Hi Vlad. After reading the entire manifesto and looking at your well drilling rig, I am dead set on building a rig like yours to drill. I live in a dense city and have enough space for 10 boreholes 16 feet apart, but no where near enough for slinky.
I feel I can reach my target price as a total expense, meaning after building the drill I would sell it whole / re-purpose it, or potentially hold on to it and try to build a side job out of drilling on weekends (considering the commercial price this does not seem unreasonable, also people around here hire unlicensed contractors a lot), and so I may spend 5K up front, and recover 3K when I sell the drill / components.
I have a HUGE amount of time to work with, sourcing cheap parts, and the economy here is bad enough that craigslist has major deals. My goal is to begin sourcing/building the well drill ASAP, and have holes (down to 100ft maybe less, still figuring that out) done between Feb and April, while sourcing the AC components between now and then. I also have the entire winter to work, as it doesn't get below freezing for more than a couple hours now and then (even at night).
So here's what I'm planning/working on now:
1) drilling regulations (laws and permits)
2) sizing of system
3) determine best way to move heat out of the air and into the water (cooling and airflow).
1) I took a cursory glance at our drilling regulations, which mention geothermal but are mostly targeted for well water, or oil and gas wells (regulating 20,000ft wells). The city website says a permit costs $10K, but that permit exemptions are a possibility. Unfortunately I will have to wait till Monday to get more information, but will report back for those US urban individuals interested in DIY GSHP, and really hope there is some way around this.
2) system sizing. I'm not sure on this, unfortunately. AC started in the manifesto saying a bit too small is better than too big for 2 reasons: COP will be worse (lower) when the compressor runs for shorter duty cycles, and the cost / labor of the boreholes.
I feel building a large water storage tank (1,000 gallons maybe) will allow me to run the compressor for long cycles to get to temperature, then let it taper off over hours/days, which should give me higher COP and relatively stable temps. If my thinking here is wrong please let me know.
Because I will be building my own drill and providing my own labor, the monetary cost for the first hole will be around 3K, but each additional hole seems to be around $100 or less. I am also expecting I will not have the drill long term, so I would rather spend $300-$500 for extra boreholes and make sure my system is large enough the first time around (similar to Vlad's views on building a drill; over engineer it so you cant fail). If I decide it is too large I can always disconnect boreholes from the loop, but after the drill is gone I can't build more.
3) Currently my house is circulating air with a dual speed 1/4 and 1/2hp blower 24/7 in an evaporation cooler and moves a huge amount of air. As such I imagine I can use the same blower to circulate air across the existing evaporator of whatever AC I end up cannibalizing. This would be extremely convenient if it works, but so far I have no clue if this would be effective as I'm still wrestling with the underlying concepts of how cooling coils work. If I luck out I may find a salvage commercial air handler that is designed for water to air central cooling.
If anyone has relevant information I would hugely appreciate it. I'm sorry if it seems I'm dismissing your idea for the cooling tower Vlad, I just don't have any idea how effective it would work, while i have seen examples of chillers and know they are effective. If you have any references I could check I will, but I need to be confident the end result will function as well as an appropriately sized central air unit from Sears.
Thanks
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