…… Solar-Electric Power Generation System Sizing tool?

Tristan

Tristan

Has No Life - Lives on TB
There's lots of big brains with experience on this forum so I thought I'd ask: anyone have a link to a good solar sizing tool/model, whether web based or app, that isn't a funnel to a company or companies wanting to bid the job?

The tools I've found so far are either far too vague and lacking detail or a direct "Get your info and send the sales team to you" type funnels.

There surely is something out there.

I'll keep looking, but if any of y'all have a clue and are willing to share, it'd be much appreciated.


Thanks in advance!
 
ShadowMan

ShadowMan

Designated Grumpy Old Fart
First off you need to assess what your current needs are?

  • How much juice are you currently using?
  • Look at your last year or two of electrical usage, through EVERY SEASON.
  • How many days of sunshine a year do you average?
  • How many days of continuous overcast or cloudy days a year do you average?
  • What's the longest period of time you've gone without direct sunshine?
  • Are you considering a stand alone or intertied to the grid. Will you be using the "grid" as your battery or will you have your own battery bank?
  • How much/many "ghost" energy using appliances do you have and what is their draw?
 
Tristan

Tristan

Has No Life - Lives on TB
Clarify? I thought the op was fairly clear: I am looking for a software tool where I can calculate the needs of a whole-house solar energy system given my particulars... The tools I've located so far are limited to the extreme and generally merely a sales funnel. I know it's out there somewhere, just haven't found it yet.

Even the state's website that purports to aid ended up being, let's say, far less than useful. And damned slow.

My goal is to determine if such a thing is even feasible.

I have a source for the components, I just need to calculate the number of each and configure.

Standard suburban home, central AC/Heat, electric range, fridge, etc, etc. I can find the specs on the various appliances, but I don't have access to a full year data on usage via the local power company. I can guestimate / interpolate and add a buffer if necessary.

Grid tie/non grid tie is an interesting question, interesting in the Chinese curse way. If I'm reading it right, I could do a hybrid system, one that is grid tied but also will function in case the grid goes down - but there are a lot more hoops to jump through. A lot more. So considering the options.
And of course, I may be reading it wrong.

Not interested in a grid-tie only system.


I appreciate all the other notations, but those bits I'm familiar with - just need the damn spreadsheet or website that ain't trying to sell my info to a contractor, and outputs a reasonably accurate model.

Thanks in advance, once again.
 
West

West

Senior
Your going to need to be more specific on the HVAC. Is it a gas heat with electric AC, or heat pump or electric heater. If so what's the KW of your electric furnace.

And what tonnage is the AC or heat pump. Usually there sized to the size of the house, but if the house is mostly glass and high ceilings.

Rule of thumb is for every 500 square feet of condition floor space is a ton of AC or heat pump, but still need to know the KW of the electric furnace if that's what you have.

Good luck.
 
Knoxville's Joker

Knoxville's Joker

Has No Life - Lives on TB
Tristan said:
Clarify? I thought the op was fairly clear: I am looking for a software tool where I can calculate the needs of a whole-house solar energy system given my particulars... The tools I've located so far are limited to the extreme and generally merely a sales funnel. I know it's out there somewhere, just haven't found it yet.

Even the state's website that purports to aid ended up being, let's say, far less than useful. And damned slow.

My goal is to determine if such a thing is even feasible.

I have a source for the components, I just need to calculate the number of each and configure.

Standard suburban home, central AC/Heat, electric range, fridge, etc, etc. I can find the specs on the various appliances, but I don't have access to a full year data on usage via the local power company. I can guestimate / interpolate and add a buffer if necessary.

Grid tie/non grid tie is an interesting question, interesting in the Chinese curse way. If I'm reading it right, I could do a hybrid system, one that is grid tied but also will function in case the grid goes down - but there are a lot more hoops to jump through. A lot more. So considering the options.
And of course, I may be reading it wrong.

Not interested in a grid-tie only system.


I appreciate all the other notations, but those bits I'm familiar with - just need the damn spreadsheet or website that ain't trying to sell my info to a contractor, and outputs a reasonably accurate model.

Thanks in advance, once again.
Click to expand...
Sadly I do not think you will find it. Most homes need a 20-30k solar setup to power. Just take your last power bill and calculate from there.
 
Millwright

Millwright

Knuckle Dragger
_______________
It's kinda like, "how big is a car?"

Most find it prohibitively expensive to maintain their current/normal power usage via solar.

Once you figure out your current usage and price that, then you will be working the deal from the other end....what is the bare minimum?

There are a coupla forums on alternative power, they have sections for newbies that answer a lot of the questions for people just starting out.

IIRC, Arizona Wind and Power or maybe Solar is a good one.
 
Sebastian

Sebastian

Sebastian
Remember you can tie certain needs to your solar system one at a time (needs a subpanel). Our master bathroom circuit is now on solar power. If that is inadequate then the grid takes over. As we expand the system we will tie more circuits to the solar. Also we charge the Nissan Leaf on the system most of the time (I am my own "gas station") along with a freezer and dehumidifier in the basement. The goal being that everything but the central air and electric stove will be sun powered. You can learn as you go along we are moving essential loads to the solar as the power company becomes less and less reliable.
 
