1) 14 Yingli 235 watt panels
2) SMA SB3000 Inverter
3) SMA datalogger (Webbox)
4) Elster A100C Generation Meter
5) DC and AC isolating switches
The location is Belvedere in the
borough of Bexley on the SE London/Kent border, the
roof has a 30º inclination totally unshaded and about half a degree east of due south.
A transformerless inverter was rejected because the existing
earthing arrangements would have required extensive and expensive modifications
and the cost together with additional cost of the inverter when compared with
the anticipated improved efficiency pushed pay back time beyond the inverters
probable life. The fact that the transformerless variant of the SB3000 was
subject to a six week supply delay was also a factor.
A 3kW inverter was chosen for 3·29kW panels on the advice of the installer who
produced performance curves which showed that greater efficiency was obtained by
keeping the inverter operating close to its limits and that the output on days
when 3·3kW might be achieved was outweighed by the extra efficiency obtained on
less than perfect days.