Solar Tracker Experiment

Several months ago, when I first posted about my manual two-axis solar tracker, a couple of readers asked whether a tracker really made that big of a difference. I had a theoretical answer based on simple trigonometry and the amount of light that falls on a surface relative to its orientation to the sun. Specifically, the amount of direct sunlight that falls on a square surface should be proportional to cosine(θ) x cosine(γ) where θ and γ are the angles between where the panel is pointed and where the sun is, in the x and y axes. By this theory, a panel that is perfectly aligned in one axis, but off by 30 degrees in the other axis would only get about 86.6% as much direct light. (This formula ignores ambient light, which in reality would clearly be present in addition to direct sunlight.) But I had no empirical data to back up my theory… until today.

On a sunny day like today, I’d re-orient my 100W solar panel 2 to 3 times in the course of the day. I usually point the panel to the east before going to bed so that it’ll catch the morning rays, and I’ll move it to point due-south later in the morning. In the afternoon, I might move it one or two times as well. The general idea is to keep the panel pointed to within about 20 degrees of the sun, since that should give me over 94% of available light at all times.

Today, when I went to re-orient the panel a little after 3pm, I decided to get a couple of actual readings. I first checked the voltage of the whole system (charge controllers hooked up to battery array), and got 13.3 Volts. I then measured the current between the charge controller and battery array, with the solar panel in the noon position, and also in its optimal position at the time, which is about 45 degrees from the noon position. With the panel in the “noon position”, I got 3.85Amps, or 51.2 Watts. I then moved it to the 3pm position, and got 5.55Amps, or 73.82 Watts.

The verdict, I might say, is that yes, the tracker makes a significant difference. If the panel had been fixed pointing due south, by 3pm I would only be getting less than 70% of the power that I could be getting, and that number would rapidly diminish as the sun continued moving away. This would also be the case in the morning, when I would get significantly less power than is available for the first few hours of sunlight. And, as it turns out, the numbers fit my theoretical model fairly closely, since according to my theory, my panel should be outputting 70.07% of its maximum when pointed 45 degrees away, while the actual numbers I got today were 69.37% (also, the angular difference was approximate, though, in theory, the sun should move by 45 degrees between noon and 3pm).

One thing to note, however, is that these results were obtained with my monocrystalline panel, which work best in direct sunlight. Thin-film panels, including amorhpous silicone panels, supposedly get more power from ambient light, so they may be less sensitive to orientation, though this is another hypothesis I’ll need to test with my 45Watt amorphous panels sometime.

Another question I got about the tracker was the effectiveness of the “manual” nature of the tracker. Wouldn’t an automatic tracker that constantly aligned the panel with the sun be more effective? Well, yes. But, to get 90% of available energy, the panel can be off by as much as 25 degrees in one axis (arccosine(0.9)). Or, at any given time, if I point the tracker 25 degrees ahead of where the sun actually is, the sun could move through a 50 degree arc and I would still be getting over 90% the whole time. Since it takes the sun over 3 hours to arc through 50 degrees, even manually moving a tracker every 3 hours will ensure that my panel gets 90-100% of available light at all times. So, an automatic tracker with all its complexity only gets maybe 5% more power than a manual tracker that’s re-oriented every 3 hours.

Journal: February 25th, 2011

I woke up to about a foot of snow this morning; I’d finally gotten that snow storm I’d been hoping for. I have a lot of things outside that I use on a regular basis, like my ice chest, the solar panels, the toilet, and everything had to be dug out before use. Oh, yeah, including toilet paper (which I leave next to the toilet in a ziplock bag). I made myself some banana pancakes for breakfast, and then decided to spend the day frolicking in the snow. Except, there was one problem. I have this nice pair of Sorel snow boots that a reader donated to me (thanks Ed!), but the snow was so deep, even just around my camp, that snow would get in from the top of the boots. Obviously, that’s what gaiters are for, except, I don’t have any. So, I decided to make some! I grabbed a couple of plastic shopping bags, cut one of the handle-loops off each bag, cut a hole in the bottom of the bags, then stuck my booted legs through the bottom holes, and stuck each foot in the remaining handle-loops (to keep the gaiters from hitching up). Then I wrapped some duct tape around the ankles and above the boots, and voila! Ghetto gaiters! I’m proud to say, despite barreling through thigh-deep snow drifts, hardly any snow got into my boots. Unfortunately, the gaiters proved to be only good for one-time use, since I had to cut through the duct tape to get them off… But, I’ve got plenty more plastic bags, if needed.