Capt. Eddie

Capt. Eddie

Veteran Member
This one is Sol-Ark specific (panel and string calculator)

This one is the NREL calculator for what kind of output you can expect from a given size array, mount style, and orientation at your specific location (its been very accurate for our system so far)

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations
pvwatts.nrel.gov pvwatts.nrel.gov
 
Capt. Eddie

Capt. Eddie

Veteran Member
Tristan said:
If I'm reading it right, I could do a hybrid system, one that is grid tied but also will function in case the grid goes down - but there are a lot more hoops to jump through. A lot more. So considering the options.
Click to expand...
Yes you can and (depending on your power company) yes there are. Took me a little over ten months from start to finish. It was well worth jumping through the hoops in the end though.
 
West

West

Senior
The first and only thing I got working off of solar is our good well. Besides a bunch of solar security lights.

Plan to do much more and have a good start with deep cells, panels, turbines, wire, fuses, diodes, controllers. Etc....

Current business is busy. Then honey do's, etc...

OP, if your a bit busy may want to start and concentrate on getting off the grid water.
 
bbbuddy

bbbuddy

DEPLORABLE ME
In a typical suburban house?? What are you willing to give up/do without? Are there kids involved or just you and the missus? Hobbies that need electricity?
Do you already cook/heat with gas?

These things are all very impactful. Cutting back electric needs saves a lot of $$.
When you know what you absolutely NEED and WANT then you can start sizing.

Unless of course money is no object, lol.

If off grid, you have to want to manage your own "grid" and many people either dont want to or simply can't.

I highly recommend NAZ Solar Electric Forum
Many experts there, many people willing to help.

I built my system for under $ 10,000. Have added to it since then. Learned it all at that forum.

We have two freezers, a washer and dryer, window ac, and well pump.

We pretty much live like anyone else, except that we need to manage what runs, and when.
 
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Capt. Eddie

Capt. Eddie

Veteran Member
bbbuddy said:
What are you willing to give up/do without? Are there kids involved or just you and the missus? Hobbies that need electricity?
Click to expand...
That's why we went hybrid, you don't have to give up the luxuries, you just still have to pay the electric bill for them. If the grid goes down or some personal SHTF occurs (job loss, medical, etc..) you just turn off the luxuries.
 
S

shane

Has No Life - Lives on TB
I always tell anyone interested in going solar to first expend time, money & energy better insulating and also reducing all current electrical loads by either upgrading to more efficient units or replacing outright with non electrical alternatives.

BTW, two outfits that I’ve had great deals via are;

World's Lowest Solar Panel Prices » Sun Electronics International, Inc

New and used solar panels, inverters, charge controllers, complete solar system kits at wholesale prices. We have best prices in solar panels.
sunelec.com sunelec.com

SignatureSolar.com: Solar Panels, DIY Off-Grid Solar, Server Rack Battery for Solar, Solar Inverters

Signature Solar provides solar panels & components and full kits for off-grid, grid-tie and custom diy solar systems. Providing Solar 101 and hands on experience within the solar industry. Quality inverters, bifacial solar panels, complete solar kits, solar batteries. Holding best in class...
signaturesolar.com signaturesolar.com

Panic Early, Beat the Rush!
-Shane
 
WFK

WFK

Senior Something
I don't know if there is a tool that encompasses all desired power replacement or substitutions by solar power.
Most people shudder when they want to do a full replacement without OTHER changes. Then they change their goal.

But full replacement is a START, so find your 12-month power bills and study the kWh use by season, by month, by day.
That will give you AVERAGES. Then study possible PEAK demands.
After you realize that the power company supplies those demands ALWAYS, you do a time study of what you can count on delivered from solar in AVERAGE and PEAK form. That is when you find that the the meaning of a Solar panel OUTPUT is not what you originally assumed. Only after you reconcile your ACTUAL replacement power in terms of Power and Duration can you even begin to size. You want a spreadsheet? No such thing.

So you have to do all that in kiloWatts and kiloWattHours, before you ever get to cost and hardware.
A not minor point may be the limited space available to put up as many solar panels as you want or need on your property or home.
Aside from the panel issue there is the question of how much time you want to bridge when there is no solar power available? Batteries? You do the average and peak power demand again for THOSE conditions! The point is that solar is intermittent power and the battery cost and sizing effort is rarely mentioned.

So before you can use a TOOL you must define your goal.
 
S

SackLunch

Dirt roads take me home
We went to Harbor Freight and bought a Kil-O-Watt, plugged it into everything that used electricity and built a spreadsheet. Very educational.

A 1500 microwave for 20 min a day during mostly sunshine hours should be considered differently than a "base" load item like refrigerator that runs day and night requiring battery storage.
 
LoupGarou

LoupGarou

Ancient Fuzzball
As WFK said, there probably will never be a spreadsheet that will cover all the bases.

