Wind spinners/ mini turbines?

[Moira Niedzwiecka]

I am just starting to think about the garden at the new house.

I quite like some of the wind sculptures/spinners that are about.

It occurred to me that they generate a lot of energy when it is breezy, like mini turbines or a dynamo.

I am really dim at this stuff but would it be possible to harness some of that energy to use in the garden, eg for a water feature or pond pump, or garden lighting?

I

[Temp]

I guess that would be possible but they will be a less efficient than a regular wind turbine of similar size.

 

There may also be a planning issue.

 

 

[SteamyTea]

1 hour ago, Moira Niedzwiecka said:

It occurred to me that they generate a lot of energy when it is breezy, like mini turbines or a dynamo.

They just don't.

It is all to do with the area they present to the wind and the windspeed.

 

[Moira Niedzwiecka]

48 minutes ago, Temp said:

There may also be a planning issue

I doubt it, these are just garden ornaments.

My garden is quite elevated & gets a bit blowy.

I just wondered if the energy from a group of 3 wind sculptures could be harnessed in anyway to power a small water feature.

[PeterW]

Yes probably as you only need a few watts of power. 

 

Transferring the rotary power to a generator may be the issue though so daft as it sounds a purely mechanical way may be easier such as the way the old wind pumps used to work. 

[Jeremy Harris]

19 minutes ago, Moira Niedzwiecka said:

I doubt it, these are just garden ornaments.

My garden is quite elevated & gets a bit blowy.

I just wondered if the energy from a group of 3 wind sculptures could be harnessed in anyway to power a small water feature.

 

 

Possibly, it depends on how large they are, how much wind there is and how much power the water pump needs.  I've been looking at using a small solar panel to power a pump for a small water feature.  I want to be able to pump around 10 litres per minute  (about  the flow rate of a shower) to a head of about 0.2 to 0.3m to create a small artificial stream.  The power needed to move that much water is between about 0.32 W and 0.5 W, and allowing for the efficiency of the water pump it looks as if I'd need between about 1 W to 1.5 W of electrical power from a solar panel.  This is surprisingly little, I had to double check the sums to make sure I'd got them right.  I can now see how the small solar pond fountains work as well as they do; they just don't need very much power at all.

 

If your wind sculptures had a swept area (the area exposed to the wind) of, say, 1m², then with a wind speed of just under 5mph the theoretical power available would be around 4.92 W, but allowing for the efficiency of the generator the electrical power output would probably only be around 2 W, but even so it seems quite possible to use a fairly large wind sculpture to drive a water feature.  Doing as @PeterW suggests, and making the drive purely mechanical, would probably improve things slightly.

 

 

[joe90]

I looked into a Wild West type of wind driven pump when considering using well water for my site, simple diaphragm pump to create a head of water.

[Temp]

4 hours ago, Moira Niedzwiecka said:

I doubt it, these are just garden ornaments.

 

 

When you connect them to a generator or pump they become a wind turbine :-) The ones in your original picture don't look that different to this type of vertical axis wind turbine. Smaller ones are sometimes used on boats.

 

 

[Temp]

Summary of planning rules here..

https://www.thegreenage.co.uk/tech/planning-permission-for-wind-turbines/

 

[joe90]

• Must comply to the MCS planning standards

i wonder what that means, it also says must be removed if no longer used fir micro generation (I guess they mean grid connected) as we are talking about non grid tied. So I guess MCS standards are not applicable.

Edited August 10, 2019 by joe90

[Temp]

As understand it the government is concerned that old non working turbines might be abandoned as has happened in the USA. So planning grants normally have a planning condition requiring removal if it doesn't generate for six months. There is probably something similar in the PDR rules.

[MikeSharp01]

19 hours ago, Moira Niedzwiecka said:

 

We saw these in UTAH earlier in the year and purchased one, can't imagine it will generate much electricity but it does generate a lot of interest

[Ed Davies]

12 hours ago, joe90 said:

it also says must be removed if no longer used fir micro generation (I guess they mean grid connected)

 

No, the permitted development rules don't care if it's grid connected or not. They just need it to be removed if it's no longer used, presumably for the reasons @Temp mentions.

[SteamyTea]

The very first commercial wind turbine was installed down here, between Falmouth and Helston at Sewogan.

It sat unused for decades, but I think it has gone now.  Was pretty ugly.

[Triassic]

We live on a ridge line and it’s fairly windy, I’ve often wondered about a wind turbine, what would people recommend?  It would be a Diy installation. 

[Ed Davies]

I'm not convinced there is a good solution in the small wind turbine area. AFAICS, none are well engineered to withstand windy sites or work well on sheltered sites. My site is about as good as it gets for wind [¹] other than bits of the west coast of Scotland but I'm not planning a turbine for my off-grid house until I've experienced a winter or two in it to see how necessary/useful one would be.

 

If you're grid connected small turbines are, IMHO, pointless. Even off grid it's not obvious whether just adding more PV is more cost effective. Obviously long runs of dull weather in winter are difficult but even still…

 

[¹] 100 metre high hill top overlooking the Moray Firth with about a hectare of land available to site the turbine, no trees of any significance around and no other occupied properties within 100 metres so would be permitted development.

