Progress, and a Failed Experiment

Today I was able to procure many additional materials: plywood, polystyrene panels, 2x4s and 4x4s, plus some plumbing supplies for further experiments.  I assembled the three grow-bed support frames.  I had to obtain a larger container to carry out the siphon experiments.

As I had mentioned in my last post, I had a crazy idea:

A miserable failure - do not repeat it!!

Yes, this is a two-stage inside the same bell.  IT DOES NOT WORK.  This is why I take notes on these things...it's just too bad I didn't actually re-read them before attempting this hair-brained idea.

Why does it fail?  The small red pipe feeds directly into the large main pipe.  There is no way enough water can flow into that massive blue down-pipe to form a siphon, therefore the siphon simply never forms.  What made the original 2-stage experiment successful was that the starter siphon formed a full and fast siphon. With the additional water being pumped into the larger out-piping, there was sufficient volume to start the larger siphon.

That is not the case with the above illustration.  What you see above is simply a slow flow into a very large pipe, which would happen even without that extra red pipe sticking out the side.  Without an actual siphon forming with the smaller pipe, there is insufficient water flow to trigger the main siphon.

Some other bad points about the above design: it's huge, it requires a very large diameter bell (which equates to an even larger media guard - bleh), it doesn't work (as previously mentioned), it requires many more fittings than its worth, and so on.  I will be trying some more experiments soon.  Namely, I want to see if a 3/4" starter siphon will trigger a 2" main siphon.  If it does, my next experiment will test two 2" main siphons with the 3/4 starter.  I can also modify the diameter of the out-piping, to help ensure the flow is sufficient to trip the other siphons.  The catch is that the smaller the out-pipe, the less flow it can handle, so there may cease to be a reason to run 2" siphons.

Bulkhead Fittings and Siphons

I have purchased a small selection of bulkhead fittings from US Plastics, an online supplier of those and evidently a large variety of other plastic-related items.  I am currently gearing up to procure another round of supplies, at which point I will be very close to the point of being able to fill the system with water.

Since I had to purchase fittings, it seemed like a good time to do some calculations and make sure I was sizing the plumbing appropriately.  I assume a pump rate of 800 gph (it's a 1000 gph pump, but I am attempting to account for head loss).  I can't seem to find the calculations (they must be in another spreadsheet), but for the moment I am assuming that the media will occupy about 30% of the GB space.  The GB's max operational capacity is approximately 100 gallons.  Thus, we will suppose 70 gallons will filter into the GB before the siphons start.

Given the above, the anticipated static fill time (the time it takes to fill completely before draining starts) should be about 315 seconds.  A 1 inch diameter drain pipe should pull the water out of the GB in about 200 seconds.  Figure in the constant fill rate, and the drain time jumps to 547 seconds (we'll call this the dynamic drain time), meaning it would take far longer to drain than to fill.  At 1.5 inches of drain diameter, we should expect 124 seconds of dynamic drain time.  That's better.  At 2 inches, it should drain all 70 gallons in about 59 seconds.

Now, I can only cut these holes once, and I am slightly concerned that the length of the bed will cause one side to become more stagnant than the other, should I place the drain in one corner.  The alternative is therefore to add a second drain.  Two 1.5" diameter drains equals one 2.12" diameter drain in drain area, so the dynamic drain time would be around 52 seconds.  Two 2" drains (equivalent to one 2.83" diameter drain) will reduce the drain time to 27 seconds.  These times do assume sufficient out-piping, which means I would probably need to enlarge at least a portion of the pipe running down to the DWC.

Whether or not I really need the second drain is up for debate, but by at least installing the bulkhead fitting now, I can always add the actual drain later (and otherwise just plug the hole if it need not be used.  If I do go with the larger size pipe, or two of them for that matter, I will very likely need to contend with a siphon start issue.  Thinking back to the pull-start siphon I experimented with several months ago, I decided it might be good to find a way to build that in.  Putting two bulkheads next to each other, however, did not seem like a good idea, and the loss of GB real-estate was becoming bothersome.

