Wind Power vs. Solar

michaels

Reed_Richards said:

I cannot help but think that current wind turbines are based on windmills and if you had a windmill then you could mill all the grain in the area so didn't need another one for a few miles.  Thus the turbines in wind farms are placed far enough apart that they don't interact whereas what you need for maximum efficiency are turbines that are closely spaced but interact in a co-operative manner so you don't lose most of the wind energy passing by.  You don't see small water-driven turbines in the middle of a wide river, you dam the river and drive the turbine with the entire flow.  However a co-operative array of small turbines along the ridge of your roof seems to be an idea that only exists in my head so far.

You see huge wind turbines in wind farms (my local turbines have tails by the way) and tiny turbines on yachts, it has always puzzled me that intermediate size turbines for houses are so scarce.  But I concede that by the time you have avoided turbulence and complied with planning constraints you have probably eliminated a large number of domestic premises, possibly my own included as I see that siting the turbine on the boundary next to the field would not be allowed.

Thanks for everybody's comments; It looks as if I may need to forget this idea for another couple of years, although I will have a look at the MCS website just in case.    

Or perhaps not only in your head:
https://electrek.co/2021/05/04/egeb-vertical-wind-turbines-oxford-brookes/
Basically horizontal turbines generating more power because they form part of an array....

Reed_Richards

Thinks for this @michaels; you can actually read the full publication here: https://www.sciencedirect.com/science/article/pii/S096014812100344X  .  @Martyn1981 had more or less convinced me that I had taken leave of my senses so I would be interested in his evaluation of why this scientific paper is wrong.

QrizB

Reed_Richards said:

... I would be interested in his evaluation of why this scientific paper is wrong.

I clicked through and read the paper. There are a couple of things that are missed by the news article:

• VAWTs are intrinsically less efficient than HAWTs. The paper says as much; HAWTs are ~50% while VAWTs are 35-40%.
• The paper doesn't seem to state efficiencies in absolute terms, only relative ones. It therefore hard to say whether these VAWT arrays are better than HAWTs, or just less worse.
• When the wind is in-line with the VAWTs, or +/-30 degrees, there's an efficiency "hole" where the output falls (at worst) about 30% of the single VAWT figure. This could be a problem for larger arrays than 2 VAWTs where there are multiple alignments.
• One of the paper's conclusions is "the total efficiency increased as the turbine spacing increased" which seems a little odd when compared to the headline.

I guess more work (and more funding) is required ...

Martyn1981

Reed_Richards said:

Thinks for this @michaels; you can actually read the full publication here: https://www.sciencedirect.com/science/article/pii/S096014812100344X  .  @Martyn1981 had more or less convinced me that I had taken leave of my senses so I would be interested in his evaluation of why this scientific paper is wrong.

My apologies, I was completely wrong, I genuinely believed that you had decided to stop misrepresenting what I (and you) had posted. Silly me.

Now, on to VAWTs, I thought I answered your post 7hrs before you made it? Didn't I?

Rather than pretending I've said something I haven't, why don't you address the real issue that I and others have repeatedly raised, but you've constantly ignored - Will any of your ideas be more economical than the current system of WT's and their deployment? Will your ideas even be economical? [Hint - have you considered the cost of all those monopiles needed to create that VAWT farm, the total amount of energy within that area, and then compared it to the far greater amount of energy available to a smaller number of giant HAWT's spread out as per the experts scientific calculations?]

Lastly, I genuinely believe that your heart is in the right place. So stop trying to stir and make up false arguments.

Reed_Richards

First back to basics.  My solar panels average about 430 W and I am given to understand would cost about £5,000 today so that is £11.50 per Watt.  I would like to achieve wind power at my home for a similar price.

The average Wind speed in my area appears to be about 25 km/h which is about 9.6 m per second or about 18.7 knots.  It I take the Rutland 504 https://www.marlec.co.uk/product/12v-rutland-504-windcharger/#1439303689503-ca1e0ecc-5b43 as an example of a small (0.51 m diameter) conventional wind turbine it would give about 20 W at 18 knots and costs £390.  That's about twice the price point I am looking for, not to mention the cost of the mounts and inverter.  Inverters designed to run off a 12 V battery cost anything from £30 up; I haven't researched how fancy a one I would need.

I would have to mount it on the ridge of my roof.  I can't help feeling it should be possible to use this to my advantage by catching the wind as it hits the roof and is directed upwards over the ridge but I think a conventional HAWT would be hindered rather than helped.  And how noisy would it be? 

