I've made a plan... maybe my research will help someone. This seems so obvious, yet _every_ thread on this forum I've found seems to just respond with unhelpful "don't do it" type comments.
Personally, yes I totally could run house electricity to this pond, but I'd rather figure out solar. Just like I'd rather figure out a bog filter than throw a fancy mechanical, biological, and UV filter in there. Plus my electricity is $0.23-$0.30/KWh. So this will save me a couple dollars a month on my electric bill. In 10 years it would pay for itself (not that it'd last that long). Although if I factored in hiring an electrician to bury conduit to my pond that'd very quickly change all that math.
My pond is about 200 gallons (max dimensions 8'x4'x2' but with sloping and ledges). I have an 8 gallon preformed MacCourt Waterfall that will actually be used more as a bog filter than waterfall. Goal is to pump water into it, water to up flow through gravel. We'll see how that works!
Thankfully I don't really care at this point about the flow rate through the waterfall weir and I'm likely to restrict it to be smaller, or upsize the pump.
My thoughts/research to this point on a solar powered pump into my bog filter/waterfall thingy.
1. DC Pump
A) AEO WP50D ($60) https://amzn.to/3w8UxdV
- Voltage: 12-24V DC and has dry run protection
- Flow Rate: 240G/H@12V; 410G/H@24V. I'm running starting running it ay 12V
- Head: 3.3ft@12V / 10.5ft@24V. I only need it to lift water 12" into my bog/waterfall, and assuming 100gph it ought to be sufficient.
- Power Consumption: 5.0W@12V ~ 21. 5W@24V (in amps 5W/12V = 0.42A or 21.5W/24V = 0.89A)
Power consumption math: 0.42A x 24h = 10 Ah from a 12V battery on a day without any sun. (20 Ah from a 24V battery). However, I personally don't need it to run 24/7 it's just good to know for sizing panels and batteries.
B) AEO-WP80D ($140) https://amzn.to/3bifvPj
- Voltage: 12-18V and has dry run protection
- Flow Rate: 660G/H@12V; 898G/H@18V
- Head: 5.9ft@12V / 9.8ft@18V
- Power Consumption: 17W@12V ~ 33W@18V (in amps 1.4A @ 12V or 1.8A @ 24V)
Power consumption math: 1.4A x 24h = 34 Ah from a 12V battery on a day without any sun. (44 Ah from a 18V battery bank).
I'm probably going with (A) because again, I don't really care about making the waterfall/weir look like Niagara Falls, I just need water movement.
2. Solar Charge Controller -
A) Renogy Voyager 10A or 20A PWM Waterproof Solar Charge Controller $35-45 https://amzn.to/33vSzYz
or
B) Renogy Wanderer 10A or 30A PWM Solar Charge Controller $20-30 https://amzn.to/3uDagBg
I'm still debating the Voyager (more expensive, but waterproof) vs Wanderer (cheaper, the 10A has a load output).
Either of these has more than sufficient capacity. But, if all this fails, I'm probably reusing some of this to pump my rain catchment water up hill which will require a much strong pump (20' of head).
I was leaning towards the Voyager since it's waterproof end though everything be in a weather proof box anyway. But I'm going to start with the 10A wanderer which has a built in load output which means I won't need a separate low voltage battery cutoff to prevent over discharge (See 5). They're cheap and easy to wire, but is just one more thing to worry about.
3. Solar Panel
You have to consider how many hours of "peak sun" you'll get, which varies by latitude as well as shade. I'm in Southern California where with an unobstructed sky I get 6 hours of sun. I also have a weather station that tracks solar/UV radiation so I know it gets 6 hours and over 24h about 200W/m2 (too much geeky detail for most to worry about).
However, where I'm putting this (next to my pond) will get less than that because of trees, so I'm being conservative and assuming only 4.5 hours hitting this panel. This is a good place to be conservative in your estimations.
