diy solar

diy solar

Beginner planning solar pond aeration

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rddmddiysp

New Member
Joined
May 28, 2023
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Location
Maryland
Hi all,

Brand new to this forum (and to learning about solar power, generally!)

I've read several other threads on pond aeration (shoutout to Brian Sloan, in particular, for this excellent-looking setup and writeup), and watched countless videos.

While there's a ton of good info, it's all a bit overwhelming - and I'm starting to twist myself in circles. So I figured I should take a stab at sizing and selecting components, to get feedback / corrections sooner.

Background:
* Looking to power two diffusers from a single compressor / air pump, for a 0.2 acre pond of ~6-8 ft depth. Leaning towards the HIBLOW HP-60 compressor, which uses 51W at 1.18A.

* This setup is only intended to run during spring and summer months. I'm located in Maryland, where we expect to receive irradiation > 5.75 kWh/m2/day from May thru July (according to https://www.nrel.gov/gis/solar-resource-maps.html) - although only for an average of 7 hrs per day (due to surrounding trees & hills).

* I'd like the pump to run ~8am to ~8pm, but this is not critical (i.e. it's Ok if it doesn't run at all on cloudy days, or shuts off early)

Components:
* On sunny days, we'll want 5-6 hours of supplementary battery power @ 51W, so I'm thinking a single AGM deep cycle 30AH 12V battery would suffice.. ?

* To keep things relatively simple, I'm leaning towards a 200W Topsolar Mono Panel kit（2 x 100W; 12V, with 20A PWM controller)


I've left out some components and a TON of details, because I'm just not yet "there" yet... But is ^this a reasonable start? Any and all input is appreciated!

(please keep in mind I'm new to this and, while I'm investing a good chunk of time to learning, I have limited bandwidth for this side project)
 
So a couple things that catch my attention:

You say the pump runs at 51w and 1.2a which implies a 48v system, but you're listing a 12v battery on there. That's not gonna work. You'll either need 4 batteries in series for 48v OR a 12v based pump.

200w of panels isn't going to get you enough voltage to charge a 48v system, you'll need at least 4x 100w panels to do that, OR back to the 12v system.

An AGM battery based system is going to do well in the weather but being lead acid should only be drawn down to 50% so your 30ah is only good for 15ah. Still not bad but needs to be considered.

If you go with a 48v system you'll want an MPPT controller to really utilize those panels to their fullest. Anything 20a or so would be plenty.

Look into used panels, the 250ish watt panels tend to be aboit the same price as a 100w panel online. A pair of those would be plenty for a 48v setup.

Noodle math says 50w × 8hr = 400wh / 48v = 10ah, so a set of 30ah batteries would buy you that 12hrs without hurting the lifespan. 60ah would get you a couple cloudy days. Either way you should be able to use the LOAD ports on the SCC and just program it to shut off the pump before the batteries get too low to protect them. ?

Other than that it looks like a simple system once you get the math figured out. My guess would look something like:

2x 250w used panels in series
4x 30ah AGM batteries in series
20a 48v MPPT SCC (anything that takes 100v PV input would be fine, no need for Victron money)
50w 48v air pump system
Pump connected to LOAD terminals, programmed to shut off at 44v to protect batteries
Start/stop timer OR programmed via SCC run time
 
Those are usually 120V AC pumps. If you were closer, I'd set you up with an amazing no battery system for next to nothing. I've been wanting to do one of those daylight systems, but I have no pond. My neighbor has one of those pumps for his septic system he no longer uses. Think I might try a batteryless this summer that only costs $25. Really, never use battery voltage panels.
 
@Rednecktek , @efficientPV - thank you very much for the replies! Now for a really dumb follow-up question...

I'm very confused about the voltage of the pump I have in mind (HIBLOW HP-60).

Rednecktek (and basic math) suggest it is 48V, but HIBLOW's spec sheets don't specify - and efficientPV says it may be 120V AC. :confused:

I do understand now that the solar panels should exceed my chosen battery voltage - and Rednecktek has given me a lot more grok and incorporate into my planning (hopefully this evening). So I have a lot more homework to do.

Could you help me understand the voltage of the pump, in the meantime? TY!
 
So looking at the link it is indeed a 120v AC pump, so that changes a LOT of things as the solar and battery end has a LOT more variations available because at the end you're still just going to need to get an inverter involved to convert the battery side to 120v. Whether you do a 12v system, a 24v system, or a 48v system, you just need the appropriate inverter to go from 12v -> 120v or 24v -> 120v or whatever. That actually simplifies things a lot.

So, let's go back to the napkin math here and play with some numbers.

51w of draw * 8 hours of runtime = 408Wh of battery
Give yourself 85% efficiency between all the parts converting and inverting and that's 469.2Wh of battery per day.
If you want to run this on a 12v system that's 469.2/12v = 39Wh of battery per day.
Lead acids are only good for about 50% discharge to keep them happy and healthy, so 39 * 2 = 78Ah of battery per day.
Since nobody makes a 78Ah battery, you'll probably end up getting a 100Ah battery. That'll get you 1 day or so of pump running before the low voltage cut-off says "Battery's dry, no more juice for you!"
If you want to factor in multiple days of run time in krappy weather figure adding in a battery for each day of standby.

