Simulation variables: Stand alone system
The following variables are calculated during the simulation process, and available as results:
Weather data and irradiation variables: see previous page.
PV array behaviour
EArrMPP | Array virtual energy at MPP (after wiring, module quality and mismatch losses), Virtual calculation independent of the system running and voltage operation | |
| EArUfix | Array virtual energy at fixed voltage Voltage as calculated by the balance loop (real battery voltage), or Battery reference voltage when PV-array disconnected. | |
| EUnused | Unused energy (full battery) loss | (EArUFix when Charging OFF) |
| MPPLoss | Loss with respect to the MPP operation | (when charging ON) |
| Earray | Effective energy at the output of the array | (when charging ON) |
| IArray | Array Current | (accumulated in Ah) |
| UArray | Array Voltage | (average when Charging ON) |
| ArrayON | State / Duration of the PV production of the array |
If converter present: converter losses
| CL_Oper | Converter loss during operation (efficiency curve) |
| CL_Pmin | Converter Loss due to power threshold' |
| CL_Pmax | Converter Loss due to power overcharging |
| CL_Vmin | Converter Loss due to low voltage MPP window |
| CL_Vmax | Converter Loss due to upper voltage MPP window |
| CnvLoss | Global converter losses |
| OutConv | Energy at converter output |
Battery operation: storage, losses and ageing
EBatCh | Battery Charging Energy |
| U Batt | Average battery voltage, any conditions, |
| UBatCh | Battery Voltage during charging operation |
| IBatCh | Battery Charging Current (all currents accumulated [Ah]) |
| ChargON | Charging duration |
| EBatDis | Battery Discharging Energy |
| UbatDis | Battery Voltage during discharge operation |
| IBatDis | Battery Discharging Current (all currents accumulated [Ah]) |
| DischON | Discharging duration |
| ESOCBal | Stored energy balance (according to SOCEnd - SOCBeg) |
| SOCmean | Average State of Charge during the period |
| SOC Beg | State of Charge at beginning of time interval' |
| SOC End | State of Charge at end of time interval' NB: The SOC evolution calculation is referred to the actual capacity of the battery, which varies with the discharge current and the temperature. Therefore it is not quite well determined, and not reversible (it may be different when charging and discharging). |
| EBatLss | Battery global energy loss (EBatCh - EBatDis - ESOCBal) |
| IBEffL | Battery charge/discharge current loss (coulombic efficiency [Ah]) |
| IBGass | Gassing Current loss (electrolyte dissociation [Ah]) |
| IBSelf | Battery Self-discharge Current (depends on temperature [Ah]) |
| EBattEff | Battery energy efficiency (IBEffL * U Batt) |
| EBGass | Gassing Current energy loss (IBGass * U Batt) |
| EBSelf | Battery Self-discharge Energy (IBSelf * U Batt) NB: The sum of the detailed battery losses contributions appearing on the loss diagram should in principle match this Battery Global Energy Loss calculated above, i.e: EBattLss = EBattEff + EBSelf + EBGass But during the simulation, all these contributions are determined from the Currents balance of the system (PV array - Battery - Load), multiplied by the Battery Voltage, which is varying with currents, charge/discharge state, state of charge, temperature, etc. Moreover, the stored energy ESOCBal is based on the capacity, which is varying according the conditions (current and temperature). The resulting energies are therefore defined with some uncertainties. Therefore the overall energy balance on the battery cannot be quite rigorous. |
| WeCycle | Wearing due to cycling |
| WeState | Wearing state (cycling and age) |
| MGass | Dissociated Electrolyte Mass per cell |
System operating conditions
| E_BkUp | Back-up Generator Energy | (UBatt * I BkUp) |
| I_BkUp | Back-up Generator Current' | (accumulated in Ah) |
| BkUp_ON | Back-up Generator running duration | |
| FuelBU | Fuel consumption of Back-up Generator | |
| Energy use | ||
| E_Avail | Available Solar Energy | Energy at the output of the array when producing - converter loss + Unused energy E Avail = E Array - CnvLoss + E Unused |
| E_Load | Energy need of the user (Load) | Defined as Input data |
| E_User | Energy supplied to the user | Including back-up energy |
| SolFrac | Solar fraction | (EUser - EBkUp) / ELoad |
When no back-up generator defined
| E_Miss | Missing energy | Eload - Euser |
| SolFrac | Solar fraction | EUser / ELoad |
| T_LOL | Duration of "Loss of Load" | Duration user not supplied |
| Pr_LOL | Probability of "Loss of Load" | Idem as percentage of time |
Efficiencies
| EffArrR | Array Efficiency | EArray / rough area |
| EffArrC | Array Efficiency | EArray / cells area (=0 when cells area not defined) |
| EffSysR | System efficiency | E User / rough area |
| EffSysC | System efficiency | E User / cells area (=0 when cells area not defined) |
| EffBatI | Battery current charge/discharge efficiency | |
| EffBatE | Battery energy charge/discharge efficiency |
Normalised performance index
(Read more about Normalised performance index)
| Yr | Reference Incident Energy in collector plane | = GlobInc [kWh/m²/day] |
| Yu | Normalized Potential PV Production (battery never full) | [kWh/kWp/day] |
| Ya | Normalized Array Production | = EArray [kWh/kWp/day] |
| Yf | Normalized System Production | = EAvail [kWh/kWp/day] |
| PR | Performance ratio | = Yf / Yr. |
| Lu | Normalized Unused energy | = Yr - Yu |
| Lc | Normalized Array Losses | = Yu - Ya |
| Ls | Normalized System Losses | = Ya - Yf |
| Lur | Unused (full battery) Loss / Inc. Energy Ratio | = Lu / Yr |
| Lcr | Array Loss / Incident Energy Ratio | = Lc / Yr |
| Lsr | System Loss / Incident Energy Ratio | = Ls / Yr |