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Inverter advice

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Inverter advice

Unread postby mrniceguy » Tue 12 Apr 2005, 08:24:07

I'm currently working on a small home built wind turbine project. However I don't wish to use batteries to store energy, instead I'd like to feed directly into an inverter which will in-turn plug in to my house ring main thus reducing my dependance on the grid. A similar system can be found here http://www.windsave.com/index.htm The only Inverter that I have found which will deal with variable power is the Windy Boy inverter which seems to be quite expensive and is designed for large projects. I'd be grateful if anyone knows of a suitable UK spec inverter (that's not too expensive) which can be used with variable power.

regards

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Unread postby gnm » Tue 12 Apr 2005, 10:39:53

There are a number of charge controls which can deal with variable DC power (or is the output variable AC?) - you could feed wide range dc into a charge control then use any grid tie inverter you wish... If the wind genny is variable AC out then I am afraid I don't have much experience with that...

http://www.homepower.com is a good resource....

good luck!

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Unread postby pip » Tue 12 Apr 2005, 11:39:14

Shouldn't his wind generator produce constant voltage, and the watts will vary by wind speed? I'm a poor electrician but that's the way I understand it, correct me if I'm wrong.

You should buy an DC to AC inverter that will handle the max capacity in watts of the generator, I'm assuming the output of the turbine is in DC. If you have no battery storage, you will have to vary how much electricity you use based on wind speed.
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Unread postby gnm » Tue 12 Apr 2005, 12:52:24

Ideally the voltage _should_ be consistent. Some generators are 2 or 3 phase AC even... But you'll have to match it to your line or household phase...
Some home turbines (and some commercial ones) have widely varying voltage (depends on how they are wound) and no voltage regulator at all. In thoses cases you can easily use a mppt type charge controller which will digest just about anything and output your selected voltage.

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Unread postby mrniceguy » Tue 12 Apr 2005, 16:20:32

$this->bbcode_second_pass_quote('', 'g')nm
http://www.homepower.com is a good resource


Thanks there's a pdf comparing various inverters.

$this->bbcode_second_pass_quote('', 'p')ip
You should buy an DC to AC inverter that will handle the max capacity in watts of the generator, I'm assuming the output of the turbine is in DC. If you have no battery storage, you will have to vary how much electricity you use based on wind speed


I'm going to build a permanant magnet generator like this http://www.windstuffnow.com/main/alt_from_scratch.htm
My aim isn't to become completely dependant on the wind turbine for all our electricty I just want to cut down on what we buy from the utility company

$this->bbcode_second_pass_quote('', 'g')nm
In thoses cases you can easily use a mppt type charge controller which will digest just about anything and output your selected voltage.

That's what I was looking for! many thanks for the feedback
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Unread postby Devil » Wed 13 Apr 2005, 06:59:34

$this->bbcode_second_pass_quote('mrniceguy', ' ')
My aim isn't to become completely dependant on the wind turbine for all our electricty


Even when the wind does not blow?

I have the wind data from Manchester and London. As they are quite similar, I guess it would be fair to assume Nottingham would be in between. Roughly 50% of the time, the windspeed is <5 m/s and only 3-5% of the time is it >10 m/s, at 50 m over ground level in open terrain. In between, the time percentage drops rapidly from 5 (14%) to 10 (2%) m/s.

This would pose some practical problems. Commercial turbines give full output at ~16-20 m/s, shutting down at >22-25 m/s. At 10 m/s, the o/p is typically 30 - 40% and at 5 m/s 5 - 15%.

As you are in a region of relatively low wind average wind velocity, you have a choice: the blades are designed to work efficiently at either, say, 5 m/s or 20 m/s. In the former case, it will blow itself to bits come the first gale, even if you feather the blades or, in the latter case, you will have to be content with an average of <20% efficiency, in which case you will need to make it 5-10 times bigger than you think.

Even in Manchester, the wind velocity is at 0 for 5% of the time, usually during the long anticyclone period averaging between mid-November and mid-December, lasting 5 to 10 days, although there are other typical (occurring for over 40% of the years) anticyclones, notably mid-May to mid-June and in September.

Please remember that you will require planning permission, including calculations of safety factors, and permission from your local electricity supplier if you aim to provide surplus to the grid. The latter will have to include details of phase correction and harmonic distortion before they will grant you the go-ahead. It may be that they will have a list of approved inverters; if so, you will have little choice.

