Saturday, July 30, 2016

Solar Shed Summary: My Off Grid Office

A few months ago I moved to a few acres in the country, and needed somewhere to work - so I built myself a solar powered off grid office out of a Tuff-Shed Pro Studio!

On one side, I've built a great desk corner with plenty of power and more than enough AC to keep me cool when it's over 100F out.

On the other side, I've built an awesome lab bench for small electronics projects and battery builds.

It all started with this.

That's an 8'x12' Tuff Shed Premier Pro Studio.  I spent around three and a half weeks turning it into my very own office.

Highlights include:
  • Aggressive insulation for year round use: 3.5" of rock wool (5.5" in the ceiling), plus 2" of foamboard on all walls and the ceiling.
  • Plywood interior walls, because I think they look good and they make it easy to mount things.
  • 2kW of solar panels on swinging mounts for power.
  • 12kWh of Trojan T105RE batteries in a 48v bank for storage.
  • A 2kW Aims Power inverter for 110v power.
  • A through-wall heat pump for cooling and heating.
  • Desk space, wall mounted monitors, a lab bench, and plenty of shelving.
This is a summary of my build, with links after each section to posts that contain radically more information (and way, way more photos) of each build stage.

Keep reading for a summary of the entire process!

Why a shed?  Why off grid?

A few months ago, I moved to a beautiful rural location in sunny farm country, and I work from home.  I do some generic tech work, some battery pack rebuilding, and some teardown/analysis/reverse engineering of various gizmos (usually cheap stuff out of China).

A standalone structure gives me space to work that's separate from the house.  This is important to me for several reasons:
  • If I share work and home space, I have a very hard time separating work from "not-work."  I've learned this lesson in the past, and don't care to repeat it.
  • I prefer quiet spaces, suited to concentration, for working.  A house with a wife and kid isn't this.  On other occasions, aggressive symphonic metal at high volumes is useful.  I've worn headphones for a lot of my working life, and don't want to wear them if I don't have to.
  • Some of my work involves fumes - soldering, spot welding, adhesives, etc.  I don't want these in the house.
  • I play with high energy battery packs.  A 500Wh pack shorting out is very exciting - I want a separate space for this.

Why solar?  This is also a blend of several reasons.
  • The property I'm working with has many basalt outcroppings ("lava rock").  This stuff is hard, near to the surface or poking above it, and basically impossible to trench through.  You blast it.  That's expensive and time consuming.  Worse, trenching power requires going either 1' deep with conduit, or 2' for underground feeder.  You hit plenty of rock long before that point.  So trenching power just isn't feasible unless I go the very, very long way around.
  • I've always wanted an off grid solar system to experiment with, and if it's powering my office it will only annoy me if it's acting up.
  • It provides an amazing real-world testbed for working with cheap charge controllers/panels/etc to see if they're any good.

Why a Tuff-Shed?  They offered me the best price.  Why start with a shed instead of building something from the ground up?
  • My framing skills are not very good, and a pre-framed structure is faster for me to get up and online.
  • They make this really cute Pro Studio that is just perfect for something like this.
  • Because I was able to build a level foundation and had truck access to the location, I got a killer deal on a pre-built demo unit (40% off retail).

This is my shed before delivery.  It's an 8x12 Pro Studio, with a nice door, windows, and a workbench (that I'll have to remove to insulate it).  This particular version comes with a radiant barrier on the ceiling, Tyvek Home Wrap inside the siding, and a shingled roof.  I'd prefer a metal roof, but for a 40% discount I can overlook a few things.

More details: Solar Shed: Part 1: Overview 

Foundation & Delivery

I had to build the foundation quickly.  I purchased the shed on a Tuesday and it was delivered Friday.  Because it's a pre-built demo unit, the installers can't block the flooring like they do with most units.  I spent a few days with a shovel, some guide wood, and an absolutely ancient generator to create a level surface for the shed.

Friday morning, the shed showed up on the back of a trailer.  Literally.

After spinning it around on the truck with the aid of a driveway and some wood blocks, a pair of absolutely masterful shed movers dropped the shed on my foundation, and I had a shed ready for interior work!

More details on building the foundation: Solar Shed: Part 2: Foundations

More details of the delivery: Solar Shed: Part 3: Delivery

Window & Door Foam

One limitation of a solar powered shed is that of energy - which means energy efficiency is important!  This shed is decent built, but has utterly zero insulation - so I fixed the glitch.

To help seal up the windows and door, I used Great Stuff foam.  There were large cavities around the window frames and door frame, and that's just not any good for blocking heat.

The door frame is literally allowing daylight through.  I'm fairly confident that will leak during hot summers and cold winters.