One potential solution, which I will be experimenting with as soon as the fittings arrive, is to put the start-pipe assembly above the bulkhead, rather than below it.  In concept, there would be only a single pipe and single bulkhead fitting.  The pipe would tee immediately above the fitting, and proceed up at full diameter and out at the start-pipe diameter (1/2" most likely).  The start pipe connection would do a bend and then run parallel to the main drain, terminating just below the top of the main.  The start pipe would therefore set the max water height in the GB.

Two siphons should not pose any special difficulty, as long as they are drained together.  If the main (pull-started) siphon is closest to the out-pipe, and the secondary siphon connects into it just before the out-pipe, the secondary siphon should get pull-started by the main siphon.  That is, once the main siphon trips, it should pull sufficient vacuum on the drain plumbing to forced the second siphon to start.  The effect will be a three-stage drain: start, primary, secondary.

It may be better to put the primary siphon upstream of the secondary, but my only concern is that the long horizontal run will cause problems for primary siphon start.

Regardless of how the siphons are started or how fast they flow, this action has an effect on the DWC tank:  given the dimensions of the DWC, a 70 gallon ebb-and-flow will equate to approximately 5.6" of rise and fall.  Consequently, the pump will need to gather water from as close to bottom as possible.  It should be noted that this height changes is slightly more than 50% of the maximum water height for the DWC.  Should it be determined that less water is required in the GB to trip the siphon, then this percentage will be reduced accordingly.  (For instance, a 50 gallon ebb-and-flow will equate to a 4" rise and fall.)

I plan to position the water pump outside the DWC, piped so that its inlet it always submerged.  I may need to find a decent filter material to keep debris from entering the pump.  One of the bulkhead fittings I acquired is intended to go through the wall of the DWC.  This is mainly to ensure that the pump can be properly primed before starting, as it is not self-priming.

Testing will hopefully commence soon!

Lighting Research - Preliminary Studies: White versus Red/Blue

I've been doing quite a bit of reading about the lighting requirements of plants.  I'll provide some details on my findings, plus references, in another post.  For now, some notes.  My goals are to build LED lighting assemblies that will provide adequate and appropriate light for my plants.  As there will be a variety of vegetables, plus fruiting plants and hopefully some root-plants, the lighting must be able to accommodate them all.

I investigated HIDs and fluorescent fixtures, and ruled both out as too costly in terms of setup and upkeep.  The former are power-hogs.  The latter's bulbs reportedly lose value after 6 months and require replacement.  LEDs to the rescue, then!  But, it's not so simple.

Firstly, manufactured LED assemblies are horribly expensive.  Second, the majority of them are red-blue fixtures.  Some also incorporate green.  I did a great deal of search about the best growth spectrum, the typical spectra for chlorophyll, and eventually found myself on a very detailed site regarding photobiology.  Here's what I have so far...

Chlorophyll-1 and -2 do indeed absorb rather specific portions of PAR light.  One takes the majority of its energy from around 450nm, the other from the 640nm area (very roughly, don't count on those numbers AT ALL).  However, their precise absorptance spectra depend on the solvent in which they are dissolved, if considered in vitro.  When one considers the effects of PAR spectra in vivo, it has been observed that a very wide range of the 400-700nm wavelengths are indeed absorbed.  These are not necessarily absorbed by the chlorophyll itself, but could be absorbed by accessory pigments and other chemical processes within the plant.  Furthermore, the presence of other proteins and chemicals either attached to the chlorophyll, or within close proximity to it, will affect (sometimes to a great degree) the spectra that the chlorophyll can and will absorb.  We cannot rely on in vitro data alone to build our lighting, as it does not accurately characterize the actual operating conditions of chlorophyll.

Some plants also make specific use of the far-red region of the spectrum.  This is evidenced by phytochromes, namely Pr and Pfr (for the red and far-red spectra).  The two convert to one another in the presence of the right light, and if I remember correctly Pfr converts without light input to Pf.  The relative quantities of these two phytochromes determine the expression of certain traits, such as the straightening of plant parts.  But the key take-away is this: we cannot alone rely on the spectra relevant to chlorophyll to determine the appropriate lighting.

