Here’s a really helpful article from Eddie about solar power and how to make it work for you.
An awful lot has been written about generating electricity from solar photovoltaic panels. It would be easy to get into arguments about whether solar PV’s are truly “Green Energy” (whatever that really means), what their true EROEI is, how long it takes to recoup your investment vs. buying grid power, and so forth, but that isn’t the purpose of this post.
My point of view is that solar PV’s are available, that they represent a reasonable if somewhat costly alternative to grid power, but that the current instability in our political and economic systems might make them look downright affordable in the long run.
They also represent a way to wean yourself off off the currency, because once a system is installed and functioning, you can go for years, perhaps for the rest of your life, without paying an electric bill. That appeals to me.
Solar PV’s do have limitations and problems. They are essentially big semi-conductors, with environmentally toxic materials to somehow dispose of at the end of their useful life. (Most panels a have a guarantee to be a 80% of original power output at 20 years, but the useful life of a system might be much, much longer). They are fragile and can be destroyed by a big hailstorm or a tornado. They can be stolen. They are complex technology. If they break, you probably can’t fix them. If we have an EMP attack, the only solar panels that likely will survive it are those that are stored in a shielded metal building , not being used. Most importantly, perhaps, there aren’t enough resources on the planet to build enough panels to come close to replacing the fossil fuels we use now to generate electricity.
But when you have some solar panels, and they work, they make electricity from sunlight, which is a free resource at the moment. There aren’t very many free resources left.
In my own prepping saga, a few years ago I became aware of the Transition Movement, which as you might know, is a world-wide movement aimed at helping individuals and communities work toward self-sufficiency in a scenario of declining fossil fuels. The purpose of this article is not to talk about Transition , but that is where I ran upon the concept of what they call an EDAP, or Energy Descent Action Plan. This concept involves communities figuring out how to learn to live with less and less dependence on the existing long chain supply lines as they inevitably break down when the wheels come off our “cheap oil” based systems of agriculture and commerce.
I decided it was a good idea to have my own EDAP, for me and my extended family. In central Texas, where I live, we have lots of sun, and a lot less running water and wind, and so my attention became focused on solar PV’s as a way to achieve some energy resilience.
I was excited to learn that significant tax incentives still existed to help cover the cost of going solar, although as I became more educated, I learned that most of those benefits were intended to be given primarily to homeowners who were willing to participate in a regimented, government and utility company sponsored system that funneled much of the money to middle men, the licensed installers who were designated by the utility providers. As is the case with most government handouts, somebody was making some money on the deal
I found out it was (and still is in my state) impossible for me to put in a grid-tie system (the kind that allows you to sell your excess production back to the power company) without my system being designed and installed by one of the companies on the utility company’s list. Fortunately this is not the law in every state.
The Federal Tax Credit, extended to 2016, does still give a 30% tax credit for ANY system, the year it’s placed in service. This is not limited to grid-tie systems. A tax credit is a dollar for dollar reduction on your actual tax bill, so that’s far better than a deduction. There is no ceiling on the Federal tax credit, btw. Some states and localities offer other tax breaks.
Grid-tie systems are a mixed blessing, with pros and cons, but there are two very positive attributes to grid-tie systems. One is the one I already mentioned, that you can shift from the position of being an energy consumer to that of being a producer, and get paid (usually at a very low less-than-wholesale rate, but this also varies by state) for the excess energy your system puts out, if any. The second, perhaps more valuable attribute is that grid-tie systems do not require batteries, which are the most expensive and short-lived component of any off-grid system. (A third benefit, which I won’t dwell on here, is that grid-tie systems allow the use of micro-inverters, which essentially can give you a solar panel producing 120V AC right at the panel, with no DC wiring runs at all. This greatly simplifies the wiring of the system.)
There are downsides to grid-tied systems. The most glaring problem is that they won’t function when the power grid fails (unless they have batteries and have been specifically designed to switch to off-grid when the grid loses power).
So…my own desire to be self-sufficient and not have to kiss the utility company’s ass eventually led me to look at stand-alone, off-grid systems. This is what I want to talk about in this article.
