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Small wind turbine useful in urban area ?
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CountingDown



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PostPosted: Wed Apr 29, 2009 8:41 pm    Post subject: Small wind turbine useful in urban area ? Reply with quote

IanG wrote:
If you look at the numbers in my table you'll see that the lows in november / december are near zero.

A bad week of heavy rain and you'll get next to nothing no matter how big the array is.

Frankly, you need an energy mix. I'm sure you'll get a near inverse of wind. Bit of PV, bit of wind and a small generator for use when the renewables isn't enough.

Sizing a PV array just for winter doesn't make sense to me.


OK, I know I'm setting myself up here . . but what are people's views on the usefulness of small wind turbines in an urban area?

My mother has a small wind turbine she's never put up, and she's giving it to us to do something with. I haven't got any details on it I'm afraid (will get those next week when I pick it up). I suspect it's just a B&Q one.

I had been thinking we might just hide it in the shed - but following this discussion, would it be worth putting up to give us a little something for winter?

Bring on the mockery . . . . . Very Happy

(this post has been moved from the solar forum as it is more relevant here, adam2)

(original context was in a discussion on how little electricity PV generates in winter, Andrew-l)
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adam2
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PostPosted: Thu Apr 30, 2009 8:57 am    Post subject: Reply with quote

Unless the area has high higher than normal wind speeds, the purchase and installation of a wind turbine in an urban area seldom makes economic sense.

However in this case, the turbine has already been received as a gift. If the owner cant sell it, or does not wish to, because it was a gift, then it could be argued that the capital cost is zero.

I would be inclined to install it and see what happens.

I believe that the B@Q wind turbines were grid tied, in which case it should come complete with the required grid tie inverter.
This will give a slight saving on your bill, but unfortunatly wont provide any standby supply in case of blackouts.

If on the other hand it is a battery charger wind turbine, then you will of course need a battery and probably also a charge controller.
The output of a battery charging turbine will probably be very limited in an urban area, it should be considered more of a disaster prep than as a means of reducing utility bills.
An average output of say 25 watts will have a negligable effect on your bill, but is enough for essiential lighting, which could be very valuable indeed in case of TEOTWAWKI.
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goslow



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PostPosted: Thu Apr 30, 2009 9:33 am    Post subject: Reply with quote

worthwhile if you're somewhere windy, simple as that. If you're not in a very windy area you might profit more by selling it on ebay to someone who is??
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CountingDown



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PostPosted: Thu Apr 30, 2009 9:37 am    Post subject: Reply with quote

We haven't moved into the house yet, so maybe when we do I'll keep an eye on the wind speeds for a while and see if it's worthwhile.

The question of payback is an interesting one, because as soon as it means that you have light where otherwise there'd be darkness I bet it'd feel like a great investment. Even if the numbers didn't back it up.
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Ted



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PostPosted: Thu Apr 30, 2009 9:52 am    Post subject: Reply with quote

If it is the B&Q Windsave model then be aware that in low wind sites it is possible that the inverter will consume more power than you generate. One of the reasons why B&Q stopped selling them.
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CountingDown



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PostPosted: Thu Apr 30, 2009 9:53 am    Post subject: Reply with quote

Thanks for the warning Ted!
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adam2
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PostPosted: Thu Apr 30, 2009 10:20 am    Post subject: Reply with quote

andrew-l wrote:

The question of payback is an interesting one, because as soon as it means that you have light where otherwise there'd be darkness I bet it'd feel like a great investment. Even if the numbers didn't back it up.


To have light when others dont would indeed be very worthwhile, but note that only a standalone battery charger wind turbine will give you lighting in a power cut.

A grid tied turbine wont produce anything without a grid connection, therefore is of no use in case of emergency.
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CountingDown



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PostPosted: Thu Apr 30, 2009 10:53 am    Post subject: Reply with quote

adam2 wrote:
andrew-l wrote:

The question of payback is an interesting one, because as soon as it means that you have light where otherwise there'd be darkness I bet it'd feel like a great investment. Even if the numbers didn't back it up.


To have light when others dont would indeed be very worthwhile, but note that only a standalone battery charger wind turbine will give you lighting in a power cut.

