{"items": [{"author": "Ryan", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954396035572", "anchor": "fb-954396035572", "service": "fb", "text": "I'm really surprised that generators don't make clean sine outputs, since they are analog devices. How interesting!
Since you have natural gas to your house, have you thought about a generator connected to the gas lines? That would eliminate fuel storage, but might be a lot more expensive", "timestamp": "1534083917"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954396035572&reply_comment_id=954399997632", "anchor": "fb-954396035572_954399997632", "service": "fb", "text": "→ I looked into natural gas, but it's more expensive than just keeping a bunch of 20lb propane tanks unless you want to run for a very long time. You need to run a pipe outdoors, which is maybe $800 of plumber time. Then either:
* Install a quick disconnect like for a natural gas grill and convert a portable generator from propane to natural gas. See price estimates on the main post, but this is $250-$500 for the generator.
* Install a big permanent natural gas generator. Much more power, but several thousand dollars minimum.", "timestamp": "1534086191"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954396035572&reply_comment_id=954416699162", "anchor": "fb-954396035572_954416699162", "service": "fb", "text": "→ As for dirty power, I also don't understand. When starting with DC you need an inverter, and simple inverters produce dirty power (modified sine), but these are single phase AC generators. (The high end generators I think are DC, powering a pure sine inverter.) Maybe it's a problem with being single phase? I know the ideal is three phase because then if all three phases are loaded equally there's constant load on the generator. So maybe with single phase the rapidly varying load combined with minimal rotational inertia (no real flywheel) gives you not quite sine output?", "timestamp": "1534088640"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954396035572&reply_comment_id=954420346852", "anchor": "fb-954396035572_954420346852", "service": "fb", "text": "→ After reading more, I'm less worried about running sensitive things off of modern AC generators. The scary warnings I was seeing look like they're about (a) poor voltage regulation in old generators and (b) modified sine inverters.", "timestamp": "1534091301"}, {"author": "Ryan", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954396035572&reply_comment_id=954443695062", "anchor": "fb-954396035572_954443695062", "service": "fb", "text": "→ Yeah, the variable load issue makes sense. Of course, then it's basically low-bandwidth frequency or amplitude modulation, which wouldn't produce the same high harmonics of a square wave.", "timestamp": "1534104675"}, {"author": "Randy", "source_link": "https://plus.google.com/102251509192760989541", "anchor": "gp-1534087590242", "service": "gp", "text": "My understanding was that there were Problems with having solar setup such that you could run things in the house off it when the grid was down (problems sourced in the utility really not wanting power outgoing from homes on the grid when it was down for utility worker safety, but turning into complex regulations that make most installers say \"Can't do that\"). Have you researched that at all? I'd really like to explore the options you describe, but only if I can actually \nuse\n them when the grid is down.", "timestamp": 1534087590}, {"author": "Scott", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954416973612", "anchor": "fb-954416973612", "service": "fb", "text": "A generator at zero load will consume fuel at about 25% of its full load consumption rate, at half load about 60%, and so on to 100% at full load. (The way to think about it is the load is transferred to the piston faces, and the governer and carburetor need to inject more fuel to push a loaded piston)", "timestamp": "1534088907"}, {"author": "Scott", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954416973612&reply_comment_id=954417567422", "anchor": "fb-954416973612_954417567422", "service": "fb", "text": "→ The advantage of gas/diesel over propane is that you can refill easily during a crisis / power outage, whereas with propane you\u2019re essentially limited to whatever you have stored", "timestamp": "1534089430"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954416973612&reply_comment_id=954424268992", "anchor": "fb-954416973612_954424268992", "service": "fb", "text": "→ Scott I don't know how much easier it is to get gas/diesel. There are propane exchange places about as nearby as gas stations.
