Choose your political party or illegal organization and try to overthrow the powers that be by force, revolution or democratic election! Control the opposition forces, manage the party budget, talk to the media, take a position on legislative bills, start protest movements, win your independence, infiltrate the spheres of power, raise an army with the help of foreign countries or illegal groups and conquer all the territory or the capital city! The player can also construct elements on the world map, which will change accordingly: nuclear plants, wind farms, military bases, pipelines, high-speed train lines, airports, and many more.
The crack issue in solar cells becomes worse as the thickness of the wafer is being reduced5. This is the case because the reduced thickness makes it easier to develop extra mechanical stresses in the cells when assembled into a full-scale PV module. Often, this will cause cracks in the cells and lead to up to 2.5% power degradation in 60-cell PV modules if they do not insulate cell areas. In a relevant study6, cracks have been proven to impact the surface structure of the solar cells and extend to damage the fingers and busbars. This would lead to disconnecting cell areas and reducing the maximum generated current. In the recent work by7,8, they have shown that solar cell cracks can not only isolate parts of the cells but also, and due to the nature of the cracks themselves, they can develop a localized increase in the temperature, resulting in what is commonly known by "solar cell hotspots".
power world simulator 16 crack
The mitigation of solar cell cracks has not been yet discovered. However, as cracks lead to hotspots, there were some attempts to mitigate hot spotted solar cells by utilizing a power electronics device to regulate the current into the affected cells9,10,11,12. These techniques work under the same principle by adding a switching element with high frequency to control the current in the modules and do not affect the interconnection between the module and the power converter. These techniques were approved effective, and they can increase the PV modules output power.
The PV modules are usually connected in series for grid-connected PV systems to build up the voltage output, and the modules frames are grounded for safety purposes13,14. A high electric potential difference between the cells and the module farm may be induced in the modules, typically at the PV string level. This phenomenon will result in a leakage current flow from the module frame to the solar cells, which results in a potential induced degradation (PID)15,16,17. Therefore, solar cell cracking and PID are different; however, both lead to a drop in the output power of the modules.
Cracks are often invisible to the bare eye; the current standard cracks detection method uses Electroluminescence (EL) imaging18,19,20. In Fig. 1, the EL image of two different solar cells is presented. Here we show the difference between the EL image when a solar cell is affected by cracking and structural defects (Fig. 1a) and when the cell is affected by PID (Fig. 1b). There has been a limited explanation of the behaviour of these cracks on the actual degradation of the output power and their correlation to the presence of hotspots. In addition, to date, there is a lack of understanding of whether all types (or crack percentages) can lead to a significant drop in the output power generation of solar cells.
To date, there is still a gap of knowledge in understanding the impact of cracks on solar cell performance, particularly those exposed in the field under different environmental conditions. Usually, and as explained in multiple previous studies21,22,23, cracks can degrade the PV output power under controlled indoor testing; these various studies, however, do not consider the influence of the size of the cracks and the correlation between the cracks and their thermal impact on the PV modules. In addition, some other recently published work24,25 has shown that PV cracks can influence the electrical parameters of the PV modules, while they did not precisely evidence whether the cracks purely cause this degradation in the module, as PV modules exposed in the filed can be affected by other degradation mechanisms such as potential-induced degradation26, bypass diodes failure, hotspots, or temperature-induced degradation (TID)27.
Considering these research gaps of knowledge, the main contributions of this paper are to provide an understanding of how the output power degradation in solar cells is affected by different sizes of cracks. In addition, the correlation between solar cell cracks and the development of hotspots will also be discussed. Our last contribution is to correlate PID vs cracked solar cells' power losses and resemble their thermal performance.
This work explores crystalline silicon (c-Si)-based solar cells affected by different sizes of cracks. The studies cells are made of three busbars, and as provided by the manufacturer datasheet, under standard testing conditions (STC), each cell has an open-circuit voltage \(V_oc\) of 0.61 V, short circuit current density \(J_sc\) of 38.8 mA/cm2, and peak power 4.72 W.
