Recent submissions

Comment · 7 years ago
Thermal masses are a super cool way (ha!) to store energy, and I'm surprised they don't get more attention, both in the media, and in terms of research / investment. Heating and cooling accounts for somewhere around half(!) of residential energy use [1], which could be easily time-shifted with some very cheap thermal mass and some economic incentive to do so.

This is actually used in some commercial buildings in places where energy is cheaper at certain times of the day (for example, at night) [2], by freezing ice when energy is cheap, and thawing it when it isn't.

That being said, although this is a super cool project (I have the same inverter, and I made a similar control board ;)), this thermal mass doesn't seem like it would be particularly practical in most cases. Water has a relatively high specific heat capacity of 4.186J/gC, but given the narrow range of temperatures acceptable for a fridge, this doesn't end up being very much - only 79Wh per degree Celsius that the fridge is allowed to swing. If you consider 1C - 6C "acceptable", you only end up storing 395Wh. This is about 30-40% of the capacity of a $100-$200 "deep discharge" lead-acid battery, and is also a much wider range than most consumers would be used to (and may result in frozen veggies, for example).

In order to make this more practical, you really want something that can freeze around fridge temperature. For the same amount of water used above, freezing and thawing the water would store 6,308Wh(!), around 16x as much. If you could get something that freezes at 3C/4C with a similar heat of fusion to water, you could have a much smaller thermal battery that lasts _much_ longer, without the substantial temperature swings you see with your current design.

[1] https://www.eia.gov/tools/faqs/faq.php?id=96&t=3 [2] https://en.wikipedia.org/wiki/Ice_storage_air_conditioning

Comment · 8 years ago
the shady part was that they charged him for a full year after he forgot to cancel, despite quoting the price on a monthly basis when he signed up.

(Also, "free" auto-renew trials like this without refunds are by themselves shady imo)

Comment · 9 years ago
Huh, interesting. I read the whole thing and understood at least half of it ;).

Are the damages primarily thermal? I couldn't figure it out from that report, although it seemed to somewhat hint that they were. I.e. if you could keep the cells warm (with more insulation or otherwise), would they still get damaged by the shutdown?

Comment · 9 years ago
Comment · 9 years ago
Comment · 9 years ago
This is at best a tangential point. If the wind farm is 114MW with a 10% capacity factor, his point is still correct.

Yes, they still rely on coal and natural gas to smooth the load, but his point was that by subsidizing the wind power, they still reduce emissions the same amount as if they didn't.

Obviously, this strategy only works when renewable penetration is fairly low, once you start having oversupplies then you no longer have 100% efficiency with this strategy.

Comment · 9 years ago
Example: https://github.com/urbit/urbit/blob/master/noun/vortex.c#L23...

I can confirm this is roughly what the intentional source code looked like.

Personally I found it a huge pain and an unnecessary difficulty, but opinions differed :). The bigger problem was a lot of the code was crap (yay research code!). The lack of english names only made this more difficult because it removed valuable clues as to what the intention of the author might have been.

Comment · 9 years ago
NO. Do not buy factorio. You will lose sleep. You will lose your job. You will sell your children just for a few more speed modules.

The first time I played factorio I played for 24 hours straight, and I am not normally someone who finds games any fun at all.

But seriously, Factorio is a great game. A game I imagine myself still playing 10 years from now.

Comment · 9 years ago
Where are you getting $15,000 for the powerwall? It's $5,500 for 13.5kWh, which should be enough for nighttime loads in many houses (but may require some inconveniences, like not running the dryer at night).

You are right that it does not yet work out, it's $0.17/kWh for the powerwall (assuming you fully charge/discharge it each night) + cost for panels. Given that grid-disconnected users would want some buffer, an off-grid system probably works out to ~$0.40/kWh all in for battery-stored electricity

You could save a big chunk of this by some habit changes, most of the cost comes from the batteries, so scheduling energy intensive activities to run during the day reduces your cost for them to $0.10/kWh or so.

Honestly I am surprised how close these numbers are. I initially was sure the grid would survive in cities, but now I am not so sure. In 10 years these numbers will likely be half what they are now (batteries in particular will be way cheaper). It might all be enough to kill the grid in many places.

Comment · 9 years ago
Comment · 9 years ago
VGA is still the most common connector type I see on projectors and in conference rooms. It's being slowly replaced by HDMI, they might be about even now.

Ethernet is still the premier PHY layer for people who want their shit to work. Wifi is still flaky as crap these days in many places. Thus, there is no Ethernet replacement yet.

As chriswarbo says, the age of the tech is completely irrelevant. Instead, it's the utility / cost tradeoff that matters. A floppy drive would be expensive in terms of weight/size, and would be useful to approximately 100 people (10 if it's 5"). VGA and Ethernet adaptors would be useful to probably 1/2 to 1/4 of the users, and cost almost nothing to have.

Also, VGA specifically is one of those ports that's still really nice to have, just in case. Last thing you want is to show up at a conference room and not be able to plug in your laptop.

Comment · 9 years ago
You can do both. My point is that most of the ports and features they removed really cost nothing in terms of weight, and so aren't really engineering tradeoffs in a sense, but rather design tradeoffs (i.e. thinner). In the feature/weight space, they are not even close to the pareto optimum.

Personally I find wireless anything to be a persistent pain and not worth the trouble, but since it costs almost nothing to add, I'm totally cool with adding it. Maybe in 10 years it won't suck.

Comment · 9 years ago
By perfectly fine, do you mean:

- Wifi is flaky (ier than on windows)

- Battery life is shit (ier than on windows)

- Sleep mode has one of the following problems

* Does not properly suspend (i.e. wakes up immediately when suspending, shuts down instead of suspending)

* Does not properly resume (i.e. kernel crash on resume)

* Sometimes does not properly resume (even more annoying to debug)

* Resumes randomly, when you don't want, often turning your backpack into a forge.

- Hibernate mode doesn't work (at all, your hardware has been blacklisted).

- Plugging in an external monitor occasionally causes everything to crash (but sometimes just compiz).

These are the most annoying problems I have on my Linux laptop. Admittedly, mine is not Thinkpad, but looking at reviews on the latest Thinkpad, at least the battery life issue seems to be ever present. These are pretty much the same problems I've had for the 10 or so years I've been running Linux on laptops. I would have thought they'd been fixed by now. 10 years ago, Windows had a bunch of these problems too, so it was excusable. Now, it's just embarrassing.

I still run Linux on my laptop because I like the dev environment and tools so very very much, but I would pay serious money for hardware that was guaranteed to just work (tm) with Linux, with all of the above solved by the vendor rather than by me. I used to enjoy these little problems, but now they just annoy.

The sleep mode problems are the most annoying to me, the most elusive to solve, and the most impossible to predict from reviews :/

Comment · 9 years ago
Fallacy of the excluded middle. They can do something more than Apple (i.e. not just USB-C ports), but less than others. The Apple design doesn't end up being small or light, because to actually use it you need a plethora of connectors.

At a minimum, I would expect standard USB, headphone, sd card reader, standard HDMI, mini displayport.

You're going to have a hard time convincing me that an HDMI connector adds more than a few grams of weight. Thickness, maybe. But even then.

VGA and ethernet could be nice too, but wouldn't see much use in my case.

The battery could be removable (i.e. half internal half external, like the thinkpads).

Optical drive is obviously not much use in a laptop anymore and should be external. (this one actually adds weight and not just thickness)

Comment · 9 years ago

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