On 20/05/2012 16:47, Dave Liquorice wrote:
On Sun, 20 May 2012 07:32:36 -0700 (PDT), Graham Easterling wrote:

I installed my panels initially as a 'green' measure, ...

Do you have figures to show that they will be energy positive over
their lifetime?

Yes. They do actually pay back their energy to create even at our high
latitude but only by about a factor of 4x energy of manufacture. See for
example David MacKays debunking of the myth that it never pays back
which is base on prehistoric inefficient thick film solar cells.

http://www.inference.phy.cam.ac.uk/w.../page_41.shtml

Installed somewhere sensible they would get more like 7-10x.

To put it in context the figure of merit for a wind turbine is about 80x.

... but they are exceeding expectations. I'm set to get my money back in
10years, even allowing for interest in the money (@ 3%gross) if it was
invested for the 10 years.

That is a pure financial expectation, nothing "green". A financial
benefit that would not exist without the huge FiT payments funded by
everyone elses electricity bills.

But if the government are daft enough to subsidise it that way...

Also changing all my 50W downlighters for 5W LEDs ... has made a huge
difference to my power bills.

You could have done that anyway.

And he will surely live to regret doing it.

High power LEDs retrofitted into existing luminaires not designed for
their proper thermal management will die young and horribly. Even some
of the better engineered mains powered LED units suffer from cooked
capacitor fatigue in the same way that computer motherboard PSUs do.

--
Regards,
Martin Brown

On May 21, 9:43*pm, Martin Brown
wrote:


Yes. They do actually pay back their energy to create even at our high
latitude but only by about a factor of 4x energy of manufacture. See for
example David MacKays debunking of the myth that it never pays back
which is base on prehistoric inefficient thick film solar cells.


About 6x on the south coast according to most figures

Installed somewhere sensible they would get more like 7-10x.

To put it in context the figure of merit for a wind turbine is about 80x.


It's massively variable depending on location. There are serious
maintenance issues with turbines, I know several people who have them,
both on farms & the local YMCA, and they've all had significant
problems. There is the energy use in sorting it that is often
excluded.


Also changing all my 50W downlighters for 5W LEDs ... has made a huge
difference to my power bills.

You could have done that anyway.

And he will surely live to regret doing it.


No I won't. I was able to get them in bulk from a electrician friend
of mine. At the time I bought them they were £20 or so online. I got
them for £14 each. They come with a 3 year guarantee.

If a light is only on an average of 2 hours per day, the saving by not
using a 50W halogen would be just over £16 (assuming 15p per unit)
Knock off the £1.60 the LEDS cost to run using the same figures and
I've covered my outlay in the guarantee period, without taken into
account continually having to replace the halogen bulbs. I've had them
8 months so far, and apart from 1 faulty on arrival (and they replaced
it & gave me a free 1 in exchange) none have so far expired. The
ventilation issue was one reason I chose the bulbs I did, as they are
supposed to run cool compared with most others.

That's the financial side, there's also the green side of reducing the
energy I use in lighting by almost 90%. I'm now in the situation where
I receive as much in FIT as I pay in bills, so I see no need to regret
it, but thanks for your concern. My last words on the subject
(honest!)

Late reply as I've been up at Polzeath & Rock enjoying summer.

Graham
Penzance