A time series is a sequence of data, modeled or measured, representing regular intervals over a period of time (several years in case of a multi-year time series). SolarGIS multi-year time series is most typically used for following purposes:
1) To understand seasonal and inter-annual variability of solar resource
2) To understand occurrence of extreme irradiance and temperature events - for design optimisation of solar power systems
3) Input data for energy simulation of solar power systems
4) For accuracy enhancement of long-term satellite derived irradiance estimates - when high-quality irradiation measurements are available at project site
A sample multi-year time series data file can be downloaded from here: http://solargis.info/doc/_files/sample_data/SolarGIS-climData/SolarGIS-hourly-time-series-PSA-ES.zip
A Typical Meteorological Year (TMY) dataset is derived from a multi-year time series.
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 popularity of TMY dataset for solar energy simulation is compatibility of such data with popular energy simulation software and speed of simulation.
However as preparation of TMY data results in loss of information, it is recommended to use a multi-year time series for energy simulation purposes when possible.
A sample TMY data file can be downloaded from here: http://solargis.info/doc/_files/sample_data/SolarGIS-climData/SolarGIS-TMY-hourly-P50-PSA-ES.zip