1- Introduction  

    Solar PV systems can reduce energy costs and carbon footprint. They're also complex, 25-year investments. Here's a primer on how solar works, and how to make it work for you.


    Turning Sunlight into Energy

    Solar photovoltaic (PV) cells convert the energy in sunlight (photons) into direct current (DC) electricity using semiconductors. A typical commercial solar PV module is comprised of 60 to 96 photovoltaic cells connected in a series, placed between glass and a composite laminate, and surrounded by an aluminum frame. PV modules are mounted to a metal framework known as racking to form an array.

    A string inverter mounted to a parking shade canopy.

    A string inverter mounted to a parking shade canopy.

    AC/DC

    The DC electricity produced by a solar PV system is converted to alternating current (AC) electricity for use by onsite loads and/or for export to the electricity grid. The conversion from DC to AC electricity is performed by an inverter. Inverters range from small “micro” inverters located on each panel to large centralized inverters converting electricity from thousands of modules.

     

    A Fine Balance

    Modules, racking and inverters are considered major components in a PV system. The rest are collectively referred to as the “balance of system” (BOS) equipment. The majority of the BOS equipment is standard electrical equipment optimized for solar applications. Monitoring equipment is specialized for PV and designed to provide real-time metrics on system performance and environmental conditions. Data is transmitted via cellular telephone network or onsite internet connections and is accessible through web-based applications.


    Types of Solar Racking

    Roof-mount PV protects the roof and keeps a building cooler, but can be costly on older or less suitable structures.

    Roof-mount PV protects the roof and keeps a building cooler, but can be costly on older or less suitable structures.

    Shade structures, while expensive, keep the sun off parking and open space and can be easier to permit.

    Shade structures, while expensive, keep the sun off parking and open space and can be easier to permit.

    Ground mount racking is low cost, and the tilt and orientation can be varied to increase output. However, the large footprint closes the area off to other uses and requires security. 

    Ground mount racking is low cost, and the tilt and orientation can be varied to increase output. However, the large footprint closes the area off to other uses and requires security. 

    Single-axis trackers follow the sun, typically from east to west. They are higher cost and require more land than fixed tilt, but increased production makes them economically viable in some cases. [Photo: Wikimedia]

    Single-axis trackers follow the sun, typically from east to west. They are higher cost and require more land than fixed tilt, but increased production makes them economically viable in some cases.

    [Photo: Wikimedia]