Costing out a small, rural solar panel installation

[Justin]

The shooting club I belong to is not connected to the grid. We've been kicking around the idea of doing a solar panel installation on the main building so that we don't have to run a generator for indoor light/electricity.

One of the guys there got an estimate for a solar panel/battery installation, and was told that it would cost around $10,000.

This cost was immediately shot down by the board of directors as excessive, as the only thing we'd be using this for is to power around 10 indoor 2-bulb light fixtures, maybe one exterior light, and maybe the ocassional laptop/tablet/smart phone. Run times wouldn't generally be very long. Most of our meetings only run about an hour or so, though a longer run time (maybe 4-5 hours?) would be nice, for those times when a visiting trainer has class time.

Given that we're not looking to run a household (no HVAC, no fridges or other appliances) I would have assumed a solar array+battery setup could be installed for around $4,000-$6,000.

Am I incorrect in my assumptions, or are even small solar+battery setups in the five figure range?

[Irving]

I'm not your expert, but I'd think you could accomplish that cheaper than quoted. Especially if someone in the club is capable of doing install themselves.

[Justin]

That's one thing I was wondering. What's the cost of the hardware vs. the cost of installation. I wouldn't be terribly surprised to find out we've got at least a couple of members capable of doing the install.

Got any good pointers on where to go to research this stuff and spec it out?

[Justin]

Also, are deep-cycle lead batteries still the go to for something like this?

[Grant H.]

The shooting club I belong to is not connected to the grid. We've been kicking around the idea of doing a solar panel installation on the main building so that we don't have to run a generator for indoor light/electricity.

One of the guys there got an estimate for a solar panel/battery installation, and was told that it would cost around $10,000.

This cost was immediately shot down by the board of directors as excessive, as the only thing we'd be using this for is to power around 10 indoor 2-bulb light fixtures, maybe one exterior light, and maybe the ocassional laptop/tablet/smart phone. Run times wouldn't generally be very long. Most of our meetings only run about an hour or so, though a longer run time (maybe 4-5 hours?) would be nice, for those times when a visiting trainer has class time.

Given that we're not looking to run a household (no HVAC, no fridges or other appliances) I would have assumed a solar array+battery setup could be installed for around $4,000-$6,000.

Am I incorrect in my assumptions, or are even small solar+battery setups in the five figure range?

No, you're not incorrect. Solar doesn't have to be expensive, most quote it that way because lots of people don't know any better.

I'll post some options in a minute...

[GeorgeandSugar]

Seems a lot for the power requirements you listed. If you could DIY, the cost would be a lot less. The set-up is straightforward.

https://www.wholesalesolar.com/


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[Grant H.]

First off, come up with a demand.

10 indoor 2 bulb fixtures, with 100w equivalent LED bulbs (14W each bulb) is 280 watts.
Laptop, Tablet, Smartphone charging - Figure on 90 watts for a laptop power supply
Outdoor light - Guess on 2 14w bulbs - 28W

Now, add time into the mix.

Indoor lights, figure 5 hours per day - 1400W (280*5)
Laptop, figure the same 5 hours - 450W (90*5)
Outdoor lights, use a photosensitive fixture to conserve engery - 15 hours (worst case in the winter) - 420W (28*15)

Total watt hours you need: 2270W/H per day (assuming this happens every day, unlikely, but plan for the worst).

Now, divide that by the number of hours of sun you get (again worst case). A safe bet for CO is 4 Hours.

2270/4=567.5 watts of solar. Now, I would upsize that by ~50% so that you are able to recover from a cloudy day.

That gives you ~900 watts of panels. In the solar thread I linked a site where 900w of panels is $750, before shipping. There are better prices out there, but they're an easy site to quote prices from.

Now, you have to decide what voltage you want to run the battery bank at, and I would recommend 24VDC or 48VDC. It means more batteries (more money), but it's better from a current draw standpoint.

2270w at 24VDC, gives you 94.5A/H required. That's what the listed devices above will use in a day.

For battery health, you never want to exceed 50% discharge, and staying at 40% discharge or less is better.

So miniumum, you need 200A/H of batteries to support your usage.

I would also suggest that your battery bank be able to run the required items for 2-3 days. Now you're at 400-600A/H.

