Doug's solar systems

Alternative energy sources
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The usual. As I have two large solar PV systems here, and my lab assistant just put one in, and others are interested in things like this, here's where that stuff goes. This is mostly for things that work now, not "gee someday a fusor will do this" -- we know that, but it's not someday yet.
The hope is to save anyone embarking on this sort of thing a lot of wasted time and money, as at least I have been off the grid since 1980 and have had a lot of practice (and made mistakes you won't have to).

Doug's solar systems

Postby Doug Coulter » Thu Sep 23, 2010 5:34 pm

Ok, for a good solar system you need some panels, some batteries, and some way to use the power. Basically you think of the batteries as a bank account, or maybe a charge card account that gets fees and interest going both ways -- batteries are the weak link at this point in the technology, but are improving, even the ancient lead-acid deep cycle types I'm using.
Here's what they look like on the main system.
Batteries.jpg
Rolls/Surrette batteries, about 1300 AH at 24 volts

These are in a little outdoor box we call the energy shed that also contains the inverters and a belt drive DC generator made from a honda engine and the generator from a P51 mustang.
Boy did they build those well. These are real heavy and it takes a big truck to support that much weight, but once they are in they are in. They cost more per AH than the popular L16 batteries many people use, but they also are guaranteed for 20 years in normal service, while most people get 4-6 years out of the L16 Trojans at most (though I will tell you a trick that got me 8-10 years out of a couple sets). These Rolls guys are just head and shoulders better in efficiency, life, and general operating characteristics, and seem like they have a better ratio of actual amp hours to the rating than the others. Forget deep cycle marine batteries -- they have good peak power but no life, nicads that cost too much and have too variable voltages, gel cells that get ruined on the first overcharge, and vanadium redox batteries (because you can't get them yet). Also, all the Lithium ion kinds they currently think will make electric cars work. No, they won't, they won't do the cycles and people are going to get real upset when they find this out. Test yourself on your battery power tools and see how many cycles they actually live and still have a full use charge, you'll see. Batteries have losses. They are better when new, but they gradually get worse. Even when new, they take charge at a higher voltage than they give it back at -- there's some loss. Also, you don't get quite as many amp hours back as you put in. For example, any overcharging (or just charging to the top) electrolyzes some water into H2 and O2, and that energy floats away. It's just the nature of the game, and when you live on solar you try to keep them charged, but then use power on the way in when you can -- 100% efficient that way.

Batteries are rated for X number cycles (it's kind of relative, at some point you just get disgusted with the lower efficiency). Here's the deal -- if you get 1000 full cycles, you get about 10,000 10% cycles -- so that's how you play it. Further, you can use some large plate area but small capacity marine trolling batteries as "bypass capacitors" to take the peaks that the big boys (which actually have fewer but thicker plates) don't like. This makes the expensive ones (about $6000 for the ones pictured) last far longer. While the cheapo marine batteries only last a year, which would you like to lift and replace?

OK, now that you have a bank account, you need money to put in there. Here's how I do that:
Panels.jpg
Panels


All of these are Solarex brand, bought over the years as I got more money and wanted more power. This is actually too much! (I'm loving it). The rightmost ones on the roof are the oldest, the oldest of those are about 20 years old and still working just fine and still meeting specs. The one missing slot is one I didn't tighten the bolts on well enough, the nuts fell off, and the next hurricane that came through took it off the roof, hanging by the wires. I cut it down and it's now on my big van we are turning into a camper kind of thing. I don't like working on that roof much, so I didn't put it back. The leftmost rack I got about a year ago as part of a group purchase when Dave Knight got a system for his place (which I hope will get posted up here, he did it nice, clean, pretty, and it's working great).

We both recently decided we wanted MORE, so we split a pallet of their newest type, seen laying against the wall. Due to this and that, they are not goint to make it to the roof before winter, so I just hog wired them up right where they are in the garden, and they are doing fine there for the moment.

