I see in the press that the BRE trust are saying that the majority of roof mounted wind turbines are going to produce less energy in their lifetime than it took to manufacture and install them. Why are manufacturers not obliged to state on their products the energy used to manufacture them. It is absurd that people are being tricked into thinking they are saving energy when they are simply wasting it.

I have not found data to say energy efficient light bulbs do either?

It may be true,
but how does the renewable energy created over life span( with embodied energy included) compare to the other option of the
national grid and its 40% network loss and the carbon heavy ( 0.5kg/Kw ? ) generation of electricty when it come to total carbon produced
for either of the 2 options.

I've no idea, but isnt this the important point/consideration

Theres certainly lots of miss selling on the under the green banner
I've heard said elsewhere we should be bring these things up with trading standard, advertising standards etc.
Jo public getting stitched as usual, a friend of mine was quote £8000 for a basic solar HW by a firm
I imagine the companys well know here though, I dont want to break forum rules

The national grid may be inefficient, but the power stations on the end of it are an order of magnitude more efficient than virtually any domestic sized electricity generation system. That's why we have the national grid in the first place, instead of local 'pumping stations'

Some companies even install turbines on the side of houses, below the roof ridge. Given that such turbines won't produce any power unless the wind speed is over 5m/s, and that the inverter consumes about 10W just sitting there waiting for the wind that will never come, the net contribution to the national grid is approximately -10W.

Data on actual rooftop installations is trivial to provide, and would, if positive, be an excellent marketing tool.

Small domestic roof mounted wind turbines in urban locations are generally a waste of money. Financial payback within the turbine's life is unlikely and the carbon savings vary from modest to non-existent.

There may be rural locations where smallish wind turbines make sense, but they should not be installed willy nilly across the country in urban locations as some form of middle class environmental one-upmanship.

It's not rocket science, it's simple physics and economies of scale, large turbines in windy locations work well, anything else is a compromise.

On a related note, the Government requiring that we generate electricity on site to qualify as a zero carbon home to qualify for the Code for Sustainable Homes code level 6 and zero stamp duty is simply counter productive and encourages the installation of wind turbines in inappropriate locations.

Unless any of you are generating electricity yourselves then you will not know that 'offgrid' is by far the best way of reducing your consumption. It is a fundamental point of self sufficiency that you understand what your limitations are - technologically or physically then work within them.

By continuing to embrace distributed power we just become ever more 'fuel obese' because we do not bother understanding the real price behind the product. By going the grid way and using blinkered logic of payback and carbon counting, are we not just feeding ourselves slowly but inevitably to the nucleur boys.

and the square of the swept diameter.

>feeding ourselves slowly but inevitably to the nucleur boys.
That'll be the French spelling then?
In case there's still anyone lurking around here who thinks there is a future in the nuclear, David Fleming has just published The Lean Guide to Nuclear Power, available as a free download or in print for a fiver:

http://www.theleaneconomyconnection.net/downloads.html#Nuclear

"The most telling argument for nuclear power is that, if it can be a major source of energy which does not
contribute to climate change, it is worth putting up with the pollution, waste and risk. In this careful and very readable analysis, David Fleming demolishes that argument."
~ Edward Goldsmith, Founder, The Ecologist Magazine


"Here we have the final proof that nuclear power generation is a dangerous cul-de-sac and that
investment should instead be directed to renewable energy. Nobody who is concerned about our future
supplies of energy should fail to read it."
~ James Skinner, New Economics Foundation

Another excellent method of reducing your electric consumption is to purchase a whole house energy monitor. When you see what is wasting away it is quite frightening. I believe that from next year you will be able to request these from your energy supplier.

Ted,

Lift = ro.g.Cl.V^2.A
Wind speed, V, does vary according to altitude (as does the direction) but the biggest difference is over the first 20m or so, the difference is more noticeable over rough terrain, e.g. houses, woods, than open terrain e.g. moorland, water, this is known as wind shear
A= Diameter.chord length
Chord length is usually proportional to diameter so A=%.D^2

Bowman

Bowman,

Power of the Wind Formula: P = 1/2 rho v3 Pi r2

Where P = the power of the wind measured in W (Watts)
rho = the density of dry air measured in kg/m 3 (kilogrammes per cubic metre, = 1.225 at average atmospheric pressure at sea level at 15° C)
v = the velocity of the wind measured in m/s (metres per second)
Pi = 3.14159...
r = the radius (i.e. half the diameter) of the rotor measured in m (metres)

So there is eight times more power when wind speed doubles and, conversely, one eighth the power when wind speed halves.

For example, at 12 m/s there is 1kW of energy in the wind for every square meter of swept area.
At 6 m/s this drops to only 130W and at 2 m/s (typical rooftop wind speeds) it is only 5W.

Due to the Betz limit a wind turbine can generate a maximum of less than 3W for every square meter of swept area at a wind speed of 2m/s.

Allow for electrical losses and the figures become vanishingly small.

Of course a simple average wind speed figure does not tell the whole story, but even using the accepted Weibull power distribution it is clear that rooftop mounted wind turbines are a waste of resources.

The difference between large and small turbines is the scale of the subsidy. According to The Economist (March 2004) "Wind farms get around three times as much in subsidy - a mixture of selling ROCS [renewable obligation certificates] and a share of fines paid by non-renewable plants - as they do from selling electricity". Also from The Department of Trade and Industry: Renewable Energy, Sixth Report 2005-6 "The Renewables Obligation will cost consumers £1 billion per annum by 2010 rising to £1.5 billion per annum by 2015." So, we're all paying for wind energy already, and will continue to pay more.

If "big wind" is so good, why does Denmark, with the highest percentage of wind power in the world, have the highest CO2 per capita emissions of the EU 15? I'll give you a clue: Sweden has the lowest CO2 per capita, and France the second lowest.

tom.harrigan did you read the biff link 9 or 10 above
http://www.theleaneconomyconnection.net/downloads.html#Nuclear
Just wondered how you stand with it
tom

Put Howdytom and GBP Keith together without delay then our Fuel Obese population (wonderful image the phrase conjures) will be shamed into producing fewer humans. Bingo! a slim appropriately sized future population. Apprpriate to what?

Sorry niggle, I've no idea how big Mike is, but i'm no slimline

tom.harrigan,
so what do the french do with their 200,000 tonnes of high level waste(in storage and obviously rising) ? send it to the uk for processing ?