Roger Chapman wrote:
On 25/11/2011 21:58, Dave Liquorice wrote:

Irrelevant for domestic PV installations. 4KW is well below the load
that even the meanest domestic connection will supply so no additional
infrastructure is required.

At the current low density of domestic PV systems but how many would
you need in a given area before the substation connected to them
became "undersized"?

Base load of an occupied house is around 1kW but these PV system have
peak output during the day when, generally speaking, homes are empty.
So most of that 4kW will be exported from each installation. Now if
the substation is sized on 1kW/home average once you get over 25% of
homes with PV systems there is potential for the substation to become
overloaded.

As TNP has yet to point out substations will be sized for the 'worst
case scenerio (not to mention future expansion) which could be the
5.30pm peak on the worst day of the year.

A significant number of houses will be occupied all day most days of the
week (pensioners, young families, shirkers, etc.) and even those that
are not have some maybe intermittent load such as freezers.

Not to mention what happens to the voltage in the area when all these
things are trying to export and that export disappears in seconds as
a clouds shadow moves across the neighbourhood.

You may have a point there but shadows move at the same speed as clouds
and the edge is rarely (never?) so significantly pronounced as to be an
on/off switch. The panels will continue to operate at a reduced level
even when not in direct sunlight.

Harry mentioned a figure of 90,000 recently. If the number rises to say
110,000 before the rate of increase reduces to insignificant that is
still only 0.5% of households. I think from now on we are only going to
see PV panels on new builds where they can be built in from scratch
with, in time, significant savings in roof construction to offset the
cost of the panels. How much does half a roof of tiles (or slates) cost.
The only price I know off hand (because I happened to be costing my roof
recently) is £420+ a ton for second hand Yorkshire stone slates (in the
order of 15 - 20 tons per roof). Concrete tiles would be much cheaper
and should weigh much less.

I think from now on solar PV will die a death and be as common as
Formica on new builds.

Quite simply no one is going to pay extra to have it, as it represents
an overhead maintenance wise, and a dubious benefit.