(I hope to come back to this blog entry and edit it, as well as adding some more pictures. It was written the day after the new turbine was installed, which should ensure some detail.)
I have blogged about our off-grid power on a few occasions, and if you are interested, just select the "Off-grid power" on the right hand side of the page to take a look. In general, our systems work well, with one exception, during the winter when we experience highest winds. That may sound odd, as wind should provide plenty of energy, but the wind turbine we have been using is not really designed to be used in areas of high wind speeds, and indeed, searching carefully through the manufacturer's web site and installation instructions reveals a note that the wind turbine should be shut down in winds higher than force 6 or so. They advise tying the turbine too, to ensure it suffers no damage. This is an alarming issue, as it it means that the turbine needs much more close attention than is ideal, and a mistake in shutting down the turbine in time can lead to a costly outcome, in additional to the hassle factor of having no turbine. But that's not the worst of the issue,
In winter, we may have weeks of winds above, say, 20 mph. That's about the highest wind speed you want to climb a 6m tower to tie up a turbine, and believe me, you cling on to that tower for dear life in those conditions. This means that we have had to keep an eye on weather forecasts obsessively for at least a week in advance, to ensure that we can safely tie up the turbine in time for a blow that may be a week or more away, meaning no turbine power while waiting for the blow. This becomes very frustrating as well as costly in petrol for the little generator that must be used to keep us supplied with power. Risking not tying up the turbine means sleepless nights as the noise of the wind over the roof makes it sound as though nothing can survive outside.
This winter was the last straw. We even had hurricane-force winds on one occasion. During those conditions, survival becomes your main concern, and not the condition of the turbine, and I was amazed that the tie-ropes remained intact, and that the tower itself withstood the forces. Many homes were damaged during this severe winter storm.
So I contacted Scottish and Southern Power Distribution, who it seems have the monopoly in installing power connections here, in an alleged free market in power in the UK. Their indicative quote was for around £16000.00 just for the connection. We'd be responsible for trenches and who knows what else. I could not see us getting change from £20000.00, and this was just an indicative quote. I could see the costs mounting if we went ahead. At those prices, it seemed to me that the installation of more suitable equipment for continued off-grid living would be possible. We now know that we get the most reliable power from the 400-500w of solar panels we have, for about 8 months of the year. The remaining 4 months, the winter months, the turbine needs to take up the slack, but needs to work under high winds. What if we could find a robust turbine, and add a bit more solar power, to elongate those 8 months to, say, 9 months?
A lengthy period of research into options suggested that the Ampair 600, a design which incorporates a geared over-speed protection system inside the turbine hub, would be the type of thing we needed. I found some articles about the use of these in the high arctic, used at remote stations, so without human intervention. I also found some web sites offering the Ampair 600 for sale at well under £2000.00, not an inconsiderable cost, but if it did the job, a cost worth paying. BUT... when I contacted the companies offering the Ampair, none had them in stock, and all apologised for incorrect pricing. The cost had more than doubled, and £4000.00 seems steep for such a device.
So I contacted Hugh Piggott of Scoraig Wind Electric . Now Hugh is an absolute guru when it comes to wind energy, and is well known through his books, magazine articles and courses on building your own wind generator. What he does not know about off-grid power isn't worth knowing, and I must admit it was with a sense of the star-struck that I sent an initial email to Hugh, asking his views about the Ampair 600, and, to be honest, crying on his shoulder in frustration at the old turbine, the power company and life in general. Hugh replied quickly, assuring me of the sense of remaining off-grid, and offering some suggestions from his experience to guide my thinking.
For some weeks, we exchanged email and he helped me firm up my plans as to how to proceed. It would be good, Hugh suggested, to increase the solar capacity, which validated my thinking, and a turbine suitable for our conditions should not need as much intervention as the existing one. Hugh kindly offered me one of his own turbine designs, which had been built during a build-your-own turbine classes he offers at Scoraig. This would be a lower cost option to a commercial turbine, and incorporate Hugh's experience of life in the off-grid community of Scoraig, 60-odd miles south of us. A commercial variant of Hugh's turbine, the African Wind Power system, was installed locally by Hugh around 10 years or so ago at the home of someone we know, and we know that that turbine has survived some incredible conditions, including this last winter's hurricane. But I thought that I lack the engineering knowledge to get the best from one of Hugh's machines, although I would have loved such a device. Hugh thought I was being hard on myself, but was gracious in acknowledging my preference for an off-the-shelf system. It is a demonstration of his generosity, though. In the next blog post, which will deal with the updates to the solar system, I'll say more about Hugh and his generosity of spirit in helping others through his experience.
