High-pressure (aka "true") aeroponics - nutrient schedule?

[QuentinQuark]

The pump failure issue is there with any system that uses a pump.

My point exactly. We can't talk about how expensive high-pressure aero is unless we do an apples to apples comparison.

I have a backup pump, at $70 its not much expense for peace of mind but if it was $200 i`d think about it more carefully as its a big outlay on a maybe (optimistic viewpoint).
I`m 100% certain an accumulator based system is less prone to pump failure simply because the load on the pump and running time is minimized. Unfortunately an accumulator wouldnt be as effective with a long misting cycle.

Atomizer, I'm obviously just in the research stages and so in no position to give you pointers as you are already successfully growing, but one of the reasons I was trying to pull this off with as few components as possible is because of a post that I read in one of Pod Racer's old threads about a guy saying that within a few days of one another, he had an accumulator tank die and then a solenoid die on him! I tried to go back and find the thread so I could link it here for you, but the bloody thread is 53 pages, and I can't search it because I don't have an account on that site. I have signed up for an account on that site but it takes 24 hours to activate. If I can search and find it I will find it and post it here. Again, not to convince you one way or the other, it's just good information for everyone to have.

I use bag filters instead of inlines because they have a large capacity, are cheap and washable. They don`t clog up completely without warning which can starve the pump of water.

Never heard of a bag filter, I'll have to look that up.

The normal filter size recomended for aero is 200 mesh (75micron).

A 200 filter is 75 micron! Crap, that's too big! Maybe I will have to get the nozzles with the individual filters... I will have to check out what micron size they are...

I use a coarse filter to catch large debris followed by a 20 micron bag. For the supply res, a 5 micron bag will remove pretty much anything that might cause problems to the pump, pipework or nozzles. Anything smaller than 5 microns with 95psi pressure behind it.. isn`t going to stay put for long

I'm not clear on where you put the 5 micron filter...

I use a small airpump to keep the supply and return res water moving, its mostly to prevent it stagnating rather than actively adding oxygen. When you have gallons of water stored at 95psi in a sealed accumulator tank for hours at a time theres no easy way of adding any oxygen to it

Lol ya I guess so... I am definitely going to use a chiller and get lots of air pumping, so I can maximize the D.O. and really crank those girls!

 

[QuentinQuark]

Ok, my account is activated on ICMag, but unfortunately I can't find that thread. Anyways, my point was that IMO it's better to have fewer distinct pieces, in that it makes it easier to have backup parts.

Like if all I have is the pump, then I just need a spare pump. But if one had a pump, accumulator tank, and solenoid, then one would need spares of all three of those things in order to sleep well at night!

Again, totally not trying to convince you Atomizer, I really appreciate your contribution to this discussion. Just sorta my approach to solving these kinds of puzzles I guess

 

[QuentinQuark]

Now regarding getting oxygen to the roots.

My idea was to keep the water nice and cool to maximize it's capacity to retain dissolved oxygen. On the old Pod Racer threads I was reading, they actually have some way of ventilating the root zone that I couldn't grasp.

Anyone have any thoughts on which way would be better? Higher DO in the water/nutes vs. ventilating the root zone?

 

[Atomizer]

Its good to try different approaches, if everyone did the same thing we`d never make any steps forward
The accumulator method works for me but pumps are more cost effective with long misting cycles.
If you want 1-5 second misting cycles you really have to go to water stored under pressure to get the fastest reponse. Accumulators last for years as there`s only one moving part.. a butyl bladder

 

[TheFaux]

Now regarding getting oxygen to the roots.

My idea was to keep the water nice and cool to maximize it's capacity to retain dissolved oxygen. On the old Pod Racer threads I was reading, they actually have some way of ventilating the root zone that I couldn't grasp.

Anyone have any thoughts on which way would be better? Higher DO in the water/nutes vs. ventilating the root zone?

T.A.G. is way cool! The chiller will take care of the dissolved oxygen, and from everything I've read, that's not a problem with true-aero anyway. All you gotta do is keep the roots (not just the water) at 68*F and you're good.

 

[Atomizer]

A 50 micron droplet holds a small volume of water (0.000295 mm3) so the water temperature isn`t too important.
The air temperature and humidity in the root zone are more important as they affect the lifespan of the droplets.
A 50um droplet in a 25C, 50% RH root chamber will live for around 4.5 seconds reducing in size as it dies

 

[TheFaux]

A 50 micron droplet holds a small volume of water (0.000295 mm3) so the water temperature isn`t too important.

1.) a 50 micron droplet of water is 100% water.
2.) Low temps are for checking pathogens and oxygen plays a big role in that department.... never heard of anaerobic bacteria?

I'd say that's pretty important.

 

[QuentinQuark]

A 50 micron droplet holds a small volume of water (0.000295 mm3) so the water temperature isn`t too important.
The air temperature and humidity in the root zone are more important as they affect the lifespan of the droplets.

I figured controlling the water temperature was the only way to control the root zone temperature, how else would you control it? My thinking was, the box is insulated (extruded polystyrene board), so 68F water = 68F root zone.

