Using microinverters for solar power
March 13, 2010If you only plan to sell the electricity you produce back to the electric company and not go off the electrical utility grid, then the microinverter may be the most elegant solution. You use a single one of these inverters with every solar panel in the system. Simply connect the solar panel to the inverter and connect the inverter to your electrical box–only two sets of connections.
What are the benefits?
If you use a microinverter, expansion is easy. You can start with a single solar panel and inverter to have a complete grid tie system. Adding to it is almost like adding a set of Christmas lights to an existing set. The plugs and sockets are different because they’re made to withstand weather.In addition, microinverters give the advantage of maximum power point tracking (MPPT) for every individual panel. This means shadows or performance issues with one panel won’t affect the others. If you opt for Enphase’s microinverter, you also have the ability to get detailed day-to-day, hour-to-hour statistics for every panel! Watch the How It Works video for a video representation.
Where can I get one?
Microinverters are still somewhat new and haven’t really made it to mainstream as far as solar power is concerned. The Affordable Solar Group and EcoDirect have some pretty good prices, (but their solar panels are a bit pricey). There are many places on the web to get microinverters.The only microinverter that is currently available is from Enphase. Another is in development from SolarBridge.
How do I connect it?
Don’t be intimidated with wiring this device. If you can install a household socket or light switch, you can install this. If you can match colors and put up Christmas lights, you can install this. The instructions alone should make it very easy to understand.If you watch the Enphase Micro-inverter System Installation video, they make it sound simple, because it is simple. But, it does take some time. Don’t let the phrases about electrical code and “qualified personnel” scare you. I’ll discuss this in more detail in another article. Check out this New Jersey Solar Installation video for some good details.
Choosing a Solar Panel
All you really need to focus on is buying a compatible solar panel for the microinverter, (unless you’re comfortable with splicing and soldering the wires of an incompatible panel). You should be able to find a compatibility list in the support section of the company’s website. Enphase, for instance, has a download section.Connecting the Microinverter
First you generally need your inverter in place before you connect your solar panel. Run conduit up to your roof (or your panels’ location) to a junction box. Enphase prefers you to buy an AC branch “Install Kit” for $60, but you could easily get your own parts separately. Or, you could just run the inverter wires to a box and run conduit to an inside switch which would probably be cheaper, maybe $20. From there, just run wires into your electrical box to a circuit breaker. Check out Installing Electrical Conduit Systems for more details.Connecting a Solar Panel
The inverter and solar panel will likely have special connectors. These connectors are designed to be fool proof. But if you’re an electronic hobbyist you may want to get less expensive solar panels that aren’t on the compatibility list. If that’s the case, make sure you have the correct voltage, (you might need two panels in series or parallel). To connect a panel, just:- Cut off the connectors from the solar panel and inverter (this may void the warranty)
- Prepare heat shrink tubing to cover your connections by placing them over the wires (available locally at Radio Shack or online)
- Solder positive to positive, negative to negative
- Cover your connections with the heat shrink tubing and shrink it
Living on DC
March 8, 2010Most of our everyday appliances and electronic devices operate using AC (alternating current), right? … It might surprise you that most appliances we use today are using DC (direct current) rather than AC. Internally they convert the AC to DC. If you’re an electronic hobbyist, you probably already know that. If you’re using a solar system with batteries, you could save by using DC directly.
Reaping the Benefits
The benefits of running things off DC directly is that you have no conversion loss. Inverters and power supplies alike have a conversion efficiency. Most conversion efficiencies lie somewhere between 80-95%. If you can reduce the number of conversions, you will come out ahead. However, it may require you to have ten 12V batteries wired in series to obtain between 110-130 volts DC. You could use a DC-DC converter, but that would defeat the purpose.Distinguishing What Uses AC
First you need to know what you can and can’t operate with DC. You cannot use DC on anything that has a transformer on its power input. You can use these steps as a guideline to determine what can be operated using DC, but the only way to really know is to look inside:- If the appliance has a mechanical switch, turn it on unplugged.
