Rooftop wind turbines

[Nick Grant]

Microgen continues to be held up as a good thing and now B&Q are selling building mounted wind generators for £1500.

http://www.scoraigwind.com/citywinds/

Is worth a look.

A wind speed logger was attached to a roof in Edinburgh by Hugh Piggott and recorded under 2m/sec average:

“Thus, manufacturers who say you will get an average of 6 m/s on the roof at your site and this will generate 1,000 kWh/year from a 2-meter diameter wind turbine will overestimate production by 10 (ten) times! Those that say you can get 2,000 to 3,000 kWh on your roof top will overestimate your production by 20-30 times!”

Nick

[Anonymous]

It gets worse. The EST have just sponsored a B&Q leaflet targetted at DIYers including not only thse micro wind turbines but also solar thermal roof panels. This public funded promotion makes a complete nonesense of training intitiatives which are surley the only long-term, sustainble route to growth of renewable energy.

[Anonymous]

So if I'm reading the above correctly, a wind turbine would cost about half the cost of a professionally installed solar hot water heating system, but only produce a tenth of the energy each year, in an urban location. Not much to think about really!

Chris is quite right about the potential pitfalls of companies like B&Q getting involved in these markets. For example they sell a solar system which to quote, “includes a 90 litre unvented pre-heat store cylinder suitable for use with a combination boiler”. This is highly misleading as most combi boilers are not solar compatible and no further advice is provided on the web site. So how long before somebody buys one of these, hooks it up to their old combi boiler and has steam coming out of their taps!! Very dangerous.

Sorry to stray off the subject of wind turbines, maybe there should be a new strand about the likes of B&Q and Currys selling equipment, rather than buying from a company who can offer specialist advice and if required a professional installation, 5% VAT and a £400 grant.

[Anonymous]

So if I'm reading the above correctly, a wind turbine would cost about half the cost of a professionally installed solar hot water heating system, but only produce a tenth of the energy each year, in an urban location. Not much to think about really!

Not so simple. By the sounds of things we are comparing a badly sited wind turbine against a south facing solar thermal system. If we sited the same wind turbine where average wind speeds were not 2m/s (say 5m/s) and compared that against a north facing solar thermal panel the results would be the complete opposite.

Add to this the fact that on most occasions the wind turbine will be offsetting electricty as opposed to gas. This means that for every kWh generated by the turbine you will be saving approximatly three times as much financially and approx twice as much in terms of CO2.

The key is the siting of the turbine and it is here where we must be careful of the likes of B&Q as I doubt whether there are any warnings or advice on wind speed monitoring/siting etc before you make your purchase!

[Anonymous]

that was my point. No one sites a solar thermal system on a North facing roof and we should not be siting wind turbines where wind speeds are low/turbulence is high.

Not sure where you got you figures from regarding the cut out/in speeds but understand the confusion. Windsave themselves actually quote a cut in speed of 4 m/s and a cut out of 15m/s but B&Q say something completely different. The rated wind speeds these manufacturers quote are in fact just that, a speed at which they can be rated and compared, similar to the kWp used in the PV industry.

I also have seen figures like 80w average output which seems really pathetic. I assume this is after taking into account utilisation factors and efficiencies. However this would still save you around 700kWh a year (slightly more than a few low energy light bulbs) and this would be a analysing a badly sited turbine.

[Nick Grant]

Will be interesting to see how B&Q evaluate the average windspeed for a customer's rooftop given all the turbulence etc.

Tempted to order one just to observe the process.

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