Wind Power vs. Solar

Reed_Richards

I have a solar PV installation with 16 x 300 W panels.  My average generation (taking the average for the full 24 hours of a day) over about two years has been around 430 W per hour.  There is obviously no generation when it is dark and not much in the depths of winter, even in daylight.  Is this sort of average power beyond the reach of a modest wind turbine?  I would have thought that I am more likely to have a use for the electricity when the wind is blowing than when the sun is shining.      

ABrass

Domestic scale wind turbines aren't really a thing. Too small and too low down to get decent wind speed.

QrizB

I don't know where you live, either generally or specifically, but the vast majority of UK housing is poorly sited for wind generation. People prefer to live in sheltered valleys and wind turbines prefer breezy uplands. It might be possible but it's unlikely to be economically viable.

It also soundd as though your solar might be underperforming (noting again that I know nothing of your specific situation). What does PVGIS predict for your location?

I see you asked a similar question two years ago:

https://forums.moneysavingexpert.com/discussion/6040086/do-solar-panels-compare-well-with-other-re-options

I don't think the technology or economics of small scale wind generation have changed much since then.

Reed_Richards

ABrass said:

Domestic scale wind turbines aren't really a thing. Too small and too low down to get decent wind speed.

That is exactly the conventional wisdom, but is it true? 

I get approximately 90% of the annual energy predicted by PVGIS.  My roof faces south.  There are trees to the south east and south west which tend to shade the panels in winter but which are too far away to influence the summer result.

South from me is a field, as is west.  South west (beyond the tree) is some scrubby ground with bushes to about head height.  The wind blows predominantly from the south west.  There is a small wind farm about two miles away with only a slight hill between that and my house Perhaps it is the sight of this that prompts me to keep asking the same question; perhaps it is the realisation that my average solar power (over 24 hours) is quite small; perhaps it is the fact that I switched from an oil boiler to an ASHP, causing my electricity usage to take-off?  And when I asked this question two years ago only one person ( @Martyn1981 ) answered.  

Coastalwatch

An interesting topic RR and your location/surroundings suggest one may be viable. Have you looked up wind speeds for where you are which may give a good indication, I believe 4 to 5 metres/sec or approx 12 mph are figures required to make this so.

We live on the coast with ave wind speeds suggesting a turbine would give a useful return, at least sufficient to cover overnight consumption once the house is on tick over. There are a couple of wind farms visible out to sea from here and, a mile or so inland a small holding has a couple of small turbines up running again after a few years of being in a state of disrepair. They are up a fair height, perhaps 30/40ft, but I've no idea how much they generate or how long they might last from now on.

Unfortunately from what I've come to understand the cost, maintenance and lifetime of them, up to now at least, doesn't seem to make for a very good investment. So unless fresh designs or data proving otherwise come to light then sadly I've let go of the idea and invested a sum into Ripples wind turbine, Graig Fatha, to get reduced energy bills from the energy it generates.

The only fresh design I'm aware of recently are the vertical axis turbines planned to be placed alongside motorways to generate energy from resulting air currents as traffic passers. If they prove successful then maybe one might be an option.

Being of a compact design than I might just have room for one of those!

Martyn1981

Reed_Richards said:

I have a solar PV installation with 16 x 300 W panels.  My average generation (taking the average for the full 24 hours of a day) over about two years has been around 430 W per hour.  There is obviously no generation when it is dark and not much in the depths of winter, even in daylight.  Is this sort of average power beyond the reach of a modest wind turbine?  I would have thought that I am more likely to have a use for the electricity when the wind is blowing than when the sun is shining.      

Hiya, the problem is typically turbulence. I've learnt a lot, and none of it good, from the 'experts' on the Navitron forum. Many of the off-gridders have wind turbines, but as I've lurked, and chatted over the last decade, I've noticed how those same individuals have gone PV crazy, singing their benefits.

The problem with wind, is you need to mount the WT quite high up, and ideally with about 200m between it and any ground obstacles in the direction the wind typically blows. This is so that any turbulence has time to settle. Unlike the giant WT's which are mechanically turned to the wind, or best wind direction at that time, the smaller ones typically have tails and turn towards the wind, but if the wind is erratic, then they will constantly 'hunt' and generate very little while they do this.

Then you have maintenace, which is essential. And consideration to the strength/weight of the WT, do you go for a light one that spins easily, but may fail in strong winds, or a stronger, heavier, shorter bladed one, that might generate less or nothing at low speeds, but will at least survive. For off-gridders there was also the issue of lowering WT's, or applying brakes, in advance of a storm, since stopping them at 100%+ of rating could be difficult, and dangerous. And if a WT is spinning, then you have leccy, even if you don't want it*, so to protect batts you may have to switch on 'dump loads' (such as leccy heaters) to use up the leccy. Whereas, of course, a PV inverter can move the tracker away from the maximum power point, to effectively generate zero, even in strong sun, so can work well with battery management equipment.

*You can't just disconect them from the grid/batts, as they would then overspeed and destroy themselves without the load restriction.

A popular name that was available in B&Q's etc, now has a nickname with three extra letters inserted into its original name - swindlesave - as generation was so low, that some actually consumed more power through their inverter, which runs 24/7, than they generated, but others did manage to generate ~£20 pa..


I don't like it when people are unfairly negative, but it seems that the practical and economic issues regarding WT's and urban/suburban housing are too difficult ....... something I was really sad about, as like you I thought that a small WT, even if only 200W, would be perfect in combination with PV and batts.

