Renewable Energy: wind energy -the basics

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- CommentAuthorconkeil
- CommentTimeJan 23rd 2009
can anyone put in really simple terms the amount of energy you get from a turbine.
how much does an average house need and can a turbine meet these needs. for example a 15kw as mentioned -
how quickly would this be used up etc etc

sorry left school early!!
- CommentAuthorDominic Cooney
- CommentTimeJan 23rd 2009
You need to work out your annual energy requirement first, then find your average annual wind speed for your location at http://www.bwea.com/noabl/
bearing in mind this is not very accurate and a lot will depend on where you site the wind turbine in terms of obstructions such as trees and buildings.

Grid connected or off grid? two distinct set ups, both with their own pros and cons.

Jane has an off-grid 6kW in a windy spot that seems to provide all their household needs without resort to diesel generator.

I am grid connected with 2 x 15kW in a less windy spot, and hoping to provide enough power on average over the year - I worked out my (NB Manufacturing Business) energy requirement to be 76,000 kWh per annum and with an average annual wind speed of 6.3m/s at 10 metres above ground level we have calculated that they should produce 86,000 kWh per annum so there is 10k leeway in case the big trees alongside the road have a bad effect.

Working out how financially viable it is, is a whole other story.
- CommentAuthorNick Parsons
- CommentTimeJan 23rd 2009
Find annual average w/s. assess obstructions. Establish max mast height. Remember the cube and square rules. (Output varies as cube of w/s - 2 x w/s = 8 x power, output varies as square of blade dia - 2 x blade dia = 4 x power). Get manuf's power-curves.
- CommentAuthorMarkK
- CommentTimeJan 23rd 2009
alternatively go to www.segen.co.uk, tap in your postcode, pick a turbine (start off at 5kW).... and hey presto...a good starting point on estimations of performance.

as a guide...av home in the UK (on mains gas) uses about 5000kWh of power a year.
- CommentAuthorCWatters
- CommentTimeJan 24th 2009
Worth noting that over a year a mill won't average anything like it's rated capacity..

Dominic above has two 15kw mills so 30KW in total. If they were running flat out 24x7 you might expect that they would produce 30 x 24 x 7 x 365 = 1,839,600 kWh a year but he's predicting "only" 86,000 kWh a year. I make that about 4.5% of their peak rated capacity.
- CommentAuthorDominic Cooney
- CommentTimeJan 24th 2009
Worth noting, but not worth obsessing about. (e.g. Solar panels don't work at night)
More important to work out how much energy you require over the year and what size of installation you need to meet that requirement, as well as how much it is going to cost you/save you/make you (depending on how you look at it).
Go for slightly more than you need, so that if all goes according to plan you are exporting more than you import.
- CommentAuthortony
- CommentTimeJan 24th 2009
Reduce energy requirements first

Forget a wind turbine unless you live at the top of a hill.
- CommentAuthorjon
- CommentTimeJan 24th 2009
As a general rule, if you're at the top of a windy hill and you can afford to get a mast up about 30 metres it may prove to be economically worthwhile. If you live in a conurbation, forget the idea. In-between the previous two situations, you might make it stack up, but not economically.

Hope this helps
- CommentAuthorjon
- CommentTimeJan 24th 2009
You beat me to it Tony, by 11 seconds
- CommentAuthorShepherd
- CommentTimeJan 24th 2009
There was a Which article on a wind turbine in a built up area - as I recall took slightly more electricity than it generated due to the electronics in the head.
- CommentAuthordave45
- CommentTimeJan 25th 2009
You will find that saving a kWh is far easier, safer and many times cheaper than trying to generate one with a wind turbine.
I have a small Marlec turbine on a scaffolding pole on my garage. It works but it generates so little juice as to be useless.
For me it was an experiment... learn from it - don't waste your money!
- CommentAuthorCarbon Free Energy
- CommentTimeJan 25th 2009
I disagree with a few comments. In my experience (and I've got a bit ) the correct turbine in a well suited location with few obstacles to create turbulence can prove to be a great success. A small turbine sub 5kW will rarely if ever prove economically viable and anything mounted to a building will always disappoint. Living on a hill isn't necessary you just need the right kit in the right place.

There are a few systems coming to market specifically designed to for sites with less wind, these all have a very large swept area and require a simple gearbox to attain generator rpm but can work incredibly well. Take a look at the Swiss built Aventa AV-7 and the Gaia 11kW turbines.