Later in the afternoon, in a bout of unusual productivity, I finished the rest of the work on the floor. The temperature is supposed to drop down to the single digits (-13C or below) tomorrow, so having an insulated floor will certainly be nice. In fact, it’s about 15F (-9C) tonight, but it’s about 65F up in the loft, and warm enough downstairs that I’m just wearing a t-shirt and a thin hoodie. I’m pretty sure that, when the floor was uninsulated, I had to keep the stove burning a lot hotter to keep the inside temperature 50F above outside temperatures, and it was certainly much colder downstairs. Now, I can even sit on the floor without freezing my butt off. Yay insulation.

A couple of readers pointed out that the way I decided to do my raised floor would be suboptimal, due to thermal bridging. This is indeed true. Those 2x4s will conduct heat out through the original floor, somewhat degrading my floor’s insulation. On the other hand, one of the reasons I decided to do what I did, was because I wanted to try using recycled cellulose insulation instead of polyisocynurate or polystyrene rigid insulation boards. Recycled cellulose, I think, is much more environmentally friendly, not just in terms of the environmental impact during production, but also when it comes time for disposal.

When it comes to houses, most people think about the cost of construction/production, as well as costs incurred while living in it (in terms of heating, air conditioning, and perhaps maintenance). But, people rarely talk about deconstruction, probably because most people expect to be out-lived by their houses, and therefore never really need to deal with the inevitable demise of their dwellings.

In my case, however, Hut 2.1 has an intended service life of 5 years, and is explicitly not designed to last long. There are a couple of reasons for such a short lifespan. First, and foremost, Hut 2.1 is as much an experiment and learning exercise as it is a home. I assumed from the beginning that it would be far from perfect, and therefore, that I would likely be building its replacement in the near future. Secondly, I consider this property itself to be an experiment. Once I’ve learned what I could learn from it, it’s conceivable that I’ll want to sell it, and buy property elsewhere. And if I were to sell this property, I may need to get rid of my structures because, let’s face it, most people don’t want tiny huts — at least, not these huts. (And since someone will inevitable suggest that perhaps I should’ve built something that other people would want, I’ll respond by saying that, building something other people would want instead of what I want defies the whole purpose of building your own home.)

So, even while designing and building my Huts, I’ve been thinking about demolition at the same time, and have concluded that using organic combustible materials as much as possible would simplify this issue. The plan, basically, is to remove any materials that can be reused (windows, for instance), and then to burn the rest. The less plastic there is, the less toxic fumes will be released during combustion. In the case of Hut 2.1, I’ll probably remove the roofing and strip off the exterior polyiso insulation before torching it, and the rest is basically just wood (including the “cellulose” insulation I just put in my floors) and a marginal quantity of unnatural materials like Tyvek and spray-foam insulation. This is also the reason I’ve avoided fiberglass; that stuff doesn’t burn and takes a long time to degrade, while I don’t want to leave behind anything that isn’t bio- (or naturally) degradable.

Journal: February 23rd, 2011

I had a pretty productive day today. It was another gorgeous clear day, and I decided to finally set up my “back-up” 45W solar panels to catch some rays while I can. Even though I could probably continue to get by on just my 100W panel, with another storm headed my way, I decided that if the weather forced me to spend more time indoors (while generally giving me less power), I might as well have a little extra capacity. I’ve seen my 100W panel output (as measured between the charge controller and battery array) as much as 80Watts, and the new 45W array was producing just shy of 40W today, so, combined, I should be able to generate as much as 120W. Though, the bigger question is how much they’d generate on a cloudy day, and that, I have yet to measure.

