"Toy" Wind Turbines

[MdB]

A while back, I refered to some wind turbines as being toys. I was talking about the micro type loved by David Cameron and the like. They used to be sold by B&Q for around £1.5k I think.

Here is a report of some actual results from them.

The best generated approx £0.20 of electricity per day. The worst generated £0.008 of electricity per day. I think my definition of toy was about right.

(Proper wind turbines on the other hand I think are great and we should have more of them.)

 

[Flyfisher]

However, Encraft MD Matthew Rhodes, quoted in The Guardian found one "benefit" from the white elephants. Apparently, seven out of ten people who see a turbine say it reminds them to save energy.

A bit of an expensive reminder though!

Talk about groping desperately for a silver lining - I wonder if his Technical Director is still employed there?

Personally, I would recommend an 'Electrisave' power meter as a reminder instead, which is a wireless device that displays your overall electricity consumption, updated every 10-15 seconds.

I bought one last year and it has certainly made us better at turning off lights etc. It's amazing how easy it is to have 1000W of unnecessary lighting burning away, but seeing it in big numbers seems to make a psychological difference.

However, I confess it hasn't caused anyone to volunteer to do the washing up by hand yet; instead, we just 'tut' to ourselves when we see the meter go to 4KW while the dishwasher does its stuff

But we have got our average usage down to about 22 units per day, from about 35 a year ago, so we've made some good progress.

 

[skier-hughes]

I read that dishwashers are more economical when used properly.

I wonder how much heating is wasted by people washing their hands under running hot water that hasn't heated up?

 

[Flyfisher]

Well, I like the sound of that - you've eased my guilt no end

Seriously though, we are very good at filling it to the brim (mainly because we're not good at clearing up straight after each meal ).

 

[Penners]

The average turbine also operates at only 1.84 per cent of capacity

If they're talking about MdB's "toy" turbines, then I can just about believe that figure, but they surely can't mean the average of all wind turbines?

 

[biffvernon]

Real wind turbines have a load factor around 30%.

 

[Flyfisher]

Talking of air-powered things, how about one of these: http://www.theaircar.com/

£5000
65mph top speed
90 miles range
Refuelled within 4 mins at a cost of £1.10
Oil change (1 litre) every 30,000 miles

I wonder if they can really achieve these specs in production?

 

[bower1]

I've been interested in this idea for a few years. I've often wondered whether compressing air with a wind turbine is better than producing electricity. Then you've got your 'fuel' at the point of use. And storing compressed air is not particularly hard?

 

[wobs]

Real wind turbines have a load factor around 30%.

Not in the UK I'm afraid. Its more like 25%. Germany is about 15-17% at the most, while in West Denmark, about 20%.

 

[biffvernon]

You can quibble about the odd percentage point but Scottish and offshore turbines are running around 30% load factor and that is the figure the industry commonly use as the standard for new windfarms across the UK with a better figure expected in favourable locations.

 

[wobs]

You can quibble about the odd percentage point but Scottish and offshore turbines are running around 30% load factor and that is the figure the industry commonly use as the standard for new windfarms across the UK with a better figure expected in favourable locations.

Its the figure the industry uses throughout the uk, as you say, despite evidence to the contrary.

To be 20% out on average is a bit naughty, when they know it not true.

 

[biffvernon]

The Garrad Hassan report for the DTI, http://www.berr.gov.uk/files/file22067.pdf gives offshore load factor well in excess of 30%.

Now, Wobs, please explain who is being naughty and what is not true.

 

[Penners]

Talking of air-powered things, how about one of these: http://www.theaircar.com/

£5000
65mph top speed
90 miles range
Refuelled within 4 mins at a cost of £1.10
Oil change (1 litre) every 30,000 miles

I wonder if they can really achieve these specs in production?

It seems too good to be true. And things that seem that usually are! But if they can genuinely live up to the claims, I will happily retract my scepticism.

 

[MdB]

Talking of air-powered things, how about one of these: http://www.theaircar.com/

£5000
65mph top speed
90 miles range
Refuelled within 4 mins at a cost of £1.10
Oil change (1 litre) every 30,000 miles

I wonder if they can really achieve these specs in production?

It seems too good to be true. And things that seem that usually are! But if they can genuinely live up to the claims, I will happily retract my scepticism.

Well I'm sure that there is something wrong with the following maths, please feel free to correct.

90m^3 of air compressed to 300 bar (data from here: http://www.theaircar.com/tecno.html)
contains 90 x 110 x ln(300/1) = 56MJ of potential energy. (equation from here: http://en.wikipedia.org/wiki/Compressed_air_energy_storage)
56MJ = 21 horsepower hours.

This figure compares fairly well with the 22 horse power with a 55min operating time given here: http://www.theaircar.com/onecatsEN.html

It does assume a 100% efficient engine though and 22 horsepower isn't much.

 

[wobs]

The Garrad Hassan report for the DTI, http://www.berr.gov.uk/files/file22067.pdf gives offshore load factor well in excess of 30%.

Now, Wobs, please explain who is being naughty and what is not true.

