The Homemade Heat Pump Manifesto

[Daox]

Looks pretty good. I'm betting you could make something like that clamping tool with some ~3/4 ID steel pipe. Cut it in half, put a hinge on one side and weld a bolt to the other side with a tab on the other half and use a nut to hold it together (kinda like the tool has). Make two of those and put them on a vise grips or c-clamp or quick release hand clamp of some sort. I'm not too sure about the heating of it. Any electric heating element could possibly work. Perhaps an electric skillet? Those are my ideas. I'm loving the progress though!

[AC_Hacker]

I took my Polyethylene weld tests down to show Howard-the-Machinist this morning. When I showed him what I was able to do with a Teflon skillet on the kitchen stove, he was rightfully impressed. So impressed in fact that he volunteered to do some destructive testing to see how good the welds were. He fixed a 3/4 piece of steel rod in the bench vice and used another piece of 3/4 rod to try and tear the welded pipe apart. One weld broke pretty easily. It was a weld on which I had tried minimum heat. You could see at the torn cross-section that some of the end was still shiny and had not even melted from the heat of the skillet. The other welds were so strong that the poly pipe gave way before the weld did. Pretty impressive. But I can see just how much better it would go with a device that was along the lines of the Mini-mac. So could Howard. He showed me some online sources for 'cartridge heaters' that came in various wattages and temps. They ran about $35 each. He also said that he'd mill out a chunk of aluminum for the cause. That's no small favor. It's good to have friends in high places...

Before I left I introduced my Teflon skillet to Howard's bandsaw.

This will give me non-stick surfaces for fusing the poly pipe.

On the way back home, I stopped into Goodwill to look for resistance-heating devices I could savage to heat my home-made polyethylene fusion machine(AKA: 'Mini-Hack'). I had plenty to choose from: hair dryers, clothes irons, waffle irons and finally I found just the thing... a mini electric sandwich maker:

This device drew 600 watts, which I properly guessed ran 300 watts per side:

I got really lucky because it even has a temp regulator. Who would have guessed that sandwiches cook at the same temp as the fusion temp of polyethylene

UPDATE NOTE:
On subsequent posts you will see information volunteered by a reader with far more polyethylene welding experience than I will ever have. Owing to his suggestions, I have passed over the mini-sandwich maker's thermostat because it doesn't allow the heat to go high enough. I have instead decided to go with an electric skillet temp controller because it allows temperatures up to 450 degrees F. I have also wrestled with the fabrication of a simple-to-make answer to a device like the Mini-Mac:

Let there be no mistake, this is a really well-made piece of equipment and a professional ought to trust his work to nothing less. However the price of the Mini-Mac and heater is about $2000, so resourcefulness must prevail.


So here is my current thinking on how to de-technify a device to precisely join poly pipe for fusion welding:

In the background is the jig for centering the pipe. I built it on a large L-bracket. The smaller angle was welded in place first, before cutting out the section from the middle, thus assuring that the two sections would be in line. Since my house is small and well-insulated, it will require a pretty small loop field, so I'll be able to get by with just 3/4" pipe. The operation will require two people, one to hold the heating iron, the other to hold the pipe in place and to apply force on the pipe when the fusion temperature has been reached.In the foreground, bottom-right is the electric skillet heat control (temp control goes over 450F), in the mid-ground, middle left is the heat-cell which I made from the band-sawed Teflon skillet and the 300 watt mini-sandwich heating element. I'll post more detailed photos in a couple of days.

Still have a few mechanical problems to solve before the Mini-Hack meets the poly pipe. I ordered 200 feet of poly pipe five days ago, should arrive in about a week.

[EDIT: Here is a picture of the finished fusion tool. Lethal voltage just a fraction of an inch away from my fingers. This must get fixed before it is plugged in.]

Regards,

-AC_Hacker

P.S.: I just located some good, free industry literature. The Plastic Pipe Institute (there is such a thing) has a book called Polyethylene Pipe Handbook which can be downloaded chapter at a time here:
Handbook of PE Pipe

...of special importance is the chapter on "PE Pipe Joining Procedures" located here:
http://plasticpipe.org/pdf/chapter09.pdf

__________________________________

[metroschultz]

Originally Posted by AC_Hacker

metroschultz,

Pump & dump? I'm not so sure I follow what you mean...

I see this term in geothermal usually meaning that an 'open loop' system is being used, and water is being drawn from the ground or river or other water source then heat is extracted and the water is then pumped on to a lake or a river or a different well where it is absorbed back into the earth.

Is this how you mean the process works?

Regards,

-AC_Hacker

Yes,
That is exactly what they do.
Pump fromthe ground water table (to an underground storage tank)
and dump back to the water table (through a leeching field).
Several of the units in my neighborhood have had their leeching field sink. (sinking field = mucho denero)
We live near the ocean and the water table is just below the surface..

