If you're evaluating which solar resource data set to use in solar project development, one question you should ask yourself is: has the climate changed at my location in the last decade? If it has, or you suspect it has, then you should be concerned with how recently a data set has been updated.
For example, the NASA data available globally in PVsyst has a 20+ year record but hasn't been updated since 2005. Meteonorm has 30+ years of data but ends in 2010. Climate changes at your location in the last decade will not be captured by these data sets. If you rely exclusively on them, you could find yourself in a predicament come operations. But how different can it be? Let's look at two examples.
First, in Los Angeles, California, stricter air pollution regulations in the last decade are working! Improved air quality and reduced aerosols in the atmosphere have a nice side effect of also increasing annual irradiance.
When we look at Mexico City we see the opposite. Decreasing air quality is also decreasing the annual irradiance values.
These two cases provide a “virtuous cycle” argument for using solar energy: reducing fossil fuel consumption will improve air quality and thereby, over time, actually increase the solar energy production in certain areas.
More importantly, they highlight why it is crucial to use a solar resource data set that is up-to-date, particularly if you are in any area where solar irradiance may have been affected by shifts in climate or other environmental factors like increased pollution. For example, relying on data sets that have not been recently updated would cause a developer near Mexico City to have overly optimistic expectations of project performance, and could hamper project financing for a developer near Los Angeles with performance estimates that are lower than they should be.
What if you didn't have to choose between keeping a tight schedule, accuracy of the resource data, and the cost to acquire it? With Vaisala's Solar Time Series Tools you can get access to highly accurate resource data within hours and for as low as $50 a time series for hourly data.
Click for more information and to view online purchase options.