DIY Solar Part 1: The Design Process
For homeowners around the world, the idea of reducing their power billsand helping the planet is pretty enticing. The problem now as it alwayshas been is money. Solar can be expensive, and even with governmentrebates the cost can scare some people away. If you are a do-it-yourselferyou’ve probably wondered if you can tackle a solar project. Let’s walkthrough a typical design and installation process and see if its rightfor you and your home.
Location Selection BasicsWellyou’re probably smart enough to figure out that you’ll need A) a sunnyregion and B) a sunny place to install the system. The more sun youget, the quicker your systems will pay for itself, its that simple.There are some nice tools to determine where exactly you should put thesystem. The solar pathfinderis one of easiest and most affordable ways to find the best locationfor panels. This ingenious device works by showing you a reflection ofthe sky and the sun’s path for all four seasons in your area. Usingthis you can see exactly what will shade your panels throughout thecourse of the year.
You also want solar panelsinstalled fairly close to your home and power meter. Since photovoltaicpower is DC, the wire that carries it grows larger and more expensivethe further away it is from the inverter, meter, and power center ofthe house. You’ll want a place close to the house but out of way ofchildren and their errant soccer balls. Also if you are planning oninstalling the system on your roof, its worth it to do a roofinspection. No sense in installing a system if it will have to beremoved in a couple years to replace the shingles.
Determining Angle and Azimuth
Generallyspeaking the closer you can get your panels to facing due south (or 180degrees azimuth) the better. If you live in an urban area and are notsure which way south is exactly, use Google Mapsto look up your address and click on the satellite image. You might besurprised to see that roof you thought was south facing is actuallysoutheast facing!
The angle from horizontal is very importanttoo. The angle should be equal to your latitude since this will meanthe panels will be perpendicular to the sun for greatest amount oftime. 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 45degrees, your panels should be set at an angle of 45 degrees fromhorizontal. IF your roof angle is within 10 degrees of you latitude youcan mount the panels easily, if not you may have to consider a racksystem that will tilt the panels.
Therule of 1/10 is easy to remember for solar power. You’ll need 1/10 of asquare foot for every watt you install. So if you want to install 2,000watts, you will need about 200 square feet of space for panels,racking, wiring, and a little space to work around them. This will varyslightly by the type of installation and panels you get but this willserve 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 newmeter or even an additional meter for the system.
Contacting the Utility and Building Department
Itsalways a good idea to talk to your power company about installing asystem. You will probably need an interconnection agreement, aninspection, and a rate schedule if you are planning to sell back power.They’ll also want some information about the panels and inverter youare installing. Also, ask about additional rebates and an up to datecost per kilowatt-hour that you are paying.
You should alsoplace a call to the local building department and ask about permits.This may seem like a pain, but really it protects you from hassles inthe end. Eventually they’ll probably find out about your systems anywayand you may have to pay a fine for not getting a permit. The vastmajority of inspectors will allow you to install a system on your ownhome, they may just require you to have a master electrician sign offon the installation.
Estimate Your Production
you’llwant to decide just what the system is going to produce over the courseof a year. The National Renewable Energy Lab has a cool tool that willallow you to do this. With the information you’ve determined in thesteps above, click on this solar map.Then find your area, and double click on it. You should see a datawindow open up with a link at the bottom that says ‘Send to PVWatts’. Click on that link, then enter the information we determined inthe first steps for angle, azimuth, and cost of power. Also enter thesize of the system you want in kilowatts. Click on the calculate buttonand you’ll see the production per month for a year. This can help youdetermine payback.
Finally: Determine a Budget
Possibly the most important part is deciding how much you can spend on a system. Most complete solar power kitscost between $4 and $6 per watt, depending on the size and rackingsystem. Be sure to take into account all state, local, and utilityincentive programs, which can be found here.You may even find a supplier that will take the rebates off the priceof the system, then the manufacturer goes after the rebate. Sharp has aprogram like this.
Next we’ll determine what skills and tools are needed, and start planning the installation.
image:A Solar Pathfinder makes site selection a snap.
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