On Wed, 27 Feb 2013 01:34:48 -0800 (PST), Graham Easterling wrote:

It is a very small drop, but get a lot of drops and you can start a
Boscastle!

But even all the drops if you covered the country in PV panels isn't enough
energy, even mid-day, mid-summer with no cloud anywhere.

I completely take your point about the need for backup. It is however
better to have a carbon emitting station working on reduced output for
much of the time, only peaking when 'renewable' input is low, than
having it working flat out all the time. (at least from an
environmental perspective)

But the efficiency of the dispatchable conventional plant falls as you reduce
it's output. So a plant running at 80% may well be burning just as much gas
as one running at 100%.

The need for backup reduces somewhat if you have a wide range of widely spread renewable options.

No every watt of direct wind, wave, tidal, PV renewable energy needs a watt
of backup as you do not know if those sources are going to be available at
any given time. Tidal is a bit different but will still have periods of low
output (neap tides).

About the only reliable renewable energy sources are the indirect ones, like
bio-mass and bio-gas. Where there solar energy is captured and stored, just
like oil, coal and gas except the turn around time from capture to use is
measured in tens of years or less, rather than millions. But the energy
captured per unit area is very low, so you need vast areas of land to grow
these fuel crops... Use of suitable waste as an energy source has a place as
well.

But no matter what renewables will struggle to provide the reliable energy we
have all become accustomed to. What is needed is a radical change in energy
use, ie reduce it. Renewables then stand a chance of providing it. Instead of
spending millions of pounds on subsidising commercial wind mills or funding
PV based monetary investment schemes(*) they ought to be ensuring that the
energy we do consume isn't wasted by, say, ensuring that *all* buildings are
properly insulated.

The "Green Deal" is available for everyone (I think) but TBH I'm not sure how
well it is going to work in practice. Take up essentially relies on people
feeling guilty about their energy use. IMHO the vast majority haven't a clue
about how much energy they use, the bill comes in they pay it, they might
whinge a bit when the price goes up but about all they can do about that is
to see if there is a cheaper supplier. As they don't have a clue about their
energy use seriously looking to see if they can reduce they amount they
consume is "too difficult". If they do look the primary motivation is a large
energy bill, are they going to opt to *increase* that energy bill via the
Green Deal? And if buying the Green Deal stays with the property, the new
owners *have* to take it over.

Wave power hasn't been mentioned yet, but there are a number of
projects, including the Wave Hub at Hayle.

Wave power seems to be in the same camp as fusion. As they were saying before
the 1970's "it will be commercially available 10 to 20 years".

It currently only has a max capacity of 20mw,

20 what? The unit is named after James Watt so has a capitalised symbol, ie
"W". Lowercase "m" is milli for 1/1000th or do you mean uppercase "m" for
1,000,000?

20 MW is also very little and would require backup as the waves aren't always
there.

but this is easily upgradable, as the cables come ashore at the old
Hayle coal fired station, so much of the infrastructure to transport
the power is in place. http://www.wavehub.co.uk/about/

"Wave Hub provides shared offshore infrastructure for the demonstration and
proving of arrays of wave energy generation devices over a sustained period
of time."

So it's a 25 year leased test bed rather than a commercial venture. Not going
to be much help in the next few winters...

Upgrade to 50 MW "once suitable components for operating the cable at 33kV
have been developed." So like wave and fusion not anytime soon...

And I wonder how well the cable risers from the sea floor to the sea surface
cope with the constant flexing/stressing, in salt water, at tidal and wave
frequencies?

I actually don't think our opinions are massively apart, just looking
at things from a rather different angle.

Quite possibly. You are glass half full, I'm glass half empty. Probably
influenced by how much energy renewables can be reasonably expected to
provide, how practical it is to realise that energy, how practical it is to
move that energy to where it is used and then add in time scales and cost.

Trouble is there are lots of stupid ideas out there How about this one?
Encircle the globe with a 10 mile wide strip of PV cells (avoids the night
problem), but how do you construct that across the oceans, how do you get the
power from the daylight side to the night side?

Have read "Without Hot Air"?

http://www.withouthotair.com/

(*) Would those that have installed or are going to install PV systems done
so if the payment for all the electricity generated was set at a 5p/unit
premium above their grid buying price? No index link and no guarantee?

--
Cheers Dave.
Nr Garrigill, Cumbria. 421m ASL.