[AC_Hacker]

Originally Posted by metroschultz

Pump fromthe ground water table (to an underground storage tank)
and dump back to the water table (through a leeching field).
Several of the units in my neighborhood have had their leeching field sink. (sinking field = mucho denero)
We live near the ocean and the water table is just below the surface..

Sounds horrible. A lot of states only allow closed loop GSHP systems, I used to think it was too restrictive, but with what you're telling me, it makes good sense.

Somehow this all reminds me of the colossal financial mess the whole USA is embroiled in... Possibly the same players.

Regards,

-AC_Hacker

[metroschultz]

What is truly horrible is that in this city we are not allowed to have "Grey" water systems. With my wife and daughter and grandson here (plus the influx of people on the weekends) I would love to be able to make a grey water system for the toilets (like Ben's). I wouldn't need to wait for the toilet so I could wash clothes. I would be adding fresh water for the toilets.
All the water in the home has to be clean and clear, either city water or purified ground water ( for the few homes left with wells and pumps).
They allow the thermal systems because some developers lobbied for and exemption. The same developers that built this neighborhood and several others.
I believe they had some deal with the heat pump guys to get it going.
Maybe it was all with the best intentions to start.
I will give them credit for one thing though.
My neighbors with the pump and dump systems pay only a fraction of what I do for A/C in the summer.
I have 1500 sq ft and pay $200. for electric in June, July, August and Sept.
My closest neighbor with the system has 3400 sq ft and pays half that.
He is waiting for his backyard to collapse.
The house next to his went sinkhole last year and it cost them dearly. Don't ask, I don't know all the details but it has something to do with the insurance or lack of it or not enough coverage or .....whatever.

[AC_Hacker]

metroschultz,

I'm not sure where you live, but here in Portland, Oregon the city is being extremely slow to make progress on greywater.

In the meantime, quite a few citizens have taken charge of their own lives and are quietly and safely operating greywater systems.

-AC_Hacker

[metroschultz]

I have considered that.
Too afraid of big brother.

[AC_Hacker]

Most of the sources I respect advise doing a heat transfer test to determine the rate at which heat will be transferred into the earth (for cooling) or out of the earth (for heating). This transfer rate will be the same in each direction, and will determine how much loop-field (trench or borehole) will be required to heat or cool your house. This is important because the loopfield is the most expensive part of the GSHP installation process if you are hiring it out, and is a lot of work if you are doing it yourself. So it's a good idea to get it right. Too little loop-field won't be able to supply the heating or cooling required. Too much, while not such a bad idea, means greater expense and greater work.

So I went on a google-frenzy to try to locate testing and evaluating proceedures, and after many, many hours, finally turned this up:

http://www.geokiss.com/tech-notes/TCTestingSum.pdf

So, I consider this test to be my first attempt at testing and likely to be a candidate for improvement, but this is what I did...

I had used a hand auger, meant for fence posts, and had dug to a depth of twelve feet in about 3 or 4 hours. I was going to fill the hole back in, but I decided to try to get some use out of the hole along the way. I buried a double loop of CPVC pipe I had laying about in the garage and attached some garden hose to the input an output of the loop. (see photo)

Then I filled the hole back up with the dirt that I had laboriously augered out and used water on the dirt as I went, so it would settle well.

I hadn't actually found the testing method document that I'm linking to above at the time I started testing, so I was just sort of making it up as I went along. I reasoned that if I introduced a known amount of heat-energy into the CPVC-loop, the ground would absorb the heat-energy at a rate that I suspected would decline. I further reasoned that if I monitored the temperature of the water, it would tell me something about the rate of absorption of heat by the ground. If the ground absorbed the heat at a high rate, the water temperature would be low, if it absorbed the heat energy at a lower rate, the water temperature would be higher.

So here's a sketch of my setup and a few photos:

this shows the hole I'm doing the tests in. I used CPCV pipe (not recommended) with a double-loop (not much advantage over a single loop)...



I thought it would help to eliminate error if I used good pipe insulation on the hose. Bottom photo shows digital thermometer and kill-a-watt. A good analog thermometer would work just fine, but the digital is much easier to use. The kill-a-watt meter has a 'watt' function. It was set up to measure both the pump & the heater together, since they both give off heat. I found that the watts vary over time, so they need to be recorded at every chosen interval. It also has an elapsed-time function (called 'clock'), very handy.


this shows the set-up in the cooler box. I initially thought that it would be a good idea to put the coffee cup warmer inside of something so it wouldn't melt the foam box. I nixed this idea, and suspended the heater from the hose with a bread wrapper twist-tie.

If you read the proceedure I am using for my guide, you'll notice that the proceedure call for measuring the input and the output temperatures from the ground loop that is under test and arithmetically averaging them. I made the simplifying assumption that the water swirling around in the cooler box would physically average the temperature.

(NEXT POST: thermal transfer test data & analysis)

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[AC_Hacker]

So here's my test data & analysis...

