Components for your PV (Solar Electric) System

Balance of System (BOS)

In PV system terminology, everything besides the PV modules themselves is called “balance of system” or BOS. We’ll go over the main BOS components below, one at a time, in the direction of electricity flow through a typical system.

Mounting Systems

Mounting systems for PV modules include hardware to permanently affix the array to either a roof, a pole, or the ground. These systems are typically made of aluminum and are selected based on the specific model and number of modules in the array as well as the desired physical configuration. Solar modules work best at cooler temperatures, and proper mounting allows for cooling airflow around the modules. For all locations, wind loading is an installation factor, and it is extremely important to design and pour the cement foundation properly for any pole mount. Solar trackers are a pole mount option to increase energy production by moving the array to face it into the sunlight as the sun moves across the sky. An array on a tracker will produce more energy than a fixed array. Trackers are often used in water pumping applications. The cost of a tracker can be significant, and due to the possibility of breakdown, they are best recommended to the mechanically inclined. The cost of a mounting system varies based on the number of modules and type of mount. The average cost is between $250 and $1,000 for a fixed array and $2,000 and up for a solar tracker. Another cost-estimating factor for mounting racks is $0.50 to $1.00 per rated array Watt.

Combiner Box

A combiner box is an often-overlooked, yet essential part of most PV systems. The combiner box is an electrical enclosure which allows multiple series strings of solar panels to be combined in parallel. For example, if you want to wire together two 12 Volt panels for your 12 Volt system, you will wire each panel’s output directly to terminals inside the combiner box. From the combiner box you can then run just one positive and one negative wire (in appropriate conduit) to the next system component, the charge controller charge controller. The combiner box will also house series string fuses or circuit breakers. These boxes are usually outdoor-rated, and meant for placement right next to the array. Combiner boxes usually cost between $80 and $140 USD.