  This paper proposes an approach to optimize the technical potential of
thermal groundwater use by determining the optimal sizing and placement of
extraction-injection well doublets. The approach quantifies the maximum
technically achievable volume of extracted groundwater in a given area and,
hence, the amount of heat exchanged with the aquifer, considering relevant
regulatory and hydraulic constraints. The hydraulic constraints ensure
acceptable drawdown and rise of groundwater in extraction and injection wells
for sustainable use, respectively, prevention of internal hydraulic
breakthroughs, and adequate spacing between neighboring doublets. Analytical
expressions representing these constraints are integrated into a mixed-integer
linear optimization framework allowing effcient application to relatively large
areas. The applicability of the approach is demonstrated by a real case study
in Munich, where the geothermal potential of each city block is optimized
independently. Six optimization scenarios, differing in terms of required
minimum installed doublet capacity and spacings between doublets, underline the
adaptability of the approach. The approach provides a comprehensive and
optimized potential assessment and can be readily applied to other geographic
locations. This makes it a valuable tool for thermal groundwater management and
spatial energy planning, such as the planning of fourth and fifth generation
district heating systems.