To seal these openings permanently and effectively, I filled all the gaps around the doors and windows with Great Stuff Foam.

After letting the foam set up, I needed to trim it back, which is easily enough done with a knife.

After cutting the foam back, the windows and doors are nicely sealed around the edges.  If I wanted to put some molding up to hide the foam, I could, but I simply don't care that much.

Rock Wool Insulation

Instead of using standard fiberglass insulation, I decided to use rock wool (or mineral wool) insulation batts.  It's fireproof, more soundproof, easier to install than fiberglass, and the cost, while higher, isn't a huge factor on such a small space.  I used Thermafiber instead of the more common Roxul, simply because it was what I could find locally.

The insulation value is basically the same as fiberglass - R13 for 2x4 walls, R21 for 2x6 rafters.

The batts are 4' long, and installation involves pressing them between the studs.  They're friction fit, and easy to cut to length and shape for the other spaces.

After a few hours of work, the walls were done.  The stuff is really rather nice to work with!

The ceiling took a bit more work, and involved quite a few false starts (including duct tape - it does not solve all problems) before coming up with a solution that worked.  Not using the correct size insulation and trying to cut it to fit contributed greatly to my troubles, but it's up!

More details on the window foam and rock wool installation, including a discussion on what I learned about vapor barriers during the processSolar Shed: Part 4: Wall Insulation and Window Foam

Experiments on how not to install rock wool in a ceiling: Solar Shed: Part 5: Roof Insulation

Foam Board Insulation

In addition to the rock wool, I added a full layer of 2" thick foamboard on the inside (both the walls and ceiling).  All the corners and joints are taped with aluminum insulation tape.  This layer adds additional insulation (another R10 around), and offers a windproof shell to help keep the inside air and outside air separated.

Contrary to popular belief, house wrap on the outside and foam board on the inside does not lead to a double vapor barrier.  It's actually closer to half a vapor barrier.  For the curious, I delve deeply into this in the main post on foam board installation.

I cut the foamboard to shape with a saw, coated the studs with a bead of construction adhesive, screwed the foamboard in to hold it, then taped the joints.  The red chalk lines mark the stud locations, both for driving the screws, and for later reference when installing the plywood.

It's like putting together a big jigsaw puzzle where you get to cut the pieces out!

The ceiling was a bit of a challenge to hang solo, but I managed.  The layer of foamboard should give me a nice and tight interior, where air exchange is done deliberately, not just because the wind is blowing.

More details on installing the foamboard: Solar Shed: Part 6: Foamboard Insulation

Plywooding the Walls

For my interior walls, I opted to go with plywood instead of drywall.  Why?
  • Plywood gives me a solid surface for mounting shelves, monitors, charge controllers, etc.  Drywall doesn't.  With the studs hidden behind 2" of foamboard, having a solid mounting surface is nice.
  • I like the look of plywood interiors, and I can do it here.
  • I hate drywalling and mudding.  And I'm not any good at it.
  • As my structure is too small to require permits or inspections, I don't need to abide by silly bits of code.  I'm not concerned with room-to-room fire spread resistance in a single room office.

The 1/2" plywood goes up similarly to the foamboard, though I'm using 4" screws to secure it to the studs.  I tried to use a different pattern from the foamboard, when possible, to help smooth out seams.

After the large pieces are up, it's back to "puzzle mode."  Measure, cut, install.  Like the foamboard, the plywood is glued as well as screwed.  I went through a lot of construction adhesive on this project.

The ceiling is three sheets of 1/4" plywood.  As I'm not planning to hang anything more substantial than lighting from the ceiling, I didn't feel the weight of 1/2" was worth it.  Also, it's hard enough to hang 1/4" solo - I'm not sure I could have hung 1/2" by myself.  It's not the best fit, but I don't spend that much time staring at my ceiling.  I can think of ways to do it better if I ever do this again.

My desk will go in this corner!

Details on installing the plywood walls: Solar Shed: Part 7: Plywooding the Walls

Installing the HVAC

A shed, sitting in the sun on 100 degree days, gets hot.  A shed, in the middle of winter, gets cold.  Even with insulation.

This means I need something to keep it cool in the summer, and warm in the winter.

I found an amazing little unit - a Frigidaire FFRH0822R1.  This fancy little window or through-wall unit is a proper heat pump ("reverse cycle" unit) - not just an air conditioner with some resistive elements.  It can flip some valves and cool the outside while heating the inside.  The advantage?  Doing this requires much less power for heat (at least down to the cutoff temperature).

Since I don't have much in terms of window space, and I have lots of power tools, I installed this unit through my wall.

