AC, DC or neither

[the mad german]

TC brought up an interesting point on my solar aquaponics thread,about his like for his AC system.

So lets hear what you like about your application. Is it AC, DC  a bell siphon that uses no power or other?

I don't view this as an "us versus them" arguement or discussion, But rather a pros and cons of all types of systems for the pumping of water, heating and lighting that each individual might need to consider when starting or expanding an AP system.

So lets hear what you like about your sytems. This might even be useful for some of the resident pros on here that give seminars on AP systems discussing the pros and cons to their respected or prospective clients as to the considerations of what they want to achieve or how.

i'll go first, now remember this doen't make my system better in any way...it just happens to suit my application and works for me.

Pros,what I like about my system is 0 electrical cost, Recently I went out of state for 6 days and thought for sure everything would be dead or dieing when I got back, I haven't built an automatic feeder so I had a friend drop in to feed the fish every other day.

I never have to worry about a power outage. The DC bilge pumps are dirt cheap, If my batteries go dead or bad I have plenty more in storage, Electrocution is severely lessened with low voltage DC and water.

I use a float instead of a timer for water level and exchanges to cycle my DC pump motor.

I built it for applications where there is no power being somewhat of a survivalist.

Cons, if you were to automate with a computer you would need AC for a computer, the controls for automation are mostly AC and need an inverter, for heating AC is quicker and more responsive, An inverter would be needed which steals 5% minimum from the DC to convert to AC. For applications with major amp draws you would need a lot of solar panels which are costly and lots of batteries.

Additional space, time and cost are huge factors when setting up a DC application. Most Ac equipment isn't a specialty item and can be bought the same day at a local hardware.

 

Anyways, just some thoughts to ponder, and am looking forward to others input about their likes and dislikes or pros and cons of their systems

The mad german

 

[TCLynx]

Going 12 volt DC you want to use as large a wire size as possible to minimize loss.

[Matthew Smith]

Hello The Mad German,

I'm The Mad Frenchman and I am planning on building a DC system next spring here in southern France. Could you give me any pointers on what size solar voltaic system I'll need for a CHOP II system following Murray Hallam's design using three 1,000 Liter tanks?

I've built a 20 square foot greenhouse and I have the tanks so that is all ready to go. I just don't know how realistic it is to run the system off grid and I don't want this project to become a cash sink.

A friend of mine says he can supply me with a 250 watt solar panel for a reasonable price and I have a local source for car batteries. I am hoping to find some DC bilge pumps online. My greenhouse is far from any electrical outlets and we have regular power outages so I prefer to have in independant system. Any suggestions?

 

Thanks very much for any advice you have!

 

Matthew

[TCLynx]

Get a bigger greenhouse, I don't think you are going to be able to walk into the greenhouse let alone tend the plants or the fish if you manage to get 3 IBC's into a 20 square foot greenhouse

[Matthew Smith]

Oops, I meant 20 square meters...

 

Thank you though!

[George]

I hope MG will respond in some detail but you can probably expect to need several of the 250W panels and car batteries will not be very good for your application.  You will likely need deep cycle batteries, such as marine or golf cart batteries.  Panels and batteries are expensive.  That being said, you will probably want to have a battery or batteries for backup, regardless of whether or not you use solar.  I tried to run entirely from solar but have now decided to use the solar system for redundant aeration and to backup the grid.  Good luck.

Matthew Smith said:

 and I don't want this project to become a cash sink.

[George]

I'm no electrician and not a mathematician either, apparently.  I had to read this several times over several months to understand how to determine battery charging and battery drain.  Thank you.

the mad german said:

 Mine uses about 180 watts an hour 12v x 1.5 amps x 10 times an hour is my wattage consumption, so the other 50 minutes my charging input is 12v X 2amps X 50 minutes or 2400 watts an hour. So battery capacity is just the other side of the coin. Being my batteries are so way oversized (2 x 1200cca x 12v and I've got 28,800 watts available on standby).

[Bob Campbell]

I'm wondering if an air pump could run off a UPS with the battery charged as needed in the event of a power failure from a solar panel with a charge controller.   This is a little different than your setup, but it sounds like you might know a bit about this stuff.  I asked about this at a retail store that sells API UPS systems, but the salesman was hesitant to say yes.  Seems simple enough to hook the charge controller to the battery, but maybe I don't know enough about this.

jdmeetze said:

I have never built a solar aquaponic setup before but I have built solar computer setups. The one I currently have on the lanai is a tiny ARM pc running linux for gathering weather data. It has a small $30 solar cell from a box store wired into a freecycled UPS gel 12v battery. I am using a cheap $9 charge controller (next time I will build my own). The entire setup out of the box on first test (after a full charge cycle) lasted a little over 170 hours on high power on battery only. Low power it would perhaps reach a full 7 days on battery only. Not bad for something that retail would only cost a total of $250 in parts. Hmm that gives me an idea...

[George]

You could run a 12-volt air pump for a long time from a lawnmower battery (or deep cell) and charge as needed from an automobile, panel or generator.  12-volt air pumps are more expensive than 110V but you wouldn't need an inverter during power outage.

Bob Campbell said:

I'm wondering if an air pump could run off a UPS with the battery charged as needed in the event of a power failure from a solar panel with a charge controller.  

[TCLynx]

Biggest drawback I see with doing a 12 backup is you then truly need  to either beef up your solar and battery capacity to be able to run full time on the solar/battery system.

Or you have to have the stuff to power the 12 volt air pump from the mains power and a means to switch it over during an outage.

Or you need to run both the 12 volt DC for backup AND a 110 V AC off mains power for when power is working AND some means to switch the DC system on only when the mains power is down.

Having a battery on float charge hooked up to an inverter that can send power to the regular 110V air pump via a relay only when mains power goes out seem the simplest system to me, though it is only simple if you are talking one system with one air pump.

[George]

110V equipment running from 12V batteries really takes the batteries down quickly.  What I intend to do during an outage is stop feeding (1) and (2) run system pump from batteries maybe 3 times per day for an hour while 12 aerator runs continuously.

[TCLynx]

How will you have the 12 V aerator turn on when the power goes out?  A relay with a wall wart or something?

I've had a moderately stocked system do fine for over 24 hours just on aeration when a power out happened while I was away.  Definitely no feeding when on backup.

[George]

I leave the 12V on all the time and it will continue when the power goes out.  Switching to 12V for grow beds water filtering will be manual at this point.