Given that this will not be a monocrop, and given that the sun's spectrum in the PAR region is generally flat (as apposed to the spiked spectra for chlorophyll-1 and -2), it becomes evident that focusing on only the blue and red spectra will not be for the best of the plants.  In other words, white light with a fairly even spectral distribution will be the optimal light, with what limited information I have about the goings-on inside the plants themselves.  While it will certainly be sub-optimal from the point of view of chlorophyll - that is, I am technically "wasting" power on light that isn't immediately absorbed by the chlorophyll - it will also be the kind of light the plant has evolved to expect.  Given the number and variety of inner-plant processes that we either do not know, or do not understand, it is possible the spectra-restricted (red/blue) lighting is itself deficient, and therefore wasteful.

Many questions remain:

• How much light, in terms of PPF per day, will the plants require?
• What will happen if too much light is provided?
• What will be the best LED light source for the spectra chosen?  Will I need to augment that spectrum with additional, spectra-specific LEDs?
• That is, most of the white LEDs I've surveyed to-date (all from Cree), tend to show dips in the spectrum after blue, but before yellow/red.  This probably means emission of the green spectra is greatly reduced.  I would have to compensate with additional green LEDs, but only if that really matters in the end.  It's possible it does not.
• What should be the minimum and maximum distances for the light sources from the crops?
• On the DWC, there will be no choice
• Will the even, consistent lighting prevent fruiting?  If so, will it be necessary to implement additional lighting (in specific spectra) that can be triggered on an as-needed basis?
• If spectra-specific lighting is required for fruiting, will it cause non-fruiting plants to bolt?

The math also looks like it will be fun.  Lots of 10-to-the-very-large-number exponents.

Updated Layout, Electrical Draft

So here it is, an updated layout with an IBC for better representation, and the latest incarnation of the GB+DWC setup.  The reconfiguration of the grow structure has allowed me to regain some space closest to the patio doors.  The electrical run is shown in pink.  There should be about 15" between the grow structure and the step that leads up into the patio door, meaning there is more than 15" between the structure and door itself.

The area on the floor in green is more than 2 feet away from any wall or barrier.  The yellow areas are within the 2' range.  Thus, I can move the grow structure even further away from the door, though not terribly much more.

I have yet to spec the actual components for the electrical.  Right now I need a minimum 3 outlets, all GFCI-protected.  I am thinking of putting a main cutoff on the left, on the pipe run originating outlet box (the grey box lowest to the ground to the left of the door).  The outlets will need to be wet-location protected.  I would also like to integrate a timer into the build, for the lighting.  I have one which isn't being used - it used to run the pool pump (but the pool is gone...for now).  It would fit nicely in on the left or right.

I'll also have to see how much wire each of the electrical appliances comes with.  The water pump should be no problem, I think it came with a ton because it's submersible.  The air pump, on the other hand, may be another story.  That said, I will need to experiment with the length of the air hose to see how it affects pump efficiency.  If it's not terrible, I might be able to store the pump close to the outlets and run longer air lines.  One way or another, I'll have to come up with a way to protect the air pump from the elements.

I am currently in the process of researching LED lighting options.  It looks like a DIY build will be required, if I want any reasonable amount of light output.  That said, I'm not sure how much light I need.  There's only indirect light back there, so some direct LED is a minimum requirement.  Having it be DIY also means I'll need to properly store and protect the LED drivers and any power transformer equipment...gaaah!  IP66 anyone?  Perhaps rated fixtures are not such a bad investment after all...especially if I could find some on eBay.  Or perhaps I should build or attach a weatherproof box to the back of the grow bed?

