In an aquaponics system, backup really only is needed for the fish tank. The fish will suffocate after about 30 minutes without continuous oxygenated water. I have a 60-watt AC air pump to accomplish this when there is a power outage.
I consulted with a local solar provider about setting up a system that would charge a battery or battery bank that would supply AC current through an inverter to run this pump if the power goes out. I suspect that the system might also need a switch to dectect when regular power fails and initiate use of battery power. To be on the safe side, I would like enough a battery capacity to run the air pump for 12 hours (720 watts?) However, I do not need this capacity every day, but only when the regular power goes out.
The solar provider has given me a quote for a system that costs almost $1,200. This seems outrageous to me, particularly given the fact that the air pump only cost me $50! The inverter alone is $544 (with tax):
MAGNUM INVERTER MM612 600W, 120VAC,12VDC, Modified Sine
SSEALED BATERIES (2) 12V-100AH are $376.
The rest is cost for cables and connectors and labor.
They did not recommend solar panels to charge the batteries. Instead, they said they we could use regular electric to charge them through the inverter.
I am writing here for a second opinion.
A standby battery charger and a battery bank would work if you switched to a DC pump.
For what it's worth, that price for a 600watt 'modified sinewave' inverter seems a little high. The total cost is ridiculously high.
Really to do what you want, all you need is an UPS (Uninterrupted Power Supply)
A computer UPS with an external battery would work just fine and would cost a lot less. You can add external batteries to almost any UPS, but it works best if you use an UPS that is intended to work with external batteries.
Duracell 225ah 6v golf car battery (quantity 2) $115 each.
$125 battery cables and fuse.
About $650 a solar pane and charge control will keep your battery healthier over time, as the inverter charger is not as adjustable.
This rig would work just fine.
I also have been thinking about other solutions in case the UPS route does not work for me. The first is to question whether I actually need a 600 watt inverter for the task. The water pump is 92 watts/120 volts. The task is to maintain 2 deep-cycle batteries fully charged in the event that there is a power outage. A 600-watt inverter presupposes a 1:6 surge capacity is needed to accommodate the switch from grid power to the batteries. Information that came with the pump does not address surge, so I have written and asked them. Of course, I do not even know if there will be a surge when the source of power switches from the grid to batteries.
In any event, a 600-watt inverter seems extreme for the job. However, I am a newbie and I could be way off base on this.
A good ups will switch so fast that there will be little to no surge and most inverters can handle a surge up to 2x their rated output.
I suspect he recommended a 600 watt inverter because that is the smallest one he carries that comes with an automatic transfer switch. I think the smallest computer UPS I've seen is around 350 watts.
Yes a computer UPS might have problems with a larger battery pack, that was the main reason I mentioned using one design to work with an external battery pack, they are more expensive but would require the least amount of tinkering on your part.
If you are using an UPS that is not designed to work with external batteries, then you could just add a separate battery charger to help it out and maybe a blocking diode so the UPS can draw power from the external batteries, but can't charge them. The external charger could even be a solar charger if you wanted.
The link posted by Frank above might also be a good option. I'm not very familiar with that brand though, so I can't say whether it is reliable or not
If however, the solar panels plus batteries are the first steps in a fledgling solar setup that will do more than power the pump, then an inverter will be handy, but in agreement with other posters, the prices you have been quoted are ridiculous.
Steve Mendez wrote:Since this is for occasional, mostly intentional power outages, maybe the simplest and least expensive solution would be a bottle of oxygen with a regulator and a solenoid switch that would open when the power is interrupted. The oxygen would be added to the fish tank through an inexpensive air line hooked up to an airstone.
Yes, i did spec the inverter based on the fact, it was the smallest and least expensive inverter that has an integrated transfer switch. Also its samlex, so decent stuff.
You could probably use a 200w or less inverter, but by the time you add a transfer switch and proper charger, the cost would be way more.
600w may be a good thing.... people are so unsure that they immediately suspect they might be suggested something foolishly more than what they need.
I wouldnt focus on the 600w part as much as the fact that it offers headroom for other loads, does not ride max output, does not consume inordinate power on standby, has an automatic charger and transfer switch in one box with terminals that lend to ease of set up and takedown and is also upgradable, does not require solar and so keeps the pcost down to half or less over the quote you have.
The equipment suppled on the quote looked good, magnum is good equipment and solar means you do not need to carry fuel or have it delivered as electricity and a load on your farm goes appropriately to a renewable source.
If you are unsure about "modifying" a ups, and id imagine a ups with a battery that can run your gear for as long as a 12v 225ah deep cycle battery and inverter combo would be quite a bit more expensive you can get an inverter as small as you want, but it will still add up to more cost when all the other bits are sourced.
The exception would be, stuff you already have on hand and custom built automation gear...Most office store ups systems are only good to operate a desktop for a few minutes to a half hour.
Actually even inexpensive ups boxes are about $100 per half hour or so to run your pump...
Pressurized air is nice, transporting it and having 3500 psi hoses and fittings to maintain could be another story, plus a tank and regulator and controller is how much, and lasts how long?
I like the dc pump idea.... especially if there is no tolerance for wasted inverter nameplate watts!
You could get a marine deep cycle battery and a dc pump, charge it on a garage shop charger periodically replace every other year, while crossing your fingers for run time and frequency of outages.... thats expensive too!
Fuses are overated, speaker wire works fine for battery cables and i saw an old ups in the garbage, if i find 10 more and scrounge some scooter batteries, that would be cheap too.
I do not sell anything here, never have, never will. I am an installer who owns and operates my company and believe me ive heard alot of these qualms over the years. People will spend $1000 on entertainments and not bat an eye long before the same on power equipment and way before they are convinced that the only thing i prescribe is what will work, not what i can sell. I have no interest in it, if it does not work, work well and is not made of the good stuff.
If you look, you may be able to find a comparable ups or ready built unit.
$600 again. No wires, mounts or fuses. 200w solar, 100w inverter, 220ah 12v battery, 20a solar controller, transfer switch, no grid charger.
Could be done a little cheaper, but its pretty basic. Places to save money, pv controllers can be had for 20$, you could half the solar size if the outages are a week or more apart. The battery could be smaller, but this will run two 8 hour cycles at 50% dod and one at 35 degrees ambient temp.
Sometimes more costs the same as long as you are opent to the idea of more.
You could place an automatic battery charger on a couple deep cycle marine batteries (golf car preferred same cost), dc air pump and a 100w solar panel and get the cost down to around 3-4 hundred.... maybe, lots of shopping but it would work as a solar system with grid backup with the lowest cost and highest reliability.
100w solar may take 2 days to a week to recharge charge depending and having a grid charger as a supplement and backup means as soon as the power is back on, you are recharging to be ready for an outage as soon as possible. Also, the solar capacity and the charger can be smaller with both rather than singularly but the battery is a good size.
And these are good for dc to dc.