Independant (non-grid-intertie) solar electric system

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Most of what I write isn't relevant to Instructables.  My main blog is here:
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Most solar systems installed on houses are hooked up to a special electric meter which can both draw on the grid and feed back into it - which makes the meter run backward.

That is pretty cool!

However, these systems generally run from around $25,000 to $50,000 and take anywhere from 10 to 20 years to make up for their up front cost in reduced utility bills.

My solar photovoltic system is independent of the utility company.  It cost me about $400 (unless you happen to live in an RV, boat, or cabin, it will cost you just a little bit more)

I still use traditional electricity for some things, so I still get a bill each month, but it reduced my electric bill by almost $15 a month, which means it will pay for itself in a little over two years.

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Step 1: Reduce demand

Picture of Reduce demand
The first step for any type of solar system is to find ways to dramatically reduce the power you use in the first place.

My previous instructable is a great place to start:

These are steps you should be thinking about doing anyway, but it becomes all the more important when doing a solar electric project.

This is because solar systems (whether grid-intertie or not) are priced by the kilowatt.  The fewer you need, the less your system costs, and the sooner it pays for itself.
JPcreo7 months ago
This is a great instructables with lots of info. Thanks.
I have just bought the 45W solar panel kit from Harbor Freight. It would be for fun for now.
Akmal2501 year ago
hi, thank you for your great information
i need to some details for solar system
first one
bulb -10
fans -04
Air conti-01

how many watt this want?
but this also 220V .
please tell me
JacobAziza (author)  Akmal2501 year ago
Your question does not have enough information.
You didn't say the wattage / amps of any the loads. Every light bulb, every appliance, every TV, AC, etc, all have different power requirements, and there is a HUGE range.

I don't know what country you are in, but in the US household current is 110-120V. NOT 220. The only things that use 220 are electric clothes dryers and water heaters.

But in any event, it is impractical to run any household appliance on 12V solar power. You need to either use 12V lights, electronics, and appliances, or use grid power. Most households with solar systems are not actually using their own solar panels, they are using grid power and off-setting the cost by putting energy back into the grid with the solar panels. There are a lot of guides out there if this is what you are looking for, but this doesn't happen to be one of them - this is about small scale independent solar
vandejake2 years ago
Great instructable, i have been doin a lot of research on solar and have begun my collection of panels, if you live in Canada anywhere near Toronto (save delivery charges) SAW Technologies is the place to get your panels, I got a 245W Panel with charge controller and wiring for less than you would normally pay for just a 70W panel, check them out send them an email for an entire price list and lets get off the grid!!

I have the same kit on my barn. Works pretty good. I can run smaller tools from it. Oh, yeah it was me who you helped on :) Thanks again.
ewookie2 years ago
Your chest freezer should be more efficient than the fridge. You could try lining the bottom of it with bags of ice or water-filled jugs. Then turn it to it's lowest cooling setting. I've even seen plans on the internet to convert a chest freezer to DC and use it as fridge.
in China the solar panels normally less than 2 dollars per watt, I used to work in the factory and the aircraft are excellent.
DarkStarPDX2 years ago
"I found some solar panels in a kit from Harbor Freight that cost just under $4.50 / watt, which is much lower than average. It also includes the charge controller, wiring, mounting frame, and even a couple of 12v lights."

Just found a good source this morning, Platt Electric is selling the 225 watt SolarWorld Sunmodule series panel for $374.22 each (or about $1.66 per watt).

These panels run at 29 volts nominally though, so you would need a charge control system that can regulate the voltage.
in China the solar panels normally less than 2 dollars per watt, I used to work in the factory and the aircraft are excellent.
JacobAziza (author)  DarkStarPDX2 years ago
Yeah, actually $4.50 per watt isn't unusually low for a stand alone solar panel- $4.50 per watt for a complete system (i.e. including the cost of mount, controller, and wiring). I should have been more specific.

Even so, $375 for a 225 watt panel is a great deal, and I would encourage anyone who could use a panel of that size (and voltage) to take advantage of it.

Thanks for the tip.
JacobAziza (author)  JacobAziza2 years ago
Also... I didn't actually pay that much! There was a larger sale at the time, for 3.70/watt, including controller, voltmeter, wiring and mount.

I have corrected the 'ible
sam D2 years ago
Hey Jacob, this is a nice instructable that shows the end to end process - fantastic.

I have been looking at ideas for simple solar concentration methods and have noticed some people are starting to put a square of reflective material on the ground in front of the panel as set up in Step 8. This causes more incidental light to reflect and hit the panel, upping the wattage.

I am about to do some experiments at home to see if it helps me make more power for my solar greenhouse.
"This causes more incidental light to reflect and hit the panel, upping the wattage."

