Daddy Tanuki
Solar Wizard
wrong post
In-ground Cooling for LFP
- Thread starter justgary
- Start date
Bluedog225
Texas
- Joined
- Nov 18, 2019
- Messages
- 2,893
Nice project.
I pointed my laser thermometer down an 6” wide hole, 15 feet down. It was still 89 eff.
I pointed my laser thermometer down an 6” wide hole, 15 feet down. It was still 89 eff.
Daddy Tanuki
Solar Wizard
I as well trying to simply things down to less and less "energized or powered" controls and more passive.
Daddy Tanuki
Solar Wizard
I would try a physical probe all the way down. i use both thermocouples and laser thermometers in my work and just a degree or two of misaiming and temps are out of whack. with a physical thermocouple and a datalogger you will probably get a totally different reading. not to mention if that hole is open and open to the atmosphere its temp inside the hole will raise to close to ambient given time. if the OP decides to go with a water based system as soon as the heat exchanger piping is lowered into the hole it should be back filled with earth.
Geokilroy
New Member
As I stated before, Check with your Community College to see if they have any “Geo-Thermal” classes. If they do you could probably get some textbooks from the class. Their bookstore should have used books available. The instructor might give you some tips for your area? If you don't want to invest the time for a full course Just get the textbooks and read them. Many have projects to see first-hand how Geo-Thermal works.
Daddy Tanuki
Solar Wizard
college level text books are a much cheaper source of info than the internet.... just saying
Geokilroy
New Member
I researched this subject a few years ago. I wanted just general knowledge. I contacted several sources and found entry and mid level college courses had excellent textbooks and were written so I could understand the info. I bought some used textbooks that had notes and highlites that made some of it easier to understand. I studied these only as far as I wanted to go. My wife sold these at a garage sale when someone saw them on a shelf. I had not used them in years and someone needed them. I only studied them enough to make myself dangerous. Good for general knowledge.
Sorry about the long delay updating this thread. I wrung my hands and gnashed my teeth over many different details of building an underground shelter basically by myself. My wife finally encouraged me to make progress, so I looked again at precast shelters. I had used a post hole digger to make a three foot deep hole and measure the temperature. It was roughly the expected 75*F at the bottom when the top was well over 100*F.
Anyway, I bought a precast storm shelter for more than I had wanted to pay. It is a bit smaller inside than I would have made if I had done it myself, but it is done and working now. I would still be wringing my hands over how to build one onsite. The bonus is that we have a certified storm shelter to use when a hurricane comes. We will stay home for Cat I or II, but drive to the shelter (about 55 minutes away) for any storm Cat III or above.
The shelter is cut into the hill about five feet deep at the back wall. The dirt excavated from the hill is used to overburden the walls and top to help keep direct solar loading down a bit. The north wall is open to the air, which gets quite hot and humid during the summer. The shelter sits on top of 2" of lime rock gravel with filter weave. The shelter was then coated with three coats of liquid waterproofing and then wrapped in plastic to help keep moisture out of the concrete. The overburden dirt also helps keep UV from deteriorating the plastic.
The shelter and earthwork:
Anyway, I bought a precast storm shelter for more than I had wanted to pay. It is a bit smaller inside than I would have made if I had done it myself, but it is done and working now. I would still be wringing my hands over how to build one onsite. The bonus is that we have a certified storm shelter to use when a hurricane comes. We will stay home for Cat I or II, but drive to the shelter (about 55 minutes away) for any storm Cat III or above.
The shelter is cut into the hill about five feet deep at the back wall. The dirt excavated from the hill is used to overburden the walls and top to help keep direct solar loading down a bit. The north wall is open to the air, which gets quite hot and humid during the summer. The shelter sits on top of 2" of lime rock gravel with filter weave. The shelter was then coated with three coats of liquid waterproofing and then wrapped in plastic to help keep moisture out of the concrete. The overburden dirt also helps keep UV from deteriorating the plastic.
The shelter and earthwork:
The good news is that I was able to extend the cut into the hill and make the ground level all the way to the end of the cut, so I won't have any significant water pooling.
I decided to route the inlet air all the way around the shelter in a downward spiral to help cool the incoming air. The primary reason for this is to help lower the dew point and let any condensed water flow back out of the pipe, but it should also help keep the box cooler in general. The pipe comes out near the ground through the wing wall. You don't see it in this picture, but the outlet air pipe comes out of the box and turns straight up and has a small turbine on it to help pull air through. I have small muffin fans on the inlet and outlet to pull and push air through for the times we might need to stay in the shelter during a storm.
