Geothermal - Video 5 - Design Rules of Thumb

[@TheGalacticWest]

My man we are all perfectly ok that you did that in KW even Americans don’t know what a BTU is.

[@zacschmelzer8487]

Excellent video. I have a 3 ton unit for an insulated barn. It should have a 5 ton or bigger for heat though. Two questions. Can I upsize the length of pipe to match a 5 ton system or keep it at the furnace size of 3 ton? Does pipe diameter mater much? Mine has hookups for 1.25”

[@tomvermeulen1082]

What an excellent video. It is so informative and I very much appreciate the time you have spent on it. I do wish there was a little more information on the slinky style. If you have any more information on that or a link to another video or a future video I would be greatly appreciate it. Again, stellar job and thank you sir!

[@PaulAverett-e2o]

I know this is an old video but I have a question if my plan is the most effective. I have 10 acres and have to run Water and Electric utilities about 600' from the road to my home. I will have 1 trench 3ft wide for the utilities to be separated 36" horizontally and vertically required by code but not less that 24" from surface. Inside of the same 600' trench, at a depth of 10' can I "fuse" 5 "slinky-loop circuits into 1 continuous circuit (basically 2500' of 3/4 HDPE “single-slinky” for the 4 ton unit). Then repeat the process at 8' and again at 6' in the same trench. The only difference is each HDPE “single-slinky-circuit” line will be the correct length (+25%) for the required ton. I will have 3 different heat pumps located in 3 different areas. Right side of house in attic (4 ton/ 3/4" 2500'), left side of house in attic (3 ton 2,000' 3/4" HDPE) and one in the shop in attic (2 Ton 1500 3/4" HDPE). I live in an area where we pour concrete slabs with a 24" x 24" footer, no crawl space, and the water table is high. I am on a slight hill “8ft’” but plan to hit water around 6-10 ft. It will be difficult for me to have up to 8 separate 3/4" HDPE lines coming into my slab at 3 different areas then a manifold above slab. My thought process is by fusing and having 1 continuous "single-slinky" circuit, I will be able to avoid a manifold and only have a single supply and single return line coming through my slab (or above slab in an insulated pipe) at each heat pump unit. Wrap that line above slab in foam and run into the attic where each heat pump will be located. -Thanks in advance

[@pradeeppandiaraj]

Thank you this video was the best explanation .I’m a full time green energy consultant in India.really awesome n

[@navin6mis]

Excellent video with actual information needed. Thank you!

[@CMZneu]

Great video! but i'm a bit confused about the the ground temp at 30 feet, you said it should be the average air temp of the whole year but idk i thought i was cooler than that like at least a few degrees.

[@davidsvarrer8942]

334 Joule must be removed per gram of liquid water at 0°C to make it ice at 0°C. This makes 334,000,000 Joule to be removed from 1 tonne of water to make it change from liquid to firm state. 334 MJ is another way of putting it. 334 MJ resembles 92.7 kWh - which must be removed from one tonne of 0°C water to make it 0°C ice. If you use a heat pump which is efficient (COP 4 for instance), you would, for each 1 kiloWatt of energy put in, get 4 kiloWatt of energy out, meaning, that pump would remove 3 kiloWatt energy on a continous note. 1 kiloWatt is the same as 1000 Joule per second (conversely, 1000 Joule equals 1000 Watt-seconds). Thereby, if you remove 3 kiloWatt energy, then over 1 hour, you would have removed 3 kiloWatt-hours. So, you would need 92.7 / 3 = 30.9 kWh of power to make 1 tonne of water at 0 degrees turn into 1 tonne of ice at 0 degrees with a heat pump. I hope this makes sense?

[@ProjectLeapFrog]

Hi, Dr Mulford. In areas where space is an issue, what are the drawbacks of drilling fewer wells at deeper depths? Deeper is better for constant temps, so why 8 wells at 125ft vs 6 wells at 166ft to reach 1000ft of wells? (Lets assume Ohio where heat and cooling loads are relatively similar)

[@cjimcook]

I'm confused by your remark at 19:00 where you said, "Your borehole will be twice the length of pipe". Don't you mean your pipe will be twice the length of the borehole? If not, what am I missing?

