The Homemade Heat Pump Manifesto

[jeff5may]

The main thing i would be thinking about is to try to ensure turbulent flow in the refrigerant-to-water heat exchanger. It is much smaller than the loop field and has to work harder.

[AC_Hacker]

Originally Posted by jeff5may

The main thing i would be thinking about is to try to ensure turbulent flow in the refrigerant-to-water heat exchanger. It is much smaller than the loop field and has to work harder.

This is an advantage that brazed plate HXs have, because of their close plate spacing and opposing herringbone pattern, turbulence is assured. They also have an advantage of large surface area for their size, and lastly, with the exception of the outer surface of the outside plates, all surfaces are engaged in transferring heat.

-AC

[stevehull]

Originally Posted by jeff5may

The main thing i would be thinking about is to try to ensure turbulent flow in the refrigerant-to-water heat exchanger. It is much smaller than the loop field and has to work harder.

Jeff,

As AC has mentioned (in the prior post), many of the efficiency issues have been settled in the internal heat exchanger (HX). Yes, more can be done, but a lot of the issues have been solved and only minor gains can still be had there.

As to the outside loop. Putting in a set of vertical or horizontal loops remains one of the dominant costs of a GT installation. One ton per vertical loop (~200 feet) costs about $1500 - $2000 in loose granular sub-soils. If in rock, then multiply that by several fold. This number approaches the actual installed cost of the actual heat pump. This loop cost (or drilling difficulty) is the major issue that impedes costumers from adopting closed loop situations.

There are many loop efficiency issues to content with - and they are solvable! Imagine a loop cost being decreased by 50% or so. This would allow far many more customers to adopt this technology.

Physics prevents me from creating turbulent flow outside the loop, but engineering allows me to maximize internal pipe conditions.

To AC's questions, the loop fluid issue is being funded by a major USA company (not hard to figure out as there are really only two). The addition of simple alcohols is easy to do and inexpensive, but at concentrations above 50% (where viscosity really decreases), then there is degradation of the HDPE. Glycols, necessary in cold weather applications are more viscous than water. The key is to find a combination of pipe and fluids that allow low temp use, have the long life of HDPE, have the high thermal conductivity of HDPE and are easy to fuse/connect together. Sorry, can't reveal the fluid.

The die for making internal spiraling on the inside of the HDPE is not hard - but putting internal divots in there is tough. Several mechanical engineering teams are thinking on this.

The surface area x heat flow issue is intriguing. Maximize surface area, maintain turbulence and increase heat flow across the tubing.

As for the DIYer - I have a lot of faith in direct exchange (DX) applications. You can increase the heat flow by using copper. You can also hammer small divots from the outside of the copper using a small punch to create internal divots. This creates turbulence. And a LOT of soft thin wall copper can be put in a small volume. But to do this, you need to build several heat exchanger "nests" that reside in the bore hole pipe. Lots of parallel tubes with 180 degree soldered bends also assists with turbulence.

Copper is simple to solder and cheap supplies can be had at any recycle yard. As an aside, I find it staggering that installers throw out a 150 foot roll that has one flattened area in the middle (caused by some truck backing up and crushing that part of the tubing). The other 99% remains perfect!

Depending on the ground temp, you can put a LOT of exchange surface using copper compared to plastic.

Copper also has issues. You have to know your soldering technique, be careful of cracks and to use a fluid that is close to neutral pH. But all this can be done by the careful DIYer. There is a lot of resistance from water quality people that are scared that aquifers will be contaminated if a loop installation goes bad. But a monitoring situation is easy to set up (detect loss of loop pressure for example).

Steve

[thumperoo]

All this talk of turbulent flow and developing solutions seem like a hassle. Best closed loop is an open loop. You can't get better heat transfer than water percolating thru sandy soil. Not everyone has that ability but developing twirly tube and/or injecting air bubbles are just fixes - not solutions. Deep wells are - well - expensive. Direct expansion systems use much less surface area, but, cost huge in copper. Trenches and plain pipe are ... not fun. I like our 1/2 hp jet pump sucking constant 49 deg F water from a sandpoint just fine. We've been using our grey water weeping field as the reject for the last two years now with no worries. Did I say - I hate closed loop. Thermodynamics hates closed loops. ;(

Pump and dump !

Thumperoo

[stevehull]

Thumperoo,

I also love open loop (aka "pump and dump") and have one at my current home and farm. But city lots can't do that . . .

Yes, I agree that the thermodynamics of the open loop (almost constant inlet water temp) maximizes efficiency, but there are places where the water quality makes open loop applications VERY problematic.

In my opinion, we will look back in 30-50 years and grunt "uggh" when we think about burning oils to keep houses warm (just like today we look at homes with coal bunkers in the basement and the need to remove coal clinkers every other day from the burner). The vast majority of homes will be heated and cooled by GT heat pumps - which is really a solar application.

