Mount my first Solar Panels on the roof - Options?

hunter44102

All,

I want to mount a couple 55W panels close to the peak of my existing roof.

The house is fairly new and only has 1 layer of shingles.

The solar panels are 4ft x 1ft and about 12lbs each and the roof is not very steep (I don't know the angle but I can walk on in pretty easy - Its a Ranch house)

What are my options? Can I just use screws with water sealer/epoxy to hold these down, or do I need to remove shingles and use some kind of Flashing with bolts?

-hunter

hillbilly

Re: Mount my first Solar Panels on the roof - Options?

Hey there, I am certainly not exactly a solar guru like some here, but I can give a bit of info on roof mounting.  First off, from what I understand it's really preferable to elevate those panels up off the roof a bit to allow for some air flow.  Excess heat can lower your power production, and supposedly lower the life expectancy of the pv's.  Keep in mind that most rooftops can get quite hot in the middle of the day.  I know that you can look into various manufactured mounting frames, or you can make a fairly quick simple rack yourself depending on how comfortable you are with drilling holes in your roof.  I made a pretty simple set up with a couple of L-brackets bolted to crossblocks in between my rafters (this was easy since I built the roof first, and was able to install the blocking before sheathing the roof).  I mounted 4 more L brackets to some some extra decking boards that I had lying around (two for each board), this essentially makes for two cross bars that I then bolted the pv's to.  The two sets of L- brackets simply bolt together.  I also put in a couple of vertical riser bars for the upper cross bar; these have several holes drilled in them allowing me to raise and lower them seasonally to change the tilt angle.  My panels are about 4-6" off the roof at their lower edge, and about 2-3ft at their upper edge (depending on the seasonal tilt), this allows for lots of air flow.
  I am sure that you could do much better than that if you are good with tools, or if not it might not be a bad idea to look into some of the pre-made racks out there. 
good luck

crewzer

Re: Mount my first Solar Panels on the roof - Options?

Hillbilly’s right: Mounting PV modules directly to a roof can cause several problems:

(1) The modules need an air flow both over and behind them for cooling.
(2) Mounted directly to the roof, the modules will operate at a higher cell temperature, and that will reduce their output voltage and power.
(3) The heat build up behind the modules (~+70 F or more) could also damage your roof.
(4) Mounted directly to a “not very steep” roof will result in poor solar alignment most months out the year, especially in the winter. This poor alignment will result in reduced output current and power.
(5) Mounted directly to a “not very steep” roof will reduce self-cleaning of the modules during rain and snow events. Debris build-up on the modules will reduce their current and power output, and snow build-up will completely block power production.

Your modules should be mounted facing South, tilted up at an angle equivalent to something between local latitude value and latitude +15 degrees, they should be have plenty of air circulation on both sides, and they should be accessible for occasional cleaning and snow removal. Seasonal adjustments (lat - 15 degrees in summer, lat + 15 degrees in winter) will increase year 'round energy production capacity.

I build my module mounts from PT 2 X 4’s. Angle aluminum should also work, and here’s a link to info on commercial mounts for a variety of applications: http://store.solar-electric.com/panel-mounts.html

HTH,
Jim / crewzer

SolarJohn

Re: Mount my first Solar Panels on the roof - Options?

Here is how I did it.

http://solarjohn.blogspot.com/2007/02/mounting-solar-panels-on-your-roof.html

John

System2

Re: Mount my first Solar Panels on the roof - Options?

here's the system i used...
http://translate.google.com/translate?hl=en&sl=de&u=http://web.k2-systems.de/cms/front_content.php%3Fidcatart%3D30%26lang%3D1%26client%3D1&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3Dhttp://web.k2-systems.de/cms/front_content.php%26hl%3Den%26rls%3Dcom.microsoft:en-US

it was pretty cheap to...

rplarry

Re: Mount my first Solar Panels on the roof - Options?

Hunter
Roof mounting is by far the easiest way to exppose your panels to the sun but it is also one of the least efficient ways to harvest the suns power. I have always felt that a top of pole mount is the best and if you add a tracker to the T-O-P mount you have one of the most efficient ways to collect the suns power. I recently completed a project to add a tracker to my array and the rusults are very impressive. I gained a full 40% in production over my fixed array. The tracker is made useing an old satellite dish mount and the sensor comes from a guy in Minnesota at:[http://www.redrok.com/electron.htm#led3x]
If you have the room in your yard the top of pole mounts are a very good choice to increase your solar out put.
Good luck with your install,
Larry

hunter44102

Re: Mount my first Solar Panels on the roof - Options?

Thanks for the great responses with great ideas and links!

I do have room in my yard to do the Pole mount, but there are some trees on the south. Putting it on the peak of the house may get more sun.

But there may be an advantage to keeping the Panels cool by putting them on pole mounts.

-hunter

niel

Re: Mount my first Solar Panels on the roof - Options?

hunter,
do understand that there isn't any difference in efficiency between a fixed pv on a roof or a fixed pv on a pole. the efficiency difference that rp is talking about is in tracking the sun, which is usually done on a pole and not a roof, as oposed to a fixed pv. you may have a point of not being exposed to the heat buildup of a roof, but if the roof is covered in pvs then the roof is not absorbing the sun's heat to affect the pvs because the pvs are shading the roof. do understand that no matter where you mount them that the sun will heat them up so no matter where you decide or how to mount them, they should have good airflow around them to help cool them.

rplarry

Re: Mount my first Solar Panels on the roof - Options?

Hunter
Niel is correct and I appreciate his clarification of my post. Your 2 55 watt panels, if roof mounted, would produce their peak power for approximately 2 hours a day and less than peak the rest of the time. If your panels were mounted T-o-P and tracked the sun then they could produce peak power for 8 hours a day. These hour numbers are guesstimates and may be different for you. But the point is that you will get peak performance from your array for more hours in a day and that equals more power production from your investment. Since in your case you will only have a total of 110 watts then a 40% increase to 150 watts approx. might not be worth the expense of a tracking mechanism. In my case I have 1000 watts of pv and the increase of my production was dramatic. I have only had it in operation for a month now so only time will tell if my efforts were worth it. If you get a chance check out the redrok.com website. Its very informative.
Larry