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Old 04-02-16, 04:49 PM   #11
jeff5may
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Wow, what a load of information! Please post some pics or drawings to keep everyone's feet on the ground. There is WAY too much described here to not imagine some kind if "Chitty chitty bang bang" sort of living arrangement. I do see you made no mention of a windmill... Sounds like you have quite a unique setup installed and operating already.


The garage is very interesting to me. The way you described it makes it seem a good fit for annualized heat storage. The mass and insulation are there, as is the conduit for heat transfer. Usage and comfort may be compromised during certain situations, so it depends on how much it is actively being occupied to determine feasibility. The space sounds to have great potential.

I am assuming that your heating needs dominate your utility bills. If so, adding solar pv and/or thermal collectors will definitely offset your gas usage. Since a boiler is already present, a "steam back" solar collection array seems to be a natural winner.

A typical DHW system

Your system obviously differs from the above rig. You have a gas powered boiler and multiple heating zones, in addition to DHW. However, the basic 2-tank steamback system could be a proven starting point to modify for your specific home.


Last edited by jeff5may; 04-03-16 at 10:19 AM.. Reason: grammar, spelling, info
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Old 04-08-16, 06:33 AM   #12
bdgWesternMass
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No windmills (yet, in town location). I do have 300AH of Edison Batteries but they aren't connected yet.

I threw up some pictures that will show my workspace transformation starting in 2002 and ending around 2004.

It has evolved and I will post updated pictures in a bit.

I'm getting ready to start one more big push that I hope can get me very close to netzero including heating. I think I need an Daikin Altherma like system and another 5KW of PV panels.

Initially I designed the thermal storage to allow me to run at higher boiler temperatures for better boiler efficiency and protect it's iron insides. If I use a heat pump as the source I can maintain a much lower water temperature. I think I will start warming up the floor in august will solar thermal keeping the floor temperature around 75 degrees F. Then as it slowly gets colder start boosting the floor temperature to around 95 degrees F. I think maintaining a slow steady low temperature is my goal.

here is a link to the pictures. The top link my not always work

http://projects.cogs.com/

I will continue to message this site based on questions and comments.

Thanks for listening,

Ben

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Old 04-08-16, 08:27 AM   #13
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Since you are considering a Daikin Altherma system, I will use that setup for a comparison here.

The units all run with R-410a refrigerant, which is the current American standard. Unfortunately, it doesn't do so well in high-temperature heating applications, due to its somewhat low critical temperature. Above about 110-120 degrees F, heating performance drops pretty quick the higher your destination temperature is lifted. The units all have been designed to yield a COP of about 4 into a 55 degC destination (heat sink) temperature. If you can live with a 50 - 55 degC heating water temperature, the low-temp line looks pretty attractive.

However, if you need higher heating water temperature (due to radiators, baseboard heaters, etc.), the COP of the Altherma units drops off to below 3 with the additional heating gradient. I didn't look deep into the ratings, but I'm sure those figures are not in frigid outdoor air temps. As outdoor air temps drop close to and below freezing (0 degC), the unit will defrost more often, further cutting into efficiency and raw heat output. Combined with the high-temperature heating gradient, this makes the heat pump not very efficient. Economically, natural gas is a cheaper heat source during frigid weather (more so when high-temp heating).

For the reasons stated above, I would definitely look carefully both at your system design and supplemental heat sources. If you only need high-temp tap water, a modest solar (thermal or PV) source could boost that small percentage of total demand with ease. You could use a low-temp heat pump do supply most of the demand in its efficient operating range. OTOH, if you need more high-temp water to supply space heat, there are trade-offs to be made. There is a big difference in outdoor unit expense between a unit that can provide total capacity on a cold day (with excess capacity the rest of the year) and a unit that (only) provides capacity 90% of the time. The difference in upfront cost could take a decade to pay back in efficiency.
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Old 04-08-16, 08:36 AM   #14
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Have you seen the solar tie-in systems for the altherma?

I can I deal with the low temperature water for the 2 offices.

The house is currently on steam radiators. I think I will install very closely spaced 4" or so on the first floor since I have access from the basement. The second floor of the house will probably get the low water Rental Radiators I used in the second office.

I believe I will be able to then heat all 3 buildings off low temperature water. We rarely get more then 15 days a year when it 5 degrees F or lower a year. I'm ok with not having an efficient system on those days. The other attraction to the Altherma system is that they seem to offer a chiller that works off the hot water loop. To tie this whole project back to the subject title. I want to try and get some sort of refrigerator running off my heat-pump.
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Old 04-08-16, 03:43 PM   #15
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You can do that with pretty much any system. The feature you are referring to is a desuperheater hx. It is plumbed in directly after the compressor in the refrigerant loop, before the reversing valve. It always sees the hottest temperature gas leaving the compressor, regardless of whether the unit is heating or cooling.

The opposite is not so easy. You cannot just tap into the compressor suction line and cool water with that stream of refrigerant. The lion's share of the cooling capacity is realized as the refrigerant is changing phase from a liquid to a gas, immediately after it squirts through the metering device. The suction end of the cooling coil (evaporator) is opposite the metering device end, so by the time the refrigerant reaches the suction end it has expanded. 99% of the heat has been absorbed at low temperature (latent heat transfer), and the remaining heat (sensible transfer) occurs by the gas changing temperature. Even with low counterflow heat exchange, there isn't much left to be had.