- Use a multimeter to measure ohms (Ω) across the prongs of the plug.
- If the meter reads about 500 ohms or less, it likely uses a transformer.
- Air conditioning and heating systems
- General purpose fans and ceiling fans
- Washing machines/dryers
- Refrigerators/freezers
- Microwave ovens
- Garage door openers
- Fluorescent lights with ballast transformers
- Cell phone chargers (which are usually small wall mount transformers)
- Anything with an AC motor
Distinguishing What Uses DC
You can use DC on anything that has a bridge rectifier on its input. A bridge rectifier is something that converts AC to DC using four diodes. If you can measure around 1 meg ohm (MΩ) or more across the prongs of the plug using a multimeter, it most likely uses a bridge rectifier. Again, the only way to really know is to look inside. Most of the following items use a bridge rectifier or can use AC or DC:- Any lengthwise oriented or switching power supply (doesn’t mount on the wall)
- Computer/Laptop power supplies
- Incandescent, CLF, and LED light bulbs or Christmas lights
- DVD players and newer VCRs
- Game consoles
Replacing Wall Transformers
One of the most pesky things to deal with are those big black and inefficient wall transformers. The output of most of these are DC because they use a bridge rectifier on the output of the transformer. If you can find a switching power supply at the same DC output voltage to take it’s place, then replace it.Solar panel wiring
February 28, 2010Some may think there’s a lot to know about wiring a solar system, but the truth is the basics are pretty much the same as they were 20 years ago. Wiring solar panels is like wiring Christmas lights. There are several sites out there that show you the basics. However, it’s important to know when to use the methods discussed.
What’s your input device?
Before you buy solar panels, you need to know what you’re going to use to convert the solar power. Are you using a charge controller and/or a grid tie inverter? Here’s a couple of different things you could use (click on their description tab for details):- Kaco blue planet 1502xi Inverter
- PVPowered PVP1100-SD-120
- Morningstar TriStar TS-MPPT-45 Charge Controller
- OutBack FLEXmax 80 Charge Controller
Wiring
First, it’s important to know the basics. There are two basic ways to wire solar panels, series and parallel. Series arrangements increase the voltage of an array. Parallel arrangements increase the current of an array. Let’s use an 80 Watt, 12 Vpm, 6.6 Ipm solar panel for examples. (See my article about choosing solar panels to learn what Vpm and Ipm means.) Wiring panels in series:- +/plus/red to –/minus/black, +/red to –/black, + to –, etc.
- Three panels in series equals 36V at 6.6 Amps.
- +/plus/red to +/red to +, –/minus/black to –/black to –, etc.
- Three panels in parallel equals 12V at 19.8 Amps.
- Solar Energy Science Project Topics: What are PV Panels?
- Solar Energy, Power, Electricity
- Physical Computing at ITP | Notes / Solar Cells
- Learn how to wire solar panels and battery systems
- UPM Solar Decathlon 2009: Solar Roof
Series vs. Parallel
These wiring arrangements, though different, generally achieve the same result in terms of power. But there are differences you should consider:| Series | Parallel | |
| Electrical focus | voltage | current (amps) |
| Wire diameter | smaller | larger |
| Physical handling | easier | harder |
| Cost per foot | less | more |
| If one panel is in the shade: | the whole string produces less power | the other panels are unaffected |
The device you use to convert your panels’ power will determine your wiring arrangement, or vice versa.
Direct Solar-to-Grid Inverters
Most high power grid tie inverters (for solar systems) will require many series connections of solar panels. If you look at the input specifications for the first two devices listed at the top, they require 120-400 VDC.You’d need 25 * 12 Vpm solar panels in series to make 300V. Or, 5 * 60 Vpm panels. Notice how much current these inverters can handle, about 20A. They generally don’t need a lot of current at that high of a voltage.
