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Posts posted by KennethT

  1. This is part of my fascination with controlled environment agriculture. Yes, it's bound to be more expensive than farming on inexpensive land in more remote areas, but I can grow much more per square foot - maybe 5-6x the yield per square foot, and use about 1/10th of the water doing it as it as all recycled.  Also, I don't need to use chemical pesticides - whatever small amount of pests I may get I can handle effectively using Integrated Pest Management - which is basically using predatory bugs to eat the bad ones.  My crops are also less affected by disease, and there is almost no risk of E. Coli poisoning or other diseases that hit the cilantro used by Chipotle, for instance, and got many people sick.  Also, I can have crops turning year round - I can have the full output when it's freezing cold or burning hot outside - neither affects me.  Finally, I can do it in urban areas close to (or surrounded by) my market, so transportation costs (and its effect on the environment) are essentially negligible.


    It doesn't make sense to do this type of ag for field crops such as wheat or corn, but for higher value crops like arugula, herbs, tomatoes, etc. I think it is definitely feasible.

  2. For those of you following along with my controlled environment saga, I opened up the A/C and it looks promising that I will be able to solve my problem.  I neglected to mention that I got this A/C on Ebay, remanufactured - for about half the price of a new one, shipping included - which is saying something since the box it came in weighed 96 pounds, so the shipping costs are not so trivial....  Anyway, in the remanufacturing process, both the evaporator and condenser coils look great and brand new, as does the compressor motor itself - but the foam that seals off the area is either slightly damaged or missing entirely....  a short trip to the home depot should relatively short work of fixing my airflow problems, I assume.... until I try it and find that I have created more problems.... ha!


    • Like 1
  3. Right - this model supposedly uses the condensate to help cool the compressor, and even though it has a drain plug, according to the manual, unless it's being used in extremely high humidity, it should evaporate all the condensate and vent it out of the exhaust tube...


    I checked it out - it only seems like 6 screws are holding the case together - I'm going to take it apart this weekend... shouldn't be a big deal to play around with....

  4. It's a Whynter ARC-12SD... I took a quick look inside when I removed the filter, but I think in order to completely seal off the compressor/evaporator areas, it's going to take a bit more than duct tape. If I get some time this weekend, I'll open up the cover completely and see what I see...  In truth, I'm probably going to have to hack the control board anyway since my test crop, alpine strawberries, seem to like a nighttime temo of 50 to 55 degF, but the firmware of the A/C only lets it get to 61, and in practice, I find it actually turns off around 62.5...

  5. They definitely look like wafer cones, and are very different from tuiles. A long time ago, I had wanted to do something similar, and in my research, it seemed that the wafer cones are made in an industrial type process - I don't think it's possible to do at home.  Nothing that I've seen comes up with that "styrofoam" type texture....

    • Like 1
  6. 9 hours ago, dcarch said:


    Not necessarily. In aerodynamics, when air is blown over a surface, it will create an uplift pressure. Try to blow over a piece of paper. It does not mean air is being sucked out. Check your air flow pattern.




    Thanks for your thoughts.  When the A/C fan only is running (even high speed), there is no problem... only when the compressor turns on.  Also, I checked the flow at both inflow and exhaust tubes... the exhaust outflow is much stronger than what's coming in from the inflow.  I was thinking about adding some smoke to the inside of the tent to see if it was vented out, but the A/C has a filter which I wonder will filter it out so I won't see it anyway.  Plus, the negative pressure is EXTREMELY strong - all 4 walls and ceiling are sucked in...

  7. On 2/25/2017 at 1:43 PM, KennethT said:

    Yikes!!!  After only 30 minutes with the light on, the inside temperature went from a stable 77.8degF (with computer and fan running) to 94.5degF!!!  And that was not the temp after it had stabilized, it was still going up!  Now I really don't think a peltier based A/C is going to cut the mustard....

