Optimizing the greenhouse cooling system

My current cooling solution is composed of the following:

  • 15″ x 12″ intake water-cooled heat exchanger
  • 12″ exhaust fan
  • 8″ water-cooled heat exchanger with 240mm fan x2
  • Geothermal loop 5-6′ deep
  • Soil bed and aisle loop 3-4″ deep

Since the beginning of spring, I’ve been optimizing the cooling system.  Now that it’s summer, I can test it’s capabilities.  Here are some of the principles I’m trying out.

Variable setpoint

In my area day/night temperatures can swing violently.  7C at night, and 31C during the day isn’t uncommon.  It will become more consistent as summer progresses, but for now, I want a system that will change the setpoint based on the fact that nights are colder.  I want the system to store more heat during the day so it can keep things warmer at night.  So I have a bit of machine learning built into the system that takes into consideration the night time temperature and allows for a higher setpoint during the day to store more heat.  I have to keep the setpoint within livable conditions for my plants.  Right now, I’ve got 9C as my lowest setpoint, and 34C as my highest and the “ideal” setpoint at 24C.  For every night the temperature drops below 9C, I raise the running setpoint by one degree.  In the winter, that will probably mean that the temperature could reach 34C and maintain there for a while.  In the summer, if the nights are warm, the setpoint will decrease as long as it’s above the 24C.

With this type of “learning”, I shouldn’t have to ever manually set my setpoint.

Oh, and one more thing.  If the setpoint is kinda high -too high for humans to comfortably work in the greenhouse, I have a rule where if the human lights (a white LED strip) are on, change the setpoint to something that a human can tolerate.  For me, that’s 23C.

CO2 On-demand

The rule for this is simple.  If the temperature is below the variable setpoint and it’s daytime, burn some hydrocarbons and make some CO2.  If it’s night, only turn on if the temperature drops below the minimum threshold (9C).  Plants only need CO2 when there’s light, so trying to maintain a certain CO2 level at night will become expensive.

Exhaust only when needed

I have my exhaust set to turn on when the temperature exceeds the maximum threshold of 34C.  Why?  Well, if there’s a certain CO2 level, and it’s 25C (vs the 24C setpoint) we don’t want to exhaust the CO2.  That’d be a waste!

We will, however, exhaust the CO2 if we get a gas alarm from the harmful gas sensor.

Variable speed intake

My intake has 6 200CFM 120mm fans controlled by a photon which can PWM a MOSFET to control how much voltage the fans get.  Using a PID algorithm and the variable setpoint, On the photon, I get 8bits of control resolution (256 steps) so I’m able to suck in just the amount of air needed to cool.  Almost all of the cooling work is being done by this and the other heat exchanger.

Below you can see how well the intake system tracks the temperature (right graph) and also see when the exhaust fan kicks on (left graph).

intake and exhaust

Heat exchanger for geothermal

I redesigned my geothermal system a bit.  Instead of using the same reservoir as the irrigation, it now exclusively uses a 50 gallon drum and a small 5w continuous pump.  This pump pumps water through the geothermal system and back 24hrs a day every day.  In addition, I moved the water cooling pump (the pump that pumps through the intake, LEDs, CO2 generator, etc) to use this dedicated drum as well.

This change allows me to add a bit of chlorine to the water to keep algae from clogging my tubes.  It also frees up my irrigation reservoir for liquid-based feeding (more on that in a future post?).

To compare, here are the designs for both the old system and the new system.

Trip's greenhouse water system

New system:

Trip's greenhouse water system (3)

Attached to the geothermal line is my little 8″ x 8″ heat exchanger with 240mm fan.  The fans don’t push a lot, but it’s the quality that counts.  The air coming from there is cooled from water deep within the earth.

IMG_20160620_202347064_HDR

I don’t open my door

With this setup, I have never had the need to open my door so far.  This hopefully keeps pests out and with them, disease.

Conclusion

Over the next several weeks, I’ll be trying to test the potential of this system.  Today’s high was 27C.  My high temperature in the greenhouse was 36C right around the time I increased the aggressiveness of the intake PID algorithm and reset the system (see the missing data on the graph above) .  With that aggressive setting, the intake still only hit 210 pulses out of a possible 255.  My next goal is to optimize the PID settings and tune it better.  This will further give me an idea of the systems capabilities.

