Auxiliary Euro-Calliope datasets: Spatial data to represent a 98-node European energy system model

Subset of output generated with the possibility-for-electricity-autarky workflow which provides the same data as given by https://doi.org/10.5281/zenodo.3246302, but at a spatial resolution that does not strictly match administrative units in Europe. Three files are not generated with the possibility-for-electricity-autarky workflow: `nuts_to_regions.csv`, `transmission.csv`, and `units.png`. The source of these files is as follows: `nuts_to_regions.csv` defines the mapping of administrative spatial units in Europe to 98 spatial regions. These 98 regions are based on the result of work undertaken in the European Commission Seventh Framework Programme project e-HIGHWAY 2050 [1]. They cover 35 European countries, describing 19 at a national resolution and the rest on a subnational resolution. Subnational regions are aggregated from NUTS3-2006 administrative units. Those aggregated from NUTS3-2006 administrative units also have mappings from NUTS3 units in other NUTS years since region naming/borders can change by NUTS year (see here). `units.png` shows a map of the resulting 98 model regions. The region colours are used to help differentiate regions and have no other meaning. `transmission.csv` provides derived grid transfer capacities between the 98 model regions, according to the e-HIGHWAY 2050 project output as well as planned connections in the medium and long term, predominantly high voltage DC (HVDC), according to ENTSOE 2018 network development plan. [1] Anderski, T., Surmann, Y., Stemmer, S., Grisey, N., Momot, E., Leger, A.-C., Betraoui, B., and van Roy, P. (2014). European cluster model of the Pan-European transmission grid (e-HIGHWAY 2050)