A) 30W Solar Panel $40 https://amzn.to/33D7iRn
Power (Imp) 1.69A
4.5 hours * 1.69A = 7.61 Ah
or
B) 50W Solar Panel $85 https://amzn.to/3faQFBV
Power (Imp) 2.86 Amps
4.5 h * 2.86A = 12.9 Ah
or
C) 70W Solar Panel $70 https://amzn.to/3uCpjeK
Power (Imp) 2.55 Amps (Note: this is at 28V operation voltage which is unusual but most charge controllers will accept)
4.5 h * 2.55A = 11.48 Ah
Fuzzy math, for comparison this is more like 17 Ah)
or
D) 100W Solar Panel $100 https://amzn.to/2R6viK4
Power (Imp) 5.56 Amps
4.5 hours * 5.56A = 25 Ah
Note, in the RV world the rule of thumb is 30ah from a 100W panel, they assume close to 6 hours. Again, I know my hours of sun is curtailed so my numbers are a bit lower.
Key things to note on panel sizing
- The 30W panel has enough amps to power the larger pump while the sun is out, but not while also charging a battery. @Keyboard you might try the 30W panel with the smaller pump. I think it'd work quite well for a total cost of $100.
- Two 100W panels (5a + 5a) would be too much for the smallest 10A charge controller (you really don't want to max those out, 70% is a common sizing recommendation), so plan ahead.
- Price and efficiency are related.
Adding more solar panels later (as long as it doesn't exceed the charge controller) just takes space... but for esthetic reasons I'd rather keep things small to start, as well as use "all black" panels and I'm going with (B) here. If it's not enough I may add a second identical panel, but the almost square 22"x26" really appeals to me.
4. Battery
First, if you have warm weather a Sealed AGM battery might be cheaper and work just fine. LiFePO4 batteries however last longer and are much better in cold (freezing) weather. It's just they're also a lot more expensive. Large ones are very very expensive. Since I I just need a small one and I do get a little snow in winter I am considering them.
A) Mighty Max 12V 8Ah 2 pack $35
Buy Mighty Max Battery 12V 8Ah UPS Battery Replaces 35w EnerSys Datasafe NPX-35T - 2 Pack Brand Product: 12V - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
amzn.to
I buy these in bulk anyway for my Uninterruptible Power Supplies. Wired in series would get 16Ah. This isn't bad, but I do think I really ought to use a 100W panel for this. I might get away with it by turning off the pump for an hour in the afternoon. It's very important you fully charge your batteries regularly.
B) Miady 12V 6Ah LiFePO4 $33
Note, this is crazy cheap for a LiFePO4 battery and not a company I'm very familiar with (I bought a generator inlet made by them and it was decent quality, but batteries are a different beast). So don't take this as a recommendation.
I'm going with B. I'll let you all know how it holds up. I _feel_ like the battery is going to be too small, but I can always add a second one in series, coupled with a second panel. I could go with a 20Ah LiFePO4 now, but I feel like I'd need a 100W panel for sure then.
5. Low Voltage Cutoff (if not using a controller with an output)
A) Digital Low Voltage Protector Disconnect Switch Cut Off ($12)
These are nice as you can set a shut off voltage (10 or 11V) and then a turn on voltage (11 or 12V) so that they don't immediately come back on as soon as your panel start recharging your battery.
What I'm going with in summary:
AEO WP50D $60
Renogy Wanderer 10A PWM Solar Charge Controller $20
50W Solar Panel $85
Miady 12V 6Ah LiFePO4 $35
--
Total: $200
Plan if I need more power, one more 50W panel and one more 6Ah battery. Which the 10A controller can still handle. I could even add the low voltage cut off and run the pump directly off of the two batteries in parallel for 24V. Lots of options for growth.
Disclaimer:
- I haven't put this all together, it hasn't even arrived yet, I just hit order while typing all this up
- I think all the power numbers are right, but my gut feeling is the battery is too small. I'd certainly welcome feedback if someone sees an error in my calculations.
When it's all said and done I'll try to remember to create a new thread with photos and such. Hopefully of a solar powered waterfall, but if not a different kind of waterfall, me crying into my pond over my failures...
