Define... (ME)

Kevin_in_Denver_2

Ron has roughly 100ft2 of Thermomax e-tubes. It's just two people in the house, so about half the day's solar collection goes to an 80 gallon solar DHW tank. Once that tank is up to 170F, then the rest of the solar goes into the large tank. So in essence, 50ft2 of collector has stored the 7.5mmbtu in 1/2 year. He plans on being up to 140-160F by the end of next summer. (sheesh)

Please note that Ron's big tank wasn't intended to support a heat pump, nor was it designed as conventional seasonal storage. It's just his way of eliminating the fossil fuel boiler and the associated installation labor.

[Deleted User]

\"alternative\" energy...

Correct me if I'm mistaken, but hasn't Solar, Wind and Hydro been on the face of the Earth for much longer than OIL???

The technology to convert solar into thermal energy has been in use for HUNDREDS of years, that's right HUNDREDS.

Patents dating back to the early 1800's for solar collectors, batch heaters, application theries and so on.

The BIGGEST hurdle with these energy sources is their seasonal and daily availability, or lack therof.

When you need it the most, you get it the least, and when you need it the least, you get it the MOST.

The need to STORE this energy to last for a full heating season is the BIG problem. Storage not only consumes a LARGE amount of space, but it also CO$T$ a LOT of Do Re ME.

So, when are we going to start thinking outside of the usual box, and start coming up with seasonal solar thermal energy storage systems. One problem has typically been that the amount of usable energy has to be at a temperature that is compatible with the technology presently at hand.

During the first solar gold rush in the 70's (1970's for you young whipper snappers), the methodology tyopically used to transfer thermal energy from the stored fluid were fan coil units. However, these too had their serious limitations as it pertains to approach temperatures. You couldn't typically operate them with fluid temps below 120 degrees F.

Along came (back) radiant floors, wehich were more compatible than the FCU's as it pertains to using low water temperatures, and the amount of useable energy from the solar storage tank was greatly increased. Drawing the water down to as low as 80 degrees was and still is an acceptable practice with the right heat emmitter, and its NOT staple up...

We have the technology at hand to create some of the MOST efficient heating systems known to man kind. We have super efficient evacuated tube solar collectors, highly efficient refrigerant based heat pumps, and WarmBoard heat emmiters. The only thing were short is reasonably cost effective non invasive STORAGE.

Why not, over dig the basement foundation (if possible) and bury a WHOLE bunch of PEX, or other readily available inexpensive tubing in this pit, fill the pit with a slurry of clay (or recycled ash from teh coal burning power plants) to insure maximum density and conductivity, throw an insulation cap between this pit and the conditioned space, and use the heat pump to transfer heat from the collectors into the pit, and viceaversa. We'd be using the best long term equipment availble.

In lieu of an over dug basement, shallow wells could serve the same storage purpose.

What thinks ye Wallies, am I thinking too far outside the box? Is this just turkey talk, or is it something that a grant should be applied for and a demonstration project undertaken...

Beam Me Up Scotty, this place is sucking oil out of the ground faster than the dinosaurs can replace it...

ME

Dave Stroman

Sounds like a better idea than the old welded plastic tanks we used to use, most of which have failed.

Dave in Denver

Constantin

Depends on where you live, no?

Some areas can easily use this setup because they get enough sun to stay warm with a moderate thermal battery. Other areas would need a huge thermal mass to do the same because the insolation is much more variable between and even within the seasons. Siting, architecture, and construction materials can achieve some of the same goals... ensuring that the home has passive solar gain in the winter, a slab floor to absorb it, and the thermal mass to flywheel through the night.

In college we once did a thermal excercise for cooling a regular house in the summer with ice harvested in the winter... we needed a lot of ice.

However, your area of the world with its 300 days of sunshine a year would probably work great with this kind of a system because the thermal battery would not need to be huge. But I would start with the architectual features of creating a passively heated house and then supplement with an active system to KISS. There is a house in VT that I read about which does not need winter heating... it can stay above freezing all winter long just on passive solar gain (when, and if it occurs, which can be rare!).