Charge Controllers
Most high power charge controllers will require more parallel connections of solar panels. If you look at the input specifications of the last two devices listed at the top, they’re good for 45 or 80 Amps DC.You’d need 6 * 10 Ipm solar panels in parallel to make 60 Amps. Or, 2 * 30 Ipm panels. These charge controllers can still handle up to 150 Voc, but they’re designed to work with higher current. They generally don’t need higher voltage like solar-to-grid tie inverters. But keep in mind that the voltage should be higher than the voltage of your battery bank.
A close look at Inverloch
February 24, 2010I understand that a writer/artist has free reign to make a story any way they choose, especially if it’s for themselves. But as an outside reader, it’s no fun to vomit up something that tasted so good.
I suppose you could say my article has plot spoilers, but I think it’s more fitting to say my article is a plot warning. I suppose you could also say my view is “skewed” by my Christianity, but this is way beyond me: “At the end of the story, there is a main plot-twist that most fans of the comic hated” (WikiFur). The ending is hardly a plot twist as it is a plot train wreck.
My First Read of a Graphic Novel
Inverloch was my first time to read a graphic novel. To my dismay, it might be the worst. I’ve seen a lot of movies and played a few games. I admit that I haven’t read many regular novels, but I don’t think anything has completely let me down as much as Inverloch.I don’t doubt that some people liked or even loved the story. Maybe even you figured it out before the end and still enjoyed it. If so, you’re probably missing a big part of the picture concerning prejudice and racial segregation.
I like the style and layout. I like the few numbers of panels per page and the backgrounds. I love the characters (or I did). But being deceived from the very beginning and learning the truth at the end really breaks the scales. Learning the truth is a good thing, but it hurts to learn the basis of the story is built on a lie.
The Buildup
Official Description
Let’s read the description straight from the site (also see description on Kidjutsu):“The story of Inverloch centers around a young man named Acheron, from a horned wolf-like race called the da’kor. After a chance encounter with an elf, he finds himself setting out on a seemingly innocent mission - that of trying to locate Kayn’dar, another elf who has been missing for the past twelve years.
Meeting up with new friends and companions along the way, he quickly begins to learn that the world is not quite the peaceful place he believed it to be - embroiled with prejudice, racial segregation, and hidden danger. And the truth behind Kayn’dar’s disappearance is something none of the party would ever expect…”
Everything the novel seems to build up is essentially thrown out or never existed in the first place. Notice it mentions prejudice and racial segregation. This is built on early in the story.
Indicators of Prejudice and Racial Segregation
Here are a few excerpts (try to follow the context):- “We have something on an undeserved reputation…” (Ch. 1, p. 9, panel 3)
- “Oh! It’s just a cute forest animal.” later followed by “But da’kor… they’re horrid and vicious monsters.” (Ch. 1, p. 25, panel 1 (&3) and p. 26, panel 3)
- “You’re… not what I expected a da’kor to be like. I mean no offence, but everyone says how brutish and ill-tempered they are.” (Ch. 2, p. 8, panel 1&2)
- “Humans and elves hate us, fear us, despise us. All that does is breed the same feelings from the da’kor toward everyone else in return. …” (Ch. 2, p. 19, panel 1 (&3))
- “Shiara… I can’t change what I am…” (Ch. 2, p. 22, panel 3)
- “Naturally, the elves decided to blame the da’kor.” (Ch. 3, p. 8, panel 3)
What makes a person?
A far as I understand, a person’s personality makes them… them, their soul, their spirit. … You’re lead to believe Acheron is a da’kor (Ch. 1, p. 9). The reality is, the Acheron you’re introduced to is Kayn’dar, an elf in a da’kor’s body (Ch. 24, p. 11±1). The real Acheron at this time is actually a da’kor in an elf’s body, Kayn’dar’s body.Acheron’s Mother and the Other Da’kor
Did Acheron’s mother really know all along?
