On 18/05/16 19:34, Chris Hogg wrote:
On Wed, 18 May 2016 18:35:18 +0100, The Natural Philosopher
wrote:

On 18/05/16 18:24, Chris Hogg wrote:
On Wed, 18 May 2016 18:06:54 +0100, The Natural Philosopher
wrote:

On 18/05/16 17:17, Chris Hogg wrote:
On Wed, 18 May 2016 13:59:31 +0100, Chris Hogg wrote:

On Wed, 18 May 2016 11:45:44 GMT, lid (AnthonyL)
wrote:

Out of curiosity, anyone calculate how many panels
would be needed to lift one ton(ne) in say 6hrs of average light?

To make that question sensible, you'd need to specify the height
you're lifting it to.

Here's a calculation (stepwise, for my benefit, and to allow it to be
torn to shreds by those who can do it better, as I don't believe the
result!).

The upper lake at Dinorwig is a little over 500 metres above the lower
lake, so I'll assume a height of 500 metres.

1 tonne exerts 9806 Newtons of force.

The work done raising 1 tonne by 500 metres is 9806x500 = 4903000
Newton-metres.

A Joule is 1 Newton-metre, so the work done raising 1 tonne by 500
metres is 4903000 Joules.

This is achieved in 6 hrs, or 6x60x60 = 21600 seconds.

Units of power are Joules per second

So the power required is 4903000/21600 = 227 Joules per second.

A Joule per second is a Watt.

So the power required to raise 1 tonne by 500 metres in 6 hours is 227
Watts.

AIUI a typical domestic solar panel delivers 260 Watts at full blast.

So 1 panel should do it, with a little to spare.

I find that hard to believe! Where have I gone wrong?

Seems OK to me. 100 meters an hour is 27mm or a little over an inch a
second.

A human being with a tackle can lift a tonne that fast easy.

In fact an Irish Navvy could shovel and lift 30 tonnes a day back in the
50's.

I think you are encountering the true meaning of 'energy density' - that
a tonne of water up a hill is actually not really that interesting -
maybe a couple of Kwh at best.

Thanks for the confirmation. Reversing the calculation, as it were,
Dinorwig dumps 60 tonnes per second through its turbines, from a head
of 500 metres and for a period of 6 hours. If 1 tonne moving through
500 metres in 6 hours is equivalent to 1 solar panel, Dinorwig is
equivalent to 60x21600 solar panels, i.e. 1,296,000 panels. I'll leave
it to AnthonyL to work out how much of Wales that would cover!

Actually insolation is on average about 100W/sq meter and a solar panel
maybe gets to 25% efficiency, so 25W/sq meter on average. Obviously
midsummer midday peaks are considerably higher - 10 x that.

IIRC Dinorwig can peak at 2GW, but not for 6h, thats less than a GW at
that level.

At 4 sq meters per hundred watts, that's 40 sq meters for a killer-watt
or 40 sq km for a gigawatt?

Hmm...yes, I see my mistake. It was in assuming a typical solar panel
produce 260 Watts at full blast. That's a mfr's figure for peak output
when insolated at 1000 Watts/sq.m. As you say, with insolation at 100
Watts/sq.metre and a conversion efficiency of 25% gives 25
Watts/sq.metre, so the answer to the OP's question is about 10 panels.


Yes. Its a very easy way to confuse greens and paint solar energy as
better than it is by using PEAK output rather than AVERAGE output.

I.e. 'Britain has 4GW of domestic solar capacity. Britains average
demand is 30 GW.

WOW!. 7% of all our electricity comes from solar!

NOT!

The average output of those panels is 400MW. And almost none of that
comes in the darkest months of winter when it is needed the most.

And if Euean Mearns is to be believed, that solar took more energy to
erect than it will ever pay back, making it utterly pointless in terms
of carbon emission reduction anyway, and if the rest of the skeptics are
correct, carbon reduction in the atmosphere won't do anything except
hamper plant growth.



--
"Anyone who believes that the laws of physics are mere social
conventions is invited to try transgressing those conventions from the
windows of my apartment. (I live on the twenty-first floor.) "

Alan Sokal