A good go to for batteries, that I have used extensively, is a 6V 215AH golf cart battery. https://www.batteriesplus.com/productdetails/sligc110
They handle charge/discharge very well.

So, at 6V you need 4 in series to get 24VDC.
That means 8-12 batteries, so $800-1200 in batteries.

A charge controller and a inverter will also be required. For what you are building, I wouldn't bother with higher end solar gear. It's not necessary.

Low Cost MPPT: https://www.ebay.com/itm/4215BN-Tracer-40A-12-24V-MPPT-Solar-Charge-Controller-with-MT50-Remote-Meter/262118005517?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
Low Cost Pure Sine Inverter: https://www.ebay.com/itm/2500W-DC-to-AC-Power-Pure-Sine-Wave-Inverter-24V-to-120V-Solar-System-off-Grid/191682182193?epid=20009499413&hash=item2ca125fc31:g:q3sAAOSw~bFWQaBA

MPPT: $260
Inverter: $240

So, Grand total, minus wiring, boxes, etc, is $2450 for 900 watts of panels, 3 days worth of batteries, and a relatively well liked solar controller and inverter.

It's an overbuilt off grid system, but it will work well for what you want.

[Grant H.]

Sorry, it got "rambly"...

[Irving]

Sorry, it got "rambly"...

Maybe your explanation is just "over built." ;)

[Grant H.]

Seems a lot for the power requirements you listed. If you could DIY, the cost would be a lot less. The set-up is straightforward.

https://www.wholesalesolar.com/


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Keep in mind, their kits don't include batteries.

I also prefer having my solar controller and inverters separate. It protects gear, and your house/building.

[Grant H.]

If it actually makes sense to people reading it, then sure...

:D

[Grant H.]

I will also throw out there, that if you don't have anyone in the club that can help with the install, I can/will (with enough lead time for scheduling).

[Justin]

Sorry, it got "rambly"...

Not at all. That explanation was fantastic!

Thank you!

[Great-Kazoo]

I will also throw out there, that if you don't have anyone in the club that can help with the install, I can/will (with enough lead time for scheduling).

What's you fee, besides air, vehicle , food & shelter to set something up in northern Az?

[Grant H.]

What's you fee, besides air, vehicle , food & shelter to set something up in northern Az?

Depends on how long it takes. :D

PM me some details, if you don't want to post in a thread like this, and we can talk.

[SideShow Bob]

Grant H.’s reply was a very good in depth and detailed explanation.
The only thing he left out, as mentioned in another thread, is the permitting costs for property improvements.

If you were closer I would be willing to donate labor help toward installation in exchange for range passes.

[68Charger]

Why not go DC with such a small system? ( like RV gear) maybe small inverters for the laptops if you can't get 12v chargers for them...

No inverter costs or losses for the lights, could even look at distributing the batteries and panels to keep losses due to wire resistance down to a minimum...

https://www.superbrightleds.com/cat/off-grid-led-lighting/

[Grant H.]

Grant H.’s reply was a very good in depth and detailed explanation.
The only thing he left out, as mentioned in another thread, is the permitting costs for property improvements.

If you were closer I would be willing to donate labor help toward installation in exchange for range passes.

Very good point. I'm used to the world of industrial automation. The county makes sure the appropriate number of 0's has been added to their coffers, and they don't care beyond that...


Why not go DC with such a small system? ( like RV gear) maybe small inverters for the laptops if you can't get 12v chargers for them...

No inverter costs or losses for the lights, could even look at distributing the batteries and panels to keep losses due to wire resistance down to a minimum.

Also a good point.

My assumption is that their building has these fixtures already built in, with everything already wired for normal 120VAC, hence the inverters. Feed it into the panel and off you go. It also leaves the option of using the generator for extra power. (Would require a little more planning).

If that isn't true, then yes, considering switching to RV gear is a good option. Just be aware that if you buy 12V lights and such, you're going to want a 12V battery bank and 68C's comments concerning wire resistance and losses become even bigger worries.

[68Charger]

Very good point. I'm used to the world of industrial automation. The county makes sure the appropriate number of 0's has been added to their coffers, and they don't care beyond that...



