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Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
- olegkikin 9y agoIt better be attached well. If there's a windy day, and that thing flies off and kills someone, you will not only be liable, you will have to live for the rest of your life with it.
- nikodunk 9y agoVery true. I've tested this thoroughly and it won't. Obviously there's always a residual risk, which I've mitigated by moving the panel to a window further back on the roof. Then I'm going to see if the panel's moved after a year. Another solution would be outdoor glue, but that messes with the ephemeral nature of the project. Thanks for the input!!
- WheelsAtLarge 9y agoNice hack. Can it power a fan for a night? That might save you some money in cooling, which would help with payback. I won't be using it for my apartment but it has great potential for an off the grid light power use workshop. Good job, thanks for showing. Just a note, the biggest expense these days in solar power installations, home, is the manpower and incidentals needed to install it. Reduce that and solar power replacement begins to look good. As we saw here, where there were no installation costs.
- nikodunk 9y agoHey! It can power a fan overnight no problem. A large box fan uses around 45W, so this could run it for 10hours on a day's charge. Good point! To your point of expense – the installation cost is what bummed me out, too. That's exactly why the hack is so effective if someone in your family can self-install it! I agree. Similar to an AC unit or a satellite dish that most people just install themselves...
- c8g 9y agowe have a table fan specially made for solar is 11.5W, costs about $14.7
- jaclaz 9y agoJFYI, the back of the envelope calculation is about energy "created", this assumes that you actually consume it, i.e. that on average you would use that energy (while it is within the battery capacity range), if you leave for - say - 1 month, it is 1/12 less.
- nikodunk 9y agoGood point! I think the next step in this project would be to hook it to some device with high constant consumption, like the fridge, to make sure the energy gets used up every day. Currently I find it difficult to use everything it's making, as you say. It's like having more tomatoes in your garden than you can eat -> sell the tomatoes.
- ruffrey 9y agoHow safe is it to keep that battery indoors? Don't batteries need some ventilation?
- canoebuilder 9y agoIt's a sealed lead acid(SLA) battery which is different from a wet/flooded battery, which do require periodic topping off with water and ventilation. For a project like this, SLA is the way to go. https://electronics.stackexchange.com/questions/175649/are-sealed-lead-acid-batteries-safe-to-use-indoors https://electronics.stackexchange.com/questions/175649/are-s...
- deleted 9y ago[deleted]
- nikodunk 9y agoAs canoebuilder said. I initially thought the same thing :). Believe me I googled the shit out of this so as not to drown the house in hydrogen.
- galdosdi 9y agoCool! The one thing I notice the author gets wrong is (out of modesty perhaps) claiming the system isn't very financially successful. But it actually is! > 200W system payback period: $300 / $48 = 6.5 years until payback > Either way you cut it, this is not a money saving machine. Energy prices are just too low. That represents like a 16% rate of return with little risk, which any investor would take in a second. However, the $66 battery expires after about 8 years, you're saving more like $40, not $48, to amortize the cost of replacing the battery every 8 years. So the actual rate of return is more like 13%, which is still very attractive. You'll never find any investment/savings product that returns half that well at such a low risk and is so accessible to anyone with $300. We've hit the point where solar is very economical! It's exciting!
- nikodunk 9y agoWow that's a really good point.
- cr0sh 9y agoYou can also get cheaper batteries and larger panels off Craigslist for much less. You can easily find much larger panels for around $100.00 - same kind you see on roofs. Batteries are more difficult to find cheap, but 6 volt golf cart batteries are readily available and low cost. Sometimes you can also find the 12V 35 AH wheelchair batteries (same as what the author used) cheaply too. Point being, if you look around, solar electric generation at a small scale can be done even cheaper than purchasing off Amazon for some of the components (inverters and charge controllers are mostly exempt - unless you go to a hamfest).
- nikodunk 9y agoVery good point! Hadn't thought of second-hand components. That'd help with the environmental footprint, too!
- pilom 9y agoUnfortunately it isn't a 16% return because he can't sell that system for what he paid. If you buy a stock at $300 and sell it for $348, that's a 16% return. But for him, he probably would have trouble selling all of that for $100 (the battery will be worthless in about 2 years given how far it is being discharged and very few people buy these things on craigslist for anywhere near what they cost). If he can sell it in 6.5 for $100 he has now made $400 in 6.5 years, a 4.5% annual return.