During a real crisis I wouldn't expect either to be available, though that's also longer than I've been thinking about how to have enough power available for.", "timestamp": "1534093977"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954419663222", "anchor": "fb-954419663222", "service": "fb", "text": "Gasoline should last a very long time if you add stabilizer. And after a couple of years, you can offer it to someone for their lawn mower or snowblower, if you don't have a use for it, and buy fresh new gasoline, again adding stabilizer.", "timestamp": "1534090887"}, {"author": "Peter", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954419663222&reply_comment_id=954420316912", "anchor": "fb-954419663222_954420316912", "service": "fb", "text": "→ OTOH if you have propane you can make hot dogs.", "timestamp": "1534091287"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672", "anchor": "fb-954421434672", "service": "fb", "text": "Battery+charger+inverter+solar is amazing and I highly recommend it. Figure out your power draw, then triple it. That's your solar panel peak. Multiply your solar peak by 12 hours and that's your battery capacity. Then tell the power company to fuck right off ( or keep a small draw just for powering occasional luxuries )", "timestamp": "1534091890"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954427662192", "anchor": "fb-954421434672_954427662192", "service": "fb", "text": "→ Going fully off grid at current usage here wouldn't work. We (9 people) use about 30kWh/day (mostly electric dryer and oven) and there's nowhere on our property with all day sun, so we'd need about 55 360W-rated panels [1] to generate as much as we consume (neutral with net metering) and there's nowhere to put that many.
So, ok, we pay the one time costs to switch to a gas stove and dryer, and maybe now we use 10kWh/day, mostly fridge, freezer, lighting, and fans during the summer. Still not possible with the space we have for panels, especially since we need more panels to account for conversion loses etc.
[1] We just had a solar system spec'd that will cover 27% of our usage with 15 panels, so I'm scaling up from there.", "timestamp": "1534095729"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954427697122", "anchor": "fb-954421434672_954427697122", "service": "fb", "text": "→ Jeff Kaufman thirty kilowatt hours a day. Wow.", "timestamp": "1534095783"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954427757002", "anchor": "fb-954421434672_954427757002", "service": "fb", "text": "→ Brent that's 3kWh/person/day, or $0.65 each.", "timestamp": "1534095826"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954427941632", "anchor": "fb-954421434672_954427941632", "service": "fb", "text": "→ Jeff Kaufman right. Which is about right I guess? I'm just boggling wrapping my head around how much energy we Westerners use", "timestamp": "1534095975"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954428166182", "anchor": "fb-954421434672_954428166182", "service": "fb", "text": "→ Average per person in the US is 11kWh/day [1], though that includes people in states where you need AC.
[1] https://www.eia.gov/todayinenergy/detail.php?id=32212", "timestamp": "1534096127"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421434672&reply_comment_id=954428505502", "anchor": "fb-954421434672_954428505502", "service": "fb", "text": "→ Jeff Kaufman yup. I think in an ideal world it'd be more like 50kWh/day, but we don't have cheap safe nuclear yet.", "timestamp": "1534096186"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954421594352", "anchor": "fb-954421594352", "service": "fb", "text": "We have a solar panel + battery array that I put together out of salvage for just over $5,000 - it produces a bit over 3kW peak, which basically means 1kW sustained in all conditions.
Being in Boston, you might have a different peak-to-sustained ratio than we do (we mostly just run our system in the Nevada desert right now)", "timestamp": "1534092011"}, {"author": "Brian", "source_link": "https://plus.google.com/114156500057804356924", "anchor": "gp-1534094086659", "service": "gp", "text": "Maybe think about when power outages happen in the summer. Is it usually caused by thunderstorms?", "timestamp": 1534094086}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954432003492", "anchor": "fb-954432003492", "service": "fb", "text": "Another option is to put together a battery pack from salvaged 18650s from old laptop batteries. People seem to have fun with this, but it looks like a good way to burn the house down, so I don't want to get into it.
(People write things like \"During my first attempt I accidentally nicked a battery while removing the tab from the battery using a wire stripper and it sizzled for couple of seconds with a little smoke. Checking the voltage later shown no degrade, therefore I assumed it is ok. When I used Li-ion Charger to charge this particular battery, it caused the chargers IC to burst and thus ending the chargers life. After which I never charged that particular battery.\" [1] I can be more careful than *that* but I think this hobby is still past my risk tolerance.)
