Yes, it would make a difference. I think 6" flue pipe is too small to handle the output of a rocket core like mine (8" x 9" cross section). The most important base factor is the size of your sap pan. How big is it? I built a very similar core for my second evaporator which has 6 square feet of surface, and it boils madly over much of the surface. The 8 square foot pan would only boil over maybe half of its surface.
Our off-grid solar is/was very expensive, but our property doesn't have grid access. Once you get used to it, it's fairly easy to manage. We have a well-pump that is on a timer so that it only pumps during daytime hours. It pumps up to 2 tanks totaling 5000 gallons that are then gravity fed to the houses. There are things that I like about being off-grid. It forces you to be hyperaware of your energy usage. But you are also going to have times where just nothing works properly and you have to wait for parts or help, etc.
I believe the theory is sound but the problem you will run into is the inefficiencies of each part leaving no surplus. As mentioned above stirlings can be very efficient as long as they operate at high pressure with highly conductive materials and high temperature differentials between hot and cold. The whispergen from a decade ago was a good attempt at a commercial unit it used a sealed free piston design similar to spacecraft stirlings. It had promise then the cost of solar dropped like a stone. You mentioned a 2 hp engine which with losses will produce at best 1.25hp or roughly 1 kW per hour of electricity at full temperature production. By unpressurized Stirling standards that engine would weight several hundred pounds and require continuous maintenance. For roughly 1000 dollars you can do the same with solar and have no moving parts or maintenance... Not to be discouraging but it might go some way into explaining why you dont see stirlings around much. I would try it with tegs myself. Their efficiency is not great but would be similar to a homebuilt stirling. All opinions of course but I did chase the stirling rabbit down the hole for a while.
You just have to click the freebie link within 48 hours. Once you click a freebie link, you then have eternal access to the freebie and it's downloads. So, yes, please keep trying! (You can see a list of all the freebie/digital market stuff you have access to here: permies.com/forums/premium/list/#mystuff)
I'll keep looking into this to see if I can figure why it's not working for you.
What advantages does the Si battery chemistry give over other battery chemistries?
At present I have a little 12v, 15 ah battery box that provides me USB and 12v dc power.
I plan to build a 100 ah version with a 1000 watt inverter for ac power and a host of dc outputs. I was thinking about using an SLA battery for simplicity and budgetary reasons, but I am open to other battery types if they have desirable attributes.
Cleaning glass on woodstove? When it's cool, use a little of your ash and water (I use a spray bottle and dampen the rag). Swirl this on, it will take off all the crud on the glass. You may have to scrub a few times. Then spray clean water on glass and remove whatever slurry remains.
No more crud on glass. Nothing to buy. Use up what you have anyway. Hurrah!
C. West wrote:Me and my girlfriend have been looking at pre fab and simple design houses and trailers and the one we are most impressed by cost and looks wise is avrame.
As far as we can tell (and I have had some correspondence with the company as well) you buy the plans and they contact a lumber mill near you to cut the pieces needed to build and send to your location. after that we use the plans given and build, if I remember correct it takes only a few weeks, and only needs two people
ill linkto their website s those more experienced than me can take a look.
My main concerns are whether I as an inexperienced builder (have to framing and roofing, as well as helped build some sheds) am biting off more than I can chew, and the other main concern is that its hard to find any reviews, positive or negative. All info and videos of the a-frames come from them.
what do you all think?
ps I plan on heating it with a rocket mass heater, any concerns there with its shape/floor?
Any input welcome.
did anything come of this? Most of ontario townships have square footage minimums that rule out tiny homes. Curious if it went forwards...
I would suggest you look into whether or not your geology might support a sand point well. In the right conditions, they can have more than adequate output for your needs. I might not be correct about your specific situation, but my feeling is that it stands a chance of being a cheaper, better solution, if it's suitable.
