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.