[1] https://www.instructables.com/.../Salvage-Lithium-Ion.../", "timestamp": "1534098420"}, {"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954432003492&reply_comment_id=954439698072", "anchor": "fb-954432003492_954439698072", "service": "fb", "text": "→ L O L ! ! Eh-yup, burn the house down.", "timestamp": "1534102247"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954432003492&reply_comment_id=954673499532", "anchor": "fb-954432003492_954673499532", "service": "fb", "text": "→ Example of a more reasonable project that I still don't think is a good idea: https://syonyk.blogspot.com/.../building-37v1kwh-lithium...", "timestamp": "1534255212"}, {"author": "Adam", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954458939512", "anchor": "fb-954458939512", "service": "fb", "text": "Check out the new Lion batteries designed for solar. Probably the most well known is the Tesla Powerwall, though, there are many others. Storage times can be a day or up to several days. Much less hazardous than the Pb batteries and easier to maintain.", "timestamp": "1534109310"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954458939512&reply_comment_id=954459233922", "anchor": "fb-954458939512_954459233922", "service": "fb", "text": "→ The powerwall is much more expensive than I'm thinking of (~$7k) and also bigger than I need.", "timestamp": "1534109452"}, {"author": "Brent", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954458939512&reply_comment_id=954707850692", "anchor": "fb-954458939512_954707850692", "service": "fb", "text": "→ We just used lead acid deep-cycle (marine) batteries for about $1K-$2K", "timestamp": "1534272238"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954458939512&reply_comment_id=954737990292", "anchor": "fb-954458939512_954737990292", "service": "fb", "text": "→ Lithium 16850 batteries seem to be about $0.50/watt-hour in bulk, while deep cycle agm lead acid are more like $0.16/watt-hour.", "timestamp": "1534286829"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932", "anchor": "fb-954902340932", "service": "fb", "text": "Here's what I'm currently thinking of doing:
* 100Ah AGM lead-acid battery, $170 https://smile.amazon.com/Universal.../dp/B00S1RT58C/
* 3.5A smart charger, $60 https://smile.amazon.com/NOCO-G7200.../dp/B004LWVEKS
* 300W pure sine inverter, $50 https://smile.amazon.com/Inverter.../dp/B07F15Q3C2/
* Voltage / Current meter, $20 https://smile.amazon.com/bayite-6-5-100V.../dp/B013PKYILS/
Total cost is $300 for 0.6kWh usable capacity. This would let us run our heat for 3-4 days, longer if the SPS lets us recharge.", "timestamp": "1534377509"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=954972620092", "anchor": "fb-954902340932_954972620092", "service": "fb", "text": "→ Ordered. This should be able to run our boiler or sump pump, and generally should add a lot of flexibility.", "timestamp": "1534434286"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955344734372", "anchor": "fb-954902340932_955344734372", "service": "fb", "text": "→ These arrived, I wired them up, inverter is not up to the job. The heating system drew ~240W with two of the three pumps running, and while that's below the 300W the inverter is rated for the voltage dropped and it shut off. I left a one-star review on Amazon [1] and am returning it.
[1] https://smile.amazon.com/review/R1R3P2WREUQVSO/", "timestamp": "1534630347"}, {"author": "Don", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955470632072", "anchor": "fb-954902340932_955470632072", "service": "fb", "text": "→ I don't doubt that the unit could have been not up to the task, but as you don't make any mention of your cabling... are you sure you sized that properly?", "timestamp": "1534714476"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955486649972", "anchor": "fb-954902340932_955486649972", "service": "fb", "text": "→ Don I wonder if maybe the alligator cable connectors it came with weren't able to pass enough current?
