We have had solar panels for about nearly 20 years. The first ones we bought were small and quite expensive, to see if solar panels really worked at all. The second set was a pair of Unisolar 12v 64w panels, physically quite large, alleged to work well in cloudy conditions. The third was a BP 80w panel, much smaller, and, it seems, not brilliant in anything other than bright sunshine. About 4 years ago we realised that we needed more power from an alternative source than the wind in summer, as wind speeds drop off, and bought two Schuco 200w panels. These were brilliant, and made a huge difference to our summer power supplies. For at least 6 months, probably 8, we could get far more power from the sun than the wind. And all this time, the price of solar panels was dropping, thanks to increasing incentives driving the market (though we do not qualify for such incentives, more's the pity).
So when Hugh Piggott (see previous post) suggested we increase our solar capacity, it made sense to me, not from the point of view of the peak summer power output, but to elongate the period during the year in which we could get power from the sun. If we could push this from 6 to, say, 9, or even 10 months of the year, it would leave just the windy winter months for the new wind turbine to supply our needs.
We live just 400 miles from the Arctic Circle, at 58° north. That means, in winter, not only is the sun at a low angle, and only up for 6 hours or even fewer each day, but the light also has a lot more of the earth's atmosphere to get through, because of the angle at which it strikes the planet, all of which reduces the solar radiation. In fact a sunny winter's day will see at best a tenth of the solar power in comparison with a summer's day, according to our ammeter, a hard demonstration of the theoretical difference. So we are under no illlusions about solar power in the depths of winter, But the seasonal light levels change quickly. There was a reason that the Medieval church regarded the 2nd of February as the Festival of Light, when candles for the church for the year would be blessed, hence the name Candlemas. (And indeed, I recently read some scientific justification for this - see a BBC magazine article here.) After the beginning of February the light levels increase quickly. Another way of telling this is by the time when the hens take themselves off to the henhouse to roost; in the same as in late autumn this gets earlier and earlier, so in early spring it gets later and later. The flip side of the duration of winter days is that summer days are very long, and at the height of summer it hardly gets dark. But it is not realistic in our environment to use special solar panel mounts that track the sun across the sky, so we only get power when the panels face the sun, not really a hardship.
So we bought 4 REC 250w panels, which, with our existing Schucos, would give a maximum of 1.4kW of power. We bought these through Hugh Piggott, who was apologetic about the extortionate shipping charges applied to these things to our area - the shipping alone costs the same as one panel. We also bought an additional Morningstar Tristar 60A charge controller, heavy duty armoured cable, control boxes, and all the various bits and pieces that are necessary to put everything together. In fact, Hugh put all the bits and pieces together without us asking, a most welcome service. A trip across to the east coast, to a builder's merchants in Tain supplied wood for a framework and concrete mix for posts to hold the framework. For the short posts cemented into the ground, I used an old unused aluminium scaffold pole that we originally bought for the wind turbine, but when we saw how much it flexed in the wind, quicky substituted a steel one instead. I dreamt about alternative plans for how to build and install a framework and after much thinking, decided on two frames, each holding two panels. I had a smaller frame for the two older panels as a guide, but I knew I would have to make these stronger to withstand winter storms. The plan came together in my head, and I started sawing, drilling, screwing and hoping. The frame was built as a base frame, to which metre-lengths of aluminium poles were attached. I had worked out how big this was to be based on the angle I wanted the panels, desparately dusting off trignometric knowledge largely forgotten since school. I could remember "Saddle Our Horses, Canter Away Happily, To Our Adventures" as the mnemonic for sine equals opposite over hypotenuse etc, and the sums gave answers that seem to have worked in practice. A second framework, to which the panels would be attached, suotably angled, was also built.
I spent some time thinking about an appropriate angle for the panels. Often one sees panels which have quite a slight angle to the ground, but I think those are for feeding the grid, when you are trying to maximise summer conditions. For us, we need to maximise winter and "shoulder" seasons, so a much greater angle is necessary, without going all the way to the vertical, if only to minimise the exposed face of the panels to storms. I also decided to set up two sets of framework, so that if a storm damaged one, the other has a chance of survival. I was amazed that the two sets of framework are remarkably straight, the panels at the back in the picture below are the original Schucos. This was a desired but not often achieved outcome of my bodging the systems together.
Then I dug the holes to ensure a secure and stable platform, meaning deciding what direction to face the panels. The helpful assistant at the builders' merchants, when I owned up to being an amateur, recommended suitable ready-made concrete to ensure the posts are well embedded. The holes had to be dug at specific locations as ideally the panels should face south, but in winter. the hills to the south east shelter the sun, so facing them slightly west of south would be better.
You can get all kinds of special fasteners for the panels, but I used fencing wire to secure it, a tried solution which gives confidence. I knew the thick armoured cable would be a challenge to fit in itself, but I wanted to test the panels, so some spare heavy duty but unarmoured cable was brought into service, and I wired up the charge controller. The first day was sunny, and I could hardly believe the ammeter just after lunch - well over 40 A was coming in. We used the toaster for lunch, and at one point, the ammeter touched 50A. Fantastic. By 11:30 on a sunny day, the batteries are up to voltage so in late autumn we will see how well the panels cope. As luck has it, we have had wonderfully sunny early spring days since installing the panels, so it will be interested to see what the panels produce on cloudier days. (Edit - around 10A on a rainy, cloudy day in late April. Very acceptable.)
Since the photographs were taken, I have added some additional diagonal stays to the framework, as we have to consider stormy days of gales and, last winter, even hurricane force winds, and on lovely days like those on which the photos were taken, it is very hard to imagine the forces those winds generate, and take steps to avoid damage.
The next stage is to get the wiring correctly installed. This is not going to be easy for an amateur, as the thick armoured cable is very difficult to manage.