Wayco Wayne_2

How much tubing would

you need? How would that cost compare to bulding insulated concrete tanks under the basement? What about using a horizontal ground source heat pump loop to store heat in the ground? At the solar Decathalon Rhode Island house used phase shifting material to store energy. How cost effective is that? Interesting stuff. WW

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ScottMP

Dan

Tells the story of the guys out by you who did this and did'nt turn on the heat untill January. I knwo it could be done.

Your right Mark, what we call alternative is really at all.

My new addition will have solar.

Scott

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Plumdog_2

Been thinking along those lines as well

Did the install work for a guy in the 70's where an indoor swimming pool (large) was heated by collectors, then liquid/air Friedrich heat pumps siamesed together took care of heating the house (and AC as well). Huge cost and complexity the obvious drawbacks. Remember the Rock Box? I haven't seen one of those in good long while (that hasn't been abandoned). But your right; there should be a technique for large storage capability that won't kill the budget.

PJO_5

How about...

Using one or two large insulated tanks instead? A couple of 500 gallon ones would give you LOTS of stored BTU's...maybe those "lawn subs" like my neighbors have for propane. No digging, but you do lose some space :-)

Increasing this amount of water 50F takes about 400kbtu or so? Or is my math goofy...

Using that combined with passive solar would definitely work on a semi-daily basis here in SE Pa, which is about 75% of Colorado's sun I think...all other things considered.

Here's another thought/question;

Say I have a couple of evacuated tube collectors. If they can heat water to about 150F on a good day, and I run that through one heat exchanger until I satisfy a 50 gallon tank (for example) for domestic, then I "switch" on another HX after to heat a very large (dump load) tank for the very sunny days...there's my space heat. Would this work? I'm sure it is getting done now by lots of people...and you have the domestic as the "primary" and use a back-up for your space heat.

This is kind of an off-shoot of what ME is saying...I think...it's a slow day here at work :-)

Take Care, PJO

Bob W._3

There is a house near town here that has a huge rock box, more like a sub-basement that was filled with stone. I think it is still in use. Friends of mine built it in the early 70's. Rocks are cheap around here:)

Maine Doug_19

My house in

FL had a heat pump that was hooked to my pool. The pool had 8 large solar collectors on the roof. In the summer, the panels radiated the heat from the AC by running the pool water thru them at night. In the winter, the solar panels provided heat to the pool which the heat pump picked up for the house. We got extra months use of the pool and efficient use of the heat pump. I built this house 21 years ago.

Mike T., Swampeast MO

That sounds sort of similar to a design I saw in Popular Mechanics. Home in VT heated by wood. LOTS of glass. Slab floor. Thick sand/gravel base with a "sandwich" of heavy plastic and aligned, hollow concrete blocks under the slab. Ends of the aligned blocks were channeled to a single inlet and outlet. Inlet fresh air. Outlet "constant temp" fresh air for the home. Small fan driving. Supposedly reduced heating greatly and eliminated any cooling load with very little in the way of operating cost and almost nothing to go wrong.

bob_50

Eutectic

Back in the 70's I thought a lot about storage. It seemed to me that some sort of eutectic material would be the best solution. The most readily available material I could find that melted in the right temperature range is chocolate. Thinking inside the box, how bout an insulated concrete box full of M&M's. bob

jerry scharf_3

what if it was water instead

ME,

I was at the green building conference a couple weeks ago. I happened across these people who make a system to build storage tanks for ranwater control. The product is a plastic grid that is 1mx1mx.1m abd stacks together that is close to 95% void. Each frame holds 25G of water, they squeeze them at the factory custom into stacks up to the size you can ship in a semi. The cool thing is that is is strong enough to build a road on top of (which is what most people do.)

