Why no 240v off grid?

Hickbeard

100 W
Joined
Nov 30, 2019
Messages
186
Hi guys.

I'm looking into off grid solutions for interest more than anything.

Out of curiosity. Why doesn't anyone run a 240v system? So no need for inverter (at least here in UK).

Is it to do with the voltage solar panels charge at?

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Step-down inverters seem to have minimal mosses, and higher voltages use thinner wire, so that would save a few dollars for the full system. I've only seen one system with higher voltages. It had the solar panels wired for 144V, to charge a battery pack, and the inverter stepped that voltage down to 120V AC. I don't recall which charge controller he used.

The cheapest and most available components are mass-produced, so 12V, 24V, and 48V seem to be the most popular battery packs. Once you spec the charger and inverter, seems like it wouldn't be too much more complex to build?...
 
Is it possible to do?

Super expensive?

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Solar panel voltages have no relation to the system / battery bank voltage, just need to select the right controller designed to handle your combinaton.

Voltages over say 60V are very hazardous for amateur DIYers

Even at 48V you're getting into EV / propulsion use cases, not "House bank" / solar storage

And you need AC for mains appliances, inverters are required powering off that storage no matter the voltage. DC is much more dangerous than AC at the same voltage also.

Off grid living is all about conserving power, low power levels so your "mostly solar" ideally is "only solar" most of the year.

People lugging around mains powered mod cons gear designed for S&B homes often end up running the genset many hours per week, at great cost per hour polluting our ecosystems and annoying the heck out of anyone nearby.

The best possible investment is paying more up front for very energy efficient gear.

Use LPG for anything requiring heat production.

And just don't expect the same level of comfort and convenience when off grid, compared to hooked into mains.


 
Argh of course. Mains is AC, solar is DC.

Makes total sense

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Yes, an “inverter” is by definition a DC/AC converter,
The only way to avoid using an inverter is if you use a AC generator ( Wind or water turbine ?) ..with controls to regulate the output voltage,..then you will have to be creative for any non DC storage ,...(pumped hydro ?)
It can be done, but Solar, inverter, and battery storage is much simpler, and less maintenance.
 
I think what you're asking is about the lack of resources, that would be because solar is still limited. My mother tried to run her agricultural facility off grid. It winds up with propane generators in key locations where the batteries can't store enough electricity, etc. Her house had some DC appliances, some AC, gas furnace, stove and oven. Large and small solar trailers for places she didn't even have panels set up. After more than a decade of problems, she threw in the towel and had the grid installed. Lucky for her the distance had been shortened by several miles by then. But even in the beginning it would have cost less to bring the power to her that way than what she spent. Though the trailers are of course still in use. They have been the most practical because they see less demand. The moment I hear someone wants 240v I assume they want a 40amp breaker, that's now 4 times the wattage per outlet, not twice. Don't think about unlimited power off grid. Think very low power usage.

You can run at 240vac from the panel and step down. It's available, not sure it's so practical for most people. I would say the more you need to DEPEND ON your 240v, the less you want it to be solar. The more you want to depend on the solar, the less you want to demand from it. On grid you'll have your power either way, so it doesn't matter your own power will be unstable. But I want a bigger than local power outlet in my garage to run something you don't normally find in a residential garage, but I could run a 10kw motor several times a week from a battery solar charged. . . .

https://www.ecodirect.com/BenQAUO-Solar-PM250MA0-250W-225W-240VAC-PV-Panel-p/benq-auo-pm250ma0-250w.htm
 
Micro-Inverters are are the latest way to go with a grid tied system.
Off grid probably a 48 v battery system to a inverter for the ac items you can't do without.
Although with 240 v ac coming from your panels you could power a battery charger
directly. 🤔
 
So off grid is as you guys say all about cleaning up your usage over I guess not being beholden to energy companies.

So off grid application has its limits and you need to decide if your requirements fit this limit. As opposed to making off grid fit what you want.

I find the whole idea fascinating but am probably not suited to the actual day to day living of it. In love with an idea lol.

I think a lot of that is YouTube. I keep watching these videos of off grid and I guess you only see the nice bits.



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Mains electricity being so stupidly cheap has conditioned first worlders especially USians to be stupidly wasteful.

Learning to be mindful of every Ah per day you are consuming

just like every liter of fossil fuel and fresh potable water

is good for the sould and necessary for our survival as a species.
 
Hickbeard said:
As opposed to making off grid fit what you want.

You can make off grid fit what you want by buying more and more and more. My mother sure did. The properly licensed electrician of the family didn't build it, a "Service" did. The brother was far away at first, then moved farther. Another nonelectrician brother got interested in the subject and rebuilt the original shed, then did all the subsequent building except the large solar trailer. But he, too, was not right there all the time. She needed better cells than the standard 24v lead acid she was using, I was interested in the molten salt but I'm in another state. Whether or not Ma's system would have been good enough for someone who knew how to deal with glitches we'll never know, but it had to be close. But she had the propane generator and that ran some. She was never going to recover her cost in being off grid.
 
