Canadian Off Grid Dome Cabin

[silentrob]

What an amazing resource this forum is.

Last year my wife and I bought 3 acres on a remote island near Vancouver and we are starting to build a weekend getaway. The property is off-grid so everything solar has been top of mind. The tiny-house itself will be a 32' diameter geodesic dome or roughly 950sq (including a loft).

Water comes from a well, 140' deep and is fed into a 800 gal cistern driven by a 115v 1/2 hp pump which my 3000w Honda generator has no problem running. This will provide enough water for the season and is gravity feed 300' down to the dome.

I had a 20' shopping container shipped over to help with logistics and serve as a shop and storage area + power center, so this thread could really be cross posted in both sections. I'm still designing and thinking though our requirements for power but narrowing in on a 48V system around 5 kwh which would be terminated in the container and then run 100 feet to a small breaker box under or in the dome itself. The needs are pretty minimal, a fridge, few lights and sound system that draws 11A/110V.

When I first starting thinking about power I was initially drawn to the Magnum Energy MS4048 Inverter but it seems like a MPP solar lv5048 all-in-one seems much more practical and I think I could plug the generator into as a backup.

As for batteries I really like lifepo4 in either a drop in or DIY, but really need to find a good BMS with low temp cutoff (being in BC we get days below zero between dec-march) and we may go all winter without even checking in on the property.

It seems like the longer I hold off the cheaper batteries seem to get, but 2020 will be the year I pull the trigger and setup solar.

New item by Rob Ellis

photos.app.goo.gl

New item by Rob Ellis

photos.app.goo.gl

Excited to be part of the community and I'll post updates as they come.
Rob

 

[AMcRae]

Rob, looks like a really cool project! Love to see a creative couple building their dream project together.
I'm new to this forum, but my wife & I have bought 5 acres in the mountains of Virginia and we've been designing various tiny houses in different configurations that might meet our "age in place" needs.

Like you, we think a shipping container would make a good workshop for our rural build. I am a Senior IT Technician so I need robust power, internet and backup systems for my work. So, I'll be watching your posts to see what you end up doing for your project. And I'll be sure to share whatever knowledge I acquire along our journey that might help you two in any way.

Best of luck on your project, and glad you have come to the diysolarforum to share.

 

[FilterGuy]

What an amazing resource this forum is.

As for batteries I really like lifepo4 in either a drop in or DIY, but really need to find a good BMS with low temp cutoff (being in BC we get days below zero between dec-march) and we may go all winter without even checking in on the property.

Rob. It looks like a fun project!!!

I have a similar/worse situation with a mountain cabin that will be unattended during the winter.
The temperature there has been know to be -42f and -20F is not unusual. The normal power source is a micro hydro turbine that is taken down when the cabin is empty.

It currently has Flooded Led-acid that went belly up way too quick. I will be switching to LiFePO4 and disconnect them when the cabin is vacant. My biggest concern is storage temperature. In addition to a BMS with a thermal cut-off, I plan on doing 3 things to deal with this:

1) Build a battery box with R30 insulation all the way around.
2) Put a small restive heat pad and thermostat in the box and hook that directly to a small 20 Watt solar panel.
3) In the storage box I will be putting two 5lb unfrozen freezer packs. (https://www.engelcoolers.com/engel-20-hard-shell-freezer-pak-large.html) . I calculated that the phase-change energy will hold the temp at their freezing point for a few days if the outside temp is at -20F.

I would like to also do earth-tubes to get some earth-contact warming into the battery shed, but that is probably a larger project than I will be able to do.

I am guessing that the weather on your island is warmer than at the mountain cabin. In fact, you are probably ok with just a good BMS with low-temp cutoff. You won't need to go as extreme as I plan, but I thought I would throw out the ideas.

 

[silentrob]

Ya, the main reason I'm leaning LiFePO4 over say, a lithium ion, was primary driven by the same concerns. I remember following Wills Tesla Battery project over a year ago and getting excited about the cost/density profile.

While I plan on building or souring an insulated box, I don't think I need to worry about it getting that cold here. You might want to research lifeypo4 battery cells. https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP100AHA-LiFeYPO4-3-2V-100Ah-TALL.html The data sheet says they can operate at -45°C up to 85°C.

And while water and power don't mix, one of the best way to regulate ambient temperature is by creating a bio mass using a water tank.

I'm still working out s cell configuration but leaning towards 16 100ah 3.2v cells wired in series to make a 48v bank. But I need a 16 wire BMS that supports 100ah.