It’s strange that Acheron’s mother herself seems oblivious that “Acheron” is actually Kayn’dar, leading us into complete deception (Ch. 2, p. 3). She also says “You have such a kind heart, Acheron,” (Ch. 3, p. 12, panel 5), but supposedly she knows he’s not really his son. Is she trying to continue Kayn’dar’s deception?Acheron’s mother also says “There never was or will be any other da’kor like you,” (Ch. 3, p. 13, panel 2). Well, that’s certainly true of the body anyway, the only da’kor attribute, (and maybe some memories retained by the real Acheron). But the actual person isn’t a da’kor, it’s an elf who’s name is Kayn’dar.
Where did her hopes lie?
Consider that if Acheron’s mother did indeed praise “Acheron” knowing he was Kayn’dar, was her faith in the elves? It certainly seems like it (Ch. 24, p. 22, panel 4). I don’t think it could be said that she had any faith or hope in her own kind, the da’kor.Did she regard her real son?
We later see her “lament” her son’s brutal death: “He was always such a foolish boy…” (Ch. 24, p. 23, panel 1). The supposed irrevocable love between a mother and her child is severed. She simply dismisses her authentic son as a fool without pity. She was even presented with options (Ch. 3, p. 15), but didn’t seem to care. Even Varden sheds a few tears, for his father (Ch. 11, p. 30 & 31).So, the elves gain leverage through Kayn’dar who is rightfully praised as Acheron’s mother admits, “I was expecting to raise a rude and conceited child, but…” (Ch. 24, p. 23, panel 2-4). Unfortunately, this way by which the da’kor could change their minds about elves, is limited to Acheron’s mother and a select few da’kor. It’s interesting to note that these da’kor initially did this to save their own race (Ch. 24, p. 23 & 24).
Acheron’s mother seems to care about the da’kor as a whole (Ch. 24, p. 24), but it seems her son was just one of the numbers, nothing special.
Parenting
Why was Acheron foolish in the first place? … I’ll let the subtitle infer what you probably thought I had in mind. However, it doesn’t seem that Acheron’s childhood was really that bad (Ch. 2, p. 13). This brings into question whether the author actually knew which direction she wanted to go.Is there hope for the da’kor?
Maybe if the da’kor, even a few, changed themselves and stopped killing humans (Ch. 1, p. 12), they wouldn’t loose their numbers to humans (Ch. 24, p. 24). What better example could be set than one willing to risk life and limb to save one of another race, in public? Since “Acheron” traveled, his quest became known, his reputation was being built (Ch. 5, p. 24, Ch. 8, p. 19-22, Ch. 9, p. 20).What a lesson it would be for those of other races (along with the da’kor themselves) to learn what this “da’kor” did (or could have done) to save the elves, an act of selflessness. Acheron could have corrected a misdeed of his own people. But when it’s discovered that “Acheron” is an elf, (essentially reflecting an elven personality), imagine the mindset of all the elves who are prejudice, not Kayn’dar. I can almost hear some conclude, continuing the stereotypes against themselves:
- “Oh, Acheron was really an elf. It all makes sense now. No wonder he was so kind.”
- “Acheron was really an elf? The world needs to know he wasn’t really a dreadful da’kor.”
- “Does Kayn’dar really think there’s hope for the real da’kor? He never really was one of them.”
What about the author?
The one thing that really seems confounded is the real Acheron himself, living in a elven body, calling himself Silvah. He didn’t even seem to recognize his own body. This seems to be vaguely hinted (Ch. 18, p. 7-10, p. 24; Ch. 20, p. 19), but it also enables the author to take an undecided direction, even up to the end of chapter 23. But even given that, why would he trust Neirenn, who he knows to be against (or at least suspect) him, to shout “Behind you!” essentially causing him to destroy his own body (Ch. 23, p. 23 & 24)?Sarah Ellerton supposedly wrote the script before the drawing process. She said in an interview with Janet Houck, “The script hasn’t changed too much - the plot is basically the same…” But then she goes on to say, “The only major change I made since the first draft of the script was the ending, which was almost completely rewritten just before I started drawing.” (Inverloch’s Sarah Ellerton Tells All)
As far as I understand, usually the ending determines the conclusion of the whole plot. While most of the original script may be essentially the same, it’s meaning can change dramatically. It’s hard to rewrite the end without considering the whole. But then you’re left to wonder, what was the original ending? We may never know.
