Passive Annualized Heat Storage/Annualized Geo Solar-Don't Waste That Heat!

[AC_Hacker]

Originally Posted by jeff5may

... They have a habit of making your heat pump explode on a hot, sunny day in mid-summer. Not a bad idea for a heating-only unit, but definitely no good in cooling mode...

Can you please cite reference links to this? It would help to establish the possible credibility of this statement.

-AC

[AC_Hacker]

Originally Posted by Mobile Master Tech

...Boreholes, hacked GSHP, collectors and storage tank details to come!...

MMT,

I'm standing right by my computer to see the rest of THIS story!

-AC_Hacker

[jeff5may]

AC,

Last year, while I was researching methods to improve performance of "average" vapor compression setups, the solar assisted method looked to be high on the list. The more I did my homework, the worse the idea held water. I decided not to pursue the method, since the collector only really helps during heating mode when there is lots of sun.

To get a glimpse of the company and products, google the following:

sedna aire reviews

A "How it Works" document from the manufacturer:

http://www.suncoolenergy.com/tech/How%20it%20works.pdf

The most relevant post describing the major design flaw is here:

Solar Assisted A/C

Some select quotes from pro members...

"Add solar heat to assist with the heating mode - great idea! But adding more heat to the heat that we are already trying desperately to remove during the cooling mode?

Uhhhh . . . maybe I'm just not bright enough but I'm going to have to have that explained to me better in small meaningful and related English words. Because at this point I sure don't get it."- Poodle Head Mikey (post #33)

"The collector is nothing more than copper tube bent into U shapes with each U inside of a glass tube. The tubes are filled with soybean oil and are connected to an oil reservoir at the top of the collector. I think the total capacity was around 4-5 gallons."- Bobberly (post #40)

"What changed to cause the failure?... The environment changed when the outside temperature finally reached the hottest it had been since the system was installed. Original install was November, first failure was in June. My hunch was increased heat = increased pressure and we finally hit the point at which the flare fittings gave. The fittings were replaced and failed again, which I guess rules out substandard parts; it wasn't until a "gunk" sealent was applied that we were able to stop pressure loss from occuring. About a week later, the compressor cut out while running (don't know the cause) early afternoon. By evening (10pm) I fired it up again and everything was fine until the next day in the afternoon when it cut out again." - Bobberly (post #71)

"Here is how it was explained to this tech.
A couple things to remember;
The rate of heat transfer is dependent on the temperature difference.
Just like suction superheat, adding heat does not change the pressure.

The increase in superheated refrigerant vapor temperature, in the solar collector provides faster de-superheating in the top of the condensing (vapor is hotter) therefore more of the middle of the condenser can be used to change the state and thereby, increasing subcooling and at least bring the liquid refrigerant temperature closer to ambient.

We tested, and concluded, it was time we told them to remove our brand names and that adding these solar panels voids our warranty." -hvac21 (post #79)

From information I gathered from these and other sources, I concluded the design and marketing teams had not effectively communicated with each other regarding theory of operation. Either that or the inventor mixed up the rules of physics between absorption and compression systems, and the resulting hybrid design was explained with flawed logic. Choice words were used to fit the end to the means, and the product was released. Convinced consumers had systems installed, a portion of which failed miserably during hot weather.

[jeff5may]

I seem to have missed a previous thread on this subject:

http://ecorenovator.org/forum/geothe...l-ac-unit.html

No shock that there are other skeptical members here...

MMT,

I have been somewhat following your projects on the forum. So far, it seems you have multiple systems in the works:

1. High seer (AC only) air-source unit w/ desuperheater
2. Water thermal store
3. Evacuated tube collector
4. Hacked ground source heat pump
5. Hydronic under-floor heating
6. Under-slab heat injection field

However, I'm having trouble figuring out some details:

A. what runs to what
B. how do you control it all
C. what army built it

What awesome potential this list has! I'm riveting my seat to this thread. I wish you the best of success in composing this literal symphony of engineering.

[Mobile Master Tech]

I've been away awhile, time for a system review and a few changes! Life....

