DIY Solar Resources? 311
TihSon writes "I'm building a large shed out back and I want to power the lighting using a surplus solar panel. In searching for information on how to go about this, I have found a lot of rough DIY guides for various projects that are close to my goal. But none seem to explain the reasoning and theory behind using solar panels, so hacking their project to suit my own needs could be pretty much hit-and-miss. I don't want to do a hacked-up job, and future solar projects are not out of the question, so something a bit more in-depth is required. Do you have suggestions for books or Web sites you have used to learn the ins and outs of using solar panels? Something that starts with basic theory and ends with the ability to wire a house would be perfect."
2 words Home Power (Score:5, Informative)
The Otherpower forum (Score:5, Informative)
Re:Free energy (Score:4, Informative)
Since you're doing the lighting from scratch, and you want it exclusively powered by solar, I'd suggest looking at low-voltage DC lighting. DC bypasses the inverter, so it's more efficient for the same type of lighting. It's also probably less likely to kill you/burn down your shed if you make a mistake.
Disclaimer: IANAE - I am not an electrician
Re:No, no, no (Score:4, Informative)
But he doesn't seem to want to wire his house... "I'm building a large shed out back and I want to power the lighting..." or even bother with other electrical devices, nevermind water.
I'd have to agree, and other people have mentioned this already, use LED type lighting, this negates stuff like inversion to get 115/220 volts, etc. and requires far less power in the first places, which means less solar panels, less batteries, probably less wiring, and LEDs last longer than incandescent, and provide better lighting than neon.
Re:No, no, no (Score:3, Informative)
There are lots of little things with wiring that can have serious consequences. Where to put the ground? Please not too near a metal anything especially pipe. Why? It'll accelerate corrosion. Possibly greatly. You can screw up your neighborhood's cable this way too.
There are fire risks for improperly installed wiring as well. Or just improper choice of materials. In a house there are other concerns such as fumes given off if cabling ends up in a fire irreguardless of what precipitated it. Builing codes exist for a reason. The 1 in 10 occurances are obvious enough and easily avoided, it's the non-intuitive 1 in 10,000 occurences that take a little foresight. With 100s of thousands at stake for millions of home owners, and the virtual impossibility of knowing all the minutia of one's own particular circumstance, best to go with building code safe as opposed to back of cocktail napkin sorry.
That said: A solar shed is probably pretty straight forward. You know the voltage you want, get battery configuration that will give the amount of stored current you want, and set it up for the voltage you desire, and just run the shed off a properly installed and secured stack of batteries with the solar charging them. They probably have a weekend workshop at a Home Depot or Lowes that would get one at least half way there.
As another person above states that's not the biggest bang for the buck, but it's certainly doable as a little project.
Re:Solar is hit and miss ... (Score:3, Informative)
... you've got clouds and rain and much less than 12 hours of sunshine available on any given day year round.
At the Equator: solar
At the Poles: wind
In between: combination of the two
Re:Car and Caravan components (Score:5, Informative)
Re:DIY? Why? (Score:4, Informative)
Why not? I am off-grid with two sets of solar panels (house and well). Did the whole thing mysef with a little help from my friends at Home Power. Not a problem unless you're totally clueless, which, being a Slashdot reader, you're obviously not. Got to homepower.com, buy the CDs.
Re:Free energy (Score:2, Informative)
And then you need the damn huge cables to go with it. DC current has huge line losses unless you're willing to buy expensive, fine-stranded cable at #4AWG or bigger. That 1500W monster power supply you have sitting in your living room suddenly requires 125 amps of 12V power at full load. That'll melt the insulation right off a standard 14-2 solid copper AC line.
Re:Free energy (Score:3, Informative)
Re:No, no, no (Score:5, Informative)
There are lots of little things with wiring that can have serious consequences.
No, there really aren't. There are a few little things and a few big things, and very few of them are arcane. Electrical systems in a typical residence are neither rocket science nor magic. A relatively good primer for residential electrical systems for a typical homeowner would be B&D Complete Guide to Home Wiring [amazon.com].
Where to put the ground? Please not too near a metal anything especially pipe. Why? It'll accelerate corrosion. Possibly greatly. You can screw up your neighborhood's cable this way too.
Please, please tell me you're not an electrician, nor are studying to become one. Either you WAY oversimplified to the point of making your statement meaningless or you know nothing about the ways galvanic reactions are mitigated in residential wiring. Any text on residential wiring will mention the problems and the very simple ways to avoid them ever becoming an issue.
