Chris Skrimshire wrote:
Hello Solar experts,

I am wondering whether the cost, subsidised or not, of a domestic PV solar
installation may be set to come down.

Solar is continuing to come down, but at a lower rate in absolute terms
because everything is so much cheaper than it used to be. That's not a
reason not to do it now though - technology is usually cheaper/better next
year, and if you waited for that you'd never buy anything.

My house roof orientation is not ideal for solar panels but I have a
flat-roofed studio in the garden that is not overlooked and which could be
a good site.

But my main question was whether anybody had knowledge/experience of
orientation sun tracker systems. I read that the overall efficiency could
be increased by up to ~30% by optimising solar capture and I would like to
know whether the cost or complications of a tracker system make this
viable? Am even wondering whether a diy system might be feasible?

If you go he
https://www.pvfitcalculator.energysavingtrust.org.uk/
you can do some calculations for roof slope, shading and orientation.

Doing the sums for my garage, let's say it's 2kW of panels and faces south
at 30 degrees of inclination, with 'modest' shading. It says 1495 kWh/year.

If I then say 0 degrees (flat) it's 1331 kWh/year. About 12% worse.

My take on this is that it's a garage so access is just a ladder - no
scaffolding or other awkwardness. It's also not super fussy about appearance
(flat roofs are never pretty anyway). That means it's feasible to DIY. If
I lay the panels flat they're easier to mount, there's no planning
implications, and there's fewer problems with wind loading. They also
provide some UV protection for the flat roof.

Now, the next step in this plan is to look at secondhand gear. Perhaps it
won't be quite as efficient as new, but the cost is a lot lower. The
lifetime of secondhand panels might be lower, but then I can just go up a
ladder and change them - no expensive scaffolding needed.

I hadn't thought about solar trackers, but one site suggests they add
25-35% for a single axis tracker, and another 5-10% for dual axis.
I'm not sure how much it would cost to make a DIY tracker, but for me it's
not an option due to planning, and wind loading (although I suppose they
could go to flat if wind was forecast above XX mph).

I'd be interested to know if there's a way to make a cheapskate roof
tracker. But I suspect it's not going to make sense over just buying more
(used) panels, assuming you have enough roof for them.

Theo