Rhiannon Macfie Miller wrote:
Having had a poor germination rate (30%) of tomatoes both this year in
my conservatory and last year on my dining room windowsill, I was
wondering whether a more constant temperature would help. I was
thinking about a smallish heated propagator. Are there any such
things available that run on solar power or are otherwise
environmentally neutral?

Rhiannon

There may be better methods, but photovoltaic cells are not even worth
considering.

A seed-tray size heated propagator uses about 10 watts. A solar panel which
could generate 10 watts in average light (not full sunlight - as most
figures are given as "peak" output) would cost well over £100 (nearer £200 -
300). Then you would need the control electronics, and a battery to store
the generated electricity. Of course, when it's dull, and when you'd need
the heating most, the power output would be even lower.

Also, the propagators available in your local garden centre, etc, are all
240v. Common solar panels are rated at 12v. So you'd need a voltage
converter (another £20 or so), or a low voltage heater. For the latter a
12v mirror demister would probably do the job for around £15 - 20.

Add it all up and you're looking at well over £250. A unit of electricity,
even at the current exhorbitant prices, costs less than 20 pence (even less
if you use night rate electricity). You could run the propagator heater for
over 4 days for that. So for around £1.50 a month, or say £6 for use from
February - May inclusive you get a heated propagator.

--
Jeff
(cut "thetape" to reply)