With quite a few markets reporting issues with overly optimistic P50 estimates, consideration has additionally been drawn to related points with PAN recordsdata. TÜV Rheinland’s Yating Zhang and Christos Monokroussos talk about the topic at size.
In each PV analysis and software areas, persons are aware of PVsyst software program which is usually utilized to evaluate and forecast the power efficiency of PV modules and arrays. The simulation outcomes of PVsyst will additional affect the monetary funding of PV techniques.
An power yield increase of 1% or 2% could convey a number of million or extra revenues for a big system. Subsequently, persons are realising that the accuracy of PVsyst simulation outcomes is worthy of a lot consideration. Other than accuracy associated to the in-build simulation fashions and methodology, the accuracy of enter parameters for every PV module, the so-called PAN file, ends in main discrepancies between simulated and precise power yield.
The customers report that there are lots of overly optimistic PAN recordsdata, and these PAN recordsdata result in overestimated power yield, which lastly will increase the chance of investing and buying and selling within the PV space.
Among the many enter parameters of PAN recordsdata, some attribute information comparable to STC outcomes, low-light information, incident angle modifier (IAM), temperature coefficient (TC) and light-induced degradation loss (LID) should be measured in response to related requirements.
For the event that the measurement information are usually not accessible, some may be retrieved from PV modules’ datasheets, that are based mostly on measurements that the producer has carried out and a few default values of those efficiency parameters are supplied by PVsyst.
The primary are inclined to overestimate PV modules’ efficiency, whereas the latter are empirical values concluded both from the theoretical mannequin or measurement outcomes of a major quantity of PV modules. To precisely take care of PAN recordsdata, there are a number of issues:
1) clarifying the supply of enter parameters, whether or not the enter parameters are supplied by an authorized and respected check laboratory or default values for PVsyst; a dependable supply of PAN file enter parameters is the bottom to make sure the accuracy of the simulation outcomes;
2) understanding the definition of every enter parameter, such because the sequence resistance or shunt resistance utilized in PAN recordsdata; the sequence and shunt resistance are comparatively delicate parameters and whose values could depend upon their definition and extraction strategies.
In different phrases, it signifies that the extracted sequence resistance or shunt resistance could also be right, nevertheless, they might not be the only option to slot in the modelling strategies utilized in PVsyst. The optimum sequence resistance or shunt resistance values for PAN recordsdata ought to be extracted from the one-diode mannequin and additional optimised by efficiencies beneath numerous irradiances to make sure that the accuracy of power yield prediction is appropriate.
Within the following sections, the definition of some necessary enter parameters for PAN recordsdata and the comparability of simulation outcomes between utilizing measured and default enter parameters will likely be defined intimately.
Low-light information
It’s recognized that the PVsyst is modelling PV module efficiency based mostly on the one-diode circuit mannequin with 5 unknown parameters (photocurrent, diode inverse saturation present, sequence resistance, shunt resistance and diode high quality issue), and the compulsory enter information for figuring out these unknown parameters are {the electrical} parameters beneath STC (short-circuit present, present and voltage at most energy level and open-circuit voltage).
Underneath the situation the place solely STC information can be found, operators can solely select the default values of sequence and shunt resistance, the setting technique of which is deduced by PVsyst. The low-light information is an optionally available enter information; nonetheless, it offers important details about {the electrical} efficiency of PV modules beneath low irradiance and can assist optimise the sequence resistance and shunt resistance in response to the precise traits of PV modules beneath numerous irradiance situations.
Underneath completely different irradiance, the comparability of simulated most energy values of 1 mono c-Si PV module extracted with and with out low-light information is proven in Determine 1, and the measured most energy beneath the corresponding irradiance is the benchmark to estimate the accuracy of simulated most energy. Some deviations inside 0.2% exist for the simulation outcomes extracted with low-light information included. Nonetheless, it’s apparent that the accuracy of simulated most energy will get worse with out inputting low-light information, and simulating deviation as massive as 1.1% was noticed for the irradiance of 200W/m2.
This simulating deviation could range with the PV module sort, as completely different PV modules exhibit distinguishable low-light efficiency. Determine 2 reveals abstractly the comparability of roughly 100 PV module sorts by way of relative effectivity with the efficiency at STC as a reference. The outcomes confirmed that the relative effectivity losses related to low irradiances beneath 400W/m2 had been noticed for all PV sorts. Even for a similar know-how group, the variability within the relative effectivity of PV modules may be vital particularly for the low irradiances, with commonplace deviation of know-how variation various from 2.23%, okay=2 for mc-Si PV modules to five.43%, okay=2 for mono c-Si PV modules at 100 W/m2.
Incident angle modifier
IAM is one other optionally available enter information for filling the PAN recordsdata. When PV modules function outside, they’re topic to diffuse angular profiles which will introduce vital optical losses. The facility losses because of incidence angles had been to be not less than 3% for a PV station yearly [1, 2]. Because the optical losses are affected by many elements, comparable to inactive supplies (glass or EVA), or the SiNx overlaying photo voltaic cells, the IAM is a novel attribute for every PV module product. Therefore, inputting the measured IAM for every PV module is advisable for rising the accuracy of the simulation. For the case with out measured IAM, PVsyst additionally offers a number of units of default IAM values assorted by the kind of entrance floor of PV modules.
