The significance of measuring albedo at photo voltaic websites

As bifacial modules proliferate, estimations of albedo have gotten extra essential and with builders not ready to put in climate stations to evaluate photo voltaic useful resource, a preferred possibility has develop into third-party, on-site measurements over intervals as brief as a day. Is that this an appropriate compromise between expensive on-site measuring and fewer correct satellite tv for pc information? Everoze’s Stefan Mau discusses the potential advantages and limitations of this strategy.

July 3, 2024 pv magazine

From pv magazine 6/24

Though an correct evaluation of photo voltaic assets is essential to making sure the reliability of an power yield evaluation, most research rely completely on satellite tv for pc irradiation information. Photo voltaic builders not often dedicate assets to putting in a climate station to acquire ground-measured information earlier than PV challenge development, primarily due to the numerous prices concerned. Working a climate station for a 12 months prices between €40,000 ($43,000) and €60,000. A satellite tv for pc dataset prices a number of hundred euros.

The event of bifacial modules has difficult the evaluation of obtainable photo voltaic assets. Irradiation arriving on the rear facet of bifacial modules is principally decided by albedo, which is the ratio between downward irradiation reaching the bottom and the upwelling irradiation mirrored by it. As with different information, reminiscent of world or diffuse irradiation, albedo will be obtained from satellite tv for pc imagery. Main information suppliers additionally supply this info. Albedo is tougher to evaluate than downward irradiation, as it’s influenced primarily by the character of soil. Satellite tv for pc information decision is, at greatest, round 1 km² and the character of soil, and therefore albedo, can considerably range over such a comparatively small space. Albedo will even range throughout a day, relying on elements such because the place of the solar, the season, and the climate. A barely misguided albedo worth can simply trigger a 0.5% affect in a yield evaluation that would have an effect on challenge valuations by vital quantities of cash.

These elements lead us to the conclusion that albedo needs to be measured. However, the price of a one-year marketing campaign continues to be a “no-go” for many builders. Alternatively, some service suppliers suggest short-term measurement campaigns the place the albedo is measured on website for one or a number of days. This measurement is then used to calibrate satellite tv for pc albedo information.

Quick-term advantages

Since Everoze is usually requested to make use of information corrected with short-term albedo measurements, we wished to forge our personal opinion on the advantages of such short-term measurements. We used publicly accessible, quality-checked climate station measurements, together with world irradiation and albedo figures, and analyzed the impact of calibrating this information with short-term albedo measurements from one-day and seven-day campaigns.

We used information from the Floor Radiation Finances Community (SURFRAD) from seven websites in america. Excessive-resolution information have been extracted for six years, from 2017 to 2022, and used to calculate a month-to-month reference albedo for every of these websites, averaged over the six years. For example, the reference albedo for January was the typical of all January albedo values from 2017 to 2022. We additionally downloaded satellite tv for pc albedo information from the Prospect software of photo voltaic irradiance information firm SolarGIS for the seven areas.

Everoze utilized a number of high quality checks to the SURFRAD information, which led to the elimination of a negligible variety of days over the six-year interval. We then used the albedo of each single day as one-day campaigns and rolling seven-day intervals as weekly campaigns, correcting all of the satellite tv for pc information based mostly on these campaigns. Lastly, with photo voltaic design software PVsyst, we simulated a theoretical single-axis monitoring, bifacial PV asset and ran yield eventualities that includes the six-year common SURFRAD albedo, uncooked satellite tv for pc albedo, and satellite tv for pc albedo.

We in contrast the yields. The measurement marketing campaign was thought of helpful if the distinction between SURFRAD information and the corrected albedo was decrease than the distinction between SURFRAD and the uncooked satellite tv for pc albedo. The determine under illustrates the outcomes for one-day and seven-day campaigns for every of the seven challenge websites.

Worth for cash

The outcomes confirmed one-day campaigns needs to be discarded as a result of they don’t seem to be helpful typically, specifically in the course of the winter. Seven-day campaigns are largely helpful within the summertime. The creator famous that information from different areas could result in completely different conclusions. Different elements reminiscent of location, peak, calibration, and the cleansing frequency of the albedometer needs to be thought of with care. Everoze recommends making the funding to cowl a full 12 months of measurements, slightly than only some days. It might be expensive within the brief time period however value it over a challenge lifetime.

In regards to the creator: Stefan Mau is {an electrical} engineer and has been working in photo voltaic since 1999, together with in R&D, testing and certification, measurement, and consultancy companies in Spain, Germany, and Austria. Earlier than becoming a member of Everoze, he was world contact for operational companies in PV crops at DNV GL. At Everoze, he helps business PV companies reminiscent of due diligence, bankability, and power assessments and coaching. He’s a part of the Spanish standardization committee for PV modules and holds one patent.

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