You'd think that with a hole saw and a reciprocating saw, it would be easy to cut a hole in a wall.  It's not!  It took me nearly half an hour to cut this! 

With the hole cut, I took my trusty sledgehammer and rammed the frame I built into the hole, trimming as needed to make things fit.  And then, of course, screwed it in place.  Because if a little is good, a lot is better!

Installing the air conditioner is easier than it looks.  The inside guts come out entirely!  One mounts the cabinet, then slides the insides into place.

One really cool part of cutting a hole in the wall is getting to see my wall cross section.  I'm very happy with it - everything is very tightly secured but not crushed, and the glue works.  This wall won't come apart easily!

With a bit of foam to seal the edges, the air conditioner is in place and sealed up!  Now I just need a way to power it...

How well does it work?  Nicely!  I can keep it around 70F inside the office when it's about 102F and sunny out.  I consider that entirely reasonable.

More details on the HVAC install: Solar Shed: Part 8: Installing the HVAC

My Solar System

My office is solar powered, because trenching through basalt is no fun.  I'm not sure what to call this other than my "solar system" - which isn't really accurate, because I don't have my own planets.

Solar Panels & Mounts

The process starts with my panels.  They rudely interrupt photons fractions of a millisecond before they hit the ground, and turn them into photos.  I've got eight 285W SolarWorld panels mounted - two strings of 4 panels each, for 2280W of nameplate capacity.  The panels are around 40v open circuit, 31v at peak power, and just over 9A at peak power.

This means my system will hit 160+v on a cold winter morning, and spends a lot of time around 120v, pushing 18A or so into my charge controller.

I built my panel mounts out of wood, because I'm in a very dry environment, and wood lasts long enough.  The mounts are obviously ground mount.  I didn't use my office roof because it slopes to the north.

The first panel mount is mostly built out of 4x4s.  It's really overkill.  As in, the thing is too heavy to easily swing.  However, it's not going anywhere.  The combiner box on the right has three breakers, so I can add another string of panels if I need more power in the winter.

My second generation of panel mounts are lower, built more out of 2x4s, and seem to be just as strong.  There are more anchors into the ground, and a bit more sand weight.  It's much easier to swing, and is much easier to clean.

Charge Controller

After the combiner box, power flows into my MPPT charge controller - a Midnite Classic 200.  This is a really fancy unit that handles getting optimum power out of my panels, and injecting that power into my battery bank.

This controller also handles managing the charge stages for my lead acid batteries - bulk, absorb, and float.  It speaks Modbus over TCP, so I can get realtime data out of it.

Battery Bank

My battery bank, despite the rest of my work with lithium batteries, is lead acid.  Flooded lead acid is cheap, reliable, and easily available on short notice.  I've got a 48v bank, with 12kWh nameplate capacity, though realistically I can't regularly use more than 5-6kWh without affecting cycle life.

I'm using 8 Trojan T-105RE batteries wired in series.  They've got Smart Carbon for better partial state of charge performance, and a bit more electrolyte capacity than the regular golf cart batteries.

A battery bank needs a place to stay - so I found a deck box and assembled it.  $99 at Home Depot.  The box is on the north wall for shade.

Inside the battery box are batteries!  I used 0/2 gauge wire and copper lugs, crimped on, for the interconnects.  The wiring is conservatively rated for around 150A.  Absolute maximum power on my inverter is 6kW, so 120A (for about a second before the inverter cuts off).  Peak solar power is around 2kW, or 40A.  I'm fine.  There's a 250A fuse on the positive side, and a wireless power meter on the negative side (you can see the shunt and circuit board hanging off the top right battery).

Inverter & DC Power Monitoring

My inverter is an Aims Power 2kW Pure Sine Wave unit.  In addition to being a reasonably priced off grid inverter ($700-ish), it has a peak power of 6kW for a second, with various overload intervals for the window between 2kW and 6kW.  A 3kW surge for half a second as a motor starts up isn't a problem for this unit, which is important to me.

The other end of the shunt in the battery box is this console that shows me instant power coming out of the battery bank.  It works surprisingly well!

Input & System State Monitoring

I'm using The Blackbox Project to monitor the overall state of my system.  It runs on my Raspberry Pi 3, gathers data from my charge controller, and graphs it.  This is very useful data for an off grid system - I can see, at a glance, the condition of my system, as well as the history over the course of the day.

Operation of the Power Systems

The power system is entirely overkill for the summer.  I have more power than I know what to do with - to the point that I'm running BOINC and Folding@Home (as SolarSyonyk) to soak excess power, and still can't use all of it.

I can pretty much ignore power on any sunny day, and be fine.  Cloudy days take a tiny bit more work - I may shut down my F@H box a bit early.  Or turn the temperature up (I do like it cold in my office).