The wind turbine industry has a poor record when it comes to honesty. They quote a load factor of 30% for any new trurbine they want to put up regardless of where it may go.

I wasn't talking about off shore, I was referring to actual experience at work and offers I've seen from various manufacturers, and a proposed wind farm near to a friends town where it would be quite inappropriately sited.

They quote this figure when they know it won't produce anything near it.

Don't get me wrong, I'm not against them, just that we must be sceptical about their claims. That the amount of CO2 saved is less than claimed. That the more we install, eventually we'll come up against diminishing returns in terms of CO2, on top of the limited load factor that the UK will see overall.

 

[Flyfisher]

Regarding the air car calculations:

It does assume a 100% efficient engine though and 22 horsepower isn't much.

I wonder if 100% efficiency (or very near) isn't unreasonable in this case? The air can only expand within the engine cylinder and if it's connected directly to the drive wheels then surely all the expansion must be translated to rotating the wheels and there's no 'efficiency of burning fuel' type issues to consider. If there are substantial energy losses I'm not clear where they would be (within the car that is, the actual air compression is a different matter)

And yes, 22hp isn't exactly race car performance, but it looks like a lightweight vehicle and I suspect it would be fine for city commuting and general short trips to the shops.

I also sceptical, but I'm more impressed with this than a battery-powered vehicle. If all stated specs turn out to be true I would seriously consider replacing my second car with one.


Regarding wind turbine efficiencies:

Don't get me wrong, I'm not against them, just that we must be sceptical about their claims.

I agree. Exaggerated claims can do more harm than good because when disproved (and there are surely enough actual turbines in operation now that the real operational figures must be known) they can be used to attack the basic honesty and integrity of the claimants, whatever the merit of any other arguments they put forward. In essence, if you can trust them on one thing, why trust them on any other?

(That's not to judge the specific numbers in this case because I don't know).

 

[MdB]

I wonder if 100% efficiency (or very near) isn't unreasonable in this case? The air can only expand within the engine cylinder and if it's connected directly to the drive wheels then surely all the expansion must be translated to rotating the wheels and there's no 'efficiency of burning fuel' type issues to consider. If there are substantial energy losses I'm not clear where they would be (within the car that is, the actual air compression is a different matter)

The equations assume that the air stays at a constant temperature and that the engine block doesn't freeze when the air expands. I would imagine that stopping it turning into a large ice block is quite a problem which will reduce performance. If the air doesn't leave the engine at room temperature then it won't get the full benefit of the stored energy. I also can't believe that any mechanical device is near to 100% efficient.

 

[Penners]

I wonder if 100% efficiency (or very near) isn't unreasonable in this case? The air can only expand within the engine cylinder and if it's connected directly to the drive wheels then surely all the expansion must be translated to rotating the wheels and there's no 'efficiency of burning fuel' type issues to consider.

But you surely can't dismiss friction losses, which will be significant. There's also a little loss of pressure around the piston rings - no compression process is without that, surely?

 

[biffvernon]

Regarding wind turbine efficiencies:

Don't get me wrong, I'm not against them, just that we must be sceptical about their claims.

I agree. Exaggerated claims can do more harm than good because when disproved (and there are surely enough actual turbines in operation now that the real operational figures must be known) they can be used to attack the basic honesty and integrity of the claimants, whatever the merit of any other arguments they put forward. In essence, if you can trust them on one thing, why trust them on any other?

(That's not to judge the specific numbers in this case because I don't know).

Sorry, it's taken me a little while to track down the data but of course it is known. For 2006 all UK mean load factors were:
UK Onshore wind 27.4%
UK Offshore wind 27.2%
Source:
Department for Business Enterprise and Regulatory Reform
That government website has an enormous amount of energy related data.

The figures inculde everything from the infamous Blyth Harbour turbine, which does not actually have a functioning grid connect so achieves a load factor of 0% to the Burradale turbines on Shetland which has consistantly returned a load factor of more than 50% for the last four years, with 58.4% in 2005.

If you want the details the Renewable Energy Foundation has published monthy generation figures for all 181 UK windfarms, from which I am pleased to learn that the windfarm I can see from my bedroom window gave a load factor of 35.8% last year.

Now, what was the problem, Wobs?

 

[Flyfisher]

Regarding the air engine:

I think I read that the exhaust gas was 0 to -15 C, which is expected due to the rapid expansion of the air. I doubt there is a big problem for the engine to work at -15C (guess though). Friction would certainly absorb some of the energy but modern bearings and oils are pretty good these days so would it be a lot? Air leakage around the pistons is certainly one way to waste the work of the expanding gas but if this was a significant problem would ordinary engines work, especially high compression diesel ones?

I, also, don't believe in 100% efficiency but this engine seems like it could be significantly better than most.

Perversely, the faq includes a question about how the car is going to be heated (given there is no waste heat product!) and the answer was that it will involve the conbustion of fuel! Fine for the hybrid car but what about the 'pure' air car?

Still we may not have to wait long for The Stig to give it a workout; summer 2008 is the stated availability date.