You're right though, there are fire risks if you don't take any care with your wiring practices. Good wiring practices are amazingly simple to learn. That said, most homeowners I'm aware of who undertake electrical work for themselves do not ever bother to do so.
virtual impossibility of knowing all the minutia of one's own particular circumstance
This statement is a crock. Residential wiring is pretty straightforward for anyone willing to crack any number of simplified wiring books. Solar systems are relatively straightforward as well. I'm honestly not sure why the submitter believes that any number of other project descriptions could not be adapted to a solar shed, unless they plan on tying it into something else at a later date.
However, and it's a big one, solar intertie systems can be enormously complicated. If the submitter is planning on later tying the solar system in a shed to one in a house, said person is going about things bass-ackwards. An intertie needs to be planned from the ground up, or the likelihood of large (and costly) problems shoots through the roof.
Many things need to be answered right from the start. Am I installing a system tied to the power grid? A backup system not tied to the grid? Are there going to be batteries involved? Do I plan to convert to AC, and if so do I need clean sine-wave power? Can my charge controller handle the potential expansion of solar panels? Can additional inverters and/or charge controllers be added to the system without a great deal of hassle should the initially chosen models not handle panel additions? Am I just planning to run dedicated DC lighting circuits? These answers should take into account future plans to expand the system, as picking one particular route and then later making substantial changes to the upgrade path can dramatically increase equipment expenses.
Depending on the complexity of the situation and whether the DIYer actually intends to acquire the knowledge necessary to execute high-quality, functionally correct work, professional help may or may not be necessary.
Re:No, no, no (Score:3, Informative)
DC cabling is not going to be adequate to carry residential loads. While you could hack together a cheap system, you'll get the quality that you pay for.
While I honestly couldn't care less if homeowners do so without permits, most jurisdictions do require electrical permits and inspections for installing DC systems. The "burn down your house" is hyperbole, but if you have homeowner's insurance you'll likely need to comply with permitting requirements. In the event of a fire or other damage as a result of wiring, your insurance may not pay even if the work you did played no role in the damage to the structure.
Using small, cheap inverters at point-of-use is going to introduce problems. For one thing, the power produced by cheap inverters is by no means high quality. Most cheap inverters produce modified sine-wave power, which can be problematic for certain appliances (computers, battery chargers, A/V electronics, some electrical appliance motors). You're unlikely to be able to find out whether a particular appliance is affected until after you plug it in. Another problem is that transporting DC at lower voltages means you need conductors larger than a typical AC run would require for the same distance. I'm not sure if you've checked copper prices recently, but it adds up pretty quickly.
For an AC-DC system, the best-practice route would be to install one or more inverters at the location of the mains entrance to the house. This allows for typical residential AC wiring practices to be used, which vastly simplify the situation. It'll save time, money, and headaches in the long run, though the system will initially be a fair bit more expensive. Even an on-the-cheap installation is really anything but cheap.
Re:Well? (Score:1, Informative)
Re:Solar is hit and miss ... (Score:3, Informative)
Sorry but axial generators are NOT an ideal solution at all - very inefficient. You will also find that your neighbors may not like you putting up a tower that sits so high above the surrounding trees - as it must in order to get clean air and be free of debris. On top of that the cost of the crane required to loft many of these is expensive. Add to that the fact that not *many* areas get enough wind to be useful and you'll find that wind isn't too great - especially for just a shed!
This isn't the best chart but perhaps this will help http://www.awea.org/faq/usresource.html [awea.org]
P.S. Wind isn't 24X7 in many places either. I have a wind gauge on my roof on top of a pole and can go for hours with ZERO wind, I go DAYS without useful winds for power generation too.
Re:Free energy (Score:5, Informative)
DC power transmission over short distances is feasible. Over long distances, it isn't. Look up the Current Wars and AC power distribution. For DC, P=I^2*R=V^2/R. For AC, Prms=Irms^2*Z=Vrms^2/Z. Ignoring phase shift and comparing RMS AC quantities with DC quantities, the equations look the same. The longer the lines, the larger R, so the larger your power lost to heat. DC-DC power conversion is a modern solid-state technology (using charge pumps?) and still tends to be expensive, intolerant of transients (without proper filtering), and limited to small voltages and/or currents. AC-AC power conversion is simple, cheap, and can handle huge currents and voltages. Also, it's much harder to go from DC to AC than the other way around. Until modern solid state, in fact, there was no reliable, efficient way to convert DC to AC in any significant quantity.