Solarex is owned by BP oil....go figure. Before that they were Amoco. It's not like the oil companies have no clue the music is going to stop -- they see it and want a chair. Phillips also makes them, nowadays along with everyone and their brother. But these are the best you can get, and for the money. Not the cheapest per watt -- the cheapest per watt-hour -- they live forever unlike the amorphous and thin film guys that die pretty quick, and they cost what they do because they are made of the best stuff known to man, actually not that much more expensive than a good double glazed window the same area, to put things into perspective. People trying to get $/watt down tend to do shortcuts on the frames, the glass, the backing plate that matches the tempco of the cells, and other things, and the result is far higher total cost of ownership, which I have found out the hard way. These are "they work, they last forever, forget them" good.
My kind of stuff.

The light blue ones are rated 125w per panel, the dark blue on the roof 160, and the new ones in the garden 175w. (now I gotta go figure the total).
This system runs this building, in which I live and work, and the one behind it that has all the computers, the shower and guest room, as well as backing up the one on my wife's house.
Today was a good power day, and I ran most of the day just on the panels in the garden, testing if they are enough. Well, we hit full charge on the batteries by noon, then I went out and used the 3.5 hp electric chain saw for an hour or so, and did some MIG welding on my wife's red wagon. When I came back up here, expecting I'd have to kick on the roof panels to recover, nope, no need. For the moment, all the control of that is manual, but I will be putting in a better charge controller soon -- I fried the one I'd had, with too much juice! So now it's just a big knife switch that looks like it came from a Frankenstein movie. Kind of fun to draw a big DC arc off that to impress folks....The rods you see are lightning rods to protect the rest. When we have a storm coming, we pull the big switch, which completely disconnects the panels (no ground either) and lightning hits the rods instead of all this stuff. It's kind of eerie being right under a hit -- no bang till the sound bounces off the surrounding hills, but things in here jump from the magnetism. The computers don't crash, though.

I am using two Trace (now called Xantrex) inverters. One is the old "modified sine wave" which is just a square wave of less than 100% duty cycle, and I use that on the air compressor and things like induction motors -- they really like that waveform and have more torque then on normal sine waves. The other is a SW 4024 which is more sine wave like. It's interesting how they did that. It has three transformers, which are essentially the "bits" in a big power D/A converter. Each "bit" has three states, plus, minus, and clamped to ground. So they are really "trits" and we have a 3-trit D/A here. This is rated at 40a 120v AC (regulated) continuous, and will put out more like 70-100 peaks without shutting off. A dead short shuts it down inside that half cycle, but you have to work at it to get a really dead short. 50 ft of #10 wire doesn't qualify, it will just incinerate that. I use the sq wave inverter also as a charger with the backup generator, which is I think now going to get the retirement it deserves -- we have enough panels now so that even on cloudy days we get enough to do what we do that day. But you never know, so you always have more than one way, and even more than one hot spare for everything. Doing this since 1980 I've learned nothing ever fails on a nice spring day, no such luck. Always on a day the stores are closed and the weather is miserable, and things you let sit and not test (like backup generators) won't work when you need them, so you kinda have a job -- you're the power company after all, and have to keep track of battery electrolyte levels (not very often, but it pays to keep up with things), generator running status, is there fuel, do the panels need the bird poop washed off, stuff like that. Not much actual work, mostly just checking on things.

What I've found in testing other panel types, is that these are the best, hands down. The amorphous/thin film ones are too cheezy to live in real life weather and thermal cycling -- I've bought a few and they wound up in the dump, not even usable after awhile at all. The single crystal ones are smaller in sq feet per watt, but -- they also don't perform as well when the light is coming from all directions, eg when it's cloudy and you need it most. This is one case where specsmanship actually works for the consumer. The poly crystal ones have to be larger for the same rating as they test with light perfectly normal to the panel face. They have random crystal orientation so reflect some of the straight on light, so they need to be bigger to pass that test. However, the parts that don't respond to straight on light DO respond to light coming in at odd angles....so when you need it most, they really shine (or would that be anti-shine?).

