SOLAR MODULE YIELD MEASUREMENT
OUTDOOR TEST RESULTS
Alongside with the release in our magazines, on this webpage we are featuring the results of our yield measurement test and the latest updates.
October issue 2014 – PHOTON International
Yield measurements for bifacial modules
Over the past several weeks and months, we have received some yield measurement requests from producers of bifacial modules. There is a clear reason behind this. With the way our yield measurements are calculated, bifacial module manufacturers can be certain that their modules will take the top positions in the rankings, especially since our benchmark for the yield measurement is based on the number of kilowatt-hours produced by the front side of the module under STC.
In the sellers’ view, this is fair, since when these modules are sold, the power indicated is only the power of the front side – the power of the back side is considered a bonus. Manufacturers often say that bifacial module users can count on an additional power of over 30 percent compared to a traditional module. However, there is no established way to describe the total power of a bifacial module. This is because the power of both sides, in fact, cannot just be added together. The amount of power generated by the back side depends on how the module is installed. For example, ...
➢ Read the full article in October 2014 issue of PHOTON International, p. 56.
August issue 2014 – PHOTON International
The first 6 months of measurement year 2014 have been analyzed, and the module type with the highest efficiency is the SR-190 monocrystalline module from Sopray Energy, which produced 660.5 kWh per kW (kWh/kW) during the period. In second and third places, respectively, are the SYP190S-M monocrystalline panel from Risen Energy, with 659.4 kWh per kW, and the SL190TU-36M monocrystalline module from Sonalis, with 659.2 kWh per kW. First and second places are occupied by the same module types that held those positions in full year 2013. The Sonalis module, which took fifth position in 2013, moved up two positions. In general, there were only slight ...
➢ Read the full article in August 2014 issue of PHOTON International, p. 44.
July issue 2014 – PHOTON International
An REC module has been replaced
The PHOTON yield measurement of solar modules is designed to help prospective buyers make good decisions when evaluating which solar module to use in a project – it is generally agreed that the price per watt alone is not sufficient for this. The amount of energy produced in terms of kilowatt-hours per watt can vary considerably even between different module types that have the same rated power.
The measurements developed by PHOTON engineers, however, are quite sophisticated, with the IV-curve of each module being saved every second. This results in 7 GB of data for each individual module each month, and for this reason, only up to three samples of a single module type are installed on our test field in Aachen, Germany ...
➢ Read the full article in July 2014 issue of PHOTON International, p. 42.
June issue 2014 – PHOTON International
Monocrystalline modules stand out – for a good reason
The yield measurements for the first 4 months of this year have come in, and the best solar modules on the PHOTON test field in Aachen, Germany produced up to 368 kWh per kW during the period. Considering that the sunniest months are still to come, this is a remarkable result. However, the extraordinarily sunny weather in the first part of 2014 must be taken into account. In order to assess the influence of the weather, ...
➢ Read the full article with all graphs in June 2014 issue of PHOTON International, p. 71.
May issue 2014 – PHOTON International
April issue 2014 – PHOTON International
A good year – Performance ratios vary from year to year
The PHOTON Lab therefore measures not only the yield of solar modules in endurance testing exercises conducted outdoors, but it also determines performance ratios using the data supplied by the test field weather station. This only applies to the round of measurements and observations taken in a given year, however. Since the weather changes slightly with each passing year, so too do the radiation conditions the modules are subjected to on the test field. In 2012, for example, snow accumulated on the modules during the winter months, whereas in 2013, the modules could operate with almost no snowfall to deal with. It therefore comes as no surprise that the average performance ratio of the module types that were assessed in both years was somewhat lower (-0.1 percent on average) in 2012 than in 2013.
When the figures are examined in greater detail, however, it becomes apparent that several modules defied the trend, performing better in 2012 than in 2013. This can best be explained in the context that every module type has a slightly different efficiency curve than the next one while operating across a wide range of radiation conditions. While some modules offer less than optimal performance when subjected to high levels of radiation, others are able to achieve far superior yields. Operating efficiency is also affected by the temperature of the solar cells and the spectral composition of the light itself. Finally, the angle at which the light reflects off the solar module plays an equally important role. As such, a few module types could provide a somewhat better overall return in 2012 than in 2013 despite having to run a few days under a cover of snow. For other modules, 2013 was the better year (see graph, PI 4/2014, p. 52).
➢ Read the full article with all graphs in April 2014 issue of PHOTON International, p. 50-53.
To download the complete PDF versions of our magazines, please go to: ➩ myPHOTON
March issue 2014 - PHOTON International
New installed on the test field
Jinko Solar's multicrystalline module JKM255PP-60 has entered the test in January 2014.
(Read the complete introduction with graphs and EL in PI 3/2014, p. 46.)
January's yield measurement results include 27 module types that have been active on our test field for some time but for which not enough data could be collected in 2013 to produce a complete yield measurement result. Nevertheless, modules such as Apollo Solar Energy's ASEC-235G6M, ITS Innotec's EcoPlus ITS220ECU5, JA Solar's JAP6-60-240/3BB, ReneSola's JC250S-24/Bb and Yingli's YL240P-29b are performing well and data for these modules will continue to be collected for the long-term outdoor performance test. From time to time, PHOTON needs to reconfigure or even remove module types from the test field, although our aim is of course to keep all modules in the performance test for as long as possible. Every module is guaranteed to stay on the test for at least one full calendar year. After a year on the field, each participant will receive an annual ranking and the according certificate.