A grid tied turbine wont produce anything without a grid connection, therefore is of no use in case of emergency.


Ah yes, of course. So basically don't buy a small, grid-tied turbine for use in an urban area, expect maybe to give yourself a warm-and-fuzzy green feeling.

However one that fed into the same batteries as your Solar PV, with possibly any excess going to a 12v immersion coil, may be a worthwhile TEOTWAWKI winter solution - but not a great financial investment.
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adam2
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PostPosted: Thu Apr 30, 2009 11:07 am    Post subject: Reply with quote

andrew-l wrote:

Ah yes, of course. So basically don't buy a small, grid-tied turbine for use in an urban area, expect maybe to give yourself a warm-and-fuzzy green feeling.

However one that fed into the same batteries as your Solar PV, with possibly any excess going to a 12v immersion coil, may be a worthwhile TEOTWAWKI winter solution - but not a great financial investment.


Yes agree entirely.
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CountingDown



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PostPosted: Fri May 08, 2009 10:05 pm    Post subject: Reply with quote

OK, have got hold of the turbine - It's a Rutland 913, 12v version. No batteries, but that's ok, as we'll have some for our PV system that we should be able to feed in to.

Haven't read much about them yet - better get searching!

Anybody got any feedback on these? Are they worth bnothering about in a domestic setting?
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PostPosted: Fri May 22, 2009 2:49 pm    Post subject: Reply with quote

The rutland 913 is a good wind powered battery charger, even with below average wind it should easily produce enough for basic lighting.

In winter conditions in an urban area it should average at least 25 watts, and might be more.
25 watts may not sound much, but it is about 600 watt hours a day, which in winter would require a PV array of about 600 watts peak.

A Rutland 913 can produce as much as 300 watts, not very often in an urban area, but the charge controller and wiring must be suitable for this.

I would suggest a minimum battery size of 100 A/H, and several times that figure would be better.

I would consider installing one or two 12 volt lighting circuits to serve all main rooms in your home.

Two circuits, each rated at 10 amps, but with the actual load limited to about 5 amps would give basic lighting throughout a house.
Use of 5 watt CFLs in toilets and bathrooms, and 11 watt ones in main living areas, would give lighting levels less than normal mains lighting, but still much better than candles or most oil lamps.

There would not normally be enough energy for power tools, kettles or microwave ovens, but very limited use of such could be considered in windy weather.
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PostPosted: Fri May 22, 2009 3:14 pm    Post subject: Reply with quote

Thanks Adam - great response as always!

The small wind turbine's seem to be an interesting add-on to a PV system, and do benefit from being able to produce all day, even if only at a low level - they don't stop working at sunset!

I'll definitely have a good look at putting this up at our new place, probably will wait until we're getting the PV put in and do it at the same time.

On the 12v circuits, do you know if it's possible to do a non-destructive re-wiring of the existing lighting circuits? We've made the mistake of buying a house that doesn't need redecorating, so I think I'd not be very popular if I insisted we get it rewired for 12v and then had to get it redecorated as a result.

The last UK house we had had to be fully re-wired, which involved them gouging huge channels in the plaster to get to all the switches, and therefore had to be completely re-wallpapered.
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PostPosted: Sat May 23, 2009 11:24 am    Post subject: Reply with quote

An existing lighting circuit intended for 230/240 volts can be re-used for 12 volts.
Simply disconnect the cable from the existing mains consumer unit and re-connect to your 12 volt fuse box or to the charge controller, or to the battery, via a fuse.

Make very certain that the lighting circuit only supplies lights, and not other items.
Bell transformers, bathroom extract fans, boiler controls, and shaver sockets are often connected to lighting circuits, and cant be used on 12 volts DC

Remember that the load per lighting circuit should be limited to about 5 amps so as to avoid excessive voltage drop.
5 amps is only 60 watts at 12 volts.
Might be enough though, with careful planning.

