4 Jan

2010

Do it yourself Solar System

Posted by easy eco blog

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solar panels, solar energy

Be sure to read our article Are Solar Panels for Me?

Do It Yourself Solar Part 1: The Design Process

For homeowners around the world, the idea of reducing their power bills and helping the planet is pretty enticing. The problem now as it always has been is money. Solar can be expensive, and even with government rebates the cost can scare some people away. If you are a do-it-yourself-er you’ve probably wondered if you can tackle a solar project. Let’s walk through a typical design and installation process and see if its right for you and your home.

Location Selection Basics
Well you’re probably smart enough to figure out that you’ll need A) a sunny region and B) a sunny place to install the system. The more sun you get, the quicker your systems will pay for itself, its that simple. There are some nice tools to determine where exactly you should put the system. The solar pathfinder is one of easiest and most affordable ways to find the best location for panels. This ingenious device works by showing you a reflection of the sky and the sun’s path for all four seasons in your area. Using this you can see exactly what will shade your panels throughout the course of the year.

You also want solar panels installed fairly close to your home and power meter. Since photovoltaic power is DC, the wire that carries it grows larger and more expensive the further away it is from the inverter, meter, and power center of the house. You’ll want a place close to the house but out of way of children and their errant soccer balls. Also if you are planning on installing the system on your roof, its worth it to do a roof inspection. No sense in installing a system if it will have to be removed in a couple years to replace the shingles.

Determining Angle and Azimuth
Generally speaking the closer you can get your panels to facing due south (or 180 degrees azimuth) the better. If you live in an urban area and are not sure which way south is exactly, use Google Maps to look up your address and click on the satellite image. You might be surprised to see that roof you thought was south facing is actually southeast facing!

The angle from horizontal is very important too. The angle should be equal to your latitude since this will mean the panels will be perpendicular to the sun for greatest amount of time. If you’re not sure what latitude you’re at, check out this latitude map of the US. So if you live in Portland, with a latitude of approximately 45 degrees, your panels should be set at an angle of 45 degrees from horizontal. IF your roof angle is within 10 degrees of you latitude you can mount the panels easily, if not you may have to consider a rack system that will tilt the panels.

Space Considerations
The rule of 1/10 is easy to remember for solar power. You’ll need 1/10 of a square foot for every watt you install. So if you want to install 2,000 watts, you will need about 200 square feet of space for panels, racking, wiring, and a little space to work around them. This will vary slightly by the type of installation and panels you get but this will serve as a guide for the time being. You’ll also need about a 4′x4′ area near the meter for the inverter, breakers, and power components. Keep in mind also that your power company may want to install a new meter or even an additional meter for the system.

Contacting the Utility and Building Department
Its always a good idea to talk to your power company about installing a system. You will probably need an interconnection agreement, an inspection, and a rate schedule if you are planning to sell back power. They’ll also want some information about the panels and inverter you are installing. Also, ask about additional rebates and an up to date cost per kilowatt-hour that you are paying.

You should also place a call to the local building department and ask about permits. This may seem like a pain, but really it protects you from hassles in the end. Eventually they’ll probably find out about your systems anyway and you may have to pay a fine for not getting a permit. The vast majority of inspectors will allow you to install a system on your own home, they may just require you to have a master electrician sign off on the installation.

Estimate Your Production
you’ll want to decide just what the system is going to produce over the course of a year. The National Renewable Energy Lab has a cool tool that will allow you to do this. With the information you’ve determined in the steps above, click on this solar map. Then find your area, and double click on it. You should see a data window open up with a link at the bottom that says ‘Send to PV Watts’. Click on that link, then enter the information we determined in the first steps for angle, azimuth, and cost of power. Also enter the size of the system you want in kilowatts. Click on the calculate button and you’ll see the production per month for a year. This can help you determine payback.

Finally: Determine a Budget
Possibly the most important part is deciding how much you can spend on a system. Most complete solar power kits cost between $4 and $6 per watt, depending on the size and racking system. Be sure to take into account all state, local, and utility incentive programs, which can be found here. You may even find a supplier that will take the rebates off the price of the system, then the manufacturer goes after the rebate. Sharp has a program like this.

