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Blue Peter
Joined: 21 Mar 2005
Posts: 2400
Location: Milton Keynes
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wellington womble
Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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Lozzie
Joined: 25 May 2005
Posts: 2595
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 Posted: Thu Jun 02, 05 10:01 am Post subject: Atricle on Wind Power on a small scale |
 
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I found this (sorry, if it is already old news. It was posted on MSN Messenger's home page a couple of days ago. There is no indication of who wrote it, I'm afraid):
Introduction
Harnessing wind as a renewable energy source involves converting the power within a moving air mass (wind) into rotating shaft power which in turn generates electricity. Modern wind turbines contain rotors fitted with aerodynamic blades, which utilise lift forces caused by the wind on the blades.
Wind energy resources
In the UK we have a large potential wind resource. Although we have 40% of Europe's total wind energy resource, it remains largely untapped, currently meeting only about 0.5% of our electricity requirements.
Power from the wind is proportional to the cube of the wind speed therefore relatively minor variations in wind speed can result in large changes in potential output.
Individual turbines vary in size and power output from a few hundred watts to 2-3 megawatts (as a guide, an electrical kettle uses approximately 2,000 watts or 2 kilowatt). Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines grouped on wind farms supplying electricity to the grid.
Small Scale Wind and your home
Wind speed increases with height so it is best to have the turbine high on a mast or tower. Generally speaking the ideal sitting is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings. However, small-scale building integrated wind turbines suitable for urban locations are currently being developed and will be available to install in homes and other buildings within the next few years, Knowledge of the local wind resource is critical to designing a wind energy system and predicting output. For domestic installations a good source of information on local wind speeds is the NOABL database which can be accessed from the British Wind Energy Association alternatively you can collect
primary information by setting up your own monitoring mast to record wind speed. An ideal way of doing this is with an anemometer which can be bought online for around �120.
Planning issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority.
Stand-alone or grid-connected systems?
Small scale wind power is particularly suitable for remote off-grid
locations where conventional methods of supply are expensive or impractical.
Most small wind turbines generate direct current (DC) electricity. Off-grid systems require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity). A controller is also required to ensure the batteries are not over or under-charged and can divert power to another useful source (e.g. space and/or water heaters) when the battery is fully charged. It is common to combine this system with a diesel generator for use during periods of low wind speeds. A combined wind and diesel system gives greater efficiency and flexibility than a diesel only
system. It allows the generator to be used at optimum load for short periods of time to charge batteries when there is little wind, rather than by constant use at varying loads.
Wind systems can also be installed where there is a grid connection. A special inverter and controller converts DC electricity to AC at a quality and standard that is acceptable to the grid. No battery storage is required. Any unused or excess electricity can be exported to the grid and sold to the local electricity supply company.
Cost and maintenance
Systems up to 1kW will cost around �3000 whereas larger systems in the region of 1.5kW to 6kW would cost between �4,000 - �18,000 installed. These costs would be inclusive of the turbine, mast, inverters, battery storage (if required) and installation, however it's important to remember that costs always vary depending on location and the size and type of system.
Turbines can have a life of up to 20 years but will require service checks every few years to ensure they continue to work efficiently. For battery storage systems, typical battery life is around 6-10 years, depending on the type, so batteries may have to be replaced at some point in the system's life.
Are there grants available?
Scotland:
Householders can access capital funding of up to �4000 from the Scottish Community and Householder Renewables Initiative (SCHRI).
For more information please see the funding and advice page or contact the SCHRI Hotline on 0800 138 8858.
Rest of the UK (England, Wales and Northern Ireland)
Householders can access grants for small scale wind from Clear Skies. For more information contact the Clear Skies Helpline on 08702 430 930 or visit their website. https://www.clear-skies.org/
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Lozzie
Joined: 25 May 2005
Posts: 2595
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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Rikki
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Rikki
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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| Posted: Thu Jun 09, 05 12:46 pm Post subject: |
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| Rikki wrote: |
| I'm currently installing a solar panel to heat my domestic hot water and have considered having a wind turbine connected to a heat sink imersion heater to heat the water in winter (when it's windy, but not sunny. Has anyone else done this. |
Its a simple-ish means of using wind energy, because it requires very little in the way of control systems and energy conversion, such as voltage stabilisation, transformers, inverters and mains synchronisation.
But its not common because usually folk *needing* wind energy are wanting to make the maximum/best possible use of it, and may well have access to plenty wood for water heating. Such folk, off grid would be charging batteries from the wind, and only when that store is full would they 'dump' wind energy into heating.