- mchannon 9y agoFar more cost-effective would have been to skip the battery and just put a cheap chinese pure-sine-wave grid-tie inverter to bridge between the wall outlet and the panel. It's simple- it has a 110V line cord and plugs into the outlet, sending current the opposite way of normal. Do a search on your favorite e-commerce site for "grid tie inverter" and you'll see what I mean. These cheap inverters have most of the same safeties as the UL 1703 certified variety, and as long as you don't exceed current ratings (not likely with a little 200W panel) you're able to apply the power to your electric bill, without futzing with a lead-acid battery.
- nikodunk 9y agoWow that's really great input. I'm going to check this out and write a follow-up! This would allow me to credit the power directly to my fridge bill, as opposed to just using it for lighting and devices!
- toomuchtodo 9y agoDo not do this. You could kill a utility worker, and it's against the law for safety reasons. Edit: Net metering/grid tie guidelines require inverters that will shutdown upon loss of utility power. Also, a disconnect switch must be on the exterior of the building/facility, clearly identified, and on record with the utility. Bonus points if you Google "lock out tag out".
- cmac2992 9y agoDoes that work with a regular meter? My internet sluething says some people have been charged for the electricity the produce because they don't have a "compatible" meter.
- ldiracdelta 9y agoIf you hook up a ton of these and actually generate _more_ than you consume at any time, you will actually _pay_ the power company for the power you push back into the grid. You have to get a special meter that can measure the direction of the flow. I have bought two residential roof-mounted solar systems and this is what they told me. If you never generate more than you use, maybe you're ok.
- snowwindwaves 9y agoI find the title kind of click baity, "$200 solar self sufficiency for my bedroom" would be more accurate
- nikodunk 9y agoHey. You're completely right :) My original title was was "Solar Self-Sufficiency for Renters", but my mates in marketing told me to clickbait it the f up. Would you have clicked on the former, though?
- TeMPOraL 9y agoPersonally, I would. What you wrote is very interesting, and interesting content can stand for itself. No need to clickbait things up.
- user5994461 9y agoYour friend gave you good advice.
- snowwindwaves 9y agoit adds to the misinformation regarding solar energy and going off-grid
- Kliment 9y agoYour "mates" can f right off. It debases an otherwise very interesting article. If you're interested, here is another similar setup that went entirely DC http://www.lowtechmagazine.com/2016/05/how-to-go-off-grid-in-your-apartment.html http://www.lowtechmagazine.com/2016/05/how-to-go-off-grid-in...
- Cerium 9y agoThe last place I worked we did this (though with some permission). One of the guys made friends with some people at a thin film solar plant down the street. He got a bundle of manufacturing rejects (300w panels that only made 280) for free. We strung them up on the roof and were raking in the kWh. Enough to charge 3 electric vehicles without paying the power company.
- jpk 9y agoThis makes me wonder why the panel manufacturer doesn't bin panels like they do with CPUs? Surely they could sell them for less than the 300W panels, but more than zero?
- pilom 9y agoMost do. The panels you see on rooftops are all generally exactly the same size but could generate anywhere from 315w/panel to 250w/panel depending on binning. No idea why that company didn't.
- ldiracdelta 9y agoWhen I was shopping Itek panels, I got a prices for 270W, 280W, 290W, and 300W. I suspect most companies do binning.
- pilom 9y ago> Unless you live on an RV or a boat it doesn’t make financial sense yet If you're curious about what a system for an RV does look like, I work remotely full time in an RV and built my own system: https://therecklesschoice.com/2016/04/29/diy-rv-solar/ https://therecklesschoice.com/2016/04/29/diy-rv-solar/ 6.5 times the solar, 15 times the storage, 20 times the inverter (but mine is overkill for us honestly).
- rbritton 9y agoAre you stationary or do you move around? Four batteries + solar panels can get somewhat heavy and eat into your total capacity, so I'm curious if it's an issue.
- pilom 9y agoWe are very mobile, usually stay in one place for a week at a time and then move a couple hours away. You're right about weight though, we are right at our GVWR (11,000 pounds) when fully loaded. The batteries weigh 100 pounds each and the panels are another 15 pounds or so each. That said though, we get terrible gas mileage already so the extra 500 pounds for everything doesn't change it much.