Next we’ll determine what skills and tools are needed, and start planning the installation.

DIY Solar Part 2: Choosing A System
In Part 1 we started talking about DIY solar and covering the topics that will help you decide if you can do solar yourself. There are plenty of different systems that can fit your solar needs. Let’s cover the three most popular systems.

Grid Tied Solar
This is the easiest and most popular way to get started in solar power. These systems simply tie into your existing home power system and the utility grid. If your array generates more energy than you use, the energy is sold back to the power grid and creates a credit for you. The advantages of these systems are the relative simplicity and lower initial cost. A system like this typically requires a few panels, some wiring boxes and disconnects, and an inverter. The inverter converts the electricity from your panels to power that your home and the grid can use.

This system also requires an interconnection agreement with the local utility. This outlines just how the connection to the grid should be made and what the inspection schedule is. It is generally advisable to get your power company involved early on for a grid-tied system. Since there are often incentives and rebates in place from the state and the utility, it’s well worth the call.

Advantages of a Grid-Tied System

Initial Cost: The upfront cost of purchasing a system that would provide for a home’s entire electrical needs can be very high. With variable climate and weather conditions across the globe, the use of off-grid systems requires expensive batteries. Off-grid systems generally require a secondary power source, such as a gas generator, to provide backup power which adds significant cost to the system. Grid tied systems are much cheaper than off grid.

Operating Cost: The maintenance cost of grid-tied systems is very low. Solar panels routinely have 20-25 year warranties and some of the panels created in the 1950′s as part of NASA’s space program are still operational. Batteries associated with off-grid systems require regular maintenance and have a much shorter life than the panels. Backup generators also require significant maintenance and access to a cheap and reliable fuel source.

Reliability: Grid-tied systems are relatively simple and can have virtually no ‘down time’ where the customer will be without electricity. The increased complexity of battery and generator backup systems often leads to significant down time and can be frustrating to a home owner. Often poor weather that leads to little energy collected from the sun also means decreased battery and generator performance.

Flexibility: Having an alternative energy source AND a utility source means you can design your system to meet whatever needs you have now and still have the flexibility to add solar panels later. It also allows you to change your system parameters to meet your different needs in the future.

Disadvantages of a Grid-Tied System

No Backup Power: Most grid-tied inverters are programmed to shut down when the grid shuts down to precent power from the panels going into the grid and potentially harming utility workers.

Grid Tied with Battery Backup
These systems are very useful in areas with frequent power failures. Provided there is ample sunshine, these systems give the customer more autonomy, while still providing a backup system in the utility grid.

Advantages of Grid-Tied with Battery Back-up Systems:

Backup Power: with proper system design, they provide continuous power to the customer regardless of utility availability or weather conditions.

Power Management: these systems make it easier to manage your power consumption, production, and storage.

Power Pricing: Depending on the utility company’s policy, the cost of the batteries can sometimes make up for the rate ‘gap’, meaning it is worthwhile to store the excess electricity you produce as opposed to selling it back to the utility.

Disadvantages of Grid-Tied with Battery Back-up Systems:

Complex: increased system complexity means more components to install and tie together.

Cost: adding batteries and their components can nearly double the cost of a system.

Maintenance: batteries require regular fluid check, corrosion cleaning, and replacement every 5-10 years.

Efficiency: batteries are usually about 80-90% efficient meaning you may be losing 10-20% of the power you generate.

Environmental issues: The manufacturing and disposal of batteries involves chemicals and metals that most eco-minded consumers would rather avoid.

Off Grid Solar Power Systems
For reliable power in remote locations, often these systems are the only choice. They generally consist of a battery bank, a charge controller, an inverter and a solar array. Many systems require a secondary power source such as a gas generator.

Advantages of Off Grid Solar Power Systems:

Remote Use: these systems are great for cabins or cottages that don’t have a utility nearby. The cost of a system is usually far less than running power lines into the property.
Independent: Maybe best reason of all, the user is not dependent on an outside entity for the power needs.
Power Management: Since you generate, store, and use all your own power you can optimize your usage.