And if mains gas is available, using wind for water heating is unlikely to be very cost competitive.
| Rikki wrote: |
| I reckon the recoup period on my solar panels, home made and installed, is 10 years whereas a commercial installation would take 50 years to recoup the cost. Has anyone looked at how long it would take to recoup the �1500 of an electricity turbine? |
That's the answer no one knows yet.
And it'll be different, depending on the local wind conditions. Which could mean *very* local.
My understanding is that without specific planning permission, the whole turbine must be lower than the top of the roof. Which must mean the roof screening the turbine from some directions, and running it in turbulent air - further complicating any pre-calculation of its viability.
There is some concern that some rather optimistic assumptions must be made to have such things pay back financially before they are expected to wear out. And then there's the question of the energy in their production...
Rikki - may I suggest you register (it costs nothing), and start a new thread on your solar system? |
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woody
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Blue Peter
Joined: 21 Mar 2005
Posts: 2400
Location: Milton Keynes
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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fonant
Joined: 01 Feb 2005
Posts: 24
Location: West Sussex
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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| Posted: Mon Jul 04, 05 3:42 pm Post subject: |
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| fonant wrote: |
| dougal wrote: |
Generators simply cannot "plug in" because they'd have unsafe exposed live plug 'pins' if ever unplugged...  (and yes, Windsave's publicity does talk about "plugging in"  ) |
Yes, they can. Any grid-connected power generation system _must_ switch itself off if the grid fails. This is so that anyone working on the disconnected part of the grid is safe. |
 I already stand corrected on this!
| nathanbriggs wrote: |
{22 June 2005}... there is nothing in BS7671 which precludes the use of a 13Amp plug as a source of power as long as it safe to touch... Removal of the plug and touching the pins has to be safe, the energy must be below 50V within 2 cycles and less capacity than will stop a human heart, btw its still possible to get a little tingle if you are quick.
The windsave device is fitted with a plug, having said that most people will get it installed by a competent electrician who will promptly hard wire it.
Lastly the plug is standard but the socket requires a metal cover plate |
One point that hasn't been brought out is the necessary implication that such systems therefore *cannot* provide independence of the mains. During a powercut, your own generator *must* shut down too.
I'm not saying its physically impossible, just that it is the inevitable consequence of a "plug-in" system's mode of operation. (But would a power outlet on the generator side of the isolater be possible..?)
However there are a couple of points that might be taken in mitigation of my error.
1/ Isolating from the mains to protect maintenance/repair workers, does not require an *instant* disconnect. Personal safety on accidental unplugging demands a much more rapid response.
2/ While you can safely *just* isolate a solar pv panel, my understanding is that a wind turbine generator can't just be left to freewheel 'off-load' in the same fashion as one might isolate the pv panel. My understanding is that such freewheeling could destroy the turbine and/or the generator - please correct me if I've got that wrong! A mechanical brake can substitute for the braking effect of the electrical load, but I don't think such things are part of the design of these small domestic turbines. (Note that this is independent of the "self-furling" self-protection from increasing windspeed.) And dumping a kilowatt from the braking load is not exactly inconsiderable.
3/ And, Milud, I was mislead!
| nathanbriggs wrote: |
| {23 March 2005}...this means you can directly connect the Windsave power into the mains (although not by just plugging it in it must be hardwired). |
{My emphasis - Dougal}
As above, I think solar pv isolation can be just switching off, but that its more involved with turbines. And I note that those units are handling just 1/10th of the claimed maximum output of a Windsave.
| fonant wrote: |
| I love electronics - these things work so fast it makes the 50Hz mains frequency look slow! |
I remember learning Assember programming on a 1Mhz 6502 Microprocessor system, 25 years ago. The response and stability of stepper motor control is an experience that lives with me! Shortly thereafter I was faced with the problem of measuring the quiescent current of CMOS custom chips (nanoamps) in a rather noisy RF environment. Having rather fancy test equipment, I didn't bother with shielding at all. I simply made 1k measurements (!) and averaged them by adding and shifting the "decimal" point (1k rather than 1000 so it was simply a matter of a "binary shift"). The results were brilliantly reproduceable for particular chips - it worked!
I suspect that the programming problem for the solar inverter isolater would have been in reliably and quickly recognising the difference between noise and a powercut.
I am well aware just how quickly microelectronics can respond, and how difficult this can make interfacing to the real, slow, physical world..! |
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