For solar power, is there something like going half-off-the grid?
April 19, 2018 1:48 PM Subscribe
Nobody really talks about rigging a house for just a bit of solar energy.
Living in Puerto Rico where sunshine is no problem. A on-line calculator has my city about comparable to Phoenix, AZ in terms of kWh/m^2/day
I don't have the money to plunge $10+K dollars into a solar powered house. On the other hand, I see multi-piece solar kits that seem to have everything: except for a lot of power.
Here's one in the $3K to $4K range.
Here's one much less capable in the under $2K range.
Is it possible and reasonably straightforward to rig up one room with solar powering with this sort of kit? Enough energy to run fans, computers, a television and VCR, let's say three devices at a time from one heavy duty extension cord.
I'm asking because after the Puerto Rican grid went down yesterday, and having used my propane portable generator for the first time, I realize what a hassle it will be to use for an extended outage.
If I can fix up one room that can function, that may be better than chasing down propane, worrying that thieves will steal it from our front lawn at night, (We locked it up but it is so loud that we would never hear a thief until they cut the motor), running out of propane in the middle of everything, only having one room's worth of power, anyway, etc.
I figure when there is not an outage we could use the incoming electricity to reduce our electric bill by running appliances in the single room.
I recognize that air conditioners, refrigerators and some appliances require a lot of energy, and I'm not planning on putting those on the solar grid. My roofing has a good angle to catch the sun, and it has an easy way to run the wiring down to the garage where the inverter and batteries would be.
I'm handy enough to do most of what I imagine the installation will be.
Living in Puerto Rico where sunshine is no problem. A on-line calculator has my city about comparable to Phoenix, AZ in terms of kWh/m^2/day
I don't have the money to plunge $10+K dollars into a solar powered house. On the other hand, I see multi-piece solar kits that seem to have everything: except for a lot of power.
Here's one in the $3K to $4K range.
Here's one much less capable in the under $2K range.
Is it possible and reasonably straightforward to rig up one room with solar powering with this sort of kit? Enough energy to run fans, computers, a television and VCR, let's say three devices at a time from one heavy duty extension cord.
I'm asking because after the Puerto Rican grid went down yesterday, and having used my propane portable generator for the first time, I realize what a hassle it will be to use for an extended outage.
If I can fix up one room that can function, that may be better than chasing down propane, worrying that thieves will steal it from our front lawn at night, (We locked it up but it is so loud that we would never hear a thief until they cut the motor), running out of propane in the middle of everything, only having one room's worth of power, anyway, etc.
I figure when there is not an outage we could use the incoming electricity to reduce our electric bill by running appliances in the single room.
I recognize that air conditioners, refrigerators and some appliances require a lot of energy, and I'm not planning on putting those on the solar grid. My roofing has a good angle to catch the sun, and it has an easy way to run the wiring down to the garage where the inverter and batteries would be.
I'm handy enough to do most of what I imagine the installation will be.
Something to consider is taking a particular load off the grid.
How about doing a load calc on the fridge (and maybe a chest freezer) and build a system to give those items a few days of automony using a few batteries. Those are a couple of things worth always having power. In any sort of `no power` situation, being able to make some ice would make you a hero.
SandPine
posted by sandpine at 2:52 PM on April 19, 2018 [1 favorite]
How about doing a load calc on the fridge (and maybe a chest freezer) and build a system to give those items a few days of automony using a few batteries. Those are a couple of things worth always having power. In any sort of `no power` situation, being able to make some ice would make you a hero.
SandPine
posted by sandpine at 2:52 PM on April 19, 2018 [1 favorite]
Talk to the electric company. Ideally, you would produce solar and feed it into the ground, reducing your bill.