Disadvantages of Off Grid Solar Power Systems:

Complex: increased system complexity means more components to install and tie together.
Backup: most people will want a backup generator in case of inclement weather, which can cause additional headaches.
Cost: adding batteries and their components can nearly double the cost of a system.
Maintenance: batteries require regular fluid check, corrosion cleaning, and replacement every 5-10 years.
Efficiency: batteries are usually about 80-90% efficient meaning you may be losing 10-20% of the power you generate.
Environmental issues: The manufacturing and disposal of batteries involves chemicals and metals that most eco-minded consumers would rather avoid.

DIY Solar Part 3: System Components

In our previous posts we talked about the design process and then different kinds of systems to choose from. Now let’s talk about the system components that you need to be aware of before tackling a project like this. Many people believe that you just get some panels and wire them into the electrical system. It’s not quite that simple.

Solar Panels and Film
Of course the most obvious part of the system is the panel. But there are several types of panels to consider.

Crystalline panels: these are the blue-ish black solar panels that are encased in aluminum and tempered glass to protect them from weather. These are the most common panels and generally the easiest to find. Their advantage is that they can be mounted to nearly any surface and they have the highest efficiency.
Solar film: these cells look more like rolls of roofing materials than photovoltaic materials. This is probably the future of solar as these are much cheaper to produce. Currently the only solar film that is available has to be stuck to a metal roof. This will definitely change in the coming months and years as this technology advances.

Inverters
Solar power makes direct current, or DC power, and your home uses alternating current, or AC, power. An inverter can turn steady stream DC power into wavy AC power. There are several different kinds of inverters and they differ in the kind of wave they create.

Modified sine wave inverters: create current that resembles connected up and down stair cases, as the inverter creates steps in the current.
Pure sine wave inverters: these inverters create a nice even up and down sine wave.
Micro inverters: this is a new development where each panel has its own inverter. This helps in several ways. First it means that you can have a far smaller system to start with since you could wire one panel and one micro inverter and tie into the grid. All other grid-tie inverters require a higher voltage and need at least 1000 watts (or 4 to 8 panels) to work properly. Secondly inverting at the panel means you can use small gauge wire (instead of large diameter wire that DC requires) from the panel to the main power panel, saving money on wire cost.

Sensitive electronics, like entertainment equipment, require a pure wave to operate properly, while smaller electronics, like small kitchen appliances, work just fine with modified wave. Pure sine wave is more expensive but it recommended since we have so many advanced-technology electronics in the home these days like computers, plasma televisions, and stereo equipment.

Charge Controllers
Whenever batteries are present in a solar power system, a charge controller is needed. Most grid-tied system won’t have batteries and therefore won’t have a charge controller. Controller’s are needed because, unlike other power sources that have an off and on switch, solar panels are pretty much ‘on’ as long as the sun is shining. This can be a problem if the batteries are at full capacity as overcharging them would ruin them. So the charge controller controls how much charge goes into the batteries.

Most controllers are now Multi-Point Power Tracking, or MPPT, units. This a fancy way of saying that the controller optimizes the amperage and voltage in the system to recover the maximum wattage. This is becoming a standard feature and you should not consider a non-MPPT controller.

Control Panels, Disconnects, and Wiring
There are a lot of fuse panels, disconnect switches, and wiring in a solar power system. These are mixed and matched to suit a particular solar power system. The wiring can get expensive, so the distances between components should be minimized. DC power runs most efficiently through thick, heavy gauge wire, much like water flows better through larger pipe. The bigger the wire, obviously, the more expensive. So keeping your panels and inverters

DIY Solar Part 4: System Costs

We’ve been talking about Do It Yourself Solar and the steps involved. Now let’s get down to the brass tacks: system costs. We’ll approach it from two directions, component costs and complete system costs. We’ll use a 2 kilowatt, grid tied, roof mounted example system where applicable.

Component Costs
Let me start out by saying that I do not think its a good idea to go out and try to build a system from individual components yourself. Unless you have experience in electrical work or are already a solar professional, this can over complicate what is already a complicated process. I also get calls from people who have inherited some solar panels or bought an inverter on Ebay. You can certainly cobble a system together with used parts but keep in mind that efficiency is advancing in this industry fast enough that even panels made 4 years ago are behind the times. The best way to start is with new, brand name products.

