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  1.  
    Not too much chat on here about wind turbines? What is the consensus?

    House previously mentioned in another thread, is on top of a hill and apparently gets a higher than UK average of wind in that area ( :cool: ), so possibly considering one as part of overall energy strategy. Use to supplement PV and top up batteries in dark/quiet hours sort of thing.

    There is a suitable un-constricted location for a WT

    Comments? Any particular WTs that are good? Or not?
    • CommentAuthorringi
    • CommentTimeNov 23rd 2016
     
    If you are on mains electric you will get a better rate of return investing in a company that builds large wind turbines. If you double the size of the turbine you get about 4 times as much power. see http://www.solacity.com/small-wind-turbine-truth/ for a lot more information.

    If you are "off grid" and can not connect to the grid, then a turbine can make sense, but most of us are on grid hence we don't have them. If I was putting in an off-grid system and the site was good for a turbine I would be sizing the system based on wind, and then only adding PV if they reduced the size of batteries I needed.
    • CommentAuthorMarkyP
    • CommentTimeNov 23rd 2016
     
    interested to follow this one. We live on an elevated, open aspect 3 acre plot and get a good unobstructed SW breeze most days. I had considered a wind turbine as a nice DIY project, inspired by various efforts I read on the Navitron forum, but I believe it's only permitted development to install a turbine up to a certain size if it's MCS (is that the right body?) installed/certified so sort of parked the idea. Didnt look into whether there's scope to get some DIY lash up certified, I rather doubted it.
    •  
      CommentAuthordjh
    • CommentTimeNov 23rd 2016
     
    What ringi said, plus hydro is even more consistent if you have a stream.

    If you seriously consider a wind turbine, I would suggest asking advice from the Navitron forum.
  2.  
    Knowledge is power - never come across Navitron </fires up google> - thanks

    We do have a stream but I don't think it'll get enough head to power more than an LED bulb. I will try and measure the drop to see if damming it would make it worthwhile.
    • CommentAuthorEd Davies
    • CommentTimeNov 23rd 2016
     
    Posted By: ringiIf I was putting in an off-grid system and the site was good for a turbine I would be sizing the system based on wind, and then only adding PV if they reduced the size of batteries I needed.
    I will be putting in an off-grid system and the site is good for a turbine (brow of a hill 100 m above sea level overlooking the Moray Forth). The basic power source will be PV (starting at about 6 kW, plus 8x20x47mm evacuated tube solar thermal mostly for space heating) then I'll see what more is needed. Perhaps more PV, perhaps a turbine but turbines are hassle which I'd rather avoid.

    Also, I don't know of a suitable turbine. AFAIK, the smallest which would be guaranteed for a high-wind site would be a Kingspan 3.2 kW which is bigger and more expensive than what I'd want. I'd be looking for something around 1 kW or a bit less.
    • CommentAuthorringi
    • CommentTimeNov 24th 2016
     
    I expect you will need a lot more PV to cope with the 3 months of low output if you just use PV. With the amount of excess power you will have for most of the year, maybe you should do something like setup a kilm to dry logs, so you can sell some of the power.....

    I have not looked at the output of PV on a none shaded site when mounted near vertical, maybe putting PV on a south facing wall would give better output at the times it is needed most.

    It would be interesting to know the numbers with a Kingspan 3.2 kW with and without a heat pump, without any solar. However a generator with heat recovery may be the most cost effective option for the dark months as I expect most people will want some sort of generator anyway.
    • CommentAuthorbillt
    • CommentTimeNov 24th 2016
     
    Posted By: ringiI have not looked at the output of PV on a none shaded site when mounted near vertical, maybe putting PV on a south facing wall would give better output at the times it is needed most.


    PVGIS will give a pretty good indication if you put in the right figures. When I was planning my systems I used it for trying lots of different panel angles, and what it demonstrated was that you get bugger all output in the winter (Nov-Jan) whatever the panel angle. You can't avoid the effects of very short days and cloud.