    I've been rethinking this statement...  I received my portable A/C unit - first of all, the thing is huge - it takes up about a third of the tent!  It's the smallest "dual hose" portable A/C I could get...  I wanted a dual hose version since, supposedly, it wouldn't vent much of my tent's air to cool the compressor - it uses an intake hose, which takes air from the outside, so it shouldn't create a negative pressure situation.  Oh well....  a few seconds after the compressor turns on, you can see the walls of the tent being sucked in - there is certainly negative pressure inside that tent!  More quantitatively, I ran a test - last weekend, the humidity in the apartment was a bone drying 11%....  So, I made an ultrasonic humidifier for the tent, and controlled it to keep a constant humidity in the tent between 60 and 70%, which at 75degF would create a perfect amount of VPD (vapor pressure deficit) in the plants.  When the A/C turned on, the humidity in the tent dropped to about 30% within 2 minutes - obviously, this was not caused by the dehumidification that A/Cs do, but rather, the influx of dry, 11% humidity apartment air into my tent....  A few minutes later, when the A/C turned off again, it took the system about 10 minutes to get back up to the proper humidity, at which time it was about the time for the A/C to turn on again!!!


    My biggest concern is actually not with the humidity, however, but CO2... since I'm going to be enriching the tent with CO2 to make the plants grow faster and utilize all the light they are receiving, every time the A/C turns on, it will be venting my CO2 out into the apartment... which is both a waste of CO2, and not desirable since I'd rather not live in a heavily elevated CO2 level... not that that level would get to the point that it is dangerous or uncomfortable, but still....


    MacGyver is back on the job... waiting for a few more parts to come in tomorrow... pics to follow.....

    • Like 3
  8. I also read The Martian, and enjoyed it quite a bit - but I kept wondering why he didn't grow his crops hydroponically - after all, it was NASA who did much of the development work on the subject many years ago, precisely for trying to develop ways to economically grow vegetables in space.  But, the reason he didn't do it is because he probably didn't have all the various nutrients he'd need for a well balanced hydro system - because they weren't planning on living on Mars for that long... their mission was only for a few weeks, so it would be pointless to try to grow food since they'd be leaving by the time it was ready for harvest.  But I wonder if they had a hydro garden on the Hermes, since they were living on it for a few years.


    I know all about the rain issues in SF... my wife just got back from a seminar in Napa - her inbound flight was delayed a few hours because of storms in SF, and it basically rained every day she was there!  I kept joking how the weather was nicer here in NY than it was for her in SF....

  9. They're everywhere here in Manhattan...  I have 2, each within 2 blocks of my apartment (although 4 blocks apart from each other).  While we have some new, good quality mexican places that are more authentic than Chipotle, Chipotle is cheaper - unless you want to go to the outer boroughs like parts of the Bronx, far away in Brooklyn.... then those Mexican places are really good, and cheap... but here in Manhattan, good and cheap are almost always mutually exclusive...

    • Like 1
  10. Yikes!!!  After only 30 minutes with the light on, the inside temperature went from a stable 77.8degF (with computer and fan running) to 94.5degF!!!  And that was not the temp after it had stabilized, it was still going up!  Now I really don't think a peltier based A/C is going to cut the mustard....

  11. Thanks for following along and your interest...  I will be posting photos as I go along to show progress....  I hope my tent and light come in tomorrow (they're supposed to)...  Depending on what time I get home from work will affect if I have time to start assembly immediately or in the next couple of days....