Panels
Solar panels vary widely in cost now but are quickly becoming a commodity in terms of pricing. You can find many Chinese manufacturers that will provide panels for $2/watt. But what will you do when you have a warranty issue? Odds are your panel company will be defunct or impossible to reach.

I would suggest using a name brand for the panels. In my opinion, Sharp, Sanyo, Mitsubishi, and Kyocera are all excellent panels. Evergreen panels, which are American made, and REC which are made in Norway, are good panels but less prevalent. For these name brand solar panels you can expect to pay anywhere from $3.00 to $4.00 per watt retail. Obviously the more you buy the better your price per watt will be.

Inverters
There are three major inverter companies that do the lion share of solar installations: SMA (the Sunny Boy line is one of the most popular in the world); Fronius (like SMA a German company); and Xantrex (which makes a wide variety of electrical gear). You really can’t go wrong with these brands, but of course that means they cost a little more too. For pure sine wave inverters, which is what you’ll want for 99% of American homes, you can expect to pay about $2,500 for a 2000 watt inverter.

There are many other brands that you can get inverters for closer to $2000 (PV Powered, Outback, and Samlex come to mind) and could be perfectly acceptable for your system. One thing to keep in mind is that since you are connecting to the grid, your utility probably has a list of acceptable inverters. Be sure to check with them before buying ANYTHING.

Racking
There are so many racking makers and types (eg roof, ground, pole) it seems like every day I learn of a new manufacturer. Generally I don’t get too picky about the racking companies. The key part is making sure that you are buying the right racks for the panels and installation type you have. Uni-Rac, Iron Ridge and DPW are all reputable brands and can handle 90% of installation specifications. For a 2000 watt flush roof mount system you can expect to pay about $800-1000 for the rails, mounts and clamps. Ground mount and tilt systems get more expensive because there is just more parts involved.

Wiring, Disconnects, and Accessories
This is a hard part to estimate because it depends on your installation and the distance between the panels and the inverter. One key concept is to realize the larger the distance between the panels and inverter, the larger and more expensive that wire will be. DC power, much like water, must travel through larger wire at higher amperages to maintain efficiency. For a 2000W system I would budget about $400 for a typical wiring, disconnect, fuses, lighting arrestor, and conduit setup.

Complete System Costs
Ok, so that was the hard way to estimate a system. The fact is that companies have recognized that most people want an all-in-one-system (full disclosure: my company sells solar power kits for just this purpose). These kits can be customized for your particle application and come with the parts you need and, most importantly, instructions and drawings! Now this isn’t quite like putting together that entertainment center from Target, but with some patience, tools, and a little help from an electrician, these kits are actually very doable.

The best part of the kit is the cost. If you do the math on the system talked about before you’re looking at about $12,000-$14,000 and you have to match all your components. Kits generally run about $5-$6 per watt. So our 2000 watt example system would be closer to $10,000. And its a complete package, some customers have to add conduit and some wiring, but for the most part its a turn-key system.

Micro-inverter Systems
We touched in micro inverter system before but I wanted to talk about cost quickly. These inverters are meant to be connected directly to one panel of around 230W. Then the inverter can be connected to the grid. This changes the economics of systems significantly because you can get a 230W panel for around $700, a micro inverter for $230, and a small rack system for $100. Add in some wiring, a fuse and a disconnect and you’ve just gone solar with grid connection for around $1300. Not bad eh?

DIY Solar Part 5: Tools For Installing a System
So, now its down to the fun part. You’ve designed a system, found the kit, its here, its ready to be put up. Now what? Let me start by saying that installing a solar power system is WAY too big a subject to cover in a couple blog posts. In fact its something most people should leave to a professional. But, since we’re all about empowering people with do it yourself knowledge, we’ll cover the basics and offer suggestions for finding more details for your specific situation. In this example remember we’re talking about a 2000 Watt roof mounted grid tied system, one of the most popular.

