How much solar power does a photovoltaic solar power unit produce? The answer isn’t obvious. The strength of sunshine changes depending where you are in the world and what time of day it is, affecting the energy output of solar panels and cells. But researchers need a common reference and that’s why they meet to adjust their instruments each year – this year it was at the 7th International Broadband Intercomparison event in Catania, Sicily.
The process is similar to the scientific quest more than 200 years ago to standardise measurements such as the metre, as was done in Paris at the International Bureau of Weights and Measures where a physical example of a metre is still kept from the eighteenth century.
“It’s actually ‘measuring the metre’. We can’t measure the metre like in Paris, but we use the sun as a metre. So everybody is comparing to the same sun, or the same metre,” Wim Zaaiman said at event in Catania.
These simultaneous measurements allow scientists to produce what they refer to as “reference cells”. These are small, high-quality solar cells with exactly defined characteristics. The overall intensity of the sunlight is taken into account, along with sunlight’s spectral composition, which varies greatly throughout the day and around the world.
These references are vital for the growing photovoltaic industry. In this multi-billion euro market, tiny imprecisions in measurements can decide a company’s success or failure.
Roberto Galleano, a meteorologist at the European Commission’s Joint Research Centre (JRC) – its in-house service – which is based in Ispra in Italy’s Lombardy region explained the necessity for meeting up annually: