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

 

[Carey Ma]

I use 220v AC here but my preference is 9 or 12 v DC. The only reason we use high current AC is to pump it vast distances. There is absolutely no reason for localized operations to use AC except for supplementary charging of ones battery banks.

[Steve Perreault]

I love my DC solar exhaust fan. It runs directly (no batteries) off a 65 watt solar panel. What's cool about it (pardon the pun) is that it turns itself on. It runs really hard when the sun is really cooking and shuts itself off at night. I'm planning to convert all my circulation fans over to solar. I picked up some nice car fans (this is the type fan you see on car radiators) off EBay for cheap. I just need some more panels and I'm in business. This is very simple system that's not too expensive since there are no batteries, charge controllers or inverters.

 

I suppose you could even run the pumps that way too if you were using a timed flood and drain system. With a bell siphon system (which I currently use and love) there is the possibility of leaving the growbeds fully or nearly flooded overnight. I would think that is not something most plants would like.

[the mad german]

Another pro for AC, I haven't researched the market on high volume DC pumps, but if 1 was to need high volume at extreme distances AC pumps have been made for jusy about every application.

Now I do have a high head DC pump I picked up on a job tear out that is DC. Its a 5 hp DC motor that pumps 250psi head (it was made to pump against city water pressure in a chemical injection system). Plus its on vfd, it only pulls 7 amps at max speed, I'll probably use or incorporate it if I ever build a large system. Problem being, if you were to buy this same pump and the controls you'd be at $4500.............I love being a pack rat.
Carey Ma said:

I use 220v AC here but my preference is 9 or 12 v DC. The only reason we use high current AC is to pump it vast distances. There is absolutely no reason for localized operations to use AC except for supplementary charging of ones battery banks.

[the mad german]

The attic fans you talk about are a great greenhouse exhaust also. Completely temperature controlled, plus here in the states you an get a tax credit for them.

Steve Perreault said:

I love my DC solar exhaust fan. It runs directly (no batteries) off a 65 watt . What's cool about it (pardon the pun) is that it turns itself on. It runs really hard when the sun is really cooking and shuts itself off at night. I'm planning to convert all my circulation fans over to solar. I picked up some nice car fans (this is the type fan you see on car radiators) off EBay for cheap. I just need some more panels and I'm in business. This is very simple system that's not too expensive since there are no batteries, charge controllers or inverters.

 

I suppose you could even run the pumps that way too if you were using a timed flood and drain system. With a bell siphon system (which I currently use and love) there is the possibility of leaving the growbeds fully or nearly flooded overnight. I would think that is not something most plants would like.

[Steve Perreault]

Actually, most DC (or solar) "attic fans" have relatively low CFM compared to AC fans and most people would be disappointed in their performance as I was. I bought and returned 2 solar attic fans before I found the 16 inch Snap Fan I have now. It's rated at 750 CFM at 12v and 1800CFM at 24v. It costs a little more. But it's definitely worth it. My GH is 10 to 14 degrees cooler now.

 

I didn't bother with the tax credit since it was for a GH. I assumed that the credit only applied to home use. Please let me know if that's not the case.
the mad german said:

The attic fans you talk about are a great greenhouse exhaust also. Completely temperature controlled, plus here in the states you an get a tax credit for them.

Steve Perreault said:

I love my DC solar exhaust fan. It runs directly (no batteries) off a 65 watt . What's cool about it (pardon the pun) is that it turns itself on. It runs really hard when the sun is really cooking and shuts itself off at night. I'm planning to convert all my circulation fans over to solar. I picked up some nice car fans (this is the type fan you see on car radiators) off EBay for cheap. I just need some more panels and I'm in business. This is very simple system that's not too expensive since there are no batteries, charge controllers or inverters.

 

I suppose you could even run the pumps that way too if you were using a timed flood and drain system. With a bell siphon system (which I currently use and love) there is the possibility of leaving the growbeds fully or nearly flooded overnight. I would think that is not something most plants would like.

[TCLynx]

I definitely like the idea of solar power, wish I could justify the expense for it at the moment at least to charge up my battery backup but ya do have to pick and choose sometimes.

 

Now I don't personally have anything against DC stuff on principle.  However, you have to look at your specific application and the flow rates and head needed and find the appropriate equipment for your particular situation and compare your options to see what will actually be the most efficient and appropriate to the situation.

 

I do have a couple of those little solar fountains (like from harbor freight) that run direct from a solar panel when the sun shines on them.  I will warn that these are not enough to support an aquaponics system, at least not one big enough not to cook the fish by being in enough sun to operate the pump.  And fish need aeration at night as well as during the day so even if the plants don't mind the pump shutting off at night, the fish could have problems if there are many of them or the water warm.  Case in point.  I had to set up a pond plant pool on short notice this summer and I placed  a couple of the solar fountain pumps in it along with the pond plants and 4 small fish to take care of mosquitoes.  Things were fine during the day while the sun was on the solar panels and the plants were supplying extra dissolved oxygen but as soon as the sun was starting to go down the poor fish were all gasping at the surface since as it gets dark not only did the pumps stop running but the plants start using dissolved oxygen right along with the fish.  So I'm out there at dusk in a rush to set up a mains powered pump for aeration to keep the fish from karking it before morning.  Now perhaps during cool weather this might not have been such a problem but warm water doesn't hold enough dissolved oxygen.

