podcast 459 - Annualized Thermal Inertia Test

Would a rocket mass heater have any downside in a Wofati? Is it for purity of the experiment that you are going without a heat source entirely or is the design somehow incompatible with a RMH?

Ask me that again in about three years.

Some partial fractional solutions / ideas :

I'm working through a similar design problem.   I'm trying to estimate how much external heat (or cold) a space will require.

I accidentally figured this out by running a propane heater in the space.

If a 4k btu / hour heater heats the place, it's losing less than 4k btu /hour at the current temperature difference.


The heat loss equilibrium would be  heat_added =  heat_lost_to_environment + heat_put_into_the_mass + heat_added_to_the_wafati_envilope.


If the wafati human envelope is at a stable temperature, and the mass is at a stable temperature then the result is the amount of heat lost to the environment at that temperature difference.  ( it gets complicated because there is air and ground temperatures to deal with, ignore it for a bit ).


By finding several equilibrium points with different amounts of added heat, the system should be characterizeable.   If there is measurement of how many BTU is required to change between equilibrium points in mass temperature, that should be usable to help inform how many BTU are stored ( and thus available for use later ).


Also,  If I had my maths with me ( I forgot them long ago apparently ),   The shapes of the curves in the temperature graphs would help : e.g.  https://permies.com/t/180/120233/permaculture-projects/Jen-Boot-Camp-Allerton-Abbey  https://permies.com/t/120233/a/96786/F5DF010F-A925-4E0B-BEA5-664886DA0EA7.png ,   The Un heated temperature graphs show a logarithmic decrease.   They should be asymptomatic to the temperature of whatever is driving the system ( presumably the mass and energy losses to the cold cold outside ).  


The front wall clearly shows this sort of shape : https://permies.com/t/120233/a/96787/0D2EEB72-EC99-4555-9D23-C31D4FEDE5E7.png   Though it's probably responding to the outside temperature more than than the thermal mass charging.


Is there a temperature sensor in the floor?

Is there a reticence to using temporary portable propane or kerosene heaters?   If the voltswagon isn't doing anything  3kw of solar turns into 10k btu of heat with an extension cord and a resistance heater.  ( just don't run it on the batteries cuz' it's abusive ).

We should be able to math this out some.... humm..

I haven't finished reading your post and I need to comment on the propane heater.   I have two big concerns:

    - it uses up the oxygen in the space (and i am also concerned about the invisible exhausts)

    - it puts a huge amount of water into the air

Is there a temperature sensor in the floor?

Nope.

I feel like we did good to scramble to get the tracking thermometers that we do have in operation.  

Is there a reticence to using temporary portable propane or kerosene heaters?

There it is!  Yes!  See my notes above.  

Mostly, my feelings are that I would like to have the mass fully and properly charged.   And then do the REAL ATI test next winter.  At the same time, I very much like seeing the abbey get better prepared for next year with window quilts and the like.  

In the meantime, if we are going to explore adding a heat source, I far prefer something wood based rather than something petroleum based.  But I do think it is quite excellent that the mass is not  charged, but just people living in there and doing some simple cooking is doing pretty good.   I would like to see something much warmer, but as we add heat, the mass will pull it out of the space - as it is designed to do.  

I guess what I am saying is that I think we can simply dodge a heat source.

If the voltswagon isn't doing anything  3kw of solar turns into 10k btu of heat with an extension cord and a resistance heater.

The voltswagon ...  I am kinda wondering if the thing we need to consider is something a bit different.   The voltswagon has issues.  I wonder if the plan could be to take out the six year old lead acid batteries (which do poorly in the col) and the inverter that takes a lot of power even when nobody is using power ...   and replace all of that with a tesla powerwall.  We could even pop it down to basecamp and charge it up, bring it back and we could run something with a bit more power for a few days - if needed.

paul wheaton wrote:I haven't finished reading your post and I need to comment on the propane heater.   I have two big concerns:

    - it uses up the oxygen in the space (and i am also concerned about the invisible exhausts)

    - it puts a huge amount of water into the air

No worries.   The oxygen issue (e.g. killing things with lack of it ) can be solve by the Mr. Heater  Big Buddy  it's got an low oxygen shutoff.  Maybe not something to _only_ trust, but it's something.


The water might be the solution to get the mass more charged.

A pool heater, that circulates warm water around coiled tube inside the wafati.    ... They seem to be costing in the kilo dollars. well fooie on that.    a home brew solution might work well enough temporarily enough to charge up the mass.

...

The volts wagon.   It might be possible to hook up a heater (or some lights) without the inverter or the batteries.   (depending on the details of everything)  A dump/diversion controler => 3k worth of lights or resistance ; done. ( :) )

....