- deleted 9y ago[deleted]
- megablast 9y agoAnd cost? > We installed a fairly large (for an RV) completely custom solar power system all by ourselves for right around $3000. Sorry, saw that. 15x the cost.
- ChuckMcM 9y agoFun stuff. I've built several systems just like this one for camping, they let you keep things like iPads or laptops charged and they aren't noisy like running a generator. Something that my wife discovered was that an igloo "lunchmate" cooler was perfect to hold the battery and charge controller. Makes it easy to carry. I recommend using Anderson Powerpole connectors (https://powerwerx.com/anderson-power-powerpole-sb-connectors https://powerwerx.com/anderson-power-powerpole-sb-connectors) to make it easy to set up and tear down. I typically use one pair of colors for the connections to the battery, and another pair of colors for the panel to charge controller.
- nikodunk 9y agoDamn, that's some inside advice. Let me try it out and I'll post a follow-up! Thanks so much!!
- dba7dba 9y agoDuring Iraq/Afg conflict, US army started investing in solar systems because they realized every fuel (alot used for generators) convoy that doesn't have to make runs to outposts means less exposure to attacks by enemy. Solar systems can help lower fuel consumption for generators. I heard fairly high percentage of US veterans back at home are more interested in solar systems because they saw the high cost of moving fuel around. Ironic. We supposedly went there to secure our energy source and we learned solar system is a viable solution...
- kerbalspacepro 9y agoI think an argument could be made that, going there to secure our energy sources forced us to LEARN how to make a better, viable option.
- liyanage 9y ago+1 on the Powerpole connectors, I used them on a small solar system very similar to what's described in the article and they work great.
- grecy 9y agoI built a very similar system into my Jeep-house. I have two 100W panels on the pop-top roof, a charge controller and a dedicated solar battery (isolated from the engine-starting battery) that runs my fridge, water pump, UV treatment lamp, interior lights, air compressor and charges all my electronics (laptop, kindle, cameras, etc.) directly from 12V DC. I can leave the Jeep parked without running the engine for days and easily have enough energy to meet my needs. The system has been amazing, and it's fantastic to be electricity self-sufficient in remote West Africa, where grid power is often non-existent More details and photos here: http://theroadchoseme.com/jeep-build-complete http://theroadchoseme.com/jeep-build-complete
- AnimalMuppet 9y agoA question: How much did the solar aspects of your rig cost? And a comment: You might want the ability to tap your solar battery to start the Jeep, if you're going to leave it parked that long.
- mod 9y agoWouldn't tapping the other battery be a simple matter of a pair of jumper cables? I mean, I guess it'd be nice to have wired in, but I can't imagine the time-savings would ever catch up to the initial amount of work.
- AnimalMuppet 9y agoDepends on how close the two batteries are to each other. I mean, I guess you could physically remove the solar battery, and hand-carry it to the ground just in front of the engine compartment, but now the hassle factor is getting rather high...
- Washuu 9y agoOn TJ and older Wrangler the tray on the opposite side battery tray is empty. People will run dual battery setups that way. There are even options for all Wrangler models to put dual batteries in the stock location. $100 to $200 on a TJ Wrangler. The cost and amount of work to do it is minimal.
- sand500 9y agoIf we are talking about being green, what is the carbon footprint of manufacturing all those things vs the equivilent carbon to geberate thr electricity the solar panels provide?
- seveneightn9ne 9y agoThat's at the bottom of the article: Production footprint PV multicristalline: 4200kWhee/kW [1] * 0.1kW = 420kWh embodied energy Production footprint lead-acid battery: 321kWhee/kWh [1] * 0.5kWh = 161kWh embodied energy Total Footprint: 581kWh Annual energy production system: 155kWh/y Payback period: 581kWh / 155kWh/y = 4+ year footprint payback
- SingletonIface 9y ago> I wish I could run a water heater, heating or fridge off this system to use the excess 270Wh of the daily energy production. Or better yet, be able to sell the excess power. In the future power grid this will be possible.
