WE KNOW WHAT A SOLAR PANEL IS – WHAT OTHER ITEMS ARE NEEDED TO GENERATE MY OWN ELECTRICITY? Internal electrical connections and module mounting techniques are critical determinants of panel cost, reliability, and endurance in an exposed environment. The module usually uses an aluminum or plastic frame to facilitate mounting. Frameless designs have been developed and may be appropriate for larger arrays of individual modules, but the majority of the market is still requesting individual frames.
The electrical connection of the module is through a backside-mounted, sealed junction box. This junction box contains a terminal strip to allow the module to be wired and connected with other modules or the load. The junction box may contain a module bypass diode which is a device that allows a series-connected PV system to operate if one of the modules is inoperative due to failure or damage. Several manufacturers are attempting to eliminate the labor and complexities of the junction box by using quick connect/disconnect electrical connectors with varied success.
One of the most important components of a PV system is the inverter – the electronic component that converts the PV array’s DC power into conventional alternating current (AC). The inverter is sometimes referred to as a power conditioning unit or PCU or by other terms.
The term balance-of-system (or BOS) is the name given to the equipment of a PV system other than the actual PV modules. Many items can be included in the listing of BOS categories. Typically, the term BOS has been identified with the DC-to-AC inverter; the foundation and structure that mount the PV modules (sometimes tracking the sun, sometimes fixed facing south); and the electrical wiring and connection equipment. If utilized, any storage components (usually batteries) and any backup generation also are included in the BOS. A comprehensive listing of BOS includes:
• Foundation (including tracking systems)
• Sitting & Permitting
• Electrical Wiring
• Electrical Protection & Safety Equipment
• Start-Up & Testing
• Electrical Interconnection & Metering
• Data Monitoring
• Communications & Control
• Operation & Maintenance
• Homeowner Training
Both AC and DC systems will have a foundation and support structure for the PV array. The type and construction are dependent on the type of mounting used as in either ground-mounted or roof-mounted, the size of the array, local wind and snow loading conditions, the tilt of the array, and if any type of tracking is utilized. Fixed mounting– that is, mounting an array south-facing at a fixed tilt– is usually the least expensive method and requires no moving parts. The tilt of a fixed array is dependent on the sunlight and load match– for summer peak loads the tilt is usually at latitude or slightly less than site latitude; for winter loads, the tilt may be at higher angles than the latitude. The solar array may also be oriented toward the southwest or even the west to obtain load coincidence.
Roof jack techniques have proven to be a popular and cost-effective mounting for PV modules on both flat and slanted roofs. This system uses a ballasted pan for attachment to a flat roof or is directly bolted to a slanted style roof.
Tracking the sun will increase the energy output of the array, but at a cost and complexity. The purchase price, along with the installation and maintenance costs of a tracking system, must be compared to the energy output of a particular application to see if this is cost effective alternative.
See You Next Time! Dr. Stripling