[sever hand waiving follows. I thing it's correct, but I need someone else to see if I've got all the pieces in the right place.]

So if you dig a hole 5' deep, put a foot on insulation and structure around/under it and 1' of top/concrete on top of it, you have a big storage capacity. You would get about 225 gallons per square meter of hole, all safe and strong enough for codes. With an 60x25 house footprint, you wopuld get around 120 square meters times 225 gallons per stack, for a nice 27000 gallons of water.

With a 40F temp rise, that's over 8 million BTUs stored. Let's ignore heat loss and work on the ideal case first. With a well insulated house, you're be looking at say 40MBH design temp load. If you are looking at a design temp difference of 60F, and we assume there are 6000 degree days of heat required (makes numbers easy,) we can come up with 2400 hours of design temp equiv heating. (The hands are waiving furiously, about to depart the wrists.) 2400 * 40MBH is 96 million BTUs used for the year. So you've stored about 1/12th of the annual heat load in the water.

On the plus side, this assumes no passive solar gain for the house. On the minus side, you need to look at the heat loss out the tank during storage.

As a sanity check, it would take 96,000 cuft of gas at perfect efficiency to generate the load. That's 960 therms or something like $1500 for the heating for the year. That makes the calculations seem at least in the right ball park. Also using this number, it comes out that you would save aruond $150 per year from the setup.

Then you need to look at it takes to collect 8MM BTUs of heat. My brain doesn't want to do the gymnastics, but the gut feel is that you are talking about a sizable array to collect that much heat.

So even in the case of a huge storage capacity, you're still talking only a percentage of the total heating requirement, and the payback is hard to imagine.

Seems like A PV driven GSHP setup would do better.

jerry

Kevin_in_Denver_2

This has been done near Denver

Jerry, I've checked the back of your envelope, and you're in the right ballpark.

Last year I did a very similar calculation in another thread.
http://forums.invision.net/Index.cfm?CFApp=2&Message_ID=123850

My main point at the time was that active collectors with a large storage tank may well eliminate the need for a fossil fuel boiler in a well-designed passive solar house in Colorado. (BTW, Ron Larson's 12,000 gallon tank went from 40F to 116F from April 05 to Oct 05.)

Also in that thread, Dale Pickard went on to explain your same conclusion that seasonal storage is impractical.

Mark Eatherton is showing a heat pump in his drawing just as you concluded would be best.

When it runs out of solar heat, the heat pump sucks the balance of what it needs from the ground.

Kevin_in_Denver_2

solar augmented ground coupled heat pump

Mark,

You should show how and where DHW ties in, because that load is what justifies the solar panels.

Once that is in place, I really think this is the system for the immediate future.

A simplification I'd suggest: Just run the Pex in a 4" conventional basement slab. Cover the slab with 2-3" of EPS, then laminate flooring. No insulation under the slab. Now you've got plenty of ground-coupled surface area without any extra digging.

Now it sounds a lot like something we discussed last year:
http://forums.invision.net/Index.cfm?CFApp=2&Message_ID=44229

Also don't worry about eliminating the ability to heat the basement radiantly. A truly well insulated basement is heated by the people and the lighting.

joel_19

big picture

The big picture isn't just how tp generate the heat but why it leaves in the first place . It would probably be cheaper just to build a really tight super insulated house with some mechanical ventilation . My house is 1900sqft and preety well done but it's not even icyneene , just fiberglass. I use maybe 550 gallons of oil . i could probably trim that 100 with solar domestic water and another 75 if it where tighter . Many of the leaky Mcmansions they build now are using 1500-2000 gallons . how bout we just biuld them a little better and use a simple domestic water system ?

Kevin_in_Denver_2

minimize heat loss first

Joel,

You're absolutely right, but the subject could be a little touchy here at the wall.

With a superinsulated house and a little passive solar gain, then the best system for the money isn't a $20,000 ground coupled heat pump system with hydronic radiant floor. It makes more sense to install just a few electric resistance heaters for $2000. Why spend $18,000 to save $400 a year?