- URSpider94 9y agoIt's possible today, almost everywhere in the USA. In fact, the power company will usually buy it from you at the same rate that they are charging. My house is turning the meter backwards as we speak. To do this, you need extra components to protect your house, the power grid, and the electricians who work on it.
- reaperducer 9y agoWill the landlord notice? Maybe not. Will the wife notice all the wires all over the place? You bet!
- deleted 9y ago[deleted]
- bonniemuffin 9y agoBecause men love electronics projects and women love keeping a tidy house and ruining their dreams, am I right?
- nikodunk 9y agoHahaha both of those comments were some of the most entertaining on here!
- dlss 9y ago> Because men love electronics projects and women love keeping a tidy house and ruining their dreams, am I right? I don't think this is accurate. Personally, I've had a lot of trouble finding people of either gender who are interested in electronics. I might be overstepping here, but it sounds like maybe you should talk to you wife and see what can be done to minimize the negative externalities caused by your hobby? It's hard to imagine she would actually want to ruin your dreams. I don't have a wife, but I know my girlfriend became a lot more supportive once I started keeping half-finished projects in the spare bedroom, and started putting in an effort to clean up my projects a bit more before letting them out. Just my $0.02 obviously.
- icebraining 9y agoI believe bonniemuffin was being sarcastic.
- bonniemuffin 9y agoI'm a female electronics hobbyist. Definitely sarcasm. :)
- Xeroday 9y agoQuite a side note: If you're renting in SF, your landlord needs to provide you with heating (http://sfrb.org/topic-no-257-minimum-heat-requirements http://sfrb.org/topic-no-257-minimum-heat-requirements)
- nikodunk 9y agoThanks for pointing this out! I think our main problem was with the non-insulation of the property. Though I haven't been here for a winter yet. There's also the landlord leverage problem though with cheap apartment gems in expensive places (like SF), as I'm sure you know: "Oh you want more insulation? Sure, I'll fix your insulation/heating. Woops! The rent just went up?"
- URSpider94 9y agoHave you talked to your landlord about adding solar panels to the roof? He/she could install them and connect them to your apartment's service, which means you would get the power and the savings -- though you might reasonably expect some of the savings to go towards higher rents in the future. With the tax advantages, it's almost a no-brainer. It's even possible to apportion power between multiple units with PG&E in California. They even allow "neighborhood solar", where you can benefit from a larger system installed elsewhere, like over a parking lot. I would also +1 the other comments about thinking really hard about whether your system is safe in the event of high winds. Solar panels are basically large sails, you'd be surprised what a 50 or 60 mph wind gust (likely to happen once or twice a year) can do. If you plan on doing this, check your lease - many landlords forbid putting things on the roof or hanging outside windows, or running wires on the exterior of the building.
- rosser 9y agoDoesn't PG&E charge customers who have residential solar installs a higher rate, because they have residential solar installs?
- URSpider94 9y agoIn a word, no. They do now tack on a monthly minimum fee that only applies if, over the course of a year, you use less than the sum of the monthly minimums. So, if you install a project so large that it zeros out your bill, you'll end up paying $100 or so per year to be tied to the grid. Otherwise, the rates are the same as you would pay without solar.
- maxmax 9y agoFor heating, you could bring in a small refrigerator rather than a resistive load. Get something besides heat for your power.
- sitkack 9y agoPlease bolt the panel down, if wind picks it up and blows it off the roof it could easily kill someone.
- Retric 9y agoI really doubt the wind is going to pick up a 2'x4' ~20lb panel like that when it's flat on a roof. Now if he had lifted an edge to try and get a better angle with the sun that would IMO be a much larger issue.
- mbreese 9y agoNo, that could easily happen. The parent was right, that panel should be secured in some way. Wind gusts can do some crazy things.
- Retric 9y agoFirst, there are no hurricanes or tornadoes in that area. So, you can work out max wind via historical data, but 85MPH is not going to be enough to move it over that lip. The skin effect around a building drastically reduces the forces involved.
- quickben 9y agoYou aren't accounting for a million other things that can happen.
- Retric 9y agoI have no problem saying bolting something to the roof is a good idea, I just don't think the wind in that area is going to lift that specific object. Move sure, lift no. So, saying any if the actual significant reasons to bolt it does haze zero influence on my objection.