I agree with what is posted here. We have been totally off the grid since 1986 and it is still a learning curve. The big message here is that the right box of tricks must be used for the job or it will not work in any way shape or form. A conventional car battery charger will not charge deep cycle batteries. The amount of energy required to get those poor struggling electrons from one side to the other is simply insufficient. You will need a proper "solar battery"charger with multiple stage charge manager. If you can access the electrolyte in the battery check the pH. It is likely that with multiple deep discharges, you battery is far from healthy and may need a good deep charge to reinvigorate it. I agree that the best way forward is 6 X 2 volt batteries. Without going into the electro-chemical stuff, the batteries fair better than a single 12 volt battery. But set your battery cutout at 11.8 max unless they are lithium (which I would not waste money on).
With your LEDs, they need a driver to make them work. The bottom end LEDs have an under powered driver that will burn out and cause issues. We buy a good quality LED light or string then match the driver, ensuring it has 10 - 20% more available power than required. Our LEDs are 10 - 15 watt but the drivers are all 22 watt so they do not get hot. Strings of LEDs can be bought ex Asia and you can make your own string by buying coloured (Aussie - we still use the 'U') tube. Seal one end and run wires from the end. 12 volt strings are available. so there is no DC > AC > DC and hence no power conversion losses that can be as much as 80% on top of the nominal draw. So 50 watt lights would use 75watts of draw. For every 110 volt appliance/ item you have, take the wattage and add the value that your inverter says will be used as well as resistance in the wire. You will be surprised how much power is lost to heat (resistance)
We have just upgraded our system by buying the components as we could afford them and now we have them all have done the job. You will never be up with the latest technology so don't try. Get what works for your intended power load and go for it. Just one note of caution, make sure that your regulators/ charge controllers have only about 80% capacity going through them. A work around and way cheaper option is to use a Solid state relay (SSR) run by your regulator. We have a 10 amp regulator and 100 amp SSR to manage 5 X 200 watt panels (20% spare capacity).
Burial is the no maintenance way of keeping the water from freezing. Even if you have no slope, if you bury it, you have now moved the water from an inaccessible 200’ to an easily accessible 8’-10’ below ground. You can run a battery powered Rv pump to supply water to your Rv and it won’t use much power and you could put a cheap hand pump pitcher pump as a backup.
I’m off grid and my water is 17’ deep. I have an Rv pump a couple feet above the water and it pumps it to the trailer we live in. I use a marine battery to power the pump and I only have to charge the battery every couple of months.
My water line to the trailer is buried 5’ deep. If we leave during the winter, I turn off the switch to the pump, which is at ground level, open a faucet in the house and a faucet on the outside of the house. I go down in the well, pop off the line to the pump and allow the water to drain back so no water is left in the line.
It is common to have two pumps. One being the deep well pump that moves it to the surface, the second a pump to supply pressure from the tank. As stated, the tank acts like a battery that stores water.
I’d personally backfill around the tank, then make an umbrella of 2” pink styrofoam over the top to keep it from freezing in very extreme temps. Maybe overkill, maybe not. Where my place is in North Idaho we rarely see colder than -5, but I’ve heard it has reached well past -40. Where I work in North Dakota I once saw it -73 on the thermometer and when it was that cold a backhoe drove over the septic tank of the trailer I was living in, driving the frost down to the tank. The top of the tank was 7’ deep and the tank froze. It was two or three months before it thawed out. A layer of insulation (and perhaps fencing off the area above the tank) would have prevented that. It sure was cold going to a portajohn til spring! Perhaps even cedar bark would work if you have a local sawmill or pole mill you could get it from.
Speaking of that, I’ve heard of people burying their water line, backfilling a foot or so, then throwing a small tree (3”-4” in diameter) on top and backfilling to the surface. The wood stops the frost from being driven down to the pipe.
As a journeyman carpenter a builder and a renovator here are a few I would want to think of:
Back up power. Preferably solar of course but you can start by having an electrician in to install a manual backup generator panel and transfer over all the critical house loads that can keep you up and running. From there you can have a simple generator plug outside, a full autostart genny if you prefer or down the road a solar array, batteries and an inverter to run the loads on the backup panel. It's also a great time to have him look at worn breakers, worn out outlets, fixtures etc...