If you're wondering why no HID or fluorescent, I simply don't have the headroom for the lower tank, and really not for the upper tank either.  I'm not even sure how I'm going to mount the LEDs for either.  But an LED bar should be no thicker than a T5, when it's completed and mounted, and should put out significantly less heat.  Moreover, and the main reason, it should cost significantly less in power.  That's a big deal.  That, coupled with low voltage (always a nicety around water) and the potential ability to encase a good portion of the electronics in epoxy (waterproof!!), makes LEDs very attractive.

Modeled, but not shown in the picture above, is the sloping porch ceiling.  The long horizontal electrical pipe running over the patio door is situated just below where the ceiling meets the wall.  That's also the highest point for the ceiling, so perhaps you can appreciate the headroom situation.

Grow Structure Design Update

On and off over the last couple of months, I have been toying around with different ways to support the grow bed and DWC/sump.

Various ways to put the GB on top of the DWC.

 There are two key problems I have to solve:

1. The bottom of the grow bed must provide sufficient clearance to allow both functional DWC access, and to ensure the DWC lighting will not be too close to the plants.
2. The patio where the system is to be located has a very unfortunate slope: approximately a 1 5/16 inch drop over an 8 feet run.

Point number 2 provides a most amusing problem.  The DWC tank is 8 feet long.  Left unchecked, one side of the DWC tank (and, of course, the GB) will be 1 5/16" lower than the other.  Since the pump will be located on the high-side of the tank, this is no bueno.  I have toyed with some options for dealing with the slope.  The first, and so far still the best, is to cut several ramps that will act as combination joists-and-slope-correction.  Another alternative was a set of wedges, cut so as to be placed at regular intervals along the bottom of the DWC tank.

Mounting the GB above the DWC is also an interesting challenge.  As I mentioned above, the DWC needs to remain accessible.  I figure I should keep a minimum 12" between the top of the DWC and the bottom of the GB supports to ensure good access (meaning I can get my boards in and out, with large plants, without crushing or destroying anything living in the process).  To complicate things, I also cannot have the GB situated too high, or it will become difficult to plumb it and to access it during actual operation.  Due to the slope problem, the DWC tank will also be situated slightly off the floor, thereby reducing the already limited clearance between the DWC and the GB supports.

Another goal is ease of build: I don't want to mortise if I don't have to, as it's a PITA.  Considering the weights involved, I also don't want anything potentially compromising the precision of the legs.  My calculations put the DWC tank weight around 1,000 lbs when filled.  The GB will probably be in that ballpark, as well.  Much of the GB's weight will depend on the weight of the media.  I'm planning on going with Aquarocks: a sort-of Hydroton alternative, where if Hydroton and lava rocks got together, Aquarocks would be their baby.

As if this all wasn't enough, the patio slope presents a bonus problem: the legs of the GB stand will be tilting by approximately 0.8 degrees.  Over the 3.5" width of the leg, this equates to one side being a little more than 1/32" higher than the other.  If the legs are 30" long, the top will be displaced by roughly 0.41".  Lateral force due to the 1,000 lbs load should come to something like 13 lbs, so it will be as though there is someone pushing against the legs with 13 lbs of force at all time.  Now that I have that written thus, I may be reconsidering my plan to not slant the feet of the legs.  My only hope - and perhaps I should check a physics book on this - is that the load will at least be distributed among 6 legs, so 2 lbs lateral force per leg.  Also, given that there will be 998 lbs of downward force, perhaps this is really all moot.

Here's the current draft plan, plus a look at how the tote squeezes in on the patio:

The build: notice the purple slants.
They're there for a reason.

Large, beastly recycled IBC tote, located where it needs to go.

The one problem with the tote is that it forces the "near-end" of the GB/DWC out away from the wall, breaking the clean lines that had always dominated the system.  But that's fine.  A small sacrifice for an extra 130 gallons of capacity.

Build Update 2016-APR-23

Today we purchased a recycled IBC.  This will become the fish tank in the now-modified build.  More modifications to come.  The tote itself was available with a new bottle.  It was slightly more expensive, but since it has never been used we can be assured there should be no contaminates lingering.  I'll wash it out all the same.