- serf 9y ago"Really doubt" is probably a poor level of confidence with regards to a decision that may or may not kill someone.
- mdb333 9y agoA couple nice things about SF on this topic: 1. Davis Stirling (Housing related laws) mandates that building associations cannot prohibit owners from installing solar panels. Basically, they have to work with you to find a way and can't just say no. 2. As of this year, SF is the first city to require that all new buildings (10 stories or less) have solar installed.
- arcaster 9y agoAnother excuse to raise rent...
- Dylan16807 9y agoIt's been clearly shown that they don't need excuses to raise rent. Solar on an apartment building wouldn't impact the cost too much. The real issue is whether construction/zoning is allergic to density.
- backtoyoujim 9y agoHow many buildings are being built in SF that are 10 stories or less ?
- URSpider94 9y agoA darned lot of them. SF is very much a low-rise city, vast swaths of the city are no more than 2-3 stories. Part of why there is such a housing crunch...
- quickthrower 9y agoIs the flat panel on the roof optimal? Maybe at the equator but on our house we angle them to catch more of the sun throughout the day. Also I echo sentiments of whether the landlord and/or building supervisor would be happy and also the electrics regulations in your country. It's only 12v but is this legal to hang loose wires down the building?
- cjonas 9y agoObvious Problems: 1: You're not using a pure sine wave inverter so right off the back you are losing significant efficiency (Most the things you're charging use DC power anyways so it would be better to just get a nice DC charger). 2: If you are discharging your battery past 50%, you're going to significant reduce it's life span.
- k__ 9y agoI asked this myself too. Aren't most electric devices used today DC?
- cjonas 9y agoEverything that runs off a battery is DC. However, for the past 4 months, I've been charging all my devices off solar/battery (working-travel vacation in a van). I have run into some issues with certain devices not accepting charge. I think it has more to do with the device charges themselves than the power source. For example, my girlfriends Motorola Droid Turbo won't charge at all anymore off the 2.1 amp usb chargers. My S7 has no problems. Her cheap windows laptop will also sometimes refuse charge temporarily. Battery voltage is reliably between 12.3-13.0, which makes me think it's an issue with the chargers themselves.
- 100ideas 9y agoDitto re: battery capacity. Using all 35 Amp-Hours repeatedly will destroy the battery. Anode terminals dissolve during discharging. They are electrolytically plated (thickened) during charging. So repeated full-discharging can reduce their solid volume to such an extent that they cannot be fully restored during charging. In general, "deep-cycle" lead-acid batteries shouldn't be discharged to less than 50% of their rated capacity to ensure a healthy, long life in an off-grid solar setup like this one. So more like 17 yrs to repayment - as long as he hasn't already bricked his battery.
- mrbill 9y agoAfter Hurricane Ike (and 8 days without power) I built almost this exact setup to power my CPAP machine in case of another long-term power outage.
- winter_blue 9y agoI wonder if you can mount this over a roof rack for a plug-in hybrid car like he Chevy Volt/Bolt. It'd be an amazing way to charge your car. Although, 200 W might be a bit too low for the Chevy Volt. It draws circa 100 W when charged via the slow charger that you plug in to an outlet.
- taneq 9y ago> It draws circa 100 W when charged via the slow charger that you plug in to an outlet. 1kW - 2kW, surely? 100W would take days to charge.
- diafygi 9y agoI work in solar, and your panel really, really, REALLY needs to be secured from wind. Luckily, they make ballast mounts that don't require screwing into the roof[1][2]. [1]: http://www.orionsolarracking.com/commercial-roof-mount/ballasted/ http://www.orionsolarracking.com/commercial-roof-mount/balla... [2]: https://www.civicsolar.com/products/racking-mounting/application/Flat%20Roof%20-%20Ballast/manufacturer/orion-solar-racking-143/type/Ballast https://www.civicsolar.com/products/racking-mounting/applica...
- nikodunk 9y agoGot it! Thanks for the input. Damn that drives up cost, though. I'll work on securing it with weights and post an update.
- agumonkey 9y agoIf that thing catch up wind and fall you'll surely have to pay a lot more. It's surprisingly quick how wind can shift large surface like this.