Determine 3 reveals the discrepancy of simulated most energy (PMAX) extracted with measured and default values for the AR coating floor. The measured IAM was counted from the measurement information of round 100 c-Si PV modules, they usually had been moreover sorted by the manufacturing 12 months. The IAM check was carried out within the ISO/IEC 17025 accredited PV laboratory of TÜV Rheinland in Shanghai in response to the related contents in IEC 61853-23 [3]. As Determine 3 reveals, there’s an rising tendency of most energy deviation together with the incident angles. The utmost deviations are round 5.0% and a pair of.0% for the PV modules manufactured by 2018-2022 and 2016-2017 respectively. This implies when the incident angle is 80°, roughly 5.0% energy output could also be underestimated through the use of the default IAM for PVsyst. It is usually noticed that the default IAM is comparatively conservative in contrast with the precise IAM of PV modules manufactured in recent times, so the default IAM for PVsyst ought to be optimised to match the newest improvement of PV applied sciences.
Temperature coefficient
A photovoltaic module within the subject isn’t working at a relentless temperature. Many of the incident photo voltaic power which fails to be transformed into electrical energy dissipates as warmth, resulting in an elevated module temperature and worsened efficiency. Temperature coefficients are measured to characterise the impact of thermal behaviour on the efficiency of PV modules, and they are often additional utilized to foretell the power output of PV modules beneath numerous temperature situations.
Typically, the temperature coefficients are particularly sorted into the temperature coefficient of ISC, VOC and PMAX. The temperature coefficients of VOC and PMAX are usually adverse, whereas the other situation for the temperature coefficient of ISC. In response to a major quantity of measurement outcomes of c-Si PV modules, the temperature coefficient of ISC primarily distributes between 0.02%/ºC and 0.07%/ºC, and the vary of temperature coefficient of VOC and PMAX are [-0.35, -0.25]%/ºC and [-0.48, -0.25]%/ºC respectively [4]. The temperature coefficient of PMAX is taken for example right here. Determine 4 reveals the temperature coefficients of PMAX for 78 c-Si PV modules measured within the ISO/IEC 17025 accredited PV laboratory of TÜV Rheinland in Shanghai.
Primarily based on the one-diode mannequin for PVsyst, the impact of temperature issue on the ability output is projected to the transformation of photocurrent and diode inverse saturation present together with temperature. The muIsc outlined because the temperature coefficient of ISC in PVsyst is ready for the temperature correction of photocurrent. The muPmpp outlined because the temperature coefficient of PMAX can both be specified by the consumer or set with the default worth for PVsyst. Primarily based on the enter muPmpp, the temperature correction issue on diode high quality issue (muGamma) could be deduced routinely by PVsyst, after which be utilized to simulate the inverse saturation present beneath numerous temperatures. The default temperature coefficient for PMAX of c-Si PV modules is -0.32%/ºC. Determine 5 reveals the deviations of most energy extracted with measured and default temperature coefficient of PMAX. The utmost energy discrepancy will increase together with the magnitude of temperature deviation from 25ºC, and it could be as massive as 8% for the temperature of 70ºC. Even for the muPmpp of -0.28%/ºC which is analogous with the default muPmpp worth, the deviation of most energy can enhance to round 2% for the temperature of 70ºC.
Mild-induced degradation loss
Mild-induced degradation (LID) refers to a efficiency and energy lack of photo voltaic cells as a result of extra service injection by illumination or ahead biasing [5, 6]. Most industrial c-Si photo voltaic cells and modules are affected by some sort of LID. In PVsyst, the LID loss is one sort of array losses in PV techniques and specified to analyse the PV array losses.
The LID phenomenon has been studied for 4 a long time because it was first noticed in Czochralski-grown c-Si units within the Nineteen Seventies [7]. A number of LID degradation sorts have been noticed comparable to boron-oxygen advanced activation (BO-LID), Copper-related (Cu-LID), iron-boron pair dissociation (FeB-LID) and mc-PERC LID [8-10]. Amongst these degradation sorts, BO-LID is essentially the most recognised degradation impact, which is often noticed in clear boron-doped Cz-Si. Lately, gallium has been launched as a dopant as a substitute of boron, which leads to decrease LID losses. In distinction to the degradation attributable to gentle publicity, a metastable relative effectivity enhance seems in HJT photo voltaic cells with doped a-Si:H/c-Si constructions beneath gentle soaking [11].
The outcomes of relative effectivity (to preliminary) towards cumulative irradiation dose for various module sorts at STC are illustrated in Determine 6. The relative effectivity losses of all of the PV modules because of LID stays inside 3.5% after gentle soaking of 15 kWh/m2. Mono c-Si, mc-Si, and c-Si PERC samples confirmed a median LID of 0.70%, 1.10%, and 0.11% respectively. N-type c-Si samples, nearly all of that are HJT applied sciences with n-type Cz-Si wafer, confirmed a median 0.60% relative effectivity enhance. The usual deviation inside know-how teams was calculated as coefficient of variation (CoV). It’s value noting that the module-to-module variation inside sure know-how was extra vital than the distinction between know-how sorts aside from n-type c-Si sorts. This means that even for related know-how sorts, massive dispersion would exist because of each wafer high quality and manufacturing processes employed.