    One thing that you can do with panel angle is flatten the monthly average. With a low angle you will get a big peak in the summer months; a steep angle gives 2 peaks in spring and autumn with a dip in summer. Get it just right and the average is fairly flat from April to September (within the constraints of the great variability of PV output due to weather).
    • CommentAuthorringi
    • CommentTimeNov 24th 2016
     
    Posted By: billtOne thing that you can do with panel angle is flatten the monthly average. With a low angle you will get a big peak in the summer months; a steep angle gives 2 peaks in spring and autumn with a dip in summer. Get it just right and the average is fairly flat from April to September (within the constraints of the great variability of PV output due to weather).


    Do you get better results having all the panels at the same angle, or putting each string at a different angle?
    • CommentAuthorEd Davies
    • CommentTimeNov 24th 2016
     
    Posted By: ringiI expect you will need a lot more PV to cope with the 3 months of low output if you just use PV. … I have not looked at the output of PV on a none shaded site when mounted near vertical,
    If you looked you might be surprised. 6 kW on my 60° roof would, according to PVGIS, produce very nearly my current electricity usage in December (worst month) at 4.27 kWh/day vs my usage over the last twenty days of 4.4 kWh/day. Pre-heating my shower water with solar thermal to halve the amount used for that would fill that gap (I estimate 0.8 kWh/day for showering).
    •  
      CommentAuthordjh
    • CommentTimeNov 24th 2016
     
    Posted By: Ed DaviesIf you looked you might be surprised. 6 kW on my 60° roof would, according to PVGIS, produce very nearly my current electricity usage in December (worst month) at 4.27 kWh/day vs my usage over the last twenty days of 4.4 kWh/day.

    Just FWIW, my 4 kWp has been giving nothing like 2.8 kWh this month. But maybe it's just been exceptionally grey.
    • CommentAuthorringi
    • CommentTimeNov 24th 2016
     
    PVGIS gives the average case, but for off grid you care about the worse case.

    Assuming you can store 7 days worth of electric then you need to show that there is less then say a 1 in 25 year chance of not getting enough PV output in any 7 days….

    Adding wind power reduces the probability of not having enough power a lot more the doubling the size of a PV array. (Your solar thermal setup is likely to fail at the same time as the PV is not giving enough power, so does not spread the risk.)

    Unless you put in a generator that is designed to cover a few weeks of usage every year…..
    • CommentAuthorbillt
    • CommentTimeNov 24th 2016
     
    Posted By: ringi
    Do you get better results having all the panels at the same angle, or putting each string at a different angle?


    No idea, it's not something that occurred to me and falls into the class of extra complexity with little prospect of useful gain. If you really want to maximise production from PV you'ld use a tracking system, but they don't seem to be worthwhile in terms of cost and reliability.

    My 3.8kW system has averaged 3.8kWh/day so far this month, but only 1.62kWh/day over the last 5 days. Over the summer (April-September) it managed 14kWh/ day with 16kWh/day in May.

    Ed's usage must be exceptionally low for a 6kW array to meet his needs in winter and that means that he will be overproducing grossly in the summer. You've still got the same issue that you have if you try to become self sufficient with more normal rates of consumption: the capital cost of the equipment enormously out weighs the value of the energy that you will be using.

    As Ringi says, a small PV system with a generator is probably the optimum if you want to go off-grid, especially if you have the option of a complementary source like wind or water when you may only need the generator for a day or two a year.
    • CommentAuthorskyewright
    • CommentTimeNov 24th 2016 edited
     
    Adding wind power reduces the probability of not having enough power a lot more the doubling the size of a PV array.

    But wind also significantly increases the complexity of the system (it introduces moving parts, and those moving parts are necessarily exposed to the worst the weather can throw at them).
    • CommentAuthorringi
    • CommentTimeNov 24th 2016
     
    Posted By: skyewright
    Adding wind power reduces the probability of not having enough power a lot more the doubling the size of a PV array.

    But wind also significantly increases the complexity of the system (it introduces moving parts, and those moving parts are necessarily exposed to the worst the weather can throw at them).


    Any off-grid system will a high level of complexity and/or cost unless you have your own river.
    •  
      CommentAuthordjh
    • CommentTimeNov 24th 2016
     
    Posted By: ringiDo you get better results having all the panels at the same angle, or putting each string at a different angle?