If you had a shed and a house on two sides of a large property, and you wanted to put solar panels on one and bring some power to the other (perhaps it is in the shade), inverter + step-up transformer + step-down transformer + AC-to-DC is going to have a noticeable improvement in efficiency over trying to carry DC long distances. If you're generating any serious amount of power, you're also going to need some thick, thick cables to carry lo-volt hi-amp DC around in order to safely dissipate the heat, especially for wires running indoors. Even if you don't care about losses, converting to/from AC is much cheaper than replacing everything in a burned-down house.
Mod parent up! (Score:1, Informative)
Check out some good magazines (Score:5, Informative)
I recommend you check out "Home Power". It's a magazine dedicated to off-grid power production (solar, wind etc). It's a good read, very informative, and has a lot of good printed links to various resources.
It's about $4 an issue.
I dodn't work for them, but I love to read that mag.
Re:Well? (Score:5, Informative)
But then there's thermal energy derived from the sun and there are nearly limitless possibilities there since the development of that carbon nanotube material that absorbs 99.8% of all light that hits it. I imagine that in many parts of the country that could be converted to heat water, create steam and drive turbines, or the new stirling engine technology if it's getting along, or even just store it underground for later use. Then one could combine that technology with the brilliant idea where they essentially put the solar-thermal collector in a vacuum so that the heat couldn't boil back off of the collector and it instead got passed quickly away to an insulated tank. It was viable over 10 months out of the year and even worked on cloudy days. I'm sure it was posted here a while back.
Re:No, no, no (Score:5, Informative)
Don't know where you live, but in most areas of the U.S. you legally need a permit and an inspection to perform any electrical work on residential wiring. When I say "any", I mean even down to installing an outlet or changing any type of fixed fixture. Most areas require all electrical work to be in accordance with the N.E.C. and /or the I.E.C. Further, most jurisdictions require that the person doing the residential electrical work have a valid Electrician's license. Some jurisdictions allow a homeowner to do their own electrical work, but only on their own dwelling and not on properties they own that they rent to tenants. In many jurisdictions performing unauthorized and/or unlicensed electrical work is a crime, punishable by fine and/or imprisonment.
As a licensed Master Electrician and former County building inspector, I can state with great confidence that simply reading a book such as "B&D Complete Guide to Home wiring" does not render one competent to undertake even moderately complex residential wiring projects. As I have witnessed, even seemingly straightforward tasks like stripping wires and using wire nuts can have devastating consequences when performed improperly.
To advocate that an unlicensed and inexperienced homeowner take on this type of project without adequate, licensed professional supervision is irresponsible in the extreme. No licensed electrician would advocate such irresponsible and potentially hazardous course of conduct.
Re:Well? (Score:5, Informative)
Re:Free energy (Score:1, Informative)
You may need to read a few books/web pages before you can get the total picture. But here's a quick checklist of what you need to know:
1. Learn the basics - V=I x R, P=V x I, and most importantly power lost P=I ^2 x R.
2. Best if you can show a sketch of your plan to an electrician or engineer just to make sure that you are not doing something dangerous or against local law. Make sure that each of you load have properly sized fuses (or circuit breakers).
3. For a DC solar voltaic system, you will need to know what load your setup will consume, and how it relates to the the size the following components:
a) Solar Panel
b) Charge Controller (connects the panel to the battery when the sun is shining, disconnects otherwise, and ensures that the batteries are not overcharged)
c) Low battery voltage cut off circuit (sometimes included in b)
d) Batteries
e) Wires, terminal blocks, fuses/circuit breakers
For an AC system, you will need to add an inverter.
The choice between AC or DC is important because DC systems are usually low voltage (12 or 24V) which means higher current. A rough example, if the wire to your lamp is 150ft long with a resistance of 1 ohms, powering a 12 watt lamp (12 volts at 1 amp of current), Using P=I^2 x R, one will lose 1W to heat. Compare this with a 12 watt lamp running 120VAC at 0.1 amp current, one will only lose 0.01 W. There's a tradeoff of using a more complicated AC system (using an inverter) or spend more money to get bigger cables to reduce resistance.
BTW, IAAEE: I am an Electrical Engineer
Hyperbole? (Score:2, Informative)
Marine battery + panel + DC lighting. Done (Score:5, Informative)
Shed lighting is pretty easy because the power requirement and the duty cycle (on vs off time) will be low, and you don't need voltage regulation. That means all you need is a largeish 12V battery (preferably rated for "deep cycle"), and a modest 12V solar panel of maybe 2-3 square feet. Test with a small setup first, and then if you want more run time (from a fully charged battery) add another battery. For more duty cycle, add another panel.
