Solar Inverter Sizing

[jamj]

What size of inverter would you put on a 12KW system?
It has been suggested that a 10kW inverter on 12kW array will give a better performance over the whole year than will a 12 kw inverter even though at peak output the output will be clipped.
Is this correct?

 

[mikelaluz]

What size of inverter would you put on a 12KW system?
It has been suggested that a 10kW inverter on 12kW array will give a better performance over the whole year than will a 12 kw inverter even though at peak output the output will be clipped.
Is this correct?

Hi jamj

If your installer is suggesting this then he knows his stuff - The reasons are as follows in the UK...

• PV modules operate for much of the time below the nominal rated power. Nominal rated power is the output of the module under standard test conditions (stc) - a condition reached relatively infrequently.
• Following on from the above, inverters will spend much of their time operating at power levels below the nominal array rating.
• Inverter efficiency is lower when it operates at low power levels (look at a few inverter efficiency curves). By a degree of inverter under-sizing, it is possible to take the normal operating regime higher up the efficiency curve – and hence decrease inverter losses at times of normal irradiance levels.
• Module / array output decreases over the lifetime of the PV system

Hope this helps

Kind Regards

Mike Smith

 

[jamj]

Thanks, Mike for your helpful reply.

 

[Simon Glew]

agreed