Modified Solar Wood Kiln

[drunkenmugsy]

Here is the plan in a nutshell:

Want a solar kiln to dry wood. Thinking I can use a 20' shipping container to make a modified solar/dehumidification kiln. Using PV to power a 600W AC dehumidifier for 4-6 hours per day. Using PV to run a dc pump on a closed loop solar hot water heater to heat the container, 80W DC 4-6 hours per day. Using PV to power inner air circulation fans 100W AC 4-6 hours per day. PV to run air exchange fans 100W AC 1-6 hours per day. PV to run a monitoring system >100 DC watts 24hrs.

Total watts at peak would be 1000W+- for 4-6 hours per day. Longer would be great. Less expensive would be priority after 4-6 hour run time is reached.

Budget is under 5k$ including 2k$ for container. More is possible I just need to justify it to myself.
I have been using a solar kiln that a friend has. It works great in the summer. Not so much in the winter. What I am looking for is a system that will work year round with reasonable cycle times.

Some input on how to weatherize components would be useful. Inside the container will be a 'water condensing environment' obviously. The only things that will be in the container are the dehumidifier, fans and sensor probes. Everything else will be exterior attached in a mini solar shed. Something I can mount on the container itself is what I picture. Solar panels as well as the water heater loop mounted to the roof. Grid power is available but I would have to run it overhead DIY. Not ideal but possible. Off grid would be preferred.
Using a standard dehumidifier kiln pack for several thousand dollars and 220v power is not an option. The solar kiln works great. I just want to turbo charge it if possible. Worst case is I have a solar thermal kiln that is slow in the winter.

What other clarifications or info am I forgetting?

 

[snoobler]

Paint the container black. This weekend when the OAT was 46°F, the interior wall on the S side was 129°F.

 

[Prefersdirt]

Did not know these existed. Great idea!

Are you using a dehumidifier or an AC unit (like a window air conditioner) to speed up the process? Just trying to understand.

 

[drunkenmugsy]

Did not know these existed. Great idea!

Are you using a dehumidifier or an AC unit (like a window air conditioner) to speed up the process? Just trying to understand.

I am bouncing back and forth between a high end residential grade crawlspace dehumidifier(600$+) and just a regular in home room dehumidifier(200$).

 

[drunkenmugsy]

Paint the container black. This weekend when the OAT was 46°F, the interior wall on the S side was 129°F.

Yes I had planned on painting the South side. I dunno yet though. If I insulate the inside I am not sure how much painting it will help.

 

[drunkenmugsy]

I may have got ahead of myself but I purchased 6 of these panels yesterday for 120$ each. They are 3-4 years old.

 

[snoobler]

You are not alone in such behavior, though the scale of your choice is MUCH more reasonable... :

Just picked up 36 285W STP285 from Santan Solar for $70 ea

Received the promotional email: https://www.santansolar.com/suntech-285w-sale/ Online prices shows $80. Called to place an order to get the $70. Jason indicated it should be fixed on the website soon. Why did I buy 36 of them? My name is Steve, and I'm a solarholic. Srsly tho, I've been...

diysolarforum.com

 

[drunkenmugsy]

Then today I put a deposit on a 20' shipping container. Just a regular old beat up WWT. I do not want to afford the fancy side door container in the above picture just yet.

 

[drunkenmugsy]

One thing I am having trouble wrapping my head around is an enclosure for the controls. I am in NE TX. We can see anywhere from 10Fdeg to 115Fdeg. What am I going to have to do to not kill my batteries. I am leaning towards putting together a 24V system as above using LiFePO4 that are not as heat/cold sensitive. Still researching a good source for them.

 

[snoobler]

LFP is very cold sensitive - no charging below 32°F. Period. Risk killing them.

An insulated container for the batteries with the option for vending during summer. Your BMS and/or charge controller should have low temperature protection. 115°F isn't too punishing on LFP, but that's above 40°F, and that's kinda the healthy limit even though they'll work at higher temps. It will shorten their life, but not dramatically so.

 

[Picasso]

All depends on you local humidity what you going to have to do. As long as you can seal it up your good to go as far as an environment to bring the moister content down. A small $600 under 800watts -2-3pint a day dehumidifier will handle a 20' container. Going fast you will have checking/crack loss. Got a lumber mill last year and milling wood is the easy part...drying is the "Art" This is great stuff. https://www.amazon.com/gp/product/B003A08DU6/

 

[Hedges]

Yes I had planned on painting the South side. I dunno yet though. If I insulate the inside I am not sure how much painting it will help.