After I got the solar panels set up, I went and cut more firewood to shore up my stockpiles in preparation for the “arctic” temperatures predicted this weekend. I’ve been using my cordless reciprocating saw to chop dead mountain mahogany trees into short logs that’ll fit into my tiny stove. Even though there’s plenty of wood lying around, using the battery-powered saw is a suboptimal solution because it wears out the batteries, and batteries are expensive. Not too long ago, I used to be able to get a load of wood on a single charge, but the batteries are getting worn, and I’m losing power much faster now. At this rate, I’d be surprised if a set of batteries last through a single winter, and replacing batteries every year could cost about $100. It’s still cheaper than buying firewood (not to mention, firewood that’s being sold wouldn’t even fit in my tiny stove), but I’ll probably want to find an alternative if I plan on spending more winters here. An easy alternative is to get a gas-powered chainsaw, but a more environmentally friendly solution might be to use a wired saw. I could use a cordless saw to harvest long sections of branches, then chop them up back at camp where I could use a plug-in saw that’s powered by my larger battery array. Of course, using a manual saw would be the most environmentally friendly option, but I’m afraid that’s more work than I’m willing to put in, if alternatives are available.

Later in the evening, I finally got some work done on the raised floor inside Hut 2.1. One half of the floor is done, but I’ve been dragging my butt on the other half. Today, I finally mustered the motivation to work on the other half, mostly because of the predicted weather. I got as far as laying down the 2×4 joists on top of the existing floor (see photo below), but the 2x4s are a bit wet, so I’m going to let them dry out for a day or two before continuing. The next step is to fill in the gaps with insulation, then cover the whole thing with Tyvek, then the flooring goes on top of that. All in all, that’s probably just a few hours’ worth of work, so I’ll get it done fairly soon. Once the floor’s done, I’ll start working on furnishings, like a desk, a sink, and a kitchen counter to put the gas stove on. I haven’t yet decided on where to put the bathroom (there are two possible locations), but that’ll happen at some point, assuming Spring doesn’t come first. So far, I’ve just been using my outdoor composting toilet, and it’s working out fine for me. It gets a little cold sometimes, but the fresh air and nice view make up for it, if you ask me.

Journal: February 21, 2011

The last couple of days have been fairly uneventful. The weather wasn’t great yesterday, so I spent most of the day on my computer working on my software project. I finally got out for a bit around dusk and went for a little walk. Today, I went for a walk in the afternoon, and came upon a cluster of nice (dead, but mostly still upright so free of snow) mountain mahogany trees, so I went back to camp, picked up my saw and a pack to go collect some firewood. As I was heading back to the trees, a startled jackrabbit ran off from a nearby bush. I instinctively reached for my gun, but quickly realized that what I had cradled in my arms was my cordless reciprocating saw — hardly the right tool for hunting rabbits.

I noticed that half a bag of potatoes I’d left in Hut 1.0 overnight for one night had started to go bad. I guess they froze during that one night spent in Hut 1.0, then thawed after I moved them to Hut 2.1 and started to rot. I boiled some of the worst ones over the stove last night, and fried them up for breakfast this morning. They tasted a little dry, but were otherwise edible. I’m currently making potato and leek soup with the rest of the potatoes that might’ve gone bad. I still have the other half of the bag that I’d stored in Hut 2.1 to start with, which are fine and should last a while. I also have a couple of pounds of sweet potatoes, so I’m pretty good in the potato department. Otherwise in the food department, the pot of curry I made last week lasted me 4 dinners, and I had the last of it last night. I’ve also discovered that making pancake batter in a ziplock bag works great. It spares me the trouble (and water) of cleaning a bowl, and I can throw the unused portions in the cooler.

My electricity supply is being constrained somewhat by the overcast weather. I used a lot of power yesterday when I spent the better part of the afternoon and evening on my computer, which, combined with the overcast weather today, put me in a slight energy deficit (i.e. I’ve used more power than I’ve generated). My battery array is still above 12 Volts so I’ve got plenty of power, but I decided to spend the evening with the lights off today to conserve power. I’m still just using the single 100W panel, and haven’t set up the new 45W panels yet. I figure if I could get by with less, I might as well.

It looks like more snow and colder temperatures are predicted for later this week. I’ll probably go gather some more firewood tomorrow, just to shore up my stockpile, even though I think I have enough to last me at least another 2-3 weeks. I’m actually quite happy about the snow. In my ideal world, it’s either snowy or sunny, but never rainy. Now that I think of it, that’s kinda how it’s been up here.