Safety Equipment
As always safety comes first. For starters makes sure you have a really good, solid ladder. Make sure it doesn’t have broken or loose rungs and it should extend at least 3 feet PAST the top of your roof when leaned against it at a safe angle. Don’t scrimp here, you’ll be going up and down that thing a lot and most accidents occur falling off ladders, not falling off roofs. Technically you are supposed to have a rope and harness system at all times as well. These systems can attach to ridges and will save your life if used properly. Many equipment rental stores will rent large ladders and harnesses.

As always a good set of gloves, safety glasses, and work boots are indispensable. That roof surface can be more slippery than you think, especially in cold weather. For 10:12 roofs and above you may want to install a temporary walkway system with 2 x 4′s running perpendicular to the slope. This will take some extra time but can actually speed up the actual installation process. If you’ve got the budget, or the fear of hospital bills, a boom lift (sometimes called a JLG or a cherry picker) can lift you into hard to reach places safely and quickly. These too can be rented easily.

This is a good example of a roof where you could use a mechanical boom lift.
The roof is steep, there is little room to work, and plenty of room on the
ground for the machine.

Hand Tools
If you are buying a prepackaged kit, your tool requirements are pretty basic. The kits these days come connectors, often multi-contact type, that are very simple to connect. There are many projects though that bits and pieces of wire that must be cut to fit, so a standard electrician’s list of pliers (small and heavy duty), wire strippers, utility knife, and diagonal cutters will be helpful. You’ll also need a small torpedo level, multimeter voltage/amperage tester, chalk line, and a set of sockets for assembling rail hardware. If you are building your own system from scratch you’ll need heavy duty cutters for large gauge wire and crimpers for attaching connectors, check with your local equipment rental shop for these (they are very expensive!).

This tool set by Klein would come in very handy on a project like this.

Power Tools
For 90% of solar installations all you’ll need is a power drill. Depending on your roof anchoring system and your roof makeup you may want an impact drill, but usually not. For standard residential roofs with asphalt shingles and wood rafters, a simple battery pack drill will do just fine. You’ll want a nice long bit (refer to your roof anchor instructions for bit sizing) and some socket inserts to tighten rail hardware.

DIY Solar Part 6: Planning the System Install

Ok, we’ve got solar panels, we’ve got tools, now we’re ready to start putting them up! Woohoo! Well hold on there partner, the better we plan this out the smoother the install will be. So let’s take a minute and a piece of paper to figure out how we’re going to do this.

Simple Roof Diagram
Most building departments will require a sketch of where your panels are going anyway, so this is not a wasted effort. If you can do a scale drawing your install will go that much faster. Make a basic sketch of the roof area in question. Then do some reconnaissance and figure out where the rafters are and their spacing. The roof mounts, which will hold the rails, will attach to rafters. Mark the rafter locations on your drawing.

Panel Strings
Solar power systems are laid out in strings to achieve certain voltages and amperages required by the inverter. So if you have 10 panels, you may have two strings of five panels. The panels will be wired in series (positive to negative) generally in that string, to get the voltage up to a level acceptable to the inverter. Refer to your inverter specifications or your kit drawings to make sure you get this right, its critical. You’ll want one string in a row, with the next row/string adjacent to it since that one will likely be wired in parallel (positive to positive). Layout the strings and rows on your drawing and make sure its all going to work. Your local building code will probably tell you what the spacing on supports should be.

In this picture, each row is its own string. So the panels in that row are wired together in series.
Then each row is wired together in parallel. This is how most systems are wired, yours may be
different.

Equipment Check
Ok you have a drawing of the system, now check with your equipment again to make sure you’ve got everything. Nothing like getting everything on the roof only to find out you’re missing some mounts. Also, if you’re getting permits, its worth a call to the building department to see what stages they want to inspect the system at. Some just want to see the final install, other want to see the roof penetrations, which means you will have to call them before you actually put the panels up.

Roof Specifications
One final note before we get to the actual install. Certain roof materials have requirements for sealing up penetrations and temperature during roof work. If its too cold your roof materials may crack or chip. If you can take a sample of your roof material to a local supply house and have them tell you about minimum temperature requirements and sealants. This ensure that you are not damaging your roof and shortening its life.

Next up, mounting panels. Kriss Bergethon lives off the grid with his wife in Colorado and sells Solar Panel Kits

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