    • Like 1
  12. I am seriously considering a peltier based cooling system, but the more I look into it, the more skeptical I become of its cooling capacity.  Only the smallest of wine fridges use a peltier device.  I know for sure that mine is not - it is most decidedly compressor based.  My fear is that the light, which produces 2200 BTU of heat constantly, for 18 hours, will overcome any peltier based cooling in that space.  Then, at night, I'd like an inside temp of about 60degF, which is probably about 15degF less than the ambient.  It seems that in order to get any decent cooling out of it, I'd need to run several in parallel, at which point, the power consumption would be way more than a small compressor based A/C.  I think a small 10000BTU A/C would be ok in the tent as long as I turn it on and off with a few degrees of hysteresis - so the A/C can turn on when the inside temp gets to 80degF, and then turn off when it gets down to 75degF, and let it cycle that way.   Couple that with the fact that the tent's night will not necessarily be night time in real life.  This is because the ideal time to harvest is maybe up to an hour or two after sunrise - that is when you have the highest product weight.  But I don't have time to do all the measurements and stuff I need to do first thing in the morning before going to work, so I was going to set "sunrise" to about 7PM or so, so I can come home from work around 7, do my measurements/harvest and then go on with my evening.  So, my "nightime" temp of 60F would coincide with the hottest time of the day in my apartment, which, especially during summer, can be get quite hot, even with all of the A/C running.

  13. @Shelby Thanks, but don't be silly! Everyone has their own strengths and weaknesses, and from what I've seen over the years, you're incredible at a lot of things I wouldn't even think of trying!  The stuff I do is strongly linked to my background - I was an electrical engineer in college, and I run a business that makes electrical products...  so this stuff is fun for me... but incredibly boring to most others.

    • Like 5
  14. ha!  I'd be surprised if I'm not already on it, since my lime tree has a big LED light over it (and it sits in the window) - it's so bright you can see it from the street - and I'm on the 21st floor!


    Also, I want quite a bit of air movement which will help evenly distribute the CO2 which wants to settle on the floor, plus it will keep the plants from getting an extremely humid microclimate around them which can be caused by the air being too still.  I think the biggest problem indoor growers have is with the humidity being too high right around the plants.


    I'm now wondering if I can build my own peltier airconditioner using a sealed box with a few peltier devices mounted on it, a fan and an in and out duct.  Plus, I can put a drain at the bottom of the box as it will collect water from condensation - maybe I should build the A/C out of a beer cooler? 


    I was also thinking about building my nutrient chiller using a similar system - fill a beer cooler with water and pump that water through a few peltier cooling waterblocks...   put a stainless steel coil of tubing (used in beer making) in the cold water and pump the nutrient fluid through it.  That way, I don't have to worry about copper or aluminum of the water block leaching into my nutrient.

  15. @dcarchWell, since this is going right in the middle of my living room, I'm not making my own tent, I'm using this: https://www.gorillagrowtent.com/products/gorilla-grow-tent-5-x-5 This tent is completely light proof, and I'll be sealing it as well as I can so that I don't have much air exchange between inside the tent and the ambient living room as I'm enriching the tent with CO2, and I'd rather not have it leaking out all the time.  I have thought a lot about peltier devices to cool it, but I'm worried that they won't have enough cooling power, or I'd need tons of them which would be super expensive.  They would be ideal as they would make sure I don't vent my tent atmosphere into the apartment as they don't move the air around.  The problem is that the tent is roughly 175 cuft. and the light creates about 2200 BTU of heat while it's running, which is 18 hours a day.  That's a lot of heat to remove with peltier junctions in a big space.  So, I think I'm just going to use a dual hose 10KBTU portable airconditioner, turn it to its coldest setting, and then just turn it on and off with the controller with a couple degrees of hysteresis so I dont prematurely burn out the compressor.  But before I get it, I was waiting until the tent and light arrives (Tuesday) so I can see how the temperature varies throughout the day first.  But I think I'm going to use the A/C anyway since I want a pretty large diurnal difference - I'd like a nighttime temp in the low 60s and the day time temp around 75-80 (and don't want to met my apartment that cold at night!).  I don't think I'll need a humidifier as the plants will create their own humidity fast enough - especially in an enclosed space - what I'm really going to need, I think, is dehumidification - which should be handled by the A/C...  if it's not enough, I can build a desiccant based dehumidifier to help, but I don't think I'll need it.

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