The reason I have so much panel hung is for winter power.  Keeping myself online during dark winter days may be a bit of a challenge.  I'll report on how this works once I've gone through a winter.

More details on my solar system: Solar Shed: Part 9: The Solar System

Interior Finish Work

An office is only useful if you can do work in it - so I built a useful interior!

I do a mix of work that requires sitting in a chair at a desk with computers and work that requires a good lab bench - so I built both.

Lab Bench

The lab bench is is set at around 41" high - this seems a good lab bench height for my height, and I'm not doing heavy work on it, only precision work.

The 3/4" plywood surface is secured to the walls with angle brackets screwed into the studs, and I've cut three 2x4s to length to help support the front edge.

Shelves are on both sides, and are designed for light use.  Heavier things will either be under the bench, or on the bench under the shelves.

Fire Extinguisher

I'm not entirely sure why, but during the construction process, lots of people seemed concerned about fire prevention in my shop.  Something about high energy battery pack work, foamboard, and plywood, I think...

Yes, I have a fire extinguisher.  It's a 20lb ABC unit.  The fallback plan, if this doesn't work, is to rapidly exit the office through the door.  At no point in the office am I more than a few seconds from the door, and I have line-of-sight to all points from all points, so I'm not that worried about it.


I installed shelves with a highly technical design spec: "Install them anywhere they fit."  Nobody ever has enough shelf space, especially in a compact office like mine.

The upper shelf is put up with heavy duty shelf hangers screwed into the studs - it's good for quite a few hundred pounds.

The other shelves are all using more standard shelf hangers, and are good for decent but not insane amounts of weight.  They're all secured into the studs as well.

All the shelves are cut from 3/4" plywood, though some of them are cut from plywood that was left in the sun for a few days and had started to curl.


Lighting is still a work in progress, but consists of 12v LED strips stuck to angle aluminum.  The angle aluminum blocks the light from blinding me, offers a smooth surface for the adhesive to stick to, and provides a good heat sink for the LEDs - some LED strips can run quite hot without a heat sink.

All the lighting is "cool white" - this is an office, so I prefer cooler color temperatures in here.  The plywood offers plenty of warmth.

Small Stuff Storage

For small parts storage, I installed a few drawer units on the walls.  They offer drawers for storage, as well as another shallow shelf to put things on.

The taped over battery banks to the right are old BionX battery packs from batteries I've rebuilt for people.  I have plans for them!

Desk Corner

Finally, my desk corner - the core of my office!

The rightmost monitor is wall mounted, and is attached to a Raspberry Pi that is always on for solar system logging and as a general utility box.  It's also capable of waking the other computers in the office, should I need them remotely.

The center two monitors are a 27" iMac and a random 27" Catleap display attached as a second monitor.

The left monitor is for my Windows desktop.  That runs UPS WorldShip, Folding@Home (GPU), BOINC (CPU), and any other Windows-only software I need.  Yes, I have Windows, OS X, and Linux in my office.  I'm too old for OS holy wars.

More photos of my interior buildout: Solar Shed: Part 10: Interior Work


Now for the question everyone is asking: How much did this cost me?

Right around $17,000 plus around 150 hours of my labor.  The solar power system made up around $6k-$7k of that, with the rest being shed costs and build costs.  I probably could have gone cheaper, but I wanted it good and quick, so it's not cheap.

Conveniently, this is also a separate structure built exclusively for business use - so I have that, come tax-time.

Final Thoughts

I've been using this office for a while (my blog posts lagged behind construction by a good bit), and it's working great for me.  I've got plenty of power, plenty of AC (70F on a 102F day), plenty of computers, and plenty of bench space.  I can work in silence (realistically, the whir of my charge controller fans), I can crank the music, or anything in between.  I can Skype, Hangout, take phone calls, and be entirely uninterrupted.

The three weeks to build it were hard work.  I built nearly the entire thing solo - I got some help with the second panel mount, but that was it.  Were I to do it again, I'd borrow a friend for a few days.  Some of the steps would have been radically quicker with multiple people, and if I were to build it again, with what I know now, I think I could do it in under 2 weeks with 2 people.  So, you know, if you want a contractor for a shed-to-office conversion...

I can't say it's fully done - I doubt it will ever be "fully done."  The joy of having my own space like this is that I can tweak it as I want.  I plan to add some filtered air intakes and exhaust vents for soldering fume extraction.  I've got parts on order to power a DC bus for powering lights/monitors/etc without having to run the main inverter - that will let me power the infrastructure (radios, routers, switches, etc) directly from the pack and will get rid of quite a few little power bricks.  I've got two more panels to mount at some point.  And I'm sure I'll find other things I want to do over time.

