On 1 Dec 2005 00:02:31 -0800, wrote:

Peter Parry wrote:

Of course you can reduce water consumption dramatically. There is no
requirement to wash at all,

There you go off on something neither sensible nor relevant.

It is both. The last time solar water heating enjoyed a burst of
popularity it was because of forecasts of even more draconian hikes
in energy prices than are being predicted today. By now, according
to those prediction, we should be on one candle a day (and don't
forget the 12 people per house caused by the world overpopulation
predictions of the same era).

Whilst I agree there is scope for considerable improvement in new
house constriction there is no sign of it being planned, never mind
realised and even if it happens it will have negligible overall
effect for many decades.

In the meantime people are using more energy. In the 70's there were
still quite a few taking only a weekly bath and showers were both
relatively unusual and very anaemic. Hot water use per person was
about 30% less than it is today. It is possible to reduce water
consumption - there is no indication that people would accept it
happily and despite Nulabors efforts to make it difficult they can
still be voted out.

At the same time there is a huge growth in appliances using
electricity. Society is showing no significant sign of becoming less
energy hungry and any savings due to efficiency will be neutralised
by expanding energy use.

The only way to make a severe impact on energy use is to put fuel
prices up three or fourfold and any government that was in power when
that happened wouldn't be shortly thereafter. The threat of being in
opposition next week is far more potent than that of global decline
next year as far as a politician is concerned.

The sums are more impressive for new builds, so thats where they'll
make inroads.

A great deal could be done (at a cost) to new buildings but much of
what could be done requires room - which runs directly against the
present policy of trying to cram as much as possible into as small a
space as possible. It's all very well promoting a noisy windmill for
every home but when you don't have anywhere to put it except against
your bedroom window it isn't terribly practical.

just spend the money you were going to waste on solar
panels on more effective ways of conserving and gaining energy.

I agree with that. But the interest is almost exclusively with DHW for
some reason, and has been for decades.

Probably because it is the only practical system which can be
retrofitted and can be demonstrated to "work" in that it produces hot
water in the summer.

It has a market, and in time I
think it will pay, once the sleeping industry is roused by a competent
competitive team. And I think it will be at some point. Rising energy
costs will help as well.

That's what was said 30 years ago :-). Competition only works if
there is some. Solar water heating is a niche market with prices all
at the same sort of level and everyone involved making a comfortable
living out of it. That isn't a market where significant price
competition develops. 30 years ago there actually was some limited
price competition and one or two national companies with aspirations
to become very large invested a lot in marketing themselves. They
fell by the wayside. There simply isn't a commercial incentive to
try to do better.

A jump from 65% to 91% is 26% more efficiency. So one's annual gas
spend would have to be fairly extreme to achieve that sort of saving.
These are not realistic figures, or even close.

The figures came from the Energy Saving Trust - an "independent"
Government funded body providing "independent evidence-based policy
analysis" just like the "Sustainable Development Commission". Surely
you are not suggesting that these independent organisations would put
out blatantly incorrect information? :-)

Funnily enough that was exactly what was said in about 1975. In the
meantime the "technology" (there really isn't that much involved) has
progressed minimally

If you review the patents granted since then I think you'll find there
are many new technologies. There have also been some significant trials
since then.

The effectiveness at gathering energy is not going to increase
significantly, systems in 1975 were about 70-90% effective, the
figures are not much changed at the present and getting much above
that figure in the future is unlikely. Different manufacturing
techniques and materials may lower the production cost after a time
but not in the short term if R&D costs are to be recovered. Moreover
most companies in a non-price sensitive market will use lower
production costs to boost profits - not to lower prices.

And its fair to say that DHW is not the hottest
area of solar research, since there are bigger fish to catch elsewhere.

For new builds especially - at least if the problem of shedding
excess heat in the summer can be solved :-). What you do with
existing housing stock is a different problem.

The market has existed in many countries for centuries, you simply
can't develop what isn't there to develop.

There is more than enough insolation on lots of house roofs to heat DHW
with a 50% efficient system. You keep saying there isn't enough over 2
sqm, but I'm not sure that tells us a great deal, except that the
commercial systems you refer to are basically expensive novelty
products.

The 2sq/m is representative of typical retrofit installations. With
present systems there are minimal economies of scale - if you go for
10sqm you have hot(ish) water most of the year but the installation
cost rises proportionately and you just lose more money.

--
Peter Parry.
http://www.wpp.ltd.uk/