Otherwise, you are most likely to have solar panels and a controller and charge a battery bank, using it as needed for lights, fridge, etc.
posted by theora55 at 3:03 PM on April 19, 2018 [1 favorite]
Otherwise, you are most likely to have solar panels and a controller and charge a battery bank, using it as needed for lights, fridge, etc.
posted by theora55 at 3:03 PM on April 19, 2018 [1 favorite]
I just PM'd you--I know someone in Puerto Rico who has their own solar setup and could probably give you a lot of information.
posted by Slinga at 3:13 PM on April 19, 2018 [3 favorites]
posted by Slinga at 3:13 PM on April 19, 2018 [3 favorites]
It would cost more and you'd need to have it done professionally, but you could have a small grid that normally feeds into the house while it's on the grid and reduces your electric bill and a transfer switch that would remove your house from the grid entirely and allow you to power specific circuits in the house from just the solar during an outage.
It's not something to mess around with unless you're experienced with electricity, as you can kill yourself or burn the house down if you don't know what you're doing.
posted by Candleman at 3:38 PM on April 19, 2018 [2 favorites]
It's not something to mess around with unless you're experienced with electricity, as you can kill yourself or burn the house down if you don't know what you're doing.
posted by Candleman at 3:38 PM on April 19, 2018 [2 favorites]
Having a solar setup with a transfer switch for backup power necessarily involves having a battery bank as well. Solar doesn't produce energy based on demand, it produces it based on how much sunlight is hitting the array, and that can fluctuate a lot—think clouds. The deal is that you draw your power from a battery bank, which is charged by your panels. The transfer switch and associated gear handle things like keeping the batteries charged and deciding whether to draw from the batteries or the grid, and the batteries supply the backup power.
Those kits you're seeing on Amazon aren't useless though. They're not the equivalent of having a natural gas generator hooked up to the city gas line with an automatic transfer switch that kicks everything on when the power dies; they're the equivalent of having a portable generator and running an extension cord in through a window to run your fridge and furnace and maybe keep your electronic devices charged up. That's still a big upgrade from having no power at all, but aside from the noise a regular portable gas generator is going to be much more cost-effective.
posted by Anticipation Of A New Lover's Arrival, The at 4:05 PM on April 19, 2018 [3 favorites]
Those kits you're seeing on Amazon aren't useless though. They're not the equivalent of having a natural gas generator hooked up to the city gas line with an automatic transfer switch that kicks everything on when the power dies; they're the equivalent of having a portable generator and running an extension cord in through a window to run your fridge and furnace and maybe keep your electronic devices charged up. That's still a big upgrade from having no power at all, but aside from the noise a regular portable gas generator is going to be much more cost-effective.
posted by Anticipation Of A New Lover's Arrival, The at 4:05 PM on April 19, 2018 [3 favorites]
With all the caveats about electric and falling off the roof safety, why not? Keep both system isolated and remember that a battery drained is a dead battery so you need to shut off usage pretty early in the night. Find the wattage of all the devices you want to use, add them and get a rough calculation how long the battery will last.
Read Handy Bob's offroad blog in depth, he has all the detail for a safe workable system.
Do a lot of research, very likely buying parts separately could save a bunch. Calculate the cable runs well and buy a heaver gauge will improve the system and the controller could make a big difference.
posted by sammyo at 4:16 PM on April 19, 2018 [1 favorite]
Read Handy Bob's offroad blog in depth, he has all the detail for a safe workable system.
Do a lot of research, very likely buying parts separately could save a bunch. Calculate the cable runs well and buy a heaver gauge will improve the system and the controller could make a big difference.
posted by sammyo at 4:16 PM on April 19, 2018 [1 favorite]
Best answer: I don't have any experience with kits of the type you link to (I do have a grid-tied solar system with no battery storage that was installed when I bought my house and is completely worthless in an outage situation). However, if the kit comes with complete with a set of batteries and an inverter, it does not seem to me that it would be too complicated to set up and use it, via an extension cord, to power a limited number of mission-critical electrical loads in a single room under both everyday and emergency conditions.