Also a good point.

My assumption is that their building has these fixtures already built in, with everything already wired for normal 120VAC, hence the inverters. Feed it into the panel and off you go. It also leaves the option of using the generator for extra power. (Would require a little more planning).

If that isn't true, then yes, considering switching to RV gear is a good option. Just be aware that if you buy 12V lights and such, you're going to want a 12V battery bank and 68C's comments concerning wire resistance and losses become even bigger worries.

Agreed, it should be designed to the situation/environment... but if the genset is already wired in, then inverters could save labor... wouldn't know the best way to do it without seeing it, just trying to give options.

[Fentonite]

I learned from Grant’s posts (he’s the solar guru), and like 68Charger suggested, I built a small system using a 12V system, largely using RV lighting. It’s just a tiny shack in the mountains, but a single 30w panel (with a lot of southern exposure) keep two 12V marine batteries charged enough to run three different interior lighting zones, a small fan, a porch light, and a charging station for phones (or whatever). I didn’t do Grant’s fancy math, and I’m sure I did some stuff wrong, but I only use the power for 3-5 hours a day, not every day, but it’s never run out of juice yet... and it only cost a few hundred bucks. I posted pics before, but photobucket killed them. Shoot me a pm if you want me to text some pics or if you want a look in person.

[earplug]

Going AC allows a occasional use of a microwave or coffee pot. They suck watts but make match directors happy.

[Justin]

I will also throw out there, that if you don't have anyone in the club that can help with the install, I can/will (with enough lead time for scheduling).

Thanks for the offer!

At this point, everything is very preliminary. I'll need to throw a spreadsheet together with some numbers to see if the board is interested at all.

[Justin]

Why not go DC with such a small system? ( like RV gear) maybe small inverters for the laptops if you can't get 12v chargers for them...

No inverter costs or losses for the lights, could even look at distributing the batteries and panels to keep losses due to wire resistance down to a minimum...

https://www.superbrightleds.com/cat/off-grid-led-lighting/

Gut reaction is that the inverter would be the way to go. The building is already wired for regular light fixtures, plus the difficulty with sourcing DC-specific laptop chargers would probably make it a no-go.

[Irving]

First off, come up with a demand.

10 indoor 2 bulb fixtures, with 100w equivalent LED bulbs (14W each bulb) is 280 watts.
Laptop, Tablet, Smartphone charging - Figure on 90 watts for a laptop power supply
Outdoor light - Guess on 2 14w bulbs - 28W

Now, add time into the mix.

Indoor lights, figure 5 hours per day - 1400W (280*5)
Laptop, figure the same 5 hours - 450W (90*5)
Outdoor lights, use a photosensitive fixture to conserve engery - 15 hours (worst case in the winter) - 420W (28*15)

Total watt hours you need: 2270W/H per day (assuming this happens every day, unlikely, but plan for the worst).

Now, divide that by the number of hours of sun you get (again worst case). A safe bet for CO is 4 Hours.

2270/4=567.5 watts of solar. Now, I would upsize that by ~50% so that you are able to recover from a cloudy day.

That gives you ~900 watts of panels. In the solar thread I linked a site where 900w of panels is $750, before shipping. There are better prices out there, but they're an easy site to quote prices from.

Now, you have to decide what voltage you want to run the battery bank at, and I would recommend 24VDC or 48VDC. It means more batteries (more money), but it's better from a current draw standpoint.

2270w at 24VDC, gives you 94.5A/H required. That's what the listed devices above will use in a day.

For battery health, you never want to exceed 50% discharge, and staying at 40% discharge or less is better.

So miniumum, you need 200A/H of batteries to support your usage.

I would also suggest that your battery bank be able to run the required items for 2-3 days. Now you're at 400-600A/H.

A good go to for batteries, that I have used extensively, is a 6V 215AH golf cart battery. https://www.batteriesplus.com/productdetails/sligc110
They handle charge/discharge very well.

So, at 6V you need 4 in series to get 24VDC.
That means 8-12 batteries, so $800-1200 in batteries.

A charge controller and a inverter will also be required. For what you are building, I wouldn't bother with higher end solar gear. It's not necessary.

