Simulation variables Simulation variables: Grid system The following variables are calculated during the simulation process , and available as results:
Weather data and irradiation variables : see previous page.
PV array behavior PNomArray Nominal Installed Power ( = Nb. PV modules * nameplate PNom) EArrRef Array reference energy for PR calculation (as defined in the IEC EN 61724 norm) = GlobInc * PNomArray EArrNom Array nominal energy at STC, according to the one-diode model. Starting point of the array energy evaluation in the loss diagram = GlobEff * Pmpp (STC) GIncLoss PV loss due to irradiance level (low-light efficiency) TempLoss PV loss due to temperature (see Uc and UV parameters) SpctCor Spectral correction (amorphous modules, CdTe, Sandia model) LigSoak Light soaking for CIS/CIGS modules ShdElec Electrical loss for mismatch due to shadings (calculation "according to module strings" or "ModuleLayout") ModQual Module quality loss (users choice concerning real performance of the modules) LIDLoss Light Induced degradation (for mono-crystalline modules, p-type wafer only) MisLoss Module array mismatch loss OhmLoss Ohmic wiring loss in the DC array EArrMPP Array MPP energy after all array losses (on the loss diagram) EArray Effective energy at the array output (taking inverter operating point displacements into account - not represented on the Loss diagram) Iarray Array current (taking inverter operating point displacements into account) Uarray Array voltage (taking inverter operating point displacements into account)
Inverter behavior (see also Inverter operating limits )
InvLoss Global inverter loss IL_Oper Inverter Loss during operation (efficiency curve) IL_Pmin Inverter Loss due to power threshold IL_Pmax Inverter Loss due to power overload IL_Vmin Inverter Loss due to low voltage MPP window IL_Vmax Inverter Loss due to upper voltage MPP window IL_Night Inverter night energy (usually negligible or null) Syst_ON System operating duration EOutInv Available Energy at Inverter Output may be larger than EArray if grid limitation is accounted as separate loss
Energy output and use Aux_Lss Auxiliaries consumption (Fans, other... ) EacOhmL AC ohmic loss (wiring up to injection point) ETrfLss External transfo loss (iron loss and ohmic contribution) UnavLss System Unavailability loss Specified or random periods of shutdown E_Solar Energy supplied to the user from solar if load is defined (Netmetering) E_User Energy need of the user if load is defined (Netmetering) E_Avail Energy available from the sun = EOutInv - losses after inverter (Wiring, night losses) E_Grid Energy injected into the grid EApGrid Apparent energy into the grid when Power factor defined ERegrid Reactive energy into grid when Power factor defined EGrdLim Grid limitation loss when Grid limitation is accounted as separate loss SolFrac Solar fraction ESolar / EUser
Efficiencies EffArrR Array Efficiency EArray / rough area EffArrC Array Efficiency EArray / cells area (=0 when cells area not defined) EffSyR System efficiency EOutInv / rough area EffSyC System efficiency EOutInv / cells area. EffInvB Inverter efficiency Threshold loss included EffInvR Inverter efficiency When operating
Normalised performance index (cf IEC EN 61724, usually expressed and plotted as values per day)
Yr or Reference Incident Energy in collector plane = GlobInc [kWh/m²] (kWh irradiance) Yr Normalized Reference nominal energy at STC = EArrRef / PNomArray [kWh/kWp] (kWh electrical) Ya Normalized Array Production = EArray / PNomArray [kWh/kWp] Yf Normalized System Production = EGrid or EAvail / PNomArray [kWh/kWp] Lc Normalized Array Losses = Yr - Ya Ls Normalized System Losses = Ya - Yf PR Performance Ratio = Yf / Yr = E_Grid / (GlobInc * PNomArray)
NB : The Normalized Reference nominal energy at STC Yr [kWhel/kWp] is the electrical energy which would be produced by the Reference incident energy on the collector plane under STC conditions (1 kWirrad/m2, 25°C). This explains that the values are identical.