Paul
- CommentAuthorrobJH
- CommentTimeJan 26th 2009
Well the average house (whatever that actually is!) uses around 4000kWh of electricity per year. Just don't multiply the "rated" power output by the number of seconds in a year!!! The rated power output at the rated wind speed is a complete non-sense. Most small turbines seem to be rated at 12m/s (~25mph) but, in Cambridge for example at no point last year did the wind speed reach 12m/s - so I am told. In Sheffield the average speed was nearer 5m/s. However, a site survey is absolutely critical so you know how much energy is in the wind around where you intend to site the wind turbine.

Don't get me wrong, I am all in favour of them for urban power generation - but only in the right places. Now I mention this, does any one know of a good wind anemometer that can be used to measure average wind speeds over days at a time without connection to a PC?
- CommentAuthorCarbon Free Energy
- CommentTimeJan 27th 2009
I think Urban wind generation is a non starter to be honest, we have a few enquiries from people who want either building mounted systems or have unsuitable properties so I explain why wind isn't the answer for their location, maybe I'm a bad businessman but at least I can sleep at night!
Out here in the East we have fen's with vast unobstructed farmland which are great for wind generation.

Paul
- CommentAuthorMarkK
- CommentTimeJan 27th 2009
Posted By: robJHWell the average house (whatever that actually is!) uses around 4000kWh of electricity per year. Just don't multiply the "rated" power output by the number of seconds in a year!!! The rated power output at the rated wind speed is a complete non-sense. Most small turbines seem to be rated at 12m/s (~25mph) but, in Cambridge for example at no point last year did the wind speed reach 12m/s - so I am told. In Sheffield the average speed was nearer 5m/s. However, a site survey is absolutely critical so you know how much energy is in the wind around where you intend to site the wind turbine.

Don't get me wrong, I am all in favour of them for urban power generation - but only in the right places. Now I mention this, does any one know of a good wind anemometer that can be used to measure average wind speeds over days at a time without connection to a PC?

Not being unhelpful - but if you need an anemometer, then your site isn't windy enough. All the anemometer will do (and to do it properly it needs to record for a year) is suggest that your site is borderline at best. If it was windy enough, you'd know.

Anyone who suggest urban wind works - seek out www.warwickwindtrials.org.uk . There's plenty of turbulent wind in the city, but that's no good for generating power. Anyone who says any different (i'm open minded...so if they have a patent saying otherwise, then bring it on!) has been deceived.
- CommentAuthorrobJH
- CommentTimeJan 27th 2009
Well I disagree! I live at the top of a hill in Sheffield (perhaps the mention of Cambridge was miss-leading!) that over looks the Peak District - when it is windy it almost blows the roof off, but being me, I want the numbers and therefore wonder about the anemometer. The site _could_ be ideal. I should say I lecture at the University and part of my research area is wind turbine aerodynamics - both VAWT and HAWT carrying out wind tunnel research as well as computational simulations. The turbulence levels in cities are an issue, but it is complex as it all depends on turbulence level as well as length scale relative to the wind turbine, but nothing has really been done is this area. Ripe for research!

Anyway, my question remains - anyone know of an anemometer what will log wind data over weeks without a PC?
- CommentAuthorshakey
- CommentTimeJan 29th 2009
GREEN ELECTRICITY?

I was watching the TV programm "It's not easy to be green" last night and the hairy faced presenter Mr Strawbridge made reference to a solar heating system which "Uses electricity from green sources to power the water pump."

There are some very clever people on this forum so hoping one or more of them picks up on this link I submit the following question which being of only average interlect I'm very curious to learn the answer.

How does 'Green generated electricity' know which house to visit? Is there a seperate electricity grid only accessable to green power and those of us that subscribe to green power supliers. If I switch to a 'Green power' supplier how can I be sure that dirty coal or nuclear generated electricity is not sneaking into my ring main?

Concerned of Ancaster
- CommentAuthorSimonH
- CommentTimeJan 29th 2009
<blockquote><cite>Posted By: shakey</cite>GREEN ELECTRICITY?
How does 'Green generated electricity' know which house to visit? Is there a seperate electricity grid only accessable to green power and those of us that subscribe to green power supliers. If I switch to a 'Green power' supplier how can I be sure that dirty coal or nuclear generated electricity is not sneaking into my ring main?

Concerned of Ancaster</blockquote>

Think of the grid as a pool - your energy supplier has to find energy to put in the pool for you to pull some off for your house. If you use 3000kwh over a year, they have to source and pay for 3000kWh of green energy. It's actually done on a 1/2 hourly basis. The reason green electric is expensive is that they have to get a contract to guarantee they can meet your demand. Which I guess means paying top whack to get the contract with suppliers.

