May 21, 2019
What is the best type of photovoltaic panels?
This is the question that dominates all those who have even dealt with the subject of photovoltaic installations.
It is clear that no one can give an easy or single answer to this question because there are several different factors affecting each photovoltaic installation, others less and more (for example height of sunshine, spatial peculiarities, meteorological conditions, cost, orientation, shades, etc.). Following the article, we will attempt to briefly outline the key features of each type so as to make their differences as clear as possible.
How are the photovoltaic panels manufactured?
The material most used for the construction of photovoltaic cells in the industry is silicon. It is perhaps the only material produced in such a massive way. Today’s silicon is the raw material for 90% of the photovoltaic market (photo 1).
The most important advantages of silicon are:
-It can be found very easily in nature.
-It is the second most abundant material on the planet after the oxygen.
-It can easily melt and mold.
– Its electrical properties can be maintained up to 125 ° C, which allows the use of silicon in particularly difficult environmental conditions. This is why the silicon photovoltaic elements meet a particularly wide range of temperatures. Silicon, depending on its processing, yields monocrystalline, polycrystalline or amorphous materials from which photovoltaic cells (cells) are produced.
Photovoltaic panels typically consist of:
-Solar glass with pre-mounted specially processed protective film (EVA). It is essentially a hardened, pre-stretched solar glass.
-Solar photovoltaic cells connected in strings.
– A special processing glass (EVA) as well as an insulating membrane on the back side. All three layers create a durable, weather-resistant laminated sheet which is placed in an aluminum fixing frame and a connection socket (photo 2).
Performance level
The “performance” reported for each panel type is essentially the percentage of solar energy that converts to electricity. Efficiency ranges from 6% -19% today. Categories of photovoltaic panels Monocrystalline photovoltaic panels: Manufactured from blanks cut from a single large cylindrical silicon crystal.
Their construction is more complex, resulting in higher production costs (photo 3, 4). Characteristics:
-It is the first type of photovoltaic panels to be mass-produced.
– They have a better performance / surface ratio than other panel types.
– Their energy efficiency ranges from 11% to 19%
– They have higher production costs than polycrystalline panels.
-They have a greater material thickness.
-There are dark blue or black.
Polycrystalline photovoltaic panels:
They are made of thin-cut blanks of molten and recrystallized silicon bars (molten silicon is poured into a mold and then cut into blisters) (photo 5).
Characteristics:
-The method of producing them is cheaper than monocrystalline, so their price is usually a bit lower.
– Their energy output ranging from 11% to 16% is relatively lower than that of monocrystals, but once the cells are placed in a panel with another 60, the actual difference in watt per square meter is negligible. Today, with the rapid development of technology, their performance tends to touch the performance of monocrystals.
– They are the most widely used panels in the world.
-It has the best cost-effectiveness.
– They are blue in color.
Thin film: This is a wider category, which includes the so-called “third generation” panels derived from many different production and processing methods (eg, amorphous silicon (a-Si), copper bisindoindium (CuInSe2 CIS), Cadmium Tetrachloride (CdTe), Gallic Arsenic (GaAs), etc.). The amorphous silicon panels, which are the most widespread of this class, are made of thin film tapes produced by depositing semiconductor material (silicon in our case) on a low-cost backing substrate such as glass or aluminum. The characterization of an amorphous photovoltaic arises from the random manner in which the silicon atoms are arranged (photo 6).
Characteristics:
– They have, nominally, lower yields than the other categories (6% to 11%). Because of the smallest amount of silicon used in their production, their price is considerably lower.
-For better at high temperatures.
-The thin film panels have better yields than crystalline photovoltaics when there is diffuse radiation (cloudy).
– They have low energy density which means that in order to produce the same energy we need almost twice the surface area compared to the crystalline photovoltaic elements.
– There are no data from old facilities, about yields and their duration, since their technology is relatively new.
-It is a good solution when available: large available space, shading, unfavorable orientation.
Hybrid panels:
These panels combine more than one of the known technologies (eg combination of amorphous and monocrystalline silicon) In the market, the most widely distributed panels of this category are made of two layers of amorphous silicon around a layer of monocrystalline silicon photo 7).
Characteristics:
– They have a high yield that can reach as much as 19%.
-Have very good behavior in the effect of temperature and remarkable performance in diffused lighting.
-It has much higher manufacturing costs.
– There are no data from old facilities, about yields and their duration, since their technology is relatively new.
Cost-to-Cost Comparison
The results from three plants with identical specifications (place of installation, orientation, power output), but with three different types of panels (monocrystalline, polycrystalline and thin film), show in practice the nominal differences of their characteristics as described above. For example, the annual yield in kWh for all three types is not significant. Substantial differentiation lies only in the required square meters for panel placement, and only for one of the three categories. The differences in the cost of such an installation are also very small, as shown below.
Installation cost for a 9.9 kWp power system
In Table 1 below, all the simulation features of the installation are analyzed.
Conclusions
Reading the nominal technical characteristics of each class over and over, together with their cost features, does not reveal a single element that turns our selection into a particular category. Odds are pretty much the same and costs too. Therefore, the selection of photovoltaic panels has to do with the particularities of each installation separately and, when we say particularities, we mean the place of installation, the available space, the orientation and the inclination of it and perhaps also the personal color choice black or blue). The decision to choose a photovoltaic system will definitely help the installer we chose, because we will have to analyze and include in the study all the features and special features of the installation so that it will achieve the optimal result for your investment.
