PFC V1 - Using Tubular Heating and Peltier Cooling


#1

I’m building a PFC V1 (simpler, and technically easier). Currently I am using a fan heater (as per BOM) to provide heat. However, it gets very hot (obviously!) and anything near the front will get toasted. For the next build, I hope to use a tubular heater https://www.amazon.co.uk/Tubular-Garage-Greenhouse-Electric-Heater/dp/B003SD4XK4 [see example]. Can Anybody see any drawbacks to this? Also, as I am based in a hot humid environment (Shanghai) I have switched the standard cooling fan out for one with a pettier cooling element. Has anyone tried this or had any issues?


#2

My company has a V1 food computer although sadly it lies dormant currently. It is on my list to upgrade the s/w of this unit to the V2 s/w stack. I also want to incorporate a cooling system for the air and/or water. I’d love to see more details of your Peltier cooler. I would be especially interested in any power consumption calculations that you have regarding this form of cooling.

Also, I did conduct grows in the above mentioned V1 food computer using a standard aquarium water chiller (along the lines of this unit: https://www.amazon.com/Active-Aqua-Chiller-10-HP/dp/B0048IVBT4/ref=sr_1_3?ie=UTF8&qid=1506095944&sr=8-3&keywords=water+chiller) without any air cooling. I grew Romaine lettuce and it did well as long as I kept the Food Computer in my air conditioned house at 75 degree F.


#3

So it uses a 12V DC 6A setup. This is more juice than the Arduino can provide given the BOM calls for a basic PC fan as cooler. So I have used a relay switch to run the cooler direct from the AC DC Converter


My Heat/Humidity/Air circulation unit, based on the advanced piece of technology of ‘a lunchbox’ was a bit of a pigs ear. So I want to look at removing the heater in favour of a tubular one installed in the grow chamber


#4

Did you custom build the Peltier air cooling unit? How low are you able to drop temperature? I’d be very interested in more details about how you built this. I would like to add a similar Peltier as an add-on for MVP to enable Co2 actuation. Did you purchase this or build it custom? Would you mind providing a rough BOM or at least some more pictures, a cheap, effective, cooling system is a HUGE need. I am collaborating locally with @ferguman and I think together we can help get your solution out to the community.

How necessary do you think heating is? I’ll be honest: having grown hydroponically for a few years now I think that cooling is WAY more of a need than heating. Also, cooling the water reservoir is arguably even more important than cooling the air itself (this will have an effect on the air too) and a direct impact on the amount of DO in the water, a crucial metric that is often overlooked by most growers. Most plants you’ll find prefer water temps of 60-75, and ambient air temps of 70-85. That being said, most plants prefer a cooler night-time temperature than daytime (strawberries for example want as low as 10C). Lastly, ideal temps are one thing, but survival is necessary. Plants have a much higher tolerance for cold than for heat. While lower than desired temperatures might reduce the speed of growth, it will not stress the plant to a point where it is stunted or even dies.

With the MVP we just use exhaustive cooling when the lights are on. What I’m getting at is that you may find out you don’t need a heater at all, and that the lights are sufficient to achieve the daytime temperatures you want (especially if your ambient air is warm anyway).


Can I grow strawberries with a PFC(v2)?
#5

Hi Peter, thanks for your reply. I built this using a kit I ordered online https://item.taobao.com/item.htm?spm=a230r.1.14.55.576a36ebIqnL7x&id=558769028119&ns=1&abbucket=10#detail self assembled. It consisted of two fans, two heat sinks, and a peltier plate, plus a foam thing to keep the peltier in place, and some sort of paste for conductivity? Anyway, fairly simple to assemble. Picture below you can see the layers.

We hope to test in the next week or so, and then I can give you more data. From online videos it seems it can cool a drinks can in a polystyrene box relatively quickly (less than an hour). However, the grow chamber isn’t as well insulated, is larger and will have the lights adding their own heat.

We are hoping to teach kids about plant science and data sets, so would like to maintain a heating element to demonstrate the effects e.g. “oh look, it’s dead”. Realistically our main issue is going to be cooling, ideally just a few degrees below the outside temperature though .


#6

@Hollmat Looking forward to the results of your experiment. I built a prototype (before knowing about OpenAg) using this same model of peltier and the results were not as desired. It hardly had any impact on the temperature inside. Although that prototype was built of a thin acrylic sheet and the outside temperature was about 28C.

I am now going to try with a higher powered peltiers and larger heat sinks.