Your not paying for individual electrons that came from a wind turbine/solar panel/water wheel, but you are paying for them to be put on the grid. In reality I know that my electrons probably come from an 800MW coal fired powerstation down the road. But what I also know is that my me paying for 100% green energy to go in the pool, then the big mainly fossil based energy co's need to find some elsewhere, to meet their renewables target. They can't buy the electric I just bought.

That's good enough for me. It's cheaper than buying my own PV - which is no good anyway as I'm not here in the day to use the electricity. And more reliable than hoping it wil be windy.

By selecting green energy you are sending a signal to the market, encouraging investment in green power sources, and increasing the take up above the obligation on the big 6 energy suppliers.

Simon
- CommentAuthordave45
- CommentTimeFeb 1st 2009 edited
Posted By: shakeyGREEN ELECTRICITY?
But what I also know is that my me paying for 100% green energy to go in the pool, then the big mainly fossil based energy co's need to find some elsewhere, to meet their renewables target. They can't buy the electric I just bought.

Simon

I'm with Good Energy (100% renewable electricity). I believe their accounts show that they flog off their surplus ROCs (to whom?), so this argument doesn't really stand up. I'm not sure the whole thing isn't more than a little greenwash. They have their own windfarm, yet hoicked my prices up royally in line with gas prices (so who profits?). They bought electricity in advance at the top of the market and now can't reduce my bill as much as other outfits.... so I am paying gas prices for "green" electricity and subsidising their bad timing decisions... its getting less and less persuasive for me. Perhaps I should just go with the cheapest and invest the savings directly into something more obviously green.
- CommentAuthorecoenergyni
- CommentTimeFeb 5th 2009
Customers signing up to 'green electricity' is a cheap way for the generating companies to meet their carbon reduction obligations. Green electricity is expensive if you add it all up. Whilst the wind turbine is producing, there is the same capacity on 'spinning reserve' at a conventional power station ready to kick in when the wind fails. 'Its not Easy Going Green' is full of myths and mis-information. It doesnt appear to be peer reviewed.
- CommentAuthorralphd
- CommentTimeFeb 5th 2009
Posted By: MarkKalternatively go to www.segen.co.uk, tap in your postcode, pick a turbine (start off at 5kW).... and hey presto...a good starting point on estimations of performance.

as a guide...av home in the UK (on mains gas) uses about 5000kWh of power a year.

My base electrical use is double that; ~30kWh/day. I have an electric hot water heater (no natural gas here). This coming summer will be my first with the solar collector (a single thermo-dynamics G32 panel); I don't expect my electrical to drop to 15kWh/day though...
- CommentAuthordave45
- CommentTimeFeb 5th 2009 edited
Posted By: ecoenergyni Whilst the wind turbine is producing, there is the same capacity on 'spinning reserve' at a conventional power station ready to kick in when the wind fails..

That is a mis-representation too - there are various types of reserve power, and commercial wind has some "capacity credit", the precise value of which is difficult to agree. A gigawatt nuke station likewise has to have reserves - and they ARE used - all too frequently ! The problem for wind is (easily?) manageable with current reserves according to the National Grid until wind reaches about 20% of total generation (NG say - sounds like a guess). Its a statistical thing, complex and new territory for the UK's grid which was designed for centralised generators. (google for "holtinnen" if you want some background to the issues).

Wind turbines at worst operate as fuel-savers for conventional power stations. At best they can displace some power stations entirely, but not megawatt for megawatt. The NETA/BETTA market mechanism complicates it all too.

Back to the original question - take your house's annual electricity consumption in kWh and divide it by the number of hours in a year. e.g. 5500 kwH consumption implies a 5500/8760 = 628 watt house (electrically). So your own wind turbine would need to generate this 24x7x365. But a house doesn't consume at a steady rate - in the middle of the night you may be down to tens of watts, and in the morning you may hit 9000 watts with an electric shower. And a wind turbine doesn't produce at a steady rate or when you want the energy. If you were off-grid you would have to use expensive battery storage, and you'd ditch the electric shower! The rated power generation of a small wind turbine is probably useless as a guidance as actual production depends critically on both the distribution of windspeeds in your area and local conditions. (Google for Paul Gipe for more on small wind)
- CommentAuthordave45
- CommentTimeFeb 5th 2009
In fact if you add up ALL your energy consumption per annum in kWh (gas, electricity, solar, wood etc) and divide by 8760 to give you a figure in watts, that is a good rule-of-thumb guide to the "greenness" of your house.

or poorness of your insulation.

or extravagance of consumption.