My suggestion, and what I tell others here in CVA to do to get started it think about what you really want to power. IF that is your whole house, then (as others have said) take your last year or two years worth of power bills, find the average KHW per MONTH, as well as the largest KWH per DAY, and write those down. Now you know the load that you need to power, both max and average.

Batteries are NOTHING more than "gas tanks" for electrons, so in reality they are one of the last things that you need to worry about on the sizing of a system, because you can have a wicked large gas tank on a car, if you can't fill it any faster than an eyedropper full at a time, don't expect to get across the country very fast, and when you do run out of fuel expect to be sitting (in the dark) for a while. So once you know your average KWH per month power and your daily max KWH for any day during that month, you need to concentrate on your power input to the system first...

If your house needs 24KWH per day on average (about 2KWH per hour on average), but has days where you may need 48KHW per day, you need to have the ability of inputting at least 48KWH per sunshine cycle unless you plan on having your batteries not get topped up for a day or two (dangerous area to be in if you have cloudy days, just sayin'). If your max and your average are closer together, then you can scale that down quite a bit, OR if you can "do without" those large loads in most times, then you can scale it back to closer to your average 24KWH per day amount. Now, that is 24KWH being developed in the amount of time you have good strong sun, not over 24Hours per day. So, if you have say, 6 hours of good strong sun per day that can hit your panels, then you need to have that many solar panels to create 24KWH in those 6 hours (or 4,000W of solar panels (say, 40X 100Watt panels)). If you have only 4hours of good strong sun a day, then you are looking at needing 6,000W of solar panels (6,000 watts for 4 hours), and that is still saying you have good sun every day. If you have clouds every other day (so you have good strong sun 50% of the time, then you need to double your solar panel input to make up for that, meaning 12KW of panels for a 4 hour day every other day. It gets expensive and VERY large if actually trying to power your whole house. The companies that tell you that they can do grid tie on your roof and power everything you want plus get you a check back from the power company are lying to you for almost any home out there unless you have a very large roof, and VERY small loads (no AC, no heat or hot water, no electric stove...)

My suggestion, is post your monthly KWH (and the highest daily KHW per month) specs from your bills and we can run through the math here on this thread. That is the only way you are going to see the actual numbers of what you need to generate, as well as what you need to be able to store. You will also need to post the average amount of direct, strong, sun you get per day in hours. And do you have clouds every other day, or every third, fourth? OR do you have good strong sun every third, fourth, or longer days?. Also, what happens on your property to the sun's path during winter and during summer? Do trees (or anything else) block the sun's path to get to where you want to put the panels at anytime during the year to cut down on that daily number of hours per day?

This will give you enough info to start looking at what it would take to power your whole home.
 
LoupGarou

LoupGarou

Ancient Fuzzball
SackLunch said:
We went to Harbor Freight and bought a Kil-O-Watt, plugged it into everything that used electricity and built a spreadsheet. Very educational.

A 1500 microwave for 20 min a day during mostly sunshine hours should be considered differently than a "base" load item like refrigerator that runs day and night requiring battery storage.
Click to expand...

Another good suggestion, especially if someone only wants to power a few devices around the house in the case of a power outage. Let the Kill-o-Watt run for a month, get the instantaneous wattage off of the Kill-o-Watt meter, and then get both the KHW used, as well as the number of hours that the meter has run, and divide the KHW used by the hours to get the average HWH usage of the device. The instantaneous wattage is what you inverter is going to have to supply constantly as a minimum to keep the device running (for most devices there will be a larger startup power needed, and the inverter will need to be able to cover that as well for a second or two). The average KHW power usage is what you are going to need to be able to supply from your panels, as well as have enough extra to recharge your batteries while still running your device(s).

And yes, since most devices like microwaves, refrigerators and freezers don't actually "run" continuously, but cycle on and off (called "Duty Cycle") either by itself (like the fridge and freezer), or by user demands like my kids hitting the "popcorn" button on the nuker, that Duty Cycle also needs to be remembered and somewhat factored in to give your system extra overhead in grace, but also to bring the size of the panel setup down a bit. If you have a fridge that takes 100 watts when running, unless you have a lot of kids that leave the door open often, it won't (hopefully) take that 24 hours a day for 2.4KHW per day, but something closer to .5WKH per day or less. Duty Cycle is a great thing, just don't plan on being able to drop your system specs TOO low as duty cycle on a lot of things can change for all sorts of reasons (device gets older and less efficient, kids leave the door open, heat in the room increases and the fridge or freezer has to run longer per hour to compensate). Personally, I like to keep the Duty Cycle part in the back of my head and NOT implement is too much in the planning and system spec design, but instead have it cover as an extra overage so that cloudy days or other bad news don't kick you hard later on.
 
Knoxville's Joker

Knoxville's Joker

Has No Life - Lives on TB
SackLunch said:
We went to Harbor Freight and bought a Kil-O-Watt, plugged it into everything that used electricity and built a spreadsheet. Very educational.

