Temperature Effects
Temperature effects
- Normal operating cell temperature (NOCT)
- Expected temperature at
- 20C air temperature
- 0.8 kW/m2 insolation (0.8 sun)
- 1m/s wind
- For most modules this is about 45C
- This is listed on the panel
Temperature
- We can predict the cell temperature (REEPS2 Eq. 5.23)
Tcell=Tamb+0.8NOCT−20CS
- If it is hot, the cell temperature rises linearly
- If it is sunny, the cell temperature rises linearly
- S is the insolation in watts per square meter
- News flash: stuff in the sun gets hot
Temperature Coefficient of Max Power
- We can predict the maximum power based on the cell temperature
Pmax=PSTC⋅(1−temp coeff⋅(Tcell−TSTC))
- PSTC power measure in lab under standard test conditions (STC)
- TSTC cell temperature in lab under STC (25C)
- temperature coefficient is the temperature coefficient of Pmax %/C
Shading/mismatch
- We use the equivalent circuit model that includes resistances to show these effects
- These resistances dissipate power and reduce the output power
Shading
- To mitigate shading issues at the cell level we use bypass diodes
- To mitigate shading issues at the module level we use microinverters
Maximum power point MPP
Variation in temperature and insolation
Solar Tracking Types
Tracking Insolation
Hourly Temperature Derating
Derate calculator
PVWatts
- Simple solar photovoltaic estimation tool
- Created by the National Renewable Energy Laboratory (NREL)
- Online Calculator
Environmental Technology Center
- How would we estimate the derate for our panels here?
- How would we measure it?