2) Design Your Project
Using the data you collected in the evaluation phase, you can produce a system design detailed enough to determine your costs and benefits more precisely, and provide documentation for permitting and installation.
At his point you are going to need some more detailed information and lock-in some of your choices to generate a detailed design suitable for a material list, accurate costing, and installation. Many of these tasks can be done in parallel.
2.0 Project Set-Up
If you have not already done so, it is appropriate to have your project set-up in OpenSolar and a project folder set-up on the HAREI projects folder. You will first need to set-up a login on www.OpenSolar.com, and then request your project be set-up.
2.1 Roof evaluation, condition and structural (applies to rooftop only)
Roof Condition
Solar arrays have a typical life of 20 years or more (we have members with functioning systems 30+ years old), if your existing roof does not have this much life left, you may want to consider a new roof (at least where you will have solar arrays) before you install rooftop solar. Newer asphalt shingle roofs can have a life of 20 to 50 years.
Roof Structure
Solar does not add much load to your roof, typically under 3 pounds per square foot (snow load in most NH towns is around 70 psf). Most towns will require a roof structure evaluation by a professional engineer before issuing a building permit. You should contact your town's building department to see what they require. If an evaluation by a structural engineer is required, the contact information for the firm most HAREI members have used is in the document here under "Structural Engineering". Even if your town does not require it, it is a good idea to make sure your roof structure is in good shape. If you did not evaluate your roof structure yet, now is the time to do it.
When using Sandford Survey and Engineering (professional engineering firm most HAREI members use), the process can be expedited by providing information and evaluation in advance working with knowledgeable HAREI members. Making a copy of this spreadsheet, in your project folder, completing it to the best of your ability and providing supplemental information similar to this is a good start.
2.2 Determine panel and inverter selection
Panel availability continues to be a challenge. It is best to confirm panel availability before you do a detailed design to avoid having to rework your design. Most panels are relatively close in width, but not exactly the same, but the height can vary significantly. Go here for the process of choosing your panel selection and confirming availability.
You will need to make a choice between micro inverters and string inverters. Once this choice is made, decisions need to be made on the specific inverters and associated equipment. Final panel selection, batteries/no batteries and backup generators will affect along with decisions on optimizing price/performance vs. maximum energy production.
Click here for a description of each inverter type, including the advantages and disadvantages of each.
2.3 Mounting/Racking System Design
The detail design processes diverge at this point for rooftop and ground mount solar installations. The design process mostly comes back together at the electrical design step. Follow the path that you have chosen for your project.
2.3.1 Rooftop Mounting
Roof Access/Pathways are often required so firefighters can get to the ridge of your roof. Emergency Egress is also a factor. There is a national code for these and each City/town requirements vary. You should contact your building inspector and/or fire department to get your town’s requirements and agreement on your plan. They have wide latitude and ultimately have jurisdiction. Following are some links related to this requirement.
Solar Fire Code, NFPA - Starts on section 11.12.2.2
NH Department of Safety Info Bulletin - Includes NH exceptions to NFPA code
Accurate roof dimensions - Before you can do a detailed design, it is a good idea to measure your roof. Satellite images are great but can be off by feet! In many cases accurate roof measurement can be done mostly from the ground or at least only from a ladder (versus running around the roof before you have safety anchors in place). There are also some newer services that will generate 3D models of your house with relatively accurate roof dimensions. Go here for how to get accurate roof measurements.
Racking design with IronRidge – Most HAREI members have used IronRidge racking systems. IronRidge has solutions for most roof types. There are other very good systems for rooftop mounting but for this example we will use IronRidge but the other systems are likely similar. Designing your racking system on the IronRidge web site will get you a detailed material list for the racking components and a layout. The output from IronRidge is generally suitable for your building permit application. Go here for how to design your rooftop racking system on the IronRidge website.
Detailed Drawings are useful when you are doing DIY rack installation and more useful if you are hiring a contractor for the rack installation. These can be done on a CAD system or by hand. The learning curve for CAD can be steep, and easier and better systems are not free. Alternatives are to contract this out or use paper and pencil. Guidelines and suggestions on creating detailed drawings are here.
2.3.2 Ground Mounting
Discussion of ground mount systems. More to come.
2.4 Electrical Array Wiring
We come back together from the two paths above - Rooftop vs. Ground Mount.
Special cabling is used to connect groups of panels into "strings". A layout of your array wiring is an important step in the process to ensure you order what you need and minimize power losses. Array wiring will affect the location of microinverters or optimizers (one under each panel), rooftop junction boxes and passthroughs (typically one in the same, but not always), and access for electrical service. Go here for discussion of rooftop array wiring or here for ground mount array wiring.
2.5 Electrical Design
HAREI has developed a tool that extracts your design information from OpenSolar and helps you:
Develop your electrical design,
Create a materials list,
Create documents needed for your utilities interconnect application, provides instruction on how to complete the interconnect application (for Eversource only, but inputs needed for other utilities)
Create documents needed for your city/town's electrical permit.
You will need the assistance of a HAREI Electrical Subject Matter Expert (SME) the first time through this tool. Once a first pass has been made, a copy of the tool will be saved in your project folder for tweaking by you. Once you have completed your preliminary design in OpenSolar, contact the Electrical SME group for assistance.
When your design is ready, it's time to apply for the permits and rebates you will need before you can begin installation.