A 1500 microwave for 20 min a day during mostly sunshine hours should be considered differently than a "base" load item like refrigerator that runs day and night requiring battery storage.
Click to expand...
And change cooking to during daytime only…
 
Knoxville's Joker

Knoxville's Joker

Has No Life - Lives on TB
And i was looking at having some smaller systems that totaled to a larger system. One for the shed, one for the well house, another for the home electronics. Doing things that way ensures i can cash flow the whole thing
 
WFK

WFK

Senior Something
My advice: start small! Characterize you refrigerator and size a solar system for it alone.
Panels, inverter, battery. Then try it out! That will be your best preparation to define your goal.

The refrigerator is really neat because you have a compressor intermittently running (and STARTING!)
And if it's "frost-free" you have an intermittent heater too.
 
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Txkstew

Txkstew

Veteran Member
I've always wanted to get some kind of solar power going here at my house, but other priorities have always taken over. Lately, I've had that inner voice telling me to get at least a minimal system for my Cpap machine and run some fans in an extended power outage. Maybe my small refrigerator and 5000 btu window unit in my bedroom. From the YouTube videos I've been watching, this should be doable with what I have planned.

The plan is to eventually put 4 - 100 W solar panels on top of my metal carport. It's 20' x 20' and mostly flat, so room for more panels in the future. It has a Southern exposure that's sunny most of the day. I probably will have to take down a few junk trees for Winter sun. I'll be buying 4 - 100 AH batteries to start.

Well, money for me is tight nowadays. So I'm starting slow, plus I've sold some things. Harbor Freight actually has some 100 watt monocrystalline panels that have some good reviews. I got one with a 15 % off coupon, for $107 after tax. There's cheaper ones out there. I bought one, 100 AH Lithium battery for $292 delivered, a HQST 40 amp MTTP charge controller for $109, a DC breaker and box. I have a 3000 W Renogy Inverter on the way Friday, for $342 delivered. I may have to up size some things in the future.

I'm converting the SAE wire connectors on the panels to the more common ME4 snap connectors. I ordered some Y conectors and a 25' fused extension cable, a crimping tool with a ring wire connector kit. Next is to buy another battery and panel. I'll need to get some #2 awg wire to power the inverter, and jumper the batteries together. I'm broke for now unless I go sell something else.

All this is going to be mounted in my walk-in closet.

Any comments from more experienced Solar folks here will be welcome. I've done Instrument and Electrical system design in Refineries for 35 years now, but this solar stuff is new to me. YouTube is full of people doing what I have planned, for home and RV installs. Whole house is not something I plan on doing. One guy said whole house systems take 20 years to break even on the equipment.
 
LoupGarou

LoupGarou

Ancient Fuzzball
Txkstew said:
I've always wanted to get some kind of solar power going here at my house, but other priorities have always taken over. Lately, I've had that inner voice telling me to get at least a minimal system for my Cpap machine and run some fans in an extended power outage. Maybe my small refrigerator and 5000 btu window unit in my bedroom. From the YouTube videos I've been watching, this should be doable with what I have planned.

...

Well, money for me is tight nowadays. So I'm starting slow, plus I've sold some things. Harbor Freight actually has some 100 watt monocrystalline panels that have some good reviews. I got one with a 15 % off coupon, for $107 after tax. There's cheaper ones out there. I bought one, 100 AH Lithium battery for $292 delivered, a HQST 40 amp MTTP charge controller for $109, a DC breaker and box. I have a 3000 W Renogy Inverter on the way Friday, for $342 delivered. I may have to up size some things in the future.

I'm converting the SAE wire connectors on the panels to the more common ME4 snap connectors. I ordered some Y conectors and a 25' fused extension cable, a crimping tool with a ring wire connector kit. Next is to buy another battery and panel. I'll need to get some #2 awg wire to power the inverter, and jumper the batteries together. I'm broke for now unless I go sell something else.
...
Click to expand...
Pull a list of the different things you want to run, get the wattage, or the amperage of each device. The 3000W inverter will run a lot of them, one or two items at a time. BUT, your input wiring at even 1500W output is going to need to be bigger than 2AWG, which is really rated for 115 amps MAX, which would only give you 1,380W max (If everything else was 100% efficient). Once you factor in losses and other issues, even 2/0 gauge wire may not be enough to cover 1500W with starting current overages. 2/0 is rated for 175 amps MAX, or about 2100W (175A*12V). For most of my 3000 to 5000W inverters, I go with doubled 4/0 copper wire (or multiple bind several 2/0 cables in parallel to get what I need) for short (less than 6 feet) runs, and either 350MCM or 500MCM copper cabling for the 10-15 foot runs.

A single LiFePO4 100AH*12V battery will have around 1000WH of usable power (even less if you draw it out quicker, and more if you draw it out slower (as in 60W over 20 hours). Everything on the load side is just the watts it needs times the hours that it will be on to get the what hours that you need to have battery capacity for. The fan that takes 50 watts, if run just an hour, only takes about 50 WH, but run for a whole day takes 1200WH, or the total capacity of one of the 100AH batteries. Likewise, the 1000W microwave oven running just a minute to heat your coffee up in the morning only takes a whopping 16.7WH to do that (1000W*(1/60)H).

