Things to Consider Before Installing Rooftop Solar

First the basic questions

• Is this a new home construction?

If so, then you have the opportunity to integrate the roofttop solar system into your design rather than retrofit it.   You can now optimize orientation, and layout including location of your inverter and electrical disconnects etc for aesthetic appeal.  There is an excellent booklet provided by the United States Environmental Protection Agency (EPA), that provides a comprehensive discussion on this subject including specifications and checklist.  You can download it here;

http://www1.eere.energy.gov/buildings/challenge/pdfs/rerh_pv_guide.pdf

•  Ground  based or Rooftop?

If you have the land, then a ground based system may be the best for you.  The most efficient approach would be tracker based.  This way your array can follow the sun for maximum energy harvesting.   In the countryside this would be a viable option but in the towns and cities where land is at a premium, rooftop solar is the way to go.  I’ve outlined below some basic questions that can get you started and if you read on through the blog, I will attempt to answer or provide links and tools that will help you answer them.

• Is your rooftop new or has it recently been replaced? 

Remember that the life of a rooftop solar system is at least 25 years.  If your roof will need replacement in 10 years, you might consider your options such as replacing it now or waiting to install the rooftop solar system until your roof gets replaced. 

• Do you have a large enough surface on your rooftop to mount your rooftop solar system on?  

      Possibly it has to be located on more than one surface and facing more than one direction.  This is not a ideal but may affect your decisions on the panels you purchase as well as the inverter/microinverter approach.

•       Shading

      Are there any trees or obstructions that will shade all or part of the panels for some of the time or all of the time.  You also have to consider the trees growing and shading the solar panels in the future. 

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•      Location of the electronics

      Do you have a location for the equipment.  Consider the aesthetics as well as practical items such as access, environmental impacts such as direct sun on the inverter which would diminish your energy returns.

•      Design of the layout on your rooftop. 

     What will the solar panels look like at street level, from across the street, from the east side and westside?  Would you like natural (aluminum) coloured frames or black frames for your solar panels?

•      If you are going solar through Ontario microFIT, are you willing to commit staying in your house for at least 20 years?

     Yes, the contract is transferable, but then again why would you want to install a rooftop solar system if you aren’t going to reap the benefits.  Since rooftop solar is new to the marketplace no one really knows how much of a premium you can charge for your system and with the payback being at least 7-9 years, you want to get your investment back and then some.

      If you want to go solar to go off the grid, then your decision tree is much different and I don’t know enough of this area to provide advise and suggestion-Good luck!

•       What size system would you like? 

      This is an important question for a number of reasons.  Can your roof support a system of the size that you would like?  From a financial point of view, if participating in a microFIT program the larger the system the greater the returns and payback but the initial capital required would be greater. than a smaller system.

•       Financing

      Can you afford the initial outlay of capital or if can you borrow money at a reasonable rate.

Some Considerations

You  may think that you don’t quite make the cut.  Not facing south, not enough rooftop surface, the angle is of inclination is not optimum, shading issues.  Don’t get discouraged right away.  It still may be worthwhile.  Especially if you are installing rooftop solar under a microFIT contract.   Panels can be purchased with greater energy harvesting density per square meter for example.  With microinverters or DC-DC optimizers you may still harvest a reasonable amount of energy to make the project financially viable. 

Azimuth

If you aren’t facing true south, you certainly will not realize optimum power or if your angle of inclination is off the requisite perfect angle you will not harvest 100% of the energy.  But that may not be a problem.  You have to complete the analysis from a financial perspective and you may find that having solar panels on your west facing and some on your south facing may work out well.  Sure your returns won’t be as high as  if  everything was perfect  aligned but on the other hand if the returns meet your minimum expectations, then proceed.  It is quite surprising how much sunlight you can harvest from the East and West facing

Inclination

The same comments that I made above stand as well for inclination.  Depending upon your location on the Earth you may not be able to place the solar panels in the perfect angle but you will still be capturing sunlight.

Shading

Shading could be a bigger problem but there are hardware solutions to some of the problems.  Depending upon the shading issue you could use micro inverters instead of one or two strings going to an inverter.  Another solution would be Tigo or Solaredge DC-DC MMPT devices which attach directly to the solar panel like the microinverter.  If you must use an inverter, you might look at one like the Powerone Aurora which allows 2 strings to be attached and each string would have its own MMPT.  

Types of Roofs

The type of roof, whether it is asphalt shingles or Spanish tiles should not be a problem although each type of roof demands its own unique approach.  Regardless of the make-up of your roof, the mounts must be installed into the rafters using steel lag bolts to get maximum strength and durability. Making certain to secure the mounts to the rafters is the surest way to avoid major damage. All other installation methods fail to provide the weight bearing structural integrity needed to protect your roof and the delicate panels. Once in place, the mounts should then be covered with metal flashing.

Here is a page discussing the various roofs:

http://solarpowerrocks.com/solar-installation-stuff/how-are-solar-panels-attached-to-my-roof/

Don’t despair and ask your professional solar installer for their advice.