"Adrian" wrote in message
...
Hi all

On 28 Mar 2007 05:52:38 -0700, "adder1969"
wrote:

On Mar 28, 11:04 am, Paul Waites wrote:
Hi all,

Last year there was a BBC2 programme called "Its not easy being green".

In one of the episodes the presenter Dick Strawbridge built a
greenhouse
heater out of a computer cpu fan, solar panels and a bit of piping....

Now that I've erected a nice shiny a wanted to try out his idea (It
involved circulating the air from the top of the house back into the
gravel bed on the floor.

I can't find any link on the internet or the BBC's website..... Has
anyone tried this idea or knows where there are plans for such a
scheme.

Thanks,

Paul.

The show appears to be back on.

I would suspect, solar panels power the fan which blows air down a
tube/pipe into the gravel. whether it really works or not I
wouldn't like to say.

Yes - that's how it (was claimed to) work.....

The principle has been around a long time - and is used in
house heating - it's effective where there are large differences
between day-time and night-time temperatures.

The key to its success would be how much airflow you could get from
the PC fan, and how much gravel you had to store the heat in....

I guess that most of us would open the greenhouse vents when it go
really hot in there - so much of the hot air would escape. Also, a
simple 'solar panel runs the fan' approach would not account for
bright, cold days - where you might well end up pushing what little
warm air there is into the gravel bed - which might not be what you
want.....

Like much of the 'science' in the programme, I got the feeling that it
was done for the sake of 'good TV', rather that being particularly
'green'. Dick likes 'making things' - which is great - but some of the
things he devised in the series seemed to be a triumph of ingenuity
over common-sense...

A cheap way of storing the heat in a greenhouse (if you have the room)
is to put as many black-painted oil drums in there as you can manage.
Fill them with water. When it's hot in the greenhouse the drums &
water will absorb the heat, when it's cooler the drums will rediate
the heat back into the greenhouse. Probably just as effective and the
gravel bed system - and no moving parts to go wrong !

I seem to remember he used recycled glass cullet. I don't know if that makes
any difference.