Buildings.Experimental.DHC.Plants.Reservoir

Package of models for district-scale thermal reservoirs

Information

This package contains models for district scale thermal reservoirs.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
BoreField	Geothermal borefield model

Buildings.Experimental.DHC.Plants.Reservoir.BoreField

Geothermal borefield model

Buildings.Experimental.DHC.Plants.Reservoir.BoreField

Information

This model represents a borefield composed of 350 boreholes, with the following main assumptions.

The soil is made of sandstone.
The boreholes are filled with a bentonite grout.
The boreholes have a height of 300 m and a diameter of 190 mm. They are discretized vertically in five segments.
A distance of 10 m between each borehole is considered.
HDPE pipes with a diameter of 40 mm are considered, in a double U-tube parallel configuration.

Extends from Buildings.Fluid.Geothermal.Borefields.TwoUTubes (Borefield model containing double U-tube boreholes).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Integer	nCel	5	Number of cells per aggregation level
Integer	nSeg	5	Number of segments to use in vertical discretization of the boreholes
Integer	nBor	borFieDat.conDat.nBor	Number of boreholes
Real	dxyBor	10	Distance between boreholes
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_T	true	= true, if actual temperature at port is computed
g-function
Boolean	forceGFunCalc	false	Set to true to force the thermal response to be calculated at the start instead of checking whether this has been pre-computed
Integer	nSegGFun	12	Number of segments to use in the calculation of the g-function
Integer	nClu	5	Number of borehole clusters to use in the calculation of the g-function
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Conservation equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Boolean	dynFil	true	Set to false to remove the dynamics of the filling material.
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	TFlu_start[nSeg]	TGro_start	Start value of fluid temperature [K]
Soil
Temperature	TExt0_start	282.55	Initial far field temperature [K]
Temperature	TExt_start[nSeg]	{if z[i] >= z0 then TExt0_st...	Temperature of the undisturbed ground [K]
Filling material
Temperature	TGro_start[nSeg]	TExt_start	Start value of grout temperature [K]
Temperature profile
Height	z0	10	Depth below which the temperature gradient starts [m]
Real	dT_dz	0.02	Vertical temperature gradient of the undisturbed soil for h below z0 [K/m]

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
output RealOutput	TBorAve	Average borehole wall temperature in the borefield [K]
output RealOutput	Q_flow	Rate at which heat is extracted from soil [W]

Modelica definition

model BoreField "Geothermal borefield model" extends Buildings.Fluid.Geothermal.Borefields.TwoUTubes( final energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, final tLoaAgg(displayUnit="h") = 3600, final nSeg=5, TExt0_start=282.55, final z0=10, final dT_dz=0.02, final dynFil=true, borFieDat( filDat=Buildings.Fluid.Geothermal.Borefields.Data.Filling.Bentonite( kFil=2.0, cFil=3040, dFil=1450), soiDat=Buildings.Fluid.Geothermal.Borefields.Data.Soil.SandStone( kSoi=2.3, cSoi=1000, dSoi=2600), conDat=Buildings.Fluid.Geothermal.Borefields.Data.Configuration.Example( borCon=Buildings.Fluid.Geothermal.Borefields.Types.BoreholeConfiguration.DoubleUTubeParallel, dp_nominal=35000, hBor=300, rBor=0.095, nBor=350, cooBor=cooBor, dBor=1, rTub=0.02, kTub=0.5, eTub=0.0037, xC=0.05)), show_T=true); /* Some parameters (such as nBor) cannot be propagated down to borFieDat.conDat otherwise Dymola fails to expand. We assign them literally within borFieDat.conDat and propagate them up here to compute dependent parameters. */ parameter Integer nBor = borFieDat.conDat.nBor "Number of boreholes"; parameter Real dxyBor = 10 "Distance between boreholes"; final parameter Modelica.Units.SI.Length cooBor[nBor,2]={dxyBor*{mod(i - 1, 10),floor((i - 1)/10)} for i in 1:nBor} "Cartesian coordinates of the boreholes in meters"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput Q_flow(final unit="W") "Rate at which heat is extracted from soil"; equation connect(gaiQ_flow.y, Q_flow); end BoreField;