t's easy to feel overwhelmed when you're just getting started with solar. But even if your knowledge is for now limited, it won’t take a lot of time to figure it all out. Our guide gives you a brief intro to residential photovoltaics, shows how you can harvest the sun’s power at home and what PV module options you have.
What are solar power modules?
A solar power module system, also called a solar panel, is a device that captures sunlight and transforms it into usable power. This device is usually made of PV cells, wiring, a glass protective covering, and a metal frame. Typical residential models are about three feet wide, and 5.5 feet tall.
Most homeowners choose to install solar on the roof, which allows them to collect as much sunlight as possible, minimize shading and avoid taking up space on their site. But sometimes rooftop installation isn’t an option due to a lack of available surface area, or a shaded or weak roof. If that is the case, you can choose to install a ground-mounted PV system. This solution has limitations as well, for example, it requires a lot of open space with good sun exposure. However, it enables a homeowner to freely choose the tilt and orientation of a PV module.
How do photovoltaic cells generate electricity?
Now let’s take a quick look at how sunlight is converted into electricity to power our homes. As already mentioned, a PV module consists of interconnected PV cells – the smallest units responsible for generating power. These cells are usually made from silicon due to its cost-efficiency and superior electronic properties.
There are two layers of silicon within one solar cell, one being doped with an atom that has three valence electrons (typically boron), and the other with a five-valent atom (arsenic or phosphorus). Putting these two layers in a junction is what creates an electromagnetic field.
As soon as the light reaches the surface of the PV cell, the electrons are kicked out of their standard positions and come into motion. When they pass through the junction between the silicon layers, an electric current is generated.
Most solar panels on the market have 60 or 72 PV cells, with 60-cell models being more common for residential applications.
Types of solar panels
Most residential solar panels available today fall into three categories: monocrystalline, polycrystalline, and thin-film. Let’s quickly run through their distinctive features.
A monocrystalline solar panel module is composed of monocrystalline silicon cells. These PV cells are manufactured using a single high-purity crystal of silicon, due to which they appear black in color.
Monocrystalline cells are the most efficient of all types converting 17-20% of solar power into electricity, which is why they are considered a high-end product. In addition to this, monocrystalline options usually have a higher power output rating of 320 to 375 watts.
These modules generally enjoy a longer lifespan and perform better at high temperatures. The only substantial drawback is the price: monocrystalline products cost from $1 to $1.50 per watt, so an average 6kW PV system would range from $6,000 to $9,000.
Polycrystalline cells, as you can guess by the name, are manufactured from multiple crystals of silicon. Polycrystalline solar installation can be recognized by its blue tint which appears due to the way light is reflected off the boundaries of numerous crystals.
Polycrystalline options typically have a lower efficiency rating of between 15% and 17%, as the crystal boundaries prevent the electrons from moving as freely as they do within a monocrystalline cell. Polycrystalline PV modules are also less heat-tolerant and have a shorter lifespan. They are nevertheless considerably cheaper: with the average cost being $0.90-$1 per watt, the standard price of the whole PV system ranges from $5,400 to $6,000.
Thin film is a second-generation solar technology that is based on a different principle than conventional crystalline solutions. Unlike their monocrystalline and polycrystalline counterparts, these panels are composed of multiple thin layers of photovoltaic materials deposited on a flexible substrate. This manufacturing method makes them pliable and thus suited for uneven surfaces, such as curved buildings. Another advantage is lighter weight, thanks to which the modules are much easier to transport and install.
But unfortunately, thin-film systems fall behind in terms of efficiency. Even though some experimental prototypes showcase performance comparable to crystalline, most thin-film modules are only up to 15% efficient.