It’s interesting to note that her general inspiration seems to stem from Disney animation features. She also says, “I love simple, light-hearted fantasy stories more than brooding war-centered epics,” (Inverloch’s Sarah Ellerton Tells All). I don’t know about everyone else, but when I discovered “Acheron” wasn’t Acheron at all and his own mother lacked pity for the death of her own son, my heart fell into a pit (so-to-speak).
Driving a Wedge
The resolution reached doesn’t seem to stop or even slow the continuing prejudice and racial segregation against the da’kor or the elves. Unfortunately, it seems to compound it. In essence, the conclusion of the novel gives me no good reason to necessarily dispute the prejudice associated with the da’kor initially introduced. It’s so far from being resolved, it actually gives me a basis for it (back at ground zero).Acheron’s father’s generation didn’t seem to change (apart from Acheron’s mother and a few others). Acheron or his brother showed no change. Is there any example for the new generation? … I think I’ll steer clear of the da’kor knowing there’s none like Kayn’dar, the elf.
My Concluding Thoughts
I’d rather Acheron had been a martyr that was the catalyst to restoring “Kayn’dar’s” memory (as it seemed) than continue the reputation of his race as an untrusted people (as in Inverloch’s reality). … This would mean a change of Neirenn’s character as initially expected (Ch. 10, p. 28).But aye, it’s a cruel world now innit? Why else would the elf and human who embarked on Kayn’dar’s journey go steady to a life of crime (Ch. 25, p. 25)? Who’s to say Acheron’s mother isn’t really a human?
I will soon read Batman: The Dark Night Returns and Kingdom Come as part of my sci-fi & fantasy literature class. I doubt my experience will be at all bad compared to Inverloch. I know that I have also disappointed readers by discontinuing my own Set Apart series, but I didn’t destroy what I planned to build up. I admit my failure to plan properly.
Choosing a charge controller
February 21, 2010Solar panels and wind generators produce electricity, but their output varies widely based on the available sun or wind speed. Therefore there is a need to convert that output to something a little more consistent using a charge controller.
Do I need a charge controller?
Generally, you will not need a charge controller if you simply plan to sell power back to the electric utility company. You will need a charge controller if you plan to:- use batteries
- use an OutBack Power System (which requires batteries)
- use solar and wind power in the same system
- go off-grid, independent from utility power (usually a mobile or remote home)
- have a backup power source during outages (which requires batteries)
- power a portable inverter or otherwise large device (requiring a significant battery source)
What kind do I need?
There are almost as many different types of charge controllers out there as there are solar panels. However they all essentially do the same thing, which is charge batteries. The most common battery type used is sealed lead acid (SLA) or gel lead acid, which is very similar to SLA. Click here to see more.If you plan to use wind generators, the charge controller is usually built into the unit or comes with it separately. Therefore, you don’t need to worry about choosing a charge controller unless you plan to make your own wind generator.
What you need is largely based on what you plan to power and how often you plan to use it. In my article about choosing solar panels I discussed calculating power:
- V (Volts) * A (current in Amps) = Power (Watts)
How do I connect it?
Connecting a charge controller is fairly simple. There are usually two things to connect, sometimes three. You will always have to connect the solar panel(s) and the batteries. The labeling is fairly explicit. Consider these and look at the pictures:- SunGuard 4-12V charge controller
- Prostar 15, 12/24V Charge Controller
- OutBack FLEXmax 80 Charge Controller
Don’t be intimidated by the FLEXmax. It also has two simple connections, PV +/- and Bat +/-, it just requires larger wire. The FLEXmax is generally used in larger solar systems.
