Types of Solar Panels: Pros and Cons
|Advantages and disadvantages of the three main types of solar panels|
|Monocrystalline solar panels||Polycrystalline solar panels||Thin film solar modules|
|material||Pure silicon||Silicon crystals melted together||A variety of materials|
|Creation of the carbon footprint||38.1 g CO2 eq / kWh||27.2 g CO2 eq / kWh||Already 21.4 g CO2 eq / kWh, depending on the type|
Monocrystalline solar panels
Monocrystalline solar modules are the most widely used solar modules on the market today because of their many advantages. About 90% of the solar cells sold today use silicon as a semiconductor material. Silicon is abundant, stable, non-toxic, and works well with established power generation technologies.
Originally developed in the 1950s, monocrystalline silicon solar cells are manufactured by first producing a high-purity silicon block from a pure silicon seed using the Czochralski method. A single crystal is then cut from the ingot resulting in a silicon wafer that is approximately 0.3 millimeters (0.011 inches) thick.
Monocrystalline solar cells are slower and more expensive to manufacture than other types of solar cells because of the precise way in which the silicon blocks must be made. In order to grow a uniform crystal, the temperature of the materials must be kept very high. As a result, a large amount of energy must be consumed due to the heat loss from the silicon seed that occurs throughout the manufacturing process. Up to 50% of the material can be wasted during the cutting process, resulting in higher production costs for the manufacturer.
However, these types of solar cells maintain their popularity for a number of reasons. First, they are more efficient than any other type of solar cell because they are made from a single crystal, which makes it easier for electrons to flow through the cell. Because they are so efficient, they can be smaller than other solar panel systems and still generate the same amount of electricity. They also have the longest lifespan of any type of solar panel on the market today.
One of the biggest disadvantages of monocrystalline solar modules is the cost (due to the production process). In addition, they are not as efficient as other types of solar panels in situations where the light does not hit them directly. And when they are covered with dirt, snow or leaves, or when they work at very high temperatures, their efficiency decreases even more. While monocrystalline solar modules are still popular, the low cost and increasing efficiency of other module types are becoming increasingly attractive to consumers.
Polycrystalline solar panels
As the name suggests, polycrystalline solar modules are made up of cells made up of multiple unaligned silicon crystals. These first generation solar cells are made by melting solar grade silicon, pouring it into a mold, and allowing it to solidify. The molded silicon is then cut into wafers for use in a solar panel.
Polycrystalline solar cells are cheaper to manufacture than monocrystalline cells because they do not require the time and energy required to create and cut a single crystal. And while the boundaries created by the grains of silicon crystals create barriers to the efficient flow of electrons, they are actually more efficient than monocrystalline cells in low light and can maintain performance unless they are tilted directly into the sun. Because of this ability to keep generating electricity under adverse conditions, they have roughly the same total energy production.
The cells of a polycrystalline solar module are larger than their monocrystalline counterparts, so the modules may take up more space to generate the same amount of electricity. They are also not as durable or long-lasting as other types of panels, although the differences in durability are small.
Thin film solar modules
The high cost of producing solar grade silicon led to the creation of various types of second and third generation solar cells known as thin film semiconductors. Thin-film solar cells require a smaller volume of material, often using a silicon layer with a thickness of only one micrometer, which corresponds to about 1/300 of the width of mono- and polycrystalline solar cells. The silicon is also of a lower quality than that used in monocrystalline wafers.
The first thin-film solar cell was made from non-crystalline amorphous silicon. Because amorphous silicon does not have the semiconducting properties of crystalline silicon, it must be combined with hydrogen to conduct electricity. Amorphous silicon solar cells are the most common type of thin film cell and are widely used in electronic devices such as pocket calculators and watches.
Other commercially viable thin film semiconductor materials include cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and gallium arsenide (GaAs). A layer of semiconductor material is deposited on an inexpensive substrate such as glass, metal, or plastic, making it cheaper and more adaptable than other solar cells. The absorption rates of the semiconductor materials are high, which is one of the reasons why they use less material than other cells.
Thin film cells are much easier and faster to make than first generation solar cells, and there are a variety of techniques that can be used to make them, depending on the skill of the manufacturer. Thin-film solar cells such as CIGS can be deposited on plastic, which significantly reduces weight and increases flexibility. CdTe is the only thin film that has lower cost, longer payback time, lower carbon footprint and lower water consumption over its lifetime than any other solar technology.
However, the disadvantages of thin film solar cells in their current form are numerous. The cadmium in CdTe cells is highly toxic if inhaled or ingested and can end up in the soil or water supply if not properly handled during disposal. This could be avoided if the panels are recycled, but the technology isn’t as widespread as it needs to be right now. The use of rare metals such as in CIGS, CdTe and GaAs can also be an expensive and potentially limiting factor in the manufacture of large quantities of thin film solar cells.
The variety of solar modules is much greater than currently on the commercial market. Many newer types of solar technology are under development and older types are being studied for potential efficiency gains and cost reductions. Some of these new technologies are in the pilot phase of testing while others are only being proven in laboratory settings. Here are some of the other types of solar panels that have been developed.
Bifacial solar panels
Conventional solar modules only have solar cells on one side of the module. Bifacial solar panels have solar cells built on both sides so that they can collect not only incident sunlight, but also albedo or reflected light from the ground below them. They also move with the sun to maximize the time sunlight can be collected on either side of the panel. A study by the National Renewable Energy Laboratory showed a 9% increase in efficiency compared to single-sided panels.
Concentrator photovoltaic technology
Concentrator Photovoltaic (CPV) technology uses optical devices and techniques such as curved mirrors to inexpensively concentrate solar energy. Because these modules concentrate sunlight, they don’t need as many solar cells to produce the same amount of electricity. This means that these solar modules can use higher quality solar cells at a lower overall cost.
Organic photovoltaic cells use small organic molecules or layers of organic polymers to conduct electricity. These cells are lightweight, flexible, and have a lower overall cost and environmental impact than many other types of solar cells.
The perovskite crystal structure of the light harvesting material gives these cells their name. They are inexpensive, easy to manufacture and have high absorption. They are currently too unstable for large-scale use.
Dye Sensitized Solar Cells (DSSC)
These five-layer, thin-film cells use a special sensitizing dye to aid the flow of electrons that generate electricity to generate electricity. DSSC has the advantage that it works in poor lighting conditions and increases efficiency with increasing temperatures. However, some of the chemicals in it freeze at low temperatures, which makes the device inoperable in such situations.
This technology has only been tested in laboratories, but has shown several positive properties. Quantum dot cells are made of different metals and work on the nanoscale, so their ratio of power generation to weight is very good. Unfortunately, they can also be highly toxic to humans and the environment if not properly handled and disposed of.