    Depends what you mean by 'better'. The yield is fairly insensitive to the exact angle, but large angle differences can make a difference. There will be an 'optimal' angle at each place that gives the greatest annual yield, but if you accept a lesser total annual yield you can increase the yield at particular times of the year, for example, or get a better average over three seasons perhaps.

    The main complication is that panels at different angles have different performance so they need to be on a separate 'string' from the inverter (or use microinverters).
    • CommentAuthorringi
    • CommentTimeNov 24th 2016
     
    Posted By: djhDepends what you mean by 'better'.


    Lowest cost for a system that will give enough electric every day, with no more then x power cuts over the next 10 years.
    • CommentAuthorskyewright
    • CommentTimeNov 24th 2016 edited
     
    Posted By: ringiLowest cost for a system that will give enough electric every day, with no more then x power cuts over the next 10 years.

    For 'best for off grid' I can't see any advantage in multiple vertical angles.

    The way I see it is...

    Choose an angle that is optimum for when the sun "starts working again" (the angle & timing will be different in different location).

    Nearer the summer from that you'll (on average) have more than you need, but that's not a problem.

    Nearer the winter than that and you'll often not be getting much whatever the angle.

    Any panels at different angles will be under performing just the point where production is marginal.

    That assumes the whole array is facing due S.

    If multiple directions is also a possibility, other considerations might apply (including the local horizon).
    • CommentAuthorEd Davies
    • CommentTimeNov 24th 2016
     
    Posted By: skyewright
    Adding wind power reduces the probability of not having enough power a lot more the doubling the size of a PV array.

    But wind also significantly increases the complexity of the system (it introduces moving parts, and those moving parts are necessarily exposed to the worst the weather can throw at them).
    This is exactly the dilemma: my prejudice is to avoid turbines if possible - they're hassle. On the other hand, their generation does tend to complement PVs.

    Posted By: djhJust FWIW, my 4 kWp has been giving nothing like 2.8 kWh this month. But maybe it's just been exceptionally grey.
    What angle are your panels? Dropping mine from 60°to 30°in PVGIS drops the December daily production from 4.27 kWh/day to 3.09 kWh/day.

    In theory increasing the angle to 90° increases the production to 4.36 kWh/day for December. However, I think that'd also likely increase the day-to-day variation even more as it'd make less use of light from a hazy sky. I picked my angle by the highly scientific method of waiting for a lightly cloudy day (one where it was just about possible to see where the sun was), shorting a panel through an meter on the amps range and wobbling the panel up and down to get maximum current.
    •  
      CommentAuthordjh
    • CommentTimeNov 24th 2016
     
    Posted By: Ed DaviesWhat angle are your panels? Dropping mine from 60°to 30°in PVGIS drops the December daily production from 4.27 kWh/day to 3.09 kWh/day.

    Don't know exactly but they're fairly flat (and at multiple angles, with microinverters) so perhaps that accounts for it.
    • CommentAuthorskyewright
    • CommentTimeNov 25th 2016 edited
     
    Posted By: djh
    Posted By: Ed DaviesWhat angle are your panels? Dropping mine from 60°to 30°in PVGIS drops the December daily production from 4.27 kWh/day to 3.09 kWh/day.

    Don't know exactly but they're fairly flat (and at multiple angles, with microinverters) so perhaps that accounts for it.

    It's an aspect of 'weather', so location can make a very big difference to a given day/week/month.
    There 's a topic on Navitron just now with people commenting that Monday 21st Nov was particularly bad. However, here on Skye (similar latitude to Ed, but West side rather than East) the 21st was a 300% of PVGIS, blue sky pretty much dawn to dusk, day.

    Edit to add: Panels at ~45° facing WSW.
    • CommentAuthorMHicks
    • CommentTimeNov 27th 2016
     
    We're off-grid in a caravan at our plot and will stay that way after the house is finished. The nearest mains connection is a half-mile away and after living unplugged on a boat for a few years being off-grid seemed like a no-brainer. We have just 2kW of PV at the moment (increasing to 6kW when the garage is built), plus a 600W wind turbine.

    I find on the darkest, crappiest days our PV makes <100Wh, an almost neglible amount of juice. The array isn't as optimally located as it will be (temporary position with an ash tree shading for part of the morning) but I don't expect much improvement when it's on the S-facing garage roof - I live in Wales. As often as not at this time of year when the weather is gloomy the wind is blowing and we find the turbine - even though it's a relatively small one - more than meets our demand, producing 100-150W at 15knots BUT (and this is the key point during the dark season) for 24 hours a day, wind permitting.

