Is domestic solar nearly as cheap as big solar? Lessons from Australia and UK

Solar pv expert says domestic solar is nearly as cheap as large scale solar

 RACHEL LEE, who has worked extensively in the solar and also wind industry  discusses how the battery and solar industry is coming together in Australia and how this compares with the UK

South Australia (SA) does have some incentives in place for batteries – I doubt they would yet be economic without support.  However, SA is different to here (UK)- the PV capacity factor is 50% more than southern England/Northern Europe for a start!  SA in particular also had very high electricity prices for a while – that was blamed on a big shift to renewables (there is actually lots of wind resource in SA too), but, having worked for the market regulator in Australia for a while, I doubt that had much to do with economics – more likely to do with Victoria/NSW(New South Wales)/Queensland Government ownership of ancient inefficient coal plants.

There are issues regarding stability in SA since it’s only linked synchronously to the rest of the network by a single dual circuit overhead line (there’s a 200MW DC interconnector too), so it’s necessary to have enough inertia and frequency response in SA to cope with interconnector loss – that’s partly why the big Tesla battery was so effective there.

 So those things have made rooftop solar + batteries look economic vs the grid. I’m not sure how that would compare to a new interconnector to NSW today, but that was being mooted when I was there (2001-2004 )and the economics didn’t stack up – these are long distances of course!

 On residential vs large scale, I’m not so sure the differences are so big when it comes to solar PV.  I’ve been involved in a few big PV schemes in the UK, including a multi project site in Norfolk which has 65MW of capacity.  But dig into that, and you will find 200,000 PV panels of exactly the type you would put on your roof and about 900 inverters each about 10-20 times the capacity of a domestic unit. On top of that there are 30 x 1.6MVA 400V/33kV transformers and a bunch of 33kV ring main units and switchgear, and  an expensive grid connection; none of which is required for domestic PV.  Plus you don’t need any mounting system or foundations for most domestic installs.  The costs at the end of the big PV push (about 4 years ago) where getting below £1000/kW for large scale stuff, but that’s about the same as a domestic install costs today.

 In practice some the the SA solar and battery capacity is under ‘Virtual Power Plant’ control and that’s likely to expand, so there in lies a question as to whether residential systems are really residential systems?

David Toke: This article is a (very slightly) edited version of a commentary by Rachel Lee posted on the Claverton Energy Group email group,

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