No April Fools here...

Mark Eatherton

The biggest problem with solar thermal is when you need it the most, you get it the least. And when you need it the least, you get it the most, and if you can't use it, it will cause "maintenance issues"...



Storage is THE largest stumbling block in using this and MANY other types/sizes of alternative energy.



I've been following this Drake Landing project for many years now, and it looks like THEY may have a winner.



Check it out.



<a href="http://www.dlsc.ca/borehole.htm">http://www.dlsc.ca/borehole.htm</a>



While you're at the url, look around. Interesting concept for sure.



I think it could be significantly enhanced if they would do away with the plastic and replace it with copper. I have a concentric design using 2" copper and 3/4" drop pipe that would make the loop field shallower, more compact and probably even higher operating temperatures. A person could even set it up so that the heat were definitely dropped there. Heat rises, so it will naturally stratify, if that is your goal. Drakes concept appears to be keeping the core hot, while allowing the exterior of the thermal cell to remain somewhat lower. I think it tops out in mid August or something like that. I know when they first started it up, it went up to 180 degrees F in no time flat because the DHW and SH loads were relatively low due to empty units.



A word of caution. The aquifer in this scenario is relatively static. In certain areas of the US, the ground water is continually moving, down hill, seeking the lowest spot (ocean), and any major thermal energy that is in direct contact with the thermal energy storage cell WILL disappear.



In other words, you might have to consider going horizontally, say at a 22-1/2 degree angle with a central pit for loop distribution. Or into an abandoned mine shaft, cemented in place.



Japan stores energy from parking lots in VBH's and harvests the energy during the winter for snowmelt. Uses something like 85 watts per hour for pumping capacity...



Ya just have to think outside the box. That's all :-)



ME

jp_2

why not just

build super insulated, passive solar buildings...............



I'd wager to say storage is the problem with ALL alternative energies, being solar/wind.



I leave out biofuels.



seems the bore systems have a chance of ground contamination?

Mark Eatherton

If it were THAT easy....

EVERYONE would already be doing it, no?



I've personally never lived in a primary passive solar house, but have had an occasion to be in one near the middle of December, and it was SO HOT inside, that the owner was actually running an air conditioner to maintain reasonable comfort conditions, and it sounded as though that was a regular occurrence.



I'm not convinced that living in a solar heat cave is the ultimate solution...



It's a step in the right direction, but I don't think most people are ready for that much life style change... Not yet any way...



ME

Sal Santamaura

And for a great case study of why active solar...

...with windows facing North is better, jp should read about Larry Weingarten's home:



http://www.waterheaterrescue.com/pages/whh/pages/hummingbird-home.html

zacmobile

ISHT

Not an anagram, these guys have taken the Drake landing concept and made a proven commercial product out of it, even seasonally stored cooling & snowmelt! neat stuff for sure.



http://www.icax.co.uk/interseasonal_heat_transfer.html

Kevin_in_Denver_2

Active Vs. Passive

Sal,



This debate has been settled for a long, long time.



You are absolutely correct, however, that a well-designed active solar house CAN be much better to live in and cheaper to heat and cool than a poorly designed passive solar house.



Not much chance of it being cheaper to build, however, since an active solar system will always cost more than a few extra windows.

jp_2

yah, I guess i'm pretty foolish

hey Sal, I consider my place to be passive solar, though not by design, I just like windows.



guess the other day when it was 35F outside and 70F inside that was all bunk.  at midnight when is was 16F outside it was still too warm inside to start a fire....



you are right ME, simple solutions are often bad ideas........  we could talk for months about simple solutions ignored for more complex costly ones. 



thats one of my favorite comment, "yah I saw one of those once, it didn't work, therefore none of those systems work"

seekertom

temp stability without solar?

I once saw an article about using the earth at a given depth to maintain a stable temperature in a home. The thought was that at some given depth, the earth stays a constant temp, all year long. Laying lots of pipe at that depth, then circulating the fluids into the home resulted in something like 70-ish degrees all year long. The depth was surprisingly shallow, for what I might have guessed. Anyone have experience with this concept?



On another note, re: solar storage... In another thread we beat up on my solar system repair project, which included replacing my old 80 gal dhwh with a new 50 gal one. My solar is not yet functional, and I started to stink, so I (shudder) plugged the hwh in for an hour so I could shower. Temp at the tpr valve reached 118 deg f, and when I was ready for my shower, the pipe to the house loop measured 108 degrees f, so I unplugged the hwh from ac. I don't take quick showers. The water felt just right. Next am, 9:30, the tank still measured 112 degrees at the tpr valve. During the shower, my house-loop circ pump was running, but I turned it off when I unplugged the hwh.



