Sunday Times : "Urban greens struggle with windy dream"

[Peter Parry]

Unfortunately that check is being carried out by the sellers using a calculator which is wildly inaccurate for over 80% of the population in the UK.

[The Natural Philosopher]

No, but thats what wind turbines produce.

So they won't help me reduce my massive fuel bill much will they?

Yawn. Son, I am way ahead of you.

Done just about every sort of calculation possible on energy use for this house..it was my own design.

Anything a wind turbine could do is utterly and completely trivial compared with half a dozen other things I could do at far less expense.

Like a new chainsaw blade. That will save me a few hundred this winter..I have a couple of blown over trees to be cut up ...

>

[David Hansen]

On Mon, 13 Nov 2006 10:40:09 +0000 someone who may be The Natural Philosopher wrote this:-

So, your calculation didn't tell us anything particularly useful then.

Indeed.

Not your bill for heating. As you admitted above, you don't heat the house by electricity. However, it will reduce your bill for electricity and it will make a contribution to reducing greenhouse gases.

In note that you were unwilling or unable to counter the point I made.

That doesn't surprise me in the least, which is why groups like Friends of the Earth recommend doing other things first and only going for a wind turbine after doing those other things. This isn't a change in direction on their part either, they have always spoken about reducing consumption first.

[David Hansen]

On Mon, 13 Nov 2006 10:37:59 +0000 someone who may be Peter Parry wrote this:-

The limitations of the model are well known, not the least because they are stated by the modellers. I would be delighted if a better model was available, perhaps just of the larger built up areas, though I can hear the whining from some if this was funded.

In the meantime when people ask me about such a turbine I put it in the context of other things and advise a small weather station, which I have mentioned here before, as a means of determining the likely output.

[Peter Parry]

They are not known to the poor sods being conned into buying this rubbish.

They are available, it just that few in the UK seem to want to use them. The Wind Atlas Analysis and Application Program (WAsP) shares the same design characteristic of NOAB in that it copes best with low, smooth hills of small to moderate dimensions. However, unlike NOAB it includes compensation for surface roughness. It is by no means perfect but it is more accurate than NOABL in urban environments.

The Danes have used it to map urban areas in Denmark in some detail taking local terrain and roughness into account. As I have said before the results can be downloaded from their web site in standard map overlay form for anyone to use. The overview map is at

perhaps just of the larger built up areas,

What is to fund? If you are really that interested in objective analysis as opposed to greenwash pop down to Edinburgh University Institute of Energy Systems, they have had a copy of WaSP there for over 5 years. Wind Prospect in Castle Street are also users.

However, you can easily add surface roughness calculations to NOABL data and the Danes have provided a (free) calculator to do this at

this it is easy to correct the NOABL figure to take into account surface roughness, although this still leaves the basic accuracy of the wind measurement as an uncorrectable factor. As I am sure you know only 22 measuring points in the UK and 200 over all of Europe are used as the basis for all these models.

Published work on urban wind generation include :-

(The Ealing Urban Wind Study from the Centre for Sustainable Energy) At a mast height of 35m they found a predicted average wind speed of

4.4m/s and calculated a wind generator at this height would be motionless for 21% of the time [no real measurements were taken in this study]. The major revenue was calculated to come from subsidies in the form of ROC's and LEC's. The payback period exceeded 50 years. "As is typical of urban areas, average wind speed at the proposed site is significantly lower than that normally encountered in rural, less built-up areas, where turbines are usually sited. Energy production and turbine load factor will therefore also be low."

(ESRC Working Paper Number 2006/1 Economic Analysis of Micro-generation Deployment Models) "The corrected average wind speed for the urban environment varies between 2.66 m/s and 4.09 m/s. Annual electricity generation is therefore quite different. In our modeling a 1 kW device (under optimistic assumptions) will hardly achieve an annual electricity output of more than 1,000 kWh (site: Aberdeen) and can be as low as

100 kWh (site: Coombe 2)" [if a wind generator cannot reach the subsidy level (ROC) of 500kWh/yr] it would take more than 60 years to payback. Our data sample suggests that most of the micro wind output is consumed on-site. This is contrast to previous studies that assumed that 60% of micro wind output will be exported to the grid (Energy Saving Trust, Econnect et al., 2005)23."...