OK, that's the battery side... making sense so far?

The solar side can be done a couple ways, let's look at the 2 simplest versions, 100w panels and used 250w panels:

100w Panels: You basically need to generate 500w of power per day. Since 100w panels (almost) never put out full rated power, and the average napkin math average is 4 hours of sunlight, you'll want to use 2x 100w panels. That gives you roughly 100w * 2 panels * 80% efficiency * 4 hours of sun = 640Wh of power per day in good sun. Sometimes more, sometimes less, but in that rough area depending on weather* conditions.
Getting everything new off Amazon and you're looking at about $80/panel, but you only need a little 20a PWM controller so you can probably get the entire setup and wires and all for less than $200.

Used panel: So back to the 500wh of power per day, the more common used panels available on the used market are about 250w for about $100 each. In this case you only need a single panel BUT because these panels run at a higher voltage you need a proper MPPT controller to convert from high voltage solar to lower voltage battery voltage. Again, you're going to need something in the 20a range and just doing a quick scan there are a few options from the Super Simple at about $80 to the Super Cheap and not sure I'd trust it for less than $50 to the Tried and Trued with a few features for $90. With a single panel and wires and MPPT controller (which buys you a couple handy features) you're looking at around $200, probably a little less. Going with a larger controller lets you expand in the future and isn't much more money for the next step up if you want future expansion. One of the big advantages also of the MPPT controllers is that they often times have LOAD terminals that are rated to the MPPT (so a 20a MPPT can provide 20a, a 40a MPPT can provide 40a, etc.) and settings built in to turn low voltage cutoff where it will stop powering the LOAD ports before the battery gets too low which protects your batteries. Very handy in a small system.

Either way should be plenty.

OK, you're going to need an inverter to convert the 12v from the battery to the 120v that the pump needs, but fortunately not a big one. There's a thing called "Startup surge" or "Locked Rotor Amps" with motors that represents the amount of power required to get all the parts from a standstill to up and running since physics is a thing. Most of the time getting that information from a manufacturer is nigh on impossible but rule of thumb is 3x to 5x the running power. So, assuming worst case, your 51w pump would need 51 * 5 = 250w for startup surge. That means that anything over 300w on the inverter is overkill. As an example, Giandel has a 300w unit for about $60 and is a well respected brand.

One place you can save money is the battery. Usable watt per dollar nowadays the AGM batteries and LFP are about break even, but AGM handles freezing temperatures a LOT better for the cost if weight isn't an issue. On the other hand, you can get a WallyWorld DC29 battery for about $100 anywhere and that gives you about 60Ah of usable power on there. Yes, you'll have to check the water every so often but being 1/3 or less the price of a comparable AGM makes it worth it to me at least.

OK, lots to parse there but hopefully it all makes sense. Just as a reference, if I were to be doing this project on a budget, I'd probably do something like this:

2x 250w used solar panels
40a HQST MPPT controller
Giandel 300w inverter
2x WallyWorld DC29 batteries
30a breaker for SCC to inverter
25a breaker for solar to SCC (for servicing and troubleshooting and such)
10AWG wires all the way around
Inverter 120v -> Basic wall timer -> pump
Panels -> 25a breaker -> SCC PV port
Batteries in parallel -> SCC battery port
Inverter DC -> 30a breaker -> SCC LOAD port

If I needed to shave some cash, drop to a single panel and a 20a SCC and save about $130 or so. But that's just me and an example.
 
@Rednecktek that's an amazingly helpful response - it clarified a lot. Thank you very much.

I follow all of your math (I think), and really appreciate links to specific options.


Additional question: where can a newbie find reliable / trustworthy used panels? If something local (craigslist / FB marketplace), what specific things should I look for / inspect / test in person, before buying?
 
I know this is a Solar power forum, and I’m a big fan of solar. But you may want to consider wind power for this if you’re in a location where wind is available.
Wind doesn’t get a lot of love here because small-scale wind for electricity is lousy. But small-scale wind to pump air can be pretty good, and you eliminate a lot of complexity.
Instead of Solar to battery to inverter to pump —-> lots of components to buy and maintain, lots of things to break.
You just go windmill directly driving a compressor that pumps air into your pond.
You Solar setup sounds like fun, and it would probably be pretty fun to build. But if you’re just looking to aerate without power available, at least consider wind as an option.
 
rddmddiysp said:
Additional question: where can a newbie find reliable / trustworthy used panels? If something local (craigslist / FB marketplace), what specific things should I look for / inspect / test in person, before buying?
Click to expand...
Yeah, craigslist or facebook are the regular haunts for used panels, especially considering the obscene costs of shipping. Things to look for when checking out panels are bubbles in the back, trails down the cells, and take a multi meter with you, preferably a cheap one that can do DC amps. The panel will have VoC and Imp ratings on the back. Stick the panel in the best sun you can and check the voltage. Then connect the ends together and check the amps. If the volts are close to the VoC and the amps are close to the Imp, then the panel is good enough for gubment work. ?