As can be observed in Fig. 5b, there is a significant correlation between the output power of the reference cell and the solar cells affected by 1%, 3%, 7% and 11% crack percentages. The mean output power is approximately equal to the reference cell, 2.571 W. In contrast, we observe a significant decay in the mean of the output power while the crack percentage in the solar cell increases. For example, the solar cell affected by 20% has a mean output power of 2.051 W, compared with 0.9708 W identified from the last solar cell sample with a crack percentage of 58%.
In addition, as the crack percentage increase in the solar cell, it is anticipated that the standard deviation of the output power measurements decreases. A low standard deviation indicated that the values are clustered close to the mean. Hence, even though the irradiance increased while experimenting, there were no significant changes in the output power of the critically cracked solar cells (i.e., 46% and 58% crack percentages).
We compared the results of the output power of the cracked solar cell with the reference cell that has been already operated in the field. Consequently, there should be some additional losses/degradation in the output power anyways.
According to Fig. 6a, the solar cells with crack percentage below 15% are above the -10% baseline. This result suggests that the output power losses for the solar cells with crack percentages of 1%, 3%, 7%, and 11% is insignificant. We confirm the same outcome while testing with the solar samples at 0.5 Sun, as shown in Fig. 6b. Accordingly, these results enable us to understand that not all cracks in solar cells could induce output power losses. Small cracks, i.e., below 10%, unlikely influence the output power generation and are relatively equivalent to non-cracked cells. In a comparative evaluation, the output losses (or degradation) are likely to transpire due to other predicaments such as encapsulation, arcing-faults, or PID.
Even though the cooling mode of the solar illuminator was set up at 25, the solar cells have not been left under illumination for a long time to ensure that no rapid increase in the temperature occurs. In addition, following this procedure will guarantee that the temperature increase in some of the tested solar cells results from the cracks, not because of the rapid illumination of the sun simulator.
While understanding the results presented in this section, we realized that there might be a substantial similarity between the cracks and the original PID effect in output power losses and hotspots development. This correlation has been investigated, and the analysis is discussed in the next section.
It is apprehended that PID is an utterly different degradation mechanism than cell cracking. PID results from a high voltage electric field and sodium Ion migration from the PV module glass to the cells29, while solar cell cracking occurs due to thermal and mechanical stresses30. Therefore, this section will present the output power losses of PID affected solar cells; the results will then be compared with the output power losses of the solar cell cracks discussed in the previous sections. This examination will demonstrate that solar cells' PID effect is not as severe as when cracked by 40% or more.
The PID test was performed using the PIDcon instrument. We have applied the standard PID testing conditions, where the temperature is maintained at 85 C, the voltage is set to negative 1000 V, and the PID test ran over 96 h28. This procedure was performed on two solar cell samples that presents no cracks, shown in Fig. 9a,b. These figures also contain the EL image taken before and after performing the PID test. Apparently, the PID had a significant impact, as expected, toward developing shunted areas in the cells. Furthermore, the output power measurements for the solar cell samples before and after the PID test are presented in Fig. 9c. After the PID experiment was completed, it is seen that the mean output power has significantly dropped for both samples, 1.909 and 1.801 W.
Calculation of the output power loss for the solar cell samples after PID test was completed, the results are also compared with the measurements taken from the cracked solar cell samples earlier shown in Fig. 6 (a) at 1 Sun, (b) at 0.5 Sun.
Another contribution of this work is that we have presented the results of the output power degradation of two solar cell samples under the PID test. We have then correlated the power losses of the PID test results with the cracked solar cell samples. We have discovered that PID can result in 30% to 40% losses in the output power; this is pretty much the same amount of losses when a solar cell is affected by at least 25% cracks. Our results of the PID effect are similar to previous work26,27. However, the actual correlation between cracks, hotspots, and PID has not been yet investigated other than in this paper. 2ff7e9595c
Comments