Defining the exploitation patterns of groundwater heat pump systems

Area of Science:

• Environmental Science
• Geothermal Energy Engineering
• Urban Planning

Background:

• Shallow geothermal energy (SGE) systems offer efficient, clean building climate control and are a growing renewable resource.
• Unmanaged groundwater extraction for SGE in urban areas can lead to thermal interferences, jeopardizing resource sustainability and system performance.
• Biased energy demand, particularly a cooling bias, disrupts the natural thermal balance of aquifers.

Purpose of the Study:

• To analyze the exploitation regimes of 27 groundwater heat pump systems in an alluvial aquifer.
• To identify thermal interferences and define characteristic exploitation patterns.
• To provide a framework for resource managers to identify and correct unbalanced SGE system operations.

Main Methods:

• Descriptive statistics to examine exploitation regimes.
• Pearson's r correlation to assess linear relationships between abstraction and injection temperatures, indicating thermal interference.
• Spectral analysis and sinusoidal regression for time series modeling of flow rate, temperature, and energy transfer.

Main Results:

• Exploitation regimes exhibited a distinct cooling bias and cyclical patterns.
• Cycle amplitudes correlated with end-user activities (high frequency) and climate control strategies (low frequency).
• Defined relative operational patterns for individual systems and groups of systems.

Conclusions:

• Biased exploitation of SGE in Mediterranean urban areas necessitates corrective actions for sustainable resource management.
• The proposed characteristic exploitation pattern can guide resource managers in identifying unbalanced systems.
• Understanding exploitation patterns facilitates the proposal of corrective plans to ensure balanced SGE resource utilization.