That’s the snow, ice, hail and rain away for a while, which was perfect timing for today’s task, erecting the wind turbine The Proven 2.5kW turbine that I’d rescued from a Yorkshire veg patch 12 months ago was at last ‘going up’. Even though it was eight years old it had been installed in such a poor site that it had done little work and was to all intents and purposes ‘as good as new’. However as it was going to be supplying power to Sonas well into my retirement I’d decided to completely refurbish it. My intention had always been to replace the ‘spring set’ with the later version as it has a stronger mounting system than the earlier versions.
The Proven 2.5kw is the Land Rover of the wind turbine world, solid, clunky and easy to repair, I’ve not spent a penny on mine in nine years, though it has broken a few springs and mountings. Nothing crucial and I’ve always managed to effect repairs with the minimum of ‘down time’, but I’m looking to the future with this one and it has a couple of major differences. Firstly it’s on an 11m mast as opposed to the 6.5m mast of my old one so this makes it a much heavier lift. Secondly it is the ‘grid tied’ 300v version and not a 48v ‘battery charger’, a strange choice for someone ‘off grid’ you may think. However the high voltage grid tied version has several major advantages over the 48v and 24v models.
For a start they are much easier and cheaper to find second hand as they’re not eligible for the ‘feed in tariff’ and many were fitted in totally unsuitable places. This means they often cost more to maintain than they produce in revenue so owners are keen to get rid of them. My purchase from Yorkshire being a prime example of this. Also, due to the higher voltage they produce more power and with the later carbon fibre blade set can push out 3.2kW. Battery charging versions are harder to come by second hand, mainly because people ‘off grid’ tend to put them in the right place to start with and rely on them for electricity and don’t see them as an income.
However, what most folks ‘off grid’ don’t realize is that you can use any ‘grid tied’ turbine or solar array ‘off grid’ by ‘AC coupling’ it into your ‘mini grid’ via a regular GTI (grid tied inverter’). This is exactly what I did with my hydro turbine some years ago and it works a treat.
I decided to opt for the GE version (grid enabled) http://www.powerspout.com/powerspout-ge40/ . This model works at voltages of up to 400Vdc and is designed for those who wish to feed into the grid via a standard ‘grid tie inverter’ but of course I’m not actually on the grid 😦 Fortunately the ‘off grid’ inverter that currently supplies our house, a Trace SW4548e is capable of ‘back feeding’ any surplus power into the battery bank. Trace don’t tell you this and if you have no means of regulating your batteries state of charge they will cook, but it is, in theory at least possible to connect a standard GTI (grid tie inverter) into your ‘AC bus’, use the power produced and then charge you batteries http://currentgeneration.co.nz/site/current/files/Partial%20AC-coupling%20in%20Minigrids.pdf .
This is exactly what SMA do with there ‘Sunny Island’ system using a slight shift in grid frequency to allow the various inverters to ‘talk to each other’ and control battery SOC.
Designing off-grid wind and solar installations differs from grid tied installations in a number of important ways such as:
- The solar array must be in a certain restricted voltage range
- The solar and/or wind generator must be kept very close to the battery bank
- Expanding the system in the future can involve complex wiring
SMA has addressed many of these issues in their Sunny Island product range by offering a unique system configuration where all power generation sources can be connected directly to the AC bus as illustrated below:
The system certainly is innovative and offers a number of advantages over traditional DC coupled systems, but there are potential downsides too.
In this article, I’ll explore the advantages and disadvantages of AC side coupling using the Sunny Island and Sunny Boy with more traditional DC side coupling using the Outback MPPT charge controller.
And I’ve just lifted the above from StephenDV’s excellent blog http://www.casanogaldelasbrujas.com/blog/2009/05/13/sma-sunny-island-ac-coupling/ to save me waffling 🙂
There are however some serious disadvantages to ‘AC coupling’ over the more traditional method of charging batteries.
1- It’s not as efficient if you’re storing the power due to the ‘double conversion’ of AC to DC and back again, though it is more efficient if you ‘use as you produce. This makes it more suitable for wind and hydro than PV.
