B&Q Solar

[Peter Parry]

The question he asked was about a specific windmill in a specific location for a specific building - his house.

Indeed it can, given an isolated location and an appropriate height of mast and size of turbine. You also need a shed to hold the battery banks if you want it to do _all_ the electricity you use as even in Benbecula the wind occasionally stops.

It is wrong to claim it can be achieved in anything other than a minority of cases which are almost all isolated sites surrounded by countryside.

See

but a figure of 30% sounds

It is completely impossible. Most of the population in the UK lives in urban areas which are wholly unsuited to wind power, a point Hugh Piggott continues to make and various propaganda and sales outfits continue to ignore. The combination of low wind speed and turbulence make most urban areas almost useless as wind generator sites.

Of course it is easy to misleadingly describe "most of the UK" as most of its land area (where no one lives) as opposed to "most of the population" and then dishonestly extrapolate that flawed assessment into how much people in cities can benefit from wind which isn't there.

To look at misleading figures go to

and enter an urban postcode. For this location it says :-

"According to our wind speed database the average wind speed at postcode hpx 9xx is 4.4 m/s and the Iskra AT5-1 small wind turbine should generate 6.48 MWh per annum. This could result in an annual energy bill saving in excess of GBP777.60 and a CO2 emissions saving of approximately 3.24 tonnes."

The wind speed figure is from the DTI database and, for urban environments, is inaccurate. The generated energy figure is consequently also inaccurate so the "annual saving" is greenwash.

It also says "Please note that the Iskra AT5-1 turbine is not suitable for domestic roof top mounting as the turbine is 5.4m in diameter and is mounted onto a tower which is at least 12m tall. You will need a location that is at least 50m from your nearest neighbour's property and exposed to the normal wind direction."

(Actually it needs to be a tower at least twice the height of the surrounding building plus the rotor radius.)

There are a lot of those sites in most towns.

It isn't that difficult of course to estimate if a site is suitable. Using the Griggs-Putnam Index of Deformity you can get a good idea from local trees. Any site showing an index above 2 should be suitable and a diagram showing this is at

Go and look around - how many trees in urban areas show the minimum "slight flagging" (an obvious asymmetry in growth) caused by constant wind?

Why isn't this simple site assessment technique mentioned in any of the greenwash information?

Looking at the wind power density it is easy to see how far out the manufacturers and proponents claims are.

has wind power density at table 4. For the B&Q offering at this location (fairly typical of any town in Hertfordshire) the wind energy available is less than 100w/m2. Assuming the generator ever starts (the average windspeed is lower than the higher boundary of its start speed) it is going to produce something like 30w. Not bad for a GBP1500 "1kW" device.

The Danish Wind Industry Association produce a useful calculator available at although its really aimed at larger turbines. It also has a comprehensive set of wind assessment tools in the wind reference manual (which is an excellent source of information)

This explains quite well the difference between the DTI's optimistic results and the figures measured at urban sites.

With a predicted speed of 4.4m/s (the DTI figure) and a roughness class of 3 it predicts a wind speed of 2.2m/s - much closer to that measured and well below the generator cut in speed.

rooftop wind generation in urban areas in most of the UK is incapable of producing any worthwhile energy and those claiming 30% of the generators capacity as a realistic output are either woefully ignorant or manifestly dishonest.

No, they have a habit of making press announcements they don't want anyone to read at 9PM on a Saturday night in an empty church hall in Stranraer, a lot of people miss them..

[Peter Parry]

Not that I'm aware of in the UK - there were promises of on-line output measurements accessible to all but they never happened and I'm not aware of windfarms which publish these figures. The Danish site may have some information on their locations (see

[David Hansen]

On Sun, 15 Oct 2006 18:51:46 +0100 someone who may be Peter Parry wrote this:-

And did they do a survey of his house and wind measurements over long periods which would be necessary to give specific advice? I doubt it very much.

[Andy Hall]

.. and neither would they, which is what makes the whole thing so ridiculous.

[AJH]

NB this was *not* a solartwin installation.

I probably agree but see below. IMO displacing enough gas to produce a decent roi is good enough.

You miss the point that an expensive "solar" dhw tank was fitted and it replaced an adequate normal one. There was no benefit in the "solar" tank other than increased capacity because it was not configured to make the best of the attributes of the solar heating.

AJH

[AJH]

This strikes me as lacking the means to verify the various claims, I wonder why? John Rumm pointed me to an isp that provides real time graphs of their bandwidth use by different types (ftp, http, e-mail p2p etc) higher in this thread. Now why won't my local council, a leader in sustainable energy provision, publish the same real time graphs for their pv installations. BTW they propose for 3 wind turbines here and as far as I can see average windspeed at 30m above ground is

[Peter Parry]

Of course not, propaganda doesn't need facts. The information to allow a correct answer to be given for an urban environment is freely and easily available. Rather than give it they chose not to use it. They gave an answer which would be wrong for 90% of the population. They deliberately chose to mislead.

