Help with emergency setup
- Thread starter Troady
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One thing to keep in mind is portability and structural damage that may occur during a hurricane. Having a big, fixed system assumes you still have a roof, solar panels and intact electrical wiring when it's over. When Fran came through North Carolina, there were sections of town where the houses were so damaged, the power company wouldn't restore power to those areas till the meters were removed or repairs were made and inspected. If you get told you have to evacuate, you can't take a big system with you. I pondered the options for a while and decided to build a portable system first. It's got a 200w solar suitcase panel that can charge at 10 amps, 3 inverters to power various loads and several 12v batteries that can be moved around as needed. Plus it can be run off a car battery. 1 inverter and battery (130 AH) can comfortably run my garage 18cf fridge/freezer for 18 hours before needing to be charged. Another runs the kitchen fridge and microwave. Depending on microwave use, it can run those loads for nearly a day as well. Charging can be done by a 60 amp Progressive Dynamics charger powered by the grid or a generator as well as the solar panels. I have a 300 watt small inverter for running networking and charging phones/tablets, ect. It can run for days on a charge and be recharged in an hour on the solar panel. It's all worked well on a couple of outages already. I'm starting to think about a larger, more permanent system now.
I was thinking in putting my solar panels in a structure on the ground, not on the roof. This way i can take the solar panels away just before a hurricane hits and mounting them back right after. I do have the space for that.
6 to 10 370-400 watts panels should not take more than 1 hour to be removed and stored.
They advice us to evacuate every time we get a hurricane, but i never do that, my house is solid enough to withstand a force 5 hurricane, and i like to be close to my things to take care of them when in need.
6 to 10 370-400 watts panels should not take more than 1 hour to be removed and stored.
They advice us to evacuate every time we get a hurricane, but i never do that, my house is solid enough to withstand a force 5 hurricane, and i like to be close to my things to take care of them when in need.
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Supposing i want to keep my normal home daily consumption of 1 Kwh, 24Kwh total. I will need to have 32 Kwh in storage/batteries to be able to use 70% of there in 24 hours. Same in solar panels for production, needs to recharge 32Kwh in the hours that the sun is able to recharge them, right ?. And been able to use the generator for backup of the sun or in case that cloudy days don`t allow a full charge. How many solar panels (taking for example a 370 watts panel) do i need?, same for batteries, taking for example a 200Ah life4po battery, how many should i need?. . Take in consideration that i only need the batteries to cover the 8-10 hours of the night, i can always start the generator in the morning (if no power from the grid is available or sun isn`t shinning) and recharge the batteries.
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MichaelK
Solar Wizard
What I can tell you right now is that ain't gonna happen! There is no more expensive why to generate electricity than with off-grid solar. If you want off-grid solar because you are planning for emergencies, then great. But do NOT expect in any way whatsoever that off-grid will ever save you money.
Hedges
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As Supervstech said, 12 hours of daylight is 5 or 6 effective hours of sun (equivalent hours of 1000W/m^2 noon sun).
800W (STC) of panels will produce 700W (PTC, realistic conditions) x 5 hours is 3500 Wh or x6 hours is 4200 Wh.
PV panels are cheap, cheaper than utility rates and cheaper than batteries. You don't want to run anything off batteries that you don't have to. For a power outage, you could plug refrigerator/freezer into a timer on the inverter so they only run during good sun hours. Then battery is only for lights & communications.
AGM/FLA/LiFePO4:
I use AGM because it is simple, dumb, has enough cycle life for the number of grid-backup events I anticipate, and a small bank can deliver 800A surge without a BMS getting in the way.
FLA (of the right quality) can last longer, is also cheaper. And more work, which I don't like. Worth considering for a larger bank.
LiFePO4 (commercially made) costs several times more than AGM but lasts proportionately more cycles. Worthwhile if you will cycle every night.
LiFePO4 (DIY) costs about 40% as much as AGM, so a great deal if you want to go through DIY. This chemistry can't be charged below freezing, which matters to many people but probably not you.
My system went the Big or Bust route, but makes some sense because it is grid-tie with net metering. The PV panels and grid-tie inverters are cost effective ($0.05/kWh). The add-on battery inverters and batteries are an overpriced luxury ($0.50 or $1.00/kWh), but they let the PV panels directly run my A/C, laundry, everything else during daylight hours (because they make a local grid for my house.)
