  The optimization of open-loop shallow geothermal systems, which includes both
design and operational aspects, is an important research area aimed at
improving their efficiency and sustainability and the effective management of
groundwater as a shallow geothermal resource. This paper investigates various
approaches to address optimization problems arising from these research and
implementation questions about GWHP systems. The identified optimization
approaches are thoroughly analyzed based on criteria such as computational cost
and applicability. Moreover, a novel classification scheme is introduced that
categorizes the approaches according to the types of groundwater simulation
model and the optimization algorithm used. Simulation models are divided into
two types: numerical and simplified (analytical or data-driven) models, while
optimization algorithms are divided into gradient-based and derivative-free
algorithms. Finally, a comprehensive review of existing approaches in the
literature is provided, highlighting their strengths and limitations and
offering recommendations for both the use of existing approaches and the
development of new, improved ones in this field.
