Well today is the truck's official second birthday, and there's a lot to be said... But I think I'll just start out with why...
It's also the line in the sand where all of this was originally supposed to end.
The idea with 2 years was simple; It would allow, one way or the other, the viability of this to be proven. 1 year would have meant plausible, 2 is undeniable, regardless of outcome.
It isn't over exactly, in the sense that things will be status quo for a while longer, but having now reached this line, I can officially declare it's status.
I'm going to go with "technologically a success, but a bit of a reach for practical".
I've learned a great many things in the course of conceiving, building, living in, modifying, and otherwise making it become what it is as of this moment... Not only about all the physics and what it takes to battle nature's offerings, but also about myself and what some of my more notable limits are, among other things.
It's been a lot of fun, and a lot of work, both, and demonstrates that it's possible to do something like this, even tho it falls short on a few levels. There's a strange relationship between us, having been a direct brainfart of my own creation. In a lot of abstract ways, it's become my best friend. Likewise, and just as importantly, an arch nemesis. And everything in between. It has a personality, for sure, and being somewhat computer controlled... even thinks like me.
So what are some of the things I've discovered on this adventure?
The hardest part by far, generally speaking, would be energy management. This is largely due to the lack of abundant rooftop real estate on something this size. At around 136 sqft, there's not a whole lot to be had, and at times, it can get spread pretty thin. There's 800W (label) worth of PV up there, and after losses and age of the panels (they were used when I got them), I typically see a peak around the 600W mark on an "ideal day". There was also never any plan to do any thermal up there, for a couple reasons, but the main one being that there simply wasn't any room.
A lot of the energy that gets made is spent on managing the inside environment thermally... Fans in both winter and summer, just for starters. Moving air takes a surprising amount of energy, even when done efficiently. This is largely because it adds up; they can be considered part of the base load because they run just about full time toward and during the extremes of the seasons.
Later on, I also added a small air conditioner, as well as some "wax stabilized" resistive heating. In summer, there is plenty of power available, until the air comes into play; the PV can barely break even with it for just a few hours a day near solstice. This was known prior to the build, and as such, was ruled out as even a possibility, until I discovered a relatively efficient 5k window unit. It largely finds use in managing humidity when I'm running on pure PV. Even the genset can't really sustain it very well due to its age, but does get used to assist the PV to help make things comfortable.
And while the (electric) heater isn't much more than trivial (~36W max, it's very targeted), it too strains the system in winter because the light is so short.
The main heat source is a heavily modified catalytic propane heater that's designed to trap as much of its infrared for its own use as possible, and convert the resultant output into convection. The primary reason for this was for efficiency and to facilitate clean combustion with a much lower gas flow to the catalyst. Basically, it reflects a lot of the IR back at the catalyst, causing it to run hotter for a given input, allowing the valve to be closed much further, without producing monoxide. Don't try this at home
Spring is by far the easiest, as the temperatures are modest, and light becomes more and more plentiful. This is the only time of year that could be considered to have a "surplus" of energy if there really is a such thing. Running the laptop for extended periods on a sunny day at this point becomes much easier, and productivity in general goes up significantly.
Late summer into early fall is the hardest because the sun starts to fall into the trees, which still have leaves on them at that point. Cooling is much more energy intensive than heating is, so the system in general struggles to make ends meet this time of year.
Refrigeration is possible for the majority of the year, albeit a little less controlled in the winter due to the shorter light supply. I use the outside a fair amount to make up the difference, but of course I have to be diligent with perishables because of temp fluctuations. In the summer, because of limitations in the overall design, the fridge also creates a lot of extra heat that I have to get rid of in some way. In the cooler months with more adequate light, this works in my favor, but in summer, can make things very uncomfortable.
There is a microwave for cooking food, although it had to be an "inverter" type, to limit the amount of current the batteries needed to supply. I normally only run it at power level 3, which works out to about 600W of input. It's a little slower than full throttle of course, but can get there in a reasonable time, so it works.