But, it's up, it's useful, I'm earning money working in it, and I'm incredibly happy with how it turned out!

If you're considering doing something like this, or already have - I'd love to hear about it in the comments!  And if you have ideas for other things I can do - let me know!

And if you're sick of solar shed build posts, don't worry.  Next week, this blog will be back to it's usual business of ripping apart battery packs, analyzing goofy electronics out of China, and doing the math on things that matter.


  1. The fire extinguisher is actually big enough to be useful although dry powder will make a huge mess and potentially ruin any electronics it get's into. I'd also suggest hanging a set of cable cutters on the shed near the battery box in case you need to cut off power in an expedient manner and your switches/fuses are inadequate.

    1. The primary goal with that is to save the structure - I recognize that it will make a big mess and I'll have to replace a lot of bench electronics. Do you have a suggestion for where I could find something that wouldn't make as much of a mess?

      I hadn't thought about cable cutters but that's a really good idea for the north wall. The interconnect loops do lend themselves to being emergency cutoffs.

    2. I'd imagine he's suggesting a CO2 fire extinguisher.

    3. CO2 isn't meant to be used on wood or textiles IIRC, which would be an issue.

    4. I'd suggest ax over cable cutters.

    5. Halotron is a good option to protect your electronics. They don't leave the residue that dry chemical extinguishers like the one it looks like you have there will put out. As was mentioned, dry chemical extinguishers will probably ruin electronics, but Halotron should keep them from getting damaged further by the extinguishing agent. Here is a link to their website if you're interested:

    6. You can still buy Halon, which is MUCH less toxic than the newer "alternates". You can buy it from racing car stores.

      Also, check into for some really good DC fuses (I've built my own electric car and that needs SERIOUS fuses).

    7. If you are going to go with a HALON extinguisher system… Please, please please please, put the trigger for it OUTSIDE of the shed. make sure you (and any other living thing) are outside, and the door is SHUT, when you fire it.

      I used to work for a chemical and hazmat recycler, and they had halon extinguisher systems in the boxes of the trucks. One guy was sweeping out his 15’ box and somehow triggered his. Even with the roll up door wide open, he died before he could exit. They are no joke.

    8. Call the local fire department they will do a check and suggest a appropriate fire extinguisher for your building/electronics etc.

    9. Side note about your normal fire extinguisher. While it will make a mess if there is no power to the electronics when it goes off it will not damage them you will just need a vacuum to clean them out.

      Personal Experience. My two cents is make a master breaker/fuse to your battery back and the intraoffice. flip the breaker to kill the power to all electronics. Then fire the extinguisher.

    10. Side note about your normal fire extinguisher. While it will make a mess if there is no power to the electronics when it goes off it will not damage them you will just need a vacuum to clean them out.

      Personal Experience. My two cents is make a master breaker/fuse to your battery back and the intraoffice. flip the breaker to kill the power to all electronics. Then fire the extinguisher.

    11. Call the local fire department they will do a check and suggest a appropriate fire extinguisher for your building/electronics etc.

    12. If you're working with LiPo and LiIon batteries, in theory what you want is a class D fire extinguisher. The dry chemical will make a mess, but it will be melted by the heat of the battery fire and then (theoretically) starve it of oxygen. However, having been to an extinguisher training at a local FD where we used one to extinguish a LiPo pack that we punctured to set it off, it didn't do a great job. There's a lot of energy in them thar chemicals, and once the reaction gets going, it really wants to just burn itself out.

      Long story short, if you ever have a LiPo pack flame up on you on the bench, just get out of the space and let it burn out. The fume are really bad for you. Call 911 and keep an eye on it from the doorway. Stuff is replaceable, your life and health are not.

  2. From the battery spec sheet:

    "As a rule of thumb, for every 10°C increase in temperature the reaction rate doubles. Thus, a month of operation at 35°C is equivalent in battery life to two months at 25°C. Heat is an enemy of all lead acid batteries, FLA, AGM and gel alike and even small increases in temperature will have a major influence on battery life."

    What's your expected battery life given that it's 37C outside?

    1. Shorter than if it were cooler.

      I rarely see more than 30-32C on the batteries - the thermal mass of lead acid combined with being on the shaded north side helps a lot. I am working on plans to push some conditioned air into the battery box to help cool them in the summer and heat them in the winter, but I haven't gotten that finished yet.

    2. I was going to suggest to dig down a couple feet and place the tub there, but then remembered the rock.

      The other approach would be to just have a "roof" for the batteries with no walls around them for added ventilation. If security is a concern, you can probably surround them with chain link fencing.

