Before I get ‘all glum’ reflecting on today’s lack of progress I’ll ‘rewind’ back to Saturday, which was far more productive.
The first job being to take over 600lts of kerosene to the Schoolhouse to keep pace with our 100lt per week consumption!!! I don’t feel too bad about it though, some of the guests that rent the place can get through more than that in the summer!!
Showers of hail and snow on the forecast had me escorting the postie to work in Phoebe.
The road wasn’t bad and had been gritted but more snow was supposed to arriving over the weekend so she decided to leave the post van in the village and use Phoebe and her 4WD. I returned in the Almera and continued transporting the barrels over to Torran one at a time on what turned out to be a really sunny day.
The Tri Star MPPT45
Relying on gravity to empty the 208lt barrels is a slow process but it fitted in well with my other project for the day.
The ‘Old Schoolhouse’ has a very reliable ‘off grid’ system based on 1260w of solar and a hydro turbine capable of supplying around 750w at this time of year. We’ve had absolutely tons of power and the Studer SW2324 inverter has supplied it all seamlessly. However during the summer the burn reduces to a trickle and the hydro is down to just a few watts. More solar would obviously be the answer but all the available southerly facing roof on the ‘boot room’ is taken up by the 3 x 250w and 6 x 85w modules.
These nine panels currently charge the batteries via a PWM (pulsed width modulation) controller, which to be honest is my preferred option. PWM controllers like the Tri Star TS45 and Xantrex C40 are relatively cheap and very reliable, however there is a more efficient way. Maximum Power Point Tracking is the method used by grid tied inverters and it can produce an improvement of up to 20% in typical Scottish sunshine In other words it’s more efficient in marginal conditions.
I’m not really a fan of MPPT controllers for battery charging as they are very expensive and it’s normally more cost effective to just fit more panels. However, when my good friend Leslie Bryan out in rural Normandy http://www.echorenovate.com/ had one for sale at a very reasonable price and I knew it had been abused. Leslie is very ‘hands on’ with everything and is in the process of going ‘semi off grid’ on his large rural property that’s currently undergoing a transformation. An engineer and ‘horologist’ to trade Leslie can turn his hand to anything and plans to turn his place into a centre of ‘sustainable living’ running courses on green building and renewable energy. Indeed, amongst other things he’s produced an excellent booklet on how to make ‘cost effective solar trackers’ http://www.echorenovate.com/new-book—make-a-solar-tracker.php
So, whilst the barrels were slowly emptying I set about replacing the PWM controller with the MPPT one,
turning off the ‘Harris Hydro’ turbine first so I could flush out the pipe and reduce the input to the batteries. The hydro turbine doesn’t use the MPPT controller but I was wanting to deplete the batteries a little for my next job.
The MPPT controller is slightly larger but the ‘knockouts’ and bottom four screw holes are in the same place. The cables to the batteries and panels are not quite the same and I had lengthen one but all the ‘dip switches’ for the settings serve the same function, so I just had to alter those. Leslie’s ‘semi off grid’ setup, like mine uses 48v batteries.
With that in position and working I then set about improving the immersion element diversion system. The controller on the right diverts the first lot of excess power to a 1kW heater in the thermal store. This is set at half a volt below the MPPT controller so that once the immersion is ‘maxed out’ the battery voltage rises and then the second controller ‘throttles’ the panels. It was Hugh Piggott of http://scoraigwind.co.uk/ that suggested this method and supplied all the kit for this and my system. Along with the gear comes the best advice and this configuration above works really, really well.
With the power to the heater turned off I went into the ‘boiler room’ and rewired it with a dedicated isolator.
That concentric hybrid cable with an aluminium core and copper sheath is a bit of a nightmare to work with, but with a 25mm square copper equivalent impedance it’s great for low voltage DC applications like this.
with the hydro now ‘running clean’ I turned everything back on and as soon as the batteries were ‘topped up’
the first controller started diverting and the immersion started its characteristic PWM buzz.
It was an early finish for we were all off to ‘number 3’ for a birthday celebration,
a pure vegetarian feast of lasagne, lentils, cheese, olives and salad. All washed down with loads of red wine and home made ‘MkII Drambuie’.
Considering the overindulgence I was surprisingly chirpy this morning, though I have to say that I foresaw the hangover so left the quad at Arnish last night. The walk home at 9:30ish last night and the walk back at 7:30 this morning going a long way towards ‘restoring normality’.
Not a good day
Just like last Sunday, things did not go smoothly today and it was nothing to do with the lentils. The gale arrived bang on time and from the south, just as predicted, the turbine was pure ‘belting it out’ and I’d a big broad smile on my face.
A full 3.3kW and at one time it was over 4kW!!! However, that didn’t last, in a lull the voltage dropped below the ‘cut in’ threshold of 246v (the lowest this inverter will accept) and then along came the wind and took it over 600v before it had chance to connect again.
Once again I connected the hydro turbine DC to the Windy Boy inverter and brought out the laptop and once more I commenced a day of messing about with the settings.
It worked absolutely great in ‘MPPT mode’ but for some reason when in that mode it kept dropping out due to an ‘AC disturbance’ which I never got to the bottom of and there seems to be a 180second delay to reconnect, which I could not reduce. Tweaking about with the settings and using the hydro DC as a power source I managed to get it functioning again but I’m not really very happy.
This SMA software is pretty rubbish and the next thing that happened was that my laptop crashed so I spent pretty much all afternoon trying to sort that out. I figured that if I could load up the turbine a bit more it would be less prone to going over voltage.
However, I had even less luck with the ‘Windy Boy Setup Tool’ than I did with the ‘Sunny Data Control’ so gave up and tidied up the shed.
Sure, it might not be working very well but it does look neat I really must stop working on the Sabbath, every time I do something on Sunday it goes pear shaped, so I’m just going to have a large dram of ‘Balvenie Double Wood’ single malt and try and get some sleep.