- coltonv 9y agoFunny that we live in a world where one renewable energy source is powerful enough to (literally) blow away another.
- ilaksh 9y agoRight which is why I believe that after the coming consumer solar revolution there will be something similar with wind energy. Especially with newer VAWT designs and areas that have a lot of wind. They compliment each other so wind can continue producing at night.
- jsingleton 9y agoFor anyone curious, a VAWT is a Vertical-axis wind turbine (https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine https://en.wikipedia.org/wiki/Vertical_axis_wind_turbine). I always thought these were less efficient than the conventional designs but they're clearly simpler.
- deleted 9y ago[deleted]
- arcaster 9y agoWhy not build a small super-capacitor or lithium ion bank that you'd charge at work? Also, unless you have perfect weather (I.e. the Bay Area) and require no energy for HVAC this system is almost useless.
- adrianmonk 9y ago> Renters don’t need permission from their landlords to place things on their windowsill and rooftops if it’s not altering the building This has never been the case in any apartment community I've lived in, ever. Every time I've looked into anything like this, the lease says I have to follow community rules, and those rules include stuff like pool hours and parking but also say I can't put foil in my windows, have a window AC unit, etc. I'm sure there are some landlords who won't notice or won't care if you do this, but it's just not true in general that renters only need permission for things that alter the building.
- nikodunk 9y agoGood point. I'll clean up the language there. I've never lived in a non-ac unit and non-satellite dish place, but I probably have friends who do. How to work around that then? You could only use an ESCO (energy service company) on the east coast or cleanpowerSF for those scenarios.
- dragonwriter 9y ago> I'll clean up the language there. I've never lived in a non-ac unit and non-satellite dish place Well, satellite dishes are legally protected by an FCC order, but that doesn't apply to other things.
- sbuttgereit 9y agoThe fact is, making any sort of broad statement about what you can or can't do, landlord be damned, is a tough thing. You get into a morass of local and state laws that may very well vary from jurisdiction to jurisdiction. This is assuming, of course, it's not just easier to extend the courtesy of talking to the landlord in advance.
- Spooky23 9y agoThat's the downside to living in complexes!
- lubujackson 9y agoCool. One caveat in SF (and elsewhere, I'm sure): since I work from home my electricity usage is way higher than the PG&E norm (which itself seems aspirationally low). Of course, PG&E uses this to charge me huge "overage" charges so using a solar panel to offset some of those charges might actually make this economically viable.
- mindslight 9y agoOne of the biggest cost/safety/longevity factors here is the usage of a storage battery. This is necessary because OP presumably uses most power at night, and is unable to use the grid as virtual storage due to all the complexity that brings. If one's usage was mostly in the day or even constant, they could forgo the storage batteries and setup a system to supply specific loads, making up any shortfall from the grid. This would take a different type of "inverter" to avoid becoming grid-tied. I'm imagining a production circuit being based around a 170VDC bus (power factor? who cares!), but that's probably currently rare/custom/expensive. You could DIY the same type of thing with a nominal 12V bus (or 48V, depending on your loads) and DC distribution, from off the shelf components.
- deleted 9y ago[deleted]
- SwellJoe 9y agoI've been using rooftop solar for many years; I live in an RV (for a total of about 7 years, spread across two different RVs, both with solar on the roof). I currently have a 400W system. It makes extremely good economic sense in my case, because it enables me to live comfortably off-grid for weeks or months at a time; which can save hundreds of dollars a month in RV park fees, when I'm traveling. But, the talk of powering water heater, heating, AC, etc. from a little DIY solar system is extremely optimistic. I've done the math, and I couldn't run my AC from the number of solar panels that I could fit on my roof. I can fit 900 watts worth, an additional couple hundred watts on the truck, if I really wanted to get extreme and was willing to connect/disconnect them every time I drove the truck away from the RV. That's just not enough. It could power a small window unit as long as the sun is up, but overnights would kill a small battery bank dead (like dead dead, not just discharged, as repeatedly discharging below about 50% reduces the life of lead acid batteries by a huge amount) in short order. With a big enough inverter and a bigger battery bank, you can run microwave or toaster oven for short periods of time (I do). But any big amperage device that runs for extended periods of time (like heating, AC, and water heater) is not in the cards for small solar systems. Battery replacement also needs to be taken into account. In my experience, you get about 3 good years, and another year of limping along, from this kind of workload on this kind of battery. He's being more kind to his batteries than I am to my batteries (I usually end up running down to about 60% each day when off grid), so he might get another good year. But they probably won't even be limping along after five years. But, the good news is that solar panels are extremely durable. They're often warrantied for 25+ years! And, the expected output after that length of time is still pretty good. So, if batteries get better, our systems today will get better just by replacing one component, because everything else is gonna keep working forever (well, cheap charge controllers die sometimes, but the panels are practically forever parts).