Overall, things are going surprisingly well. I haven’t yet faced any major issues as I enter my second week of my continuous stay here, and I’m enjoying each day, even if I’m not being as productive as I perhaps could be… My floor is still half unfinished, but I’m sure I’ll work up the motivation to finish it one of these days. After all, I’m not in any particular hurry. But, other than that, I’ve got plenty of food, plenty of water, and so far, plenty of firewood to stay warm. So, basically all my needs are met, and I have no concerns there.

I guess the one thing that’s worth noting is that I’m still adjusting to having internet access up here. It’s certainly a mixed blessing, though it hasn’t been as detrimental to my life here as I feared it may be. Though, I still spend more time on the computer, and less time reading or simply pondering than I used to. It’s not necessarily bad, but different. But then, a lot of things have changed in the year and half that I’ve been on this property. I used to live in a tent, without decent electrical lighting, without internet, without cell phone access, without heating. It’s hard to say that things are worse, but it seems that something is lost every time I add a new convenience or comfort. But, that’s what this journey is about. It’s about finding that right balance for myself, and it’s an on-going process.

Pondering the State of Nature… in Nature

The weather was beautiful this afternoon, so I went on a long-ish walk. I headed north up the clearing in front of my camp, where, just beyond visible range of my cabin, I found dozens of deer tracks, coming and going from every which way. It almost seemed like they’d gathered for a little cocktail party, or perhaps a protest of some sort, as those seem to be in vogue these days.

There’s this steep ravine that cuts across my property, west to east, that splits my property roughly into two-thirds and one-thirds. My camp is on the one-third side, and since I rarely cross that ravine, I’m generally confined to a relatively smaller portion of my property, and there are acres and acres that I probably haven’t even seen yet.

Today, as I was walking down the ravine, I noticed a rock cropping up on the north-side (the less visited side), so I clambered up the steep slope to see what I could see. As I reached the top, a frightened flock of birds beat a hasty retreat. When I said “beat”, I meant that quite literally, as the flapping of their wings reverberated through the crisp air like a dozen drums.

I didn’t get a good look at the birds, but the awkwardly loud and hectic flapping suggested that these birds were pretty big, and also not entirely accustomed to this “flying” thing they were attempting. Though I know little about fowl, I somehow imagined that these birds might make for good eating. If they’re sticking around this time of year, they must have a nice layer of fat to keep them warm, or so I imagined, and I could almost taste sizzling fat and juicy bird flesh on my palate (though, on second thought, I realized I was remembering the Peking Duck I had in Beijing last summer…).

As I had my shotgun with me, it occurred to me that I could try to hunt these birds. Though, I quickly realized that it would probably be illegal to do so, this being California where hunting seems quite heavily regulated. Besides which, I didn’t know what kind of bird I’d be shooting at, so there was no way to know what kind of regulations even applied. So, it seemed safe to assume that it’d be illegal.

Standing there among the snow and trees, I contemplated the incongruity of these two realities I faced. On the one hand, there I was in the middle of nowhere. I had a shotgun, conveniently loaded with birdshot. Beyond those bushes were birds that sounded tasty. I was hungry. Shooting those birds seemed like the most rational thing I could do. Yet, I had to contend with the other reality, which lay beyond my property borders. Those birds, though presently on my land, are legally property of the people of California, and therefore regulated (most likely) by the California Department of Fish and Game.

So, I turned around, and trudged off feeling somewhat defeated; a man living in the woods, who can’t hunt. I might as well have been a wolf without fangs, or a mountain lion without claws. While this seemed absurd, it occurred to me that we muzzle dogs and declaw cats. We’ve domesticated ourselves as much as we’ve domesticated wolves into dogs and lions into cats. To be a modern human, as it turns out, is to be something not quite human. It’s almost as if we’re not good enough to be, well, us.