    3. You could vent some excess air con into the battery box ?

    4. Phil - yes, I plan to do that eventually.

    5. A hole saw, some laundry vents, and some laundry vent hosing should do the trick well enough.

    6. John - I already have a 2" PVC conduit going into the battery box with nothing in it (intended for airflow). I just need to get an intake on my office before I set up exhaust from it...

    7. You also need to consider the size of venting for the hydrogen gas released during charging. There are minimum vent area calculators available online.

  3. This is one of the cooler things I've seen all year, and I see a lot of cool stuff. Nice work!

    1. Totally agree. This project is way cool.

    2. Totally agree. This project is way cool.

  4. Replace that fire extinguisher with a halon one like this and you won't ruin all your electronics in a fire:

    1. Thanks for the suggestion - I'll look into something like that.

    2. I would suggest an Ansul clean guard fire extinguisher such as this one. The Halon ones have been phased out in most places. The clan guard ones are what I see day to day in data centers as they are mostly harmless to sensitive electronics.

  5. Looks great! the only thing I would of done different is put the rigid foam behind the siding but I live somewhere that gets way below freezing in the winter.

  6. How did you get internet access out there since I assume you didn't trench in fiber :)

    1. Wireless bridge to the house. I've got a pair of Mikrotik Lite2 units up for now.

    2. You might be able to run some cat5 or cat6 if you are close enough. cat5 is rated for 100 meters.

    3. You might be able to run some cat5 or cat6 if you are close enough. cat5 is rated for 100 meters.

  7. What was your total investment? Do you have an expense break down?

    1. It's in the $15k-$17k range - I don't have a full breakdown yet.

    2. Thank you. I see now that you already had that in your post. Sorry. (reading... it works)

  8. Did the structure require and state/local inspection?

    1. No - it's below the 200 sq ft minimum for permits/inspections.

    2. I would have assumed you were outside of any permits/inspections period since you said you were rural.

    3. Sadly, "rural" does not mean "outside of any permits/inspections." I wish it did...

  9. Hey - thanks for taking the time to document the build and share it. Happy shedding!

  10. VERY nice work. The off-grid part is awesome! It's so nice, you might want to dress it up a little by making nicer shelves. Perhaps adjustable shelves or build in some wall-to-wall shelving for a cleaner look. Perhaps a cabinet to store some of the messy things? I am both inspired and jealous.

    1. Gary -

      I don't see myself adjusting shelving any time in the future, so static shelves are fine. There's just not that much vertical space in there. I've been using parts holders to store small stuff, though I'm already out of space...

  11. VERY nice work. The off-grid part is awesome! It's so nice, you might want to dress it up a little by making nicer shelves. Perhaps adjustable shelves or build in some wall-to-wall shelving for a cleaner look. Perhaps a cabinet to store some of the messy things? I am both inspired and jealous.

  12. Great build and thanks for documenting it. You may want to vent your battery box some near the top to prevent build-up of hydrogen gas.

  13. Since you have excess energy available you could run a small vent into the battery box to reduce temp to help increase battery life.

  14. Great Article , thank you for taking the time to write it up and document, I imagine it will help a lot of people over time. Lots of great Ideas there. I want to live off-Grid One day, Oh, I notice how well you insulated the place. cool, Actually make sure you leave a window cracked if you heat with Kerosene, Propane, etc. - Get a C=O=C detector maybe. Thanks again!!

  15. I have an 8X12 Tuffshed. Solar power,but only 300W. max.1,500 pure sign wave go Power inverter.(3)31M AGM's.Shed pulls around 220W all in.One more panel on it's way.
    I made a wind turbine,but took it down. Solar is WAY better.
    Dave in Seattle.

  16. I think if u have internet.. your not off the grid -_-

    1. Off-grid power systems refer to not having mains power available from the power grid.

      Apparently, everyone else thinks off-grid means something else. It's a quite interconnected office, since I work online. So, I use off-grid my way. I really didn't expect so many people to get bent out of shape about my use of off-grid for a solar power system.

    2. I was reading about a guy that used to live down in the coastal mountains of Mexico. He was off-grid, yet he had broadband connection to his house. I agree with Russell that "off-grid" means you are not connected to the power grid.

  17. I think if u have internet.. your not off the grid -_-

  18. " I'd prefer a metal roof, but for a 40% discount I can overlook a few things." Highly recommend investing in a white or aluminium roof. You can put a split seem right over the top of that one - just insure you leave an air gap. But you knew that ;0) Awesome job!