 

For my original battery powered backup aeration I had wanted to buy a 12 v dc air pump but the one available wasn't really big enough for my application but still used about as much electricity as an AC one that was big enough to provide enough air so I wound up going with the AC air pump plus inverter for the job.  This also allowed me to set things up with a relay to run the air pump on mains power when there was power available and it will switch to battery power when the mains power shuts off.  So I guess the lesson here is to do a bit of extra research to figure out what is best for your situation with the equipment you can get instead of automatically assuming that a DC pump will be more efficient because you don't have to mess with an inverter.

 

I will also mention that an inverter can be a real weak point so I'm not automatically saying they are better either.  I've had to replace two of them.

 

Pay close attention to the environment you will be subjecting your electronics to since that can really affect their lifespan.  My garage where the battery backup system equipment lives can get quite warm so I needed to shop for an inverter that can handle higher temperatures to finally get one that might last a bit better.  I have also had control electronics fouled by bugs and heat/moisture is also a likely problem for many electronics near an aquaponics system.

[the mad german]

Cost is a huge factor when 1 considers it, fortunately for me I can get batteries all day long and scavenge parts from my job.

So my only cost was the panels themselves which are getting cheaper every year, kind of 1 of the holdups with the entire solar PV movement.

The other problem is application, even if someone was to build or design a setup like mine, in most cases people don't understand the entire dynamics of their application. 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). They were free and it is overkill, but it allows the excess wattage to ensure that these monsters will always be charged. Which means 2 important things which are detrimental to a 12v motor that wasn't designed for solar. I'll always have the proper voltage and current for at least 20 continuous hours of running or cycling at the current rate with no sunlight for 6.5 days. But even then on cloudy days a panel will still put out 10-20 of their capabilities, so I'm still pretty much covered.

The other issue is the bilge pumps, unlike the solar pumps or solar attic fans they weren't designed for solar. They were designed for a constant 12v. The problem occurs when they either no longer have the the voltage or have the voltage but not the current. Then the motors tend to heat up like a heat sinc. Eventually breaking down.

Then add in the fact that a solar panels voltage can be anywhere from 18-36 volts. So unless 1 is using batteries and going through a charge controller which regulates the voltage to 12v.....the problems of burned out pumps will persist.

Kind of why I brought this whole issue up with the DC applications, I think alot of people think they can just buy a panel like they see with the solar pond pumps hook it and wallah,...Its not quite that simple.

Same thing goes for the inverters, unless you have 1 that shuts off or alarms when current or voltage is low they tend to burn out, being that you're still drawing current at an under voltage scenerio, which is  why I chose to use the monster batteries that I did. Right now I'm not using an inverter but probably will for a fishtank heater, but even then my panels and my batteries won't be enough.

It definately isn't a cheap or cheaper solution, For me it works out being I wanted the capability to move my system anywhere on the property and not have to worry about running or stringing extension chords.

Then theres the issue of solar degree days for your area which comes into play for sizing.

As far as your solar air pump, myself I haven't seen many big ones myself short of using an air compressor, then 1 would need a huge solar panel setup and charging system, I definately concur on an AC pump/bubbler/aeration

I also whole heartedly agree with you on the equipment environment, Even in AC applications I think people fail to see heat/moisture/insects etc can be a problem. When people do purchase their equipment they need to look at the temperature ratings of the equipment. Any and everything with an electrical rating also has a temperature rating. So in these days of intense heat, most equipment will be operating outside of their design specs which causes, stress, heat buildup, higher current draw and equipment break downs.

Thanks for the added input, just a few more things for people to consider on any application.

[the mad german]

Sorry I thought you were just chiming in on your happiness of a solar product, wasn't aware it was for the greenhouse. So no I actually wouldn't claim it, but then again the wording does say solar attic fan for your house, Your greenhouse is a house and you are using it to free up the grid......but I wouldn't push the envelope with the IRS.

Steve Perreault said:

 

I didn't bother with the tax credit since it was for a GH. I assumed that the credit only applied to home use. Please let me know if that's not the case.
the mad german said:

[George]

http://www.reuters.com/article/2011/12/20/us-power-acdc-idUSTRE7BJ0...

[the mad german]

Good article,

A lot of places as far as manufacturing, building automation are going to frequency drives for energy efficiency to back off when demand load is not there. Theres a trade off as far as the conversion goes, but when you save 10-40% when not under peak load or demand for production, HVAC or building automation, the savings does pay back. Nowif the manufacturors would come down on their equipment cost it would be more feasable.  The LEED certification process is 1 way this is being utilized.

A lot of houses now days use multiple speed blowers for their HVAC systems, they always have used 2 speed for absorbtion and heat transfer purposes, but I am surprised freak drives on home heating cooling systems isn't being utilized or mass produced. Most times the problems with development like that is, electrical engineers have no understanding of heat transfer and absorbtion rates of refrigerants, so it would probably take a bit more programming then just a basic PLC..........something I would love to be involved in as far as the design goes.

 

But good article
 
Geoge said:

http://www.reuters.com/article/2011/12/20/us-power-acdc-idUSTRE7BJ0...

[jdmeetze]

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]

How about AC, DC, both or neither?

I'm using solar to batteries to inverter to pump but at some point may add a clean water sump, pumping to towers and possibly I'll use a straight 12-volt for that application.  In my situation, it will entail running 20 feet or so of wire from 12-V battery to pump - can you tell me how much loss will occur between battery and pump?  I've always heard that is one of the drawbacks of 12 volt.