.04 W / mK at 10 C, and 0.18 W / mK at 600 C.

    3. Water can be kept liquid beyond 100 C. The most recent thermal stores in Finland are about 100 meters below surface, where the pressure of the liquid column allows heating water to 140 C.

    4. However, any plan of co-generation (making some electricity while extracting the stored heat) requires solid materials and high temperatures.




  • perestroika@slrpnk.netOPtoDIY@slrpnk.net*Permanently Deleted*
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    1 month ago

    It sure is possible.

    A typical “obscenely bright” LED chip might be Cree XML, but many similar chips exist. You’d need a plano-convex or equivalent Fresnel lens - shorter focal lengths favour compact design. Then you need a driver. Some are fixed while some adjustable with a tiny potentiometer. You’d need an 18650 cell holder (it can be made too, an 18650 will go into a leftover piece of 20 mm electrical cabling pipe with a spring-loaded metal cap engineered of something).

    Myself, I bought a nice head lamp, but it broke after one year. The driver board failed. Being of the lazy variety, I replaced the board with a resistor to limit current and now it’s been working 3 years already. Not at peak luminosity, the resistor wasn’t optimal of course. :)


  • I think the EU Commission has done a fairly good job of listing the pros and contras of small modular reactors:

    https://energy.ec.europa.eu/topics/nuclear-energy/small-modular-reactors/small-modular-reactors-explained_en

    They have some advantages over conventional (large) reactors in the following areas:

    • if they are serially manufactured without design chances, manufacturing is more efficient than big unique projects
    • you can choose a site with less cooling water
    • you can choose a site where a fossil-burning plant used to be (grid elements for a power plant are present) but a renewable power plant may not be feasible
    • some of them can be safer, due to a higher ratio of coolant per fuel, and a lower need for active cooling*

    Explanation: even a shut down NPP needs cooling, but bigger ones need non-trivial amounts of energy, for example the 5700 MW plant in Zaporizhya in the middle of a war zone needs about 50 MW of power just to safely stay offline, which is why people have been fairly concerned about it. For comparison, a 300 MW micro-reactor brought to its lowest possible power level might be safe without external energy, or a minimal amount of external energy (which could be supplied by an off-the-shelf diesel generator available to every rescue department).

    The overview of the Commission mentions:

    SMRs have passive (inherent) safety systems, with a simpler design, a reactor core with lower core power and larger fractions of coolant. These altogether increase significantly the time allowed for operators to react in case of incidents or accidents.

    I don’t think they will offer economical advantages over renewable power. Some amont of SMRs might however be called for to have a long-term steerable component in the power grid.



  • I noticed a journalist mention (hopefully based on good sources) that this months’s storm was estimated to be 4-5 times weaker than the 1859 storm.

    NASA, in their article mentions the recent storm as a G5 level geomagnetic storm caused by an X8.7 level solar flare.

    X is the strongest class of solar flares and G is the strongest class of geomagnetic storms, but this was definitely not a record - an X20 flare has been observed once, but as I understand, the ejected particles didn’t hit Earth.

    Where I live (latitude 59), a short electrical grid event occurred during the display of auroras. Something tripped and something immediately switched over to replace it, most people didn’t notice anything, but some had to restart various heat pumps and similar devices. Then again, in Europe, the power grid has relatively short lines and many transformers between them, which makes it comparatively less vulnerable.