Do you want a 12 Volt/24 Volt/48 Volt System?
I’ve just got power. And it’s sweeeet! What's more, this system functions better than my old system in Turkey, despite being privy to a lot less sunshine. This is because I’ve learned a thing or two about solar power in the meantime. A large tranche of this knowledge comes from my nearest neighbour Brian, who happens to be an engineer, and has one of the most efficient small solar systems I’ve seen. Yeah, I lucked out yet again, I know:)
My vecinos have three 250 watt solar panels. Their solar system runs a full-sized fridge freezer, washing machine, toaster, kettle, massive flat screen TV with surround sound, the well pump, lights, blender, hairdryer, vacuum cleaner, and powers another small guest cabin with small water heater… Yup, it’s pretty flipping amazing.
Needless to say, when I came to install my own solar system, I had a long, long chat with Brian first. What’s the secret to such a slick system? It’s a 24-volt set up, not your standard 12 volts.
Huh? What does that mean?
Now, if you’re an electrician, or some engineer type who knows all this stuff, you can zone out right now. Heck! Why are you even here? This, as with all my posts, is an overview for the majority of us bumbling mortals who can just about wire a plug, but get a bit lost after that.
The difference between 12V/24V and 48V Systems
Previously unbeknown to me, there are three types of independent solar power systems: 12V, 24V, and 48V. Most people automatically set up a 12V system because both the batteries and panels are (nearly always) 12V, so it seems like a no-brainer.
In truth, 12 volts often isn’t the best way to go. It’s not hard to wire a couple of panels or batteries up in series to create a 24V system instead, so don’t let that put you off. (Just get an electrician to do it for you, if you don’t know what wiring in series means).
Think of it this way:
A 12V system is like driving an old 2CV. Yes, it will get you from A to B, and if you only need to drive to the supermarket and back, it’s fine. But if you’re hitting the motorway, or planning a Pan-American road trip while towing a caravan, it’s going to get pretty uncomfortable.
A 24V system is like driving a Honda Civic. For most of us, this is plenty good enough. You can cruise comfortably and economically with your family on the motorway without worrying about a burn-out. You will be a little more prudent with your power usage than you would on-grid, but you should be able to run most appliances well on a 24-volt system.
A 48V system is like driving a Range Rover. This is for businesses or loaded individuals who want to splurge on power like it’s going out of fashion (which in a way, it is). I’m not going to waste time outlining 48-volt systems, because if you’ve got enough money for this you’re wealthy enough to pay a consultant:)
Here’s a rough outline of what a 12V and 24V system would look like, plus the types of appliances you can run well on each.
Bear in mind, it’s not just the voltage. You need enough battery power to run your system when the sun’s not shining, and you need enough wattage margin in the inverter, too (see my beginners’ guide to solar power if this doesn’t make sense).
NOTE: You can run a fridge or washing machine on 12 volts. It’s totally possible. But take it from me, you’ll soon be ragging your inverter and emptying your batteries. If you have 300 days of sun a year, you may manage. If you don’t, it gets much more annoying, and ultimately expensive, because you will have to replace your batteries, inverter, or both before too long.
Advantages of 24V systems:
1. The system is more efficient. You lose less power all around.
2. Reduced fire risk.
3. Better inverter efficiency converting to 240 volts. The inverter doesn’t have to work as hard to keep the AC output constant.
5. Larger usable voltage window for the batteries (in practice this means you have more power to play with).
If you are a numbers- and wires-lover just itching to geek out on this stuff, head to these sites to satiate your curiosity:
At present I’m only using small appliances, so I could feasibly get away with a 12V system, but... here’s the thing: I know I’m going to upgrade in the future, because I want a fridge and possibly a washing machine. So, what I did was buy a 24V inverter, and created a 24-volt system, even though I only have 230 AH of battery power, and two 60-watt solar panels.
Do I notice a difference with 24V?
Heck yes. A lot.
In Turkey I had a 12V system with a good 400 AH of batteries, in a country with 300 days of hardcore sunshine a year. So there was no lack of solar clout. But if we went three days without sun, I was out of power. I also burned my 600-watt inverter out after about three years (which is to do with an inadequate inverter as much as the system voltage).
Here in northern Spain we have 300 days of rain a year! I have only two 115 AH batteries. But I’m yet to run out of power. Even on a rainy day I get enough to charge my laptop. I’m observing that the batteries charge faster because there’s less power loss between the panels and the batteries. I notice the batteries lose power more slowly too. So to be honest, I’m a bit sold on 24 volts and would probably prefer a system like this even if I was only running the small stuff.
Many thanks to Brian for explaining this lot to me while simultaneously showing me how to make soda bread (I learned a lot that day). The car analogy is all his, though I admit I swapped the brands, because I like 2CVs better than Minis.
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16/3/2020 01:33:12 am
Hi Atulya. Thanks for this great share. Yesterday I asked an old Salty for his help on setting up a solar system for myself. His info was useful enough, but yours is freaking awesome and answers the questions that I didn't know how/what to ask.
17/3/2020 01:30:17 pm
Yay! So glad if this was helpful Magz. Yes, because I'm not a 'professional' builder, and definitely not an engineer, I don't use the confusing jargon. I didn't even know what a joist was when I built my earthbag house, but hey I still built the thing, and that roof functioned superbly:) Thank you so much for your support! So appreciated.
16/3/2020 08:56:56 am
Hi Atulya. Informative article, thanks. Another important consideration not that well known is the type of panels. Most people only look at the efficency of the panels without considering the fact that that is measured in full sun. Crystalline panels, for example, quickly loose ability to generate useful power when shaded/cloudy, (These panels were designed for use in space where completely different wavelenghts of light predominate) yet on paper they have high efficencies. Amorphous panels, on the other hand, have releatevly low efficencies on paper but will perform better than crystalline when shaded. Over all, in a wet climate, I would opt for prediminately amorphous panels. You do have panel technology like CIGS which do well in all light conditions but are more expensive.
17/3/2020 01:32:25 pm
Thanks Luke! Yes there are many many things to factor into a solar system, and it gets insanely confusing for non-techie people which is why I didn't try and cover every detail in one go:) I have to say, I find people usually overthink the panels and underthink the rest of the system, but I've got another post coming on that.
17/3/2020 02:17:39 am
17/3/2020 01:34:58 pm
Nice find Kit! You did well, because that system will last a long long time. People are slowly moving to 24V now, but in a few years 48 volts is going to be much more mainstream. And yes, so good to be off-grid as The System creaks on its hinges.
14/4/2020 07:16:45 pm
Hi, Atulya; I always look forward to your posts and have been learning from them. Being a bit of a car junkie, and especially fond of funky French cars, I have to comment about your mention of the Citroen 2CV. Truly, the original post war versions are not fun on motorways, (being so slow they'd be hit within the first minute), but from about the mid 60s towards the end of their long production life, they could maintain 70 miles an hour and had better brakes. Never quiet, they did the job. Here's a link to a story you may not have heard.
23/8/2020 10:39:51 pm
Ah just seen this John. He he, well it was only an analogy, so swap the 2CV with whichever car you like:))
28/10/2020 10:55:53 pm
I’m deeply entrenched in solar hell having just received a quote for a lot of money from a solar company. I’d be really curious to know first, what you spent on your system (if you don’t mind sharing) and, second, how you managed to piece it together and install it. Did your neighbour help? Did you buy the system all in one place from a solar company and have them do the install? Did you research and do it all yourself with bits you assembled? Thanks!!
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