    1. I could, but I'm not sure what I'd gain. My house has a metal roof for fire resistance reasons, but I'm not that concerned about my office. I mow around it. As far as thermal demand go, I can keep it at 70F inside when it's over 100F out, so it's not a problem.

  19. Suggestion on the Fire Extinguisher. 10 lb CO2. Will work for the electrical fires you are afraid of and won't make a mess like dry chemical. Don't get a Halon one. Halon was phased out in 1994 because it destroyed the Ozone layer.
    Some extinguishers might still be available, but if you use it getting it recharged is almost impossible.
    Also, if you buy a CO2 fire extinguisher make sure that it has been tested by a licensed NAFED dealer. The containers need to be hydrotested every 10 years. (The date of the last test is usually stamped on the cylinder like they do with Scuba tanks.)
    (Source- used to work in the industry filling and testing CO2 fire extinguishers. )

  20. Is there enough power generation and storage to work through an 7-8 hour night?

    1. Possibly. I didn't design it for that, though. As long as you kept it below about 500W sustained use, it'd be fine with this pack.

  21. Fantastic build, what exactly do you do in terms of work if I may ask?

    People think off-grid as in living somewhere in the salt flats or something. It's neat that you can technically just move this shed somewhere else and it'll still work (granted, you'd use satellite internet).

    You seem to have done your homework on most of the installation process/solar panel setup/etc. You say you remade a few batteries, for some reason I just get the vibe that you're an electrical engineer or sorts, am I close?

    1. I do a range of things - generic tech work/web backend stuff, sysadmin, battery pack rebuilds (look around my blog for examples of this). I've been attempting to make a bit on blogging as well, with device teardowns and analysis.

  22. Great work, this is really cool!

    -I play with high energy battery packs. A 500Wh pack shorting out is very exciting - I want a separate space for this.

    Best part of the article.

  23. Great work, this is really cool!

    -I play with high energy battery packs. A 500Wh pack shorting out is very exciting - I want a separate space for this.

    Best part of the article.

  24. Very nice build! A little off topic but I couldn't help but wonder what kind of internet connection are you getting out in that rural environment?

  25. Nice job. You may want to consider some sort of flashing around the hole you cut for the ac; you don't want water or moisture sneaking into the walls from the outside. Cheers.

  26. I'm curious why you didn't off-grid the house and run a cable up to the shoffice. You could still do this given the setup. I can see having a reliable power supply in mid-winter to be key to use.

    One thing I did when I built my shoffice was to install a tiny wood burner (with ventilation + monoxide detector). It removed the biggest power expense.

    1. Basalt. The problems with trenching through it.

    2. Russell, did you consider burning wood for winter heat? A wood burning stove would take up a lot of space, though.

    3. I considered it, and I have literally no free space in here. I might be able to put in a little ammo box stove or something, but there's still no good spot for it.

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  28. Great project. You might consider solar thermal panels for heat. Easy diy project, very efficient

  29. This is a fantastic idea. Love it. Good inspiration for me to consider as my house can feel a bit tight with a dedicated office.

    I don't quite have the solar/electronic chops as you, but in my situation it would not be difficult to run a dedicated line to the shed and possibly fab in solar later as I learn more.

    1. If you can run a dedicated line, do that. It'll be cheaper and less of a pain to deal with. My system is fine, but I do have to pay attention to energy.

  30. My brother in-law and I built a finished out shed for me to use as an (on-grid) office, he suggested adding a radiant barrier on the ceiling before sheetrock because there was no attic space. We also insulated under the floor. Installed 2 windows for those days were no AC or heater was needed. The one thing that I did not anticipate was the noise from the air conditioner while on meetings, I might have been able to hear ok but people on the other end complained about background noise. I ended up having to turn it off for phone calls, which got hot sometimes. Worked remotely in the shed for 2 years before changing jobs. It was great and my wife and kids knew if I was in the shed I was "at work".

    1. Sounds similar - very cool! Yes, the AC noise can be a problem for phone calls.

  31. If you wanted it to be mobile you could roof mount the solar panels and put the whole thing on some kind of trailer. (Assuming you could figure out some sort of leveling/stabilizing jacks.) Not sure exactly why you'd want to do that but it seemed like the natural next step with not being tethered to power.

    1. I could, but I have no real desire to do that...

  32. Interesting build. IMHO, for the money spent you'd have been much better off to use a quality mini-split unit for HVAC. Way, way more efficient - as much as 22 SEER or better - and much quieter. I've owned one of those Frigidaire units and hope your experience is not like mine, otherwise you're going to be sorry you cut a hole in a perfectly good wall and glued that POS in there.

    1. Fortunately, if I need to replace it, I can swap it out quickly. :)

      I'll see. I couldn't find a mini split that was suited to my size of office or installation ability.