"The modelling results used in this paper suggest that payback times for micro wind turbine installations are greater than manufacturers? estimates."

John Shore of Resource Research ?The public have a right to know that most of the media hype surrounding this subject is based on wishful thinking and not on realism. The situation has been made worse by two or three companies who hope to exploit the issue of climate change by making unrealistic performance claims for their products. Wind turbines are very useful green electrical generators, when placed on windy sites at least 10 metres above any obstruction within 150 metres. A 1 kW turbine with a blade diameter of at least 2.5 metres can produce over 3000 kWh/year in a windy field, but will struggle to reach 700 kWh/year on a roof-top. My personal experience of roof-top wind turbines are that they very rarely make a serious contribution to the energy needs of a dwelling, especially in urban areas. Very few of my customers who have mounted turbines onto buildings have been pleased with the power output.?

[Steven Briggs]

In message , Peter Parry writes

Can I thank you Peter for your excellent evidence & fact based contributions to these threads ;-)

Incidentally, the figure mentioned above for the "Combe 2" site mirrors the calculation I did from my own weather station data. 100kWh gross,

50kWh net over a year (1kW turbine). Still better than the poor chap in the Sunday Times article that made 10p in two months!

[Steven Briggs]

Another thing that is misleading is the use of the Rayleigh Curve or Weibull distribution for average windspeed.

Intuitively its wrong, _no_ periods of zero wind? Come on! While it doubtless applies at typical, wind rich, commercial sites, for domestic situations its way off the mark, as shown from my own data.

Wind Av Equivalent DAYS mph per year

0 55.2 1 41.4 2 39.7 3 39.4 4 38.6 5 37.5 6 30.1 7 23.1 8 17.7 9 12.7 10 9.9 11 6.9 12 4.1 13 3.0 14 2.1 15 1.3 16 0.9 17 0.5 18 0.3 19 0.1 20 0.1

This is an analysis of the whole of 2005, recorded average wind speed in

10 minute intervals. Collected by a Davis Vantage Pro anemometer, mounted 8 feet above the end of the roof ridge of my bungalow in the middle of Yorkshire.

Intrigued by the energy that may be available in gusts, on a moderately windy day I observed the weather station readings for 10 minutes, noting every 2.5 second sample of wind speed.

Instant. Wind No. of mph samples

0 1 1 1 2 5 3 19 4 8 5 19 6 34 7 23 8 14 9 10 10 23 11 16 12 23 13 12 14 9 15 1 16 4 17 3 18 9 19 3 20 4 21 2 22 1 23 0 24 0 25 1 26 1 27 0

Average for that period recorded as 9mph, peak 26mph Now that is more or less Wiebull shaped, although there are sampling/conversion anomalies in the data.

Now before I get labelled as an "anti" again, let me say in a (much) more exposed site I would be watching the technology very closely. But not for this semi-rural site!

Someone I know, about 8 miles away, until recently used a wind turbine for a fair portion of his electricity. He has a good site, on sloping ground exposed to the west, house built on somewhat of a mound, 30-40' lattice tower in the back yard. Wind and an occasional diesel genny provided all his electric, but he had to be very frugal, gas fridge, solid fuel cooking/HW/heating, 12V portable telly etc. Old age has now forced him to finally have a grid connection for a few of life's comforts.

[David Hansen]

On Tue, 14 Nov 2006 17:12:01 +0000 someone who may be Peter Parry wrote this:-

"Poor sods" are "conned" into buying all sorts of "rubbish". Why single out wind turbines and moan about the fact that not everyone thoroughly researches every purchase?

Those that do research before purchasing something find out that leaflets can only show a subset of the available information on that something.

