David Hansen wrote:
On Sat, 23 Sep 2006 16:10:39 GMT someone who may be "Bioboffin"
wrote this:-

Please enlarge on this! We have double glazing; draught proofing; a full
layer of insulation in the attic. What do you suggest now, before going for
solar panels?

drain heat exchangers can pay back fairly well, though maybe not if you
have to take the bath out to get one in. HRV is worth a look too.


Don't be fooled by advocates of solar space heating.

It'll be interesting to hear you explain that.

It may work
well in a location where there are cold nights and sunlit days.
However there are few deserts in the UK.

Night time temperature has nothing to do with it, nor does the absence
or presence of a desert. The relevant difference between desert
conditions and our winters is direct vs diffuse sunlight. Flat panels
work with diffused light. To achieve good temp gains the design may
need to be slightly different, but not by much. The same process is
going on, and in either case the same big advantage of space heating is
there, the high panel efficiency.


In the UK solar space
heating can reduce the load on other forms of heating during spring
and autumn, but it is not an all year system.

Why do you think panels can not work in winter? Its fairly basic
science. Certainly there will be more output at the ends of the heating
season than the middle, this is true for all solar thermal systems.


If you have a suitable
house a passive design, can be added on, but don't expect too much.

Surely what you get depends on what solar system you design and build?
How does house design affect the panel output? It doesnt, as long as
the panels point the right direction.


You also need to consider hot water consumption.

Yes... and thats precisely why space heating yields more return. Theres
only so much DHW a house uses. Much more space heating energy is used,
thus much bigger potential paybacks are available there. Plus setup
cost is much lower.


Electricity generating panels are still uneconomic if measured on
simple payback, or discounted cash flow. However, this will change.

I hope it will change greatly one day, but it isnt likely to be any
time soon. There is nothing significant in the research pipeline.
Energy prices wont change the equation by a lot, as the cost of system
purchase depends on energy cost.


NT