  33. Came here via a Brent Ozar link and it was really great seeing your man cave built in stages. Would love to do this myself but living in the UK, we don't get much sun! ;o) Thanks for sharing, what a brilliant office set up.

    1. Yes, but I don't believe most of the ground in the UK is filled with large rocks. Just trench power if you can.

  34. If you need some air exchange look into an HRV or ERV depending on your climate. They will give you fresh air while recovering ~70% of the energy you spent for your cool or warm indoor air.

  35. Hi Russell,
    I like the end product. Have you considered at any point using the shipping containers turned houses/workshops? I'm quite sure that one (used) with a prebuilt isolation could be found for under 10k$.

  36. I really like this project and the way it turned out. My wife and I will be shopping for a house over the next year and we're going to keep a office shed like this in mind as a possibility in case we like a house with just not quite enough space. The ability to isolate work space from living space might be enough reason to undertake such a project on its own. I am a bit surprised that the cost was about $10k excluding solar. What were the top costs in that area?

    1. Insulation, plywood, and screws are expensive. Plus the interior finishing work I've done with shelving/storage boxes/etc add up.

      If you're going to grid tie it, you could go a lot cheaper since you won't need quite as much insulation.

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  38. Sweet job. 2 ideas: 1, quick-removal system. Have a trap door system like the drawer used in drive up banking, for the hazardous stuff... screwups get ejected to the outside, with power disconnecting as the drawer moves thru the wall, and 2, like the man said, at least one manual disconnect at the battery box, consisting of a hearty tree stump with the power source cables laying across it, and a nice paul bunyan axe hanging close.

    For the quick removal system, maybe even shoot the drawer many feet away from the office on tracks, sorta like a coal miners trolley? get sophisticated and use rail gun power to git er gone?
    Seems better than burning down the outhouse or coating it with slime to put out the fire.

    Good luck, tom

  39. Understand why you went solar, but maybe you could evaluate the system a bit further. I'd like to do this too, but I don't have to, so the money balance is important to me.
    So, you spent some dollars on equipment, but what's the life expectancy of it? 6K might be affordable initially, but what's the cost to keep things running long term? 5 years? 10 years or more? Batteries need replacing, electrical components have warranty expo dates etc.

    Electricity costs about 10cent per kwh. How long to recoup your investment etc.?
    Be interested in how you'd look at it if you didn't Have to use solar.
    thanks, tom

    1. If you can use grid, use grid. This is not cheaper than grid - I did it because I can't easily trench grid out to my office. Also, because I find it interesting and have wanted an off grid system to play with for years so I can learn it. It's not about saving money, and I don't expect it to save me money (other than "not having to pay someone to trench through basalt").

      Life expectancy on the solar panels is 30+ years. They simply produce less power as they age, but unless they physically fail, they'll keep producing power many years into the future.

      The charge controller and inverter? No idea. Hopefully a long time. They're around $600/ea to replace.

      As far as the batteries, my batteries are deep cycle flooded lead acid, designed for renewable energy use. According to Trojan's charts, if I run them at a 20% DoD they're good for 4000 cycles, with around 2700 at 30%. I generally don't drain them terribly low - I've got more panels than I really need, so they spend most of their time full. And I have a backup generator for deep winter conditions. That's 10+ years on them if they meet expectations, and by that point, I'll probably have replaced them with a mass of worn ebike batteries, since I seem to accumulate those at a rapid pace.

  40. I'm doing this from my smartphone using the microphone Because my fat fingers don't fit on the tiny screen very well so excuse me if stuff seems weird.I'm doing this from my smartphone using the microphone because my fat fingers don't fit on the tiny screen very well so excuse me if stuff seems weird. I have a question about daily operations of your neat little box house. Do you run the air conditioner 24 7 or do you only run it while you are actually working there. Next question if you run it only when you're working there can you give us an idea of the internal temperature when you arrive and how long it takes for your AC to bring the internal room temperature down to where you want it to be. Also how many be to use is that AC and how many amps does it your all. Running your typical load why you are working there approximately how many AC amps are you drawing. Thanks for your help I really enjoy your project Tom

    1. The AC runs while I'm in there, and is left at a high setting on econ mode when I'm not - typically 80F. That way, things don't get too hot in the evening, but it doesn't spend a lot of power trying to keep it cool when I am not out there.

      The AC can bring the office temperature down slowly (1F every 5-10 minutes) if I have all the compute loads going on a hot day, or much more rapidly with less power being used. I also can open the windows and door if it's cool to help vent the office and cool it down.

      As far as power use, the AC uses around 750W when operating.


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