Insulation: caulking around window trim inside and out.,
Upgrading the windows if drafty. Seals around doors. Check the attic for insulation. Replace all vents through the building if worn, caulk all penetrations. Figure out if there are rooms that can be closed off if not in use and close off their heat vents or lower thermostats.
Just the top of my head stuff. At 51 I'm not quite there yet. We are building a new house right now and will incorporate all that and more.
Cheers, David Baillie
Awesome video and information. I'm not exactly that off-grid. I do have a SunPower solar panel system set up that's still connected to the grid, but reduced my grid payments to nothing. The storage solution they offer is a bit cleaner than Tesla's as well. I do plan on making a hunting spot in the woods, I might have to incorporate a few of your ideas for that since it would be off-grid too.
Lisa Sampson wrote:We typically run around 1kW per day of usage especially with the power tools. I was hoping to learn from you guys what works well, what doesn't work well, and what you would do differently if you had to do it all over again. Since ours will be a new system, maybe we can avoid some mistakes that others have already made. We are looking at some property that has a well but no electrics. The water is potable but we haven't done solar before so we are not sure how this might work.
I have about a million questions and I would love to pick your collective brains about this. I am a tech geek by trade so we have to have power for electronics and interwebz so I can work remotely. Hubby needs a metal and wood shop so between us we pull a lot of power. I am already planning to convert to propane for some of the larger appliances (stove, oven, clothes dryer, water heater, winter heating). That still leaves the AC, fans, fridge, washing machine, dishwasher, hair dryer, lights, TV, and all my techie gear sucking power. If any of the other power pigs can be converted to DC, I am definitely open to suggestions.
For the shop, DHB (Dear Hunny Bunny) needs to be able to run saws, lathes, drill press, press break, air compressor, and possibly some CNC stuff (which we will need to acquire). His welder has its own generator so that at least isn't an issue. Some of his things will run on DC just fine but not everything so some stuff will require an inverter to function.
I know that I need 2 separate systems with one for the house and one for his workshop. When we had a regular grid tied house, I would have to shut things off for him to do work so that we didn't blow breakers and we ended up going to 200 AMP service from the grid. That was the highest amp service we could get without getting a second meter. We were actually looking at getting a 2nd electric meter with separate service for his workshop when life threw us a curve ball and we took an overseas assignment. Anyway, splitting everything into two systems brings down the both the amps and the volts that would be necessary to manage to safer and more reasonable levels. I prefer to keep volts and amps in the "OW" range or maybe the "OW and bad words" range and out of the "Fried" range since DHB isn't always super careful about throwing breakers and testing to be sure things are no longer energized. Hes been better since he discovered that the water heater was still on the hard way but I would rather not have a crispy DHB.
I would love to hear your experiences with solar only vs solar and wind hybrid systems. Texas is pretty flat so hydro is probably not an option. However, when its not sunny, its usually pretty windy. Its generally pretty windy even when it is sunny so our thought was to use wind, particularly overnight when our consumption drops to almost nil, to help make up for cloudy days. I am particularly interested in the Lead Acid vs AGM vs Lithium advice anyone can give. Space and weight aren't that much of an issue for us since we plan use a small shipping container to house the batteries and most of the gear.
Hi Lisa, your situation sound similar to a lot of off grid users who do trades type shop work. Usually in your case you would only do one system but a good one and dear hubby would have to adjust his work somewhat to an off grid life. The heart of your system would probably be up to 5kw of solar, a 48 volts DC inverter system that would do 220 power and a larger than usual generator that can carry hubby's biggest single load with a 2 to 4 kw reserve for battery charging and house loads. If he is doing small power tool work the inverter handles it if he has a heavy draw day planned the genny is on... I'm partial to the outback radian with their fm100 or the stacked magnum 9kw inverters with their pt100 charger. If you can swing the expense you will never regret it. If you try to cobble up a system for large loads you will be saving dollars but buying a lifetime of fiddling around and unmet goals ...