Point is, this new tank showed me that efficient storage of solar-heated water over-night is a reality. Yes, a consideration is, how much did I use out of the tank. I can't say, nor can I say how long the hot water would last with three or four of us in the house.



Just a thought to share.



t

jp_2

ah come on ME, where's the boiler box?

where's the thinking out of the box here?



you come to a house thats too warm from passive FREE  heat;   no pumps,valves,ODR's, antifreezes, boilers and you don't see a great start for a heating system?   Isn't over heating an easier problem than under heating efficiency wise?



I agree passive heating isn't a perfect heating system, but how can you really get simpler, more cost effective system?  they don't have to be caves with only southern windows, unless you fear to come out of the box



I understand the heat wells, but is it really practical for the small guy?



wouldn't a spring snow melt kind of wash away the heat?

Kevin_in_Denver_2

Drake Landing is a success without a future

http://www.dlsc.ca/news/2010/02_06_10.htm



Even though it's performing better even than expected, district heating is a concept that has long since come and gone. The average North American single family homeowner wants all of his appliances under his control.



No one wants the neighborhood HOA dictating expenditures for their heating system. This system is way too mechanically complicated to have low maintenance expenses.

Mark Eatherton

JP...

I've done thunk outside of the box hydronically speaking.



For example, first off, there HAS to be a middle range point where the home is NOT as mass intensive as they have been historically. With passive solar gain, your options are fairly limited. You can keep it out of the envelope (i.e. overhang control, and or dynamic glass, see Raven Brick http://www.ravenbrick.com/ or Sage http://sage-ec.com/pages/faqs.html



My ideal passive energy home is going to require the consumption of SOME energy, but the human comfort factor will be high, and the energy consumption quite low.



My floors would be done with Warm Board, covered with a thin, but highly conductive, dark material. The hydronic's would be powered with small DC powered (think 5 watts or less) mini circulators from WILO, and a PLC control logic from ENV that would have the ability to see "free" energy falling on a given surface, and would have the ability to functionally transfer the falling energy on the South side of the home, and allow it to be transferred to other areas (North) of the home that need the energy. Once the rooms are satisfied, then any excess solar energy falling on any given surface would be directed to a seasonal energy storage system (think vertical bore hole with enhanced copper heat exchange system and direct or GSHP extraction depending upon temperature of availability). Hence, energy efficiency WITH good human comfort. You don't have to be uncomfortable with direct gain passive solar.



Back on the glass front, there are numerous working patents for see through solar collectors, that would allow the majority of the incident solar radiation falling on the South side to be converted to electrical energy. This energy can then be transferred via wire to the North facing windows, and "banked" for use later in the evening.



Is it the most simplest form of alternative energy utilization? No, a box with no north facing windows would be the ultimate simplest form, but also the most uncomfortable to have to live in.



So, one CAN have the ultimate in alternative energy utilization, but through control, the human comfort factors can be maintained, along with minimal energy consumption.



Insofar as VBH thermal energy storage, I believe it IS within the reach of Joe and Jane Sixpack. I have a small portable well drilling rig, powered by a Hole Hawg drill, that drills a nice clean 3" hole (Hydro borer), that allows a nice 2" copper heat exchanger to be tightly grouted into the hole, giving good conductive contact between the fluids and the Earth. Obviously, this technology is NOT for all locations. If you have a shallow ground water aquifer, the wicking effect will have a tendency to diffuse what energy you have collected. And I am not alone in my thinking. Numerous German hydronic manufacturers are already marketing a hybrid solar thermal system with Earth Seasonal Energy Storage systems, and obviously, your milage may vary...



Is THAT far enough outside of the box for you? :-)



ME

jp_2

Not Bad ME......

will you use a heat pump to move the lower temp water around?



I found an old file on my laptop from the wall,  60 ways to eliminate solar gain, I thought that was funny, sounded like trying to eliminate infiltration......or something bad.



you would need cool water to remove heat from the room getting too much sun. wheres this cool water going to come from?

Mark Eatherton

Only IF cooling is actually required...

In most cases, just swapping the fluid from the North side to the South side, and vice a versa. The biggest problem with most of the current heat pumps is that they are either fully on, or completely off. No points in between. We have the technology, it;s just a matter of application.



In Germany, they will bury a whole bunch of tubing in the foundation, and use that to produce cooling at the entry points to the building, so we know it CAN be done. It comes down to heat transfer efficiency, which WarmBoard rules, as we all know.



