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Message: <blockquote data-quote="scolairebocht" data-source="post: 141870" data-attributes="member: 8">By way of something different, I wonder if the denizens of this site have any interest in solar power and the way that maybe it can be used if we were ever to hit a grid down situation soon.New Financial Equation and other considerationsA few years ago you would wonder if the huge sums of money some people spent on large household solar systems, was really worth it. With not very efficient panels and over enthusiastic salesmen (not to mention a very misplaced hype about ‘renewables’ in general), you would wonder if a few of these installations could almost be classed on frauds in a country that traditionally had cheap and very stable electricity.But thats then and this is now, a heading in the Irish Times 29/10/2024 has pointed out simply that “Ireland has most expensive net electricity prices in the EU” and that would rate it then as close to the highest in the world. As regards stability some people, especially in the West and Midlands, got a big shock in the earlier part of this year when large tracts of the country were without electricity for weeks after a storm, and similar experiences coming from the USA and to a degree Europe, have caused a lot of people to ask what they should do to counteract these outages.The ‘equation’ that this section refers to of course, is the rising cost of Irish electricity from the grid on the one hand, and the much lower cost of some of the components needed for solar installations on the other, making an equation that could lead people to explore solar now? As a for instance on the Humsienk website (a Chinese battery maker) you can get a c.4,000Wh battery for €370 while on the boards.ie website as of  April last year they were talking about €2,000 for a 5,000Wh battery. But I do not believe that financial reasons are or should be the key element here though, its still the case that solar can require quite a lot of money up front and its still debatable if it will be recouped in time. Rather I think questions about the security of the current supply from the grid has to be uppermost in peoples minds, not least because of the open talk of a major world war in recent years. But remember it would only be practical in concert with other measures: its probably not a good idea to think about solar for any heating or cooking, because the large power that these demand would in turn necessitate very big and expensive solar systems. Rather open fires for heat (which is very flexible in what it can burn) and maybe gas for cooking (small gas hobs can be inexpensive and if linked up with the large canisters widely available in Ireland, you should have a reasonable cheap and practical backup cooking system) would be better options in those areas.In any case as well as getting cheaper, its also getting better technologically which might also make this a good time to explore the field.Technological Advances– Solar Charge ControllersThese are the devices that you plug the battery, possibly the ‘load’ (the appliance or household that is using the power), and the power coming from the solar panels, into, and it uses some software to put order on these competing demands and resources.Around the 1990s the new technology here was Pulse Width Modulation (PWM), a technique to vary the voltages around the system (by switching them on and off rapidly and controlling the width of the resulting ‘pulses’) so that, for example, the solar power coming in would not over charge the batteries, or the ‘load’ overly drain them. But then along comes Maximum Power Point Tracker (MPPT) solar controllers, which in a more sophisticated way cycle the voltage coming from the panels up or down to match the voltage at which the battery will accept the maximum power input, so saving as much as possible of the power coming from the panels. These units therefore contain coils that allow them to step up and down DC voltages in this manner.Judging by some real world tests, it seems you can expect an improvement using MPPT of maybe 20% on small systems and as much as 50% on bigger ones, depending on the variance of the voltages between, for example, the panels and the batteries, and possibly the overall atmospheric conditions, e.g. PWM controllers will match MPPT ones in tropical climates where the panel voltages will more closely match the batteries– PanelsOf course technological developments in solar panels is an enormous area, with the latest greatest thing announced every other week, but the switch from polycrystalline cells to monocrystalline ones has definitely helped in the last few years. For any system you will design now you will definitely desire the latter and they can be noticed by the black hue they give out as opposed to the blue one for the older type. Some claim that the efficiency of monocrystalline cells is about 18-22% (that percentage is a kind of notional value of the overall amount of power that could be harnessed from the sun) and for polycrystalline 15-17% and this might particularly matter in low light conditions.– BatteriesThis is another area where things have improved significantly in the last 10 years or so, driven by the necessity to power electric cars as cheaply and efficiently as possible. Obviously lithium ion batteries have taken over from lead acid (and numerous other types of course), because they pack a greater power punch into a smaller area, which is very important for cars. But some of this earlier lithium ion technology has serious drawbacks, including sometimes  a serious fall off in power as they are repeatedly cycled (cycling of batteries obviously means the number of times they are charged and drained) and actually spontaneous fires, these batteries are significantly more prone to that than say lead acid ones (and hence can only be used surrounded by strict battery management systems (BMS) that for example will track the temperature of the batteries and close them down if they detect problems). But now we have lithium iron phosphate (LiFePO4) batteries which are much less unstable that way and have far better power retention on repeated cycles (as much as five or ten times better than the previous lithium ion batteries). Also these batteries do not use nearly as much rare earth metals as the earlier type either, such as Cobalt and Nickel.So anyway I just think it might be worthwhile thinking about solar, and if so you might like to see two examples among three categories of these systems.Large house sized systems connected to the gridThere is a large amount of information on these systems out there, so there is little need to add  to it here. They might cost about €10-20,000 and you will recoup the money gradually as you sell it back to the grid and save on your own net usage of electricity. Sometimes they are a good idea I guess, but its a big outlay, much of it on expensive installation costs on high roofs, and you would need to make strong financial assumptions of the future to make it pay, and it may, or may not, work in a power outage. Meaning that if the system is installed without batteries then of course it cannot be used if the electricity is down, and even if they are so installed the default is that they cannot be used by the house owner when that happens, but there might be ways of changing that. Small systems using ‘Power Stations’Recently a new player has emerged in the last few years in the shape of the portable ‘power station’. In a way these are overgrown power banks (the type of things you might bring on holiday to keep your mobile phone charged), and sometimes made by the same companies, but many have facilities on them to easily incorporate solar power. They cost about from €220 to €2,500 but are very easy then to set up with a small solar system, and use the power so created.[ATTACH=full]7990[/ATTACH]To cut to the chase here is a very small example that can be used. It uses a Chinese Dokio 100w rigid suitcase style panel (c.€100) which plugs directly into a small Anker power station, which has a capacity of about 280wh and costs about €220. That is a fully functioning standalone system, there is no need for any other part. You simply place the panel outside in sunlight using the built in stand and then put the power station beside it (maybe covering it with the bag that came with the panel, to avoid it getting wet) then when you are finished bring the power station back inside and plug in whatever you want into it. Obviously it all depends on the level of sunlight you get, but you should be able to charge that system in one day even in Irish conditions, at least in summer.But, as pointed out above, remember to forget about cooking and heating (except maybe a 12v style electric blanket say?) on these kind of systems. The power draw of those devices is much too high, think mobile phones, laptops, lights, routers and internet systems and maybe TVs within reason. But obviously if you were to go up the ranks on these systems, and accompanying panels, then you will be able to power a lot more, although that will cost quite a bit. For example fridges and freezers are on the margin if you like, with respect to these devices. Meaning that with the big expensive systems, sure no problem, on the smaller ones it depends. Possibly it might be possible to get 12v car style fridges or freezers working on the smaller systems, which obviously then would be much less capacity than many modern fridges but still could be quite serviceable.</blockquote>

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