I think there are some moderate priced inverters that support grid-tie, PV, batteries. SolArk comes to mind; one forum member recently completed an install in Florida.
800W (STC) of panels will produce 700W (PTC, realistic conditions) x 5 hours is 3500 Wh or x6 hours is 4200 Wh.
PV panels are cheap, cheaper than utility rates and cheaper than batteries. You don't want to run anything off batteries that you don't have to. For a power outage, you could plug refrigerator/freezer into a timer on the inverter so they only run during good sun hours. Then battery is only for lights & communications.
AGM/FLA/LiFePO4:
I use AGM because it is simple, dumb, has enough cycle life for the number of grid-backup events I anticipate, and a small bank can deliver 800A surge without a BMS getting in the way.
FLA (of the right quality) can last longer, is also cheaper. And more work, which I don't like. Worth considering for a larger bank.
LiFePO4 (commercially made) costs several times more than AGM but lasts proportionately more cycles. Worthwhile if you will cycle every night.
LiFePO4 (DIY) costs about 40% as much as AGM, so a great deal if you want to go through DIY. This chemistry can't be charged below freezing, which matters to many people but probably not you.
My system went the Big or Bust route, but makes some sense because it is grid-tie with net metering. The PV panels and grid-tie inverters are cost effective ($0.05/kWh). The add-on battery inverters and batteries are an overpriced luxury ($0.50 or $1.00/kWh), but they let the PV panels directly run my A/C, laundry, everything else during daylight hours (because they make a local grid for my house.)
I think there are some moderate priced inverters that support grid-tie, PV, batteries. SolArk comes to mind; one forum member recently completed an install in Florida.
MichaelK, You may be right, i can`t tell, do not have any experience whatsoever with solar. But theoretically using 3000 cycles lifepo4 batteries and well known solar panels known to go for at least 20 years, you should be able to save money.
I am spending right now around $2800 yearly in utility bills. If i spend $5000 in a solar installation, and this reduce my utility bill to $1000 a year, i am getting my money back after 3 1/2 years.
$2,800 yearly utility bills x 5 years=$14,000
$5,000 in the solar power equipment and installation and $5,000 of $1000 bills a year for 5 years Total $10,000 in 5 years.
There are many variants that have to be taking in consideration here, and i don`t know many of them, just beginning with all of this. But many of you doing solar for 10 years or more should known better. In a southern state like CA, AZ, NM, TX or FL, solar power should be cheaper than the local utility company.
I am spending right now around $2800 yearly in utility bills. If i spend $5000 in a solar installation, and this reduce my utility bill to $1000 a year, i am getting my money back after 3 1/2 years.
$2,800 yearly utility bills x 5 years=$14,000
$5,000 in the solar power equipment and installation and $5,000 of $1000 bills a year for 5 years Total $10,000 in 5 years.
There are many variants that have to be taking in consideration here, and i don`t know many of them, just beginning with all of this. But many of you doing solar for 10 years or more should known better. In a southern state like CA, AZ, NM, TX or FL, solar power should be cheaper than the local utility company.
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Thanks Hedges, your comments are very helpful, how far can i go with 8 370W panels? Can i do a install that can be grid tie with net mettering but at the same time can be disconnected from the grid in case of a emergency like off-grid?
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Hedges
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Before you buy panels, select the inverter they will work with and plan how the panels will be connected (series & parallel) to fit the voltage and current requirements of the inverter. Maybe you want 8 (4s2p), maybe 9 (3s3p) or some other optimum arrangement. Then buy a spare or two in case you break one. Shipping is more expensive than a panel.
"8, 370W panels" sounds like $1300 to me:
https://store.santansolar.com/product-category/solar-panels/
Grid tie net metering may still be advantageous. It depends on how much the utility has messed up rates to shift it in their favor. It is possible to install solar power, reduce your consumption, and have your bill go up. You need to understand what new rates (and time of use schedule) will be imposed.
I think I can install a 5000W PV system for about $5000. That does take me quite a few hours work. I don't know what prices you can find for someone else installing.
