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.

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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.

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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.

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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.

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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.

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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!

EuroFresh Farms – Another example of using water as the heating medium

Here’s another example of a greenhouse, this time a huge commercial greenhouse, that uses water as the heating medium.

There are substantial differences between a geothermal water system and this system, namely, the temperature of water they use is very hot relative to a geothermal application and therefore they do not use the system to heat the growing medium directly.

They also use natural gas to heat the water.  Natural gas is good because it burns into primarily water vapor and CO2 which they recycle by giving it to plants.

Greenhouse solar heating


The ultimate source of heat for my greenhouse is the sun.  Even if the outside temperature is less than 10C, inside, due to the energy input from the sun, I’m seeing up to 40C on sunny days and almost 30C on overcast days.  However, my water reservoir, which I pump through a geothermal bank 6 feet under the ground and through my soil bed, is only seeing a maximum of 15C on those hot days.  As nights have been dropping below freezing (-4C), it drops about 5C to 10C when I wake up.  That’s not acceptable.

The issue is that the air in the greenhouse can only heat the water if it comes in contact with the reservoir container.  Further, waiting for the air to heat up by the sun, and then the air to heat up the water isn’t ideal.  Air is a poor conductor of heat and has relatively low energy storage capacity.  To improve this situation, we need to increase the surface area of the water system.  We could put in a bigger reservoir but space is a scarce resource inside my greenhouse.  A larger reservoir will increase the surface area, but only a little bit of that will receive direct photon penetration from the sun.  What we really need is a solar heater.

I have a 4 ft x 6 ft area above my components.  I could mount a board of some sort up there are coil some water tubes to increase the surface area.  I also have 2 old CPU radiators with fans.  This will increase the effective surface area of the water’s contact with the air.

Over a couple weekends, I took the 200 ft of black poly tubing and made two spiral loops almost 2 feet in diameter on a 8 ft by 4 ft Styrofoam board I picked up at home depot.  In between the two spiral loops, I placed the radiators in series.  To hold down the tubes, I used automotive-grade 3M double-sided tape in an “X” pattern.  On the top, I used gorilla tape, but this wasn’t effective.  Right before installing, I used 10 gauge wire to lock it down in case the 3M tape fails.

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I mounted the setup at a 30 degree angle near the top of my greenhouse facing south.  This is not ideal.  In my area, a 70 degree angle would be better, but space is limited, so this will have to do.

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Before I installed it, I tested it on the ground at a 70 degree angle.  Over the space of an hour or two, the water heated up from 13C to 19C.  It was a sunny day.  This is about the same as pouring two good size pots of boiling water inside the reservoir.

I’ll continue tracking the performance, but today I’m optimistic this will help.  The running cost is pretty cheap too at only 28 Watts (12V @2.4A max).  I’ve coded up an algorithm in my automation controller to only turn on the pump if the air is hotter than the reservoir.  This is good for the winter time, but this rule probably won’t work will in the summer.  In fact, I may have to add a rule to turn on the solar heating system to help cool the greenhouse.  We’ll see.

What about the cost?  Well, this addition was relatively cheap.  If you want the cheapest solution, this might be it.

Cost breakdown:

Total: $104

Bonus:

Bonus Total: $119

Geothermal Water Reservoir to Soil Energy Transfer

It was cold today.  It’s been cold all week.  The high for today was 7C (about 44F, yes, Tidder, I love you) and the low was 6C.   This caused my soil temperature to drop to 11C (52F).  This is bad.  In addition, it looks like it was very dark most of the day.  My artificial lighting accounted for 85% of the total light energy in my greenhouse (how my light algorithm works).  The sunlight was only able to warm the greenhouse to 15C.

In a conversation on IRC, a friend, wondered if PEX tubing was very good at thermal conduction (ability to transfer heat energy to another substance).  After a bit of searching, I found that PEX has very poor thermal conduction relative to, say, copper.  If PEX is 0.4W/(mK), copper is like 28.  Big difference.  All is not terrible, however, because water is only 0.6W/(mK).

Looking at today’s data, there was a couple degree discrepancy between the reservoir temperature and the soil temperature.  I would have thought it would be almost the same.  Could thermal conductivity explain the difference?

I conducted an experiment.  I boiled some water and poured it into the reservoir.  This brought the temperature to about 21C (from about 14C).  Over the space of a couple hours, I logged the temperatures from both over the space of 3 hours.  Here’s a scatter plot of the reservoir and soil temperatures:

redhouse-resevoir-soil

The chart shows a negative correlation between dropping reservoir temperatures falling and rising soil temperatures.  We have energy transfer!  It also shows about how much pumping time is required to raise the temperature of the soil by a few degrees.  This could certainly explain how there could be a difference between the reservoir temperatures and the soil.  If the reservoir heats up quickly during peak temperature, it could be several hours before the soil will rise.

During this test, the control soil bed (unregulated) remained around 13.11C and eventually fell to 12.9C after 3hrs.  The air temperature dropped from 10.1C to 9.7C.  We lost some energy to the air, but not enough to change the air temperature upward.  We also likely lost a significant amount of energy to the geothermal bank which as about 4 or 5 time the contact area as the soil bed.