Augmenting greenhouse with blue and far red LEDs

I’ve done a few posts about the benefits of blue and far red lights on plants.  I’ve used them on my seedlings.  Now that I have no seedlings for the moment, I wanted to try them out in the greenhouse.

But the greenhouse is outside, right?  It already has the sun, right?  Yes and yes.  However, exposing plants to a higher concentration of blue light before sunrise, can begin the process of the plant opening its stomata (pours the plant uses to “breath” out water and breath in CO2) to make it more ready for photosynthesis and ultimately carbon fixing and growth.

Far red light benefits at the end of the day are already covered in a different blog.  The higher concentrations should help -especially because trees and other objects shade the setting sun from my plants.

I’m trying to put growth and fruit production into overdrive.  My max expected yield should be somewhere around 1-2lbs of tomatoes per day.  I’m getting close to 1lb every 2-3 days.  The blue light along with CO2 boosting in the morning should help with growth and production.  I expect to see less suckers on my tomatoes and more growth with the far red light as well.

My red and blue lights are enclosed in flood light housings.  It was pretty easy to set them up this way.  I used a carabiner to hang them from the wire over my second bed.  I then pointed the lights at my tomatoes and ran the power cord to the ubiquity mfi mpower strip that I recently installed.  The cool thing about the mpower strip is that you can control it over wifi -so I can tie it into my automation system, but it also supports simple schedules including location-based sunrise/sunset.  I created a schedule that starts the blue light 1hr before sunrise and turns it off 1hr after sunrise.

The blue light looks really cool at night.  This is what a 50 watt LED can do.

IMG_20160611_214600801

The schedule I set up for the far red LED was 30 mins before sunset, and turn back of 1 hr after sunset.  It isn’t visibly as bright as the blue, but my infrared camera sees the difference.

IMG_20160611_213657044

I’ll try to remember to follow up if I notice a difference.  If I forget, comment below and I’ll either respond with my findings or make a new “results” post.

Radiant aisle heating/cooling in greenhouse

As I mentioned in a video a bit back I wanted to add more water to the geothermal water system.  This will improve the systems ability to absorb and store more energy.  This should improve cooling in the summer and heating in the winter.  I decided to place a 55 gallon drum to the rear of the greenhouse.  Additionally, to maximize the system performance, I wanted to add radiant heating/cooling pipes in the aisle between the beds.  This will increase the surface area greatly.

It took several weeks to get all the parts and plan the attack.  But once the parts and plans were in place, it only took a couple hours to retrofit the greenhouse with the upgrade.  Here’s step-by-step what I did with images.

The Plan

Here’s an image from about a week earlier showing what we are working with.  The bed on the left is regulated with the geothermal water system.  It has PEX tubing running through the bottom of the bed.  We are going to attach to that tubing and run 4 more lengths up and down the center aisle between the two beds.  At the end of the aisle we will put the 55gal drum.

Before the retrofit
Before the retrofit

Step 1 – remove tiles and dig trenches

This was pretty straight forward.  I made the trenches about 2-3″ deep.  The first trench and last trench hugged the edge of the bed.  In the middle, I made the trench deep and wide enough for two passes.  The reason for this is I needed exactly 4 passes but the aisle just wasn’t quite wide enough for that with 9 inch spacing between the passes.  The aisle is just under 3 feet.  If it was exactly 3 feet, it would have been perfectly spaced.

Trenches
Trenches

Step 2 – Lay out PEX

PEX really doesn’t want to be straight.  Putting some dirt over the ends helped me hold it down enough to get it in the trenches.

PEX layout
PEX layout
PEX layout 2
PEX layout 2

Step 3 – Cover PEX

While digging the trenches, I move the dirt to a wheelbarrow.  I moved it back after laying out the PEX.  I also added a layer of sand to help level the aisle.  I used 4 50lb bags of sand from Home Depot.

IMG_20160423_182124651 IMG_20160423_183406541

Step 4 – Clean tiles

The tiles got kinda dirty over the last 9 months.  This is a good opportunity to clean them off.  These tiles are made from recycled rubber tires.  The cleaned easily with a hose.

Cleaning the tiles
Cleaning the tiles

Step 5 – Weed cover and replace tiles

I put down two layers of weed cover.  Mostly because it was already rolled as two layers and the length was perfect for the aisle.  Rather than unfolding the layers, I just laid it out as it was rolled.