I’ll talk about the components of an off-grid system. I’ll discuss the significance of a low voltage vs. a high voltage system. I’ll discuss battery options. I’ll talk a little bit about various free resources on the web that help in computing things you need to know, and I’ll talk about educational resources. In fact let’s start there.
Unless you happen to be an electrician or an engineer, you probably need to get some training before you attempt to build a system. My first inclination was to scour the net for free articles and visit Youtube University. So I did, and here is my take on what’s out there..
While there are many, many great Youtube videos posted by folks who have built PV systems, there does not exist a good straightforward start-to-finish “how to” on building a PV system. And many internet forums dedicated to alternative power are dominated by professional engineers who aren’t necessarily eager to share everything they know.
Books on solar power tend to be like computer books. After a couple of years they are so out of date that their best use is for mulch in your garden.
There are two resources that are timely as of right now that I would recommend to anyone who wants to learn how to do this stuff.
There’s one good book “Photovoltaics Design and Installation Manual” copyright 2004, put out by Solar Energy International and published by New Society Publishers. It has workbook pages for you to practice making schematics of systems, which helps you learn how to wire both panels and batteries to achieve the correct voltages for various systems, which is an essential skill.
The second resource is even better, and it’s a video series by Green Power Videos, run by Bob Nagy, a teacher who teaches solar installation at an Arkansas community college. This series was conceived as a complete how-to course, and comes very close to being an all-in-one guide to building an off-grid system. I paid about 50 bucks for these CD’s and I’ve watched them repeatedly, which is what’s required for a lay person to absorb all the details. I don’t know Bob, but I’d like to meet him sometime and thank him for his work. His videos get high marks from me.
In addition to those sources, I’d add one more, which is a recent article in Home Power Journal (Feb-Mar 2013) titled PV Preflight, written by Bill Hoffer. This article talks about the exact process by which a new system is safety checked before being place into service. Good stuff to know.
Electricity is potentially dangerous, particularly high voltage systems. So you need training, and you need to pay careful attention. Be safe. Working on PV’s requires insulated tools and gloves and clamp type volt meters that let you test circuits indirectly without touching leads to bare wires. Systems should generally be powered down when you’re working on them. You need to be able to check that they are, too.
This is a good segue into the subject of system voltage. Old school solar power generally meant a 12 volt system. One good reason for that is that 12 volt DC systems have a measure of safety not shared by higher voltage systems, which is why they were chosen for the electrical systems of cars and pleasure boats in the first place.
However, low voltage circuits require proportionally larger diameter wires (unwieldy and expensive) to carry the same amount of current that high voltage systems do. Unless you live on a sailboat, in an RV, or maybe a tent, then a 12 volt system is probably not what you are looking for. (There may be some exceptions, such as a system used in a house just to run very low amperage LED lights, for instance.)
For a system that will run the typical modern house, with all its many appliances and devices, it is usually more practical to run at 24 or 48 volts on the DC side of your system. This allows you to use smaller, cheaper wire, giving you more leeway in how far your panels are from your house, for instance. Panels can be purchased readily in 12 volt and 24 volt . By understanding how to wire them in series and parallel, you can up the voltage to whatever you need. Battery voltage doesn’t always have to match panel voltage, but always has to be the same or lower voltage than the voltage of the panel array that charges it.
Confusing? Well, maybe it’s time to talk about the various individual components of a system, and how they work together to give you juice at the plug in your house. That will help you get clear.
The parts of an off-grid system are:
1. The panels, or panel arrays (multiple panels wired together). They make the electricity, delivering it at a particular voltage of DC electricity.
2. The charge controller, which is a sophisticated electronic battery charger, keeps your battery bank charged within an optimum range. This is important for both power output and battery life. A DC circuit connects the panel arrays to the charge controller.
3. The battery bank, which stores power so you can run your lights at night when there’ s no sun. The batteries also are DC current, and sit in a circuit between the charge controller and the inverter.
4. The inverter, which converts power from your batteries to AC current to run your refrigerator, air conditioner, washer, dryer, stove, microwave, hair dryer, etc..
(Of course you can buy many devices that will run on 12 volts. A system can configured to deliver 12 volt DC current to special plugs in your house in addition to providing normal 120/240V AC current.)