(just grabbing rough costs out of the air, YMMV)

Constantin

You're right, of course

What a super-insulated, passively-heated house gives you is the flexibility to heat and cool the place with just about anything and yet not have to spend a lot of money doing it.

These are the kinds of tradeoffs I hope more homeowners building and gutting their dream homes will consider instead of maximizing the bling factors. If the envelope is tight and the insulation thick (can be done relatively inexpensively at that stage), you have a lot more options to build on later.

Naturally, the house-flippers, tract-builders, and speculators are not going to see the value in a Mooney wall or whatnot. They just want to be in and out, minimizing up-front costs at the expense of the homeowners later. Perhaps this segment of the market will get squeezed a bit as the interest rates start to bite, credit will become tighter, etc. but I am not holding my breath.

joel_19

Constantine

don't hold your breath , money and bling rule the realestate universe always has always will. I sell more and more Viessmann not on it's attributes but on the bling factor alone . Many people get the deer in the headlights look when i talk about eff , and lowered emmisions . I tell them it's like the Gageneau dishwasher the Subzero and the Viking stove with 5000$ range hood .

Me : " it's really high tech , it's really cool and your friends don't have one , and look it's got this control screen that lights up!".

H.O.
"That's great when can you start!"

shallow but hey it works.

Kevin_in_Denver_2

New source of complaints

Joel,

Have you had this problem yet? You have this client interested in efficiency, so he builds a very tight house. You install a Viessman system with radiant floors. (Could be $20-$40k right?)

Since he's kind of a tree hugger, he sets his thermostat to 65 degrees. Now he calls to complain because the boiler never comes on and his floors are always cold.

jerry scharf_3

Cool, some real world info

Kevin,

How much collector did it take to get the water tank to raise almost 80F? By my calcs, it stored 7.5MM BTUS, which was right near the number I used. What would it cost to do a collector system double the size?

Since you need the PV/heat pump to take the heat out of the storage tank and after the tank is exhausted anyway, how much advantage does the storage tank give you over a standard GSHP? It would certainly save on the amount of power used during the early part of the season, but that would not be there during the heart of the heating system when you have the lowest PV outputs. Maybe you could partially preheat the ground around the GSHP loops instead.

jerry

[Deleted User]

True you are Con...

I have a tendency to think only about MY location. My idea may not even work in a place like Weezboville. Way too much cold, and not enough sunshine.

In my corner of the world, it would work like a charm.

ME

[Deleted User]

Wayne...

I have asked Timothy D of Wirsbo fame to do some kind of FEA evaluation. My gut feeling is that the grid would look a lot like a snowmelt grid. 5/8" tube, 9" O.C. But that is strictly a gut feeling. I'm sure a lot would depend upon the soil conductivity etc.

We shall see.

ME

[Deleted User]

The problem with rocks...

is that during the summer months, yuou have to keep the rock storage unit warm, or you take the chance of growing some pretty ugly molds in the dark, moist box...

I had a project with rock thermal storage, and the HO ended up abandoning it after the first full year of operation. Seems he was DEATHLY allergic to molds, and he almost died the first summer it was in operation. Finally figured out where it was coming from and eliminated the problem all together,

ME

[Deleted User]

Doug...

This is a classic example of two excellent, commonly overlooked thermal theories. One is night sky re-radiation, and the other is fly wheel thermal mass effect.

I'm only talking about taking advantage of the flywheel effect. Again, you're thinking globally, I'm thinking in my back yard where AC loads are negligble.

Good points though.

ME

[Deleted User]

Patrick...

You're on the right track. In my own home, my solar system will initially heat the DHW tank first, then the house if needed, and then dump into my
DIRT CHEAP" solar storage battery.