Yep Im running the EVTV 240v 6kW inverter hooked to some Tesla Model S modules, charged daily by a few kilowatts of solar.
 
Warren said:
Watch Jack Rickard's EVTV. He sells 400 volt DC/240 volt AC off grid systems.

That is just so that a 400V DC ( Tesla) EV battery pack can be used ...which he sells...for storage.
..and doesnt answer the OPs question about avoiding the use of an inverter..

Hickbeard said:
...... Why doesn't anyone run a 240v system? So no need for inverter (at least here in UK).....
 
12V is the way to go for House storage in a mobile context.

Going to 24V only if the truck's alternator puts that out, or if you have high-amp loads that really require it

you'd need buck conversion down to 12V circuits anyway, lots of load device categories mot available or just stupid pricey in 24V.

ex-EV packs are stupid dangerous in this context

LFP, LTO are the only safe LI chemistries for DIYers, but really with a big vehicle lead is most cost effective.

Inverters are 100% optional, IMO makes more sense to just buy cheap little ones spec'd and sized for the device that needs it.

For mostly solar off-grid living, energy efficiency is best served by avoiding them as much as possible.
 
john61ct said:
12V is the way to go for House storage in a mobile context.

Going to 24V only if the truck's alternator puts that out, or if you have high-amp loads that really require it

you'd need buck conversion down to 12V circuits anyway, lots of load device categories mot available or just stupid pricey in 24V.

Inverters are 100% optional,
^^^^. I dont think the OP mentioned a “mobile” set up ??
He was talking about Solar inverters on a 240V AC,.standard domestic system ...in the UK.
 
My system is 48 volt DC based, going to an invertor that steps it up to 120/240VAC. Makes it real easy to run standard appliances.
 
In the US, most electrical code requires battery packs to be no more than 48volts DC.... left over from the days trying to protect DIYers that if voltage was <48 vDC its less likely you will kill yourself. Over 48v DC is hard to let go of, and can stop your heart. less than 48v will probably just burn you. This code was written in the time of flooded lead acid batteries when users had to periodically expose themselves to wires (and acid) while watering batteries.

kind of a moot point now with sealed AGM, and Lithium batteries... especially as we have more EV battery packs available at 300+ vDC.

Output AC voltage can be 120vAC, or 240vAC with commonly available inverters.... lower current and presumable installed with proper circuit breakers to protect you. PV string interverters used to take string voltages up to 500 volts, but modern micro-inverters usually kick out 220v AC and sync together with grid-tied installs. not typically used for off-grid since there is nothing providing the master heartbeat to sync to.
 
No one's going to question whatever voltage you want to use.

For example if you have ebikes that are setup to use 72V or whatever, it would be sensible to use the same, build duplicate packs so you can swap them out, recharge off grid or at home or from public charge stations without messing with multiple sets of infrastructure.

But yes once you get past 60V or so, much more lethal if you screw it up, so learn how to do it right, or hire a pro to do it for you.

You need to take responsibility for your own safety, even if the jurisdiction you're in has no regulation, or ineffective enforcement.
 
I figure If you were designing a 100% off-grid electrical system from scratch it would make most sense to skip the inverter and just use household DC.

Back in the day AC was desirable because you could cheaply step up and step down voltages with a transformer. Nowadays solid state DC buck and boost converters are cheap. Plus power transmission isn't a big deal when it comes to off-grid systems.

It is my limited understanding that low-frequency AC is significantly more dangerous then DC for equivalent voltage. This is because DC causes a single muscle contraction were AC can cause freezing or repeated contractions. This means a DC victim will tend to pull away from the voltage source were AC victim will grip hard and repeatedly. Also your body has a capacity capacity and because of that the AC voltage will tend to be 'stepped up'. Also AC frequency is much more likely to send the heart into ventricular fibrillation. DC is more likely to freeze it. It's easier to start a heart that is stopped then one that is fluttering.

Or something like that. Hell if I know. I used to believe that DC is worse because it causes you to grip onto stuff, like whatever is shocking you, but I don't know about that anymore.

Any sort of appliance that uses a universal motor will run just fine off of DC. Old fashioned blenders, drills, and a multitude of other tools, Water heaters and old fashioned stoves can probably run just fine off of DC, provided there is no microcontrollers in them. Maybe it would require some mods, but it shouldn't be anything super crazy.

Although it would probably be better just to have natural gas or propane versions of those.

For air conditioners and fridges/freezers you can get them in DC versions.

Then that leaves devices that have microcontrollers that you can't get alternatives for. Microwaves, I suppose. And computers. That sort of thing. Having a few smaller inverters used locally with a appliance is probably a lot cheaper then trying to find one gigantic one that will run a entire household.
 
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