Am I not on the right track as to how to control the root zone temps? PLEASE don't tell me I have to keep the ambient temps in the room at 68F

A 50um droplet in a 25C, 50% RH root chamber will live for around 4.5 seconds reducing in size as it dies

What does that mean, what are the implications of this? Is this a good thing? A bad thing? Is this optimal?

 

[QuentinQuark]

1.) a 50 micron droplet of water is 100% water.

I don't think he meant that it isn't 100% water, just that it is a very very small amount of water.

2.) Low temps are for checking pathogens and oxygen plays a big role in that department.... never heard of anaerobic bacteria?

I'd say that's pretty important.

Personally, coming from DWC, I am thinking along the same lines, but to be honest I have never grown true aero before, and Atomizer has been doing so for quite some time, so I'm happy to hear his experiences and if I'm lucky, learn from his mistakes.

 

[Atomizer]

The res will need to be aerated as its a large body of water, small droplets have large surface area to mass ratio`s.. they absorb oxygen to the saturation point (dictated by temperature) extremely rapidly.
Unfortunately water temp wont necessarily equate to root chamber temp when you take into account the evaporative cooling effects of the mist. Its not easy to calculate as its dynamic being governed by the RH and temperature. To add a further twist these also change constantly as a result of the process

 

[TheFaux]

PLEASE don't tell me I have to keep the ambient temps in the room at 68F

75*F would be fine.

Unfortunately water temp wont necessarily equate to root chamber temp when you take into account the evaporative cooling effects of the mist.

He's talking about cool water being released into a cooler, right? If the room temps are at 75 and he's shooting chilled water at the roots there's no way he'd have problems unless he used an accumulator tank, no? Do you keep your tank inside a fridge? What kind of temps do you get at your nozzles?

 

[Atomizer]

I didn`t say he`d have problems..just that he shouldn`t expect the root zone temp to reflect the water temperature.
You don`t have to chill the entire res, all you need to cool is the water used for each misting cycle,which is about 855ml in Quentin`s case. My water temps reflect the ground temperature as both the supply and return res are buried.

 

[LiquidLumen]

You can get a 800GPH Active Aqua Pump for 60.00 retail. I know Texas Hydroponics sells them.

 

[LiquidLumen]

That last post was in response to Quentin's comment that a low pressure Aerop pump would run in the $150-200 range.

 

[TheFaux]

keep the roots (not just the water) at 68*F

the water temperature isn`t too important

all you need to cool is the water used for each misting cycle

Talking to you is like pulling teeth and I don't have the patience to deal with your ego. You gave me some good ideas though; thanks.

 

[Atomizer]

Thats a shame as patience is a virtue with high pressure aeroponics..best of luck implimenting the ideas though.

 

[hengis]

Great Thread. I really admire you guys knowledge.
I have a few questions which I hope somebody will answer

It seems to me aeroponics works very well and it doesnt really matter if you use a few second son and 20 off or 1 min on and 5 off or even on 24/7 all work. The question is is it worth the hassle going for high pressure and very short on pulses. Has anybody done a direct comparison.

2 I emailed dripwork in march re their misters as I did not understand how all these different flow rates all occurred at the same drop size I never got a reply that answered the question so I went for a much bigger drop size. It works but I dont know if it is near optimal. I did try a ultra sonic mister with very poor results although the drop size was very small.

Rather than experiment on drop size what about injecting pure oxygen to the roots a bit like CO2 for the green bits.

 

[LiquidLumen]

A direct comparison would be interesting...my take is I've seen amazing things with low-pressure Aero set ups that have 30 misters housed with PVC connected to a simple 500GPH pump, so why hassle with the extra complication and cost of high pressure? Just take a look through this forum and you'll see tons of beautiful plants produced from very simple aeroponic systems. I personally don't think it's worth the hassle just to produce smaller water droplets that can hold more oxygen. Even with relatively large water droplets, you're roots are getting an incredible amount of oxygen to the roots- especially compared to soil or other hydro systems. Motto of the story: if it ain't broke, don't fix it.

 

[QuentinQuark]

The res will need to be aerated as its a large body of water

ok

small droplets have large surface area to mass ratio`s..

ok

they absorb oxygen to the saturation point (dictated by temperature) extremely rapidly.

So the droplets are going to suck the oxygen out of my rootzone chamber, and jam it into my roots. But what happens after a couple of misting cycles, when there's no more oxygen in my rootzone chamber? Will bubbling in lots of oxygen IN THE RES increase the amount of oxygen in the rootzone chamber (it's sealed, not airtight but it's closed) ? Will it decrease the amount of oxygen that the droplets try to suck out of the rootzone chamber, because the droplets are already close to saturated because the res is cold and getting plenty of bubbles?

Unfortunately water temp wont necessarily equate to root chamber temp when you take into account the evaporative cooling effects of the mist. Its not easy to calculate as its dynamic being governed by the RH and temperature. To add a further twist these also change constantly as a result of the process

I have no issue if the rootzone is too cold, only if it is too hot. Let me rephrase my question: barring exremely unusual circumstances, would decreasing my res temps lower my rootzone temp, and vice-versa?

 

[Hammer of Dong]

I love the "true aeroponics" qualification. Just because you mist doesn't mean it's "true" aero. Aeroponics encompasses any hydroponics lacking a medium where the roots hang in the air.