[@rydgemulford]

Thank you for catching that. It appears I should have said "the pipe will be twice the length of the borehole".

[@victorgalvez927]

wow, quite a lecture!! super informative I really apreciate it! Bravo!

[@Bob-de1qi]

Great summary video and great series, reminds me of engineering school. Thanks. Do you have anything comparable for Direct Exchange (DX) Geothermal where water is replaced by refrigerant in the loop? What is your opinion of DX?

[@TobiasZiggy]

An excellent video and explanation on the exact right level for depth of information! Nice lecture!!! Interesting especially the last slide about the length of trench / borehole at different pipe configurations. Left me wondering how comes that with increasing avg ground T trench length needed increases. Seems counterintuitive as the necessary heat exchange per meter of trench should increase with higher avg T?! However the graph implies the opposite and I still can't wrap my mind around it why that is... Obviously missing something here. In any ways great educative video, elevating the level of understanding. Keep up the good work! 👍

[@tobymartin3265]

I think he's considering heating in the winter along with cooling in the summer...so there is a sweet spot for cooling AND heating. I'm in Texas, so I'm primarily interested in cooling and thought the same thing. I'm curious that a 2 pipe config is the least efficient... Again, I'm assuming here - but maybe the multiple pipe config is a single loop? I can see more pipe being more efficient. Originally, I would think the slinky would be the least efficient, but it must be pipe length - 150 ft of trench, with say 700+ ft of pipe is more efficient, than the 2 pipe at ~700ft of pipe.

[@lorezyra]

This would be far better as a simple webpage rather than a video...

[@mlee81]

Thanks for the vid. So basically the slinky style is going to be the most efficient for closed horizontal loop

[@boxelder9167]

It’s going to be the most cost effective. The efficiency is going to depend a lot on the soil type in contact with the pipe and the moisture in the soil. I am thinking about using earth tubes that use air and a solar powered fan. I have 3 acres so lots of room for a straight run. I also thought I might put a slinky in the trench also so if I decided later that I wanted to tie into a heat pump I could and use the air pipe to feed a greenhouse/wrap-around sun room and pull the air in with a solar chimney. That would basically make my only heat loss from the roof.

[@CMZneu]

@@boxelder9167 Did you do earth tubes? Did they perform ok? was thinking about doing them but they have so many cons compared to a closed system with pipes like in the video.

[@boxelder9167]

@@CMZneu - I ended up getting a standard heat pump from my neighbor who gave me a big discount on it. I currently use it for the AC and heat with wood for the fact that the wood is free. I got hit with $24k in back taxes for capital gains selling my other properties I wasn’t expecting so that kind of shut down my projects to a minimum.

[@CMZneu]

@@boxelder9167 Sorry to hear that.

[@rathermelc]

Is it worth insulating over the top of your horizontal pipe field?

[@rydgemulford]

I wouldn't think so. The ground is insulating enough that it would be hard to make the investment of all that insulation worth it.

[@rsnell22]

I have witnessed a highly engineered, multiple vertical well loop fail to get even close to design temp difference. Use some sort of horizontal layout.

[@lorezyra]

"English units..." 😞

[@davidsvarrer8942]

English units? Eeeeh? Thanks a lot for your great and excellent video, however, English units, that's not workable :-)... YOu can barely call anything English or Imperial units anyway, because there is no commonality about them. These are so diverse as new born puppies...

[@bobjoatmon1993]

For American consumption, you want metric units go to a European site

[@davidsvarrer8942]

No. Not 3.5 kiloWatt. kiloWatt-HOURS... :-)

[@rydgemulford]

Thanks for the comments and for keeping me on my toes! After watching this again I realize that I forgot to specify that a ton is defined as the rate of heat necessary to freeze 2000 lbs of water at 0 degrees Celsius in 24 hours (the 24 hours being the part that I forgot). This is what allows us to express a ton as a heat rate as it is a quantity of energy removed over a period of time, hence 3.5 kW instead of 3.5 kWh (en.wikipedia.org/wiki/Ton_of_refrigeration). I completely agree about using only SI units. This is one of the few lectures in all of my classes when I don't work in SI units, because they make way more sense. Thanks for watching!