- msangi 9y agoDoes the panel produce the same amount of energy every season? I know that in most of Europe the production during summer months is way higher than during winter and that needs to be taken into account
- kerbalspacepro 9y agoSan Fransisco is at about the same latitude as Gibraltar, so while he will see seasonal fluctuations unless he changes its angle of incidence (but hes laying it flat, so...) However, he will not see as big a difference as, say, somebody in Germany.
- bvanderveen 9y agoCan't imagine why OP has an inverter in the stack when everything connected to it is DC.
- nikodunk 9y agoBecause it's easier and I don't want to fry my $1500 laptop with some hair-brained project's DC-power spike. But I admit that's not really well thought through and an earlier version of this project was DC only. Also, the main inspiration for this project was DC only, as I mentioned in the article (but reposted here: https://arstechnica.com/gadgets/2015/08/op-ed-how-i-gave-up-alternating-current/ https://arstechnica.com/gadgets/2015/08/op-ed-how-i-gave-up-...)
- gwbas1c 9y agoThese already exist as self-contained kits: https://www.amazon.com/dp/B00GV3XRDW/ref=asc_df_B00D5RVMAM5086472/?tag=hyprod-20&creative=394997&creativeASIN=B00D5RVMAM&linkCode=df0&hvadid=167143550553&hvpos=1o1&hvnetw=g&hvrand=16267220506877723508&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9001821&hvtargid=pla-308511758090&th=1&psc=1 https://www.amazon.com/dp/B00GV3XRDW/ref=asc_df_B00D5RVMAM50... What I think would be interesting is to use a relay to fall back to grid power once the battery dies.
- nikodunk 9y agoNice! 600 bucks though?! I guess I'd have to sell this package for 600 for any kind of profit margin... Reading the reviews on Amazon of the Yeti system though, I'm not sure they've solved all the issues for 3x the price.
- gopikori 9y agoI have a similar setup at my apartment in India. It is functional since more than two years now. Its total 140Watt panels, popping out of my bedroom window [Photo: https://photos.app.goo.gl/S4WR5gbrGu0z8IQB2 https://photos.app.goo.gl/S4WR5gbrGu0z8IQB2]. It has a 12V battery and 10A solar charge controller. It produces good enough energy to power my room. I hate inverters, all my lights/fans in room are based on DC 12V. I use car chargers to charge mobile phones and to run a LED wall clock.
- wfunction 9y agoThis is awesome. The one question on my mind is: is there really no barrier to doing this, like regulation of some kind? I would imagine there's an added fire risk with that kind of battery at home?
- quickthrower 9y agoWhat about safety? Is there earthing, fuses, RCD breakers in this? Fire risk? Is it worth it? Fuck have I been hellbanned?
