How Solar Works

Solar Cells

Solar cells are small, square-shaped panel semiconductors made from silicon and other conductive materials, manufactured in thin film layers. When sunlight strikes a solar cell, chemical reactions release electrons, generating electric current. Solar cells are also called photovoltaic cells or “PV cells” and can be found on many small appliances such as calculators.

Solar Photovoltaic (PV) System Components

A PV system components include PV modules (groups of PV cells), which are commonly called PV panels; one or more batteries; a charge regulator or controller for a stand-alone system; an inverter to covert solar power from direct current (DC) to the alternating current (AC) of the utility grid-connected system; wiring; and mounting hardware or a framework. A PV module arranges individual PV cells, and the modules are grouped together in an array. Some of the arrays are set on special tracking devices to follow sunlight all day long and improve system efficiency.

PV System Installation, Maintenance, and Longevity

You could install a photovoltaic (PV) or solar electric system yourself. But to avoid complications or injury, you will probably want to hire a reputable professional contractor with experience installing solar systems. While they are sophisticated electric systems, PV systems have few moving parts, so they require little maintenance. The basic PV module (an interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years while requiring little maintenance. The components are designed to meet strict dependability and durability standards to withstand the elements. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. Most PV system problems occur because of poor or sloppy system installation.

Incorporating PV Systems into Your Home and Business

PV systems today can be blended easily into both traditional and nontraditional homes, powering appliances and electric systems. PV cells can be installed as a stand-alone module that is attached to your roof or on a separate system, or using integrated roofing materials with dual functions – that as a regular roofing shingle and as a solar cell making electricity. The most common practice is to mount modules onto a south-facing roof or wall. PV systems likewise can be blended into virtually every conceivable structure for commercial buildings. You will find PV used outdoors for security lighting as well as in structures that serve as covers for parking lots and bus shelters.

Sunlight Requirements for PV Systems

A photovoltaic (PV) system needs unobstructed access to the sun’s rays for most or all of the day to be effective. Shading on the system can significantly reduce energy output. Climate is not a major concern because PV systems are relatively unaffected by air temperatures, and snow cover typically melts quickly because panels are positioned directly into the sunlight.

The Size of Your Solar PV System

The size of your solar system depends on several factors such as how much electricity or hot water or space heat you use, the size of your roof, how much you’re willing to invest, and how much energy you want to generate.

Crystalline panels are the most common type of PV panel. The technology has been around for about 50 years and was first developed for powering satellites. They are capable of being up to 20% efficient. Most of these technologies are highly reliable (25 year warranties are common) and produce similar results in terms of output efficiency. The primary downsides of using crystalline are that they can be bulky, expensive, prone to damage, are rigid and require a lot of labor to install. That said, they are often the best choice for a residential solar energy system. They come in two varieties: monocrystalline and polycrystalline.

Monocrystalline silicon panels are made up of single-crystal wafer cells cut from continuous, cylindrical crystal ingots. They can be cut completely circular to minimize waste, but they are often trimmed into other, more square-like shapes. Since each is made from a single crystal, the cells have a uniform, deep blue color. They are the most efficient units available today (they produce more power per square foot), but they cost more than other types.

Polycrystalline silicon panels are made of multi-crystal wafer cells cut from square ingots that are created by pouring molten silicon into a mold. This way they can be cut into square wafers to minimize waste. Each is made up of random crystal formations which make it various colors of blue. They are slightly less energy efficient, but also cheaper than monocrystalline.

Thin film modules are very inexpensive, but also quite inefficient (require more area per watt produced). Their efficiency is 10% or less and their long-term durability is often questioned. They are less expensive because they require less of the active material to function. In fact, they can be made microscopically thin, flexible and light weight and are deposited on a sheet of glass or metal instead of having to grow ingots and slice wafers. Cadmium telluride (CdTe) is the most cost effective thin film technology. Amorphous silicon is a material used to create panels that can be molded to the shape of almost any surface. Most of the research and development of solar cells is currently being focused on thin film technologies. Building integrated photovoltaic (BIPV) panels look like an integral part of a roof since they are the same size and shape as shingles. They have lower efficiency and are more expensive than other panel types. They are most effective on large roofs in very sunny areas.