Abstract
The PAN recordsdata for PVsyst combine most traits of PV modules which can be essential for power yield prediction beneath completely different weather conditions. These days, a major quantity of PAN recordsdata, that are broadly used within the trade comprise inaccurate data, which is overly optimistic of the particular PV module efficiency. With a view to purchase correct PAN recordsdata, there are some recommendations beneath.
Firstly, understanding the modelling technique and the way enter parameters are outlined is a elementary step. Secondly, the efficiency measurement of PV modules ought to be carried out in response to related requirements comparable to IEC 61215-1 [12] and IEC 61853-1,-23, [13]. Thirdly, it is suggested that checks are carried out by an accredited and respected laboratory.
Lastly, it’s instructed to have a third-party organisation performing common surveillance for PAN recordsdata data. A 3rd-party organisation can assist test the accuracy of PAN recordsdata, and if essential, pattern PV modules and carry efficiency characterisation to confirm the accuracy of enter parameters.
References
[1] N. Martin, and J.M. Ruiz., “Calculation of the PV modules angular losses beneath field situations by the use of an analytical mannequin”, Sol. Power Mater. Sol. Cells, 70 (1), 2001.
[2] M. Schweiger, W. Herrmann, A. Gerber and U. Rau, “Understanding the power yield of photovoltaic modules in several climates by linear efficiency loss evaluation of the module efficiency ratio”, IET Renew. Energy Gener., 11: 558-565.
[3] IEC 61853-2: 2016, Photovoltaic (PV) module efficiency testing and power ranking – Half 2: Spectral responsivity, incidence angle and module working temperature measurements.
[4] C. Monokroussos, Y. Zhang, Eleanor W. Lee and et al., “Power efficiency of economic c-Si PV modules in accordance with IEC 61853-1, -2 and affect on the annual particular yield”, EPJ of Picture., to be submitted.
[5] H. Hashigami, Y. Itakura, T. Saitoh, “Impact of illumination situations on Czochralski-grown silicon photo voltaic cell degradation”, J. Appl. Phys. 93, 7 (2003).
[6] J. Knobloch, S.W. Glunz et al., “Photo voltaic cells with efficiencies above 21% processed from Czochralski grown silicon” in Proceedings of twenty fifth IEEE Photovoltaic Specialists Convention, 1996, pp.405-408.
[7] R.L. Crabb, “Photon induced degradation of electron irradiated silicon photo voltaic cells”, in Proceedings of ninth IEEE Photovoltaic Specialists Convention, IEEE, Silver Springs, MD, USA, 1972, pp. 243-249.
[8] B. Sopori, P. Basnyat, S. Devayajanam, S. Shet, V. Mehta, J. Binns, “Understanding Mild-Induced Degradation of c-Si Photo voltaic Cells”, J. Appel in Proceedings of 2012 IEEE Photovoltaic Specialists Convention, Austin, 2012.
[9] T. Luka, C. Hagendorf, M. Turek., “Multicrystalline PERC photo voltaic cells: Is light-induced degradation difficult the effectivity acquire of rear passivation?”, Photovolt. Int. 32 (2016), pp. 37-44.
[10] Ok. Ramspeck, S. Zimmermann, H. Nagel, A. Metz, Y. Gassenbauer, B. Birkmann, “Mild Induced Degradation of Rear Passivated mc-Si Photo voltaic Cells”, A. Seidl., in Proceedings of twenty seventh European Photovoltaic Photo voltaic Power Convention and Exhibition. Frankfurt, 2012.
[11] E. Kobayashi et al., “Mild-induced efficiency enhance of silicon heterojunction photo voltaic cells”, Appl. Physics Letters, 109(15), 2016.
[12] IEC 61215-1: 2016, Terrestrial photovoltaic (PV) modules – Design qualification and sort approval – Half 1: Check necessities.
[13] IEC 61853-1: 2011, Photovoltaic (PV) module efficiency testing and power ranking – Half 1: Irradiance and temperature efficiency measurements and energy ranking.
Authors
Yating Zhang serves as challenge supervisor in R&D Photo voltaic & Business Merchandise of TÜV Rheinland Group. Yating is especially answerable for the event of measurement strategies of latest PV applied sciences and efficiency analysis of PV modules. She obtained her PhD diploma from Shanghai Institute of Microsystem and Data Know-how (SIMIT), Chinese language Academy of Sciences, Shanghai, China.
Christos Monokroussos serves as world head of photo voltaic and is answerable for the worldwide competence centre for photo voltaic and R&D within the TÜV Rheinland Group. Christos’s actions in TÜV Rheinland concentrate on the characterisation of photo voltaic cells and PV modules, PV module reliability and standardisation progress. Christos earned his doctorate diploma in photovoltaics on the Centre of Renewable Power Techniques Know-how (CREST), Loughborough College, UK.