The biggest problem is going to be the ability to design around extremely low water temepratures in the range of 115 to 120 degrees F. If you have CFT BBR, this knocks you ouyt of the plan. The GSHP has the functional ability to extract extremely low grade heat and compress it and store it in this range. If the "source" allows a higher temperature, then the C.O.P. of the heat pump is even higher. In fact, you have to make sure that you didn't hit the GSHP with TOO HIGH an entering temperature, or you could blow the heads off the compressor, but the technology for limiting the entering water temperature is an off shelf no brainer.

Dirt cheap storage that works well with low grade heat is the key.

Here's a schemat of my eventual system.

ME

jeff_51

Constantine has hit the problem

the avg homowner stays in his house no more than seven years. (somplaces it is only five) and no one wants to put in the investment for someone else. I have done a number of houses where they spent more on the wallpaper than they did the whole mechanical (yes, it was exspensive paper). Lets face it, fuel is cheap, even at todays prices. I still have the 1954 windows in my house. It has good combination storms, so no payback. I did put in a 90+ furnace 12 years ago, but the ac is a 10 and no payback on that either considering the cooling season here is only three months at best. All the ideas that ME put out on the first thread have been done for years. Problem is, they cause alot of inconvienece. Rock sink overheats in summer and you really can't use the room, they overheat. Solar collectors of course work well someplaces. Groundsource heat pumps are prolly the best at the moment, storage pits as ME suggested just are not going to get by any building inspector in any city and that is were over half the population lives. Passive solar can certainly be built into alot of homes regardless of style. One more issue, who is going to work on these systems? If the contractor who installed it isn't around, you won't get many guys to do it. We have a system that transfers lakewater for heatpumps and has filters etc on it (about a 5 million dollar house) and they can't get a contractor in the cities who will work on it. The company that installed it no longer has a tech who can service it. I could certainly install it off the prints, but servicing it is another matter. It would take days just to begin the understand it. Just not enough money in the job to justify it, it would tie up a guy to long, and than what do you do if that tech moves on? You start all over again. Unless we get some standardized systems, I don't think most guys would touch them

[Deleted User]

Kevin...

I like Dale Pickard. He's my favorite engineering curmudgeon.

I come up with way crazy ideas, and he blows engineering holes through them. Very intelligent individual with substantial engineering back ground.

I read through the thread that you linked to, and it is quite obvious that Dale is looking at it from his typical ridgid mechanical engineering background, where there is but one way to perform the tasks, and that is what he was taught and that is what he teaches. Ridgidly.

He does however, admit that the use of a heat pump could extract heat at a reasonably high output range of 120 degrees, however he incorrectly states that it does so at a poor COP, which I would take exception to. The higher the approach temperature, the higher the COP of the heat pump.

Dale is looking at things through a heat transfer pair of glasses. In order to transfer heat efficienctly through conventional heat exchange methods, you DO need higher approach temperature, as he stated. But, as the name implies, a heat pump can eliminate a lot of the heat exchanges, thereby reducing required storage tank temperatures, and increasing the solar harvest. For the 12K gallon tank in Mr Larsons house, if the "useable heat" were taken from the tank down to say the original 40 degeee F take temperature, or even lower, then that represents 7,290,000 btu's, and that ain't nothing to sneeze at.

Granted, Dale has his way of doing things, and they have been proven to be succesful to a point. It's time for people to start thinking outside of the "typical" engineering box and look to off shelf technologies to enhance what Mother Nature has given us for free.

Leave NO BTU behind...

Marry the heat pump to solar and cheap, low cost low temperature storage. Now THAT'S what I'm talking about.

ME

[Deleted User]

They key to complex systems...

is an owners manual that keeps people from having to reinvent the wheel, or make their own intrepretive drawings everytime it quits working.

It quite simply states the sequence of operation, and what to do if it isn't working.

