Posted by Dana.
The only seasonal storage system using underground storage in an insulated tank anywhere near your size is a demonstration project in Galway Ireland, with much milder climate than yours and a very tight very well insulated PassiveHouse type building, not a retrofit on a leaky 20th century standard-issue house. See this.

Hi I visited Lars from ScanHomes a few weeks ago, his tank loses more than 50% of its heat through the 2 ft of insulation, the temperature dropped from 150 degrees F in Sept 2010 to 75 degrees F in Jan 2011 so was too cold to draw heat from.

I think that water tanks in the 1000 to 5000 gallon range make lots of sense for time shifting heats loads for solar, wood heat, off-peak electricity, diurnal storage, faster warmup after setback, etc.

Posted By Viking House on 12 Jun 2011 06:57 PM

Posted by Dana.
The only seasonal storage system using underground storage in an insulated tank anywhere near your size is a demonstration project in Galway Ireland, with much milder climate than yours and a very tight very well insulated PassiveHouse type building, not a retrofit on a leaky 20th century standard-issue house. See this.

Hi I visited Lars from ScanHomes a few weeks ago, his tank loses more than 50% of its heat through the 2 ft of insulation, the temperature dropped from 150 degrees F in Sept 2010 to 75 degrees F in Jan 2011 so was too cold to draw heat from.

I'm  not too surprised. It's easy to become overly optimistic in how low the actual heat load is, as well as the perfection of the insulation seal. 

And 150F is a pretty high storage temp, even with 2' of insulation, guaranteed to be lossy.

If this one failed to perform, I can only imagine how miserably cowboy-calculation seat-of-the pants systems might fare...

I'm still curious to watch how Drake Landing performs over the next 5 years.

Do you guys have a problem you are trying to solve, or is this just trash talking? I have built PAHS, AGS, Mass thermal storage, Net-zero, passive and other homes. All worked well because they were engineered with FEA analysis and experience. I have been doing zero energy homes since the 70s. The important thing is figuring out the least expensive way to accomplish a carbon free building per the location. You want to use local sourcing, natural materials, recycling, repurposing, etc. R-100 in a sealed house or 6 foot thick earthen walls and an R-100 roof will typically get you to zero. Note, good windows, doors, HRV, solar orientations etc. are also needed. R-30 foam and 3 feet of earth will also get you there. Mass is cheaper and more comfortable unless you are having hot flashes and want to keep changing the temperature. Earth inside the envelop averages temperature over time. Every foot of earth typically averages the homes temperature over a month of temperatures. A little solar gain in the winter, dihedral averaging warm times etc. I feel like I am rambling. Again what are you trying to do? Brian Earth must be kept dry to be effective because the fluid flow removes the stored heat quickly. Water table, bedrock and other things need to be considered.

I know 11 pages is a lot to wade through, but the gist of it is, the initial poster "dragmit" was running the concept up the flagpole of using the thermal mass of soil to shift solar heat gain to support mid-winter heating loads as a retrofit project. He seemed adamantly opposed to doing even the simple napkin-math as a sanity check, but I tried multiple times to convince him that getting to net zero by upgrading the envelope of the existing house would be a far cheaper and more tractable proposition, requiring even less insulation than the thermal storage envisioned for supporting the much higher seasonal load of the non-improved house (or even a somewhat-improved house) in his upstate-NY climate. The problem he's trying to solve is a retrofit solution for barely-code (or sub-code) insulation houses, not PassiveHouse or NetZero new-construction. He also seems convinced (absence of evidence or even a simple-arithmetic first-cut model of the problem notwithstanding) that a seasonal storage solution using the thermal mass of soil is destined to work.

I've yet to see reasonable path to seasonal thermal storage on a single-home basis, but the district heating scheme at Drake Landing may have merit (TBD). Whether it is more economic in the end than doing that way rather than doing the same number of homes in a more straigthtforward PassiveHouse or NetZero approach remains to be seen. Drakes Landing went with R-2000 standard on the building envelope to better bound those costs, but the cost of the active solar and thermal storage field is also quite substantial.

The only reasonable way to make these systems work is to make the envelope use 80 to 90% less energy first. Thermal mass in the form of rock or earthen fill, lots of cellulose, ashrea 50 of less than .8, radiant roof, thermal barrier, better windows and doors and placement, natural circulation, moderated air intake and exchange and an HRV system can be done for a small investment comparatively. A good house and suddenly seasonal heating systems can easily be accomplished to get to a self-heated home.

Brian

The only reasonable way to make these systems work is to make the envelope use 80 to 90% less energy first. Thermal mass in the form of rock or earthen fill, lots of cellulose, ashrea 50 of less than .8, radiant roof, thermal barrier, better windows and doors and placement, natural circulation, moderated air intake and exchange and an HRV system can be done for a small investment comparatively. A good house and suddenly seasonal heating systems can easily be accomplished to get to a self-heated home.

Brian


Brian

The only reasonable way to make these systems work is to make the envelope use 80 to 90% less energy first. Thermal mass in the form of rock or earthen fill, lots of cellulose, ashrea 50 of less than .8, radiant roof, thermal barrier, better windows and doors and placement, natural circulation, moderated air intake and exchange and an HRV system can be done for a small investment comparatively. A good house and suddenly seasonal heating systems can easily be accomplished to get to a self-heated home.

Brian


Brian

The only reasonable way to make these systems work is to make the envelope use 80 to 90% less energy first. Thermal mass in the form of rock or earthen fill, lots of cellulose, ashrea 50 of less than .8, radiant roof, thermal barrier, better windows and doors and placement, natural circulation, moderated air intake and exchange and an HRV system can be done for a small investment comparatively. A good house and suddenly seasonal heating systems can easily be accomplished to get to a self-heated home.

Brian