20 W alone isn't worth worrying about although I could aspire to more in winter when winds are stronger.  But is it really beyond the bounds of possibility that we could go from where we are today to something that is economically viable and which we could use in multiples rather than singly?

QrizB

Reed_Richards said:

The average Wind speed in my area appears to be about 25 km/h which is about 9.6 m per second or about 18.7 knots.  It I take the Rutland 504 https://www.marlec.co.uk/product/12v-rutland-504-windcharger/#1439303689503-ca1e0ecc-5b43 as an example of a small (0.51 m diameter) conventional wind turbine it would give about 20 W at 18 knots and costs £390. 

I'm not sure quite how you did your wind speed conversion but 25km/h is only 6.9m/s or 13.5 knots, at which speed the rutland 504 generates 10 watts (£39/watt). The Rutland 1803 would generate maybe 150 watts at that wind speed (and a maximum just shy of 1000 watts) but is £2400. I don't know if you can drive a conventional solar grid-tie inverter directly with one of these, or if equivalent wind power inverters exist, but a 1Kw solar inverter is around £250. That's a total of £2650, or £17.67 per watt for the major system components.

What we've not considered yet is fitting and all the cables/switches/brackets. The £5k price for a PV system like yours is fully fitted; parts are roughly half the cost (Bimblesolar is offering 410w panels at £149 each (x12 = £1788) and a selection of suitable inverters around £500, so ~£2300 for parts). So for the *parts* price of a single Rutland 1803 you could buy the *parts* for a 5kWp solar PV system, with change.

Martyn1981

Reed_Richards said:

20 W alone isn't worth worrying about although I could aspire to more in winter when winds are stronger.  But is it really beyond the bounds of possibility that we could go from where we are today to something that is economically viable and which we could use in multiples rather than singly?

I hope it's possible, and as I mentioned right back at the start, VAWT's aren't new, nor magical, so the technology exists.

So the problem, as you now agree is 'economicaly viability', and that's the big hurdle. As QrizB points out, the numbers don't seem to add up, and something I mentioned in the same early post (29/4) is that you also have to take inverter energy consumption into account, as the wind can of course be 24/7, hence why you see SMA Sunny Boys (PV) and SMA Windy Boys (wind).

Then there are other issues such as NVH (noise, vibration, harshness) which need to be considered for HAWT's on poles mounted directly to houses, which can be unacceptable. I don't know if individual VAWT's are better (or worse), but either way, I'd expect 10 to be interesting!

Moving on to multiples of VAWT's, every atom of my body assumes (only an assumption) that you will be increasing outlay and complication, for ever diminishing returns, as you add more. I'd have thought that 10 small VAWTS lined up on a house roof, let's say 300mm wide and 500mm tall, giving you a total area of 1.5m2, would cost far, far more than a single small HAWT with a corresponding swept area. 

Then how will the generation work, will each generate independently (10x the motors), or some complex mechanical system linking individual shafts to a linked shaft to a single motor? 

What about the roof works needed? Having helped to build a side extension, I was surprised at just how much ironmongery such as roof straps was needed to hold the wall plate down, or to link the first 3 rafters to side walls. Holding up a roof is easy, the weight is transferred by the rafters to the wall plate, purlins etc and then sits in compression on the main structure walls, so easy to calculate roof weight plus snow load and build accordingly. But wind lift is another beast alltogether and takes serious consideration, and rooves are built to minimise wind lift, even PV needs to be kept away from edges to avoid wind lift. So how much work and expense will be needed to strengthen the roof/ridge, not to hold up the VAWTs, but to prevent them from damaging the roof structure - note if you want to take energy from the wind, then your WT has to stay in place, not be blown over/away.

So could it be done, maybe, but since this is not a new idea, and many types have been tried before and failed, history suggests that it's unlikely, and whilst this doesn't prove it's not possible, it certainly hints quite loudly.

Reed_Richards

QrizB said:
I'm not sure quite how you did your wind speed conversion but 25km/h is only 6.9m/s or 13.5 knots, at which speed the rutland 504 generates 10 watts (£39/watt). 

I did it too late at night, obviously.  I knew I should divide by 3.6 to convert km/h to m/s so I must have typed a wrong number into my spreadsheet and I suppose my critical faculties must have already gone to sleep or I would have noticed.