There are some brands of inverters which support grid-tie net metering and battery backup. I think SolArk is one several people here have used. Member SolarQueen who works for Alt Energy Store does designs for people, and can sell you complete plans if you need that for permitting.
There are some alternatives, inverters that do grid-tie and batteryless backup. Not sure, but SolArk may be batteries optional.
Sunny Boy is a grid-tie inverter that provides up to 2000W (given enough PV and sun) of batteryless backup, a feature called "Secure Power". For a time, that feature was disabled if your system had "Rapid Shutdown" as required by code in many areas, but I think they've found a way to make it work now.
My system is (older) Sunny Boy with (expensive) Sunny Island battery inverters. It makes a very nice on-grid/off-grid system but probably costs $10k and up.
"8, 370W panels" sounds like $1300 to me:
https://store.santansolar.com/product-category/solar-panels/
Grid tie net metering may still be advantageous. It depends on how much the utility has messed up rates to shift it in their favor. It is possible to install solar power, reduce your consumption, and have your bill go up. You need to understand what new rates (and time of use schedule) will be imposed.
I think I can install a 5000W PV system for about $5000. That does take me quite a few hours work. I don't know what prices you can find for someone else installing.
There are some brands of inverters which support grid-tie net metering and battery backup. I think SolArk is one several people here have used. Member SolarQueen who works for Alt Energy Store does designs for people, and can sell you complete plans if you need that for permitting.
There are some alternatives, inverters that do grid-tie and batteryless backup. Not sure, but SolArk may be batteries optional.
Sunny Boy is a grid-tie inverter that provides up to 2000W (given enough PV and sun) of batteryless backup, a feature called "Secure Power". For a time, that feature was disabled if your system had "Rapid Shutdown" as required by code in many areas, but I think they've found a way to make it work now.
My system is (older) Sunny Boy with (expensive) Sunny Island battery inverters. It makes a very nice on-grid/off-grid system but probably costs $10k and up.
i am beginning to understand as my research gets more extensive. For what i can see, in the place that i live a 370 watt panel will not produce more than 1400 watt per day(in ideal condition), so i will need like 20 to cover my daily power needs, not gonna happen, BUT if i got my installation tie to the grid, i can use the grid for half of my needs reducing my electrical bill and at the same time having a backup for times of need, and that to me is worth it!
Hedges
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First order of business it to find out what net metering rates/rules are.
Then see what regulations apply (Rapid Shutdown, walkways on roof for firemen, etc.)
If Rapid Shutdown is required, it is a box per PV panel (or possibly box per 4 PV panels) and a remote control that isolates all panels so wires are a safe voltage. Not all areas require it. If panels are not on the house then not required.
Read about ArthurEld's SolArk install:
diysolarforum.com
Then see what regulations apply (Rapid Shutdown, walkways on roof for firemen, etc.)
If Rapid Shutdown is required, it is a box per PV panel (or possibly box per 4 PV panels) and a remote control that isolates all panels so wires are a safe voltage. Not all areas require it. If panels are not on the house then not required.
Read about ArthurEld's SolArk install:
10K PV and Solark Install
I got the Cadweld kit and did it today. I have an inspection tomorrow. It's ugly but the original wasn't anything to look at either. I'll put a plastic pipe over it. And I have broken pavers to arrange around it. The orange wire is cable and it's not connected to the ground rod. The cable...
diysolarforum.com
Thanks Hedges, i will have to study the whole thing and research prices a little bit more. Seeing that i want to mount the solar panels on the floor, (so to be able to dismount them and getting them secure in case of a hurricane) i only got space (sun oriented) for like 10 of them, got a lot of cypress trees in my property.
i will have to go with the biggest capacity panels i could afford (around 370-400 watts i think they are) and for what my research have let me know, 48V is the way to go, so the inverter will be 48V-110.
Hedges
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Is that price per individual cell, or for a 12V pack of four?
I haven't bought any, but many on the forum buy LiFePO4 cells and assemble batteries. There are a couple of vendors people here recommend, while others are unknown or people report bad experiences.
An assembled battery will have questionable BMS and wiring (except for a couple premium priced brands.) A BMS protects cells against over/under charge, hopefully prevents charging below freezing, and provides some amount of balancing but only among the cells it controls.
