by Carrie
Thu Feb 16th, 2006 at 06:30:55 AM EST
Back from the frontpage
original format restored ~ Migeru
There was a story in Sunday's breakfast about an Australian couple and how proud they were of their new wind (and solar) home power generating installation. It piqued my interest, and I ended up digging up this old news story, which I don't think has been diaried here before...
BBC: Generating interest in wind power (25 October 2005)
When Donnachadh McCarthy decided he wanted to generate his own electricity using a wind turbine, he almost fell at the first hurdle.
The planning application was initially refused after a neighbour objected - over what turned out to be an unnecessary concern.
...
A second amended application was finally given the go ahead soon after - making Southwark the first London borough to approve plans for a domestic model to be installed - and his neighbours seem more than happy.
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The turbine was installed on the gable wall of Mr McCarthy's terraced house in Peckham, south London, on Monday, and should generate up to 600 kilowatt hours every year.
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The turbine itself costs £1,000 but an inverter which turns the wind-generated electricity from DC to AC so that it can be used in the home costs a further £1,000.
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Mr McCarthy hopes more Londoners will follow suit and that looks likely with Mr Connor saying a recent survey showed that more than 12% of those living in the city would like their own wind turbine.
Before you think that the UK is about to erect a forest of domestic windmills, consider this:
Hidden Windpower: The problem with wind power
Love them or hate them, wind turbines have visual impact and it has to be conceded that more than half the population:
"Would object to the installation of a wind turbine in their immediate vicinity" ( 57% according to the TV Country File poll of Feb. 2004).
It has also to be recognised that local planners are elected to reflect, and act on, the opinions expressed by the majority of those they represent. It follows therefore that refusal is the likely outcome for any planning submission involving wind power and the current rejection rate of over 50% merely indicates that local planning authorities are carrying out their electoral obligations
In the UK there is even an association called
Country Guardian opposing wind farms on the following argument:
The Guardian:
Mini-turbine brings 'green power for all' (November 24, 2003)
Yesterday [a new domestic wind turbine design] was provisionally backed by Country Guardian, the lobby group which has opposed almost every planning application submitted for windpower development in Britain in the past decade.
"I think they are a good idea. I don't think they'll look very beautiful, but we always feel that it's the people in cities who use the power and that we in the country have to pay the price," said Ann Evans, a vice-president.
This is for the news and the sociology of urban wind. Below the fold I consider some of the technical details even (horrors!) daring to get quantitative. Feel free to skip to the comments.
The Guardian story I used to illustrate the rural NIMBY (Not In My Back Yard) problem includes the following:
Just two days after Britain's biggest offshore wind farm started generating electricity off the north Wales coast, the designers of the tiny domestic unit believe they can provide up to 15% of the annual electricity needs of an average house for a one-off cost of £750 - bringing green electricity into the price range of most families.
...
The system, says the Scottish inventor David Gordon, who has pumped £1m into the idea, can generate up to 750 watts - enough to power lights but not high-energy items such as kettles or heaters.
This is actually representative of the state of the art: a domestic wind generator can produce on the order of 1 KW and costs about £1000.
[By 'on the order of' I mean that I am happy if '1' stands for anything between .3 and 3]
So, how must wind power can you hope to produce at home in an urban environment, and is it worth it? If I owned the house where I live, I reckon I could produce up to 1000 KWh per year, which covers about 50% of my household's electricity consumption, and hence save up to about £100 a year in electricity.
How much wind power you can obtain from your house depends on the area that your house (and lot, if you have it) covers. For example, my flat (in a 2-storey terraced house) is about 80 m^2, and the house has a yard of maybe 50 m^2, for a total of 130 m^2. If I add the front yard and 1/2 of the area of the street up to the middle of the road, the total area available for my hypothetical wind turbine(s) to catch comes to maybe 160 m^2. How much power can I extract from it?
The Danish Wind Industry Association has a fantabulous guided tour containing the following diagram (used without permission) illustrating what is considered to be the optimal separation between wind turbines in a wind farm:
The '4' and '7' are in units of rotor diameter, with the longer distance in the direction of prevailing winds. This is relevant because, if every house is going to have its own wind turbines, you have to consider your own turbine as part of a farm, and you cannot encroach on your neighbours' wind. The area corresponding to each turbine is then approximately 21 times the square of the rotor diameter. The assumption that the city is saturated is my justification for including 1/2 of the area of the street in front of my house as part of my 'catchment', by the way.
My 160 m^2 of catchment area then translate into d^2 = 7.6 m^2. That is, I could think of installing one turbine with a rotor diameter of 2.8m, or two turbines of 2m diameter, or 3 of 1.6m... you get the idea (in all three cases the total area swept by the rotors is the same).
According to a recent report of the Mid Wales Energy Agency, Domestic Roof-Mounted Wind Turbines - The Current State of the Art (PDF), which I found through the British Wind Energy Association's I want my own turbine page, there is a 2m turbine with a nominal power of 1500 W, and a 1.75m turbine with a nominal power of 1000 W, so it seems that I could hope to get 3 KW (nominal) out of my 160 m^2 catchment. However, KW range wind turbines are usually rated at their maximum power, which is by design obtained at wind speeds of 10 to 12 m/s, while typical speeds in an urban setting about 10m above the roof are typically 5 m/s. Small turbines usually produce power starting at 3 m/s (a lower cut-off than large, MW-range turbines), and power scales with the 3rd power of wind speed, so the Welsh report estimates an average output of barely 200 W for the 1500 W turbine. That is, 400 W for my possible two-turbine configuration. This is still enough to produce about 3500 KWh in a year, which might just cover the electricity costs for us and our downstairs neighbours.
Assuming I don't get planning permission for two 2m rotors on 10m poles, it seems I could still aim for 1 W per square meter with smaller turbines, and that's still good for 1400 Kwh in a year.
The cost of a KW-range turbine seems to be about £1 per 1W nominal power, that is, in the hundreds or low thousands of pounds for a typical home installation. Considering the expected life of the turbines is 10 to 20 years with little maintenance, and the current (and, as we know, likely to escalate) retail electricity prices, it seems like residential wind power is beginning to make financial sense, even in urban environments.
I note that, in places where the typical appartment building is higher than 2 storeys, the amount of power that can be produced begins to be insufficient. This would clearly the case for a typical 7-storey block of flats in mainland Europe. However, such a block might be able to get larger and taller turbines installed, for higher power output.