The amount of savings you'll see from these kinds of systems as a supplement to your grid power will be minimal: the smaller one will probably give you at least 50-75 kwh of electricity a month (probably on the high end given your location) and the larger one more like 100-150. Electricity is significantly more expensive in Puerto Rico than the US average , so that helps! If you're paying $0.20 per kwh then you can expect to save something like $10-15 a month for the small system, and $25-30 a month for the large one. So it's a pretty long timeframe before either system would pay for itself, which is part of the reason you don't see a lot of people buying such systems just to save money. But if you couple in the convenience factor compared to a gas generator, then it's not a completely ridiculous idea. Definitely look into any tax incentives as well.
posted by drlith at 6:52 PM on April 19, 2018 [1 favorite]
The amount of savings you'll see from these kinds of systems as a supplement to your grid power will be minimal: the smaller one will probably give you at least 50-75 kwh of electricity a month (probably on the high end given your location) and the larger one more like 100-150. Electricity is significantly more expensive in Puerto Rico than the US average , so that helps! If you're paying $0.20 per kwh then you can expect to save something like $10-15 a month for the small system, and $25-30 a month for the large one. So it's a pretty long timeframe before either system would pay for itself, which is part of the reason you don't see a lot of people buying such systems just to save money. But if you couple in the convenience factor compared to a gas generator, then it's not a completely ridiculous idea. Definitely look into any tax incentives as well.
posted by drlith at 6:52 PM on April 19, 2018 [1 favorite]
Response by poster: After work hours I'm limited to texting, so I will keep my answers brief until tomorrow. No problem with roof safety, the roof is flat except for two parts which slope up. These make for taller ceilings. I did take a course in wiring and I've done small jobs. I think I'd run this through its own switch box.
posted by dances_with_sneetches at 6:56 PM on April 19, 2018
posted by dances_with_sneetches at 6:56 PM on April 19, 2018
drlith has it exactly right. These kinds of systems are designed to provide standalone power via the built-in outlets on the inverter. They are not supposed to interact with your house's wiring. They're not up to code for that and also wiring up only part of your house for solar backup (even if they were up to code) would either require a bunch of additional equipment (to keep it separated from the rest of your house's power system) or else be just hilariously dangerous. Solar is not like other household wiring,
it involves direct current for one thing and you have to deal with backfeeding for another, neither of which are otherwise normal things to have in a house. Please don't jerry-rig one of these contraptions into your house's electrical system.
Using one to run a few appliances via extension cord is perfectly acceptable and useful and is what these systems are designed for. If you want to have one of these, the way to use it is to just plug stuff into it. They are standalone systems for providing limited power in off-grid situations or as an emergency backup. The beauty of them is that they are self contained and do not require specialized electrician skills. Don't try to make them be more than they are supposed to be.
posted by Anticipation Of A New Lover's Arrival, The at 7:07 PM on April 19, 2018 [2 favorites]
it involves direct current for one thing and you have to deal with backfeeding for another, neither of which are otherwise normal things to have in a house. Please don't jerry-rig one of these contraptions into your house's electrical system.
Using one to run a few appliances via extension cord is perfectly acceptable and useful and is what these systems are designed for. If you want to have one of these, the way to use it is to just plug stuff into it. They are standalone systems for providing limited power in off-grid situations or as an emergency backup. The beauty of them is that they are self contained and do not require specialized electrician skills. Don't try to make them be more than they are supposed to be.
posted by Anticipation Of A New Lover's Arrival, The at 7:07 PM on April 19, 2018 [2 favorites]
Best answer: Note several negative reviews & comments about a similar system/same seller to one of your top choices. The numbers there just don't add up. He's saying it is a 3.3 kW system when actually it is a 0.84 kW system.
FWIW we have a 7 kW system (connected to the grid) and it comes close to generating all the power needed for our 1100 sq foot home for the month in the sunnier months. However, it does this by generating more than we need while the sun is shining & then (of course) nothing at all in the dark.
I point that out so you understand how underpowered a 0.84 kW system is going to be. Personally I would consider a 0.84 kW system for $3700 to be something of a rip-off and fairly useless.
