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.
You need to take into account efficiencies of getting the cold into the fridge too. It takes around 10-15 hours of runtime to cool the thermal mass down from 5 to 0.5 degrees C (at 14C exterior temp), and the fridge needs 120 watts to run. Measured this way, the thermal battery is storing ~1200-1800 watt-hours.
But then, if it were powered from batteries, there would be significantly more power needed to fully charge the batteries and maintain good health -- my 860AH battery bank (4 deep cycle batteries) needs at least 1kwh input to charge up from 12v to full).
Another way to come at the question is, how many batteries are typically specced out to power an offgrid fridge, and banks costing 10-20k dollars are not at all uncommon, though they're also shared with other household needs.
I was subletting for a year from a family of six (who were away themselves). Their fridge was extremely oversized for the amount of stuff I stored in it, so I filled up two thirds of the volume with refilled water bottles.
It has the added benefit of stabilizing the temperature a lot. I recall reading somewhere (who knows, maybe one of the earlier blog entries here) that turning on a cooling element costs a lot of energy too on top of it just running, to the point where that effect on energy savings should not be underestimated.
All in all I saved quite a bit on my energy bill with quite a simple hack.
A material that can be frozen would be better, because it takes a lot of extra heat to melt a frozen material and so more cold could be stored.
However, this needs a material that freezes at a higher temperature than water, and most such are oils, which are less dense and so store less cold overall.
I've heard about projects where they store heat underground - not sure if they use a certain medium or groundwater or something, but they basically pump heat into the ground during summer (and cold out into the HVAC) and vice-versa in winter. I guess ground itself - whatever is down there - is good enough. See also the London underground for an undesired underground heat storage.
But yeah, back in the day they would get blocks of ice from nearby lakes and put them underground, it'd last all year.
Some of the things I found crazy when reading about it is that they can get the ground temperature up to 80 degrees celsius by the end of the summer, and then the ground stores enough heat (without just dissipating off to the environment) that it can provide a majority of the heating for 52 houses over the course of a cold Alberta winter.
He says they didn't quote him the yearly price. All you have to do is go through the beginning of their trial signup process to see that they clearly disclose it in a completely open and visible way.
Yes, but aluminium smelting has certain constraints - namely, the molten metal cannot solidify[1]. This restricts your ability to quickly spin up and down smelters, but they are still potentially a very useful part of an energy smoothing strategy.
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?
Your assumption is correct. The vast majority of the damage comes from thermal stressing of the refractory materials that make up the crucible of the furnace. If there were better insulators available, so that the rate of heat loss through the furnace was minimized, it would be a huge improvement to the industry, both in energy saved during production, and greater amounts of time available after shutdown before thermal effects wreck the furnace.
NAT has not solved the IP address problem, it has merely postponed it slightly. Multi-level NATs are a hell far beyond the single-level NATs that most consumers see (and single-level NATs already cause all sorts of problems for even moderately advanced network usage). So most people only have single-level NATs, which practically only extends the address space by a small multiple - 8 bits at most, in practice ~2-3 bits.
128 bits allows routing tables to be super small and fast. While RAM has gotten cheaper, it is still slow, and smaller routing tables are way more important than smaller addresses.
However, I agree with your central point - IPv4 was "good enough" that IPv6 is going to be a tougher battle than it ought to be. However, IPv6 is winning that battle already. 15% of google's users use IPv6, and it's increasing sigmoidally. [1]
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.
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.
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.
Out of reach for your local dentist? Huh? Dentists make more than most people here, $159k/yr average[1]. Software developers make a little over half that on average, depending on which sub occupation they work in. [2].
Dentists already have a mortgage sized student loan payment to make.
People also confuse revenue with profit. My coworker's OB/GYN has great revenue, but her insurance costs are amazing, almost as much as my salary.
From memory of my kids birth the hospital direct bills expensive equipment, certainly my buddies wife did not personally fund the construction of the birthing center room, however if my dentist wants a new x-ray or new chair AFAIK its literally cash out of his checking account.