But to do that we need to have a way to more inexpensively couple the ground to the heat pump. That is where turbulence, equations and such are important to discuss.

Ohh, and I also use my outflow "pump and dump" water as a water source for watering my livestock. Keeps the water tubs cool in summer, warm in winter and never slimy. So I certainly DO like open loops! And the outflows from there fill a pond that I use for pasture irrigation.

Steve

[AC_Hacker]

Originally Posted by stevehull

As for the DIYer - I have a lot of faith in direct exchange (DX) applications. You can increase the heat flow by using copper.

In the studies I have done, the copper/DX advantage is around 15%. Intuition would suggest it would be far greater, but in the grand scheme of things, the thermal resistance phenomenon is very much like several resistors placed in series, and the resistance of the pipe wall turns out to be one of the smaller resistors, so radically changing its value doesn't have a radical effect on the whole system. Personally, I think that most of the DX advantage comes from eliminating a HX (the rule of thumb is 10% per HX).

Originally Posted by stevehull

And a LOT of soft thin wall copper can be put in a small volume. But to do this, you need to build several heat exchanger "nests" that reside in the bore hole pipe. Lots of parallel tubes with 180 degree soldered bends also assists with turbulence.

Is this your own hunch, or is there more to this story? I'd like to know your experience or references or studies about this. My own experience is that heat movement in ground is much more like molasses. Prove me wrong, Steve.

I was surprised to read in the IGSHPA manual that putting in two (HDPE) loops in a borehole increased heat transfer by only 4%... I would have expected 40%.

Originally Posted by stevehull

Copper is simple to solder... You have to know your soldering technique...

Are you suggesting that refrigerant pressure and temperature cycling can be effectively contained by solder joints? In the trade, they braze. They might call it soldering, but it is brazing, using phosphor/bronze + silver.

Originally Posted by stevehull

...use a fluid that is close to neutral pH...

Depending on the locale, ground PH can eat copper pretty quick. In Norway, they were figuring a copper loop life of about 30 to 40 years. They also studied using stainless instead, but decided that an inexpensive, very long lived, but somewhat less efficient loop was best.

Originally Posted by stevehull

But all this can be done by the careful DIYer. There is a lot of resistance from water quality people that are scared that aquifers will be contaminated if a loop installation goes bad. But a monitoring situation is easy to set up (detect loss of loop pressure for example).

If you're doing Direct Expansion, a loop faillure means you have contaminated your soil with refrigeration lubricant. If you live in an area where it is just fine to contaminate soil with compressor lubricating oil, I guess it's only your conscience you'd have to deal with. In areas like Oregon, with a strong Department of Environmental Quality, you'd have to deal with your conscience and also the fury of the State.

So, when there is a copper DX loop field failure, what exactly is the procedure to remedy the situation? I mean... location of the leak, how would that proceed... and remediation of contaminated soil, what would that look like?

I think HDPE has a lot going for it, a 'guaranteed' life of 50 years, and a more realistic life of 200 is pretty darn good. I mean if our forebears had put in HDPE loop fields all across America in 1813, we'd still be able to use them today.


Best,

-AC

[stevehull]

I am assuming that a peripheral heat exchanger be put in water contact in a bore hole and not in the ground (as in buried in soil). I do not have a lot of faith in a flat copper plate, buried in the ground, absorbing/radiating many BTUs.

My mistake to use the work DX as in direct exchange. I would replace the vertical loop with a loop with a "nest" of copper tubes in parallel, with several of these exchange nests located in the vertical bore hole each suspended in the static water column.

This replaces the long vertical loop, and does NOT contain refrigerant.

The above is a low pressure application and conventional soldering techniques can be used as there is NOT high pressure refrigerant. If a blow out occurs, yes, you do have to deal with a fluid in the aquifer, and that is why so much research is going on to prevent this and also to have a biologically compatible fluid.

The question I am relying to is "what can the DIYer do?" They can build, rather inexpensively, a set of copper based heat exchangers that sit in a deep bore hole of water. These can be built with simple techniques to accelerate turbulence (dimples) to maximize heat transfer.

The use of thin wall type L copper pipe can be used in water situations where water quality will permit.

The industry is trying hard to come up with other solutions. There are ceramics that are being looked at (tremendous heat transfer capabilities) and other exotic metals, but it is hard to compete with HDPE. It is quite inert, takes a lot of pressure, inexpensive, long lived, flexible and simple to fuse.

But conventional bore holes with HDPE vertical loops are expensive . . . and are curtailing the acceleration of the industry.

Steve

[AC_Hacker]

Originally Posted by stevehull

The question I am relying to is "what can the DIYer do?" They can build, rather inexpensively, a set of copper based heat exchangers that sit in a deep bore hole of water. These can be built with simple techniques to accelerate turbulence (dimples) to maximize heat transfer.

So, if I'm understanding, you are suggesting copper, specifically scrap copper, because copper pipe purchased new is so horrendously expensive. And you are willing to accept shorter loopfield life in order to give DIY folk an easy workable material, right?