This is true, however you are still limited by the wattage of the solar panel. In most cases, the amount of surface area used by a mirror would be better utilized by placing another solar panel in its place as this will increase the system wattage as a whole.
solar panel watt ratings are based on 1000 watts per square meter, if you increase that using a mirror, than the wattage goes up.
In other words, a 200 watt panel can indeed generate more than 200 watts if there is more than 1000 watts per square meter.
JacobAziza (author)  DarkStarPDX2 years ago
True, but (if it works), a mirror is a whole lot less expensive than another panel.
JacobAziza (author)  sam D2 years ago

The reflector idea would definitely help out for a green house (or solar hot water heater, passive solar heating, solar refrigeration, or anywhere else where you want to concentrate heat as well as light)

The problem with using a reflector in a PV (photovoltaic) panel application is that they are powered by visible light, not by heat, and a reflector can cause excess heat to build up on the surface of the panel, and the hotter the panel gets, the less electricity it produces (and the less long it lasts).

Although, it might not be a bad idea in the winter time, when temperatures are cooler and there is less available sunlight for power.
I'll have to look into that
caarntedd2 years ago
Thanks, nice work.
profpat2 years ago
great instructable!
sam D2 years ago
Actually, many people online are finding that the panel isn't the limit to the wattage, if kept cool. Folks on Youtube are using mineraloil heat exchangers on the back of the panel (left over cooking oil) to take the heat away and use it.

I am thinking of an inverted design where the panel is upside down over a parabolic trough, with a cheap bladder full of oil on the back. As the oil in contact with the back of the panel heats, it will rise up, causing convection currents within the oil. Might knock up a prototype.

As Jacob says, a reflector is usually cheaper than another panel.

JacobAziza (author)  sam D2 years ago
I could be totally wrong, but I would suspect that the main advantage to a reflector wouldn't be in raising the peak wattage, but rather in extending the hours of useable light each day.
For example, I have 5 hours of usable light on average. But the sun is up for about 12 hours each day. More than half of those hours aren't maximized because the angle of the sun is too low to capture the light. Having a reflector wouldn't necessarily help during the peak daylight hours when the sun is already hitting the panel directly, but it would capture some of the incidental light at other times, increasing the total watt hours the panel produced over the course of the day.

The more I think about it, the more I think I'd like to try it
This guy has heaps of solar augmentation on his Youtube channel. He comes out with a new idea every week.

I am keen to try the oil cooling idea....
SinAmos sam D2 years ago
Sorry, but there is nothing helpful about those videos.
I did some more thinking, and some modelling in sketchup to see if it really made sense. I think it does. Here's some pics:

I guess you could make the reflector 'wider' and you would extend the hours as you say above Jacob. And if you made it 'deeper' you would extend the wattage - although there is a relationship between the two.

JacobAziza (author)  sam D2 years ago
Seems like someone needs to write a new instructable soon...
ToniRose2 years ago
Thank you! I've been thinking for some time about the possibility of converting to DC as much as possible, but didn't know where to start gathering the information needed. And here you just hand it to me for free! What a gift. And Tom Edison is vindicated!

Of course, nearly all of the components of a computer use DC, with the converter/charge controller built into the AC power supply. (The display on a laptop contains an inverter to go back to AC - how much is wasted by that???) If that step could be eliminated, you could add your 'puter to the list.

Somewhere in my searching I came across DC plugs, male and female, that look very much like AC versions and can be installed just like household wiring, eliminating the "cigarette lighter" version. If I can find a link, I'll post it later.

All in all, you've provided great information clearly explained and tied together. Bravo!
Found it!

I admire and respect independent folk, but as a more urban-oriented type I'm looking for community solutions; think neighborhood or city block solar power stations rather than the extremes we have now --massive generation-transmission systems or self-contained pioneers like yourself. Any thoughts?
JacobAziza (author)  ToniRose2 years ago
I don't think there is much advantage to eliminating the "cigarette lighter" style plug, because the vast majority of things which use DC have that style plug by default. The ones you linked to are for specialty applications - namely, a house which is built 12v from the ground up, and has large 12v appliances (which you aren't likely to have if you are building a casual system like mine).

If you custom built your own DC application (like with a computer power supply) you could use any regular 120v 20amp outlet and it would work fine.

As to community level solar - in a way that is what grid-intertie systems are now, since they feed back into the neighborhood electric supply. I suppose if there were enough of them in a given area, its hypothetically possible that they could keep the block going in a power outage (assuming the mains were disconnected beyond the block)
Never really thought about that before.
Anyway, while I like the compliment, I am not really self-contained (nor a pioneer!), I live in the city and am still connected to the grid. I just tried to find a small scale compromise between the traditional way and going full solar.
JacobAziza (author)  ToniRose2 years ago
Your welcome!

As it happens, I spent about 20 minutes yesterday looking at different options for running my computer on 12V yesterday.
I have a laptop - which uses less power than a desktop; problem is that they need more than 12v. Mine runs on 18v. So a straight 12v cord won't work.

I found a few converters for under $4, but I'm concerned about their quality and safety features (or, rather, lack there of).
There are some for around $20 that look good, and I'll probably end up getting one.

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