There is no running water, for a multitude of reasons, but the biggest two are that A, there isn't really room to have all of the things I wanted to do, and have everything that water would have required. B is simple as well, I didn't want to deal with all the issues and implications that having it on board would have meant. This does of course complicate things, but since it was decided from the beginning that there would be none, other provisions were made to deal with some aspects. The others got refined as time went on. In a nutshell, a Y membership covers the showers etc, and a couple of systems for handling waste came to be. In all, again, not necessarily the most practical, but doable with minimal fuss, and more importantly, safe.
Storage also has proven to be an issue, but then again, when is it not... lol
The sleeping arrangement is set up for seasonal, with a murphy style bed for summer that folds down to right at the floor line underneath the "ceiling fan", with the "attic" being used for storage. In winter, the bed goes up against the wall, and the space in front of it used for storage, and the mattress gets moved to the attic. This allows me to curtain off a small space, up high, and trap heat efficiently. It is also where the above mentioned resistive heat is; imagine a "crock pot sized electric dog" at the foot of the bed...
Ventilation was also a tricky thing given all of the concepts that had to be considered both originally and as time went on. I planned in the beginning for a much more stealth approach to the whole design, to facilitate the original travel plans. This didn't work out for a number of reasons, but one of them was because of the needs that thermal management posed. The system originally was only going to use two 4" tubes, one intake, one exhaust. In winter this may have even been possible, had it not been for getting spooked by a freeze that bound the big door up (ok down, actually lol), and in summer, I have to move a LOT more air. So the back stays open when I'm stationary. So much for stealth.
That said, due to other limitations such as ability to fabricate and modify various aspects to make changes, I had to get whimsical to turn it into something that could handle all the seasons. What it comes down to is a bidirectional system that pulls air in along the floor and exhausts high in summer, and the opposite in winter. The winter mode is much more effective because it now exploits natural convection much more efficiently thanks to the increased inside/outside deltas. Fresh air is pulled in from the ceiling gap (from along the big door), which helps reduce heat loss thru the roof, and a complementary fan simultaneously pulls the cold air out at the floor line and exhausts it. The result is that the much cooler intake air gets mixed before it has a chance to fall naturally (by the ceiling fan, which does regulation duty in winter). The other drafts, along with the then cooled air from the rest of the room are sucked out before they can build a "hard layer" at the floor.
There are a couple of drawbacks to this design, but it was the best compromise I could come up with given what was at hand. The main drawbacks being that A, it doesn't always completely prevent condensation at the roof line (tho does drastically reduce it). And B, below a certain point, if the fans begin to throttle back too far to try and maintain the ceiling line temp, it can lose its "grip" and the cold layer can still form and build up.
The latter isn't always an actual drawback; it depends on what I'm trying to do. At night, it's pretty much inconsequential, and actually acts somewhat to increase the overall heating efficiency naturally (I don't need to increase the gas flow to maintain the ceiling line temps because the lower part of the box isn't losing as much heat thru delta conduction to the outside). During the day however, when feet are on the floor, this can obviously make for some uncomfortable conditions. Given what I had to work with tho, it works surprisingly well, all things considered.
There are countless other things that could be covered here, but I think I'll cap this particular post with quite possibly the most important aspect of all this...
It's been an interesting journey, and I don't regret doing any of it, although it certainly has had its moments. I would encourage anyone that's considered something like this to give it a shot and see what comes out of it, as one will learn all kinds of unexpected things in the process. It will test your understanding of just about every aspect of life, and will demonstrate both under and over estimations in what you thought you might be capable of (there are plenty of both to be had), and if you take it to some of the extremes I have, it'll put your physical, mental, spiritual, and every other "-al" you have to the ultimate test.
Which leads me to my last thought before I let this go out into the wild...
It's certainly rewarding to have set a goal of this size and seen it to completion in terms of intent and a date and such... But be warned, it's very stressful in the form I've done it in, and I've noticed a significant acceleration in my aging during this time frame. It would have been much better to do as a much younger being, but then again, I wouldn't have had a clue back then where to even begin, so it's a wash. Call it something of a life's dream of sorts, but it did come at a price.
I still don't regret it however, and my most sincere thanks goes out to all that have helped out along the way. There are so many of you, and in so many different ways, that I simply can't list everyone and everything without feeling like I'd leave someone out somehow. But you know who you are, and I do as well, and it wouldn't have been possible without you!
Steve
[PS... So *now* what... lol]