Hook the panel to the battery with a diode in series, and then hook 12V lighting (eg track lighting minus the transformer) to the battery, and you're done. Solar panels are inherently quite compatible with lead-acid charging requirements, so you don't even need charge circuitry for a small setup such as this.
If you want to power a small 110V device, you can use an inverter. You won't be running a table saw on one of those though.
Treat Batteries Like they are a bomb (Score:4, Informative)
Since becoming a ham several months ago, I started learning all about batteries and 12V power and while I was at some solar energy stuff. Starting with a shed project is a great idea. I am assuming you are looking to light things, not run a planer.
Oh yeah, treat all large batteries like they are bombs ready to go off. Store them outside, and if it gets below 0C then you might have to figure out how to keep them warm. Good luck with that.
Re:No, no, no (Score:2, Informative)
Making a blanket statement as you did tends to result in severe cases of "Foot in Mouth" disease. FYI a 50watt 12v PV panel requires a minimum of 8ga wire to connect to the busbar while a 200watt panel requires at least (4)0 wire (quad aught) to handle the amperage it can easily output and most PV panels over the 150watt rating are configured for 24v output.
Now depending on what the OP wants to do with the PV system is going to determine what he needs. If it's simply lighting for a shed, then the issue is even simpler. Get a small PV powered light unit (Brinkman/Others) from the local Home Improvement Center or order it online and use it to light the shed. If it's anything more then lighting, then you need to consider appropriate wire gauge to minimize voltage drops, Purchasing of DC rated switches (standard household switches aren't safe due to arcing).
In regards to the 120/240 AC voltages, you're actually better off putting the Inverters near the batteries and running standard house wiring because of safety factors. We're damn familiar with AC power and there's plenty of standards to follow when working with it. PV systems with high amp DC circuits are very dangerous Common Automotive Batteries can output in excess of 1200A when the posts are shorted, so you damn well better protect those batteries.
Right now the best solution would be to head over to Mr Solar [mrsolar.com] where you can find plenty of PV related equipment and kits for numerous projects.
Re:No, no, no (Score:3, Informative)
Re:Marine battery + panel + DC lighting. Done (Score:4, Informative)
That is a good basic plan. The 'open circuit' voltage of the panel needs to be around 18V to charge a 12V battery. 12V CF lighting is available from a number of vendors, I would highly recommend it over 12V halogen track lighting:
http://store.altenergystore.com/Lighting-Fans/Compact-Fluorescent/Compact-Fluorescent-Bulb-12V-7W/p1003/?source=froogle
I don't really like these 12V bulbs that screw into a normal 120V socket, but what are you going to do...
I would also suggest skylights. There is really no point is converting light to electricity and back to light.
Honda also makes some super quiet generators that are less of a pita than solar.
Re:Well? (Score:2, Informative)
Who are the nutcases that mod this kind of drivel "Informative"? That author has no clue what he's talking about. A shed without power plus a solar panel equals a shed with power - and all the whining of the anti-solar retards isn't going to change that.
IT DOES NOT MATTER what idiotic games you can play with dollars to make solar look unattractive (and the fact that have to play games in the first place proves you squarely wrong anyways) when you have a shed without power. There's simply one solution and no word-games and math-fiddling is going to make it go away. There's NO alternative. You go ahead and power your lights with fifty-packs of C-batteries that you have to replace once a week, but for reasonable people who'd just like to run a light in a shed, solar is THE solution.
Re:Simplest Solar Powered Lighting (Score:3, Informative)
I would certainly take that approach. The fewer steps of energy conversion, the better.
If I ever get prosperous enough to afford it, I will be converting our home to renewable (off the paid electricity grid). Probably a gradual process but I have to say investing in simple things like skylights, insulation, solar hot water heating has the best long term pay-off, since there is practically zero maintenance involved.
Re:Marine battery + panel + DC lighting. Done (Score:4, Informative)
1.) no voltage regulation
a.) is bad because the more current you draw from a pv-panel the less voltage you will get thus you cannot charge a battery with
(your solution is by adding a diode to prevent this)
so a pv-battery charger and monitor is highly recommend, because lead-acid batteries need to be watched carefully you can ruin them by discharging them to their least.
b.) pv-cells have no linear characteristic, not keeping this in mind will lead to a lower effeciency, they have a
MPP - Maximum Power Point[1], the characteristics are mostly supplied with the datasheets,
also the MPP is given. So using voltage regulation you can draw more power from the cells as you could otherwise.