The solution to many of the problems with conventional HAWT's (horizontal axis wind turbines) in an urban environment, might be a VAWT (vertical axis), but again, a point that comes up from the 'experts' is that a WT can only generate energy from the wind that hits it, and  whilst VAWT's look cool, and always promise a lot, they typically have much, much smaller swept areas than HAWT's, which might be why they never seem to deliver on their promises, as they are simply too small. However, the economic argument for the VAWT's Coastalwatch has mentioned, seem interesting, as they piggy back off existing supports and leccy connections (one example being motorway lamposts), but the lease cost (aparently you can't buy them) still seems to run into many 10's of thousands each over 25yrs, which confuses me greatly.

QrizB

Reed_Richards said:

I get approximately 90% of the annual energy predicted by PVGIS.  My roof faces south.  There are trees to the south east and south west which tend to shade the panels in winter but which are too far away to influence the summer result.

South from me is a field, as is west.  South west (beyond the tree) is some scrubby ground with bushes to about head height.  The wind blows predominantly from the south west.  There is a small wind farm about two miles away with only a slight hill between that and my house Perhaps it is the sight of this that prompts me to keep asking the same question; perhaps it is the realisation that my average solar power (over 24 hours) is quite small; perhaps it is the fact that I switched from an oil boiler to an ASHP, causing my electricity usage to take-off?  And when I asked this question two years ago only one person ( @Martyn1981 ) answered.  

When you had your solar PV installed, did your installer seek permission from your DNO for a higher export value? If not, you may have been limited to a 3.68kW export and your installer would have limited your generation to match. This is a bit small for a 4.8kWp installation IMHO and would go some way to explaining your 10% deficit vs. PVGIS. You may be able to reverse this if you speak to your installer.

You have said that you're in the North of England. I had a quick look on the MCS website and there are a handful of wind generator installers in that general region. Perhaps you could contact them and see what they think of your property as a site for a generator, and whether they would quote to install one? (Apologies if you have already tried this.)

Reed_Richards

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.    

QrizB

Reed_Richards said:

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. 

I used to do a lot of sailing and hope to get back to it one day. Electricity on yachts is expensive to produce and store, and is a carefully managed resource. If running an engine or generator to produce electricity, my rule of thumb was always one litre of fuel per kilowatt-hour, an effective price these days of £1.20/kWh. Also, yachts have tiny electrical demands (less than 1kWh per day), are used for less than 100 days a year, and spend most of their lives in windy places. A small wind generator that generates 100kWh per year is worth having even if it costs £300 as it offsets fuel costs and engine wear (plus stops your batteries going flat and dying in-between trips).

[EDIT: I see the Rutland 504 is closer to £400 now.]

At home, even if your house is as windy as a yacht mooring, you might want 30x as much electricity (8-10kWh per day, 365 days per year) but it's worth 1/10th as much to you; between 5p (export) and 15p (import). The economics rarely make sense.

If you can get a grid connection to a yacht, you don't bother with a wind generator. Yachts that are kept in marinas, where there is usually a mains hook-up at the dock, rarely have wind generators for that reason.

Unlike wind, the majority of UK housing gets some usable sunshine so solar PV has achieved good market penetration, while domestic wind hasn't.

Reed_Richards

Thank you, @QrizB, your perspective as a sailor is very interesting.

Martyn1981

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. 

Have to say I'm a bit confused by that. Are you suggesting that they work co-operatively, as I understood it to be the exact opposite, and that they have to be placed apart to stop the turbulence from one affecting another, and also because they will reduce the power of the wind behind them.

If you look at the rollout of WT's over time, you'll see them getting further and further apart as they got bigger, so as not to 'steal' the wind from the nearest neighbour. We see a tiny number of giant (MW) WT's, being used to replace 100's of small (kW) old WT's in some places around the World.

Also the calculation of energy from wind generation includes v3, as in the energy cubes with the velocity of the wind. Twice the wind speed means 8x the energy (up to the rated power of the WT), so it's really, really important, not to have one WT impacted negatively by another.

The single biggest problem for WT's is economies of scale, or, since we are discussing small WT's, diseconomies of scale. My sister has a small holding, and is having ~9kWp of PV installed for about £8k. She's been quoted £15k+ for a 2kW WT, mounted approx 10m. Assuming it works really well and gets a cf of 20-25%, then it will generate approx 2 or 2.5x as much leccy as the PV per kWp, so let's say it's equal to 5kWp, so roughly 3x the cost of PV. But whereas the PV should be good for 30-50yrs, the WT will probably be good for 20yrs and require maintenance. So that idea has been dropped, and I suggested she invest the money in a large windfarm, and switch to a green tariff as soon as they are out of contract.

Now, take that WT at £15k, and imagine 1,000 of them, so ~£15m, or a single 2MW WT, costing around £2m, and we see how economies of scale are almost perfect for wind. [Note, the 2MW turbine doesn't actually need to be 1,000 times larger than each 2kW model, as it will be operating at a greater height, benefitting from stronger winds that are also less turbulent, and more consistent.

Then consider PV, a panel on your roof, or in a massive PV farm, and it will be pretty much exactly the same product, so there are almost no economies of scale with PV (not to be confused with economies of volume (or buying power) where a lower price can be negotiated for bulk purchases). This isn't a negative for PV farms, as PV is so, so cheap, but it's a massive benefit for small domestic arrays, as they don't suffer the diseconomies of scale of going small.

[And then on top, you also have to consider other factors, such as lower CAPEX / higher OPEX for a PV farm, and also the value of the product at the location, as QrizB explains, giving higher value (retail pricing) to a domestic wind/PV generation, v's supply side wind/PV generating at wholesale prices.]


[Edit - I sincerely hope none of this comes over as my being negative about wind power. My thoughts opinions are directly related to my own disappointment levels at not being able to find a domestic wind power solution for my suburban house. M.]