I'm choosing a combo active/passive system. The passive part requires warm soil under my home, approx. 73F instead of its' natural 62F. This will cause heat to move into the house during winter temps but not during the summer, as I would never have the AC set lower than 74F. I have about 2200sqft of uninsulated basement wall and slab, which will be bare or covered in hard flooring or drywall for an approximate U-value of 0.6. A 70F interior temp and 73F soil temp will move about 4,000btu/hr into the house instead of my current loss to 62F soil of around 10,000btu/hr. This passive "heater" reduces its output gradually and automatically to zero as the house approaches 73F. That's a difference of about 11.5 million BTU per month. My max winter usage including DHW and cooking in the last couple years has been about 20 million BTU/month. This continues to go down as I convert to electric cooking, seal gaps, replace windows, insulate, etc.

The active part is collecting heat from the back of PV panels (heavy gage aluminum foil & pipes silicone'd to the back of the panel) and injecting it into borehole PEX loops surrounding the house, then pulling heat from the ground as needed for DHW and hydronic heating using a hacked GSHP. I've decided to do away with the boreholes in the middle of the basement and just let the perimeter heat work its way to the middle over time. There will be more than enough BTU's throughout the year with a 73F heat sink cooling 300+ sqft of PV panel. By the end of winter when I've taken quite a few BTU's out of the ground, the days will be getting longer to provide more.

One Laing variable speed sealless ECM pump taking 25-60 watts will circulate 30% ethylene glycol (enough to prevent burst damage to any temp, freeze protection to 0F) through the closed system: ground loops, then the collectors, then the flat plate heat exchanger for the hacked 2 ton GSHP, then back to the loops. Since the ground loop temp will be around 73F, putting the collectors before the HX means the GSHP may often see inlet temps over 80F, making it very efficient as it charges the buffer tank for the day. A diverter valve will bypass the collectors when their temp is below the ground loops but the GSHP needs to run, or if the ground under the house ever gets too warm. If the collectors have heat to give, but the GSHP doesn't need to run, the fluid just runs through the GSHP HX unchanged. If the GSHP ran continuously it will put out 17 million BTU/month, well more than the 8-9 million BTU max shortfall I project and nearly as much as my current usage.

The output plate HX of the GSHP will use a smaller 15 watt Laing pump to circulate water from a 330 gallon IBC tote made of HDPE, available nearly everywhere for $50-100 and occasionally free. The HDPE can handle 230F continuously, unlike the Linear LDPE totes that can only handle 150F continuously.

I decided against a large water tank as the buffer for my hydronic floor heat/DHW. Water is nearly free, but the ready made tanks or even the materials to build a wooden one cost more than cheap PCM's. My purpose is to pioneer a DIY, easy for others to reproduce, low cost system made from materials that can be sourced anywhere and are cheap and preferably recycled.

A 330 gallon tote can hold enough heat to ride through overnight cold snaps and low PV output if it contains Phase Change Material. Most PCM's and their containers are too expensive. Candle wax (paraffin) is a great PCM, has other prepper benefits and can be bought recycled for $0.40/lb or new for $0.55/lb from firestartersonline.com. Their wax has a melting point of 127F. For slightly more, you can buy waxes in bulk having any melt temp up to 150F from many places to avoid shipping. Goodwill, other thrift shops and some stores throw away their damaged candles. An enterprising DIY'er could get a lot of wax free. Candle manufacturers may have cheap or free scrap wax. Wax used for taper and pillar candles melts at 133-145F, better for DHW than the wax for tealights, votives and container candles which melts at 127-133F. Wax is stable, holds around 200J/g latent heat and isn't any more of a fire risk when encapsulated underwater than a wooden house: set it and forget it.

Sodium Acetate has many uses, including flavoring your salt & vinegar potato chips: it's cheap, easy to make/buy and known as Hot Ice. The stabilized Trihydrate (SAT) form holds over 250J/g latent heat, melts at 136F and is much more dense and thermally conductive than paraffin. It is hard to keep stable, but it appears doable.

Ecorenovators, please post if you have info on keeping SAT stable or good sources for SAT, paraffin or any other worthy PCM's in the Atlanta area! I can make my choice of PCM the last step.

PCM containers: free! The food packaging industry has given us special "heat set" PET plastic bottles, used for hot-fill of food products, juices etc, allowing in-bottle sterilization with no preservatives added. They are good for 185F fill temp and some even go up to 205F, far higher than non-heat set PET's maximum of 150F. Their perimeters are rigid but they have flexible panels to allow for expansion/contraction of contents, so they won't collapse or fatigue as a PCM changes volume during phase change. They have some of the lowest permeability of any plastic, and are impervious to diesel, oils, etc. PET isn't recommended for gasoline, mineral spirits or straight naptha, but you can put nearly anything else in them. Caps are made of PP (polypropylene): no problems there.

