Hi,
I need to be off-grid for 24 hours, I will be powering a device that consume 2kw.
I live in Africa, so Sun is not a problem here. Thanks, jongi
How to select best UPS and Solar to be off-grid 24 hour for 2kw
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Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#2How often do you need to do this? (E.g. once, once a year, once a month, or once a week?)
And do you have access to / storage for liquid or gas fuels?
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#3I would look at off road, camping, and overland forums for ideas.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#4That's 48kWh. You're going to be looking at a setup that's a few thousand dollars.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#52kw draw for 24h is actually quite substantial. Don't forget regardless of how sunny it is in Africa, You will still need to have enough stored power to make it through the night.
I'm not saying it is impossible but suspect it will cost more in fuel to transport the batteries and panels than it would to just run a small inverter genset instead.
If your device doesn't need to be constantly powered then I would suggest bringing pre charged batteries and not bothering with the panels.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#6The answer depends on exactly what you want.
Here is a guy doing a solar shed/office with a similar power envelope as you are: https://www.sevarg.net/2016/05/15/solar-shed-part-1-overview...
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#7As some other comments noted, there is a lot of information missing to give you a good answer.
Do you need to be off grid 24 hrs out of every 24 hrs? (No grid connection, permanent off grid)
Do you need to be off grid UP TO 24 hours, with a grid connection most of the time?
Is your grid power cheap? If so, how cheap? It might be worth it only as a weather related backup if it is cheap, or might be worth going full off grid if not.
Do you plan on sustaining that 2kw the full 24 hr, or only peaking up to 2kw? If only peaking, for how long?
There are lots of potential trade offs that could help a lot in making it cheaper, or make it much more expensive if you can’t do them.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#8How much advance warning will you get? You need 48 kWh + charge/discharge losses. So if you get 8 hours of sunshine on 100 W per square metre panels you need 48/(8 * 0.1) square metres to charge in one day, that is 60 square metre. Or you can use two months to charge and one square metre of solar panels. More panels charge in less time. Then you need a battery about the size of that in a medium sized electric car if you use lithium ion or lithium iron phosphate. If you use lead acid batteries which are probably easier to obtain in Africa, and cheaper, you will need something like 50 car batteries or equivalent because each on has a capacity of about 1 kWh depending on the size of the battery. Don't actually use car batteries, there are batteries specifically designed for use with UPSes
How portable does this installation need to be? If it needs to be at all mobile it really would be simpler and a lot cheaper to use a 2 kW petrol or diesel generator
So to summarize you need to decide how long you can wait for the battery to charge, how often you want to go offline, how big a solar array and battery you can afford.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#9Firstly - maybe someone knowledgeable will come along, but but I wouldn't hold my breath - most people here have never touched an off-grid setup. Some might have some form of feed-in tarriff with solar on the roof, but that's totally not the same.
Secondly - there is not enough information here to provide real advice - do you mean that you are normally connected to the grid, but need to survive an interruption of 24 hours? In that case the generator suggestion might make sence. Or do you mean that it is a total off-grid location that needs to be self-sufficient, in which case the generator idea is idiotic.
Just saying 'Africa' is not enough, look for solar irradiance map and and figure out your annual solar incidence. That will inform how you size your solar panels - their power rating are given under standard incidence of 1000W / m2, so you can basically multiply annual irradiance to figure out how much power they will collect in a year.
For example a single 300W panel in the middle of Sudan will give you 720 kwh per year, or ~ 2KW/h per day. Same panel in Gabon will givey ou half as much. Then you have to account for seasons, in UK we get almost 8 times less sun in winter than in summer - you can't compensate for seasons with batteries, so you need more panels.
Batteries compensate for periods of bad weather and nights - they need to be sized according to weather and importance of the load: what happens if there is some unusual bad weather and power runs out, how important is the load? Are we going to be stuck without a TV, or is someone's life on the line? There is also a balancing act - you can compensate for bad weather by getting more panels or more batteries. Example of a battery bank: https://www.photonicuniverse.com/en/catalog/full/359-24kWh-4...
Then there are furhter spesifics -> is space at a premium? Is the load DC or AC? With DC you don;t need an inverter and you avoid losses.
Here is a UK centric calculator, just to sanity check some numbers: https://energysavingtrust.org.uk/tool/solar-energy-calculato...
Generally you will have local firms that specialise in installing solar and they will do a better job of providing advice than NK.
Re: How to select best UPS and Solar to be off-grid 24 hour for 2kw
#10AFAIK most prepackeged UPS devices are a battery and inverter. My hot take is that if you need to run this device continuously it will be a substantial (& custom?) build. The biggest factor is how portable it needs to be.
Overview: Most solar outputs 12 or 24v, so what often happens is solar -> controller -> battery (or bus) -> inverter -> your device.
Batteries: Many batteries are rated for 100ah at 12 volts (so 1.2 kw hours). You would need 2+ of them to run the system purely off them for about an hour. You can buy much beefier batteries designed for residential homes (e.g. 3' x 2' x 1' in size, 10kwh, $5,000+ for lithium, etc..).
Solar: The panels you might see on top of a camper often generate 100 watts each, so you would need 20+ of them to continuously sustain your device. Can be 250 watts or a bit more, so 8+ panels.
I've only worked on electrical for a camper, so could be missing other options! AFAIK your requirements aren't crazy for residential solar setups.