Insulate the others, paint and glaze the South side?
Paint the roof, and have tilt-up insulation to open it in the summer? With foil on the bottom side of insulation?
Tilt-down insulation on the South, also with foil.
those would double your capture area, although sometimes reflected light would miss.
Someone mentioned thin plastic sheet as glazing on pool panels.

 

[drunkenmugsy]

Insulate the others, paint and glaze the South side?
Paint the roof, and have tilt-up insulation to open it in the summer? With foil on the bottom side of insulation?
Tilt-down insulation on the South, also with foil.
those would double your capture area, although sometimes reflected light would miss.
Someone mentioned thin plastic sheet as glazing on pool panels.

I am going to attach the solar panels and water heater loop to the top of the shipping container. You cant really mess with the integrity of the container to much by cutting big holes in the roof or sides without adding more rigidity. I am going to make minimal perforations for wiring, air circulation and similar but that is it other than the doors themselves.

 

[drunkenmugsy]

Due to temp issues I am looking at AGM batteries like these. I dont want to have to worry about it as I have such a large temp envelope to cover.
These batteries look like they will fit the bill. I would probably start out with 2-4. Comments? Has anyone used these particular batteries or can recommend similar?

KiloVault 2.1KWh 12v

Operating Temperature Range
Discharging: -40 - 131°F (-40 - 55°C)
Charging: -4 - 113°F (-20 – 45°C)
Storage: -4 - 122°F (-20 – 50°C)

 

[snoobler]

Make sure you get more than you think you need, and apply temperature compensation during charging.

 

[Hedges]

Similar price per kWh to the brand I'm using, but says 3000 cycles to 50% vs. 1000 cycles for mine.

Sun Xtender PVX-2120L Solar Battery Apex Battery

This is the 12v 212ah 4D Deep Cycle Sun Xtender PVX-2120L Solar Battery .This <b>maintenance free</b> and <b>sealed</b> lead acid battery, fixes the acid electrolyte in a gel or in an absorptive fiberglass mat. The advantage of this design is that the ba

www.apexbattery.com

http://sunxtender.com/pdfs/Sun_Xtender_Battery_Technical_Manual.pdf

 

[drunkenmugsy]

I think I have settled on using this unit from MPP Solar, 2424LV-MSD(link to catalog pdf) with 2 x KiloVaults above. Any other suggestions or options? Now to figure out the best place to buy it from. MPP Solar USA ebay seller?

 

[drunkenmugsy]

I am making progress on the solar kiln. I decided to go with a growatt hybrid controller. I purchased their 3000w 24v model several weeks ago. I have been testing the automation pieces and have had good success. I am able to measure temperature and humidity on multiple sensors. I am able to turn on/off wifi smart power switches based on that temp/humi sensor input automatically.
I have tested the sensor wiring length so that I can have proper placement inside and outside of the kiln. This allows me to place the sensors inside the kiln but have the controller outside of the kiln. The kiln environment can be somewhat caustic due to tannins in the wood. I want to keep as much hardware outside the kiln as possible. The growatt, batteries, ESP32 controllers and smart switches will be in an enclosure mounted to the outside of the kiln.
I have purchased several 8" inline duct fans for air movement. I am very happy with these so far. They move a ton of air and only draw about 45W / .77A each. There will be 3 inside to provide air circulation in the kiln itself. I might only need two but planning on 3 for power designs. Then 2 more 8" duct fans circulating air from the heat exchanger to the kiln in a closed loop. Again planning on two but may only need 1 for this.
I have attached a couple pics. One is of the ESP32 controller and temp/humi sensor testing cable length. This will all be soldered and shrink wrapped in project boxes once finalized. The other is just a sample control dashboard. I will redo it for the kiln but you get the idea of what is possible with using just the default. You can get as fancy as you want with icons, graphs, colors.

 

[curiouscarbon]

nice, glad to see your project coming together

nice touch with the ethernet cable

 

[efmrrt]

Due to temp issues I am looking at AGM batteries like these. I dont want to have to worry about it as I have such a large temp envelope to cover.
These batteries look like they will fit the bill. I would probably start out with 2-4. Comments? Has anyone used these particular batteries or can recommend similar?

KiloVault 2.1KWh 12v

Operating Temperature Range
Discharging: -40 - 131°F (-40 - 55°C)
Charging: -4 - 113°F (-20 – 45°C)
Storage: -4 - 122°F (-20 – 50°C)

Where is the batteries going to be housed? Inside or outside the kiln? If inside the kiln, its a fail. I take mine to 145-150 for 6+ hours to kill bugs. Temps in full sun on a hot day can reach up to 200'F inside.

Currently building a solar system to power the 3 fans inside the kiln.