I have settled on 64oz juice bottles shaped like Ocean Spray's and the 32oz PowerAde bottles-very common, very strong, very compact stacking and I create my own supply or pick them out of recycle bins. Both have the same 3.5" cross section so it won't take too long to add/release heat from the PCM and are stable to stack. Both will easily fit through the 6" top opening of an IBC tote. They can be stacked in a pattern holding 234gal of PCM in a 330gal tote, while allowing space for circulation around the bottles. This allows me to use only a 20F temp swing from 125F to 145F with plenty of margin on either side of the melt temp to allow for supercooling. This tank will store over 200,000BTU using paraffin and over 300,000BTU using SAT. That's $800 or less for the paraffin, even cheaper for SAT. Using PCM's would also negate the need for any kind of mixing valve to regulate output temp (KISS principle). If using paraffin, rolled or folded heavy gage aluminum foil can be stuck in the bottle, making a thermally conductive path to the PCM in the center.

I will suspend a 30 meter(98ft) corrugated 25mmOD stainless pipe coil having approx. 24sqft surface area in the top few inches of the tote as my water heater for DHW and hydronic heat. Carlsonhx.com's calculator says a 20sqft stainless plate heat exchanger can use 135F input water to heat 2.5gpm of water from 68F to 130F-good enough for my purposes, since my inlet water temp will never be below that. My open loop hydronic system brings incoming water through the floors first, which would pull heat from the house if the water is colder. While I wished for a hotter shower at a hot water supply of 120F, I am happy with my shower and my floors can keep up with cold weather at 125F. Using a PCM that can maintain tank temp at 130F or above gives me some wiggle room and is hot enough to prevent Legionella bacteria.

A plate exchanger with pumped water will be more effective than a corrugated exchanger relying on convection to move fluid around it's exterior, but my coil has 20% more surface area than Carlson's largest HX and I could always add a circulation pump to move water around the tank. The first 4.5 gallons already in the coil will be at tank temp anyway once a hot water draw begins. Insulation will be 4-6" of reclaimed polyiso foamboard, plus 1" of reclaimed ductboard on the sides and top since it has a foil radiant barrier, all held together with UL 181B rated foil ductwork tape.

Search my other posts-other concepts, controls, parts of the system and construction methods are detailed there. This has been and will be built by "an army of two...."

I built a fence this year when it was unseasonably wet. I dug extra deep on a couple post holes, so I know my water table is at minimum 8ft below my slab level even with biblical amounts of rain. I believe it will be 20ft below or more, giving plenty of soil under and around the house to hold heat with. Time to get back to it!

[jeff5may]

The sodium acetate looks like it would be the most suitable material for your temperature range. It is a fairly common salt by chemical supply standards. Not highly expensive in bulk, nontechnical grades.

Food grade, bulk anhydrous:
Sodium Acetate

Runway ice melt:
Sodium Acetate MSDS | MeltSnow.com

The lab or reagent grade is much more expensive, and actually will work worse for your application. The ultra-pure stuff doesn't have anything in it to help seed the crystallization when the temperature drops. That's how those little "hot hands" bags stay liquid until you pop the little disc inside of them. The phase change occurs on demand due to the mechanical shock induced. A little bit of impurity in the salt will help confine the phase change within your target temperature range. I am sure this has been researched thoroughly by chemists, and various custom formulations could be found with datasheets and patents and such to support the respective products. As always, the more specific the application, the higher the product price rises. I don't know if the more inexpensive premixed solutions available on ebay or amazon would have trace chemicals in them to help stabilize the phase change temperature range or not.

You can make small, crude batches of it by mixing white vinegar and baking soda. This chemical reaction yields weak sodium acetate and carbonic acid if there is excess vinegar. Adding extra baking soda yields nothing, which is undesirable. When boiled to increase the concentration, the extra carbonic acid breaks down into co2 and leaves the solution. If using grocery store grade chemicals, the acetate salt must be crystallized, ground, and rinsed with rubbing alcohol to remove the contaminants in the vinegar to refine the salt. This still leaves trace amounts of who knows what, depending on filtering and rinsing methods, but there seems to be lots of youtube videos, instructables, and blogs from home chemists trying their luck to watch.