Wiring details should be outlined in the instruction manual for your specific charge controller. I’ll try to cover wiring in more depth at a later time.
Will incandescent lights die?
February 20, 2010There’s been a lot of advancement in the field of lighting, particularly solid state lighting with LEDs, but that doesn’t necessarily mean incandescent bulbs will phase out. Consider that they were probably conceived as a way to replace candles, and they excel at that, (heat and light). Also, candles haven’t phased out.
Today’s Applications
Incandescent lights still have a place in the modern world, but not necessarily as a lighting source. They produce light, but most of all, they produce heat. Here are some modern day applications:- Heat Lamps (more examples here and here)
- Reptile Heating and Lighting (more examples here and here)
- Incubation (more examples here and here)
- Easy Bake Oven
- Scentsy (a flameless scented candle)
- Plant Grow Lights
Give Me Heat!
It’s been said that only 5% of the energy going into incandescent light bulbs results in light. 95% of that energy results in heat. I see no reason to refute this, they get hot! Now that’s efficient… for heat production.Other places where people would prefer incandescent bulbs over the newer bulbs would be in cold locations or climates. If you move from Texas to a northern state, you’d probably prefer more heat. If you’re working outside on a cold winter day, those hot halogen work lights feel pretty good.
What about the Energy Independence and Security Act of 2007?
Some might be concerned about the federal bill that phases out incandescent light bulbs between 40 and 150 watts. (See Subtitle B, Sec. 321 in the full text.) However, there seems to be enough exceptions that a simple relabeling could probably circumvent such restrictions. Just because “incandescent light bulbs” may not be sold doesn’t mean “heat bulbs” can’t be sold.Then there’s the burning question of “who is the government to dictate what bulbs I can’t use?” I find it particularly disturbing that the government would do this (among many other things). But, I look forward to LEDs being used in lighting applications, because you get more light per watt of energy.
Reusing the CFL circuit base
February 18, 2010For you hobbyists out there wanting to reuse the parts from a burnt out CLF (compact florescent light), there are some ways to reuse the circuit in the base. With a few steps I’ll show you how to wire up a small florescent light to take it’s place.
Know what Failed
CLF lamps may fail because the filament in the bulb burns out, just like regular incandescent bulbs. If this is the case, the bulb doesn’t produce any light. If the CLF filaments at the base light up, but the rest of the bulb doesn’t, the electronics failed. This means you could use the base of another broken CFL to repair it.Open the Base
First you need to get it open. Some are fairly loose and you can easily use a flat tip screwdriver to pop it open. You might have to use a hacksaw on others and then use a screwdriver. Be careful not to break the bulb.Get to the Circuit Board
Once you have it open, just lift out the circuit board. Next, cut off the wires from the bulb at the circuit board. If you had to use a hacksaw, you may have to cut the wires from the bulb first and then pop out the plastic ring you sawed off.Get a Bulb, Wire It Up
You saw two wires coming from each end of the bulb, right? Now, just get a small florescent light (like one found in a modern camping lantern) and connect it the same way as the other bulb was connected. At this point you probably realize that a compact florescent light is simply a florescent light.Turn It On
Once you have everything connected, turn it on and see if it works! Assuming your bulb is good, there shouldn’t be a problem and it should turn right on. Be careful not to shock yourself!More Experimenting
Try some different types of florescent bulbs and see what works best. Try some in series. Just keep in mind that the filaments at the ends shouldn’t be brighter than the rest of the bulb. They also shouldn’t flicker. If you observe this, you may be using excessive power to light the filaments than the whole bulb requires! Try a smaller bulb.
Is it on, off, or idling and how to tell
February 17, 2010I’m sure most of you have heard or read that some appliances still use electricity when they’re “off.” There is no doubt this is true, but how can you tell? Identifying what’s idling and what isn’t (without paying money for something like a Kill A Watt Monitor) is a good first step.
How much energy is really being wasted?