 

[Deleted member 783]

While I plan on building or souring an insulated box, I don't think I need to worry about it getting that cold here. You might want to research lifeypo4 battery cells. https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP100AHA-LiFeYPO4-3-2V-100Ah-TALL.html The data sheet says they can operate at -45°C up to 85°C

Check those specs carefully. You can discharge them down to -45 C, but you cannot CHARGE them below freezing or you will damage them.

 

[Deleted member 783]

I dig the dome! Is that a kit, or built from scratch? What will be the exterior surface and how is it fastened?

 

[FilterGuy]

While I plan on building or souring an insulated box, I don't think I need to worry about it getting that cold here. You might want to research lifeypo4 battery cells. https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP100AHA-LiFeYPO4-3-2V-100Ah-TALL.html The data sheet says they can operate at -45°C up to 85°C.

I have looked at the LiFeYPO4. They would probably do a really good job for me. The big problem is price. I don't know if the price is high because they are more expensive to make or the market is smaller.

They also tend to be a bit larger but if that was the only issue I would certainly live with the larger size.

 

[offgriddle]

What an amazing resource this forum is.

Last year my wife and I bought 3 acres on a remote island near Vancouver and we are starting to build a weekend getaway. The property is off-grid so everything solar has been top of mind. The tiny-house itself will be a 32' diameter geodesic dome or roughly 950sq (including a loft).

Water comes from a well, 140' deep and is fed into a 800 gal cistern driven by a 115v 1/2 hp pump which my 3000w Honda generator has no problem running. This will provide enough water for the season and is gravity feed 300' down to the dome.

I had a 20' shopping container shipped over to help with logistics and serve as a shop and storage area + power center, so this thread could really be cross posted in both sections. I'm still designing and thinking though our requirements for power but narrowing in on a 48V system around 5 kwh which would be terminated in the container and then run 100 feet to a small breaker box under or in the dome itself. The needs are pretty minimal, a fridge, few lights and sound system that draws 11A/110V.

When I first starting thinking about power I was initially drawn to the Magnum Energy MS4048 Inverter but it seems like a MPP solar lv5048 all-in-one seems much more practical and I think I could plug the generator into as a backup.

As for batteries I really like lifepo4 in either a drop in or DIY, but really need to find a good BMS with low temp cutoff (being in BC we get days below zero between dec-march) and we may go all winter without even checking in on the property.

It seems like the longer I hold off the cheaper batteries seem to get, but 2020 will be the year I pull the trigger and setup solar.

New item by Rob Ellis

photos.app.goo.gl

New item by Rob Ellis

photos.app.goo.gl

Excited to be part of the community and I'll post updates as they come.
Rob

What will.the sound system consist of?

 

[AMcRae]

2) Put a small restive heat pad and thermostat in the box and hook that directly to a small 20 Watt solar panel.
3) In the storage box I will be putting two 5lb unfrozen freezer packs. (https://www.engelcoolers.com/engel-20-hard-shell-freezer-pak-large.html) . I calculated that the phase-change energy will hold the temp at their freezing point for a few days if the outside temp is at -20F.

I have been following a fellow who has built an off grid tiny house, and he had a problem where his LiFePO4 battery was getting drained by various phantom loads over a period when there were low temperatures & snow covering his roof-mounted horizontal PV panels. So, most likely, the battery's BMS got its low temperature cutoff triggered when some thawing uncovered a PV panel and tried to re-charge the battery below its cutoff temperature. When the battery went into cutoff mode, his MPPT charge controller powered down, so he returned to a totally dead solar power system when he finally returned for a visit. (I have heard similar stories on other forums from off grid solar power users who left their homes for several days during the winter and returned to dead systems for a variety of reasons.)

Building an insulated battery box seems to be really important, especially in off grid buildings that will not be self-heated when the owner is away. Days of freezing & sub-freezing interior temperatures (and periods of condensation) could reek havoc on solar power components if proper battery box & controller enclosure conditions are not maintained. Are there any experience-based diy guidelines available in the forum?

The tiny house builder started experimenting with USB resistive pad heaters, but we were all concerned about possible heating pad continuous cycling failure scenarios that could result in a short circuit and possible fire inside the battery box/system enclosure. I did some quick research into self-activated fire extinguisher systems and found the Elide Fire Ball https://www.amazon.com/Elide-Fire-Activation-Extinguisher-warranty/dp/B07BC653JC

Does anyone have any experience with the Elide Fire Ball or other self-activated fire suppression systems suitable for off grid situations?