Now, the other half of the equation is how much is going to be needed to fill that 100AH "electron tank" back up? Not sure what the specs are on the 100W panel, but I'm betting that you are looking at around 5.8 amps at around 18 volts output on the one panel. IF the MPPT works well with that single panel, then you should be able to get somewhere near 7A at the needed 14.2-14.4Volts that the LiFePO4 battery want to charge at. If the battery is 100AH, and the charge rate is 7A you can quickly find the needed hours of full sun to be able to charge the battery back up with 100AH/7A=14.29Hours, or a little more than two days worth of sun, so you could not charge the emptied out battery back to full in one day with one panel. 2 of those panels in series would get you down to 7 hours to fill the 100AH battery (the HQST 40 amp MTTP charge controller will handle up to 100V input from the panels, which will let you series connect up to 4 panels in series to get you past 80 volts but below 100 volts of solar power to the MPPT charge controller). If you had 4 panels in series, you would be able to charge the 100AH battery up in about 3.5 hours. So for every 100AH of batter bank capacity you have, you need 4 of those solar panels and one those MPPT charge controllers (They have a max of 600W capacity at 12V). This means that you will have 16 panels, 4 MPPT charge controllers, and 4X 100AH batteries that all need 3.5 hours of sun or more per day minimum to guarantee a full recharge.

Here is where load choices help out, as a watt you don't use, is one that you don't have to generate. If you stay with just one battery, and 4 panels, you are looking at having a stored supply of about 1000-1200WH. If you have 4 batteries, and 16 panels, you are looking at 4000-4800WH of stored power.

The 5000BTU AC, may take 11-13Amps at 115V, or 1265-1495W for as long as it is on. Running it for just 8 hours is going to need anywhere between 5060WH to 11,960WH (1265 * 4 (if the AC is only on half the time cycling on and off), versus on constantly on a really hot day for 8 hours at 1495W)... Either way that would be a load you might not be able to afford for 8 hours.

The math here on the load side is important, as it will give you a better idea on what you can and can't power with what you may have coming in from the sun, as well as what you have as far as storage.

How much does the CPAP machine take? How about the CPAP with the air warmer? How long per night do you plan on running it? IF you are looking at the CPAP taking 75W without the heater, and 140 with the heater, then a 8 hour night would pull either 600WH or 1,120WH from the battery. Running the heated CPAP may not leave you with much left for other loads on a single battery...

You can work through the other load the same way. Watts used, hours that the device is running and it's Duty Cycle (does it actually run 100% of the time when it is on, or say 50% of the time with half the time pulling XXXX watts and the other half of the time pulling next to nothing...
 
S

SciFi Lover

Member
I just did a quick scan of the message strings here. What I don't see mentioned is "what will your Grid supplier let you install"? Do you have a limit from them? In Michigan you sure do. If they won't let you connect your system, well, your complexity just went way up. Additionally, what you put in for panels by wattage will probably NOT produce that level of power even when brand new. Mine, a 7.8 kW system has never produced over 7 kW's. So plan on production limits, then think of degradation over time as each year you will produce less.

If you cannot push excess power to the grid, where are you going to put it? If you have batteries, yes, they can take some. Where does it go when they get full? Sure, people will tell you the electronics will cycle the panels on and off. No, I don't believe them. The hits to the system, both inverter and batteries, as the system tries to compensate for this condition, driven by clouds and intermittent home loads are frankly nasty. You need a place to put the excess power if you have any. So your grid suppliers requirements are a key starting place.

Point of information. Michigan will tell you you cannot generate more power (annual) than your last annual kWh's total. You can argue with them on this IF you have battery storage. I got approved for more solar than my annual total, wish I had gone for more!

The comments on examining your annual historic power usage are directionaly correct. These values give you your boundary usage conditions unless you are going to change something. Unless you are going to go crazy with storage or plan to totally change your lifestyle I fail to see how you are going to live on solar power in the winter. Here in Michigan last winter I generated almost zero power in January. No reasonable battery bank is going to carry a month or more of power.

So look at your power usage by month for the last couple of years, figure out what power usage you can cut out via efficiency gains or total elimination. Calculate what you need in solar generation to replace that power, allowing for at least (my opinion) 20% overage on new panels by design. Storage will be impacted by any number of things including battery chemistry selected, storage temperature and duty cycle. You will have to do your own research here and get trained up. No, there is no good single repository of wisdom that I have found in this area. Just info scattered all over.

There are a couple of good solar strings on the forum. Search them out as they have a lot of practical information on system design in them.
 