If you see bubbles, snail trails, cracks, signs of physical damage, etc, grab another one from the pile. People selling these usually have a stack of them.
 
With installers, it's panel of the month. Panels are a commodity and installers buy them by the pallet. Next month they buy some other brand which is cheaper. They always have a couple left over and they don't match the new ones they are buying. I've got really reasonable prices on these. Look up small installers and ask what they have left over.
 
Thanks for all of the helpful responses!

@LakeHouse - when I first concocted this project, I had a similar thought - but quickly ruled it out as it's one of the least windy areas of the property (which contributes to the stagnant water surface - hence our current algae predicament - hence the need for aeration ; )

@Rednecktek - TY for the info on used panels, and criteria for inspection. I might check out some to further educate myself, at least.

@efficientPV - understood regarding installers & commodity panels. Makes sense.

Two more questions on the controller piece, as I'm drawing closer to a "final" components list (which I'll share here of course):
  • With two 12V 100W panels, would a 20A controller suffice? (200W % 12V = 16.6A)
  • I'm intrigued by an MPPT controller because of the increased efficiency and monitoring capabilities, but if I understand correctly they are more susceptible to water damage - is that accurate? I'm currently intending to store the components in a simple Lowes storage bin or the like (with some holes drilled for wires, and caulking/sealant). Would that be problematic?

?‍♂️
 
rddmddiysp said:
Two more questions on the controller piece, as I'm drawing closer to a "final" components list (which I'll share here of course):
  • With two 12V 100W panels, would a 20A controller suffice? (200W % 12V = 16.6A)
Click to expand...
Yup, and you can use a basic PWM controller if you need to, you'll just lose any real functionality on the LOAD terminals which makes it a little more complicated to deal with low voltage cutoffs, but you can actually throw 300w of panel on there and be just fine.
rddmddiysp said:
  • I'm intrigued by an MPPT controller because of the increased efficiency and monitoring capabilities, but if I understand correctly they are more susceptible to water damage - is that accurate? I'm currently intending to store the components in a simple Lowes storage bin or the like (with some holes drilled for wires, and caulking/sealant). Would that be problematic?
Click to expand...
??? Who told you that and what were they smoking? You might want to put in a computer fan (I've used these IP67 rated Noctuas in greenhouses) on a thermostat (I've used these in greenhouses and my diesel heater project) to ensure it doesn't overheat in the summer. As long as there's enough airflow the controllers (and yes, even PWM's) will usually be fine. I've mounted stuff in HF's Apache cases without issue multiple times, just gotta have air space around the components. Having ventilation will also help prevent gas buildup from the batteries venting and reduce the risk of an earth shattering Kaboom!
 
I'm going to ask my neighbor to borrow his pump he doesn't use any more. Just today I got a 60V 220V inverter that works great off two grid tie panels. Only $25 shipped. For some reason 60VDC is common in Europe. They can't give those inverters away in he US, but they are really neat for running things off panels with no battery.
 
Ok, I've incorporated a bit of updated knowledge and some very helpful feedback. Is there anything that I've miscalculated, or egregiously poor choices in my selections below? Thoughts on the 100Ah AGM vs 50Ah Lithium battery?




  • Pump: HIBLOW HP-60 60lpm air pump
    • (hoses & diffusers to be ordered separately)

I'm ready to order, if this looks sane!
 
Both batteries offer the same usable power but the AGM won't die when it gets below freezing out.

About the only concern I have is that the inverter may kill the battery by draining it so low that the SCC doesn't have enough voltage to turn on in the morning. A wall timer to feed the pump during daylight hours (or 8 hours or whatever) will help that a lot.
 
Last edited:
Rednecktek said:
Both batteries offer the same usable power but the AGM won't die when it gets below freezing out.

About the only concern I have is that the inverter may kill the battery by draining it so low that the SCC doesn't have enough voltage to turn on in the morning. A wall timer to feed the pump during daylight hours (or 8 hours or whatever) will help that a lot.
Click to expand...

I'll add a wall timer to the components list. Thanks!

(this $14 option seems suitable.. ?)
 
Now mind you, with what you've got planned with 200w of solar, a 100AH AGM battery, and about 625Wh of load, you're maxing out what that system could provide. That's going to be a full cycle of the battery every day and if you get a day of bad weather or clouds the system is going to be out of juice. You're going to want to keep a real close eye on things the first few days at least and may have to reduce the run time of the pump at the very least, but when winter hits it's going to be really tough to keep aerating every day.

Plan for a few upgrades in the near future, a few hundred watts more panel, a larger SCC (probably MPPT to wring every last drop out of the panels), and at least 2 more batteries. I would honestly recommend doing it in that order and if you can swing it now get a 3rd panel involved right out the gate and connect all 3 in parallel to that controller.

For a few dollars more than that AGM you can get a pair of the WalMart DC29's which are 122ah each which should give you about 2 days of runtime without running the batteries too low. All 9 of the ones I've bought over the years cost me about $100ea after tax and core charges. I've damaged more AGM's over the years than wally worlds and it's cheap enoigh and available enough that I find them to be a great value.
 
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