IMG_20160423_184311974 IMG_20160423_185308480

Step 6 – Connect barrel to system

The PEX is 1/2 inch.  I bought some braided PVC tubing of the same inner-diameter to match.  I connected them together with several barb couplers.  For the barrel, I drilled holes in the bung-cap and put some 1/2 inch NPT threaded bulkheads.  The bungs for this barrel are not the same as I’m used to.  These drums are of Japanese origin and it took some extra planning to make adapters for them.

IMG_20160423_185821178

To get the pex to fit on the plastic barbs, I had to heat it up to soften it.  The fit still wasn’t great.  Brass barbs fit better.

IMG_20160423_190809415

Step 7 – Fill the barrel

This was slightly tricky.  My reservoir is 20 gallons.  It fills from 1/4 inch tubing from my rain water barrels via a float valve.  The geothermal water system is all 1/2 inch.  Output is greater than input.  So to fill the 55 gallon barrel, I needed to add more water as needed to the reservoir.  I used my garden hose to add water when needed.  I had to fill it a couple times after it got low.

IMG_20160425_170209079

Note: this may look not level… and it is, but not as much as you might think.  First, the left post of the greenhouse settled about 6 inches.  Second, the barrel is under pressure and is bulging a bit making it lean more to the right.  The bulging is concerning.  I fix might include a reducer before the inlet.

Profit

After filling it with water and tightening up a few hose clamps, it was finished.  Let’s enjoy some fresh garden strawberries and celebrate the new 20 megawatts I’ve just added to the system.  This brings my total up to 27mW (20 gallon tank is 7mW at 23C).IMG_20160425_114539348

Water cooling grow LEDs

I needed a few more lights for my second greenhouse bed.  I had the bright idea to use water cooling because, well, I already have a water system, why not direct the heat from the LEDs somewhere useful, like the soil bed?

You can take a look at my previous blogs on how I made the LED strips.  This time, instead of using heat sinks, I used water blocks, which were about the same price.

After a long break from lights, I finally got a system put in to water cool several components at the same time from the same pump.  Check it the video explaining that here:

I’ve got everything I want just about hooked up to the water system including a water cooled air intake system and the solar and CO2 generator.  Only thing left is maybe another heat exchanger and maybe another strip of lights.

Initial testing is promising.  After several minutes (long enough for part of the aluminum back to get very hot to the touch), the water blocks and surrounding area remained very cool.

What about cost?  Well, this actually ended up being cheaper than the previous system.  The water blocks where the same cost, but the savings came in the power supply.  I have been using one power supply per 6 LEDs (180W per 6).  Instead of a 350W power supply (that can’t really do two at full power, I’m using a 400W 24V power supply to power 12 LEDs instead of just 6.  This saves me about $50 per 12 LEDs.

Stay tuned, I have something awesome in the works related to LED grow lights.  I think it will take these lights to the next level.

Grow Lights 101: What kind of light matters

If you are following my youtube channel, you’ve probably already seen this.  If not, here it is again.  This is an introduction to grow lights where I cover what are the important aspects of light relevant to plants and compare a couple different types of grow lights (T5 vs LED).

To sum things up, T5’s are cheaper out of the gate.  But LEDs are more bang for the buck in the long run.

I am building LED grow lights for anyone interested.  Head on over to the new tripzero.io store.

10W Far Red LED Grow Floodlight

Far red (740nm) might be very beneficial to tomato production.  Studies have shown that it can help produce longer “hypocotyl” (the seedling shoot that becomes the stem) by just blasting the plant with 12 minutes of light at the end of the day (16hr photoperiod with T5 lights).  Other studies claim that far red can help reduce or eliminate sucker growth.

Parts:

Total cost: $33

 

50W Blue grow light build for seeding

According to my research, blue light is primarily used in plants for vegetative growth.  It follows, therefore that blue light is best for seedlings and clones that you want to grow in size quickly.  Is this logic sound?  I’ll experiment, and report back.

This video is a live build video where I make a $54 dollar blue-only grow LED floodlight.  Note that at the time of posting, the floodlight price has already changed on Amazon.  You can typically find these on ebay for a reasonable price.

Materials:

Total Cost: $54

LED Stair Lights


Stairs are pretty boring, but they don’t have to be.  I convinced my loving wife that she needed stair lights.  I put the project off for over 6 months while I’ve been greenhousing, but now that that project is more completed, I have time to get back to house projects.  Let’s get building.