Txkstew

Txkstew

Veteran Member
LoupGarou said:
Pull a list of the different things you want to run, get the wattage, or the amperage of each device. The 3000W inverter will run a lot of them, one or two items at a time. BUT, your input wiring at even 1500W output is going to need to be bigger than 2AWG, which is really rated for 115 amps MAX, which would only give you 1,380W max (If everything else was 100% efficient). Once you factor in losses and other issues, even 2/0 gauge wire may not be enough to cover 1500W with starting current overages. 2/0 is rated for 175 amps MAX, or about 2100W (175A*12V). For most of my 3000 to 5000W inverters, I go with doubled 4/0 copper wire (or multiple bind several 2/0 cables in parallel to get what I need) for short (less than 6 feet) runs, and either 350MCM or 500MCM copper cabling for the 10-15 foot runs.

A single LiFePO4 100AH*12V battery will have around 1000WH of usable power (even less if you draw it out quicker, and more if you draw it out slower (as in 60W over 20 hours). Everything on the load side is just the watts it needs times the hours that it will be on to get the what hours that you need to have battery capacity for. The fan that takes 50 watts, if run just an hour, only takes about 50 WH, but run for a whole day takes 1200WH, or the total capacity of one of the 100AH batteries. Likewise, the 1000W microwave oven running just a minute to heat your coffee up in the morning only takes a whopping 16.7WH to do that (1000W*(1/60)H).

Now, the other half of the equation is how much is going to be needed to fill that 100AH "electron tank" back up? Not sure what the specs are on the 100W panel, but I'm betting that you are looking at around 5.8 amps at around 18 volts output on the one panel. IF the MPPT works well with that single panel, then you should be able to get somewhere near 7A at the needed 14.2-14.4Volts that the LiFePO4 battery want to charge at. If the battery is 100AH, and the charge rate is 7A you can quickly find the needed hours of full sun to be able to charge the battery back up with 100AH/7A=14.29Hours, or a little more than two days worth of sun, so you could not charge the emptied out battery back to full in one day with one panel. 2 of those panels in series would get you down to 7 hours to fill the 100AH battery (the HQST 40 amp MTTP charge controller will handle up to 100V input from the panels, which will let you series connect up to 4 panels in series to get you past 80 volts but below 100 volts of solar power to the MPPT charge controller). If you had 4 panels in series, you would be able to charge the 100AH battery up in about 3.5 hours. So for every 100AH of batter bank capacity you have, you need 4 of those solar panels and one those MPPT charge controllers (They have a max of 600W capacity at 12V). This means that you will have 16 panels, 4 MPPT charge controllers, and 4X 100AH batteries that all need 3.5 hours of sun or more per day minimum to guarantee a full recharge.

Here is where load choices help out, as a watt you don't use, is one that you don't have to generate. If you stay with just one battery, and 4 panels, you are looking at having a stored supply of about 1000-1200WH. If you have 4 batteries, and 16 panels, you are looking at 4000-4800WH of stored power.

The 5000BTU AC, may take 11-13Amps at 115V, or 1265-1495W for as long as it is on. Running it for just 8 hours is going to need anywhere between 5060WH to 11,960WH (1265 * 4 (if the AC is only on half the time cycling on and off), versus on constantly on a really hot day for 8 hours at 1495W)... Either way that would be a load you might not be able to afford for 8 hours.

The math here on the load side is important, as it will give you a better idea on what you can and can't power with what you may have coming in from the sun, as well as what you have as far as storage.

How much does the CPAP machine take? How about the CPAP with the air warmer? How long per night do you plan on running it? IF you are looking at the CPAP taking 75W without the heater, and 140 with the heater, then a 8 hour night would pull either 600WH or 1,120WH from the battery. Running the heated CPAP may not leave you with much left for other loads on a single battery...

You can work through the other load the same way. Watts used, hours that the device is running and it's Duty Cycle (does it actually run 100% of the time when it is on, or say 50% of the time with half the time pulling XXXX watts and the other half of the time pulling next to nothing...
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Thanks for your input Loup. I'll explain my most important power needs in an extended grid down situation. Number one is my Cpap machine. Since starting on therapy, I've only gone a couple of nights where I went to sleep normally and didn't have Grid power. It's a horrible feeling of suffocating as you fall asleep. I keep waking up gasping for air. So I'd say that's a pretty big issue in a prolonged event. Losing weight might be a real good idea in the long run, but in that situation might not be an option.

Now let's say I have my system installed with 4 - 100 AH Lithium batteries, 4 - 100w panels, the 40A controller, and 3000w inverter, all with proper sized wire.

Certainly my Cpap machine that uses 6.67 amps at 12vdc (it has a transformer on the power cord) would be covered for many days by its self. I don't use the heated humidifier. Am I right that 6.67 amps x 12 vdc = 80 w more or less? Times 8 hours of use = 640 WH per day.

My system, fully charged, is 4800 WH, so about a week on a full charge if nothing else is powered, and it gets real cloudy and not much charging is going on. I've seen it get cloudy here for 3 weeks and no sun.

I ran my Cpap on a 55 AH agm battery at one time, directly hooked up with a 12 v adapter cord and cigarette plug. Seemed a little weak, but got the job done.

Now a fan and Cpap running at the same time would be nice if it's Summer, and here on the Gulf coast in this scenario.