David Huang wrote:I'm not sure what level of interest others might have but as an off-solar person I've never gotten into all that complex data monitoring. I've been tempted sometime to run a line from the barn where all the equipment is to the house so I can see what the battery level is at during long periods of cloudy days, but instead just hike out and look figuring I could use the exercise. I personally have little interest in connecting my system to the internet. I have no idea what virus and stuff could be caught out there! ;) It seems like a more secure system if I keep it isolated.
David, most of the systems mentioned above will either report to a web based platform or to a offline network to your computer. Something else to consider for the system you are designing Nuno; make sure it can work offline also with an on board browser of some sort since many off grid locations either dont have internet or dont want to share their data...
Most of the answers are already given, and are fine.
Here is just my 2 cent on it:
The input of a solar charge controller is designed to suck the most current (wattage to be precise) as possible out of the solar panel. (PWM or MPPT based charge controllers).
So even if the generator could supply a matching DC voltage, you risk overloading the supply source (the generator).
The (mppt) based) charge controller would "think" like this:
<mmpt program inside>
Ah, I'll start slow: gimme 10W watts.
Ok, that went fine, now give me 20W... Ok, still fine, 30W please. Oh that supply voltage still looks good, 40W please...50W...60W...70W.....
.....and it wont stop until it either the charge controller is at it's limit .... or the supply source is overloaded.
</mmpt program inside>
For a solar application this is great because you would want to extract as much enery out of the solar panel(s).
Once you hit absorbtion, the algorithm will change, and only draw as much current as is needed for maintaining the absorbtion voltage (for the attached batteries).
If you still need help .. I would, in your place, disconnect all the loads and stay without electricity until you get an ok charge on your batteries.
To know that you don't kill your batteries .. search for "battery protect" from Victron. It is pretty easy to setup and it will kill your loads if the voltage drops so it hurts your batteries.
Also .. with so little power .. don't waste it on an inverter if you really don't need it. I mean .. probably yours is 80% efficient so a lot of power wasted. You wrote about bulbs and a phone charger .. they can run directly on 12/24v, there are a tone of cheap chargers with USB outputs (for the phone charger).
Joshua Myrvaagnes wrote:Wow, this is an amazing set of experiments. I will have to revisit it when I'm less fatigued.
I love the design of having the collector completely covering the open window and sealing that in.
I had trouble understanding some of the wording of things. What does this part mean?
C. Letellier wrote:
2. Whole collector box cools off at night to outdoor temperatures. Minimal mass, sealed off from the house and a really good black body radiation surface virtually guarantees this right thru the glass. The very things that makes it a good absorber make it a good emitter too.
how is it sealed off from the house? and if it were, how would that make it more of an emitter of the house's heat, rather than less of an emitter? thanks
The window opens and closes at the top. It is a standard 2 foot square hand crank anderson window. Since the crank is 10 ft off the floor I have a pole with a bent head with pipe socket on it that I use to run the crank. In the basement the box is closed off by a butterfly door. If you look at the fan picture you will see a 1/2" metal rod running right across the middle of the picture. The door just drops on it. I chose to do the butterfly door with essentially hinges in the middle on the pivot with the thinking that I wanted to run it with a small servo so I wanted a mostly counter balanced design to do so. This was to keep from lifting a the full weight of the door one way or the other..
So when I open the collector up, I open the window and I am currently simply lifting the door completely out in the basement since it snaps in and that is easier and faster that blocking it up so it doesn't close. Then I turn a power switch on an outlet strip on to run the fans and with that I am doing roughly 6 to 7 air changes an hour out of the basement and into the upstairs thru the collector. Inside the house I am using an old windshield box as duct from the basement ceiling where the butterfly valve is down to the basement floor so the coldest air in the house.(within 5 inches of the basement floor) is gathered and carried thru the collector. Today the house reached 88 having started the day at 72.(while it started the day below freezing at 23 outside and it reached low 60's outside at peak The basement 6 inches off the floor the air temp started at 68 and right now is 72 at dark. By morning I expect it to have fallen to 69. So I added a degree to the basement today that I can rob back some cold or gray day.