By this time, I had found an alternative to the Ampair system. The Ampair had two design factors that, in the limited experience I have gained with relying on wind turbines, made it stand out. One was the mechanism for altering the angle of the blades to manage high winds, and the other is that it produces high voltage AC current, which then requires a rectifier at the battery bank. This last is useful, as it means you can run thinner, more manageable cable from the turbine to the rectifier. We had experience of cables getting too hot from high amperage at the turbine, but high voltage would prevent that from happening. The German designed and made Superwind 350 got one out of two of these, the in-hub geared furling mechanism. It only produces 350w, so the current should never get high enough to create a problem. Hugh said he had no direct experience of the Superwind, but had heard good reports. So I ordered a Superwind from their UK agents, Mactra, after speaking to Mactra's owner, the exiled Scot Jim MacDonald, as well as the ever-helpful Liz.
Superwind seemed to understand our problem. From their site:- "In the past small wind generators were used rarely for professional applications, since they generally did not have effective safety systems and since they were not reliable enough for automatic and unattended operation." The web site goes on to talk about the Superwind as a "small wind generator for professional use, which even under extreme conditions works autonomously and automatically." This sounded like the right thing. Under specifications, the following is of special importance:-
|cut off wind speed||none|
So it looked as though the Superwind will look after itself while its owner is sitting quaking with fear during storms.
Time will tell.
The Superwind duly arrived, and unlike some of the previous turbines I have used, does not fit over the outside of the mast, but inside the pole. It comes with an adaptor allowing it to be used on larger, 60mm pipe or smaller 49mm pipe. A drawback is that it is necessary to drill and tap two holes at a fairly critical location, but from an engineering point of view in the marine environment for which the Superwind is designed, it seems to me that this is a good idea.
Then the long wait started for a suitable weather window to drop the tower to check it, alter the way the wiring insude the pole was routed and install the new turbine. This only happened in early April.
The first job was to remove the Futurenergy from the tower. I've done this on several occasions, so it was fairly straight forward. The Futurenergy had some superficial rust on the main support, and an internal barrier that keeps weather away from the electronics was badly rusted, but it was otherwise in good condition. The cabling, which was always a worry to me, as under peak conditions it needs to be able to cope with nearly 50 amps, was in a fairly good state. In a previous installation, I had inadvertently pushed the wires on top of each other, where it was able to heat up and melt the insulation, (fortunately not shorting...) so I knew the importance of getting the cables taut but not under load. Down came the tower, and I started work on a better hinge system for the base. I did this by adding a short length of pole to the base, which was easier to work with, and which was joined to the main pole with a fitting used for scaffolding. This good hinge makes lifting the tower easier and safer. I also wanted to avoid having to rig cable inside the pole before putting it up, so came up with a solution to allow that to happen.
I should also say a good word about making sure you have a handy-billy to help raising and lowering masts. I have a couple of blocks I bought at a chandlery some years back, and they offer a 4-to-1 ratio, which, although it uses a lot of rope, makes fine control and ease of lifting a lot more manageable. If anything, one has to be careful of over-doing it and pulling the mast right over. With a pair of side-ropes, I had enough stability to start connecting the various stays, which are just fencing wire and fence tighteners, and are positioned at three sets of points along the mast.
But when it came to fitting the Superwind, imagine my consternation when I found that it would not fit the inside of my standard scaffold tube.
Now, we are 100 miles from the nearest metal merchants, and getting a pole here is a costly and long winded process. So, while we had to make a journey to the east later in the week, I wondered what I could do. I did not want to take any chances with the fitting, as the top of the tower will experience a strong bending moment during gusts, but I also knew that fitting the unit, while at the top of the tower, is not an easy task. For that reason, the type of fitting where the turbine fits over the pole is easier as you can lift it and slip it over easier than trying to manouever it into a precise position while holding it above your head, if you can imagine what its like trying to do this on the top of a ladder. I had a piece of 60mm pipe, which slots over a 50mm pipe beautifully, so I cut a length of 70cm, below which the first of the guys for the tower would sit. So I drilled and tapped four locations for holding bolts, and ensured that the turbine fitted correctly into this, shorter, pipe. I could therefore fit the turbine to the mast stub while still on the ground, which makes doing a good job of it easier.