The whole house high velocity fan sold at Habor Freight is rated at 164w. So for 8 hours it uses 1300 WH. With Cpap at 640, we're under 2000 WH for 8 hours. Doesn't leave much for the other 16 hours. And that's at peak efficiency and conditions.

Gonna need a bigger boat.
 
WFK

WFK

Senior Something
Txkstew said:
Thanks for your input Loup. I'll explain my most important power needs in an extended grid down situation. Number one is my Cpap machine. Since starting on therapy, I've only gone a couple of nights where I went to sleep normally and didn't have Grid power. It's a horrible feeling of suffocating as you fall asleep. I keep waking up gasping for air. So I'd say that's a pretty big issue in a prolonged event. Losing weight might be a real good idea in the long run, but in that situation might not be an option.

Now let's say I have my system installed with 4 - 100 AH Lithium batteries, 4 - 100w panels, the 40A controller, and 3000w inverter, all with proper sized wire.

Certainly my Cpap machine that uses 6.67 amps at 12vdc (it has a transformer on the power cord) would be covered for many days by its self. I don't use the heated humidifier. Am I right that 6.67 amps x 12 vdc = 80 w more or less? Times 8 hours of use = 640 WH per day.

My system, fully charged, is 4800 WH, so about a week on a full charge if nothing else is powered, and it gets real cloudy and not much charging is going on. I've seen it get cloudy here for 3 weeks and no sun.

I ran my Cpap on a 55 AH agm battery at one time, directly hooked up with a 12 v adapter cord and cigarette plug. Seemed a little weak, but got the job done.

Now a fan and Cpap running at the same time would be nice if it's Summer, and here on the Gulf coast in this scenario.

The whole house high velocity fan sold at Habor Freight is rated at 164w. So for 8 hours it uses 1300 WH. With Cpap at 640, we're under 2000 WH for 8 hours. Doesn't leave much for the other 16 hours. And that's at peak efficiency and conditions.

Gonna need a bigger boat.
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Tx, I have two comments:

1. look into LiFePO4 batteries; They are more expensive, but you can discharge them deeper than Lead/Acids.
Look at their discharge curves (Voltage and Current) and you see the "Wh available" advantage.

2. If you power rotating gear you must consider the load power factor (PF). Things rated in Watts demand a current of
Watts/(Volts x PF). Suddenly the actual drawn current is so much larger than calculated from Watts/Volts.

Bonus: Loup's assumption of 7 hours of RATED panel output per day is incredibly optimistic for any fixed installed panel.
 
LoupGarou

LoupGarou

Ancient Fuzzball
WFK said:
...

Bonus: Loup's assumption of 7 hours of RATED panel output per day is incredibly optimistic for any fixed installed panel.
Click to expand...
I was saying that to charge a single 100AH LiFePO4 with two of those solar panels that he would need at least 7 hours of strong sun. No guarantees that you would get that in one day, even with moveable panels, which is why I suggested 4 of those panels per 100AH battery.
 
Txkstew

Txkstew

Veteran Member
WFK said:
Tx, I have two comments:

1. look into LiFePO4 batteries; They are more expensive, but you can discharge them deeper than Lead/Acids.
Look at their discharge curves (Voltage and Current) and you see the "Wh available" advantage.

2. If you power rotating gear you must consider the load power factor (PF). Things rated in Watts demand a current of
Watts/(Volts x PF). Suddenly the actual drawn current is so much larger than calculated from Watts/Volts.

Bonus: Loup's assumption of 7 hours of RATED panel output per day is incredibly optimistic for any fixed installed panel.
Click to expand...
Yes, I'm talking about using LiFepo4 batteries. I use lithium for shorthand as it's easier to type. I got my Power Queen 100AH battery for $292 delivered. The plan is to buy a total of 4 as I can afford them. Amazon has a 100AH LiFepo4 for $229, a $12 off coupon, plus tax. Comes with a shore power charger. Cheapest I seen so far.
 
LoupGarou

LoupGarou

Ancient Fuzzball
Txkstew said:
Thanks for your input Loup. I'll explain my most important power needs in an extended grid down situation. Number one is my Cpap machine. Since starting on therapy, I've only gone a couple of nights where I went to sleep normally and didn't have Grid power. It's a horrible feeling of suffocating as you fall asleep. I keep waking up gasping for air. So I'd say that's a pretty big issue in a prolonged event. Losing weight might be a real good idea in the long run, but in that situation might not be an option.

Now let's say I have my system installed with 4 - 100 AH Lithium batteries, 4 - 100w panels, the 40A controller, and 3000w inverter, all with proper sized wire.
...
Click to expand...

Whoa, hold that thought... I said the ratio was looking at 4 panels per 100AH battery, which is why I suggested 16 panels and 4 of those MPPT charge controllers if you are looking at 4X 100AH batteries in parallel. Yes, this gets expensive, which is why I also suggested looking at your loads before spec'ing and building your system. The 16 panels could be dropped to 12, with 3 in series to each charge controller, and still decently charge the batteries in a single day with 6-7 hours of strong sun (keep in mind that you may have to move the panels a bit to keep them pointed during the 6-7 hours, which is why I usually suggest oversizing the array so that you can do it in 3-4 hours, and not have to move much.