Added to this conundrum is the reversible nature of the heat pump. If the unit you choose doesn't change direction between heating and cooling modes, it is easier to directly rig in a chiller circuit. If the thing changes direction, you would need a dedicated chiller circuit plumbed in that short-circuits the reversing valve. Either way, your chiller is going to rob capacity from the cooling circuit one way or another. Whether or not that matters makes a difference as to your options. Also, the chiller circuit would be a slave to some other heating or cooling demand in the house.

As far as Hot potable water and freezerating go, they are usually a much smaller load to satisfy than the space heating and cooling needs. Other ecorenovators have toyed mercilessly with these comparatively tiny loads, and had resounding success. A run-of-the-mill dehumidifier can be modified to simultaneously make plentiful amounts of cold space and hot water, consuming about 250 to 300 watts while running. Maybe more power than a TV running, but definitely less than a desktop PC running. In comparison, most whole-home a/c units draw at least 2000-2500 watts while running.

I hope I didn't confuse you too much in this post. If so, just read through some previous threads. Many have been where you are now in their own struggles, and it takes a good amount of planning to get what you want out of your system. Superior efficiency is all in the figgerin', so to speak.
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Old 04-08-16, 03:51 PM   #16
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Yes, it was those dehumidifier projects that peaked my interest in the site and prompted me to join. I should probably consider a secondary hot water source as an emergency backup.

I will try to start tinkering with one this summer.
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Old 04-08-16, 06:51 PM   #17
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There are a few members tinkering with phase change materials. These serve as thermal batteries in the temperature range you choose. On the hot side, calcium chloride and water mixture is perfect for DHW. On the cold side, there are brine solutions and organic materials available. These materials store 4 to 14 times as much heat as ice melting to water (or release heat during freezing), and can drastically change things for the better. They work the same way as your sand bed floor, only they hold more heat per unit volume, and while charging and discharging they stay just about constant temperature. So for say, the same heat capacity as a 100 gallon water tank, you only need like 8 or 10 gallons of PCM material. Charge the PCM with hot or cold when it is economical/available, let the PCM take up the slack.

Here's an article on a solar walk-in freezer:
http://www.pcmproducts.net/files/Sol...e%20System.pdf

The referring page:
solar thermal heat storage and heat recovery programmes
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Old 04-13-16, 09:44 AM   #18
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I read through the phase change material (PCM) article. I think I'm going to to set-up a precise measurement/logging system over the summer. Then this winter gather the data to calculate the kWh of storage in my sandbed. I also want to experiment with how low a water temperature I can use.

Oddly enough my battery storage is about the same as the the one in the article.

I wish it stated how much PCM was used. I wonder if my larger quantity of sand makes up for the efficiency loss of using a PCM?
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Old 04-14-16, 07:23 AM   #19
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After viewing your link, I am convinced: you have the disease. No doubt about it. I am now thoroughly bewildered. In addition to the genius of Caractacus Potts, you have the work ethic of Willy Wonka as well.

Quotes to support my discovery:

"Caracticus Potts: Mm? Oh. Do you think I'm a lunatic, wasting my time on a lot of silly inventions?
Jemima: But they aren't silly! They're wonderful!
Jeremy: Nobody else can think of them."

"Willy Wonka: [making a mysterious formula] Invention, my dear friends, is 93% perspiration, 6% electricity, 4% evaporation, and 2% butterscotch ripple.
Mrs. Teevee: [as Mr. Wonka drinks the formula] That's 105%!
Sam Beauregarde: Any good?
Willy Wonka: [smacks his lips, then speaks in falsetto] Yes."

Seeing the garage project, it is clear now that you cannot use the sand slab for a medium or high temperature heat store, since the space is at least partially finished living space. Doing so would turn that area into a sauna above a certain slab temperature. Unfortunately, that certain temperature is probably below your minimum heating supply water temperature. However, that zone will be particularly easy to heat with low temperature supply water.

That is some really nice looking work! Please feel free to write us an encyclopedia about this project.
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Old 04-14-16, 08:24 AM   #20
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Thanks for the feedback

The current goals for the sand slab is really to act as a moderator. I want to keep it between 100F-86F degrees during the heating season. So my current quest is for generating water up to 110 degrees during the heating season.

Here is how I'm thinking I will use the sand slab. Charge it during late summer with solar thermal drainback system that could also be used during sunny winter days.
Once the sand slab is charged there will be days it can handle the heating alone and other days will it be charged using some sort of heat-pump.

On the coldest days the sandslab can boost the water temperature with could be a problem with an air source heat-pump.

I have just been doing some calculations to figure out the quantity of btus I can store and looks like I can store 341,100 btus. That I can use for passive heating of the my office or boosting the water temperature of the system or both.
I got the numbers based on these links:
Using Sand to Store Solar Energy | GreenBuildingAdvisor.com
Sand bed storage for solar homes

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