- kogepathic 9y agoThe author's calculations for the capacity of the battery are very wrong and the battery will not last many years the way he's using it. Deep cycle lead-acid batteries should not be discharged below 50% (known as Depth of Discharge, or DoD) unless you really want to kill them quickly. The author's calculations assume he can drain the battery 100% (35Ah), which while technically correct, will kill his battery very quickly. Unfortunately the manufacturer doesn't provide any data on the capacity over discharge cycles at different DoD's [0], but I can guarantee the author will significantly shorten the battery's lifespan by discharging it so deeply. If you want some idea of the effect of DoD on battery health, Hoppecke have a very good chart in their datasheet on page 43. [1] At 50% DoD, the battery will last for approximately 3000 cycles, or 8 years. At 90% DoD, the battery will only last for 1500 cycles or 4 years. If you want to go for 100% DoD in solar, you're looking at Redox flow or Lithium battery technologies, both of which are more expensive than Lead-Acid. There are other problems with this setup as well. At $17, the charge controller is very unlikely to support an equalization charge mode, which is required to periodically balance the cells within the battery to ensure a long lifespan. The author would be better off skipping AC entirely and charging their MacBook/iPad from a car charger which operates on 12V. DC lights can also be purchased quite inexpensively. The AC inverter is likely putting out something closer to a square wave than a sine wave, and the low voltage cut-off is far too low to avoid damaging the battery. This is really a case of "you get what you pay for" and for such cheap components, the system will not perform well or last for very long. If this sounds really negative, I'm sorry. I want more people to become energy independent, but if you follow the author's example, you're going to have a very bad time. If you are seriously interested in going off grid, you should invest in quality components like Victron, Outback, Studer, Hoppecke, etc. Something like the Victron EcoMulti would be a good choice for someone who wants an easy to use system that's been designed for longevity. [2] [0] http://www.expertpower.us/exp12350 http://www.expertpower.us/exp12350 [1] https://www.hoppecke.com/fileadmin/Redakteur/Hoppecke-Main/Products/Downloads/Montagehandbuch_verschl_EN_final.pdf https://www.hoppecke.com/fileadmin/Redakteur/Hoppecke-Main/P... [2] https://www.victronenergy.com/solar-pv-inverters/ecomulti https://www.victronenergy.com/solar-pv-inverters/ecomulti
- mindslight 9y agoTo be fair, the DoD vs cycle numbers aren't as dire as they first look. Even an ideal deep-discharge battery would have a 1/x curve, as the real metric is total energy stored, which is proportional to DoD*ncycles vs DoD. For instance, for the two datapoints you gave. At 50% DoD, the battery will have stored 1500 times its capacity over its life. At 90% DoD, the battery will have stored 1350 times its capacity over its life. This is only a 10% degradation.
- anderspitman 9y agoI'm hoping to build a similar system in the next year or two. Biggest difference is I plan on building battery banks out of lithium-based 18650 cells. You can salvage them from old laptop batteries, even dead ones (one bad cell can bring the whole battery down, even if the other cells are fine). 18650s are also used in Tesla's car batteries [0] and Powerwall. They literally just cram thousands of them in there. There are some youtubers who have done tons of stuff with them [1][2]. [0] https://youtu.be/NpSrHZnCi-A https://youtu.be/NpSrHZnCi-A [1] https://www.youtube.com/user/jehugarcia https://www.youtube.com/user/jehugarcia [2] https://www.youtube.com/user/nocrf50here https://www.youtube.com/user/nocrf50here
- scotty79 9y agoYou could save some energy by driving Led lights directly from the 12V battery. Not through an inverter. Doeasn't matter in this case though since one of the things he's running is electric heater. When you are usin lights you are just getting bit more heating comming from inverter.
- agumonkey 9y agoI've been chatting a bit about thermal building design. This article reminds me that for most entertainment or work, we don't need much energy. Cost comes from AC, heater, fridges. Other household appliances too but these are transient. But with carefully dimensionned walls, you can slow the heat spread enough to avoid AC most of the time. Surely we could keep our energy needs low if we wanted to.
- luxpir 9y agoHe mentions fridge/freezer - I'll just draw attention to this project[0] where the smart guy uses a chest freezer as a fridge with an external thermostat. It has better insulation and design (cool air stays in when open), so ends up much more efficient and can be run on minimal power. Just 90 seconds of run time per hour. There are other ways to do this in mobile setups, or with inverters in any setup, using mini-freezers, simple electronics to turn the inverter on/off and a small panel. See /r/vandwellers[1]. [0] - https://www.treehugger.com/kitchen-design/man-retrofits-freezer-to-make-an-ultra-efficient-fridge.html https://www.treehugger.com/kitchen-design/man-retrofits-free... [1] - https://www.reddit.com/r/vandwellers/search?q=freezer&restrict_sr=on&sort=relevance&t=all https://www.reddit.com/r/vandwellers/search?q=freezer&restri...
- agumonkey 9y agoHow hard would it be to add regenerative braking to that ? if not already installed.
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- PascLeRasc 9y agoVery cool project and great writeup! It seems like every week I learn about a new Google microservice (Google Sunroof here).