Installing Off-Site Watering Setup

[Naptown]

Panels made for batteries generally will have a cell count of 36 for 12v and 72 cells for 24v
That said there are a lot of 72cell grid tie panels out there.
However you are still losing a good bit with a PWM controller. Roughly a third
You will need a minimum of 72 cells to charge a 24v battery efficiently.

[OregonSolar]

OK I see problems maybe. Are you running the system at 12 or 24 volt battery. If 12 volt you must use MPPT. If you intend to run at 12 volts with a 36 volt solar panel (24 volt battery panel), that PWM controller will turn your 240 watt panel into 87 watt panel.

Once you get above 200 watt panel wattage MPPT is less expensive. There is two reasons for this.

1. With MPPT you can use higher wattage, higher voltage, much less expensive Gri Tied panels. Grid Tied panels are 1/2 the cost of battery panels.

2. is efficiency and power. It takes a 300 wat panel with PWM to make the same power as a 200 watt MPPT.

What you have done is made the same mistake most make. You only looked at the cost of the controller, rather than the project. I can buy a 200 watt GTI panel and a MPPT controller for less than you can by 3 watts of battery panels and a PWM controller. Not only that but I get to save on installing 1 single panel with less and smaller wiring. 300 watt s of battery panels is at least 2 panels with twice the hardware and more and large wring. It would cost you $1000 all together with PWM, or $700 with MPPT.

It is a 24V system, 24 volt battery, 2 175Ah (upping to 200Ah)12V batteries in series for 24V. But one thing to clarify: What is the difference between a GridTie panel and a Battery panel? Aren't they all solar panels?

You've convinced me. I have a 240Wpanel; i'm going with MPPT.

[Sunking]

OK I see problems maybe. Are you running the system at 12 or 24 volt battery. If 12 volt you must use MPPT. If you intend to run at 12 volts with a 36 volt solar panel (24 volt battery panel), that PWM controller will turn your 240 watt panel into 87 watt panel.

Once you get above 200 watt panel wattage MPPT is less expensive. There is two reasons for this.

1. With MPPT you can use higher wattage, higher voltage, much less expensive Gri Tied panels. Grid Tied panels are 1/2 the cost of battery panels.

2. is efficiency and power. It takes a 300 wat panel with PWM to make the same power as a 200 watt MPPT.

What you have done is made the same mistake most make. You only looked at the cost of the controller, rather than the project. I can buy a 200 watt GTI panel and a MPPT controller for less than you can by 3 watts of battery panels and a PWM controller. Not only that but I get to save on installing 1 single panel with less and smaller wiring. 300 watt s of battery panels is at least 2 panels with twice the hardware and more and large wring. It would cost you $1000 all together with PWM, or $700 with MPPT.

[OregonSolar]

OK, so scratch that idea.

So far, my estimated cost per system is about $900. here is my list, it may be a little on the low side of the energy ratings but I can live with it.

STATS:
Solar panel 24 volt 240 Watts 10A: $210
Pump 3GPM @ 3A 24Volt: $100
Charge Controller Morningstar Prostar PS-15 $95
Two 175Ah 12V deep cycle FLA batteries: $240x2=$480
TOTAL COST: $885

Run time per day, not counting longer Summer hours: 6HR


I know its a PWM charge controller and that's probably not enough panel for the charge controller. But at this point, it's either a better charge controller or a bigger panel, and I'm already getting a little big on the panel as it is. For a MPPT option in the charge controller department is a SunSaver SS-MPPT-15L. Would this controller be a good choice or do you have another preference? With this model i'll be slightly over my preferred cost of $1000.

CORRECTION: I really need to go up to a 200Ah battery, don't I. The calculator says so.

ANOTHER EDIT: And I assume a FLA would be a good system for this? I'm not sure if a FLA or an AGM would be better, but I'm leaning towards an FLA simply for lower price and I don't need the higher charge current.

[Sunking]

Here's another possibility for my batteries: Perhaps LiION?

From what I've read so far, they have a MUCH higher energy density than FLA's or AGM's, and can be discharged past 60% safely. .

Yes they do have much higher energy density, but so what? That is only important for motive power where weight is a concern.

A mid quality FLA battery that will last you 3 to 5 years cost around $175/Kwh. A mid quality 2 to 4 year AGM around $225 to $300/Kwh. A very low end 1 to 2 year LiPo around $500/Kwh and a high end 5 year Lithium Titanate used RE power in substation is around $1000/Kwh. Not even utility companies use them, Why would you spend $1000/Kwh when you can get the same for less than $200/Kwh?

In addition to be being cost prohibitive, there is no charge controllers out on the market for lithium chemistry except for the RC (Radio Control Toys) market which is a motive power market. No one makes them yet because lithium is still too expensive and thus no demand. It would be a custom design.

[Naptown]

Yes you can
However there isn't really a solar charge controller made for those so it would be something custom
Second you would be drastically increasing your battery costs.
The least expensive battery chemistry is lead acid.
High Energy density isn't really an issue with solar.

Did you re run the calculator using the revised watt draw of the pump?

[OregonSolar]

Li batteries?

Here's another possibility for my batteries: Perhaps LiION?