Its comparing apples and oranges. Much like comparing U3 employment stats in an employee culture like the USA where as in Japan I understand they hire once a year for new grads and if you don't make it into a real job at a real company (and very many don't) its a lifetime of either NEET or temp work, so their concept of U3 means very little compared to our concept of U3. Their concept of U3 is kind of like our concept of U3 of military service academy recent officer graduates.
* 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 :/
Wifi works perfectly, suspend/resume, docking/undocking too.
As for battery life, it was around 19W/h when I first switched to linux after FreeBSD. After installing tld and powertop it is stable around 10.8-12W with wifi enabled.
Maybe you might want to try a recent distro, I'm using Fedora and I really like it.
Even my 3G usb dongle worked flawlessly with zero config.
PS: I remember having a flaky wifi under Debian 8, but that was due to an old version of wifi driver. It has since long been fixed in every distro I tried -including Debian-.
PS 2: My laptop is pretty old (x201), so your mileage may vary. You might want to check out thinkwikis for further info.
Partly, that's because the x201 is so old. It's had about 7 years to mature support.
I had an x201 new, and I ran into all those problems listed above for the first two years. Hell, I had to use a USB WIFI dongle for the first year or so because the drivers hadn't stablized.
Yeah, I'm so tired of hearing this come up when people are looking for Linux laptops. It's very old, and VERY ugly. Most of us want something modern that runs Linux well.
I can only speak about myself of course but running Ubuntu 16.04 on a thinkpad x250 I have absolutely none of the issues you have listed above. Maybe you hear more about people having bad experiences than good ones?
I remember having these issues on an x60 series maybe 8 years ago, but my friends who have thinkpads are all running them fine, even on the jankiest distros with a bit of careful driver picking
Owner of a Thinkpad X1 3rd gen running Debian (started with Jessie, now Stretch), and my experience is quite different but there are some things to know. Let's trade anecdotes:
> - Wifi is flaky (ier than on windows)
No problem there, always been rock solid. The chipset is likely to matter, my laptop uses an Intel chipset. Performance wise Intel may not be the best, but the Linux support has always been good in my experience.
> - Battery life is shit (ier than on windows)
A very common misunderstanding, and very easy to solve. The thing is, a stock Linux distro is made independently of the PC hardware that will run it. There's no integration like any PC vendor does when installing Windows, making sure the Windows configuration is well tuned. In order to be functional on most devices, a Linux distro is typically conservative, and will typically stay away from enabling low-power modes that are flaky on some crappy PC models.
But for most tier 1 PC brands, the hardware is fine and it's perfectly safe to enable aggressive low-power. So just install a package like The Laptop Project (tlp), or the older laptop-mode, and you're good to go. You can even tune the configuration, it's simple and well commented. For example, with a fast SSD (no spin up/down), one can be very aggressive on putting the drive into low-power.
With this done, taking about 10 mn tops, I have a longer battery life on Linux as on the stock Windows8.1. And this is as reported by the firmware through ACPI, so same estimator on both sides.
> [Various sleep mode issues]
There was a very nasty bug in Linux MMU set-up that's been solved in 4.8. Before this, it could trigger some random and sometimes hard to reproduce bugs on some models, leading to crashes on resume. I've been affected, and it was a pain. The bug was there for a long time apparently.
Since 4.8, it's been rock solid. Zero issues. And it's really night and day in term of user experience. In case some of your issues were related, you may want to make sure you're running a recent enough kernel.
As for the unwanted wake-ups in a bag turned into an oven? Only ever happened to me on my work TP running Win7. From experience, sleep is not perfect there too.
No experience on using an external monitor with my Linux laptop.
One of the main weakness is that there's no ODM integration if you install Linux yourself. With big brands like TP, it's still mostly been smooth in my experience, except for the nasty resume bug fixed in 4.8. If that's a problem for you, there are now vendors with pre-installed Linux. Then it's a similar situation to Windows.