Does the forum have any proven diy insulated battery box/controller enclosure designs for off grid cold climate conditions that we could review?

 

[FilterGuy]

... he had a problem where his LiFePO4 battery was getting drained by various phantom loads over a period when there were low temperatures & snow covering his roof-mounted horizontal PV panels...

Since the LiFePO4 self discharge is so low, I plan on disconnecting the batteries from the rest of the system while the cabin is vacant. This would ensure there is no phantom load. What I have not decided is if I will disconnect the BMS while away.

Are there any experience-based diy guidelines available in the forum?

I second that question!

we were all concerned about possible heating pad continuous cycling failure scenarios that could result in a short circuit and possible fire inside the battery box/system enclosure.

I have wondered about that too. That is one reason I am using a small independent 20 watt solar panel to power the heater. (Not the batteries). The max current possible will remain pretty low and I won't be draining the battery. (Note: the panel is mounted at a steep enough angle that snow should melt off as soon as it warms up. )

The heat pad I am planning on using is a high wattage 120 volt oil pan heater. I picked it for two reasons: 1) The resistance of the pad closely matches the Vmpp and Impp of my small solar panel and 2) the low voltage and current I will be putting through it is unlikely to ever create a problem of shorting out.

Furthermore I am planning on using old fashioned mechanical thermostats. These are pretty simple and reliable. The current we are talking about is relatively low and the load is resistiv. Therefore, the chance of the thermostat getting their points welded closed seems low. I was also thinking I should put a 2nd thermostat that cuts everything off if it gets too warm. The second one would be at a higher temp than the primary. Therefore, in normal situations it would only cycle when there is no current flowing. The chance both of them welding closed is extremely low. The failure mode is more likely to be that the thermostats don't close....ending up letting the batteries get too cold.

 

[Deleted member 783]

Just search "solar generator". You'll see lots of DIY battery boxes.

 

[silentrob]

I dig the dome! Is that a kit, or built from scratch? What will be the exterior surface and how is it fastened?

The Dome is a kit I ordered off Alibaba. The exterior is a heavy poly covered cotton surface. Imagine a circus tent material and the inside will be lined with a 1cm cotton insulation for both sound and heat insulation. Fdomes.com has a pretty good "marketing site" for them.

 

[Deleted member 783]

The Dome is a kit I ordered off Alibaba. The exterior is a heavy poly covered cotton surface. Imagine a circus tent material and the inside will be lined with a 1cm cotton insulation for both sound and heat insulation. Fdomes.com has a pretty good "marketing site" for them.

Interesting. Do you frame out the inside? Very interested to see the progress on that.

 

[silentrob]

What will.the sound system consist of?

Ha, I was wondering if anyone was going to comment on that. I have 2 12" loudspeakers and a dual 18" sub (from PK Sound). Plus a mixer and Pioneer DJ setup.

 

[silentrob]

Interesting. Do you frame out the inside? Very interested to see the progress on that.

Yes, the inside will be framed... and I'm still working out the layout. But it will basically be a one bedroom bathroom main floor and a loft with 2 double beds. The front is a giant clear window so it will have a natural "great room" in the front half and the loft will sit on top of the bathroom / bedroom.

 

[offgriddle]

Ha, I was wondering if anyone was going to comment on that. I have 2 12" loudspeakers and a dual 18" sub (from PK Sound). Plus a mixer and Pioneer DJ setup.

That's a very credible sound system for a backwoods, off grid retreat. I haven't yet hooked up my new, (I bought it four years ago and it's still in the box), 12 volt pioneer automotive receiver, but I will, some day, and I'll probably build it into a cabinet of some sort! Rock on fellow off gridder and Merry Christmas, (or the equivalent), if you're into that sort of thing! ?

 

[silentrob]

It has been a few months since updating this thread.

I installed 9 solar panels 385W Bi-facia and run them to the battery bank below. 32 3.2v 100ah LIFEPO4 cells. (2 x 48v @ 100ah)
The MPP Solar now runs to a 80amp panel, and a sub panel under the dome 150 feet away.

This year I put the cover on the dome, framed it, and got most of the deck finished. We are still working on the covered section and outside kitchen.

Still lots of work to do, but it is all coming together.

 

[silentrob]

And yes, I direct shorted a cell, the clip of Will chuckling "you are going to have a bad day" has been forever ingrained in my mind.
Be carful, and don't stop leaning.