It took Adam and I and the electricians 4 days to install our 18 panel 4.5 kW grid-tied solar photovoltaic system. At two full stories to the eave, a 2 foot overhang, a 12:12 pitch, and a slippery-when-wet roof, a lift was certainly in order. After deciding layout, installation began with snapping a chalk line for the first rail. Working with Adam on our house again was fun in a nostalgic sort of sense. Of course, this time we were both getting paid as Sandri employees–it isn’t every day that you get to hire yourself!
The rails are attached to the roof using S5!’s new Protea clip. It is specifically designed to adapt to any metal roof with trapezoidal ribs. The fantastic thing is that they don’t need to be sunk into the trusses/rafters. They simply attach to the metal rib using four gasketed sheet metal screws. These clips were a huge boon to us because our house has cathedral ceilings across the entire roof; no access to the trusses. The manufacturer claims the clips can take 1000# uplift. When we walked and moved around on the rails, Adam and I both felt that they were more stable than rails mounted with standard Eco-feet with L brackets.
Solar panels produce DC electricity so you need an inverter/s to convert to AC. Although somewhat more expensive than a single inverter, we chose to use micro-inverters. This means that each panel has a dedicated inverter beneath it. This allows the system to overcome some of the problems associated with shading. In a typical single inverter system, if any panel is shaded, all of the other panels can only produce as much as the shaded one. Since we have a large silver maple tree right next to our house micro-inverters were essentially a necessity. At present time, there are only a few microinverters on the market: PowerOne, Renesola, and Enphase. We went with Enphase in large part since they have been on the market the longest. When you choose a micro-inverter you are also signing up for the same company’s monitoring system. You can log into your system via a web portal and see statistics for each panel as well as the entire system. If any panels are not functioning you will know.
Before we put on the panels I took a final set of solar access photographs using our Solmetric Suneye camera that uses a fish eye lens to photograph the sky. After orienting the camera towards south and leveling it you take a photograph that is instantly analyzed by the on-board software. Our annual solar access average is at least 85%. I say at least because we removed one final branch using the lift after the shots were taken.
I wanted to use US made solar panels so we went with American Choice panels sold by Renewable Sales. The panels are in fact re-branded 1Soltech panels made in Texas. Each panel is rated to create 250 watts/hour. The rating system baseline is actually somewhat worse than the amount of sun we get in Greenfield Massachusetts so, shading aside, one can expect to see more than 250 watts per panel under ideal conditions.
As solar installers, Adam and I often get asked if we install systems with battery back ups. Unfortunately, battery technology/costs are not at a place where it is economical. However, there are a couple of promising workarounds coming on the market that, when the grid is down, allow electricity from the panels to be used in real time without batteries. One of them is an inverter by SMA that provides up to 1500 watts on a dedicated switched outlet.