Crystallization of homemade sodium acetate - All

Please fill us in on anything you find out about this application. I saw lots of building products being marketed, but most were formulated so the phase change occurs between normal room temperature and body temperature in range.

[Mobile Master Tech]

Snowmelt! Thanks for the tip, Jeff! Anything that is cheap enough to throw on the ground at the scale airports need can't be too expensive to get a half ton of. I will check your meltsnow source, as they deliver also.

Aviation story: A CEO and his pilot are flying to a short, icy runway with no good alternate airports in a rented jet without the advanced safety features their normal corporate jet has. Both realize the dicey situation:

CEO: "Captain, does this plane have thrust reversers?"
Pilot: "No, sir."
"Captain, does this plane have antilock brakes?"
"No, sir."
Pause......"Captain, does this plane have any more Scotch?"


Impurities, including intentional ones, seem to be the way to get SAT to not supercool. Adding a few percent extra water and gelling with superabsorbent polymer (SAP), like what is used in diapers, seems to be the way to control phase separation. Otherwise, you get layers of crystals at the bottom and water at the top, stopping SAT's usefulness.

If I use SAT, at least it would be easy to remove the bottles of it from my tank every couple years to heat/shake up/reenergize the mix, since SAT is heavier than water so no mechanical restraints will be needed in the tank. I would like to hear if anyone has practical experience with SAT as a PCM so I can use whatever methods make it least troubleprone.

Mechanical mixing seems to completely eliminate any problems with SAT, but then complexity goes up.

[AC_Hacker]

Originally Posted by jeff5may

The sodium acetate looks like it would be the most suitable material for your temperature range. It is a fairly common salt by chemical supply standards. Not highly expensive in bulk, nontechnical grades.

Do you have any actual experience with this stuff?

I followed Glauber's Salt and also Calcium Chloride salt claims... I bought the components, mixed them according to general lore.

In each case I was not able to approximate the claimed result.

So, I'm interested to know if you have actually tested this stuff that you are recommending??

-AC

[jeff5may]

I have had some experience with both CaCl solutions and the sodium acetate hand warmer packets. Please note that I am not a salt research scientist, nor any other form of pedigreed professional. Take my comments with a grain of whatever you see fit.

The experience i had with the calcium salt was awesome! I used it in a desiccant waterfall dehumidifier like the LEAF home demonstrated. I cobbled it together using a little feng shui fountain indoors that held maybe 2 gallons total volume. It was plumbed with an overflow like a toilet.

Outdoors, I assembled a solar desalinator out of half of an old sliding glass door (maybe 2 square meters), some spare HDPE pond liner, and some 1" XPS board. The water was drained to waste, and did not kill the flowers it fed with salt poisoning. I fed the indoor fountain with a little solar fountain pump, same thing I run in the 5 gallon waterfarm buckets instead of an air pump. The assembly was not super airtight, and held about 8 gallons of salt water. I filled it with a saturated mixture of pet-safe ice melt and tap water mixed up above the wonky point on the saturation chart. The most active region for this evaporator was in the 120 - 180 degF range, perfect for any functioning solar collector. On a hot day, the brine solution climbed up into the 150's in the collector.

I did this stuff somewhere around this point in this thread:http://ecorenovator.org/forum/33290-post42.html
I wish I had taken pictures of it. I tried it out in my parents' south-facing sunroom for about a week. When it worked, I moved it to grandma's house to dehumidify her dank basement. It kept her phase-change dehumidifier from running down to about 20% rh until the lawnmower man threw a rock into the sliding door while cutting the back lawn. Rather than rebuilding the rig, I pretty much repurposed it into the garbage.

The acetate hand warmer bags I had worked pretty well for a few years, maybe 4 or 5. I had three of them, and none of them popped or leaked. I used them on hunting trips and such. One day, they turned up missing, and I didn't replace them. A friend who worked at a warehouse gave me a big box of hot hands packages that fell off a truck or something. The hot hands packs stay warmer for longer in your pocket, but cannot be recharged. I probably put the acetate bags through 200 cycles or more, plus what other people used them also. They worked as good the last time as when they were new.

[Mobile Master Tech]

Not practical for home purposes, but desiccants can store heat, so can ammonia, and caustic soda. Here is an interesting link on "soda locomotives":

Soda Locomotives.