"Available" was a bad choice of word, "in use" would have been better.

[The Natural Philosopher]

We don't. Here we also herald the deficiencies of Saniflos, inappropiate Combi boilers, Toyota Pious' and electrical underfloor heating, not to mention flexible baths, and chipboard walls.

Indeed. Perhaps you should listen carefully to what you just said...

[David Hansen]

On Wed, 15 Nov 2006 09:06:46 +0000 someone who may be The Natural Philosopher wrote this:-

[The Natural Philosopher]

leaflet covers a broad definition..including learned papers produced by people who have missed some fundamental points.

Nature doesn't get a decimal point moved for example, Scientists can.

If you want to save energy on towns, roof them over. Preferably with something opaque so that they don't spray light into the night sky.

[Andy Hall]

Because it's an expensive purchase and the purveyors are being economical with the truth. That's being kind about it.

[Dave Plowman (News)]

It's rather different price wise from an Ideal Homes gadget. It also intrudes on the environment.

[Peter Parry]

I'm pleased that at last you agree that the majority of people who buy these silly things are being conned into buying rubbish. One could just sit back and chuckle at their stupidity but it is a particularly dishonest piece of hype they are being peddled and that dishonesty is supported and promoted by the various greenwash groups propaganda where "exposure" is more important than effect.

I noticed today a particularly amusing seller who is offering :-

"If you buy your turbine from B&Q via the links on this webpage we will give you a free £25 Ecoflow voucher which you can put towards a Thermoflow for reducing the cost of gas or oil in central heating systems,a Motoflow for reducing petrol consumption in vehicles or an H2Flow for reducing the effects of limescale in hard water areas"

Two useless devices for more than the price of one? I do agree that anyone falling for that offer would have to be particularly moronic but it is indicative of the dross found on the green sales wagon. Have you seen a single utterance from the likes of Greenpeace of FOE saying these devices are being sold dishonestly or attempting to give objective, factual help to prospective purchasers most of whom will live in urban areas? Of course you won't, they want them on roofs as "green statements", to dishonestly alter opinion rather than generate electricity.

Your own organisation, FOE, state :- "Costs and grants: From around £1,500 for a small rooftop system (which would power a TV, DVD player, computer, fridge, freezer and several lights) to between £4,000 and £18,000 for fully-installed systems to meet the needs of a household or community building."

Those claims are completely unsustainable for 90% of the UK.

Those that try would probably go to places like the FOE - to be misled. Or they might find sites like the Green Company where they would be told :-

"Do wind turbines make financial sense? Yes. A well installed high quality turbine has an operational life of 25 years. As a rough rull of thumb in the UK, a 1kw turbine will generate £200-£450 of electricity a year - paying back your investment in 3-7 years."

This is complete nonsense.

Or they might try yes2wind "This site was produced by Friends of the Earth, Greenpeace and WWF, with the aim of providing information and resources for the public ..." where they will misleadingly be told:-

"Could I put a turbine in my garden or on the roof of my house?

Yes you could! In the future, as both solar and Combined Heat and Power systems develop, we will have far more smaller generating units throughout our towns and cities, as well as in rural areas. Renewable power won't just be coming from large wind farms but also many small wind turbines as well. We can all become mini power stations - it's already possible to sell electricity you generate from renewables on your land or home back to the national grid through net metering. "

The Energy Saving Trust are even more misleading :-

"Knowledge of the local wind resource is critical to designing a wind energy system and predicting output. For domestic installations a good source of information on local wind speeds is the NOABL database..."

"As a rough guide, a good wind site will produce an average output of

30 per cent of the rated capacity of the turbine. The size of the wind turbine determines the total amount of energy generated each year. For example, if a 5kW wind turbine generates the equivalent to rated power for 30 per cent of the year, it will generate 5 x 0.3 x 8,760 (24 hours x 365 days) = 13,140kWh per year."

There isn't an urban site anywhere in the UK where anything other than a tiny fraction of that will be produced.