From what I've read so far, they have a MUCH higher energy density than FLA's or AGM's, and can be discharged past 60% safely. Since bulk is a factor in this setup as everything has to fit in one pole mounted box, would this be a possible solution?

I understand that they take a lot more advanced charging controller technology, but if I can get the weight and bulk of my batteries down it would be great.

[OregonSolar]

Ok how long would that tank last
Lets say 20 years for the sake of the discussion
And a battery bank lasts on average 5 years with very good care
Now say good quality batteries will cost about $600.00 and last 5 years on the outside.
Which is more cost effective in the long run!

Yes and no. Poly tanks tend to crack after about 10 years sitting in full sun. Ever leave an empty milk bottle outside all summer, and then when you go to pick it up it falls apart? Same principle. Seems more cost-effective than the batteries, even after I did fix the calculator amps. Interesting to think about...

Note: A setup involving a tank would require twice as much fencing around due to the extra surface area, but this cost is negligible. And you need a big truck to haul the tank out of the field in fall, then back out again in spring. The battery setup all it takes is to remove the pump so it doesn't get flooded.

[OregonSolar]

Setting up an adjustable tilt is fairly easy
Generally though go for the angle that gets you the most for the worst insolation month the system will be used.
Don't even think about trackers on this scale.
So based on your head what will the pump produce an hour?

2.8GPM at 10 PSI. But I just realized something: The retailer I was looking at had the wrong amperages. The pump is actually only about 3 amps. So with the revised amperages, the calculator says I only need a 200 watt panel and 150Ah of 24 volt batteries. This is very easily within my grasp. Sending a revisory email to my boss.

Looks like it might be worth it after all.

[Naptown]

The only problem with that is storage. Ideally there are two 350 gallon stock tanks out there. The original plan was to use solar panels to charge some batteries, which would run the pump when a float in the tanks called for water. You see, for some reason the contractor wants NO overflow, hence the battery design. To run an 8 GPM pump for 5 hrs would require an extra 1500 gallon storage tank that would drain into the stock tanks using a float. This is out of the question, considering a 1500 gallon poly tank costs $800+.

Ok how long would that tank last
Lets say 20 years for the sake of the discussion
And a battery bank lasts on average 5 years with very good care
Now say good quality batteries will cost about $600.00 and last 5 years on the outside.
Which is more cost effective in the long run!

[Naptown]

Setting up an adjustable tilt is fairly easy
Generally though go for the angle that gets you the most for the worst insolation month the system will be used.
Don't even think about trackers on this scale.
So based on your head what will the pump produce an hour?

[OregonSolar]

Well you are not the first to bring this subject up.
Mostly however from Texas.
Now how many feet above the stream is the tank to be located? This is important to calculate the head on the pump.
A pump that has to pump up vertically 100 feet may only put out 1/5 the water if it was only 10 feet. The numbers above are arbitrary and depend on the pump selected.
So lets get that settled first.
Second up is a zip code to check insulation at various tilts for the location.
Bet the place in Florida didn't ask this many questions.

So far, depending on some locations, it will be no more than 20ft of lift through about 100ft of 3/4 inch black poly pipe. I understand the pump lift concept; assuming an only 20ft lift (10PSI pump pressure) I should be running nearly at maximum flow.

Zip is 97624. This site (http://solarelectricityhandbook.com/...alculator.html) reccomends a 66 degree angle from horizontal in winter (round to 65, won't use), a 42 degree angle spring/fall (round to 45, may use), and a 18 degree angle in summer (Will use definately, round to 20 degrees). Is it just me or does the 18 degree angle seem a little shallow? I mean, it will really cut down on your exposure in the later afternoon and early morning.

[Naptown]

Well you are not the first to bring this subject up.
Mostly however from Texas.
Now how many feet above the stream is the tank to be located? This is important to calculate the head on the pump.
A pump that has to pump up vertically 100 feet may only put out 1/5 the water if it was only 10 feet. The numbers above are arbitrary and depend on the pump selected.
So lets get that settled first.
Second up is a zip code to check insulation at various tilts for the location.
Bet the place in Florida didn't ask this many questions.
Lastly how much do the cows drink daily
It is cheaper to have the storage for perhaps 2-3 days in the water tank than to buy and maintain batteries.
( think water storage in place of batteries)

[OregonSolar]

Ok
Then lets think about things that would not require a battery.
There are pumps and controllers that do not have batteries and are used for this exact purpose.

What about wind?

What about wind? Not consistent enough. A good 20MPH blow that would maybe provide enough energy to do something comes around once a month. Mostly we range from calm to 10MPH sustained, with occasional 15MPH gusts. Oregon ain't the Great Plains, you know.

Sorry to rain on both our parade's, but solar is really the only consistent energy source out here.

What do you mean, systems that don't require a battery? I already brought this up, storage (1500 gallon poly tank+two 350 gallon open top stock tanks) for a 8GPM pump running 5hrs costs just as much as getting the batteries.

I'm just being difficult, aren't I...

[Naptown]

Ok
Then lets think about things that would not require a battery.
There are pumps and controllers that do not have batteries and are used for this exact purpose.

What about wind?