simplified installations, making it easy to add panels to an installa- tion. Each solar module is paired with its own micro inverter, which then coverts the power directly at the panel. In off-grid installations the use of a charge controller is necessary to properly manage the power harvest, charge the batteries, and prevent overcharging. The greatest innovation in charge controllers would have to be
the relatively new feature called Maximum Power Point Tracking (MPPT). This method of charging batteries constantly monitors peak power voltage from the array and input voltage on the batteries and adjusts amperage to compensate for the fluctuations. This provides the most efficient means to manage the power harvest. The function of MPPT charge controllers is analogous to the transmission of a car, keeping your charging system in the ‘right gear’. Other components of the solar system include wiring and mounting hardware, and some installations use a tracker that changes the tilt angle and direc- tion of the panels throughout the day.
Types of Solar Panels
Solar panels are classified into three classes: mono-crystalline (single crystal), poly-crystalline (multiple crystals), or amorphous sili- con. Mono-crystalline use a continuous, unbroken sample of silicon. This method uses very pure silicon grown in a complex growth pro- cess, and then sliced into wafers that compose the individual cells. This was the first method used to manufacture solar cells, and is still highly regarded because of its efficiency ratios. Poly-crystalline panels are composed of many crystallites of
varying size and orientation. These multi-crystalline panels are gen- erally less expensive and slightly less efficient than mono-crystalline modules, yet lately the difference in efficiency is very small. Like their mono-crystalline counterpart, the cells are also cut into wafers that make up the individual cells of a solar panel. Amorphous solar panels use the non-crystalline, allotropic form of silicon, in which a thin layer of silicon substrate is applied to the back of a plate of glass. These panels are much cheaper and less energy efficient, yet they are more versatile in how they can be used. For example, amorphous solar panels can be manufactured into long sheets of roofing material. Thin Film solar panels also fall into the amorphous category. These cells can be mounted on a flexible back- ing, making them more suited for mobile applications. Each of the solar panel types is estimated to last at least twenty-
five years. Electricity production declines gradually over decades. The longevity of a solar panel refers to the number of years before
the unit starts producing only 80 percent of its original power rating. The industry standard for warranties is 20 to 25 years, although it is not uncommon for panels to produce adequate power for more than 30 years.
Off-Grid versus Grid-Tied
Solar panels are used extensively in rural areas, where access to the grid is non-existent or inaccessible. These installations are called off grid (or independent, stand-alone) solar power systems, and require the use of batteries to store the energy for use at night or on long stretches of overcast weather. The energy stored in the batteries leaves the batteries as DC electricity which can power DC appli- ances (as in RVs) or be converted to AC for use with conventional appliances. Much like running your own mini utility company, this method gives you full independence from the national grid. You can eliminate the cost of batteries by going with a system that connects right into your home’s main junction box and use the
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