    We leave the turbine 'turned off' for the majority of the time - output shorted so blades stationary or gently rotating - and let it run just when the PV needs some help.
    • CommentAuthorEd Davies
    • CommentTimeNov 27th 2016
     
    MHicks, interesting: which turbine do you have? How well does it stand up to lots of wind? Do you have to mechanically brake it when it's too windy?
    • CommentAuthorMHicks
    • CommentTimeNov 27th 2016
     
    Posted By: Ed DaviesMHicks, interesting: which turbine do you have? How well does it stand up to lots of wind? Do you have to mechanically brake it when it's too windy?


    An LE-600. So far it's stood up to 60kn gusts without mishap. It is not ideally located (much like our solar panels!) with a tree 10m away to the E, woods 30m to the NW and continuing round to the NE and whilst it has cleaner air from the SE to W the turbine is too low relative to the ground in that direction which means the airflow is more turbulent than ideal. We wouldn't be without it though, it contributes significantly to our needs when we need it most.

    The turbine is pretty substantial and well built but I would probably tether it with more than 50kn forecast. I've done that once - I 'stopped' it electrically and then popped up the pole with a bit of cord. It would be problematic doing that DURING very high winds - the company told me not to stop the turbine electrically (by shorting the three outputs) in strong winds as the coils can overload and burn out - and you wouldn't want to go near the thing with spinning blades...
    • CommentAuthorEd Davies
    • CommentTimeNov 27th 2016 edited
     
    Thanks. The LE-600 is one I had in mind for a while, until they changed their warranty to not include damage by strong winds. I think it used to be specified as 25 m/s. If so, they've reduced it even more, now:

    What is not covered by your warranty?

    · Damage due to high winds and storm conditions (17m/s+, 40 mph+).
    Got 20 m/s forecast for Wednesday - that's not uncommon around here.

    Posted By: MHicksIt would be problematic doing that DURING very high winds
    Exactly. Playing guessing games with what the wind could get to over the next few days is not something I'd want to be fretting about which really puts me off.
    • CommentAuthorringi
    • CommentTimeNov 27th 2016
     
    What about a “vertical wind turbine”, e.g. http://www.ecopowershop.com/wind-turbines/Vertical-Wind-Turbines/LE-v150-small-vertical-wind-turbine-by-Leading-Edge or http://www.windtrap.co.uk/maglev-darrieus-art-3kw-vertical-wind-turbine-48v-443-p.asp
    • CommentAuthorEd Davies
    • CommentTimeNov 27th 2016
     
    Be interested to see actual data from a successful vertical-axis turbine installation. Maybe I'm out of touch but I've not heard of one yet. It might well be that part of the problem is that they get sold to inappropriate locations but still …
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 27th 2016
     
    • CommentAuthorMHicks
    • CommentTimeNov 27th 2016
     
    I'm sure I read that vertical axis turbines are self limiting in high winds, something to do with their aerodynamics. Does anyone make a higher output vertical though?

    As far as the LE-600 and damage in 'high winds and storm conditions' above 40mph (????) - that's pretty lame. I do rate the LE-600 though, the downwind configuration makes it unobtrusive and - I think - quite elegant. It's also solidly built (and as an ex-blue water sailor I've seen and discussed many, many small turbines over many rums on many boats.).

    The Leading Edge website claims 'Peak output: 750 watts @ 18m/s (40mph)' and that, in my experience, is rubbish - I've never seen more than 500W and that was in pretty strong winds. Maybe it's my site.
    • CommentAuthorringi
    • CommentTimeNov 27th 2016
     
    Posted By: Ed DaviesBe interested to see actual data from a successful vertical-axis turbine installation.


    Mostly they seem to be used where some power is needed, but easy of setup is of is more important then getting as much power as possible.

    Posted By: MHicksThe Leading Edge website claims 'Peak output: 750 watts @ 18m/s (40mph)' and that, in my experience, is rubbish - I've never seen more than 500W and that was in pretty strong winds. Maybe it's my site.


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