dr wrote:

gentlegreen wrote:


"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.

Indeed he did, he hired a glass bottle sonic "crusher" then scrounged the
bottles from the local pub, so everything was free. Then used some white
plastic tubing to direct the heat from the top of the GH down into the
bottom of the glass sump. It was powered by a solar panel (outside the
GH), but I thought the fan was a little more sophisticated than a simple
PC fan (could be wrong).

The real advantage of this is that it takes up no space, uses up no
energy, and basically just runs itself an ideal little extra heat during
the evenings, though there was no real demonstration of how well it
worked. Would be nice to see a max/min thermometer inside and out of the
GH to see what difference it can make. Though how you turn off a heat sump
I don't know.

D

Just watched the tape of this weeks episode, and I see they we're doing the
heatsink thing again, only this time using any old rubbish in the hole.
D