Homes and Wind Turbines

So how many “homes” does a wind turbine power?

We all know that there are lies, damn lies and statistics. But there is also lies, greed and manipulation of the truth.

Say you want to desecrate a large area of rural England with wind turbines the height of Salisbury cathedral. You know that these turbines are only viable because of the massive subsidy you get. You know they produce next to nothing in the way of useful electricity. But you need to con the gullible, the wishful thinkers and the Luddites into supporting your ruthless avarice. What do you do?

You make it look homely, warm, benign even.

You describe the output in terms of how many “homes” your monstrosities will power.

But of course, you are, as ever, economical with the truth. Especially when it comes to using simplification to airbrush out the real truth of the matter.

Take this site which offers lots and lots of propaganda for a proposed four turbine complex deep in rural Purbeck. They state their turbines are rated at 2.3 MW. That is 9.2MW in total.

Sounds impressive.

To be fair, they realise that no one is conned by these maximum rating figures.

So when they calculate the number of “homes” they can provide for, they appear to use the pathetic average of one quarter of the boiler-plate rating. In other words each turbines real rating is an average of 0.575 MW. But they do not display this figure. It is after all derisory.

If they then take the average household consumption of electricity as the figure given here   they can offer up that their assertion that this four turbine carbuncle on the face of Purbeck will fuel 5000 homes.

Sounds good. 5000 homes Hmm-mm. Wholesome.

But there is a problem. In fact there are two problems.

The first problem is that while the average output of these things really will be about 0.575MW each and the average requirement for a household really is about 600W, the figure blatantly avoids the demographics of household electricity use.

Households use their energy mainly in well defined time bands. For example their use at 3am is small yet in the early afternoon is at least a couple of kilowatts.

(graph from mpoweruk.com )

Simply put, the average turbine energy output is inadequate at times of peak demand (by at least a factor of four) and at other times the power they produce is unneeded and wasted. These four turbines are not capable of meeting anywhere near the day to day demands of 5000 homes.

But it gets worse.

Wind turbines are governed by the vagaries of the wind and the wind is governed by the certainties of Physics. The power of the wind is proportional to the cube of the wind speed. The harder it blows the more energy there is in the wind.

The result of this is that half of the energy in the wind is delivered to the wind turbine in just 15% of the time.

So half of their annual power output will arrive in a total period of less than 60 days. So not only are they intermittent they are also peaky. There will be times when they are maxing out and demand is low

(graph - http://en.wikipedia.org/wiki/Wind_power Note the graph is the total wind energy and frequency of occurrence at different wind speeds. The throughput is calculated through an imaginary 100 meter disk. Energy data recorded 2002 Lee Ranch facility USA)

If you take out this brief peak period and concentrate on their output over the majority of the year, we find that the 300 day average output of these things falls to:

365/300 * 0.575/2 = 0.35 MW per turbine.

That is 1.4MW for the whole 4 turbine farm.

So most of the time they can provide only an average “home” load for 2300 homes.

But do not forget that is the averaged household demand NOT the day to day demand which is itself peaky though predictable. During many defined periods of the day the average homes will use 2+ KW.

During these times these things, on average over the 300 days, then can only provide for about 600 "homes".

The ability of wind turbines to provide reliable energy for “homes” is overstated, deceptive and fuelled by massive amount of wishful thinking.

I often use the old now redundant small nuclear station up the road from me in Winfrith as a comparison for Wind Energy.

This old nuclear station regularly and routinely provided 62MW to the national Grid. No peaking, no troughs, It never stopped because of the weather.

If you do the maths in the same way the wind industry does, ( i.e. “homes”), this old reliable nuclear reactor provided power for well over one hundred thousand “homes”.


Of course the other big con in all this "homes" nonsense is that household electricity is only 30% of the total demand. The rest is split across industry and services.

So why are we building these useless wind farms? Why are we desecrating our country-side?

Unless you are getting the subsidies, the reasons appear unclear.