There is a difference between a subset and being deliberately misleading. To say the average wind speed in the UK is 5.6m/s isn't specifically a lie - but it is about as meaningful as saying the average voltage between the UK and USA is 170V.

Where exactly is the poor punter supposed to go to do their research and find unbiased advice?

So why do people like FOE not use the better models? Why don't they give practical objective advice on how to use the DTI data in a sensible way? Might it be because it would show the "wrong" results and display the emperors new clothes for exactly what they are?

[AJH]

The quoted numbers above is interesting and I'd hoped someone with a grasp of statistics would comment. For myself I can only see a method to indicate the likely utility of power generated under your conditions if I can work out the instantaneous energy available in the wind, so your ten minute samples would be good for this, about 52000 entries?

I'm more interested in seeing how closely I can match wind generated electricity with my own use and minimal reliance on batteries or grid supply rather than an exercise in exploiting subsidies.

AJH

[Andy Hall]

.. and you're willing to invest £1500 in doing so??

Let me send you my Paypal account details. I have a great opportunity for you.

[The Natural Philosopher]

I would say the short answer is you would be far better off with photovoltaic cells.

I fly model planes, and just about any hour of the day, I am fairly aware of the wind speed. Its usually around 7-12mph, and anywhere near the ground, extremely variable. Especially at dawn and dusk, where there is a boundary layer up to about 50 feet then a smooth transition to proper wind at 1-200ft.

winds in excess of 10 mph at anything near the ground are extremely rare..thats the sort of day when you notice it is 'quite windy'..and the days when its over 30mph are probably less than 10 a year.

That's is out in the country. In town its even calmer.

I don't say that someone up on a high moor with no trees around can't make a go of it, but not the rest of us.

[AJH]

I don't expect people to remember an occasional poster's comments but this is essentially my view, previously expressed, also. I also am optimistic about the contribution solar thermal and PV might make as fuel prices rise. In the meanwhile I do make cost effective use of renewable energy for heating.

I can see from Steven B's posted figures that 55 days equivalent without wind annually is difficult to reconcile with power on demand but I am not clever enough to make a judgement on the data as presented and I would like to see the full dataset to give an idea of the time constant involved.

I've seen how "incentives" to produce electricity have skewed the renewable energy market so I want to look at things fundamentally, I don't accept the biased views of a certain globetrotting, perennially unhelpful, poster should influence such an enquiry.

AJH

[The Natural Philosopher]

I think if I went away from oil/electric here, I'd probably lay out solar panels, and maybe a small mill on a tower, and try and set up a heat pump to freeze the garden and heat the house.

I wouldn't expect to replace it, but bill reduction is always good. The houseis large and te requirements for airchanges make an upper limit to what insulation is worth applying..a heat exchanger would help..

[David Hansen]

On Wed, 15 Nov 2006 23:01:17 +0000 someone who may be AJH wrote this:-

I think one needs to differentiate between the two. Solar thermal is now on the verge of becoming mainstream. OTOH PV is still something for those who wish to encourage the market. Given some years PV will also move to the mainstream, but it isn't there yet.

A 1kW panel, made from 50 x 20W panels would cost £3750 and cover an area of about 6m x 2.5m with fixings.

's just the panels, a figure of £6000 per kW is given for the array at installed.

By contrast a 1kW wind turbine is £725

to the £3750 and £725 figures one would need to add an inverter and mounting.

The amount of electricity one would get out of each depends on where it is installed. PV works better in southern England, wind varies around the UK.

In the UK PV is not well matched to maximum demand, which tends to occur in winter after dark. Wind output is generally higher at times of maximum demand.

The large scale incentives are engineering neutral. Obviously this means that operators have chosen the most mature engineering, onshore wind (together with some work on hydro). However, one can also argue that wind demonstrates that renewables work and this encourages investment in other forms of renewables.

The small scale incentives are largely engineering neutral. The big exception is that there is a much higher grant for PV, in order to encourage the market.