@old_scientist And would almost certainly need planning permission! Would this be very likely to be granted within an urban environment anyway? (And allow for the energy required to power the red warning light atop the tower😉) Toodles.

Posted by: @toodles

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@old_scientist And would almost certainly need planning permission! Would this be very likely to be granted within an urban environment anyway? (And allow for the energy required to power the red warning light atop the tower😉) Toodles.

Agreed. When I first looked into domestic wind, my initial impressions were there are easier ways of generating 2.5kW of intermittent renewable power (solar!).

I had a chat with ChatGPT about the relationships between wind speed, turbine size and power output. ChatGPT tells me:

• Electrical generation increases with the cube of wind speed
• Higher mounting height increases wind speed → which increases power cubically
• Electrical generation increases with the square of blade length

all of which tells us where wind is concerned, go big or go home. A large turbine swept diameter mounted at least 10m above the local roof / treeline is not practical on your average domestic street. This isn't something you can strap to your roof and generate meaningful amounts of electricity.

I guess we would all be interested in a small scale domestic wind turbine that could reliably cover house baseload of up to 300W. I looked at some of the smaller wind turbines commonly sold in the marine industry for boats in the hope of finding that magic bullet that may produce 5-10kW per day on a windy day when there's little to no solar.

For example, I looked at the Rutland 1200 wind turbine here, available for around £1500-1800:

https://www.marlec.co.uk/product/rutland-1200-terrain-windcharger/

It has a turbine diameter of 1.2m and a minimum mounting requirement of 6m. At 7m/s wind speed, it outputs around 100W, rising to around 300w at 12m/s which you may achieve on a windy day if mounted high enough (e.g, 10m above local roof / treeline). Many of these models are not designed to be grid tied, but rather for charging small scale DC battery systems. Once mounting costs and grid tied inverter systems are factored in (plus the cost of any planning application), you'd be looking at thousands of pounds for a system that may produce nothing to 300W on a windy day.

The global wind atlas tells me my mean average wind speed at 10m elevation for my location is 5.8m/s, and the Rutland 1200 turbine yield prediction documentation suggests I may expect an annual yield of ~700kWh per year for those wind speeds. That equates less than 2kW a day. At 5m/s constant wind speed, it only generates 40W output which may not even power an inverter. None of this makes me want to rush out and buy one or contact the local council to investigate planning requirements, let alone erect a 10-15m pole in my garden.

Posted by: @toodles

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@old_scientist And would almost certainly need planning permission! Would this be very likely to be granted within an urban environment anyway? (And allow for the energy required to power the red warning light atop the tower😉) Toodles.

Precisely. After all these years, when considering noise regulations and heat pumps, could we really say a person commissioning a heat pump does not carry the risk?  

There are several types of site which would be viable for a small wind-turbine, but there aren't many of them.

Let me put out a few pointers:

1: You won't achieve any useful output from a turbine at a wind-speed below 3m/s. It's just idling.

2: If you want to erect a turbine tower less than 15m high, then you need to  place it on the upslope of the prevailing wind direction. That just happens to suit where I live! As the ground rises, the air get compressed and the effective wind speed is multiplied.

3. The energy output depends on the ratio between the wind-speed and the (angular momentum of) the blade-tip.

If the turbine spins too fast then you won't get any benefit from the end of the blade because its velocity is greater than the air moving past it. That's why large commercial turbines appear to turn slowly.

4: In a domestic setting a wind-turbine with peak output above 2kW would be regarded as 'medium', rather than 'small'.

If there's a 3-day period of wind, then you'd be generating 3 x 24 (hrs) x 2kW, which is 144kWh.
Where the heck do you expect to put all that electricity?!

5: You can't just switch-off a wind-turbine like you do with solar-panels. The turbine must always 'see' a load connected to it.

Opening the contacts of a switch/contactor would present no load, thereby allowing the blades to spin ever faster. That leads to over-heating of the wire coils in the turbine head, which is called 'a fire'.

6: Yes, you require Planning Permission to erect a wind turbine, but most Local Planning Authorities would be sympathetic.

The two issues you'd need to address in the Application are:

• noise, either from the blades turning, or from wire-stays 'singing' due to harmonic vibrations
• shadow-flicker; as the shadow of a blade passes across a window, the room will seem to be subjected to a stroboscopic light source. That can cause epileptic episodes.

7: The main 'authority' on DIY domestic wind turbines is Hugh Piggott  – www.scoraigwind.co.uk

He and his fellow islanders have built scores of plywood turbines from scratch, and have often run week-long courses.

If it's still available, get hold of his well illustrated "Wind Turbine Recipe Book" which will tell you everything you need to know.

If you'd like to have a go at building your own wind (or water) turbine, but don't fancy winding a set of coils by hand(!), then you can buy a ready-built Permanent Magnet Generator (PMG).

To that you'd add a set of blades and a tower to mount it on.

That's how I started, buying in a PMG, and a hub with six moulded blades.

My tower is constructed from two lengths of aluminium lighting-truss which I picked up from a disco-hall that had gone into liquidation.

A PMG is very similar to the sort of electric motors which are now used for electric bikes, but you're using it in reverse. This means there are now loads of options from which to choose the size/power you're after.

Of course, there are also rogue traders who haven't a clue what they're offering for sale.
Here's a 15kilovolt 3-phase DC motor, for example!

After much research we'll be getting an Istabreeze Heli 4.

Posted by: @transparent

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6: Yes, you require Planning Permission to erect a wind turbine, but most Local Planning Authorities would be sympathetic.

The two issues you'd need to address in the Application are:

• noise, either from the blades turning, or from wire-stays 'singing' due to harmonic vibrations
• shadow-flicker; as the shadow of a blade passes across a window, the room will seem to be subjected to a stroboscopic light source. That can cause epileptic episodes.

I am pleased that the image of a catastrophic effect on bird population (that some world leaders showed extreme empathy for) did not influence our legal planning framework!  

Interesting, but could we have a situation where someone would erect a 60ft pole in their backgarden, and the council just informs the adjoining properties. Yet if the applicant back garden would be at the top of a hill, the accountability for the stroboscopic effect to people living in the valley below would not be clear? 

There seem to be plenty of systems available, including that Dump load component, essential to deal with over production. 

Posted by: @batpred

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could we have a situation where someone would erect a 60ft pole in their backgarden, and the council just informs the adjoining properties.

No. Whilst it's not an offence to erect a turbine on a 60ft pole in your garden, it becomes one if you ignore an instruction from the Planning Enforcement Officer to remove it 😊 

The onus is on the prospective owner of a wind turbine to provide the Local Planning Authority with maps and calculations showing where blade shadows would fall for all days of the year.
There is software available to undertake this task.

Posted by: @transparent

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No. Whilst it's not an offence to erect a turbine on a 60ft pole in your garden, it becomes one if you ignore an instruction from the Planning Enforcement Officer to remove it 😊 

🤭 Yes, I meant if someone planning to erect that 60ft pole in their garden would submit a prior planning application. But you already crushed my dream (probably misguided) to claim that green community champion "crown" by trailblazing that sort of project in my suburban neighbourhood... 😁