It' is REQUIRED in a lot of our jurisdicitons. In fact, I've been turned down for final inspections because the literature holder was not found on the mechanical equipment we'd installed. Seems the GC had put it all together in a binder for the new owners, but the inspector wanted to see it right AT the equipment. I agree with the inspector. People lose a LOT of warranty papers. If it is a part of the appliance, there is no need to go hunting for it. And then when the HO moves, and take the literature with them, what's ON the equipment STAYS with the equipment.

My former employer still stuffs all the literature into a tekmar box and hides it in the boiler. Better than nothing I guess.

ME

Kevin_in_Denver_2

Ground couple the tank

Mark,

As Jerry Scharf says just above, you theoretically run out of heat in the big tank when you take it down to 40 degrees. The solution to that is to leave out the tank insulation in spots where it's thermally connected to the earth. The the 55F earth gives up heat to the 40F tank, and you still have heat for the house.

The ground-coupled surface area of this tank is nearly equal to a typical slinky loop, so yeah, I think this would work great. Now the question is if it saves enough money vs. GFA/AC to justify the extra cost.

Weezbo

Mark *~/:)

keep the same picture, yet,make the basement a giant concrete with waterproof tank in the 60 K gallon territory. This was one of my earlier suggestions for holding on to some of those btus. throw a few guppies in the tank call it good

Lloyd Nichols

Biomass fuels are stored solar energy

I have to jump in here and take a different approach to the question. To those of us in the biomass heating business solar energy is efficiently and conveniently stored in firewood, wood pellet fuel, and whole kernal corn. Many other biomass feedstocks are also being researched as fuels, such as, switch grass, corn stover, waste from the cotton ginning, etc. Wood chips are also being used in bigger heating applications like schools. In all cases these fuels are effectively stored solar energy. Many of these fuels can be safely and economically transported, stored and automatically fed into an efficient, low emissions boiler for heating. Biomass isn't very sexy to most people but it is often a good choice when you want to use thermal solar energy. Just my perspective...

Lloyd

Bob W._3

Good points, although I don't know how much of our heating can be done by biomass, when we are also using it for other purposes (like food, auto fuel, etc.). I plan on installing a corn/pellet stove in the garage/barn soon; they are a little hard to find right now:)

Joel_3

no

not really they don't run as much but still run . the water temp is very cold though so the comments i get are that unless it's the dead of winter the floors don't "feel" warm . they are of course they are just only 70-72f

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Kevin_in_Denver_2

Biomass is also CO2 neutral

They use up the same amount of CO2 when being created as they release when burned. I guess particulates are the biggest problem.

[Deleted User]

BioMass is not wihout problems...

Especially in Denver and other cities with inversion problems. Denver sits in a basin and traps MAJOR particulates during prolonged cold weather. Bio mass would not help thi situation unless every converter were equiped with a catalytic after burner.

Denver used to be heated with coal back around the turn of the previous century (1900's) and there are photographs of a BLACK cloud in the Denver basin.

I do agree that it is a renewable resource, but it is not without its own set of problems.

Due to environmental warming, we have whole forests being devestated by the pine beetle. We have PLENTY of wood resources available, but at what environmental costs?

Heres a picture of Denvers skyline on one of its less than pristine days. I can't imagine what it would look like if everyone burned wood...

ME

leo g_13

Different app, same result

Kevin, have one client that repeatedly complained about the house being to warm, yet the floors were cold. Every time I would visit them, EVERY, and I mean EVERY light in the house were on. Sometimes I get there and let myself in, as no one was home. Again, EVERY light in the home was on! Talk about radiant ceilings!!! LOL!!!

Leo G

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jp_2

co2 neutral

true, but its the "rate" of release that can cause problems.

trees uptake may take 20 years but you burn it in your stove and release all that CO2 within a month, along with soot.

ScottMP

Joel

what about a slab sensor to keep the floors warm.

Scott

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Kevin_in_Denver_2

More info on the subject

Here's a paper on Germany's "Deep Probe" solar/geothermal system:
http://www.energyprobe.org/energyprobe/reports/ErHiLiRaSc98.pdf

Love that name