Personally I would be looking at something maybe more like this. That is 5kW at about $8000. So 2X your price but generating 6X the power. You lose the benefit of batteries but gain the benefit of generating 6X the power every day, all year long. Also there are some federal rebates etc so your total cost might be less than $8K.
Contrary to what some reported above, our grid-tied system has a couple of special dedicated plugs and this makes it quite useful during a power outage. If our mains power goes out we flip a switch & then we can connect an extension cord to these dedicated plugs & run a refrigerator, charge our laptops, etc. As long as the sun is shining brightly we can run a lot of things--more power than we generally use in our whole house at that time of day--but since it is not connected to the in-house wiring we really don't/can't run everything but just rather a few selected items like the refrigerator, freezer, a computer, a fan etc.
And since we don't have any battery packs this only works as long as the sun is shining. But if we really wanted we could charge batteries & then run things via battery/inverter once the sun goes down.
Still, it's a lot better than nothing during a power outage and we have in fact used it in that manner during power outages.
posted by flug at 9:55 PM on April 19, 2018 [3 favorites]
FWIW we have a 7 kW system (connected to the grid) and it comes close to generating all the power needed for our 1100 sq foot home for the month in the sunnier months. However, it does this by generating more than we need while the sun is shining & then (of course) nothing at all in the dark.
I point that out so you understand how underpowered a 0.84 kW system is going to be. Personally I would consider a 0.84 kW system for $3700 to be something of a rip-off and fairly useless.
Personally I would be looking at something maybe more like this. That is 5kW at about $8000. So 2X your price but generating 6X the power. You lose the benefit of batteries but gain the benefit of generating 6X the power every day, all year long. Also there are some federal rebates etc so your total cost might be less than $8K.
Contrary to what some reported above, our grid-tied system has a couple of special dedicated plugs and this makes it quite useful during a power outage. If our mains power goes out we flip a switch & then we can connect an extension cord to these dedicated plugs & run a refrigerator, charge our laptops, etc. As long as the sun is shining brightly we can run a lot of things--more power than we generally use in our whole house at that time of day--but since it is not connected to the in-house wiring we really don't/can't run everything but just rather a few selected items like the refrigerator, freezer, a computer, a fan etc.
And since we don't have any battery packs this only works as long as the sun is shining. But if we really wanted we could charge batteries & then run things via battery/inverter once the sun goes down.
Still, it's a lot better than nothing during a power outage and we have in fact used it in that manner during power outages.
posted by flug at 9:55 PM on April 19, 2018 [3 favorites]
My situation isn't at all Puerto Rican; we (NL) have a robust grid, give or take some unfortunate backhoe activity, and no immediate fear of power shortages. The solar panels on my roof are merely meant to reduce my energy bill (I hesitate to say 'footprint', because manufacturing those panels have to weigh in there). The inverter is grid-tied so no dice if the grid is out, although the manufacturer offers a modification kit to allow autonomous operation with a battery reserve.
For your situation, and the budget you mention, I would first look to acquire a couple of second-hand UPS units (one for your 'autonomous' room, one for your fridge and freezer) that can have battery extensions hooked up. Those tend to be cheap and sometimes even free when their batteries are busted, but those are easily replaced and not that expensive if you stay away from the vendor parts; most of them run on a number of generic 12V, 7Ah to 15Ah SLA batteries. Figure out the power consumption over time of the gear you need to keep running: UPS ratings tend to specify half an hour runtime at maximum load, so a 1000VA unit can easily run a small computer, a DSL modem and a few LED lights for the better part of an evening. With a battery extension you can run more stuff, and/or longer. I got handed a 1000VA unit from work which keeps about 100W of computer gear running for at least four hours even with mediocre batteries, and a 3000VA one with two battery extenders that has kept some 400W of load going for nearly 8 hours with plenty to spare (battery level was down to 40%). All free, as long as they didn't have to deal with moving that heavy shit.