As for your question on the cooling that is black body radiation and since I am not sure I completely understand it someone please correct me if I get this wrong. Basically most(not all because of material properties) black items get warmer faster than the same item in white. But the converse is also true that black items cool off faster because they radiate more heat out because of their color. Thus an uninsulated box with one glass side and very little mass inside that is black is going to cool off faster once it is no longer receiving heat from either the sun or from inside the house. Closing the butterfly door and the window cut it off from the house heat mostly(some small air leaks and poor insulation of door and window so small amounts of heat leak out), and the sun going down eliminates that heat source so the collector box being black is going to get colder faster as it radiates that heat to the sky and thus to space. In fact depending on optics of how much space it sees verses how much other heat radiating sources it sees the box may actually get colder than the ambient outdoor temperature. With snow on the ground the collector sees very little other radiating heat sources and a lot of sky so it might actually get colder than outdoor ambient on clear cloudless nights. Preventing this would mean adding insulation and automated insulated shutters on the front over the collector glass to keep the heat in the collector box. Not practical so instead the box gets cold each night and on sunny days the suns first job is to rewarm it. Being relatively low mass this doesn't take much.
If this doesn't answer your question suggest looking up black body radiation and radiant cooling as I am really struggling to convey a topic I only marginally understand.
Right now the if the windows on the house doing passive are one heat source and we call that 100% The current collector as it stands adds another 20%+. I have enough glass gathered and need to get the boxes built to mount it on.(health problems interfered this fall) to increase the collector area to nearly 90%. Thus if passive is 100% and active is 90% I should in theory be nearly doubling the solar heat for the house. Now it won't be nearly that good because most of the glass I have is single pane so higher losses there. Also about half of the new intended collector area is going to be passively driving an HRV core meaning the air gets hotter, increase drag losses and losses of energy because it is moving air rather than adding heat. Just guessing adding those but I expect it to mean my total will be more on the order of 150-160% of what I started with. Now I also intend to waste a bit more of this heat at times in hopes that I can get the cloths drier mostly using solar heat to run rather than gas. But the hope is I can recover part of this heat on the outlet end too.
Here are some pictures that were requested on the oil burner.
It is a #2 burner and soft 1/8" copper tubing. The burner wick tube is cut flush with the top of the base burner. I drilled 2 holes through the burner assembly that just miss the wick driver assembly. The tubing is left unsoldered and each end raps around the wick a little bit for heat transfer. The loop is heated by the flame. I have tried it both crossing the flame and beside the flame and they both work. Its harvest season and I haven't been near a computer so thank you for being patient. I am happy to try to help you build one.
Thank you all for the responses. It seems the consensus is that the heat gain from the summer months is not the goal here.
I am planning to get some insulated shades for the skylights that we can open at night in the summers and in the day for winter. We are debating if the cost of the motorized ones is worth it over the ones that use a pole to open/close. I think we will probably end up just getting 2 of each. That way if we’re feeling lazy that day we can at least manage to get half of the skylights used properly.
I certainly am experiencing what most of you have described about skylights not being all that effective for passive solar use.
I’m glad that a previous owner planted some maple trees on the east side so we will get the benefit of their shade in years to come.
I’m grateful that the community here was so helpful and quick to respond!
How about this one?
According to physics you can only suck water so high (10m or 33ft) until the air pressure exceeds the vapor pressor of water and it turns from liquid to gas.
Problem is: Have you ever seen a tree over 33 ft? Often. So how do they do it?? Different scientists have a few different theories but really don't know 100% for sure, but it involves growing up with water continually in the pores such that there are no sites for gas to form.
If you can try to locate some old patio doors. they tend to pe tempered glass which can deal well with the heat the cell put off. Build your own has kind of gone away with dirt cheap panels. Lots of adds online for 230-260 watt panels for anywhere from 15 to 25 cents a watt all done... Lots of the farms have upgraded to the newer panels and flooded the market with 7-10 year old perfectly good panels...