Low Cost MPPT: https://www.ebay.com/itm/4215BN-Tracer-40A-12-24V-MPPT-Solar-Charge-Controller-with-MT50-Remote-Meter/262118005517?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
Low Cost Pure Sine Inverter: https://www.ebay.com/itm/2500W-DC-to-AC-Power-Pure-Sine-Wave-Inverter-24V-to-120V-Solar-System-off-Grid/191682182193?epid=20009499413&hash=item2ca125fc31:g:q3sAAOSw~bFWQaBA

MPPT: $260
Inverter: $240

So, Grand total, minus wiring, boxes, etc, is $2450 for 900 watts of panels, 3 days worth of batteries, and a relatively well liked solar controller and inverter.

It's an overbuilt off grid system, but it will work well for what you want.

I have some questions about your example. If he needs 600 AH, and you are recommending some 215AH 6V batteries, he'd need three batteries to make 600AH,but will need four batteries to get to 24V, he'll just end up with 860 AH of batteries? Why will he need 8-12 batteries instead of only 4?

I quickly looked up a 100w panel and it is showing just over 6 amps. Is it correct to scale that up to about 20A for a 300w panel? If so, with three of those we're now looking at 60ish amps. Is that 40amp controller enough?

[68Charger]

I have some questions about your example. If he needs 600 AH, and you are recommending some 215AH 6V batteries, he'd need three batteries to make 600AH,but will need four batteries to get to 24V, he'll just end up with 860 AH of batteries? Why will he need 8-12 batteries instead of only 4?

I quickly looked up a 100w panel and it is showing just over 6 amps. Is it correct to scale that up to about 20A for a 300w panel? If so, with three of those we're now looking at 60ish amps. Is that 40amp controller enough?

Amp Hours don't add up on series, you're just increasing volts, and thus watt hours... so 4 batteries in series is 24V with 215Amp hours... or 5.160 KWh... to increase to 2 or 3 days worth, you'll need 2 or 3 strings of 4 (8 batteries for 430Amp hours, 12 batteries for 645Amp hours) at 24V.

the current on the panels depends on the voltage... lower volts is higher current... 900W / 24V is 37.5A


Oh, and that charge controller is cheaper at their website when they're not paying ebay fees:
https://www.hurricanewindpower.com/ep-solar-tracer-4215-bn-40-amp-12-24v-mppt-solar-charge-controller/

I didn't check the other items, but pays to shop around... I always look if a vendor on ebay sells for less elsewhere (like their website).

[Irving]

Thanks for clearing that up.

[Grant H.]

68C is right on the money.

Series vs Parallel will come into play a lot in solar stuff.

Always shop around for better pricing. I do as well, but when I'm posting something here, I generally just grab something easy that has the specs.

One thing I will add to what he shared:

The use of an MPPT controller means you don't have to shop for 24V panels to match your 24VDC battery bank.

An MPPT controller, the one suggested in this thread specifically, will take up to 150VDC in from the panel array. This allows you to daisy chain your panels and run smaller/cheaper wire to your panels. You have to make sure your panel array doesn't exceed 150VDC at open circuit voltage.

As 68C pointed out, 900W at 24VDC is 37.5A, which requires the use of 4AWG wire (6AWG is only rated to 37A).

The panels that I suggested are 39.7VDC at open circuit (3x @ 300W) which gives you ~120VDC at open circuit. Their Max Power Point (where the controller will likely run them) is 32.5V.

So 3x panels at 32.5V is 97.5VDC.

900W at 97.5VDC is only 9.23A. Now we can use 12AWG (on the edge - rated for 9.23A) or 10AWG (rated for 12A).

[68Charger]

Grant really knows his stuff, especially solar specific... I come from a general electrical/electronics engineering background and am not intimately familiar with solar panel and charge controller specs like he is...

at first I was like 9.23A for 12AWG, that's not right... but I realized you're using power transmission spec which is 700 circular mils per amp rule (VERY conservative, to minimize loss)... you're perfectly safe with up to 20A on 90degree C insulation on 12AWG according to NEC (National Electrical Code).. but you will have more loss at higher current with that spec.
That is to say, the choice for 12AWG vs 10AWG in this instance is an economic exercise, not a safety factor.