Another little detail that is worth noting with the Superwind is that inside the shaft is a little retaining bar, around which you can slip a piece of rope. This can be lashed to the electrical cable, which can be quite heavy when it is 6m of cable running vertically, to take the strain from the cable itself. But in our case, it can also be used to draw the turbine onto the mast by pulling at the rope from below, providing an extra safety factor.
I had drilled a large diameter hole at the base of the mast, and connected a 14m length of cable to the turbine. 14m? Yes, so that I could feed it into the tower from the top, while the turbine was still on the ground. I ran a length of wire up the hole to the top, attached the cable from the turbine, and pulled the cable down. Initially it was a struggle to get the cable through the hole, but I did not want the hole to be any bigger than it needed to be. After a while, all was done, and we repeated the process with the retaining rope. I should have photographed all of this, but I was more intent on the job itself, especially as we knew the few days of high pressure, which resulted in perfectly calm conditions to do all this work, was coming to an end. Here is Helen's picture of the cabling being done, showing the maze of stays which look over the top right up to the time a storm blows through, when they seem puny and inadequate.
My top fitting worked a treat, and within minutes the unit was on the tower. I connected the wires at the base to the over-sized cable between the tower and the battery shed, where the existing safety stop switch and other cabling could be re-used. This was the time for checking and re-checking the electrical connections, making sure they were correct, as you do not want to get polarity wrong or make any other wiring mistake when you connect up a large battery bank. At the top of the tower, I turned the generator manually while Helen checked the polarity of the cables in the battery shed, using little PMR446 radios to talk to each other. For some reason, I had a crisis of confidence at this point, perhaps because everything was pretty much going to plan at this stage, so I re-checked and re-checked before going on. I then fitted the blade and hub unit, and in the light winds, the turbine started spinning. I knew the wind was far too light for a charge, but a minute flicker of the ammeter showed we had the job done, and that no mistake had been made.
What about performance? Well, as I discussed, the problem we are trying to solve really is the winter storm problem. However, there is no doubt that replacing a machine capable of generating 1kW of power with a 350W unit is going to mean less power into the battery bank during non-stormy conditions. I never used an ammeter on the Futurenergy, but I do not think it often provided full output, which theoretically it developes at around 25mph. The reason for this is the furling tail which started to turn the turbine away from the wind at around 20mph, according to our anemometer, resulting in a much slower spinning turbine, and of course, less power. Real life wind is fluky and gusty, and you don't get the perfect power curves that perhaps you do in a wind tunnel. I had also made some adjustments to the Futurenergy to make the tail furl to a greater angle in an effort to handle higher winds without causing damage, something which I think has worked. The upshot is that the we probably got around 600w at most from it, as it was tied up in higher winds that would provide more power. But at lower wind speeds, a careful watch on the voltmeter showed that it was able to maintain battery voltage at just over 8mph average winds, where I expect it would produce about 3-4 A. The Superwind needs 12 mph winds to produce this amount of power. So the sweet spot for the Futurenergy was 8-25mph, while the sweet spot for the Superwind we expect to any wind speed above 12mph.
The next blog entry will be about phase 2 - increasing the solar electrical capacity. By the time that is done we will have moved from therorectial 1kW wind plus 500W solar to 1.5kW solar and 350W of wind.
A note about the Futurenergy we are replacing. This British designed and manufactured unit really is great. The alternator is clearly very good, with the rated output at relatively low revs, and the blade assembly is good and robust. The 1kW output is exactly what is needed for people off grid like us and the pricing is simply superb. But we live right at the coast, and we are closer to the Arctic Circle than we are to London, and the Futurenergy is not, we think, meant to be used in such challenging conditions. We have had very good service from Futurenergy who even arranged for a spare unit for us, without the blade assembly, when we sent ours in for repair, at a discounted cost. Given our experiences, an unbeatable unit will be a Futurenergy alternator, built with a marinised finish, but equipped with an in-hub over-speed protection like the Ampair and the Superwind rather than a furling tail. Even if that doubles the price, it would be a wonderful unit.
Addendum: Since writing this a few months back, we have had a few near-gales come through, with wind speeds of over 30mph, gusting to over 40. During this, the ammeter never went above 14A, even in gusts, showing tha tthe furling hub works quickly and well. These manageable blows have been encouraging, though it still needs to be tested in winter conditions.