The power wall will be something like $10k ( and they _really_ might not like it being used as in a mobile installation ), for 13.5 kwh .   13.5 turns into about 46k btu, and each round trip is going to take 3-4 hours.  I'd guess the cook top is doing more.

....

heat water with the cook top?    That might help the heat transfer better... maybe...

....

5kw of propane generator (outside) and a bunch of halogen lights (inside) ?    It's temporarily icky, but might be worth it for science. ( and the cheapest/ simplest/ fastest solution ) .   And I can see not being happy with that one; I'm not.

...

Tank hot water?  Is there a large hot water heater on the lab?   a 55 gallon barrel of water at 210 degrees has about 50k BTU usable in it.     4 of them might be a good start, though driving that stuff around is going to be dangerous and getting it all moved around is going to be burn inducing.

...

That being said, it's a good problem to solve.    having to wait 3 years to _realy_ get a place happy is a larger ask for the general human populations.

...

Build the sauna.  Put it down hill of the floor of the abby.   Add some water heating coils to the sauna heater.   Thermosyphon up to tank(s) in the abby.    Daily sauna activity.  ?    

...

As a first data point it's probably a good idea to start recording wood weight.  It'll put an upper bound on BTU required to increase the air temperature in the space.   Adding more BTU than that number is just going to be wasted.  (Should! hA!  I almost should'd Paul, I need some sleep I think).  A week or two of watching the temperature loggers and recording wood weights, we can go back and get the temperature rises per weight of wood.    Two burns a day, one when it's getting warmer and one when it's getting colder ( and dark) would be helpful.  Is there an exhaust gas temperature for the typical burn on the cook top?  ( getting an approximate idea of cook top thermal efficiency might be helpful too ).  

...

I'll ponder it more after some sleep.

Good luck with it!

tesla power wall - I got the impression that they are about $7000.  And they supposedly will do fine down to 4 degrees.   It seems that the the thing to do, for a portable solution, is to have them in a super, tiny insulated room with an incandescent light bulb that comes on when temps are below 20.

Out of all of the solutions that you listed, the one that seems the quickest and I am the most comfortable with would be the propane generator and a conventional portable electric heater.

BUT!

I think the best thing this year is a series of simple, indicative tests.  

Even if we ran the generator for a week, holding the interior temp at 85 degrees F for a week and then observed what happened in the following weeks - all of that would still be nothing more than indicative.  

The real test is a year from now.   Hence the challenge with "annualized" - it takes a year to do proper tests.

If we had more people in the bootcamp the last few years, we might be two years ahead on this testing.   Which is why I have placed so much emphasis on the bootcamp and the BRK for boots.

paul wheaton wrote:tesla power wall - I got the impression that they are about $7000.  And they supposedly will do fine down to 4 degrees.   It seems that the the thing to do, for a portable solution, is to have them in a super, tiny insulated room with an incandescent light bulb that comes on when temps are below 20.

Out of all of the solutions that you listed, the one that seems the quickest and I am the most comfortable with would be the propane generator and a conventional portable electric heater.

BUT!

I think the best thing this year is a series of simple, indicative tests.  

Even if we ran the generator for a week, holding the interior temp at 85 degrees F for a week and then observed what happened in the following weeks - all of that would still be nothing more than indicative.  

The real test is a year from now.   Hence the challenge with "annualized" - it takes a year to do proper tests.

If we had more people in the bootcamp the last few years, we might be two years ahead on this testing.   Which is why I have placed so much emphasis on the bootcamp and the BRK for boots.

Totally fair and right.  

My understanding with the power walls,  $7-8k cost, + installation ~= 10k.

( I just found these) Slightly better than strait propane would be something like a cozy cabin propane heater, they are sailboat heaters that send flue gasses out the chimney.   Neat!

Also, they make the same thing but for diesel.   Diesel heaters : flue gasses go out and the heat stays.    And diesel. :/

These are probably both cheaper / better than a generator and lights, but would be more single purpose tools.

And yes, artificially loading up the mass is testing, and possibly testing things that are not the most important.

Good luck!

> [keep batteries at a good temp]

Put them in a vault in the ground below frost line. Insulate the top of the vault and the top of the hole (because you're not going to backfill and that space above the vault will want to follow out door temps). Wire as needed. Beware ground water.


Regards,
Rufus

What about a portable rocket that heats liquid that travels down flex pipes to send the heat into the abbey?  Could be used for all kinds of heat needs around the lab...

https://permies.com/t/131988/Portable-Rocket-Space-Heater