2- If you are buying the kit new it is generally more expensive, however with the rise in popularity of PV, bargains can be had and grid tied kit tends to be more reliable.
3- Unless you buy into one particular manufacturer like SMA where the products ‘speak to each other’ you do need alternative ‘charge control’ to prevent your batteries cooking.
4- It’s far more complicated.
It’s main advantages are that it enables you to have your ‘inputs’ anywhere in your ‘mini grid’ without the need for expensive cabling and it gives you a much wider range of operating voltages. So, if you have a regular house with PV or wind turbine close by then it makes little sense. However if you find £3k worth of wind turbine for £800 you’d be stupid to pass it by
Kingspan or Proven
Anyway, the latest carbon fibre blades and spring set arrived in the back of Phoebe last night and I was up long before daylight and off to Arnish to start work on fitting them.
The first part of the job I’d already done almost a year ago. As the new spring set uses M10 studs instead of lighter M8 ones I’d already ‘prepped’ the steel backplate with a 10mm hole. As the holes in the hub are only 8mm you need to drill them out to 10mm, trouble is that you cannot get a drill in there. So, what I did when the turbine was in my shed last February was pre drill the backplate so I could drill it from the inside of the turbine All you have to do is carefully measure 68mm from the outside edge of the backplate and drill a 10mm hole, then if you ever need to replace the spring set you can can just bore the hole like the picture on the right.
Here you can see the old pressed yolk with 8mm studs and the later cast one with 10mm studs and a locating peg. Just to be clear here, the earlier ones are still serviceable but after fitting a new set to my old turbine I noticed a huge increase in performance.
Here you can see the different profile of the older polypropylene blades and the newer carbon fibre, which is much lighter and slender in width. Again, the older blades are still serviceable, I’m just ‘thinking ahead’ only now I’m not sure if I’ve got a Proven 2.5 or KW3 wind turbine. Much as I regretted the demise of ‘Proven Energy’ at the time, I must say that the new owners are ‘streets ahead’ in the after sales service department. I contacted them last week http://www.kingspanwind.com/ paid by BACS and the gear arrived yesterday, well packed and with a few extra fasteners
Raising the turbine
After repairing some storm damage on a friends shed and having a strong black coffee with the new neighbours, all before 8:00am, I headed up to the ‘chooks’ prior to ‘getting stuck in’.
As all the fasteners are stainless steel and have to go through rubber, polypropylene and steel I always coat them in silicon grease.
The grease eases the passage of the studs and bolts and stops them ‘galling’ http://en.wikipedia.org/wiki/Galling.
It’s also far easier to screw them in than batter them with a rubber hammer!!!
With the blades and springs fitted I set up the Tirfor for the ‘big lift’, having previously drilled and pinned the rock to take an anchor point.
Then it was the long hard slog
and, of course, the moment I got the Kingspan/Proven up, the wind dropped to nothing
And it looks like it’ll that way for a day or two, ‘just typical’!!!!!!!!!!!!
Morningstar charge controllers.
As I said earlier, ‘AC coupling’ requires some form of charge control to prevent the batteries cooking, well that’s not strictly true if you use SMA products as the SI ‘off grid’ inverter can communicate with the GTI’s to ‘throttle them’. Whilst I do have all SMA kit I chose it for it’s reliability and not this particular function so have disabled it. Sounds a bit barmy I know but I’m going for ‘diversion load control’ via Tri Star TS 45 controllers instead. This will hopefully give me more control over my planned DC immersion heater elements, though it is still very much ‘work in progress’.
To this end I’ve set my three controllers to come on sequentially as the voltage rises.
Number 1 driving a 3kW load at 58.4v, number 2 a 3kW load at 59.2v and finally a 1kW load at 60v. This is very much experimental at the moment but it will give me a good indication of how much energy is available.
It’s a start anyway, all I have to do now is configure my ‘grid tied’ inverters into ‘off grid’ mode
but that’ll have to wait until tomorrow!