Does anyone publish this, analyse it by region, house type etc? Southerners in balmy Bournemouth should use a lot less than Scots in Stornoway. Do they?
- CommentAuthorted
- CommentTimeFeb 6th 2009 edited
The BERR website has reports giving household consumption figures by region.

http://www.berr.gov.uk/whatwedo/energy/statistics/regional/index.html
- CommentAuthordave45
- CommentTimeFeb 8th 2009
mm - the BERR regional figures seem to correlate more with affluence than outside temperature !
- CommentAuthorfuncrusher
- CommentTimeFeb 9th 2009
micro windpower has no practical role - and certainly no economic role - in electricity generation in ordinary homes, but might do so off-grid in the Hebrides. To point out just one fundamental drawback: there is no practical method of storing electricity (as opposed to heat), and because the majority of wind power is harvested at high wind-speeds the electricity generated will be hopelessly insufficient for the overwhelming majority of the time.
- CommentAuthorSimonH
- CommentTimeFeb 9th 2009
I'll address a couple of points in one post...

ROCs were invented to be sold. It's a bonus paid on top of the price you get for electricity for being good. They were designed to offset the increased cost of generating the green electric. Take Good Energy for example - all their electric is green, so green electric has hit the grid. All suppliers currently have an obligation to generate about 9% of their electricity through green sources. So what do good energy do? Sit on their ROCs which have value, and make a huge loss, or sell them (for about �40 each) to suppliers who for whatever reason didn't meet their 9% target. What thet actually do is sell 95% of their ROCs, but retire 5%. Meaning no one can get their hands on them, to present as green generation. You could argue they should retire more, but this would put up the cost to consumers (like me) - probably too much.

Coal fired powerstations aren't on/off. They have standby, which means furnace is running but not at full pelt , lets make up a figure (as I can't get real ones) say 1000 tonnes coal an hour full generation 100 tonnes/hour standby. They take about 4 hours to come back on line no good for coronation street breaks, but good enough if the wind speeds nationally are starting to drop. They take about 2 weeks to cool down sufficiently to get the boiler cleaned out.

What we need is a couple more "Dinorwigs" a pumped hydro station which can reacts in under 12 seconds, to dump 1320 MW on the grid....
http://www.fhc.co.uk/dinorwig.htm

That, plus a few Vanadium flow batteries (so stored wind power can be sold at peak rate rather than off peak).

All that said you can meet your energy needs for a house, but it might be cheaper to get your neighbours to invest in a community scheme and stick a 2 MW turbine somewhere in the atlantic / north sea ;-)

Simon
- CommentAuthorgavstamp
- CommentTimeFeb 17th 2009
Posted by funcrusher
* CommentTimeFeb 9th 2009

micro windpower has no practical role - and certainly no economic role - in electricity generation in ordinary homes, but might do so off-grid in the Hebrides. To point out just one fundamental drawback: there is no practical method of storing electricity (as opposed to heat), and because the majority of wind power is harvested at high wind-speeds the electricity generated will be hopelessly insufficient for the overwhelming majority of the time.
===============================================================================================
Funcrusher, I have to disagree with your assesment that the majority of wind power is harvested at high speeds and that it has no economic role to play. For example, if you have an average wind speed of 6.5 m/s, which is not that high, then using a Gaia Wind 11kW turbine you can produce about 40,000 units if you have a good, clean site. Even if you exported all of that at 7p/unit, your payback would still be in the region of 5.5 years. If you consume a portion of that at, say, 12p/unit then of course your payback time comes down. Definitely worth thinking about.
- CommentAuthorPaul in Montreal
- CommentTimeFeb 17th 2009 edited
Posted By: gavstampif you have an average wind speed of 6.5 m/s, which is not that high, then using a Gaia Wind 11kW turbine you can produce about 40,000 units if you have a good, clean site.
There's two big ifs there. Not too many urban sites would satisfy both ifs ... which was funcrusher's point I believe.

Paul in Montreal.
- CommentAuthorted
- CommentTimeFeb 17th 2009
As recent microwind reports (BRE, Carbon Trust, Encraft) have stated - roof-top wind speeds in urban areas in the UK average 2 to 2.5 m/s and many trial sites did not even produce enough power to balance that consumed by the inverter. funcrusher's comments are spot on.

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Renewable Energy: wind energy -the basics