[1] http://en.wikipedia.org/wiki/Maximum_power_point_tracker
Re:No, no, no (Score:2, Informative)
slashdot is a good site (Score:3, Informative)
Plenty of folks here have solar PV experience, several guys run whole house systems.
Steps: Determine your mount, do you want a roof mount? Most likely. They make those you can buy, or you can fabricate your own, just starting out go ahead and get the mount from the same place you buy your panel. but make it accessible enough on the roof so that a few times a year you can access it and adjust the angle relative to the sun. This is determined by your latitude, you can find maps online that address this. Seat of the pants,this works just as good, once a season (solstices and equinoxes, 4 times a year in other words) go out exactly at noon, adjust the panel so that it perpendicular/flat to the sun.
The panel itself will have a metal frame with a grounding hole indicated. You need to install a grounding rod at the shed base, big fun, you'll develop manly man muscles hammering that bad boy in. Here's a hint, dig a hole where you want the rod to go (after first determining you are *not* going to hit a waterline or some other underground man made obstruction of course, common sense rules there), soak that hole with a bucket of water (that gives you an idea on the size of the hole to dig, something that can take a few gallons and sit there and soak in) periodically for a couple days before hammering in the rod. Man it makes it much easier. Where you buy the rod, they will have grounding wire and a connector clamp. You'll need a nice maul to get it going, a normal hammer would be possible but I don't recommend it. alternatively a fence post pounder, maybe you can borrow one. Lowes/ Home Despot have all of that. At the panel frame, just a good stout bolt with lockwashers and regular washers is adequate for the ground wire. For lead wire, welding cable you can buy off the roll by the foot is good enough for your shed needs, and your run won't be that long anyway most likely. Conversely you can use exterior grade house wiring, again, by the foot. that is more resistant to sunlight/water/whatever. If you want or need by code conduit, again, cheap plastic pipe at the store and glue and a hacksaw and some clamp mount action.
Next you need to run the raw output of your panel to a charge controller (those ship with wiring diagrams as well), then the feed from there will go to your battery. If you are using a smallish panel it will nominally output 0VDC at night with no visible moon to around 17 (maybe higher) or so VDC at high noon on high summer day. The charge controller adjusts this, better quality ones monitor the charge going to the battery and adjust as it is needed for optimum charging, which is a three stage process of voltage regulation. It will shut itself off when the battery is full, indicated by the colored lights on the controller (some have a little LCD panel with interesting little things to look at ;)). If you find yourself with extra juice potential (I bet you do) by early afternoon, lucky you, you can add an additional battery in parallel if you want that juice. I am a big fan of having lager than what you think you might need battery action, more and bigger. Makes them last longer.
For battery or batteries, now your choices get varied depending on needs, but rule of thumb with batteries after all is said and done and all the marketing BS is out of the way is you are buying lead by the pound. that's it. More lead, more stored juice. Your cheapest solution is a normal 12 volt "trolling" motor battery they sell for boaters and fishermen. Those batteries are designed to run a trolling motor for hours, they should be sufficient for your modest lighting needs. You'll need ring connectors for your lead wires, attachment is straight up, positive and negative. Next step up would be two 6VDC batteries, or golf cart batteries. Those get wired in series to give you your 12, then in turn are wired from the controller output, on one battery it is the negative, on the other it is the positive. the two others are connected battery to battery, that is your series connection. To keep it sim
Re:Car and Caravan components (Score:2, Informative)
For those not from the UK, a caravan battery is probably one type of deep cycle battery. These are mostly wet batteries that use acid and water as an electrolyte. There are a number of lead acid batteries called by different names: marine, locomotive (big!!), golf cart etc. The primary difference between a car battery and a deep cycle battery is the size and perforations of the electrodes. Car batteries have lots of perforations to produce lots of amps quickly. In the deep cycle battery world, you need larger batteries to get more amps. How big? Well, 1000lb batteries for large solar installations. The leading manufacturer with a neat interactive website is Surrette Battery http://www.surrette.com/ [surrette.com].
Golf cart batteries are very interesting for these projects. They are 6v batteries that are relatively cheap ($60-$200) each, connect them in series and you have quite a bit of energy storage.
