page_title: Rooftop photovoltaic power station
section_title: Installation
hierarchical_section_title: Rooftop photovoltaic power station / Installation
caption_attribution_description: English: The Googleplex rooftops and car parks %u2014 blanketed in solar cells as seen from the Zeppelin NT (with Marissa Mayer pointing out her office window) on our Geek Tour of Silicon Valley.
context_page_description: A rooftop photovoltaic power station, or rooftop PV system, is a photovoltaic system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters and other electrical accessories.
  Rooftop mounted systems are small compared to ground-mounted photovoltaic power stations with capacities in the megawatt range. Rooftop PV systems on residential buildings typically feature a capacity of about 5 to 20 kilowatts, while those mounted on commercial buildings often reach 100 kilowatts or more.
context_section_description: The urban environment provides a large amount of empty rooftop spaces and can inherently avoid the potential land use and environmental concerns. Estimating rooftop solar insolation is a multi-faceted process, as insolation values in rooftops are impacted by the following:
  Time of the year
  Latitude
  Weather conditions
  Roof slope
  Roof aspect
  Shading from adjacent buildings and vegetation
  There are various methods for calculating potential solar PV roof systems including the use of Lidar and orthophotos. Sophisticated models can even determine shading losses over large areas for PV deployment at the municipal level.
  Components of a rooftop solar array:
  The following section contains the most commonly utilized components of a rooftop solar array. Though designs may vary with roof type (eg. metal vs shingle), roof angle, and shading concerns, most arrays consist of some variation of the following components
  Solar Panels produce carbon free electricity when irradiated with sun)light. Often made of Silicon, solar panels are made of smaller solar cells which typically number 6 cells per panel. Multiple solar panels strung together make up a solar array. Solar panels are generally protected by tempered glass and secured with an aluminum frame. The front of a solar panel is very durable whereas the back of a panel is generally more vulnerable.
  Mounting clamps generally consist of aluminum brackets and stainless steel bolts that secure solar panels to one another on the roof and onto the rails. Clamps often vary in design in order to account for various roof and rail configurations.
  Racking or rails are made of metal and often lie in a parallel configuration on the roof for the panels to lie on. It is important that the rails are level enough for the panels to be evenly mounted.
  Mounts attach the rails and the entire array to the surface of the roof. These mounts are often L brackets that are bolted through flashing and into the rafters of the roof. Mounts vary in design due to the wide range of roof configurations and materials.
  Flashings are a durable metal plate that provide a water resistant seal between the mounts and roof surface. Oftentimes, caulk is used to seal the flashing to the roof and it resembles a metal roof shingle.
  DC/AC wiring for inverters connect wires between panels and into a micro inverter or string inverter. No cables should touch the roof surface or hang from the array to avoid weathering and the deterioration of cables.
  Micro inverters are mounted to the bottom of the panel and convert DC power from the panels into AC power that can be sent into the grid. Micro inverters allow for the optimization of each panel when shading occurs and can provide specific data from individual panels.
caption: Rooftop PV systems at Googleplex, California
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