> The thing is, a stock Linux distro is made independently of the PC hardware that will run it. There's no integration like any PC vendor does when installing Windows, making sure the Windows configuration is well tuned.
You make it sound like Windows needs to be fine-tuned (by the vendor) to provide good battery life. This is absolutely not the case. You install a bare Windows 10 on a random laptop, and battery performance will likely be much better than on Linux.
Anecdata, but my desktop Lenovo workstation's suspend function worked well with Linux, but after an update (few months ago) it never resumes successfully. Nothing in logs -- just simply doesn't wake up properly. (4.10 kernel.) These are painful things.
> Anecdata, but my desktop Lenovo workstation's suspend function worked well with Linux, but after an update (few months ago) it never resumes successfully. Nothing in logs -- just simply doesn't wake up properly. (4.10 kernel.) These are painful things.
That sounds like my experience with Windows 10 on my gaming PC. I only use that machine when gaming, and while it has a <10 second cold boot time (god I love NVMe), I prefer to leave it running and let it fall asleep after a few minutes of inactivity. Some time last week or so, I noticed it never cycles fully to sleep; it will fall asleep and almost immediately wake up. I'm positive this was due to a Windows update, as I haven't changed any settings on it before or after the incident first occurred.
Now, this is on a PC I built, but I used a common motherboard (Gigabyte Z170M) and never had this issue on my previous build, also based on a Gigabyte Z series board. My wife's computer is a mini-PC made by HP, and it started having the same sleep/wake issues during the same week. Something in a recent Windows update has affected sleep states.
I had similar, terrible issues with my gaming rig when I let Windows auto-update from 7 to 10. I found that there is an option in system update to "restore" or "auto-fix" the OS. You might start by trying that.
I found that I needed to let the entire thing be wiped (including all software) and re-installed in order to get it working. A long time and complete pain in the ass, but it's much better now.
Just as a piece of warning if you go that route: MS decided that my legit MS office keys were "Pirated" because they were old and wanted me to upgrade (after telling me that it was a valid key 3 hours before) so I told them to pound sand and I was going to buy MAC's from now on, and I'm not a fan of Apple at all. They offered me nothing, but the chance to give them more money.
> Just as a piece of warning if you go that route: MS decided that my legit MS office keys were "Pirated" because they were old and wanted me to upgrade (after telling me that it was a valid key 3 hours before)
This happened to me after my first upgrade to Windows 10. I had a legit copy of Office 2010, and when I upgraded my Windows 7 installation to Windows 10 during the free year, I opted to do a clean OS install after 10 was activated. Upon reinstalling Office and inputting my key, at first it activated then it threw my Office install into an unactivated state and told me to contact my administrator. Umm, what? I'm the administrator and this was a retail purchased and licensed copy that worked fine before being installed on Windows 10. I even tried reverting to Windows 7 and installing Office on that, but it never activated and gave me the same message.
Thankfully I don't really rely on Office anymore and can get by with F/OSS alternatives or Office Online, but it definitely sucks that Microsoft appears to try pushing its business customers into O365 subscriptions and away from traditionally licensed software using what I feel should be illegal tactics.
Completely agree with you. I have in writing that my key would be good, even though the MS site said that there was an error and I needed to check with Customer Service. I then explained this to three people, whom found the written statement and said they couldn't/refused to fix the problem. They just wanted to sell my an O365 subscription.
As to how legal their tactics are, I'm not sure. I do know before I would never have considered anything other than MS, I'm now left to moving onto Mac's because I cannot give them more money and the work I do tends to now work in the Linux or alternative OS environments. Lots of industrial software that is touchy enough as it is...
I only boot into Windows once a month or so. This Monday, when I had my laptop sitting idle for a bit, I noticed the sound of the hard drive settling down and spinning up again in a regular pattern. At the time, I thought it was the Antivirus deciding to do an idle scan just when the OS put the drive to sleep, but now I think I might be affected by the same bug you mention.
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