The house at left is roofed with solar panels. No doubt there’s a real roof under there, but someone has cleverly configured photovoltaic panels to cover the roof so neatly that the eye sees only tempered glass and aluminum frames. The roofing material under the panels will not deteriorate, seeing no sunlight, clomping feet or ice and snow, so its life should be at least as long as that of the panels. The panels are attached flat to the roof, with a slight standoff for cooling air, so wind forces should not be a problem in heavy weather.
Note, if your eyes are that good, the shadows of the small trees in the foreground. They indicate that the azimuth, or compass orientation, of the roof is exactly or nearly south-facing, and that no nearby features like trees or other building threaten to shade the panels any time during the solar day (popularly reckoned to be between 9 AM and 3 PM).
No nearby power lines appear in the photo, so it’s hard to be sure whether the panels feed directly out into the local utility wiring (or grid), or to a battery bank designed to power the house after sundown, or a combination of the two functions (bi-modal, it’s called).
A tiled roof in the background, along with mountains, suggests either a western US or possibly European location, places where solar panels are considered more progressive than kooky, and where local governments subsidize and encourage responsible photovoltaic installations. The local power supplier, or utility, may be purchasing the panels’ output at its own retail rate (net metering is the industry term), or it may be paying a “feed-in tariff” of up to twice the retail value of the power, a practice widely used in Europe and Canada to encourage the installation of solar electric arrays.
The residents of this house (subtle signs indicate this may be a barn) may spend some time each day accommodating their routines to the flow of solar power. They might operate their heaviest electrical loads, i.e. water pumps, refrigerators, dishwashers, clothes dryers, water heaters etc. while solar output highest, using their own power rather than purchases kilowatt-hours. They might adjust their lifestyles subtly to decrease power usage in the evening, using only lights and small loads while only battery current or expensive utility power are available.
Or, if the system has no “backup,” they may go about their business with no thought of loads, since the grid power simply flows into the house at night the same way the solar power flowed out through the meter all day. The local availability of sunlight, or “insolation,” may be as little as 2 kilowatt hours per day per square meter, or as high as six kilowatt hours per day per square meter, depending upon latitiude, climate, compass orientation and shading. The panels themselves may be as little as 12% efficient in transforming uv radiation into electric power, or they may be as much as 20% efficient, according to the quality and cost of the equipment when purchased. The panels, by their appearance, are not homemade, or if they are, they are meticulously framed and sealed. The wiring that connects them to each other is high-grade silicone with a sunlight-resistant coating, and the “inverter,” thedevice that transforms the panels’ DC output into AC power usable by house loads, also synchronizes that AC output to the grid power for resale.
This primer, with links, is meant to bring your thinking into the picture with solar PV and the role it may/will play in your life in the future. Next time you’re driving past a house with panels on its roof, picture yourself living in it. Solar power on the roof doesn’t mean less fun for people living under those panels; to the contrary, there’s something natural and comforting about being linked to this life-giving power source in a positive and profitable way. But you humans, if you go out there, use sunscreen.