wrote in message
oups.com...

Dont attempt to solar heat a thermal
store / heat bank, as DHW panels
run this way will have very low efficiency,
and contribute close to zilch.

You xclearly know little of thermal stores/solar to come with such a crass
comment.

Preheat cylinders are used because
they are the one way to get
good efficiency from unconcentrated panels.

The pre-heat cylinder can be the bottom half of a thermal store, not heated
by anything but solar panels. The DHW drawoff can take off water from the
solar section and when too cool start to use the cooler solar heated water
for mixing, instead of much colder mains water. An depletion of hot water
in the upper section heated by a boiler, will be replaced by warmer water
from the lower section, not very cold mains water, hence keeping the burner
off for longer. Not difficult or expensive to do, using only a 3-way
blending valve with a remote temperature.

Also any solar generated heat can be used for CH too.

Preheat cylinders are notorious for being inefficient to all one cylinder
thermals storage.