This simplifies the solar part a bit, because you can now just install a couple of panels with a simple autonomous inverter, which you simply plug the UPSes over into to charge from when the grid goes out. Inverter and panel capacity has been covered in previous answers.
posted by Stoneshop at 2:58 AM on April 20, 2018
For your situation, and the budget you mention, I would first look to acquire a couple of second-hand UPS units (one for your 'autonomous' room, one for your fridge and freezer) that can have battery extensions hooked up. Those tend to be cheap and sometimes even free when their batteries are busted, but those are easily replaced and not that expensive if you stay away from the vendor parts; most of them run on a number of generic 12V, 7Ah to 15Ah SLA batteries. Figure out the power consumption over time of the gear you need to keep running: UPS ratings tend to specify half an hour runtime at maximum load, so a 1000VA unit can easily run a small computer, a DSL modem and a few LED lights for the better part of an evening. With a battery extension you can run more stuff, and/or longer. I got handed a 1000VA unit from work which keeps about 100W of computer gear running for at least four hours even with mediocre batteries, and a 3000VA one with two battery extenders that has kept some 400W of load going for nearly 8 hours with plenty to spare (battery level was down to 40%). All free, as long as they didn't have to deal with moving that heavy shit.
This simplifies the solar part a bit, because you can now just install a couple of panels with a simple autonomous inverter, which you simply plug the UPSes over into to charge from when the grid goes out. Inverter and panel capacity has been covered in previous answers.
posted by Stoneshop at 2:58 AM on April 20, 2018
Response by poster: Hi. All of your comments are good. I've sorted the situation out in my mind.
First. These lower end units sometimes talk about setting up for an RV or camping. (Typically the under $2000 range). That's kind of what I have in mind: making a room into the equivalent of an RV. And, frankly, if it can be set up for camping, it can be set up anywhere. However,
Second, I would like a bit more power (not a huge amount, but let's say 3kW) and a bit more sturdiness than take on your camping trip provides. That seems to be the case for the $2K to 4K dollar systems.
Third, some toss in battery arrays. That would be necessary, because I don't want a system that goes down at night.
I'll have to investigate closely what (or if there are any) systems out there that meet these standards for let's say, under $5K.
Ultimately, I want to do two things. Emergency energy when the Puerto Rico grid is down. One month for us after Maria. If I stayed using my generator for one month, it would have been about $1,000 for fuel. Of course I would have compromised and shut if off at times. And, there was no fuel to be found for most of that month, so it would have been useless.
The other thing is to regularly use some of the energy. This would be like the RV type of usage. As pointed out, it wouldn't save that much off the electric bill, but wouldn't hurt.
posted by dances_with_sneetches at 5:32 AM on April 20, 2018
First. These lower end units sometimes talk about setting up for an RV or camping. (Typically the under $2000 range). That's kind of what I have in mind: making a room into the equivalent of an RV. And, frankly, if it can be set up for camping, it can be set up anywhere. However,
Second, I would like a bit more power (not a huge amount, but let's say 3kW) and a bit more sturdiness than take on your camping trip provides. That seems to be the case for the $2K to 4K dollar systems.
Third, some toss in battery arrays. That would be necessary, because I don't want a system that goes down at night.
I'll have to investigate closely what (or if there are any) systems out there that meet these standards for let's say, under $5K.
Ultimately, I want to do two things. Emergency energy when the Puerto Rico grid is down. One month for us after Maria. If I stayed using my generator for one month, it would have been about $1,000 for fuel. Of course I would have compromised and shut if off at times. And, there was no fuel to be found for most of that month, so it would have been useless.
The other thing is to regularly use some of the energy. This would be like the RV type of usage. As pointed out, it wouldn't save that much off the electric bill, but wouldn't hurt.
posted by dances_with_sneetches at 5:32 AM on April 20, 2018
This is possible, but you aren't going to be running your TV and fridge and a window AC all night without spending more than you want to spend on batteries unless you get a great deal on a Leaf or Tesla battery pack.