An idling appliance is something that uses electricity when it’s “off.” When “off,” they could use anywhere from about 5 to 25 watts. Usually these appliances have internal clocks or settings. Unplug the appliance if you don’t care to keep time or settings you may have saved.A disconnected cell phone charger, laptop power supply, or any external power supply not connected doesn’t need to be plugged in. Depending on how they work, they could use anywhere from 0 to 10 or more watts.
Here are the results (in watts) of some measurements I took:
- Nokia cell phone charger (not connected):
0W - Laptop power supply (not connected):
2.5W - Ethernet router power supply (not connected):
8.9W - Cassette deck, “standby” (it’s not labeled “off”):
2.5W - VCR/DVD player, no clock, completely “off”:
5W - Older PlayStation 2 turned “off” from the front button:
6.3W - Older PlayStation 2 turned off from the back switch:
0W - Computer, completely “off”:
10W - Older VCR with clock, completely “off”:
13W - A Sony stereo system with disc changer, cassette deck, and clock, completely “off”:
25W
How can I tell if something is idling?
Common Indicators:
- Lights or a display is still on and working
- It hums or makes any noise when you put your ear right up to it
- It can automatically turn itself on (as through a timing function) if it’s “off”
- It is warm to the touch due to power dissipation
Typical Appliances that Idle when “Off”:
- Desktop computers made after 1995 (or after ATX was introduced)
- Laptops
- Computer monitors and TVs
- VCR/DVD/Blu-ray players
- PlayStation, Xbox, Nintendo, and other gaming systems
- Satellite receivers
- Cell phone chargers
- Answering machines
- Anything that has an external power supply
- Anything that keeps time
Push-Button Switches
Another way to tell if an appliance is idling is by the power button or switch. If the power button is small and requires a gentle push with a subtle “click” or “tap” sound, it likely idles.If the power button feels heavy duty, making a “click-cling” or a “click-clack” sound, it probably doesn’t idle. This is because these switches usually switch the wires straight from the power cord. It’s the equivalent to unplugging it. This is common in much older appliances, especially stereos and amplifiers.
Toggle Switches
If you have an appliance that has a toggle or flip switch like a power strip, it probably doesn’t idle. However, if the switch is small, thin, or light, it might use idle power.Too Much Hype?
Another point I want to get across is don’t be too optimistic. Most idling appliances use very little electricity. Also, new power supply designs continue to increase in efficiency during idle time. Consider that a laptop or cell phone also uses idle electricity when it’s completely “off” (unless you have no battery).Air conditioners and heaters make the meat of your electric bill, not idle power or lighting. Unplugging any one appliance will probably make a negligible difference. It’s when you have several that they have an impact.
Turning off a power strip to everything you’re not using is a good idea. Even the Smart Strip uses some idle power. If you’re still using any incandescent light bulbs, you’ve got a slightly bigger problem than idle power.
Choosing solar panels
February 16, 2010There’s a lot of different solar panels out there, and with so many choices, it would be helpful to know what to look for when buying one. I’m going to explain some of that technical jargon. This way you can better understand how or what panels to use with a given system.
Understanding the Spec./Data Sheet
Let’s say you want to check out a specifications sheet for a solar panel, like this one or this one. As you start looking at the tables, you’ll see terms like:- Polycrystalline silicon (or Multi-crystalline silicon)
- Monocrystalline silicon
- Open Circuit Voltage (Voc)
- Maximum Power Voltage (Vpm) (or Optimum Operating Voltage)
- Short Circuit Current (Isc)
- Maximum Power Current (Ipm) (or Optimum Operating Current)
(As we discuss these terms, keep in mind that voltage and current measurements are usually taken under a consistent test light source. The results should be comparable to good sunlight.)