I decided to route the inlet air all the way around the shelter in a downward spiral to help cool the incoming air. The primary reason for this is to help lower the dew point and let any condensed water flow back out of the pipe, but it should also help keep the box cooler in general. The pipe comes out near the ground through the wing wall. You don't see it in this picture, but the outlet air pipe comes out of the box and turns straight up and has a small turbine on it to help pull air through. I have small muffin fans on the inlet and outlet to pull and push air through for the times we might need to stay in the shelter during a storm.
I don't have a recent photo of the inside, but here is the basic layout. The batteries now live in an aluminum box under the inverter. You can also see the fans mounted to adapter flanges that I printed. The flanges allow the conduit to pass through as well. I'll try to get a photo of the finished electrical the next time I'm there.
Hooking up the batteries in the aluminum box was a bit tedious. I had to do things in the correct order to help ensure that I could not drop anything metal on an exposed terminal. You can see the red plastic covers that I printed to help reduce risk and to warn anybody who gets nosy. Note that the positive terminal is protected under the plywood shelf and by a flange at the back of the box.
Hooking up the batteries in the aluminum box was a bit tedious. I had to do things in the correct order to help ensure that I could not drop anything metal on an exposed terminal. You can see the red plastic covers that I printed to help reduce risk and to warn anybody who gets nosy. Note that the positive terminal is protected under the plywood shelf and by a flange at the back of the box.
Consumerbot3418
Fitting square pegs into round holes... for fun?
Always nice to kill two birds with one stone! 
Do I correctly understand that you intend to occupy the shelter, along with your LFP batteries, during a category 1 or 2 hurricane? Maybe it's safety overkill, but I wonder about being "trapped" in your shelter during a hurricane along with the battery bank and inverters. What if the magic smoke happened to come out at the wrong time (Murphy's law)?
Do I correctly understand that you intend to occupy the shelter, along with your LFP batteries, during a category 1 or 2 hurricane? Maybe it's safety overkill, but I wonder about being "trapped" in your shelter during a hurricane along with the battery bank and inverters. What if the magic smoke happened to come out at the wrong time (Murphy's law)?
We were still working on the panel mount during the heat of August, but with the roof mostly covered and exposed to direct sunlight, the dirt was about 127*F, the air was 109*F, and the inside back wall of the shelter just above the batteries was 89*F. I expect that will be lower next summer since the dirt is now complete and the panels provide shade during the hot part of the day. I plan to add an additional shade to the sides to improve the shade before and after noon.
The panel mount sits on top of the shelter and has cable tie downs to the lift rings of the shelter. I used the online calculators from Iron Rack and others to determine that I should expect about 1,500 pounds of lateral force and only a few hundred pounds of uplift in hurricane winds with the panels level. I scrounged enough pipe, hat channel, and angle iron to build a tilting rack that allows me to set the panels in ten degree increments from 0* to 50*. Door hinges provide the tilt action, and plates with drilled holes allow me to through bolt the rack to the support pipe to hold the angle.
The panel mount sits on top of the shelter and has cable tie downs to the lift rings of the shelter. I used the online calculators from Iron Rack and others to determine that I should expect about 1,500 pounds of lateral force and only a few hundred pounds of uplift in hurricane winds with the panels level. I scrounged enough pipe, hat channel, and angle iron to build a tilting rack that allows me to set the panels in ten degree increments from 0* to 50*. Door hinges provide the tilt action, and plates with drilled holes allow me to through bolt the rack to the support pipe to hold the angle.
No, I only intend to occupy the shelter during a category 3 or higher hurricane. Category 1 or 2 is nothing to leave home over. Category 3 isn't either, but once they get that large they tend to grow quickly, and they always seem to make landfall at 2 in the morning.Always nice to kill two birds with one stone!
Do I correctly understand that you intend to occupy the shelter, along with your LFP batteries, during a category 1 or 2 hurricane? Maybe it's safety overkill, but I wonder about being "trapped" in your shelter during a hurricane along with the battery bank and inverters. What if the magic smoke happened to come out at the wrong time (Murphy's law)?
Everything we do has risk involved. The batteries are opposite from the door and in an aluminum box. The door opens inward. The whole thing, including the panels, is below average terrain. I'm pretty sure we are safer in that box overnight than we would be on the highway trying to evacuate.
The rest of the plan includes taking the tractor and backing it in next to the door to help block direct wind and support a tree or something that decides to land on it. The chainsaw will be between the tractor and the shelter wall just outside the door.