ME

jp_2

PV windows

not a bad idea.   but that would be pretty expensive way of doing it?



your highest output would only happen during the narrow winter months with sun angle,  I can see this working in an office building, but with a residence, you'd be way ahead putting standard PV 'son the roof.  thus window PV's would be real inefficient, but a great talking piece.



how would you bank this ? batteries?

Mark Eatherton

No alternative energy is inexpensive...

The "banking" of thermal energy would be done by converting the electricity into thermal energy and pouring it in through the same window from which it would normally seep through. Essentially raising the MRT of the North facing rooms.



One could use chemical energy storage (batteries) but that would add significantly to the installed cost.



I have designs on a radiant window that would store off peak electricity in batteries, then use it to maintain the radiant windows in the thermally opaque condition to help get the space through peak demand with minimal energy requirements. Then, once non peak conditions return, the windows wold be heated directly off the grid, and the batteries recharged again. I'm thinking high rise applications for the most part.



There are electrical off peak heating systems out there, one that pops in my mind if STEFES.



ME

jp_2

maybe not clear

ME,



i was talking about using a window as a PV source as being highly inefficient or you could say very expensive.   my reason is that the PV/window, i assume that is vertical, will get little peak power seasonal.   thus a PV panel on the roof would get much more energy output yearly.   i find a vertical panel is good for about 3 months a year.

you would get no power in the summer.



with the high cost of PV's you want to harvest as much as possible, generally that s not putting them in a vertical position, and then forget it if you have overhangs.



i looked at the raven site, little disappointed that i could not clearly read their graphs.  I will look again, but first impression was not that impressive, sciences wise.   when I see free heat/cooling 100% efficient, i start wondering...........



from my experience, the best way to solve solar over heating is using air flow.  your north side would most likely require more heat than the south floor could deliver.  the sun seems to spread heat pretty evenly in a room, so if you drop the floor temp 5F, it probably won't get noticed in time.  



interesting ideas none the less.



in my case pv/batteries were much cheaper than 1 mile of power company line.

you do live life far differently than your city counter parts.

Paul Rohrs_14

ME- I like the concept

but the pragmatist in me wants to believe that the whole system's heat emitters must be sized to the storage capacity at design conditions.  

What exiting water temp are they designing around in the middle of winter?  My other concern would be max temp and pressures of the "Tubing" in questions.  We all know that most pex is 80psi @ 180F which seems substantial, but is it robust enough to stand the test of time, even when grouted? 

Makes me as nervous as a long-tailed cat in a room full of rocking chairs.

Seems like this is a dedicated Geo thermal storage with a solar feeding it as a dump zone?

Thoughts?

Mark Eatherton

Pragmatic Skepticism

Paul, I honestly do not know the answers to your questions. But in my minds eye, it would make sense to have an input system, separate from the output system.



If I were to design this system, I'd have individual DHW storage tanks in each dwelling unit, supplied direct from the individual owners array. Once the DHW storage tanks are charge, any excess energy would be diverted through a district collection system and delivered to the short term storage tank. Any residual energy would then be sent to the VBT seasonal storage system.



On a call for heat, there would be a separate loop that would distribute the solar heated water through a district heating system, that would deliver the energy to a WSHP that would then deliver the energy to the dwelling loads. During cooling calls, the heat of rejection would be sent back through the district loop to the VBH storage system and sent to the outer (cooler) loops for rejection.



By using the WSHP technology, the distribution loop temperatures can be maintained at a relatively low temperature of operation, thereby minimizing the piping losses between source and load.



As I have previously stated, the use of VBT for storage is extremely dependent upon a static aquifer. If you have a dynamic (moving) aquifer, it will not work for high temperature storage, but if in fact it is moving, it will produce lots of low grade heat, ideal for collection and distribution through the district heating systems network of pipes.



As an alternative to VBT, a person could build a large pit storage system, with flat slinky PE coils, for higher grade energy storage, if available. This could make for DIRT cheap energy storage.



We HAVE the smarts and technology available to us, and it has been proven to be a viable technology, in most cases. We simply need to do more R&D to refine the technology and get it into distribution.



BTW, what an excellent way of avoiding collector stagnation issues, eh...



ME

furthur

heat dumping for homeowners?

An idea I had very recently for dumping excess solar heat was to dump it near below grade walls, preferably under foam insulation.  You could recover it, if you wanted to, but otherwise, it just lowers heat lost.  The caveats for other ground storage still apply, but the storage temps are very low, maximizing BTU's even on low output days.



My original thought was for solar snowmelt, where water temps can be very low and still usable.  Once those areas are satisfied, and during "off season", might as well use those free btu's.  After DHW preheat, and any other low temp scavenging, this seems like another efficient way to uselow temp  "leftovers".