On 8 Jan, 12:13, Peter Parry wrote:
On Mon, 7 Jan 2008 14:18:20 -0800 (PST),
wrote:

(1) We're considering ploughing some money into some a renewable power
source for our home. I knew of government grants, but I also recall
reading recently that the grants were either being cancelled or cut
back substantially. Has anyone taken advantage of such a grant
recently? Does the installation company sort it all out or does the
consumer have to claim it back themselves?

Grant availability is inconsistent but some companies are particularly
adept at managing the grant process. It is fairly straightforward and
they seem to be able to get approval quickly. The only problem is
that the companies approved under the grant schemes have almost
universally inflated their prices by at least the value of the grant
so the end user gets no benefit from them.

(2) Of the various options available (I can think of at least three)
has anyone any experience across each type? Are some more effective
than others in terms of energy return for a UK home? Are some more
problematic regards installation?

For most of the UK roof mounted wind turbines are useless other than
as a green fashion statement, There is an ongoing project in
Warwickshire (The Warwickshire Wind Energy Project) assessing their
effectiveness and although little factual information is being
released so far the monetary saving has been in the order of a few
pence a day. Typically in an urban environment you will generate
electricity worth about £4 in one year. The problem is the lack of
wind in urban environments coupled with the inescapable cube law on
energy produced against wind speed. A figure often bandied about is
that the "average" windspeed in the UK is 5.6m/s . Assuming that
produced 100W output from a generator if the wind speed dropped to
3m/s (higher than that being measured on houses in the Warwickshire
trial) the electricity generated falls to about 12W.

Hot water systems are simple but generally have inflated installation
prices, they only make economic sense if done as a DIY project. I had
one for some years and it was an interesting experiment but not much
more. The DTI carried out a 12 month trial of various panels and
found that a single solar panel of any type if optimally sited would
collect about 1MWh of energy in one year, equivalent to a saving of
about £40 if you use gas to heat your water. It would cost between
£2,000 and £8,000 to install commercially. Vacuum tube collectors are
more efficient than flat panel but tend to be made into smaller panels
so generally there isn't much difference between panels. There is
very little difference between manufacturers. Navitron are worth
looking at for DIY bits as their prices for the vacuum tubes are quite
good.

Solar PV is useful in remote sites where there is no mains
electricity. Its cost is prohibitively high except in these locations
or to power individual low consumption devices. The roughly 1sqm BP
panel I have as an experimental setup originally cost nearly £1,000
and produces about 60W in bright sunlight but today for example, with
a very dull overcast, is producing about 3W. It makes no economic
sense if grid electricity is available as the payback period is much
longer than the panel life.

A problem with solar energy in the UK is that there isn't much sun
when its needed and most comes at the time of least energy usage.

(3) Installation companies are many, I know that BP have a solar
business and will more than likely have a list of contractors on their
books. I would feel a little safer dealing with a large organisation
but I don't expect they will be as cheap as others.

The great majority of "alternative" energy companies are out and out
fraudsters. Almost universally they make vastly inflated claims for
the capability of their products. The skill levels generally in this
sector are poor and although there are some enthusiasts who are also
competent it is difficult to find them.

In financial terms none of the three common technologies make sense.
Air source heat pumps (inverter air conditioners) can. Ground source
heat pumps are beginning to make sense especially if you have a lot of
land and are planning major works anyway but don't work too well
unless you have underfloor heating. They are also no better than a
good condensing boiler in terms of heating costs or carbon emissions.

There is some data on ground source heat pumps from the Barratt
Chorley experiment (which used a 30M borehole rather than a widespread
network of pipes so is better suited to urban environments) which
indicates a payback period of about 15 years.http://www.barratt-investor-relation...ses/Content.as...

What is universal about all the ecotechnologies is that the potential
energy generation or saving is invariably grossly overstated and this
is becoming clearer now actual measurements are beginning to be made
public.

There is no doubt that if you spent the money you were contemplating
spending on alternative energy on insulation and better and more
controlled ventilation and heating you would get better value for
money.

I'm still to be totally convinced by heatpumps. COPs of 4 and even 5
are advertised by manufacturers, yet the only real world figures I've
been able to find are 2 or a bit better - and that's ground source
with UFH and plenty of insulation. I know that with green technologies
in the home it's compulsory to exaggerate about their performance, but
I simply couldn't buy a heat pump from someone who I know is lying to
me. Also, when it comes to payback, the additional cost of UFH etc. is
not factored in. I know some manufacturers say you can use radiators,
but they already lied about the COP, so I don't believe them.

What sort of COP can air source heat pumps really achieve on average
throughout a heating season, with radiators, and supplying hot water?

T.