Vpm and Ipm
These are the most important aspects of the solar panel because they determine power. Both Vpm and Ipm are the ideal maximums at which the solar panel functions. Looking at Ohm’s Law, we know that:- Vpm * Ipm = Power (Watts)
This may seem trivial and basic for some of you, but the point is that you need to know what is being advertized. What is a “12 volt” solar panel? Is it 12 Voc with about 9 Vpm? Or is it 12 Vpm with 18 Voc? I admit, it’s usually the latter, but you need to make sure.
MPPT - Maximum Power Point Tracking
Both Vpm and Ipm establish the maximum power point. When you see a charge controller or grid tie inverter, they may advertise a MPPT (maximum power point tracking) feature. All this means is it searches for Vpm and Ipm to get the most power from your solar panel(s).Voc and Isc
Consider Voc and Isc as the opposite extremes of Vpm and Ipm. Generally, you don’t really need to worry about these. You won’t get any power output at these extremes.Open circuit voltage, or Voc is the voltage measured when the panel isn’t connected, hence “open circuit.” Short Circuit Current, or Isc is the current (amps) measured when the panel is completely shorted, positive to negative.
Poly-crystalline vs. Mono-crystalline Silicon
This makes up the composition of the silicon used in the solar cells of a panel. Silicon is the same material that make up computer chips. You don’t really need to worry about the raw materials that make up a solar panel. But for your interest, here are some key differences:| Composition | Cost | Efficiency | Appearance |
| Poly-crystalline | less | less | usually rectangular or square without rounded corners |
| Mono-crystalline | slightly more | slightly more | usually square with rounded corners |
Buying a simple grid-tie solar system
February 12, 2010If you’ve done any amount of home improvement, then setting up a simple solar system isn’t a challenge. However, it would be good to know a few basics and what parts you need.
Please keep in mind you may have to contact your power company to learn specific code requirements. Where I live, our house wasn’t required to be wired to code; therefore I simply discuss what will work from a technical standpoint.
Jump in Head First
If you want to jump right in and buy a simple low cost package that outlines all the details, here they are:- ASG Power Plus 0.2 kW GT Kit
- ASGP+ Enphase Grid Tied Starter Kit - 175 Watts
- Hi iQ Telecom Ltd (eBay store)
How These Systems Work
These systems are very simple. Think of it as battery charger working in reverse, except the battery is the solar panel. A solar panel is connected to the inverter, which is connected to your breaker box. The inverter is “charging” your house using the solar panel “battery.”If you’re familiar with inverters used in cars for laptops, they are very similar. However, there is a serious difference between a grid tie inverter, and a basic inverter. A grid tie inverter synchronizes with the frequency (60Hz) and phase of the voltage from the power company. (Think of it as two people flipping a switch at the same time, in the same direction.)
Buying Parts Separately
The essential parts you need for a simple grid tie system is a solar panel and an inverter. You need to consider both items at once for a complete working system.Inverter
The inverter is what converts the input VDC (voltage, direct current) from the solar panel to the output VAC (voltage, alternating current) to your home. You need to consider voltage, both input and output. This will determine the voltage of your solar panel and how to connect it in your breaker box.Good inverters can work with a range of voltage input, like 10-30 volts DC or 40-60 volts DC. Output voltage is usually ~120VAC, ~240VAC, or ~208VAC. You need not worry about the last one, it’s for commercial three phase power systems. Check out my article Is solar power really affordable? for additional information.
Power Source
Solar panels come in lots of flavors and output voltages vary widely. (See my article about choosing solar panels for details.) Here’s a list with some common voltages according to open circuit voltage (Voc) and optimum operating voltage (Vmp):- ~18Voc (12Vmp)
- ~36Voc (28Vmp)
- ~58Voc (47Vmp)
- 12V
- 24V
- 48V
Hardware
As for mounting hardware, you could use angle iron or angle aluminum usually available at a local hardware store, Lowe’s, or Home Depot. Wood or angle brackets are other options, but I recommend against duct tape.If you go with a wind generator, tower kits are usually sold separately. You may also have to buy galvanized steel pipe for a guy-wire tower kit. See some examples here.