A 48V system is good for any but the smallest (e.g. < 2kW) inverter. For a 48V system, best to use a 16s bms so all cells balanced together. If you use 4, 12V batteries with their own BMS they may get out of balance, you might periodically charge separately.
A system can have BMS that doesn't communicate with inverter, but best system will have them talk. That way, charge can slow down and wait for balancing to occur.
It all depends on the capacity, performance, quality, price you want. At first you were looking for $1000 backup for fridge, then $5000 system that offsets utility bill. Hope you plan to stay connected for several years, ideally a decade, to get your money's worth. Grid-tie has quicker payback, but battery backup costs more without giving any more watt-hours.
For battery backup, you need to understand your loads: watt-hour, maximum load, starting surge.
First examine your electric bills, determine average Wh/day in winter and summer.
Read your electric meter just before sun goes down (or stops shining on your planned panel location) and in the morning before it will start producing power.
Identify largest motor to be run.
Some people buy a kill-a-watt meter to measure appliances.
Motors draw about 5x their nameplate rating to start, so a window air conditioner rated 500W needs 2500W for a second to start.
Refrigerators have a smaller motor; most of the current draw is defroster.
Your inverter rating has to be sufficient to start the loads.
Battery capacity has to be sufficient to make it through the night.
My AGM battery which cost $5000 is barely enough to get through one night. A different house with one newer refrigerator might use half as much. A sufficient size DIY LiFePO4 might be $2000 for 48V or $1200 for 24V.
From the figures you've given so far, 20 x 1400 Wh = 28 kWh is your daily consumption.
One night could be 14 kWh, hopefully less.
Your PV system will be 8 x 1400 Wh/day = 11.2 kWh, plan for 5 kWh at night
People here buy LiFePO4 280 Ah cells for about $100 or so, 900 Wh each.
A 24V 8s pack would be 7.2 kWh, cost about $1200 with BMS. That should last one night if you cut consumption when running on PV.
Doing a 48V 16s pack would let the house run one night at full consumption, but you don't plan enough PV to recharge in one day or run the house.
A generator (and suitable generator input to inverter) could work, if inverter tolerates frequency of generator.
Lithium batteries should handle nightly 80% cycles for a decade, but backup application won't make use of that. If you have time of use rates and PV smaller than total household consumption, you may find you are still a net consumer during peak times. "Peak shifting", using batteries to store power when produced and provide power during peak times so you don't draw from the grid, may be a cost-effective application of the batteries. I think DIY LiFePO4 can cost $0.05/kWh (over a decade) and utility rates could charge $0.20/kWh premium for peak hours; depends on local rates. The right inverter can be programmed to shift peaks. That's something Tesla Power Wall and SMA Sunny Boy Storage do. I think some of the low-priced inverters do to but not sure which ones.
You won't be able to run an AC overnight with a $1000 battery bank. When the sunsets/night, what really matters is the amount of energy/stored in your battery bank. A small 5000BTU window AC uses around 500w every hour. Battery technology is not ready for heavy demanding power hungry appliances like AC without breaking the bank. You would need a generator or car alternator to constantly provide 40Ah to 50Ah draw that a small 5000BTU needs. That is too much for two 100Ah batteries to handle for 8-12 hours of night time.
I suggest you get some DC fans and DC cigarette adapter to power the DC fan directly from your battery. Using AC fans with DC-AC inverters would reduce your available battery bank.
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Wow, couldn`t ask for more detailed info even to my brother. Thanks Hedges, you make things clear to understand and right to the point, very valuable info indeed. I haven`t decided which way to go, if finally i decide to go big, i know for sure that seeing that i am only able to use 10PV, the installation will need to be grid tie.
In that case, i will have to install a disconnector from the grid (you spoke about one above) that somehow will permit the installation to be used in time of emergency off grid with batteries. Also at that moment, because my short capacity of solar recharging, the generator will have to be linkup to the system to recharge the battery bank to the fullest from time to time.
There are many components needed in order to achieve that installation that i still don`t know much about them, i keep researching and learning. Very happy about the idea of been able to build my own lifepo4 banks for that amount of money. Will appreciate if you point me to the websites with the info and prices.
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