AtesCluster

Description

The AtesCluster asset represents an Aquifer Thermal Energy Storage (ATES) system in the thermal network. It can operate in charging mode (injecting heat into the aquifer) and discharging mode (extracting heat from the aquifer). In the network equations, the asset behaves as a controllable thermal boundary with a prescribed mass flow and supply temperature.

The subsurface thermal response is represented through ROSIM, an external aquifer model developed by TNO, and the resulting hot-well and cold-well temperatures are used to update the ATES operating point between timesteps. The asset is mapped from ESDL ATES properties and receives controller-provided setpoints during simulation.

Parameters

Parameter

Description

Unit

ESDL Asset Property

aquifer_depth

Depth of the top of the aquifer

m

aquiferTopDepth

aquifer_thickness

Aquifer thickness

m

aquiferThickness

aquifer_mid_temperature

Undisturbed aquifer mid temperature

degC

aquiferMidTemperature

aquifer_net_to_gross

Net-to-gross ratio used in aquifer parameterization

aquiferNetToGross

aquifer_porosity

Effective porosity

aquiferPorosity

aquifer_permeability

Horizontal permeability

mD

aquiferPermeability

aquifer_anisotropy

Permeability anisotropy factor

aquiferAnisotropy

salinity

Groundwater salinity

ppm

salinity

well_casing_size

Well casing diameter parameter

inch

wellCasingSize

well_distance

Distance between hot and cold wells

m

wellDistance

temperature_in

Initial inlet temperature used to start operation

K

controller-set (runtime)

temperature_out

Initial outlet temperature used to start operation

K

controller-set (runtime)

Controlled Parameters

The controller provides a setpoint dictionary with the following user-relevant signals:

Signal

Description

Unit

\(Q_{demand}\)

Requested heat demand. The ATES thermal allocation uses opposite sign internally.

W

\(T_{in,set}\)

Inlet temperature setpoint used at the first timestep.

K

\(T_{out,set}\)

Outlet temperature setpoint used at the first timestep.

K

From the second timestep onward, the inlet or outlet temperature is partly taken from the solved network state and partly from aquifer well temperatures, depending on charging or discharging mode.

Additional simulation outputs

The ATES asset writes the following result signals for each timestep:

Signal

Description

Unit

mass_flow

Solved mass flow through the ATES boundary

kg/s

pressure_supply

Pressure at ATES connection point 0

Pa

pressure_return

Pressure at ATES connection point 1

Pa

temperature_in

Solved inlet temperature at connection point 0

K

temperature_out

Solved outlet temperature at connection point 1

K

Physics and Assumptions

The AtesCluster couples network-side heat exchange to subsurface thermal storage behavior. The controller requests thermal exchange, the model computes the required mass flow from the network temperature lift, and the aquifer model updates hot- and cold-well temperatures used in subsequent timesteps.

Operating mode and sign convention

The internal thermal allocation is defined as:

\[Q_{alloc} = -Q_{demand}\]

with:

\[Q_{alloc} > 0 \Rightarrow \text{injection (charging aquifer)}\]
\[Q_{alloc} < 0 \Rightarrow \text{production (discharging aquifer)}\]

Mass flow

The required mass flow follows the standard thermal power balance:

\[\dot{m} = \frac{Q_{alloc}}{c_p (T_{out} - T_{in})}\]

where \(c_p\) is fluid specific heat capacity and \(T_{in}, T_{out}\) are the active ATES boundary temperatures for the current mode.

Temperature coupling with wells

The ATES boundary supply temperature depends on flow direction:

\[\dot{m} \ge 0 \Rightarrow T_{supply} = T_{cold,well}\]
\[\dot{m} < 0 \Rightarrow T_{supply} = T_{hot,well}\]

After each timestep, the aquifer model updates \(T_{hot,well}\) and \(T_{cold,well}\) from the exchanged flow and thermal conditions. This captures long-term thermal storage and recovery effects in simplified form.

Aquifer flow conversion

Before calling the aquifer model, mass flow is converted to volumetric flow using a fixed saline density:

\[\dot{V} = \frac{\dot{m}}{\rho}\]

with \(\rho \approx 1027\ \text{kg/m3}\) in the current model.

Assumptions

  • The aquifer response is represented by ROSIM, configured from ESDL aquifer and well properties.

  • Network-side ATES behavior is quasi-steady per timestep.

  • Fixed fluid density is used for mass-to-volume conversion in aquifer calculations.

  • First timestep temperatures are taken directly from controller setpoints.

Limitations

  • The model does not resolve detailed 3D groundwater hydraulics in the network solver itself.

  • Density and thermophysical-property variation in the aquifer flow conversion are simplified.

  • Wellbore thermal losses and mechanical constraints are not modeled explicitly.

  • Accuracy depends on the validity and calibration of the configured external aquifer model.

See Also

References

References