Other types of lead acid battery uses absorbent glass mat or gel (not the same thing)to reduce the chances of an acid spill.
Lead Acid Batteries http://en.wikipedia.org/wiki/Lead-acid_battery [wikipedia.org]
Absorbed Glass Mat http://en.wikipedia.org/wiki/Absorbed_Glass_Mat [wikipedia.org]
CAUTION: Lead Acid batteries contain allot of stored energy. Equivalent to a stick of dynamite, and all you need to do is short it and they WILL explode. Please treat lead acid batteries with extreme care. Nothing like an exploding bomb of sulfuric acid to fuck up your day. Do not use lead acid batteries in your house, or near kids. Yes, I know people who have had batteries explode while working on their cars..
And for those who want batteries, but just use mains power to charge the batteries, here is an excellent charger that many hams use. http://www.a-aengineering.com/5smartcharger.htm [a-aengineering.com]
Re:Mod grandparent down! (Score:5, Informative)
The second assumption is that the only thing that effects cost of an item is the energy used to produce the item. Also demonstrably false.
The third is the assumption that energy costs are uniform across the planet and that they do not change with time. Has he ever looked at his power bill?
Don Lancaster needs to take an Introductory Economics course. From this article I gather that the term "informally peer reviewed" means "read by people who agree with me and guess what, they still agree with me."
Re:Well? (Score:3, Informative)
Then they should license the fucking patents to someone who WILL manufacture for the consumer. The problem with their approach is that solar energy is actually MORE efficient in a decentralized production environment. Solar power stations for utility monopolies are inefficient, compared to solar panels on every roof.
Re:Marine battery + panel + DC lighting. Done (Score:2, Informative)
We used a deep-discharge AGM battery purchased locally. The panel we bought online from www.solardepot.com. We considered just using a series diode, but eventually opted for an inexpensive SCN-2 charge controller from www.allelectronics.com. We also picked up the AC inverter there. (Checking, I see the price for the controller has gone up, so you might want to shop around for one that's a little cheaper.) The various other parts, like the mechanical dial timer, fuses, outlets, conduit, and assorted mounting hardware were all purchased locally.
Frankly, the hardest part of the project was coordinating the installation (which involved getting up on the roof) with the school. The electronics went together effortlessly.
Our main worry wasn't that the setup wouldn't work, but rather that it would be vandalized. But for whatever reason that hasn't happened.
Re:Free energy (Score:2, Informative)
Re:Google shopping results (Score:3, Informative)
Re:Google shopping results for "solar powered shed light" gives a lot of good solutions. Anywhere from $30-$100, fluorescent or xenon, indoor outdoor...
Hawaii (Score:3, Informative)
Solar is economically competitive in some markets today, like in sunny places with high electricity prices, e.g. Hawaii
The big island of Puna in Hawaii gets 30% of it's energy from geothermal [energy.gov] power.
FalconRe:Well? (Score:4, Informative)
Yeah, that'd work wonders at nighttime.
Because you _never_ do work in a shed at nighttime.
Re:No, no, no (Score:3, Informative)
A 220 circuit isn't too complicated. I mean, seriously. You have three or four wires, right? A ground, a neutral, and then one or two hot wires. The two wires have opposing sine waves on them, so if you pull from both you get 220, and if you pull from one and the neutral you get 110. Just don't fuck up! That's the one thing that most people get wrong :) Seriously though, just keep which wire is which more or less straight, and keep things balanced, and you can wire up all kinds of shit.
If you don't want to burn anything down or kill yourself, follow simple rules, like assuming every circuit is live if you don't know if it's live, and testing everything before you touch if even if you "know" it's not shorted out or cross-connected or whatever. I shouldn't admit this but I've been shocked with all kinds of stuff (not including 220V, but including the signal off the CRT card on a VGA monitor, whee!) and I'm still here because when I was being stupid enough to get shocked, I was smart enough to keep one hand in my back pocket. If you're going to be stupid, be as smart as possible while you're doing it.
None of this is going to convince anyone to let me wire their house, but it's not that fun anyway. The fact is that it's really quite simple, and only the steep potential penalty for failure should scare anyone away. Use quality parts, use the boxes, follow the code when all else fails, and don't let anyone with a professional certification tell you what to do just because of a piece of paper. Remember, not that it applies directly here, but MCSE == "Moron Confused by Sun Equipment" and CNE == "Certainly No Experience". Electricians have to have experience, but they don't have to come down off their ivory tower.