If you are talking about the Thunderbolt solar 100 W panels, the specs show them at 6.2A MAX at 18V. Three in series would give you 54V at 6.2A Max, and 4 panels in series would give you 72V at 6.2A Max. Run through the MPPT charger, you are looking at getting 21A for 3 panels, and 28.16A for 4 panels. A single 100AH battery would need a minimum of 5 hours of strong sunlight from the three panels to get charged (21A X 5H), or a little over 3.5 hours with 4 panels (28.1A X 3.5H). Again, not having ever played with these panels, you might want to setup on set of 4 panels, one charge controller, and one LiFePO4 100AH battery and test it before quadrupling all of it to get to where you want.

Txkstew said:
...
Certainly my Cpap machine that uses 6.67 amps at 12vdc (it has a transformer on the power cord) would be covered for many days by its self. I don't use the heated humidifier. Am I right that 6.67 amps x 12 vdc = 80 w more or less? Times 8 hours of use = 640 WH per day.

My system, fully charged, is 4800 WH, so about a week on a full charge if nothing else is powered, and it gets real cloudy and not much charging is going on. I've seen it get cloudy here for 3 weeks and no sun.
...
Click to expand...
The 3 weeks of no sun may be a rather big issue. You may want to look at having a generator or another backup plan for those times as even with 400AH of battery bank goodness, your solar panels REALLY like good strong sun, and don't do hardly anything with anything less than that. You don't get 50% power with 50% sun. It's more like 10% with 50% sun.

Txkstew said:
...
I ran my Cpap on a 55 AH agm battery at one time, directly hooked up with a 12 v adapter cord and cigarette plug. Seemed a little weak, but got the job done.

Now a fan and Cpap running at the same time would be nice if it's Summer, and here on the Gulf coast in this scenario.

The whole house high velocity fan sold at Habor Freight is rated at 164w. So for 8 hours it uses 1300 WH. With Cpap at 640, we're under 2000 WH for 8 hours. Doesn't leave much for the other 16 hours. And that's at peak efficiency and conditions.

Gonna need a bigger boat.
Click to expand...
As with any of this, test all of the parts of the system NOW, along with various loads and challenges NOW while "normal" power is still available in case of things not lasting as long or charging back as fast as hoped or planned. I definitely would suggest checking how well and how fast 4 of those panels charge back the 1 battery before scaling up.

And make sure that you have a good digital volt meter on hand always, to see actual real world readings on the battery's (and the solar panel's) performance.
 
Txkstew

Txkstew

Veteran Member
LoupGarou said:
Whoa, hold that thought... I said the ratio was looking at 4 panels per 100AH battery, which is why I suggested 16 panels and 4 of those MPPT charge controllers if you are looking at 4X 100AH batteries in parallel. Yes, this gets expensive, which is why I also suggested looking at your loads before spec'ing and building your system. The 16 panels could be dropped to 12, with 3 in series to each charge controller, and still decently charge the batteries in a single day with 6-7 hours of strong sun (keep in mind that you may have to move the panels a bit to keep them pointed during the 6-7 hours, which is why I usually suggest oversizing the array so that you can do it in 3-4 hours, and not have to move much.

If you are talking about the Thunderbolt solar 100 W panels, the specs show them at 6.2A MAX at 18V. Three in series would give you 54V at 6.2A Max, and 4 panels in series would give you 72V at 6.2A Max. Run through the MPPT charger, you are looking at getting 21A for 3 panels, and 28.16A for 4 panels. A single 100AH battery would need a minimum of 5 hours of strong sunlight from the three panels to get charged (21A X 5H), or a little over 3.5 hours with 4 panels (28.1A X 3.5H). Again, not having ever played with these panels, you might want to setup on set of 4 panels, one charge controller, and one LiFePO4 100AH battery and test it before quadrupling all of it to get to where you want.


The 3 weeks of no sun may be a rather big issue. You may want to look at having a generator or another backup plan for those times as even with 400AH of battery bank goodness, your solar panels REALLY like good strong sun, and don't do hardly anything with anything less than that. You don't get 50% power with 50% sun. It's more like 10% with 50% sun.


As with any of this, test all of the parts of the system NOW, along with various loads and challenges NOW while "normal" power is still available in case of things not lasting as long or charging back as fast as hoped or planned. I definitely would suggest checking how well and how fast 4 of those panels charge back the 1 battery before scaling up.

And make sure that you have a good digital volt meter on hand always, to see actual real world readings on the battery's (and the solar panel's) performance.
Click to expand...
On YouTube, they are saying you need a shunt with a Bluetooth readout in order to see the actual charge level of a LiFepo4 battery. The Bluetooth app for my charge controller does not show actual charge level, just charge rate. Something else to buy I guess.
 
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