The table depicting the results of our yield measurements in February issue erroneously contains the YL260C-30b (Panda) module type from Yingli Green Energy Holiding (see PI 2/2014, p 62-67). The Panda cells used in this module (like the back contacts cells from SunPower) have a much higher capacity than other crystalline solar cells. The time in which the regularly used module test device measures the IV curve is too short for this type of module because it can’t measure the entire IV curve. The measured yields are therefore too low and should not have been published. A modified measurement device is under development so that this module type can be included in future monthly yield results. Please find below the updated 2013 list with the annual results:
February issue 2014 - PHOTON International
Three Chinese modules lead the pack in PHOTON Lab’s yield test
This year’s top three winners in PHOTON Lab’s annual outdoor module yield test – Sopray Energy, Risen Energy and ET Solar Industry – can count themselves lucky. Had it not been for our newly-developed testing equipment for IV curves that was still going through its growing pains, this year’s results, as last year, would quite likely have given a gold, silver and bronze sweep for one US company – SunPower Corp. – instead of a one, two, three ranking for these Chinese manufacturers. But problems with the device meant that 26 modules from 23 companies were not measured correctly every month, which left them out of the annual running during the calendar year 2013.
So instead, the well-earned top spot goes to Sopray with a performance ratio of 94 percent and a yield of 1,094.3 kWh/kW for its SR-190 module, squeaking past Risen Energy with respective values of 94 and 1,092.5 for its SYP190S-M module, and ET Solar with 93.4 and 1,088 for its ET-M66250WW module. This was the first time that all three modules, each using monocrystalline cells, were tested for a full calendar year.
The top 10 (which included one more entry each from Sopray and Risen) ran a close race at our outdoor test field, the world’s largest, located in Aachen in the far west of Germany. The difference between the number one and number 10 was a mere 1 percentage point in the performance ratio and just under 9 kWh/ kW for yield.
While the performance ratio is the decisive criterion for the technical quality of a solar module, technology alone is not the measure of all things. Long-term stability is equally significant for a product that needs to function well for at least 20 years. Our tests are not designed to cover this, which arguably puts the older installed modules at a disadvantage in head-to-head competition. Indeed, the bottom three spots went to Photowatt International’s PW 1650-175W, installed in 2006, with an 80.6 percent performance ratio; Sharp Corp.’s NT-R5E3E, installed in 2005, with a 79.8 percent performance ratio; and Evergreen Solar’s ES-180-RL, installed in 2007, with a 76.6 performance ratio. Still, not all the older modules installed in the test field have shown their age. Siliken’s SLK60P6L 230Wp, installed in 2009, which in the 2011 yield survey was ranked number two (see PI/2012, p. 92), had only dropped to 15th place for this survey. It should be noted that not all of the modules in the test are still being manufactured.
As always, in the pursuit of consistency, the modules in the test field were not cleaned. Neither were they cleared of snow, which hardly mattered this year, as there were practically no snowfalls in Aachen during 2013.
Unlike this month’s Winter Olympics (where there is snow), the rankings for solar modules is more than a sport – indeed for winners, good results can be a serious selling metric. But nonetheless, as we start our measurements for next year’s annual module yield test – with equipment now set to measure each and every module entry with preciseness – it is time to let the games begin.
The PHOTON Yield Measurement outdoor module test 2013 annual results
include each months' data and are thus best viewed in a double-page mode like in the magazine:
Earlier annual test results of the PHOTON Yield Measurement:
To download the complete PDF versions of our magazines, please go to: ➩ myPHOTON
PHOTON Laboratory Yield Measurement test site near Aachen, Germany
PHOTON Laboratory’s outdoor module tests – methology & background
The overview tables document the current status of solar module yield measurements conducted by PHOTON Laboratory. Since 2005, the lab has been measuring solar module yields under real-world conditions. At least one module of each model is installed on an open field, facing south at a 28° incline. PHOTON Lab’s proprietary measurement devices take second-by-second measurements of the IV curve for each module. The test also captures other important values such as global irradiation, as well as module and air temperature.
For testing purposes, it’s important that modules actually feed in their electricity, as they would heat up in open-circuit mode. It’s also important to measure yield before it hits the inverter. One common mistake made in yield comparisons, apart from using generally imprecise measurements, is capturing data at the electricity meter – after the output has passed through the inverter. Inverter efficiency impacts yield measurements. Moreover, different combinations of modules and inverters result in better or worse performances, which makes it impossible to compare results. Another factor that poses challenges for module yield comparisons is standardization according to the manufacturer’s specified nominal power. These specifications can deviate considerably from actual power – power under standard test conditions (STC). That’s why PHOTON Lab’s yield tests always standardize to STC power.
The tables show yield measurements for all of the modules that have been installed on PHOTON Lab’s test field for at least a month. In the performance ratio column, results are shown for modules that were installed on the test field for a whole year. Only monthly values are stated for modules that were installed later. It is important to consider, however, that the results from a single month say relatively little about how the modules function over the course of a full year. For instance, modules that perform well under direct solar irradiation, delivering high yield in the summer months, have considerable reductions in performance during fall and winter – when the share of diffuse irradiation is higher. The opposite scenario is also possible. Naturally, the summer months play a disproportionately large role for annual yield calculations.
Winter can also impact results, albeit differently: modules on the test field are not cleaned during the year, and PHOTON Lab does not remove snow. Frameless modules therefore have an advantage, as snow tends to slide off these models faster. The age of the modules should also be taken into account when analyzing yield information: a module installed in 2005 cannot be compared directly with a module just recently installed on the test field.