In my view, everything offgrid is based on solar energy. Sure, there are cases where offgrid is done with generator, but they are not really the subject of our discussion. But if we rely on solar energy, we have to capture it somehow and put it into batteries. Today I want to talk strictly about panels and in the next episode we'll tackle the topic of the solar controller, because even there it's an adventure. But we won't talk about brands. There are so many variants from Victron, LG, Canadian Solar, Nitecore, Poweracu, Solaewatt and they still appear and water. Basically the difference between cheap and expensive ones will be the lifespan and the actual yield. But for systems as small as a camper, my opinion is that the differences are irrelevant. For a farm with thousands of panels, there are not but in our case study, the impact generated by the difference in quality I think is minimal.
Panels are of many kinds, flexible, semi-flexible, rigid, monocrystalline, polycrystalline, amorphous or powerfilm and so on. And as many kinds as they are, so many powers they can have. And obviously, the question comes: which one is good for me? And to answer that we need to see what you want to do with it, what space you want to put it in and what it needs to power.
The first important difference between panels is the construction: rigid, flexible, semi-flexible. The rigid ones are the metal-framed version, which attach with flanges or screws to the camper, van roofrack or boot. The semi-flexible ones are attached with an existing or applicable double adhesive, directly on the bodywork or on the elements where they fit. And the flexible ones are somewhat intended for overlanding. They're small, they stink, they can have very reasonable powers and they come off when you camp. Personally, on the Gloria, we have a 300w rigid panel clamped with 6 serious flanges on the roofrack, so it doesn't go anywhere. Basically, this variant is super ok for most of our needs. Semi-flexible variants are perhaps the weakest on the list as they have the shortest life and heat up the most. In short, if we're not talking about a very good quality amorphous semi-flexible, I wouldn't even bother thinking about fitting one of these on any camper or overland car. We will come back and detail a little later all the reasons for this observation. The latter are the flexible panels that have gained a lot of ground lately, both because they are very easy to tighten, but also because they have a very good yield and can be repositioned according to the sun, unlike the previous variants that, in principle, are pretty much stationary.
Further we have monocrystalline, polycrystalline, amorphous or powerfilm. In short, in the long run, the monocrystalline variant is the most expensive per w but the smallest size for equivalent power. In general they are rigid and, like the poly variety, they do not particularly appreciate very high temperatures (above 25-30 degrees). The main difference between mono and poly has to do with the shape of the crystals. In the case of mono, as the name says, you will have a single crystal, while in the case of a poly panel, the panel will look somewhat like a broken window. These inconsistencies in the shape of the crystals cause the electrons to get trapped between the crystals and lead to a somewhat lower efficiency. The proof is that a polycrystalline panel will be about 25% larger than a monocrystalline panel of the same power. The biggest disadvantage of these types of panels is the decrease in heat output. A panel needs light, not heat, to work, and the 40-50 degree temperatures that panels reach in summer reduce their efficiency by up to 20%. And here I come back to the idea of rigid mounted versus semi-flexible bonded. The fact that the rigid one has room underneath for ventilation and cooling ensures both superior performance and a noticeably longer life. Amorphous panels are, at least today, the most efficient in terms of efficiency in all lighting situations but also in terms of working temperatures, having a completely different operating principle than traditional ones. But, this efficiency comes with some minuses, such as a much higher price and size for the same power. Traditionally, therefore, rigid or flexible monocrystalline panels are the best option when considering purchase price, yield and lifetime.
Let's not get too deep into technical issues. Let's relax now with some math, naturally.
Obviously, we start from the classic question: "How big should my caravan panel be?". Well, if we're going to keep it as simple and easy as possible, my answer will always be: put up the biggest billboard that fits. I've never heard anyone say "Look we put up two panels but we only needed one". Rather I heard "He didn't put the panel in enough, as a consequence there's no power, so it's warm beer". But leaving my unsolicited advice aside, let's see how we actually calculate a consumption. Well, let's start like in the first clip, from how much we consume daily. We have .... as I said there, about 1280Wh I think. We look at the number of hours of sunshine per day for each month we go out, roughly, and cut it by about half. So, if I were to go in June when I have say 6 hours of sunshine, we have 1280 divided by half the hours of sunshine, i.e. by 3. The result is a 426w panel that could replenish everything I consume in an offgrid day. There are multiple options where it doesn't come down to 50% but 70% or 75% but I like to be conservative and think of a system that will help me more than I estimate I need. And we can see these things. If we go on bluetooth and connect to the Smart Solar controller or VRM, we can see a very detailed history and calculate exactly what production we have. In my case, a 300W panel produces somewhere between 1 and 1.5Kwh on a sunny day. Of course, we've had days when it didn't produce even 300w and, in fact, that's what we have to take care of. Everyone can do it in the sun. So, I think I've solved that mystery too.
I was also going to talk about the related stuff like cables, presets, connectors and fuses but, to keep it short, let's leave those details for the episode on solar controllers. The important thing today was just to talk about panels. If we were to simplify and choose something concrete after all the discussion, my recommendation would be a rigid monocrystalline panel for caravans, motorhomes or vans and, as space is generally a sensitive subject for overlanding, without doubt a flexible monocrystalline, such as the 220w Dokio which seems to me an excellent choice for overlanding cars. I hope you enjoyed the article and ... in the next one, we read about the solar controller that helps us.