The tote is a 330 gallon, which is about 130 gallons larger than the tank I had originally spec'd.  I'll have to use a SLO to deal with the waste accumulation on the bottom, but I'm hoping that will work OK.  An alternative would be to use the bottom drain itself, but I hesitate to do that, partly because it's facing the wrong direction.  The tote is also shorter than the cone-bottom tank, and since it's free-standing it was also about 1/4 the cost (i.e. no stand required).  I may place it on some PT 2x4's just to get it off the ground, since the back porch gets quite a bit of rain-water on the floor.  It's really just an accumulation, but also quite an annoyance.

I built the two frames (below) a few months ago.  Unfortunately, the project has stagnated due to lack of funds.  On the bright side, this has given me time to reconsider the fish tank (which is why it's now a tote), and time for the PT lumber to dry out.  With it dry, it will be easier to paint.  I still have to purchase and cut the PT plywood, and have been reworking the grow bed stand.  I am hoping to fix a few design concerns I had, and make it so that both the upper bed and lower DWC tank can be properly leveled.

The lumber, all cut and labeled

More pre-cut pieces.

The two boxes, sans bottoms.

Build Revision - Media plus DWC

I purchased a copy of the Green Acres Aquaponics' manual, which describes both the basic knowledge required for aquaponics and their specific build projects.  It was a good read.  I skipped a good deal of the basics, having already obtained them from multiple other sources.  But their build was fascinating.  They basically have a compact system that sports a small-ish fish tank (100 gallon I think), a roughly 4-ft by 4-ft media bed, and a 4-ft by 8-ft sump and DWC tank.  You can get all 8 feet of sump to work as DWC if you have the floor space available.

This turned me on to something I had been mulling over since I first designed my prototype: how to make use of that blasted sump.  One idea was to add media to it, to improve the bio-filter.  But without growing plants, it seemed like a bit of a waste.  The GAA manual also demonstrated how to use a specific liner for their builds, and that opened the door to this:

This is a media bed over a combination sump/DWC tank.  The upper bed is 2' by 8'.  The lower is 3' by 9'.  Since the entire system has to fit in a very small footprint on my back porch, and will already require artificial lighting, I'm planning on simply adding additional lighting to the underside of the media bed.   The last foot or so of the DWC will either get lighting somehow affixed over it, or be partitioned off and used as a place to add chems, etc.  While most publications seem to favor putting the pump in the sump tank, I still think I'd prefer it to be outside the tank for ease of access.  Guess we'll see how everything fits on the porch.

The GAA build also sported a radial flow clarifier.  The clarifier fed directly into the sump, and the media bed drained into the sump via bell-siphon.  I had originally started planning one into this build, but then changed my mind after figuring the media bed would probably provide sufficient filtration of the particulate matter.  That said, I can always add a clarifier later.  My idea for the clarifier was to set it high enough that I could set the sludge drain to empty into the media bed.  After all, the media bed was going to get straight fish water one way or another.  Theoretically, managing the plumbing such that the outlet for the clean water and the outlet for the sludge would be at the same elevation ought to give me two outlets with two different purposes, from the same device.  This will be something worth experimenting with in the future.

I have yet to price out the lumber for the above build, and the build requires a little further fine-tuning anyway.  If the total price comes out below the original build, I think that'll be a great value.  If higher, it will probably still be worth it for the fact that we'll more than double our growing capacity (since DWC gives you a much higher plant density than what you can achieve with media).  If significantly more - which I'd have a hard time believing - then we'll reassess just how important the DWC tank is.

Some things that this build doesn't give me: I won't be able to control the media bed flood and drain rates as much as if they were two separate beds - this means less opportunity for experimentation.  The DWC might suffer from particulate accumulation without the clarifier; we'll see.  The top of the media bed is quite a bit higher than the original plan called for - or at least I think it is...I haven't measured yet, but it's at around 40" at present and I don't want it to go much higher.

I'd love to have the space to spread things out, rather than planning to bend and stoop for DWC plant access.  However, this is a trial build after all and hopefully, with sufficient lighting, we'll get a good return.