Typically, to determine the performance of a solar station, panels of appropriate power are selected, regardless of the production technology, basing only on efficiency of the panels under standard test conditions (STC).
How true is this? After all, the efficiency of the panel is a variable value, and in fact depend on cell temperature as well. On the solar panels datasheet is indicated still so-called temperature coefficients describing the change in panel characteristics as a function of temperature. Temperature coefficients of modern panels may be different or the same for polycrystalline and single crystal panels the panels, but generally they have monocrystalline panels slightly lower and approximately varies in the range 0.3-0.4% / ºK and polycrystalline panels in the range 0.39-0.5% / ºK. To date, the Chinese company JinkoSolar already achieved efficiency up to 22.04% for polycrystalline panels and 23.95% for the single-crystal panels, with both the record values achieved using the p-type cells. So, as we see, the efficiency of polycrystalline panels can also be quite high. Anyway, which panels should be preferred for the same power of installation? Regarding this, you can meet completely different opinions. We also asked this question and decided to test it in practice. We have established solar station with the total capacity of 20.95 kW, consisting of two parts, first one consisted of 38monocrystaline panels of 275 W with total capacity of 10.45 kW, and the second part consisting 40 of polycrystalline 250W panels, with total capacity of 10.50 kW. All the panels hase been mounted on ground supports at the same angle 40 at a distance of 10 meters from each other and connected to two identical ON-GRID inverters from the Chinese company GoodWe.
The station has been operating for 4 months and so far, we see almost an absolutely same energy output of these two stations. If we talk about the later aging (degradation) of monocrystalline panels, to be honest, there is no reliable data too. Perhaps, the only advantage is saving area, but this is the result of greater efficiency, but not solar cell’s technology.
Author: V. Sharafian