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wrote:
Ian Stirling wrote:
wrote:
Ian Stirling wrote:
Mary Fisher wrote:
snip
You have a stack of n (where n is a large number of panes, which absorbs
say 80% of incoming light before it hits the bottom.
The air is drawn past these from the outside in, in a serpentine
fashion, so that the inner panels are hottest, and hopefully essentially
all IR radiation is trapped.
I wouldn't be surprised if 2-300C was possible.
But, it'd use a hell of a lot of glass, and probably take a long time to
start up, due to thermal inertia.

ok theres a proven system a bit like this using shade cloth. 2 or more
layers of shade cloth, just one of glass. The air flow is from near the
outer glass towards the inside, through the cloth, and efficiency is
very high, far above any black or selective absorber system. And the
cloth is cheap, unlike glass.

Interesting.

If you have a lot of glass, how about a hot air collector with one
sheet of glass and one poly?

Possibly - there is an obvious tradeoff (for non evacuated panels)
between power output, and maximum temperature.
Obviously, adding another layer of glazing will always increase the
maximum steady-state temperature, but due to absorbing some light, will
decrease the power output.

only above a point. Double glazing will give more power out than
single, as conduction losses are less. Triple may not. Extending the dg
layer below the first glazing layer also provides reduced heat loss.

To restate.
Adding another level of glazing will increase the maximum temperature it
will reach at 0 flow.
It will reduce the maximum power output at a reasonable flow to below
the temperature without an extra pane, due to the lower power due to the
losses from the first pane.

snip
I suspect a 'low temperature' panel, and a high temperature one may be
worthwhile.

this is what I've been thinking about for some time now. Each panel
type performs best in different parts of the system. Eg vac tubes for
the top of the tank, as theyre the only thing that performs sensibly at
high temp, rads as a simple minimum cost inlet prewarmer, and flat
panel for the bulk of tank heating.

Also wondering what the possible ratio of a fan assisted panels
radiator/panel size is.

I still cant see what you mean there

2m^2 panel, 1m^2 radiator and a fan.
Or 0.5m^2 radiator, ...

Helps with the thermal inertia thing as well as to some extent the cost.

still just as puzzled

Ok, in more words

Instead of having a 1m^2 radiator, in a 1m^2 panel, you have a 0.5m^2
radiator in a 1m^2 panel, and a fan, to circulate the air to the
radiator.