Well, since HDPE is really pretty cheap, and a big holdup is that it is not particularly turbulence inducing... why not make an electrically heated "dimpler" (newly coined word, I claim all rights, and lefts). I mean I made a thermostatically controlled HDPE fusion device that usually cost $1000+, for $7 from a teflon skillet and a mini-paninni maker heating element (you did see that in the manifesto, right?).

So how about a dimpler that is a bit like a cross between a waffle maker and an "Iron Maiden", electrically heated and thermostatically controlled.

In fact, an awesome EcoRenovator might even be able to put a twisting feature in the dimpler, too.

Maybe even make two heated wheels that could continuously process a length of pipe.

Wow, the possibilities are staggering.

Originally Posted by stevehull

But conventional bore holes with HDPE vertical loops are expensive . . . and are curtailing the acceleration of the industry.

I really wonder about that. I read that in Europe, the whole thing can be installed, enough to heat a house for $6K (US). Of course their houses are much more sensible, as ours will become when we end our military subsidy of oil.

I actually paid good money to go to a GSHP installers training and certification, and industry self-protection and profiteering were everywhere to be seen.

In fact... I was so upset that I started a blog called, "The Homemade Heat Pump Manifesto", in order to empower people to self-install this wonderfully efficient heating method, and make an end run around those fat cat idiots that are trying to enrich themselves at other peoples expense, by colonizing, controlling and obfuscating information.

Knowledge is freedom, knowledge is power!

-AC

[stevehull]

AC,

I frequent the scrap yards and I am amazed at the "scrap" copper that only has a marginal kink, dent or bend. Yes, I certainly do advocate using the best cost material that can be found.

The concept of the Iron Lady is FANTASTIC!! I certainly chuckled when I saw it. And yes, the electric powered Pannani iron is also clever. After a few tries, you got it working - which is the goal.

But what about my brother, who can't recall "righty tighty, lefty loosey" with a socket wrench? Not everyone has the time, brains or initiative to do it as has been you and others as described here.

But without large subsidies, loop fields, equipment AND installation, geothermal heat pumps are a long stretch for $6,000 USA.

I can tell you that a 2.5 ton Waterfurnace unit wholesales for about 1/2 that of the "retail" price. And as more are sold, they become a commodity rather than a select item.

Here is an interesting approach on loops by a city close to me.

In Edmond, OK, the local electric (city owned) company is considering putting in vertical ground loops in city lots and tacking the cost (no interest) over 30 years onto the deed (800 feet total, four loops). The amount $20-25 per month is not much more than the trash fee . . . It is felt that this approach can get more residential owner to go with geothermal heat pumps.

Here, the summer peak load for electricity is some 3 times that of the winter peak and the utility has to purchase power based on the yearly peak. Thus by "leveling the curve" the city saves money by decreasing summer AC costs.

The customer saves $, the cost of augmenting electrical distribution infrastructure is lowered and the city saves $. Win, win, win . . . .

Increasingly, here in central OK, we are on large scale wind power with natural gas back up and then coal as a further base. But as the costs of coal increase, the mix will be more and more that of wind and gas.

As individuals, it is hard for us to control costs, but we can do everything to maximize the kWhr costs with rational use of energy.


Steve

[AC_Hacker]

Originally Posted by stevehull

But what about my brother, who can't recall "righty tighty, lefty loosey" with a socket wrench? Not everyone has the time, brains or initiative to do it as has been you and others as described here.

The EcoRenovator site in general, and the Homemade Heat Pump Manifesto thread in particular, are not aimed at people such as your brother. Not only would this web site be of very little interest to your brother (self-filtering), but were your brother to start posting, with his disregard for learning the most rudimentary aspects of mechanics, he would be roundly dismissed (peer-filtering).

This website and this thread are rare pieces of Internet real estate where people with gumption and talent share their work and ideas that either apply to their work, or are tempered by their actual experiences.

We do have visitors who don't understand this and think it is just a "talking shop", and they mindlessly exercise their keyboards (not so different from tossing trash out the window of a car)... which tends to make this rare space as littered and worthless as so much of the rest of the Internet.

Originally Posted by stevehull

• But without large subsidies....
  
• I can tell you that a 2.5 ton Waterfurnace...
  
• Here is an interesting approach
  
• In Edmond, OK, the local electric...
  
• Here, the summer peak load for electricity...
  
• The customer saves $, the cost of...
  
• Increasingly, here in central OK, we are on....
  
• As individuals, it is hard for us to...

I'm glad Oklahoma is doing something.

Steve, this thread is for people who want to actually build Homemade Heat Pumps (not think about it, not hire it out) and for actually building loop fields and all the other related efforts.

Please respect this, and place posts that are not relevant to actually building heat pumps, or actually building loop fields, etc., in the Billiard room, or some other thread where they belong.

This is NOT a talking shop.

Is this clear?

-AC