Of course, whenever you're doing longer runs (than say 50'), you should run a voltage drop calculation to determine if larger conductors are needed to keep voltage drop under 2% in design, in practice (after installation) it should be less than 5%... but this is based on whether or not everything will work, not best efficiency.... you'll find with power transmission spec, you have to get REALLY long runs before this is an issue.

[Irving]

Without derailing the thread too much, what do you think would be the minimum amount of system required to just run a laptop? The system on my van won't do it, but I'm not sure how far off I am.

[68Charger]

Without derailing the thread too much, what do you think would be the minimum amount of system required to just run a laptop? The system on my van won't do it, but I'm not sure how far off I am.

Depends on the laptop... the power bricks they use can have a significant amount of parasitic power loss (sucking power while not actually charging anything, even with the laptop off)... read the power spec on the brick for info.

Some laptops can run on inexpensive DC power cable adaptors to run off 12v power port (simple voltage regulator with cables & connectors)
Example: https://www.amazon.com/CHARGER-Dell-Inspiron-Latitude-E6430s-Adapter/dp/B002UI2Y8Q
Others require 15-19v and/or communicate with the brick, so they require more complicated solutions... an inverter and then a brick isn't efficient, so you would have to oversize the system to compensate, but it'll work.

[Grant H.]

Without derailing the thread too much, what do you think would be the minimum amount of system required to just run a laptop? The system on my van won't do it, but I'm not sure how far off I am.

You have a Lenovo w520 (if memory serves from your laptop thread), right? (I know, I could go search it, but I'm being lazy.)

The power brick that comes with those has a 20VDC @ 8.5A output. That's what your laptop wants to see on it's input. It doesn't need the full 8.5A if you put it to sleep/turn if off and just charge it.

Assuming you have a 12V system in your van, you would need to use a DC to DC converter to get the 20V out. Something like this (tunable output, rated for enough amps) https://www.ebay.com/itm/Boost-DC-DC-Converter-Power-Supply-Step-up-Module-12V-60V-to-12V-80V-600W-10A/231572940208?hash=item35ead2a5b0:g:-hgAAOSwBLlU9qKi

With that, you can use a multimeter to measure and set the output, then use it to run your laptop.

Now, the solar side gets a little more tricky for a few reasons:

1. You now how a step up converter (not 100% efficient). This means you have to oversize your system.
I'm sure we can find the efficiency curve for that design somewhere, but I'd just buy one and set it up with a current meter inline on the supply side to know how much to plan for.

2. Your panel is mounted flat, not aimed at the sun.
This gives you losses in what your panel can generate.


What battery setup do you have? That will help us figure out how long you can run your laptop before having to let the batteries recover.

[Grant H.]

Grant really knows his stuff, especially solar specific... I come from a general electrical/electronics engineering background and am not intimately familiar with solar panel and charge controller specs like he is...

at first I was like 9.23A for 12AWG, that's not right... but I realized you're using power transmission spec which is 700 circular mils per amp rule (VERY conservative, to minimize loss)... you're perfectly safe with up to 20A on 90degree C insulation on 12AWG according to NEC (National Electrical Code).. but you will have more loss at higher current with that spec.
That is to say, the choice for 12AWG vs 10AWG in this instance is an economic exercise, not a safety factor.

Of course, whenever you're doing longer runs (than say 50'), you should run a voltage drop calculation to determine if larger conductors are needed to keep voltage drop under 2% in design, in practice (after installation) it should be less than 5%... but this is based on whether or not everything will work, not best efficiency.... you'll find with power transmission spec, you have to get REALLY long runs before this is an issue.

Thanks. You clearly know electrical stuff very well, as well.

I've done a lot of solar over the years, and I enjoy it.

I appreciate you jumping in and adding depth in these conversations.

You are absolutely correct, I do use the power transmission spec. Several of my customers demand that their solar installs abide by it, so I just use it as a general rule of thumb. Overkill? Yes. But they write the checks and make the demands... The original customer to require that wire spec are the ones that we build 15KW installs to support major network backbone tower sites for.

[Irving]

I have a 50w Accopower panel and an 18AH battery. Right now I run my cheapy inverter off the vehicle. I'd like to be able to run it off my panel, but if not, I'll survive.