Time Temp
____________
0.00<tab>54
0.133<tab>57
0.167<tab>57
0.50<tab>60
1.733<tab>70
4.00<tab>79
6.25<tab>83
7.50<tab>85
8.433<tab>86.5
14.833<tab>92
15.25<tab>92
15.517<tab>92.5
19.883<tab>96
21.00<tab>96
22.083<tab>97
24.03<tab>100
25.82<tab>100
27.65<tab>99
31.67<tab>99
40.317<tab>99
44.23<tab>101
49.60<tab>102
63.65<tab>102
68.93<tab>103
89.55<tab>106
102<tab>107
113<tab>107
123<tab>108
143<tab>109

(I had to use the "<tab>" thingies, because the real tab didn't appear correctly in this blog)

Since I don't have an automatic data logger (yet) I logged all the data by hand. The time intervals were irregular but I think that it doesn't matter so much.

The first thing I did was to put the data into a curve analysis program. The program I found is a really great shareware program called CurveExpert for Windows available here: CurveExpert 1.3: Download

I've used this program for lots of things. There are even tutorial pages available, if you need.

At any rate, it was very useful to get well done graphs as the test progressed. The program does automatic curve fits and it was interesting to see that the program selected various curves before finally settling on an MMF type curve.

heat transfer curve

From CurveFit, it's even possible to get the equation of the curve that is the best fit and to project the curve forward in time. I was interesting to predict what the temperature would be at a particular time and to check the results as they came in.

But this wasn't really getting me what I needed, which was a quantified characteristic of the earth formation in my yard. This is where the document mentioned in the previous post: TCTestingSum.pdf, came to the rescue.

I tried to follow the proceedure but wasn't able to get the same results as the author had. Either I was making a mistake, or I was using a version of Excel that was older and didn't have the exact feature he was using. But I devised a work-around and got reasonable results.

Here was my proceedure:

1) Start Excel
2) Open the data from a tab-delimited text file. This just means that the data is written in a test file and you hit the 'tab' key after the Time data, but before the Temp data. If the tab could print like this: <tab>, your data would look like this:

...
0.00<tab>54
0.133<tab>57
0.167<tab>57
...

Anyway this is a standard text format that Excel understands.

...of course you could just enter the data straight away into Excel and I could save myself some time & typing.

If you graph the data I have included, it would look like this:

See picture

Looks similar to the graph from CurveExpert.

At this point, the author of TCTestingSum.pdf was able to do a right-click on the graph curve that Excel made. Then he was able to choose "Add Trendline" and then a Logarythmic trendline, and the result, as illustrated, was a linear graph. I was not able to get these results, certainly not the graph as illustrated. So my modification to the process was to return to the spreadsheet, 'Insert' a column between the Time data and the Temp data. Then I wrote a simple formula (=ln(A1)) that took the natural log of the data in the time cell. I copied this formula down to the rest of the data cells. Then I made another graph of these data columns, "ln(Time)" and "Temp". At this point, I got a graph that resembled the illustrated results.

line slope graph

I then did the right-click and 'add trendline' this time I chose "Linear", since the natural log function had essentially linearized the graph. This did give me a formula with slope. Then I was able to use the rest of the proceedure as described. This all gave me a "k" value of 0.569464441. I was in turn able to use this value to calculate the total length of borehole, which would yield 12,000 BTU/hr. This calculated borehole length came to 214.23 feet. Which is reasonable, as I hear from local installers that they estimate that 12,000 BTU/hr (AKA: one Ton) borehole length to be in the range of 175 to 225 feet.

I have attached my spreadsheet for your consideration.

Some improvements:
* Get a real data logger
* Use the actual type and configuration of Polyethylene pipe I plan to use in the actual installation.
* Use a borehole that is closer to the actual location of the installation (the test borehole was within three feet of my basement, so error is to be expected)
* use the type of grout I plan to use. I'm currently planning to use "mix-111", more information available here:
Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

I welcome your comments.

Best Regards,

-AC_Hacker

P.S.: For those who want to know more about the topic of borehole testing, I have located what might be the definitive paper on the subject:

http://epubl.luth.se/1402-1544/2002/...DT-0239-SE.pdf

P.P.S.: Here is a link to a report from a professionally done borehole test. Note the unusually high results and the speculation as to why such unusual results were obtained.:
http://www.tva.gov/commercial/TCStud...iles/Se-02.pdf

...and another done in Alabama in 2000. These are more typical results.
http://www.tva.gov/commercial/TCStud...iles/Jo-18.pdf

...and yet another done in Illinois in 2008.
http://www.midwestsustainable.com/Co...%20Example.pdf

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[jwxr7]

I am very interested in your thread. Nice work so far too . You shop at Goodwill too, one of my favorite places to check , right up there with garage sales!
I have been wanting to mess around with heat pumps. I can get ahold of old ac units and dehumidifiers but have been afraid to mess with the original plumbing. It's just something I haven't had much hands-on experience with. What did you have to do to the Ac unit you converted in the picture you posted in the beginning of the thread?