In addition to the electronic components and batteries, there are wiring runs to connect them and to deliver the output of the system to your house There is always a switch and a fuse or breaker between components. There are grounding requirements both for the external frames of the array and whatever rack it’s mounted on, as well as for the electrical circuit that goes to your house.
My goal is that anything I build for myself will be meet code, and that at some time in the future I can hopefully convert my off-grid system to a grid-tie with a battery back-up, because I’d like to sell power. But that depends on TPTB and their rules.
Charge controllers are always evolving. MPC controllers are the state of the art, and more efficient than the older technology, which means you get significantly more power from your panels to use as you see fit. They are more expensive, but worth it.
There are choices in inverters. The more panels you have in a system, the bigger inverter you need. There is usually no need for more than one inverter for a smaller home type system, but sometimes two are used for resilience, since if your inverter ever fails, then you would have no AC power at all. With two smaller inverters rather than one large one, if one fails you have one (hopefully) still up and running.
The more expensive inverters deliver their AC power in a true sine wave frequency, which is important to get things with motors (fridge, air conditioner) to run right. Lights can run on modified sine wave frequency. Modified sine wave inverters are pretty cheap now, so sometimes it’s nice to have one just for lighting.
One important point. You can have an off-grid system running in your house separate and apart from your existing power. You can have plugs from your system dedicated to whatever you want. You could design a system that say, powers your refrigerator, your pool pump, or just lights. It just can’t be wired into the grid, if you built it, most likely.
On buying panels. Panels today are available in 12 volts, and 24 volts for the most part. Wattage (power) typically ranges from 200 to 250 watts per panel for a 24 Volt unit. When building an array it’s important for the panels to have the same power output. Generally, the more power output per panel the better, because you’re always ultimately limited by the amount of space available for your array.
I have purchased panels online, and the experience has been a little mixed. The problem is that they typically come to you by freight, and they are somewhat fragile. I have seen some banged up pallets of solar panels. It might be better to buy them locally if you can get a good price. Right now panels are selling at $.75 to $1 per watt, depending on which panel and how many you’re willing to buy.
Batteries. Most people use high end industrial lead acid deep cycle batteries. They generally can last 5 to 7 years if they are kept filled with electrolyte and charged properly, which is a big if. Solar PV systems require some minor maintenance and must be monitored. You can get sealed gel batteries if you need to keep them indoors and can’t vent them.
Another battery option, at significantly higher front-end cost, is the Edison cell. These batteries are an iron/nickel battery that uses potassium hydroxide as an electrolyte. These batteries can last an awful long time (25+ years), and they can be abused a lot more than lead acid batteries. Until very recently you could only get new ones from China, but they are now also being produced in the US again.
Battery technology is one area that is changing. Soon, carbon nanotube batteries may revolutionize solar power. The technology already exists, but as of now, they are not widely available.
How big a system do you need? Lots of calculators are available online that let you add up the power used by various devices, so you can design a system that gives you the power you need. You can look at your electric bill and quickly calculate how much power you use in a day.
Or conversely, you can build whatever size system you can afford and learn to live on what you make. Most people who really do live off-grid learn to live on a fraction of the power most of us are accustomed to using.
Most systems are not readily scalable. It’s hard to add on to a system. Panels need to match. Lead acid battery banks need to be placed in service so that all batteries in a bank are the same age. You can add on to a nickel/iron battery bank, however. Using a high end inverter and charge controller gives you more options on adding additional arrays and battery banks to an existing system, or even adding wind or water power to your home power system.
There are lots of other online resources that can tell you things you’ll want to know, like the proper alignment of a panel for you latitude…and exactly how many average hours of sunlight your locale receives in a day.
Panels, of course need to be in the sun all the time if possible. Depending on what kind of charge controller you have, you may lose power from every panel if even one is shaded.
With the exception of batteries, solar power has gotten an awful lot cheaper over the past five years. I don’t expect the prices to stay down forever. I encourage absolutely everyone to build at least a small system, something that could power your computer, a 4G modem, and your radio and TV in an emergency. It doesn’t take much to do that.
I hope this has been helpful. Please give me your questions and comments.