The nice thing is that my panel spends far more time charging the battery than the battery spends powering anything.

[Justin]

Stupid question:

If we build a system, and then decide at some future date that we'd like to have additional power, how hard is it to add extra battery capacity?

[Irving]

Not difficult, just a matter of wiring them all in and having the space.

[crays]

Seems a lot for the power requirements you listed. If you could DIY, the cost would be a lot less. The set-up is straightforward.

https://www.wholesalesolar.com/


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Wholesale Solar is is running a special on battery banks right now. 50% off select battery banks with purchase of any qualifying off-grid system. (saw it on FB)


OFF GRID SOLAR SALE

Get 50% Off your off-grid battery bank when you purchase a cabin sized package or larger.

No matter how many batteries your chosen system needs—four, eight, sixteen, twenty-four or more—we’ll give your battery bank to you AT 50% OFF

[Grant H.]

Not difficult, just a matter of wiring them all in and having the space.

This.

You can always add batteries. It will just take longer to fully charge, with no change in panels.

Growing a system is generally pretty easy.

[Grant H.]

Wholesale Solar is is running a special on battery banks right now. 50% off select battery banks with purchase of any qualifying off-grid system. (saw it on FB)

I don't mean to sound like I am harping on them, but there is a reason they can offer to sell a battery bank at 50% off.

The offer requires the purchase of a "Cabin" sized system or larger.
The cheapest (smallest) "Cabin" System is 1080 watts, and costs $6620 with no batteries. It does have a very good solar controller (Midnite Classic 200), and a decent quality inverter, so those are good selling points, but it's still 2.5x the cost of a complete diy system.
A comparable battery bank is $1466, and you can save $733 (50% on it)

So, for an extra 180 watts of solar, a better solar controller and inverter, you would be spending a grand total of $7353+shipping.




For comparison:

Taking the $2450 system I laid out earlier:
Add another panel - +$250
Upgrade the controller to the same Midnite Classic 200 - +$400
Upgrade the inverter to the same - +$1300
Add some more batteries - +$400

So now you have:
1200w Solar
High end MPPT Solar Controller
Decent Quality Pure Sine Inverter
860AH of Batteries

For $4800+shipping.

[crays]

Didn't know if it was a good deal or not.
Figured I'd throw it out there.



Sent from somewhere...

[bradbn4]

Interesting; sort of wondering how much shipping adds to the overall bill.
I figure batteries would be best sourced local to cut down on shipping costs.

Add in some supper caps to provide for the high startup surge on some appliances...

[Justin]

Interesting; sort of wondering how much shipping adds to the overall bill.
I figure batteries would be best sourced local to cut down on shipping costs.

Add in some supper caps to provide for the high startup surge on some appliances...


Interestingly enough, I know a guy who replaced one of the batteries in his truck with a bank of super capacitors. Pretty cool stuff.

[Grant H.]

Interestingly enough, I know a guy who replaced one of the batteries in his truck with a bank of super capacitors. Pretty cool stuff.

I did it with my motorcycle.

Probably building a pair of bigger banks for my brothers diesel.

Super caps are pretty slick, but they have their limitations. Their self discharge is much higher than a normal battery, so they have to be used more frequently or they have to be trickle charged between use.

Their capacity is limited, and rather expensive, but they have their uses.

[Justin]

So the installation of a solar array was brought up at the last board meeting, but the decision was made to stick with using the generator. Not totally surprised with the outcome, but everyone's input here was helpful in discussing the issue.

[bradbn4]

For simple setup and short term use a good generator is hard to beat. I could see getting one or two panel setup to support keeping an electric start generator's batteries topped off.

For a friend of mine in Texas I keep saying you should get a small setup to handle the mundane stuff for one of the outbuildings. Nothing over the top, but something useful to help out in a pinch. They keep wanting the setup to do more, so it costs more, so they opt out of the project. I even offered to pickup part of the tab just to see how well it would perform in a real world setup.

I am happy some place like http://sunelec.com/home/ is not in the Colorado back yard, otherwise I would be tempted in setting up a one or two battery solar fun project for summer use.