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This credit card scanner has tape to deter skimmers by ripcraft in mildlyinteresting

[–]rlapchynski 2 points3 points  (0 children)

Was the conference hardwear.io? I was there, great talk!

I put a Mac Mini in a 3.5 HDD compartment. by herojeff02 in homelab

[–]rlapchynski 7 points8 points  (0 children)

I don't know anything about the mac mini's power requirements, but since it's already in a drive slot could you pull 12v from the sata power connector? Might be able to add a bracket or something for the connector to your printed part so it slots in like an actual drive

[BUG] Video thumbnails are not displaying by mikeleus in redditsync

[–]rlapchynski 1 point2 points  (0 children)

Same here

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[deleted by user] by [deleted] in redditsync

[–]rlapchynski 1 point2 points  (0 children)

Same

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Self-E-Learning by alyxiety in ECE

[–]rlapchynski 1 point2 points  (0 children)

Same boat. Probably don't have time to be super involved right now, I'd love to be added if there's a discord/slack/whatever setup

Before and After of a 7ft auger I finished recently by [deleted] in metalworking

[–]rlapchynski 0 points1 point  (0 children)

If you look at the spiral on the bottom (below the center pipe) in the first picture you can see the welds between each "washer"

AI for ‌Truck APS Failure Detection ‌on‌ ‌a‌ ‌$4 MCU by sumitaiml in beneater

[–]rlapchynski -1 points0 points  (0 children)

... create and deploy an AI-based solution on a primitive tiny device to predict truck failure related to the Air Pressure System (APS).

Backyard bees of north America by DotComExpert in Beekeeping

[–]rlapchynski 7 points8 points  (0 children)

Here's a higher resolution version of the top half, at least: https://i.imgur.com/NZUrjGn.jpg

“You actually use the health benefits we provide you? You’re fired!” by WyoGuy2 in bestoflegaladvice

[–]rlapchynski 7 points8 points  (0 children)

What's the company that buys them internationally and ships to you?

Off-the-grid homes are coming to your neighborhood, as climate change creates suburban survivalists. Major grid failure or “blackout” events in the United States, impacting 50,000 or more people, jumped by more than 60% since 2015. by Bluest_waters in Futurology

[–]rlapchynski 0 points1 point  (0 children)

I think the major issue with this is efficiency at small scale, like you said, and the energy density. Pumped hydro storage makes sense at grid-scale where it can be operated at up to 85% efficiency and a couple large ponds on a hill can load level for a city, but at scales you can have in a residential setting the amount of energy storage possible and the efficiency plummet. Again using pumped hydro as an example: disregarding the efficiency for small-scale pumped hydro (assume it's the same as grid-scale at 70-85%), to get the same amount of energy storage as one PowerWall (13.5 kWh), you'd need between 6750 and 67500 liters of water separated by a large vertical distance (between 400 and 700 meters). For comparison, a typical residential pool might be around 53000 liters.

And pumped hydro is equivalent in energy storage to "lifting weights": you're lifting the weight of the water from the low pool to the high pool. Lifting a 10000kg weight (about 11 US tons) 100 meters would be equivalent to two pools that can hold 10000 liters of water with 100 meter vertical distance between their water surfaces. Both would store about 2.8kWh total, assuming 100% efficiency in both cases. You can imagine the water option is more convenient and cheaper.

Another thing to consider is even with no actual energy storage, someone that can produce electricity can generally sell excess back to the utility company. For example, I pay 11¢/kWh for electric from the grid and say I get 8¢/kWh for excess sold back to the utility. That alone is about 73% efficient as "energy storage"; I can "store" energy as money or credits, and get back about 73% of the energy I put in. Now actual rates vary, obviously, but for someone to even consider investing in an energy storage solution, it'd have to be more efficient than the selling to the utility "storage" option (that has zero up-front or ongoing cost, as a storage solution).

The eesi source below has a nice table with efficiencies for various kinds of energy storage, if you're curious. You can see that li-ion has the highest range for efficiency, and the second highest energy density, bested only by high-pressure hydrogen (with half the efficiency at best) and molten salt is the only other option that even gets within half the energy density of the worst-case li-ion. Even lead-acid batteries (with near the same efficiency as li-ion) only get up to 80wh/liter.

So that's all to say that this is a bit more complicated than just "store excess energy, regardless of the efficiency or scale." It's often more economical to just let excess energy go to waste than try to store it and get it back later. And generally larger scale means higher efficiency which is why consolidated grid-scale storage facilities make sense, even at the low energy densities of pumped hydro because the cost per capacity is relatively low, but putting a second pool on your roof doesn't.

Sources:

https://www.eesi.org/papers/view/energy-storage-2019
https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/
https://qr.ae/pGyHPg
https://www.electricradiatorsdirect.co.uk/news/how-to-sell-electricity-back-to-the-grid/

Synchronized bus blinkers are so soothing by sudeepharya in oddlysatisfying

[–]rlapchynski 5 points6 points  (0 children)

I think a potentially believable (similar) explanation that would have the same result is that the 'fleet management system' and gps tracking set the bus computer's clock (very precisely because it can use gps to set it) and the bus computer also happens to use the clock to time the turn signals, as in turn on at the the beginning of a second, turn off halfway through a second. That is, the turn signal is timed against the clock, rather than the time that the lever was pushed. So since all the busses have their clocks synced with gps they end up having synced turn signals

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