I did a lot of thinking about this after Irma knocked my power out for a week and came to the conclusion that to do significantly better than a good USB solar charger, a couple of battery packs, and a Biolite stove I'd be looking at $6,000-$8,000 for an RV-style setup in a place where wiring in a transfer switch wouldn't be possible. IIRC it was 60% panels, 40% battery and that was assuming we quit running the AC a few hours after sunset. At the higher end it would have been possible to keep the AC running all night without killing the batteries assuming we were starting from full at the end of the day.
That said, I suspect it could be done more cheaply if you have some electronics skills such that you can build your own components from parts and have the space to safely use lead acid batteries rather than lithium ion packs. My estimate was using off the shelf components for a non permanent installation.
posted by wierdo at 6:15 AM on April 20, 2018
I did a lot of thinking about this after Irma knocked my power out for a week and came to the conclusion that to do significantly better than a good USB solar charger, a couple of battery packs, and a Biolite stove I'd be looking at $6,000-$8,000 for an RV-style setup in a place where wiring in a transfer switch wouldn't be possible. IIRC it was 60% panels, 40% battery and that was assuming we quit running the AC a few hours after sunset. At the higher end it would have been possible to keep the AC running all night without killing the batteries assuming we were starting from full at the end of the day.
That said, I suspect it could be done more cheaply if you have some electronics skills such that you can build your own components from parts and have the space to safely use lead acid batteries rather than lithium ion packs. My estimate was using off the shelf components for a non permanent installation.
posted by wierdo at 6:15 AM on April 20, 2018
To clarify a bit: the upside of using off-the-shelf UPSes is that they conform to code, and don't really care about mains voltage being out of whack, stuttering or out for a longer time. That's what they're meant for, and it also means you have quite some time to plug them into the backup source, selecting what is available (solar, generator on an overcast day, wind). On the output side you just plug in, using a power strip with a C14 plug on the lead, what you need to power and leave things that way; no need to switch stuff over once grid power is back.
Even though I redid the entire wiring myself in both houses I live(d) in without turning into a sparking skeleton or burning things down, I would stay away from anything that involved DIY parts to go from battery DC to mains AC, considering the currents involved and the consequences of getting things wrong. That's what I would leave to APC, Emerson, MGE, Tesla or whoever else has a solid reputation for that
posted by Stoneshop at 7:59 AM on April 20, 2018
Even though I redid the entire wiring myself in both houses I live(d) in without turning into a sparking skeleton or burning things down, I would stay away from anything that involved DIY parts to go from battery DC to mains AC, considering the currents involved and the consequences of getting things wrong. That's what I would leave to APC, Emerson, MGE, Tesla or whoever else has a solid reputation for that
posted by Stoneshop at 7:59 AM on April 20, 2018
This guy in PR had a similar idea, but it sounds like he had some electrical experience.
posted by BungaDunga at 9:59 AM on April 21, 2018
posted by BungaDunga at 9:59 AM on April 21, 2018
This thread is closed to new comments.
I think you may be a little confused about how 99% of people< use solar, which is on the grid, with the panels providing power to their house, and extra to the grid if available, during the day and then relying on grid power for their relatively low electricity needs overnight.
Why do they do this? Because the grid remains the cheapest "battery" by far. Putting a battery in will easily double the cost of an installation, and depending on power prices make ROI very long.
You have a more unusual situation because your grid is a bit crappy as a battery. But before thinking about wiring up a room etc, you should find out how much electricity you're actually using, and roughly when. This wull guide your decision and make for more productive conversations with installers. You could have more options than you think.
Everyone who is actually off grid has a back up generator I think you'll find. If the issue is noise etc some of the new petrol generators are surpsingly quiet. That could be the cheapest option for you.
BTW and finally you are not handy enough to do most of installation unless you're a qualified electrician. People die effing around with solar, if you're doing anything with electricity always always always pay for a professional.
posted by smoke at 2:05 PM on April 19, 2018 [8 favorites]