Time Series vs TMY

What is the difference between multi-year time series and TMY data?

The Full Time Series is the original data product generated by Solargis model, the one which contains the data values for the whole registered period. Since the information contained by a Time Series file is not compressed, it is the most versatile file able to provide inputs for all the calculations needed to run a complete solar resource assessment.

Solargis multi-year time series is most typically used for the following purposes:

To understand seasonal and inter-annual variability of solar resource
To understand occurrence of extreme irradiance and temperature events - for design optimization of solar power systems
Input data for energy simulation of solar power systems
For accuracy enhancement of long-term satellite-derived irradiance estimates - when high-quality irradiation measurements are available at project site

The Typical Meteorological Year (TMY) is a popular data product designed for summarizing the average weather conditions of a specific site in a period of a single year. TMY data is primarily used for energy simulation purposes, as popular simulation software such as PVsyst, SAM, etc. typically work with 8760 hourly values representing a typical year. The main reason for the popularity of TMY dataset for solar energy simulation is compatibility of such data with popular energy simulation software and speed of simulation.

The TMY is indeed constructed from Time Series (more info here), so it is usual to find both data files within the same order files in Solargis. However, since TMY data results in an avoidable loss of information, it is recommended to use a full time series file when possible.

To download sample Time Series or TMY you can click here.

Data description	Time Series	TMY
Period	Data from the full period available since 1994/1999/2007 (depending on the region)	Data from a summary year constructed by concatenation of data from typical months
Data values	Up to 876,000 approx.	8,760
Data time step	15-minute / Hourly	Hourly
Spatial resolution	250 meters	250 meters

Applications	Time Series	TMY
Running energy simulations	Yes	Yes
Calculation of absolute max / min values	Yes	No
Calculation of interannual variability	Yes	No
Comparison of data sources	Yes	No
Adjustment of values using ground data	Yes	No

Why are meteo data for selected months in TMY file different from meteo data for corresponding months in time series dataset?

When generating TMY data, we try to select months in such a way that annual sum of GHI/DNI values in the TMY file is consistent with the annual average calculated from time series. However, it may not be possible to find representative months where the sum of irradiation as well as meteo values will equal the long-term average. Therefore, we may be required to slightly adjust the meteo values to maintain similar averages as calculated from time series.

More information on how Solargis TMY data is prepared can be seen here.

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