Modern humans, it seems to me, are an oddly self-defying and self-denying species. We find ways to feel guilty about everything, and this seems particularly true of Americans. We’re guilty about food, and we’re guilty about sex — two things a species can’t do without. We even find ways to feel guilty about drinking water. And while some may point at our country’s Puritan roots, this belief that we somehow can’t be trusted can be traced to early political philosophers who influenced the rise of modern governments, including our own. The 17th century philosopher, Thomas Hobbes, argued that the State of Nature for man was one of perpetual conflict, and famously described life in such a state as “solitary, poor, nasty, brutish and short.” He then argued that a better life could only be possible in a civil society, one in which we must cede our rights for the sake of peace.

If I recall Hobbes correctly from my college readings, he argues that, by nature, we are in a state of constant war because each individual acts to serve their own interests only. In other words, in the State of Nature, I would shoot that bird because I want to eat it. Conflicts arise if others also want that bird, and when two guys with shotguns fight over a bird, well, at least one of their lives could indeed end up nasty, brutish, and short. And even if nobody was there to fight me over that specific bird, humans have hunted animals into extinction, including on this very continent. We all know about the White Man killing off the plains buffalo, but less well known is the strong possibility that Native Americans (or their ancestors) drove other large tasty fuzzy animals (like the wooly mammoth) into extinction many thousands of years before those Puritans showed up in their funny hats and giant belt buckles. I don’t know about others, but I wish we still had mammoths. And if the California Department of Fish and Game (and Large Fuzzy Animals) had been around 15,000 years ago, it may very well be that we’d actually still have mammoths, and saber tooth tigers and North American lions, and other such wonderful beasts. So, perhaps Hobbes does have a point after all.

There are people in our country today who want a smaller government, fewer regulations, and less intrusion. As I stood there today with my shotgun in hand, I wished I could simply shoot whatever I wanted, when I wanted. But, if we are to deserve such a society, that is, a society that is slightly closer to the State of Nature, then we must prove Hobbes wrong. If we are to cede fewer rights and still get along with each other and our environment, we must each act responsibly and intelligently. If we don’t want the Department of No You Can’t to regulate us, we must regulate ourselves, and act not only out of our own self interest, but also in the interest of our fellow man and our future generations.

The question is, can we?

Day 2

I’m pretty tired, so this’ll probably be a short post…

Had another late-ish start today, mostly on the account of having trouble getting out of my nice warm bed to brave the crisp air. Eventually, the combined realization that 1) it was sunny out, and 2) my solar panel was pointed in the wrong direction, got me out of bed in a hurry. I had my usual eggs, greens, and tortillas for breakfast. The eggs were the last of the dozen I’d bought in January, and were fine despite being 3 weeks old, and having been left in freezing temperatures. The tortillas, however, had frozen, but other than a few at the top having frozen in weird shapes, they tasted fine.

I spent the early afternoon gathering more snow, and collecting some twigs and branches that I use for kindling. Before starting Project 31, I had 2 buckets filled with kindling, but already burnt through one. Since the sun had dried out some branches, I decided to fill up that bucket again, so I still have the other bucket. I also have a large pile of branches under a tarp, if dry branches aren’t otherwise available.

Later in the afternoon, it started snowing again, so I worked some more on the hut floor while listening to music. At this point, half the floor is done and insulated. The raised floor feels much, much more solid than the original floor, partially because the joists on the raised floor are spaced closer together and are laid perpendicular to the original joists to spread the load, but also because the OSB is oriented in the right way (after all, the “O” in “OSB” stands for Oriented). I still need to do the other half, though it’s more like 3/4 of the half since the area near the door will not be raised. The lowered floor near the entrance is a standard feature in Japanese houses, where you’re expected to take off your shoes. Your shoes stay in the lowered area near the door, and the height difference also helps keep mud and dirt out of the rest of the residence – a feature I intend to take advantage of in Hut 2.1.

In general, I’m feeling good. Even though this is Day 2, I got here on Monday, so I’ve been here 4 full days now, and I’m settling in. It’s nice to have everything I need here, and not have to worry about going into town, or the roads not being clear (seeing how they haven’t been anyhow). There’s also a certain peace of mind in being committed to staying here. I get emails about things happening in the city, and normally, there’d be a pang of doubt: a part of me would wonder if I might have a better time there than here. But, now, there isn’t. I simply file away those emails, because I am here, not there.