Just a thought. Good luck on your project.
I am going to go the other way on this issue. Heat energy done right looks so much better I would say. A good large tank designed to encourage stratification and it should be able to do hot water heating, household heat and air conditioning all in the same system. During the winter store all heat using the lower heat for household heating and the hot heat for hot water heating. In the summer start throwing the low level heat away every night using the solar collector as radiant cooler and the stratification to keep the cold water from hurting the hot water so they can be stored in the same tank. During the day use the cold of the tank to cool the brine before it comes back into the house to gather humidity. Neat thing is the low power needs of this system and lack of toxic stuff making it. And as quality of glass etc gets better there is no reason why such systems shouldn't run for a century or more with minimal maintenance.
Here is something I wrote up else where discussing the beginnings of even how to maybe do this all on a real budget.
Here is the link to the dream storage system It starts at about 1 hour and 11 minutes
https://www.youtube.com/watch?time_continue=4268&v=AtHkvpRI6fc&feature=emb_logo Then about 6 weeks ago I tripped over a DYI storage tank that might be in my budget and able to be fitted to my space. That one lead eventually lead me to this video that best explains it. Now my tank shape would be different.
https://www.youtube.com/watch?v=bI0T7ZegAPU Combine that with a drain back collector so no antifreeze needed and the above article that would indicate that pex would work for the collector tubing as plastic and suddenly the numbers look way more doable cost wise. Now PEX is very UV sensitive but apparently they are getting far longer life expectancies out of it by a simple coat of black paint to protect it from the UV that also increases its absorbtion. When I first started looking Walmart had one of the rubber membrane sheets(large enough) special for $53. So with some hunting I assume it is possible to get down in that sort of price range again. 300 ft of pex for $100 using 200 of it in the collector and 100 ft of it in the tank as a heat exchanger to preheat the city water going into the existing water heater. Another hundred for the pump. If I could do the insulation, wood work and misc for $500 to $600. Most of the wood work could be reduced in cost if I can get pallet topper plywood sheets free and piece and laminate them to bigger sheets to build the hot water tank box inside and the outdoor collectors. And the final big cost would be for a tempering/mixing valve for the outlet of the water heater to keep the hotter hot water from scalding anyone. I have already gathered the glass to cover the collectors and all I have in it is some fuel to go get the glass.
Now why do it? That sounds sort of expensive compared to just buying a hot water heater and it certainly is going to eat a fairly large piece of floor for an insulated tank holding 300 gallons of hot water. (roughly 24 square feet of floor space) Well I burn roughly 250 gallons of year of propane doing hot water, clothes drier and cook stove. Say I could knock 150 gallons off that. If propane was $2 a gallon(keeping the math easy) that would be $300 a year savings and the pay back period would be less than 3 years likely. And even if propane fell to $1 a gallon it would still pay back in 6 years. The membrane they are listing as a 20 or 30 year life expectancy. Pretend it only does 10 in this application Pex as a collector rating unknown but lets pretend we can get 10 out of it. The pump there again should be 10 plus. The rest of the system should be good for many decades. So potentially looking at say $300 once a decade on materials for repair. The numbers now look really good. And reducing the second highest single energy use in a normal household is good for the environment too. Total energy input would be say 50 watts 5 to 7 hours a day 4 or 5 days a week. There again very doable. More importantly this one only needs to run while the sun shines making it ideal for photovoltaic solar drive..
In the process of researching this I also tripped over desicant air condition and it is possible to possibly combine all of this into a single system. Now things are better still.
Douglas Alpenstock wrote:Agree, handled correctly there would be no waste heat at all.
A boiler is always more efficient, though it may tie you to a pump. I've heard something about thermosiphon setups but don't know much.
An outdoor boiler is something that insurance people understand. These are often tied in to in-floor heating. Or a radiator coil is added to the forced air furnace.
A fully pressurized system will freak them out, though, and they'll ask "where's the engineer's stamp?"
