The following variables are calculated during
the
simulation process of the pumping system, and are
available as results.
The
Irradiance and PV-Array variable topic describes all the
preceding simulation variables, which lead to the last quantity
really independent of the system running conditions, the
Array virtual energy at
MPP.
The set of variables involved in the pumping
system simulation, as well as their significance and order, is
dependent on the System
Configuration. The energies (in blue) at different
levels of the system are visualized on the Loss diagram.
Direct coupling
configuration
With
Direct coupling configurations, including improved
solutions with booster, pump cascading or Array reconfiguration,
the set of main variables is defined as:
| EArrMpp
|
Virtual available energy at the
maximum power point. |
| MPPLoss
|
Loss with respect to the MPP
running (EArrMpp - EArray) |
| EArray
|
Effective energy at the output of
the array, according to the real Voltage operating point. |
|
|
This contribution is also
accounted for when the pump is stopped due to full tank conditions,
assuming normal voltage of the pump, as if it were running. |
| IArray
|
Corresponding current,
instantaneous [A] or cumulated [Ah]. |
| UArray
|
Corresponding voltage,
instantaneous or averaged [V]. |
|
|
Cascading or array
reconfiguration configurations: |
| 1_PmpON
|
Operation duration with one pump
/ low voltage array |
| 2_PmpON
|
Operation duration with two pumps
/ high voltage |
| A_PmpON
|
Operation duration with all
pumps |
| EPStart
|
Energy loss under the starting
current threshold (EArray when pump not
started) |
|
|
(only for positive displacement pumps,
without booster). |
| EPmpThr
|
Energy loss under pump producing
threshold (EArray when FlowR = 0) |
|
|
(for centrifugal pumps, which should
attain a given speed before reaching the useful head). |
| EPmpOvr
|
Pump overload energy
(EArray in excess of the pump's maximum
power) |
| EPmpAv
|
Available useful energy at pump when
running (EArray - EPStart - EPmpThr -
EPmpOvr) |
|
|
(before taking the Pump stopping due to
hydraulic constraints into account). |
MPPT converter
configuration
| EArray
|
Effective energy at the output of
the array (normally = EArrMpp) |
| IArray
|
Corresponding current at MPP,
instantaneous [A] or cumulated [Ah]. |
| UArray
|
Corresponding voltage at MPP,
instantaneous or averaged [V]. |
| CL_Oper
|
Converter efficiency loss during
operation. |
| CL_PMax
|
Converter overload loss
(acc. to the specified strategy, limitation or cut). |
| EOutConv
|
Energy at the output of the
converter |
| EPmpThr
|
Energy loss under pump producing
threshold (EOutConv when FlowR =
0). |
| EPmpAv
|
Available useful energy at pump when
running (EOutConv - EPmpThr). |
| NB:
|
The converter Voltage or Power
threshold losses are included in EPmpThr. |
Fixed Voltage DC converter
configuration
| EArrMpp
|
Virtual available energy at the
maximum power point. |
| MPPLoss
|
Loss with respect to the MPP
running (EArrMpp - EArray) |
| EArray
|
Effective energy at the output of
the array, at the fixed converter voltage. |
| IArray
|
Corresponding current, |
| CL_Oper
|
Converter efficiency loss during
operation. |
| CL_PMax
|
Converter overload loss
(acc. to the specified strategy, limitation or cut). |
| EOutConv
|
Energy at the output of the
converter |
| EPmpThr
|
Energy loss under pump producing
threshold (EOutConv when FlowR =
0). |
| EPmpAv
|
Available useful energy at pump when
running (EOutConv - EPmpThr). |
For all of the above
configurations: hydraulic constraints
These manage
the Hydraulic commands of the pump. When the pump is OFF the losses
listed above remain, and the lost energy
is part of the EPmpAvail.
| ELowLev
|
Pump stopped due to low level
aspiration (deep well, drawdown safety) |
| ETkFull
|
Pump stopped when tank is
full |
| EPmpOp
|
Pump real operating energy
(EPmpAvail - ELowLev - ETkFull). |
Battery Buffer
Configuration
The
Battery-buffered configuration has a quite different
operating mode, as the pump is connected to the battery voltage,
which is quasi-constant and independent of the PV-array production.