This is the problem of greenwash - it is made of lies and deception.

[Peter Parry]

It may have something to do with the only one which has been publicly verified having produced less than a third of its promised output, but I'm sure it isn't.

A few places (Southampton University is one ) do have on line monitoring of experimental PV panels but not turbines. Most wind purveyors seem to prefer the used car salesman's approach and quote the highly scientific output figure of "3,000 average households" or the like. What is pretty clear is that both the availability and the real output invariably fall well below the predicted figures.

Apparently when a local school installed a windmill with data logging intending to make the information available on the schools web site the supplier put a clause in the contract forbidding access to the information from it to anyone outside the school intranet.

There is a vast amount of money being made from subsidy farming, far more than from wind collection and no one wants to rock the boat.

[DJT]

Been reading this discussion with interest as I live in a very exposed and windy location. What would be the best and cheapest way to measure wind speed so I can decide whether a wind generator would ever pay for itself in my location.

[David Hansen]

On Sun, 15 Oct 2006 22:56:38 +0100 someone who may be AJH wrote this:-

I never claimed that it was. However, their instructions to installers speak about altering existing controls and I imagine other instructions are similar in this respect.

Incorrect.

[David Hansen]

On Mon, 16 Oct 2006 00:39:33 GMT someone who may be DJT wrote this:-

The equipment is often expensive. However, navitron sell a weather station that may be suitable for under £100.

[Peter Parry]

You probably don't need to, nature has already done it for you. Firstly, if you are in an exposed area away from other buildings the DTI estimator at

is reasonably accurate. If you are in an urban area divide what it says by two at least.

Secondly, and probably more significant, is look at the trees. Use the diagrams half way down the page at

to estimate the wind.

If this all looks good read

to see a bit about the influence of ground shape.

[JohnDW]

In the tradition of DIY :-) A toilet-roll and sticky-backed plastic solution:

Replace the motor-used-as-a-generator solution with a pulse counting mechanism using a magnet and reed switch or photocell and input the pulses into a computer programmed to convert the pulse rate to wind speed...

[AJH]

Yes that's the sort of thing I meant, the graph could be a better definition and I would have preferred to see the output visualised as a fraction of the installed capacity. Also a view of recent history and the date from which the accumulated total started as well as the accumulated total as a fraction of the installed capacity times uptime. I think this would give a lay person an immediate feel for the possibilities.

That's fairly apparent from comparing the wholesale electricity price with the value of the ROC. It was probably necessary to reward the early adopters like this as we have seen from other subsidies that the incentive has to be very great before people will change.

AJH

[AJH]

On first looking it seems the measuring equipment is nearly as expensive as a small wind generator! If you have the space, and to my mind that means enough room for the wind generator and pole to fall over and not damage anything, I'd have thought just logging dc Volts across a resistive load (same as impedance as generator??) and amps would be simplest.

After that you have a complicated calculation to decide how the generated power fits in with your use. The best scenario I have seen, and I may have mistaken the meaning, is that you can export all your power to the grid via an "approved" inverter, buy back what you generate and use at no net cost, give away any surplus to your (one specific) electricity provider who also then collects and sells the ROCs on all your output and credits you these.

Having seen the goldplating necessary when you are obliged to use approved installers and equipment I'll bet a home grown solution requiring no direct grid interconnect will get a better return.

AJH

[Roger]

The message from Peter Parry contains these words:

They perhaps might. The Dti figures give the load factors for the years since 1998 and that year was the only year 30% was exceeded (30.7%) but as the load factor is calculated crudely by averaging the installed capacity at the beginning and end of each year it probably just means that the new capacity was installed on average later in the year than earlier.

Too true.

The governments own figures also suggest why B.Liar is now so keen on nuclear. The CO2 lifetime output for nuclear is marginally better than that for windpower, a range of 11-22 grams per kWh as opposed to 11-37.

[David Hansen]

On Fri, 13 Oct 2006 17:33:02 +0100 someone who may be AJH wrote this:-

It is more accurate to say they are complicated and site specific. The end result tends to be complaints from the antis that site specific information is not typical and averages are no use either. They then muddy the waters even further by claims that German wind conditions, geographical dispersal and the way the electrical system operates are similar to the UK.

Have you read the reports that I have referred people to? The answer to your point is in them.

[David Hansen]

On Mon, 16 Oct 2006 12:17:25 +0100 someone who may be AJH wrote this:-

Financial return? Depends on the circumstances, in particular whether one has an existing external supply. If one doesn't then a stand-alone system will usually be cheaper, but there are costs (financial and environmental) to storage batteries.

[David Hansen]

On Mon, 16 Oct 2006 12:30:59 +0100 someone who may be Roger wrote this:-

[Roger]

The message from David Hansen contains these words:

Dti