About Solar Array

With all these things about getting green and using the proper installation products for energy efficiency, many of us does not know what a photovoltaic array (also called a solar array) is, and what it does in converting solar energy. Perhaps a little information about how this works and its efficiency would somehow help.

The cells convert solar energy into direct current electricity via the photovoltaic effect. The power that one module can produce is seldom enough to meet requirements of a home or a business, so the modules are linked together to form an array. Most PV arrays use an inverter to convert the DC power produced by the modules into alternating current that can plug into the existing infrastructure to power lights, motors, and other loads. The modules in a PV array are usually first connected in series to obtain the desired voltage, the individual strings are then connected in parallel to allow the system to produce more current. Solar arrays are typically measured under STC (Standard Test Conditions) or PTC (PVUSA Test Conditions), in watts, kilowatts, or even megawatts (source: Wikipedia).

 

The costs for this have been dramatically reduced in recent years for more widespread use through production and technological advances. In year 2006 it ranged $3–10/watt while a similar size is said to have cost $8–10/watt in February 1996, depending on type. Others offer bulk discounts for bulk orders (compare solar companies rate).

For example, crystal silicon solar cells have largely been replaced by less expensive multicrystalline silicon solar cells, and thin film silicon solar cells have also been developed recently at lower costs of production yet. Although they are reduced in energy conversion efficiency from single crystalline "siwafers", they are also much easier to produce at comparably lower costs (source: Wikipedia).

Photovoltaic arrays are commonly used on rooftops to supplement power use both in urban and rural areas. It is being connected to the power grid which the energy produced by the PV array can be sold back to the utility in some sort of metering agreement. 

The array that has the look of trees provides shade and at night can also be used as street lights. In agriculture settings, the array may be used to directly power DC pumps, without the need for an inverter. In remote settings such as mountainous areas, islands, or other places where a power grid is unavailable, solar arrays can be used as the sole source of electricity, usually by charging a storage battery (source: Wikipedia). 

There are a lot of factors that affect PV performance. Most photovoltaic cells' electrical output is extremely sensitive to shading. Majority of modules have bypass diodes between each cell or string of cells that minimize the effects of shading and only lose the power of the shaded portion of the array (The main job of the bypass diode is to eliminate hot spots that form on cells that can cause further damage to the array, and cause fires.). When even a small portion of a cell, module, or array is shaded, while the remainder is in sunlight, the output falls dramatically due to internal 'short-circuiting' (the electrons reversing course through the shaded portion of the p-n junction).

Thus, this suggests that a PV installation should not shaded at all by trees, architectural features, flag poles, or other obstructions like continuously parked cars. Sunlight has tendencies to get absorbed by dust, fallout, or other impurities at the surface of the module and this could lead to cut down the amount of light that actually strikes the cells by as much as half or more. By keeping the module surface clean, it will increase output performance over the life of the module. Module output and life are also degraded by increased temperature. Allowing ambient air to flow over, and if possible behind, PV modules reduces this problem.