Building

First, we will use the APA102 lights.  These are individually controllable.  They are the same lights we’ve used in our ambilight project with the minnowboard max.

I came up with a simple light protocol that supports “instructions” rather than just raw pixel data so it’s fast and light.  I’ve published the library here on github (be sure to use it with my forked Adafruit_dotstar library which has the “driver” for the LightProtocol).  I loaded that onto a particle photon, combined with an level shifter, and powered the thing with a Drok DC-DC power supply and a 24V 5A AC-DC adapter.

To install the LED strips on the stairs, I picked up several aluminum channels from superbrightleds.com and the corresponding “frosted” covers.  To stick the channels on the stairs, I used 3M automotive double-sided tape.  The aluminum can be drilled and screws can be used to mount, but I didn’t do that.  I used a simple dremel to cut the channels where I needed to.

I’m hiding the photon and the power supply in the closet which is adjacent to the stairs.  I cut a small hole in the wall on the closet side and put a 4 wire, 14AWG cable through the wall.  This is low-voltage (5V), so you don’t need an electrician or a expensive permit to install inside the wall… at least in my area.  On the other side, I combined a 2 socket “keystone” faceplate with a couple two wire speaker jacks.  This doesn’t look half bad.

Effects

Using the same python library as the minnowboard max ambilight project, and adding a “driver” that can speak our “LightProtocol” that we’ve installed on the particle photon, we are able to to complex effects and themes on the desktop and change the lights over wifi.

I have three effects coded up: “Chase”, “Random Rainbow Transforms”, and “Rainbow”.  Check out the video for how these effects look on our lights.  What other cool effects can we do?

 

Redhouse December Update

The last few months have been trials, full of learnings and many successes.  This is really only my second tomato growing experience and first experience with a greenhouse.  First  let’s look at the successes.

Successes

I’ve harvested several pounds of tomatoes so far.  There’s several more pounds to harvest.   On addition to the tomatoes, I’ve harvested lots of parsley as well.

The greenhouse is fully automated.  The irrigation, the lights, the solar, heater the blower… just about every electronic component is controlled by my custom automation software.  I’ve been tweaking the rules for months and its working really well.

Trials

Humidity sufficated many flowers in Sept and October.  They developed mold which prevented fruiting.  Adding a dehumidifier to the system solved that and fruit started to set in November.

Electricity has been my latest trial.  It started getting below freezing so I added an electric heater.  The load from the heater started popping my 20A breaker.  On night it popped and temperatures dropped to -2C air and 9C soil.  This caused serious damage to more than half of the 10 tomato plants.  The planta dropped flowers and aome of the youngest fruits.  To solve the issue temporarily I put the heater on a separate breaker with a long extension cord.

Between the humidity and the cold I probably lost 2 months of future harvests.  After December, I may not see another harvest until March.

Learnings

Avoid higher than 80% humidity.  85% is a critical threshold and mold will start to take over.

Don’t share electric breakers.  I did not foresee the need for a heater.  Even so, future proof yourself by putting your greenhouse on an independent breaker or two.

Improvements

The door leaks heat.  It needs to be rebuilt.  When I start, it needs to get done *fast* because I can’t leave it unfinished at night.

CO2 generator/water heater.  I found a water cooled CO2 generator.  This is perfect for a geothermal water system because it heats the water AND produces CO2.  I may be able to eliminate the electric heater if this thing works.

Measure electrical cost.  I plan on adding a current sensor to the new breaker.  I’ll be able to see what my electrical costs are and use that in my automation software.  I’ll be able to create “power saving” rules when costs exceed expected production.  The current sensor has been installed, now I need to get it tied into the system.

I have almost 600 Watts of grow lights that still need to be built and installed.  200 watts on bed A (the tomato bed) and 360 watts for bed B (strawberries, onions, garlic, herbs).  This will help with growth especially with the onions and garlic which don’t get any direct light because of how low the sun is in the horizon and how high my fence is.  It will also help produce heat at night as a fallback if the geothermal system or water heater can’t keep up.

Conclusion

It’s been a rough few months, but things are literally looking up as new growth is being observed in many of the damaged plants.  After the door is rebuilt, I believe the heat and even the cooling and humidity problems will be solved for good.  The new wall where the door will go will have vents and fans for intake and exhaust.  I’m excited about the improvements in progress and seeing some real results.

Happy new year everyone and happy 2016 harvesting!