I mention this so that you don't go into it unprepared, only to hit a brick wall. If I were you, I'd firstly rig a recording anemometer at the place you propose installing it, so that you can see what the local wind pattern (speed and direction) is (there may be atypical katabatic winds, for example, or some other orographic vertical velocities due to nearby topography or buildings). From those data, you could better dimension the turbine to your needs. It may help to get the records from the nearest meteo office, but remember that microclimates can play an important role, so, even if the office is fairly close, it will not give you an accurate picture (for the anecdote, I have two distinct microclimates in my 1100 m² garden).

Please excuse me for pointing these potential problems out, but I have the feeling from your posts that you may not have thought these things through. If this is not the case, I apologise. Whatever, good luck; you will probably need it! :)
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Unread postby mrniceguy » Wed 13 Apr 2005, 13:23:24

$this->bbcode_second_pass_quote('Devil', '')$this->bbcode_second_pass_quote('mrniceguy', ' ')
My aim isn't to become completely dependant on the wind turbine for all our electricty


Even when the wind does not blow?

I have the wind data from Manchester and London. As they are quite similar, I guess it would be fair to assume Nottingham would be in between. Roughly 50% of the time, the windspeed is <5 m/s and only 3-5% of the time is it >10 m/s, at 50 m over ground level in open terrain. In between, the time percentage drops rapidly from 5 (14%) to 10 (2%) m/s.

This would pose some practical problems. Commercial turbines give full output at ~16-20 m/s, shutting down at >22-25 m/s. At 10 m/s, the o/p is typically 30 - 40% and at 5 m/s 5 - 15%.

As you are in a region of relatively low wind average wind velocity, you have a choice: the blades are designed to work efficiently at either, say, 5 m/s or 20 m/s. In the former case, it will blow itself to bits come the first gale, even if you feather the blades or, in the latter case, you will have to be content with an average of <20% efficiency, in which case you will need to make it 5-10 times bigger than you think.

Even in Manchester, the wind velocity is at 0 for 5% of the time, usually during the long anticyclone period averaging between mid-November and mid-December, lasting 5 to 10 days, although there are other typical (occurring for over 40% of the years) anticyclones, notably mid-May to mid-June and in September.

Please remember that you will require planning permission, including calculations of safety factors, and permission from your local electricity supplier if you aim to provide surplus to the grid. The latter will have to include details of phase correction and harmonic distortion before they will grant you the go-ahead. It may be that they will have a list of approved inverters; if so, you will have little choice.

I mention this so that you don't go into it unprepared, only to hit a brick wall. If I were you, I'd firstly rig a recording anemometer at the place you propose installing it, so that you can see what the local wind pattern (speed and direction) is (there may be atypical katabatic winds, for example, or some other orographic vertical velocities due to nearby topography or buildings). From those data, you could better dimension the turbine to your needs. It may help to get the records from the nearest meteo office, but remember that microclimates can play an important role, so, even if the office is fairly close, it will not give you an accurate picture (for the anecdote, I have two distinct microclimates in my 1100 m² garden).

Please excuse me for pointing these potential problems out, but I have the feeling from your posts that you may not have thought these things through. If this is not the case, I apologise. Whatever, good luck; you will probably need it! :)


Thanks for your comments I have absolutely no problem with anyone pointing out potential problems.

I don't intend to be dependant on the turbine, I just want to reduce my electricity bills. As far as wind speed goes, during winter (when we use most electricity), it's always windy here, I also have the advantage of living at the top of a hill in an exposed position, however I take your point regarding putting up an anemometer and doing some research into local wind conditions.

The project is currently still in the design stage and I'm still gathering information and considering feasibility, this post is part of that process. Incidentally, I'm looking into building a darrieus type VAWT which is more suitable for “spoiled wind” typically found around buildings.

As far as planning permission goes I'm not sure that it is required for the sort of small scale turbine that I'm thinking of, from the enquiries I have made, it seems that you only need planning permission for a structure which is higher than your own house eg. Lots of houses have satellite dishes and (in most cases) these do not require planning permission. Design calcs for building regulations (if required) will be to BS6399-2 1997 Design wind loads.

According to the UK energy white paper the Government is committed to generating 10% of our electricity by 2010 and 20% by 2020 with renewables unfortunately these targets are unlikely to be met. I think that as energy costs increase micro generating projects will be encouraged as the availability of land for large scale wind farms reduces. If 10% of homes in the UK had a small wind turbine generating 30% of their electricity, that would be 3% towards the governments targets.
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Unread postby Bandidoz » Fri 15 Apr 2005, 00:01:44

I'd be inclined to regulate your WT output with a switched mode power supply or regulator. This creates a stable DC supply that you can then apply to a bog-standard inverter. You could also "slug" the DC with a battery if you so wish.
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