The PV-battery-load simulation process is similar to the
Stand-alone strategy, with the pump as load.
With this
configuration we have chosen to account for the "hydraulic" losses due to "Low level"
(drawdown limit) and "Tank Full" upstream the
battery operating losses, as we consider them as
electrical losses, between the "Available PV energy" (at fixed
nominal voltage) and the "Unused energy" when the battery is full.
Indeed, there
is no loss when the pump is stopped but the battery is not full:
the available PV energy is simply stored into the battery.
The necessary variables involved in the
simulation are the following:
| EArrMpp
|
Virtual available energy at the
maximum power point. |
| MPPLoss
|
Loss with respect to the MPP
running (EArrMpp - EArray at Vnom) |
| ELowLev
|
Energy lost when Pump stopped due
to low level aspiration (deep well, drawdown safety) |
| ETkFull
|
Energy lost when Pump stopped due
to tank is full |
|
|
These two above losses are
accounted only when the battery charging is OFF due to full
battery. |
| EArray
|
Effective energy at the output of
the array (at operating voltage) |
|
|
Accounted only when the charging
condition is ON |
| IArray
|
Corresponding charging current,
instantaneous [A] or cumulated [Ah]. |
| UArray
|
Corresponding charging voltage,
instantaneous or averaged [V]. |
| SOC_Beg
|
State of Charge, beginning of
interval |
| SOC_End
|
State of Charge, end of
interval |
| UBatt
|
Average battery voltage |
| IBatCh
|
Battery charging current
[A or Ah] |
| IBatDis
|
Battery discharging current
[A or Ah] |
| IBEffL
|
Battery Charge/Discharge current
efficiency loss |
| IBGass
|
Gassing current
(electrolyte dissociation when full) |
| IBSelf
|
Battery self-discharge
current |
| EBatCh
|
Battery charging energy |
| EBatDis
|
Battery discharging energy |
| ESOCBal
|
Stored energy, Balance
between SOCEnd and SOCBeg |
| EBatLss
|
Battery Overall energy loss
(EBatCh - EBatDis - ESOCBal) |
| EEffLss
|
Battery efficiency loss
(EBatLss - (IBGass+IBSelf) * UBatt |
| EPmpOp
|
Pump operating energy
|
| NB:
|
The balances of the battery
energies can never be rigorous due to the very complex behaviour of
the battery. For example its effective capacity, which strongly
varies with the discharge current, the temperature, etc. If
the current balances are well determined in the simulation process,
the corresponding energies involve the operating voltage, which is
also model-dependent and varies with state of charge, charge and
discharge currents, etc. |
Hydraulic part, for all
configurations
Remember
that the
Hydraulic Energy is the product of the Head and Volume
pumped.
The last part
of the Energy Loss diagram refers to Hydraulic energy. Implicitly, when it
shows pumped water volumes, this is under a given Head.
Inversely, the arrows for Dynamic Head Losses express a Head
loss at constant volume.
| E_Hydro
|
Pump hydraulic energy (energy to
the fluid) |
| P_Effic
|
Global pump efficiency
(E_Hydro / E_PmpOp) |
| H_Pump
|
Average total Head at pump
(During Pump_ON) |
| H_Stat
|
Static head requirement |
| H_Loss
|
Friction head loss |
| H_DrawD
|
Well: drawdown head loss
(Only deep well systems) |
| FlRate
|
Average flowRate when
running |
| WPumped
|
Water pumped volume
[m³] |
| WStored
|
Stored water in the tank |
| W_Used
|
Water drawn by the user |
| W_Miss
|
Missing water, with respect to
the user's needs. |
A lot of
further (secondary) variables are available for results, which are
not described here.