Measuring the voltage at the inverter input it was above 12v, though, and I think voltage would have fallen more if the cables couldn't pass enough current?", "timestamp": "1534720549"}, {"author": "Don", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955525092932", "anchor": "fb-954902340932_955525092932", "service": "fb", "text": "→ Jeff Kaufman Yep, if it was 12+v under load then you should have been good there.", "timestamp": "1534735059"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955540067922", "anchor": "fb-954902340932_955540067922", "service": "fb", "text": "→ The problem may have to do with the fact that your pumps are an inductive load.", "timestamp": "1534744888"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955555142712", "anchor": "fb-954902340932_955555142712", "service": "fb", "text": "→ Michael it measured 236W and 258VA, so I'd still think we'd be ok? But I'm not very clear on this.", "timestamp": "1534764372"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955559578822", "anchor": "fb-954902340932_955559578822", "service": "fb", "text": "→ Jeff Kaufman from Charles Cowie on StackExchange: \"For resistive AC loads, an inverter can work well. But for capacitive and inductive loads, inverters generally do not fare as well. The bigger the motor, the less likely it will work. An inductor (motor winding) stores current initially, acting as a load... then this energy tries to return back through the inverter. Most single-phase inverters \"see\" this and try to compensate, assuming they are not outputting the correct current and adjust themselves wildly, leading to continued overcompensation and failure.\"", "timestamp": "1534768796"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=955560656662", "anchor": "fb-954902340932_955560656662", "service": "fb", "text": "→ From some more reading, it looks like you need to derate the inverter by 50% for inductive loads, at least, possibly more depending on the design.", "timestamp": "1534769466"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=954902340932&reply_comment_id=956448711992", "anchor": "fb-954902340932_956448711992", "service": "fb", "text": "→ New inverter seems to do well: https://www.jefftk.com/p/furnace-battery-backup", "timestamp": "1535303933"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955540172712", "anchor": "fb-955540172712", "service": "fb", "text": "If you're interested, I have a couple of old APC SmartUPS's that you could probably adapt to this purpose. They're rated at 1200 VA, and have some additional features you might find useful or fun (voltage alarm, brown out protection, networkable).", "timestamp": "1534745084"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955540172712&reply_comment_id=955555172652", "anchor": "fb-955540172712_955555172652", "service": "fb", "text": "→ Do you think a UPS does a reasonable thing if you swap out it's battery for a larger one of the same type?", "timestamp": "1534764412"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955540172712&reply_comment_id=955559154672", "anchor": "fb-955540172712_955559154672", "service": "fb", "text": "→ Jeff Kaufman I don't know if that's true for all of them, but I know that this particular model can take additional batteries wired in parallel to double its capacity. I also know a couple of people who know more about them than I do, whom we could ask.", "timestamp": "1534768478"}, {"author": "David Chudzicki", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955584174532", "anchor": "fb-955584174532", "service": "fb", "text": "Have you considered stacking concrete blocks in the back yard?
https://qz.com/.../stacking-concrete-blocks-is-a.../", "timestamp": "1534778856"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955584174532&reply_comment_id=955629069562", "anchor": "fb-955584174532_955629069562", "service": "fb", "text": "→ There's something I'm missing about the problem if that design is the best solution. What's wrong with lifting a single heavy weight with adequate gearing? I guess this way everything can be built for much lighter loads because the most the crane needs to handle is one block?", "timestamp": "1534800846"}, {"author": "David", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955584174532&reply_comment_id=955842402042", "anchor": "fb-955584174532_955842402042", "service": "fb", "text": "→ \"He\u2019s developed a machine that can mix substances that cities often pay to get rid off, such as gravel or building waste, along with cement to create low-cost concrete blocks.\"
Jeff, maybe those blocks aren't strong enough to be made much larger without falling apart?", "timestamp": "1534938475"}, {"author": "Scott", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955584174532&reply_comment_id=955860400972", "anchor": "fb-955584174532_955860400972", "service": "fb", "text": "→ Jeff Kaufman concrete has great compressive strength but not so great tensile strength, lifting it piece by piece takes advantage of this", "timestamp": "1534950897"}, {"author": "Peter", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955584174532&reply_comment_id=956455493402", "anchor": "fb-955584174532_956455493402", "service": "fb", "text": "→ His design only makes sense if it's cheaper than the alternatives. Gear trains, heavier cables, etc. would make it more expensive. As it is it's only marginally better than battery storage.", "timestamp": "1535307147"}, {"author": "Laura", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=955930864762", "anchor": "fb-955930864762", "service": "fb", "text": "I'd be sad to miss my computer because I earn my living via the Internet.", "timestamp": "1534990511"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/954384847992?comment_id=959032294472", "anchor": "fb-959032294472", "service": "fb", "text": "Jeff, we have an example up in the Merrimack Valley right now, about how the expensive solution is not always the best solution. Those who have the gold standard in electric service backup, those who have natural gas powered generators, are simply outa luck. Their electric service will be restored long before Columbia Gas gets around to returning gas service to the Valley.", "timestamp": "1536932470"}]}