[Cpd]

36 minutes ago, Triassic said:

We live on a ridge line and it’s fairly windy, I’ve often wondered about a wind turbine, what would people recommend?  It would be a Diy installation. 

Living on the west coast of Scotland in a wind tunnel i am also in a prime location, lack of funds at the moment but wind powered energy is my end game even if it’s just for fun....  in the research to date I have found that the smaller turbines just don’t cut it and large ones require serious service and my location makes that a non starter.... so one day I would like a small turbine to power some heating and LED lighting in a poly tunnel to extend the growing season........ as I said it would be fun !

[Ed Davies]

My assumption, above, was that you're talking about a small turbine up to around 1 kW or a bit larger. If you mean something bigger then a 2.4/3.2 kW Proven/Kingspan turbine seems like the answer but that's quite a big bit of engineering to DIY. Multiple cubes of concrete for the base, for example.

[SteamyTea]

If you are making a WT for fun, it need not be expensive, or that efficient.

When I worked for a small turbine manufacturer, I suggested that they just made the tower and generator. Let others make the 'sexy' bladed. People seem to think that is where they can improve over Betz, so let them learn.

I still think that the idea has some legs, but it does require a stringent understanding of what loads can be placed on the generator.

Also, rather than an electrical generator 'up top' why not a simple air compressor. Store the air in a tank, or lots of tanks, release through a turbine when needed.

Can get a bit of thermal energy to.

Only for small off grid stuff. Large turbines need to pump the juice straight to the grid. Less waste that way.

Edited August 22, 2019 by SteamyTea

[ProDave]

A small wind turbine is on my "to do eventually" list. Definitely sub 1Kw and it will have to be cheap (probably Chinese from ebay) as I don't expect much yield from it.

[Ralph]

I was under the impression that domestic turbines even with blades about 2 meters long need a quite high windspeeds to get anywhere near 1kW and mostly produced a 150 Watts on normally breezy day.

[Jeremy Harris]

5 minutes ago, Ralph said:

I was under the impression that domestic turbines even with blades about 2 meters long need a quite high windspeeds to get anywhere near 1kW and mostly produced a 150 Watts on normally breezy day.

 

 

You can work out the power for a given wind speed fairly easily, the main variables are the efficiency (doesn't change by much, though) and the true wind speed (may be less than it seems due to turbulence and the effect of ground friction).

 

The formulae for power is:

 

Power (W) = C_P·0.5· ρ ·A ·V³

 

where:

 

C_P = the efficiency of the wind turbine (typically between 0.25 and 0.45)

 

ρ = air density (typically about 1.25kg/m³)

 

A = the swept area of the blades, in m²

 

V = the wind speed, in m/s

 

For a 2m diameter wind turbine, with an efficiency of 0.3, in a wind of 2.5m/s (about 4.9kts) the output power would be about 0.3·0.5· 1.25 ·3.14159 ·2.5³ = 9.2 W

 

Increase the wind speed to 5m/s (about 9.7kts) and the power increases to about 73.6 W

 

Increase the wind speed to 10m/s (about 19.4kts) and the power increases to about 589 W

[Ralph]

1 minute ago, JSHarris said:

For a 2m diameter wind turbine, with an efficiency of 0.3, in a wind of 2.5m/s (about 4.9kts) the output power would be about 0.3·0.5· 1.25 ·3.14159 ·2.5³ = 9.2 W

 

Increase the wind speed to 5m/s (about 9.7kts) and the power increases to about 73.6 W

 

Increase the wind speed to 10m/s (about 19.4kts) and the power increases to about 589 W

So from that you're going to need a wind speed of about 12m/s to get 977 W. That's about 26 mph or a force 6. 

Even in Shetland with an average of 7 m/s you're only getting about 190 W

[SteamyTea]

35 minutes ago, JSHarris said:

the main variables are the efficiency (doesn't change by much, though)

Not so sure about this.

With small turbines, the area in the centre is pretty 'dead', so generally small turbines have very poor efficiency.

Also as the blades are fixed, their efficiency tends to vary with windspeed, with peak efficiency generally happening a little below the windspeed where peak output happens.

That is before all the electronic that convert or condition the output have had a chance to convert mechanical energy into electrical energy and thermal energy.

You can get a rough approximation of yield by using statistical methods involving an accumulative weibull distribution, but this tends not to work too well for small turbines that are affected by the ground, wind direction and the other problems mentioned above.

 

As a general note about wind turbines, they very rarely produce the name plate output as the windspeeds needed, say 15 m/s is quite high for close to the ground.

With small turbines (domestic), they are designed to automatically stall at just over the maximum rated windspeed for safety reasons.

The rule of thumb for large turbines is bigger, higher and with as little 'clutter' around them.  Why they work so well out at sea, or on top of a hill, or even on a plain, they are rubbish alongside a hill, high buildings and even woodland.

 

Edited August 22, 2019 by SteamyTea