PTES land eligibility

[cpschau]

This PR adds a rudimentary land eligibility for pit thermal energy storage (PTES), that is used to introduce an upper bound for the maximum installable storage capacity within Germany. These upper bounds are introduced the district heating subnodes as well as for the mother nodes that comprise all currently existing district heating systems that are not explicitly represented by subnodes.

The land eligibility is based on the following assumptions (all criteria must be met):

• PTES can only be built within the district heating systems that are contained within the Fernwärmeatlas
• PTES can be located within the boundaries of the lower administrative units of the cities that are associated with these district heating systems
• PTES can be built in areas of the following Corine land cover categories (configurable parameter): "Natural grasslands", "Sclerophyllous vegetation", "Beaches - dunes - sands", "Sparsely vegetated areas", and "Burnt areas"
• PTES cannot be built within areas, which are protected according to NATURA 2000 dataset
• PTES cannot be built in areas with a groundwater depth above -19 m underground. A geografically continuous global dataset of the groundwater depth is provided by Fan et al.. There should be a minimum distance between the storage ground and the groundwater of 3m.

The maximum installable capacity is calculated as conservative estimate, based on the geometric and techno-economic data of the existing PTES projects in Denmark: The geometric properties (surface area & depth) correspond to two of the largest projects in Denmark, namely SUNSTORE 2 & 3 (source for surface, source for depth). The energetic capacity of 4.5 GWh was taken from the PTES unit described in the DEA catalogue.