A small pump is not a big deal... all depends on how much juice you need to burn.. and when.
I would imagine a nice thick thermal mass floor could coast through a cold night, and then you run the pump to replenish this heat battery from another source in the daytime... Haven't tried to do the math on that theory yet though.
I got a short tour of a very fancy brand new house a couple years ago; off grid, up a mountain not too far from me. All done with permits... but, soon as that was all sorted, this guy installed a huge outdoor boiler and plumbed it up to the indoor hydronic floors. Think the official heat source was a propane boiler, but it was never seeing use.
He builds & sellers these boilers, made out of two nested chunks of pipe. Maybe 30 and 36" diameter?
He figured he was safe insurance-wise because it was not in the insured building... hm.
As far as batteries- the most expensive and fragile part of a system- you might try industrial batteries. They are big heavy and expensive but last a lot longer. We’re running 4 Trojan Ind17-6’s now for almost 7 years and they’re still doing well. About to add a separate system with 4 Rolls 27-6’s. These were had for less than the Trojans bought years ago. It really pays to shop around for batteries!!! Saved hundreds if not a thousand $ Smart vendors will compete for your business if only you ask. If they’re put off, buy elsewhere. Ours we got from Solarbiz- they were very good and have been in solar business since Adam went off-grid.
Try shopping Craigslist ( Craig should get a Nobel prize)- I’ve seen great deals on entire systems. Happy hunting. Tom
Vince - that is a super rich response. Can I get an apple here ? Can I give an apple ? I don't know how that fully works but I know a lot more about this freezer equation now. Excellent.
Not that I will be doing this right now anyway, but given this info I think the best bet is to, as you say ditch the idea of running the freezer off the battery at all, this lightening the battery load greatly and keeping it free for other basics. Lights and devices mostly. Maybe by then Ill want a fridge haha...would be good to find a 12v unit though since they are fairly available out of old RV's and would be much more efficient.
I would also probably not bother with the smaller freezer and instead try to find a larger chest freezer nearby on craigslist, not transport my small one, and get as much mass in as possible. I would opt for the rectangular 2L milk jugs and line the whole of it. I've made brine at 5% before for fermentation purposes so that should be easy enough once I figure out the % i need considering the mass available and desired temperature.
On another, non-freezer related note. This project has evolved a bit since playing with the thermostat I bought. If/Once I get it to work I'll post about it but here's the rundown:
My generator is a firman with keyfob remote start/stop. I'm working on building a voltage sensing circuit to turn it on and off with an arduino and a 433Mhz transmitter board.
The goal would be to code it to check the voltage every minute or so. Once it drops below X (11.75v maybe) it would would make a start attempt and start rechecking the voltage more regularly to ensure the start was successful. If not, rinse and repeat a few times...not sure where to go if it doesn't work...let's get it functional first (Maybe rig it to an old cell phone to send me a text or otherwise warn me.) It would then go through an as yet undetermined duty cycle to charge up the battery. This could be time based or rely on the voltage sensor.
This may be completely unnecessary but I have the stuff, and winter is coming. I'll decode the keyfob with my SDR (software defined radio) and take it from there. Then once I have a solar panel integrated it will be an automated backup for when the sun isn't shining.
I was speaking to my buddy, a red seal electrician who specializes in solar installs in BC...there's a word for the commercial version of this unit...but I can't remember it.
Thanks again for all the great responses, and thanks Vince for clearly demonstrating how the thermal mass is really the most appropriate and likely efficient solution to the initial problem discussed.
If you want to incorporate solar electric heat it gets easy if you run pex and water. There are 24 volt dc rated heating elements that could take the feed from a 60 cell panel when it was available....
I find that "tinkly char" can also be made in an actively managed open burn pit, though there is more ash content. It may not be as good, but I make wheelbarrows full at a time, so maybe that compensates a little. It's great to add stable carbon to soil, for many reasons.
Looking at Sean's excellent and well-considered video, I'm taken down memory lane, and realize how much I miss my old wood stove.