OK, now I have the money burning a hole in my pocket, how can I spend it? I fooled around at first with 12 and 24v DC kinds of things -- let me tell you that's a waste of time and money, and the wiring gets daunting for any reasonable power levels. As time has advanced, 120v things have become much more efficient, and of course easier to find. I started out building my own inverters, but was broke at the time and couldn't afford to troubleshoot much when one mistake cost you 10 or twenty then-expensive mosfets, so I topped out at about 500 watt ones, where the transformer itself basically couldn't burn out the fets even with the secondary shorted! And I built those first ones off solar power at 24v, by using an old weller soldering station temporarily divorced from it's 24v stepdown transformer. Yeah, it was an excercise in being a bit too "purist" but hey, it's cool bragging rights too. Those inverters still exist and still work and are in my wife's house now. But for big things like computer consultancies, and machine shops, you need the big power, and at that point just buying the good stuff looked like more of a bargain, so that's what I did.
Inverters.jpg
Inverters and fans and fried solar controller


The inverters are in the side of the energy shed behind the main shop, to keep the high current wiring real short. Lest you get the wrong idea, that upper one with the hanging board and box top off is 20 years old, and croaked because of mouse poop taking out a couple of board tracks which have been fixed since, now I have to put the box back on it. That one is the DR 3524, rated at 35 amp continuous output, which I use mainly as a charger with the generator. It just syncs up and reverse inverts....pretty cool. It will do fairly insane peaks, it easily runs my 10hp air compressor for example, the main thing I use it for now, other than a hot spare. Below that is the SW 4024, which cost more per watt, but the sine wave is a big deal when it comes to running audio stuff etc here in the shop, and it's rugged as heck besides. That one has all kinds of programmable relays etc, that can start generators (I don't do that due to a disaster I'll tell you about sometime) or in this case, turn the shed fans on and off. When it knows the batteries are "gassing" it blows air over them. When it's hot, it blows air over itself. That's nice.

The shed also contains the batteries above, and another generator, a much more thermodynamically efficient one, that I'll put into another post, that is electric start, but the button for that is out there in the shed, forcing you to check if there's things like missing bolts, spilled gasoline, wires off, things like that. Imagine this failure scenario, which we had at one time.

Float bowl in the carb gets a bit of dirt in it. Gas pours into the engine, hydro-locking it, then spilling all over. Now the start command comes, which uses the 10 hp generator as a motor, but it cannot turn. Heck, it draws 250 amps to spin even when free! So the number 00 wire simply burns up. In the middle of all that gasoline. Don't try that at home. Been there and done that. Thank heavens (maybe) it was raining and hailing at the time, or it might have caught the woods on fire too. The other lesson -- don't put a penny in the fuse box because you are too cheap to buy a $20 fuse...batteries and welded relays can really move the amps!

The other box on the left is what's left of a fancy solar controller that couldn't protect itself from a certain condition that happened when a generator was running against bad batteries, (tons of 120 hz ripple) and the sun came out hard....live and learn. They make far better ones now, and I plan to make a PIC based setup for here real soon now.

Batteries are at whatever volts they are at -- here it might vary between 22 volts (on a really bad day, which gets attention right now and someone probably starting a generator) to maybe 30 v when equalize charging. Solar panels are easily modeled as a bunch of forward biased diodes, with the sun doing the bias. The current is a function of the number of photons. This means that with the normal design margins and temperature ranges the peak power output of a PV panel will be in the 35v or higher range, depending. Shorting them out doesn't increase the amperage much at all. So what's wanted (and what that controller did, and which I invented and sold the tech for) is to "impedance match" from whatever the panels are doing to whatever the batteries are doing. Best case, that gives you maybe 30% more net watts into the batteries, when you need it most -- they are low, and that usually happens in winter when the panels are cold -- so their max power volts is higher (the tempco of those diodes). That particular model was rated at 50 amps and trusted its internal logic to keep from frying, but the response time of it's loop was too slow to see generator ripple and act accordingly, so eventually -- poof.

