Hi Amethyst,
Hopefully this late reply is still useful. There are so many things that could be incorporated into buildings to make them more solar-ready than what we often find when trying to retrofit a system. As Robert and William have already stated, the orientation of the roof surfaces, the array tilt, etc is relevant, and whether south-facing, or East and West, there really is no ideal universal answer. Each region of the US has insolation and weather characteristics that would influence that decision. As William alluded, the Net Metering policies of each local utility would also be relevant. Modeling different orientations and tilts, including shading analysis, and looking at the daily load profile against the net metering policy might make East-West look more beneficial than due South for some projects.
But there are other things:
Minimizing roof penetrations, and locating/clustering penetrations and other obstacles in roof areas that are less optimal for PV arrays is extremely important. Eliminating purely aesthetic building elements that carve up what could be large expanses of usable roof area into smaller areas with triangular or trapezoidal shapes can severely reduce the viability of solar for a building. We need large, unbroken, unshaded areas for arrays. There is nothing more fustrating than arriving at a 4,000 sq ft home with a huge electric bill and a customer with a generous budget, but has a roof carved up into 8-10 little surfaces facing all directions and with hips and valleys everywhere. Solar panels are rectangular, not triangular.
Selecting solar-friendly roofing materials and construction methods is important. Standing seam metal roofs, with profiles that enable clamping to the seam, and additional attachment points during installation that increase the pullout strength of the steel panels. Lighter color roofing that would result in lower array temperatures since PV output decreases with higher temperatures. Flat roofs with EPDM, PVC, or TPO membrane are great for ballast-mount racking systems holding the array, as long as the structure was designed for a little extra weight (Not a lot of weight, really, generally 3-5 psf worst case). If there are roofs of varying height, put the lower roofs on the south side, and make the vertical wall facing that roof white or of light color, so that it reflects light back under the flat roof mounted array with bifacial panels.
And then the electrical distribution system. Designing into the service and the main service disconnect and/or panelboard extra capacity, breaker space, or physical space so they are ready to accept a solar generation system without having to add expensive 3-phase hardware. Making the main buss larger to allow load side connection, or adding a CT cabinet for supply side connection. Thinking about conduit pathways between the array and where the inverters might be located, or between the inverters and the interconnection point.
And storage is going to become mainstream with most solar installs. Thinking about where large amounts of energy storage would go, and what distance limitations there may be between components. And which circuits might the customer want to be backed up in the event of a utility outage. Lighting, communications, computers, and any critical loads should be put on separate subpanels. The storage will not only be used for backup in outages, it will increasingly be used to reduce the import/export swings from/to the grid, and to reduce demand charges as utilities adapt their rate plans.
Lastly, in certain areas of the country we should start to think about greater variability from normal weather patterns as climate change worsens. Maybe we should add a little buffer to max winds speeds and highest expected temperatures when designing. Maybe we should plan for more frequent and extended power outages.
There is a lot that could go on a wish list for making buildings solar-ready. These are a few that I think about, and I'm sure others have run into problems that spark more suggestions.
-Ken Nadsady
------------------------------
Ken Nadsady
AviSun Renewable Energy
Hudson OH
------------------------------
Original Message:
Sent: 05-10-2024 07:18 AM
From: Amethyst O'Connell
Subject: Principles of Existing Electrical Design in Buildings to Enable New Solar
Hello, my name is Amethyst O'Connell, I recently got my first job out of college at an MEP firm that is known for it's sustainable design. I'm looking for ways to improve my own sustainable design skills in Electrical Design. I was wondering if there are general principles of electrical design that developers, electricians, installers, and others look for, when developing new rooftop solar on a commercial site that can reduce costs, make your life easier, or make that site selected more often, that you would like to see become more common as more people want rooftop solar. I would especially be interested if you work on community solar, what principles do you wish someone had thought about when designing the building that make you go, yes, this one has the perfect electrical design to have solar installed.
------------------------------
Amethyst O'Connell
Electrical Designer
Michaud Cooley Erickson
Minneapolis MN
------------------------------