For example, the downstairs lighting circuit might supply- living room two 11 watt lamps, wearedodgy two 11 watt lamps, dining room 11 watt lamp, hall 5 watt lamp, porch 5 watt lamp, downstairs toilet 5 watt.
Although that is 70 watts in total, it is unlikely that every lamp would be used at the same time.
This would provide ample lighting in power failures, but might not be considered sufficient normaly, it could be supplemented under normal conditions with table lamps etc worked from the grid via 13 amp sockets.

Another approach would be use an inverter to supply the lighting circuits, thus permitting use of standard 240 volt lamps, and any bell transformers, boiler controls, fans etc. that may connected to the lighting circuit.
It would be possible to have manuall or automatic changeover between grid and inverter power.
Use the wind turbine/inverter supply whenever the battery is nearly full, selecting grid power when the battery drops below say 75%.
This would ensure that maximum use of the wind power is made, but also that at least 75% of the battery capacity is available for blackouts.

Dependant on the load, amount of wind, and the battery size, this would give a few days unlimited use of lighting, and more restricted use indefinatly.
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CountingDown



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PostPosted: Sat May 23, 2009 10:26 pm    Post subject: Reply with quote

adam2 wrote:
An existing lighting circuit intended for 230/240 volts can be re-used for 12 volts.
Simply disconnect the cable from the existing mains consumer unit and re-connect to your 12 volt fuse box or to the charge controller, or to the battery, via a fuse.

That's Good news Adam - that should be an easy change. I had thought they might need thicker wiring.

adam2 wrote:

Make very certain that the lighting circuit only supplies lights, and not other items.

Is there an easy way to check? I guess I'll just ask whoever is doing our install, hopefully they'll know Laughing

adam2 wrote:

For example, the downstairs lighting circuit might supply- living room two 11 watt lamps, wearedodgy two 11 watt lamps, dining room 11 watt lamp, hall 5 watt lamp, porch 5 watt lamp, downstairs toilet 5 watt.
Although that is 70 watts in total, it is unlikely that every lamp would be used at the same time.
This would provide ample lighting in power failures, but might not be considered sufficient normaly, it could be supplemented under normal conditions with table lamps etc worked from the grid via 13 amp sockets.

*that* is an awesome idea. Minimal re-wiring required, Get to use the power is a useful, and everyday manner. Fantastic.

Thanks Adam
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adam2
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PostPosted: Sun May 24, 2009 10:47 am    Post subject: Reply with quote

12 volt lighting would normally require thicker cables than 240 volts, since for the same wattage the current would be 20 times greater.

However that does not mean, in practice that a 240 volt 5 amp lighting circuit will need to be replaced with 100 amps at 12 volts.

Remember that the 240 volt circuit should have been designed for 100 watt incandescent lamps, which we are proposing to replace with 5 watt, 7 watt, or 11 watt compact flourescents.

The minimum wire size permitted for domestic lighting circuits is 1.0mm, and 1.5mm is more common.
These are rated at about 10 amps and about 15 amps respectivly.
The load current should however be less than this in order to limit voltage drop, I would suggest a maximum load of 3 amps on 1.0mm and 5 amps on 1.5mm.
A greater current, up to the cable rating, would not be dangerous, but would result in excessive voltage drop and dimmer lamps.

Regulations require that the voltage drop in a circuit should not "prevent the proper functioning of the connected load" and the recomended figure for lighting circuits is 3%.
With a 12 volt supply, I believe that as much as 10% voltage drop would be acceptable (12 volts at battery, 10.8 volts at load)

If you find that the voltage drop in your wireing, when re-used at 12 volts is excessive, then consider installing an additional lighting circuit to whichever room has the greatest load.

In one home, I changed the existing lighting circuit from 240 volts, to 12 volts.
To limit the load and therefore the voltage drop, 5 watt lamps only were used in the living room and in the wearedodgy, one per room in the middle of the ceiling.
This provided ample light for safe movement and non critical tasks. Additional lighting for cooking, reading or fine work was provided by 12 volt 13 watt floursecent lamps over the wearedodgy work tops, and by wall bracket lamps in the living room, these being on an extra circuit.

Remember that in a future emergency it may be desirable to keep a low profile and not advertise that you have generous lighting.
For this reason it would be well to stock very low power lamps (1 watt or less.
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