However, these things are a good idea for a number of reasons, and so I'll be replacing that (hopefully with a better design). Reason one is that increase in power -- at the margin, that's cheaper than more panels for the watts. So, good number one. The other is, batteries live a lot longer when carefully charged. These guys usually have a 3 stage charging scheme. When the sun comes up and the batteries are down, they push full power into them. That's good up to a point, but pushing the terminal volts too high at current makes them gas, which wastes both power and electrolyte (more on that elsewhere). So they go into "acceptance mode" holding battery voltage to a set (temperature compensated) number, reducing current until the battery draws below a certain threshold amperage you set. This of course means they need to know net battery amperes, as you may be using some of the input, a complication. They also sense battery temperature, as the batteries also have a temperature coefficient so that volts for acceptance (in fact all the voltage thresholds) need to vary with that.

Once the controller determines the batteries are fully charged, it drops to a float state -- the voltage where the batteries are happy, little or no current in or out of them, with the controller essentially regulating that (providing more current as necessary and if it can) while power goes basically straight from the panels to the house, your piggy bank being full. If some big load happens that the controller can't keep up with, it starts the whole cycle over again, so it's a little state machine. This results in best battery life.

One thing you don't want to do much of is overcharge batteries. This makes them lose electrolyte, which then has to be replaced with distilled water (they lose some sulfuric acid too, which makes a mess if nothing else). Contamination never falls out of a battery, and is deadly to them, so you don't want to have to be opening those tops much. Prevention is best.

So, to roll it all up, we have inputs -- two generators I've mentioned so far, plus a huge welder that can either charge the batteries direct, or through the SW 4024 while running all the 120 volt loads (it's a noisy gas hog, but...nice to be truly ready for anything too). And the main show, the PV panels. I diddled with water wheels and windmills, but it's just not worth the maintenance hassles here for what I got out of them. I also diddled with a thermo generator off the woodstove, but that was only about 12 watts, again, not really worth it.

Then you have these expensive batteries, which paradoxically, you try fairly hard not to use much -- they don't live as long if you beat on them too hard. Then inverters to run the normal stuff, in this case, a computer network, machine shop, fusor systems, and back up the wife's house. You learn some things -- live with the weather, don't fight it -- weld and run the machines on nice days, when that's fun anyway. The other days, maybe don't do so much. Turn things off when not in use, especially "vampire loads" like things that have a needless clock, a remote control (so they are really always on at some level). The sheer number of power strips around here to make that easy would make a hardware store owner smile wide.

For food, we have a top loader efficient freezer (small) and we freeze two liter pop bottles of water in that to keep a couple of good quality camping coolers chilled, which serve as our refrigerators. This is actually where most of the watt hours go, so getting that right is a big one. We found a freezer of the older type, with external coils for the hot side, so I could add insulation to it, and put that in an unheated building with a little fan to blow over the coils when the compressor is powered. Makes more difference than you'd think.

The way it rolls out here, spring is our best energy season. Sun hours are longest, but that freezer still isn't hot and so doesn't run much down in that unheated building in the shade. Worst is fall (now) in general -- still hot, but the sun hours are getting less, and not as high in the sky. Still, the last two days since I wired up that other bank of panels (no fancy controllers yet) are so good I have to pull the switch on the roof bank during most of the day, or I run the batteries up too high! So, now I can just completely forget all this and get one with it all -- this job is finally pretty much done, except obviously for finding a way to mount those new panels up and out of the way -- spring will be soon enough for that, for now, they're even at the right angle for max sun in this season, it ain't broke, so I ain't fixin it. You might think a guy couldn't do this on 4kw, but you can. I can't run all the machines at once, I'm just one guy. I can weld, or I can mill, or I can spin stuff on the lathe and so on. So the non huge peak capacity (nevertheless enough to fry #10 wire) is plenty for me, and simplifies other things.

