July ushered in the start of the real action for our Tesla solar roof, as the installation kicked into high gear. The first materials arrived at the house and the team prepared to install the solar roof on our new home. Before we get into the installation, let’s talk about the components that make up of one of Tesla’s solar roofs.
Many of the components and processes used in installing a Tesla solar roof are from the traditional roofing industry, which makes sense. The solar roof still fundamentally has to perform all of the same functions of a normal dumb roof before its ability to generate power matters. It also includes many of the same components as a traditional bolt-on solar system, with rooftop wiring, inverters, safety devices, and the like.
A Tesla solar roof installation starts with the installation of a waterproof underlayment. Tesla uses Firestone’s CLAD-GARD SA-FR, a standard roofing underlayment for metal roofs. This product provides a waterproof foundation for any roof while also providing a skid-resistant surface for the installers to walk on while installing the more complex parts of the roof. This is the white material in the photo above.
After the underlayment goes down, Tesla’s crew frames up the roof with metal. A metal trim wraps around the entire roof edge as well as along every peak and valley in the roof structure. In the valleys of the roof, the metalwork provides the drainage for any precipitation and debris. Up at the peaks of the roof, it provides protection, funneling any precipitation onto the tiles or surfaces below, which ultimately escort it off the roof.
Tesla makes all of its own metal products for the solar roof, so all of these components are specific to the Tesla solar roof. Word on the street is that these are all currently made in the Bay Area, but that likely won’t be the case as Tesla ramps up production after locking in the design of version 3 of its solar roof tiles.
The star of the show in the solar roof install is obviously Tesla’s solar roof tiles. These come in two flavors: 1) tiles with solar cells sandwiched between two pieces of tempered glass that produce power, and 2) glass tiles. Roof tiles with solar cells in them are called PV Tiles and are the fundamental building block of any Tesla solar roof. They arrive on site in pre-wired, pre-mounted bundles of 3 tiles in a row, called PV Modules.
Each PV Tile has a production capacity of just over 8 watts each, translating to 25 watts for a full 3-tile PV Module. Assembling the tiles together into PV Modules at the factory has multiple benefits, with the first and foremost being a reduction in the amount of effort and time that’s required to install a solar roof. This helps Tesla deliver a faster turnaround time, means less time for a customer’s home sitting there without a roof, and keeps labor costs down.
Using PV Modules also reduces the number of on-site wiring connections that need to be made, allowing Tesla to control the quality of more potential points of failure in the roof system at the factory. PV Modules come with the joints between the three tiles pre-sealed, resulting in what is surely a higher quality, more consistent seal that what can be guaranteed with a field installation. Each PV Tile comes with its own set of built-in c-clip mounts and stand-offs that hold the top of the tile off of the roof, transferring any weight from above to the roof surface below while also serving to set the correct angle to allow water to run down the roof.
Tesla calls the non-producing tiles Roofing Tiles, which are simply made from a single sheet of tempered glass. These come from the factory as single tiles as well as bundled into Roofing Modules comprised of 3 glass tiles. Tesla uses these on sections of the roof that are not wide enough for a block of solar tiles and for use along the seams of the roof. To ensure a clean fit at the seams, Tesla’s team simply cuts the tiles to match the angle of the seam they will butt up against.
Tesla has packed an impressive amount of functionality into each single PV Module, and the mounting bricks are the other half of the system that makes it easy for Tesla’s installer to secure the PV and Roofing Modules to the roof. Tesla’s mounting bricks come in standard and drained configurations.
Standard mounting blocks allow the tile below it to mount to it, but also allow the panel above it to clip to it, thanks to a healthy dose of industrial grade plastic hook and loop. The trailing edge of the panel above the mounting brick has another strip of this fabric, resulting in a very secure bond. Check it out in the video below:
Drained mounting bricks include a channel that helps water drain in the proper direction between each of the PV Modules or where they butt up against a Roofing Tile or Roofing Module. They still allow adjoining modules to mount to them with their c-clips, but with the added benefit of funneling water down the roof.
The Electrical System
Each PV Module is connected to the solar roof wiring string via standard solar MC connectors that come pre-installed from the factory. These strings then connect down through the roof via a series of electrical pucks mounted and sealed to the roof. Tesla is required to install a Rapid Shutdown Device (RSD) within 5 feet of every solar array, so they are typically installed up in the rafters near the roof.
On the inside of the house, the pucks sprout bare wires that connect to one of a handful of these Delta Rapid Shutdown Devices, shown as a small grey box to the right of the rooftop wiring in the image above. Outputs from the RSDs are fed down to a pair of Delta inverters that convert the DC power from the roof down into the AC power that all the electrical goodies in the home want.
From there, the wiring configuration varies depending on whether Powerwalls are being installed or not. We are installing two Powerwalls, so we’ll talk through the essential loads wiring configuration. For our house, we do not have anything running on gas, so all our appliances, cooking, and heating are electric. Add to that two electric car chargers and a spare for guests and our loads were just too large to cram into a single 200 amp electrical sub-panel.
After all the load calculations were done, we opted to pull a few of the larger, less critical loads off of the Powerwall battery backup and just backup the “essential” loads in our house. The image below shows a single, undersized inverter and diminutive supporting boxes. Every single one of these boxes/devices in our system is twice as large as shown here, with the exception of the Tesla Powerwall (though, technically, we do have two of those).
The two Powerwalls provide backup power to everything on our 200 amp sub-panel, while the remaining loads in our home — our electric oven and two of our car chargers — will be relegated to the 400 amp main panel.
The Tesla Backup Gateway provides communication to the Tesla Mothership and can automagically disconnect the home from the grid in the event of a power outage. Doing so engages the Powerwalls to provide power to all of the essential loads in the sub-panel, while being replenished by the rooftop solar system when the sun is out.
That’s an overview of the components in a Tesla solar roof system. We’ll dive into the system more in future articles, so stay tuned for a first look at this hot new clean tech.
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