29 more days to go.

Day 1

I guess this is technically the second day, but since yesterday was Day Zero, today would be Day 1. The idea is that I can leave on Day 31, while if I’d started counting at 1, it wouldn’t be 31 full days until Day 32. Though, I’m sure in a few days it won’t make a huge difference either way.

Let’s see. I didn’t accomplish a whole lot during the day today. I got a late start, so instead of cooking breakfast, I just toasted a bagel, slathered some cream cheese and strawberry jam, and scoffed it down with some coffee. The only other noteworthy day-time activities were a couple of short walks I went on around the property. It stayed more or less below freezing so all the trees are still mostly covered in snow, which is really quite pretty. There were a few snow showers, and during one of them, I just stood in the doorway with the door open, and watched giant snow flakes fall silently to the ground. While on my walks, I tried to spot animal tracks, but all I saw was a single deer track on a known deer trail. Normally I’d see some rabbit trails, but I didn’t see any today. Maybe it was too cold last night, and they just stayed in (I wouldn’t blame them). Or, perhaps I was too distracted by the scenery, that I missed the tracks that were there. I think this is about as gorgeous as my property gets, and walking around the snow-covered woods made me feel like I was in a fairytale (though, hopefully one without big bad wolves, or witches that try to eat me for dinner).

For dinner, I cooked some Japanese-style curry, with pork, onions, potatoes, carrots, and brussel sprouts. I briefly sautéd the ingredients in a pan over the propane stove, just enough to get the meat browned, but then let it simmer in a pot on the wood stove for a few hours. I made a big pot full, so there’s plenty left. I’ll probably leave the pot on the stove tonight, so that the pork can cook a little more until it’s nice and tender.

Speaking of food, I’m still trying to figure out where to put everything. I’ve got all the meats and dairy in a single ice chest outside, and I’m not too worried about that unless it gets really warm again. I have some vegetables in my unpowered fridge, also outside, which seems to stay reasonably warm even when it gets really cold out. The rest of the veggies I have split up between Hut 1.0 and Hut 2.1. Hut 1.0 is totally unheated, so it gets as cold as it does outside, which is to say, everything freezes. Hut 2.1 is obviously heated, but most of the heat rises, so I suspect temperatures down on the floor rarely go above 40 degrees, but probably also rarely falls too far below freezing. I have a bunch of bananas up on the loft where it’s warm, since I’ve learned that they just turn black without ripening if left in the cold…

In general, not knowing how long things will last makes it harder to ration my supplies. A part of me wants to use up the fresh veggies while they’re still good, but I also don’t want to use up all my vegetables early on, and only be left with canned goods for the second half. Of course, the worst case would be to let things spoil, but I guess I’ll just have to keep a close eye on my supplies, and use them wisely.

I realized that I hadn’t done a very good job of utilizing the stove’s heat yesterday, so I did a little better today. I’ve had both burners occupied for most of the evening, partially to cook, but also to melt potfuls of snow. I’ve decided to try and get as much snowmelt as possible, because it’s a lot cleaner (and better tasting) than the old rainwater I have in my bins. On the downside, my wood consumption rate is much higher than it was in previous weeks. Part of it is that it’s just simply colder than it was in January (right now, it’s 12F/-11C), but I’m also using the stove more for cooking, so I burn more wood to get it nice and hot. One other thing I’ve come to realize is that, ideally, I should use different kinds of wood for cooking. I’ve been gathering mountain mahogany, which is the densest wood on my property and therefore burns the slowest. That’s great for heating, but when I’m cooking, I want the stove to get hot for short periods at a time, and for that, oak and juniper would probably work better.

I still haven’t set up my 45W solar array, so I’m still just running off of my single 100W monocrystaline panel, which obviously hasn’t been producing much power during these snowy cloudy days. I spent most of the evening with my lights off to conserve electricity, and ran my laptop off its own battery power. My battery array still hasn’t dropped below 12.4 Volts, so I’ve got plenty of power, but I’m not sure how long it’ll be before I get decent sunshine, so I might as well conserve if I can.

Okay, that’s it for today. 30 days to go.