So, if we ever make real serious progress on fusors, we can also claim we did it completely off the grid! The nearest power line from "the man" is over half a mile from here.

Now, I'm no lefty (by local definitions) and I'm not especially green by their definitions (but I walk more lightly on the earth than any greenie I've ever met). Heck, I'm conservative (not a right wing fascist though, more like Bill Buckley). But this wasn't about that -- it was about power, the power that company had over my life in various ways, and no longer do. I'm an engineer, and I just figured, hey, this is real freedom, and if not me, then who?

Now in my case there is another special payoff. I homesteaded this starting from raw land. If you don't have power company power, well, it's they who enforce the building codes and permits. Without it, you need neither. And your buildings are by definition "barns" as no one believes that without their power, you have power....HAH! So I pay land taxes on "barns" which saves me nearly half the price of the system all by itself -- year after year. Two year payoff, not counting no power bills in other words. Maybe they will get wise someday, but so far, it's 30+ years of "no taxes". Fairly big deal, eh? Can't pull that one off most places I'd guess, but I am where I am, and it's partly for that reason -- freedom, little government interference, natural beauty, all that ;) :D

Despite some astroturfing by various "business as usual" sorts, this really works and works well for any detached dwelling, we can even run air conditioning sometimes, and have the power right when it's needed most, by some fluke of nature (heh). Up here in the mountains, it's rare to need AC anyway but it's nice sometimes. We don't have to adapt all that much, but do so willingly -- it's good to take a break if it's a week of darkness, and read and contemplate for example, and having power up to your ears on some other days is a nice motivation to go use some of it since it'd be wasted otherwise. So, it works out. Those poor city dwellers, I feel for them and their "conveniences" as they'll never know how nice this is. When they talk culture, well, I can do many things from whipping out an instrument, to showing them the art gallery here, to taking them to the local theatre for a play or to see some good down home flat pickin at the general store. They can walk to the nearest beer store, I have to drive my hotrod over some of the most fun roads on earth to get there, oh poor me. And what few neigbors I have are nice, not potential child molesters or thieves -- you don't do those kinds of things in places where everyone knows everyone and live too long, so it's just better.

I won't say everyone should do this, but it IS cool, nice, and it's nice bragging rights besides. Nothing like knowing you're not dependent on some batch of jerks who say things like "we don't have to be reasonable, we follow policy"!


//////////////////////////////////////////////////////////

Someone once said that PV's don't make back the energy they take to make. Hah! I destroyed a wrench today wiring up that rack of 2kw more....a little impromptu arc welding with pure DC.
That one rack's worth would have been easily able to melt itself had I desired that -- in a single afternoon. How much energy can they possibly take to make? yeah, they use evil chemicals, which all wind up as dopants in the cells, not in the environment. The bulk is the most common stuff on earth -- glass, aluminum, silicon, and a bit of copper for the wiring. Not a resource hog.
In other words, the raw materials are sand and clay -- anyone hearing of a shortage of those?


Ok, prices:

Panels, roughly $500 each, and I've got more than needed now.
Inverters $4000 each, and you only really need one if it's a good one.
Batteries -- $6000, more or less.
Racks and wires, I forget. They weren't cheap, but I did the racks myself and saved a ton there, and all the wiring. I bought most of the fat wire at a metal recycling place for much less than the hardware store prices too.

Expected life -- well the panels on my wifes house are now 33 years old and still work like new. That place is on the second set of L 16 batteries, and about to switch to the third set, which are used from here before I got those nifty new red guys. No inverters have failed, and only one of 3 solar controllers have failed in that whole time. We've run through a couple of backup generators -- at about $300 each. That's total cost, plus some odd hours here and there fixing stuff when it breaks. This is very real life, actual experience, time tested. If someone tells you different, you might want to consider what their other agenda is....I'm sure others have been had on cheap junk, and that's not worth it, but with the right stuff -- it sure is.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
 
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Location: Floyd county, VA, USA

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