The energy solution for South Africa is DC power.

[Swa]

Dude it steps the voltage from 12V to a higher one to charge laptops.
Output: DC 15/16/18/19/20V 4A DC 22/24V 3.3A 80W Max
So you're back to wasting power with DC-DC boost converters.

Current step down transformers used in all your DC appliances wastes even more power. You're also completely missing the point of converting to DC.

Then what's the point?
I don't see the logic about having to have two separate standards for appliances. At least at the moment everything runs off 220-240V 50Hz AC.

The point is to be self sufficient and not rely on an external utility to supply power for essential appliances. I guess you're quite happy though to put all your eggs in a basket that will in one months time be technically bankrupt. Those with two separate supplies will at least be able to use some appliances when things go belly up. You probably missed this part as well but your DC appliances are already using two standards as they convert from the wall supply to DC.

But that is still not 12 V

A car charger IS 12V.

Yes - and it contains a DC-DC converter that is creating a higher voltage. As per the specs: "Output: DC 15/16/18/19/20V 4A DC 22/24V 3.3A 80W Max"

DC-DC converters are at least as inefficient as AC-DC switch-mode power supplies - often far worse.

Again not the point but to counter your argument you are already using an inefficient means of conversion from AC for all your DC appliances. Running AC from a DC source through an inverter is even less efficient. Switched mode power supplies are more efficient than your current transformer based step-down tech you are using in almost every DC appliance.

Your lack of knowledge and arrogance is growing tiresome.

Voltage drop is due to resistance. There is some resistance in the source (power supply), some in the cable and normally the majority of the resistance is in the load. The biggest reticulation challenge however is the resistance in the cable. Voltage drop is highest when the current in the cable is high. This will happen when trying to trying to carry too much power at too low a voltage. The way to combat that is to reduce the current - but if you still need a significant amount of power then you need to raise the voltage.

12 V is too low to reticulate usefully for more than about 20 metres unless you have extremely thick and expensive cabling. The only reason 12 V is popular is due to its use in cars and thus with cheap lead acid batteries and cigarette lighter accessories. Most industrial and business grade DC systems use either 24 V or 48 V.

And you are grasping at straws. The voltage drop at source is not due to resistance but rather that it supplies power as a factor of voltage and current commonly known as wattage. Drawing more current from a supply where this is limited therefor results in a voltage drop. This typically doesn't affect lead-acid batteries though as they can usually supply several hundred watts.

Voltage drop in a wire is negligible for small distances like house wiring and it isn't unique to DC. AC systems also suffer from this and even more so due to the skin effect. Since this is unique to AC systems DC current can flow through the entire diameter of a wire thereby decreasing the resistance and voltage drop.

 

[itareanlnotani]

And you are grasping at straws. The voltage drop at source is not due to resistance but rather that it supplies power as a factor of voltage and current commonly known as wattage. Drawing more current from a supply where this is limited therefor results in a voltage drop. This typically doesn't affect lead-acid batteries though as they can usually supply several hundred watts.

Um no.

Impedance is what drives the voltage drop, not the source.


I specifically asked a question which would have led you to the right answers -

It quite obviously won't be sufficient for most applications as has been pointed out repeatedly at length by myself and others, and the solution for that is running at higher DC voltages. DC works for low current draw, at short lengths. If you have higher current draws, the voltage loss is high at standard cable lengths. Assume you have 20m from your DB. Calculate the voltage drop over the size cable you'd need to run a 500w computer. Or a kettle. Or a vacuum cleaner. Or a tv. Or anything really that uses a few hundred watts of power.

Power (Watts) = Voltage x Current (Amps)

500w / 12v = 40Amps.

Go visit here -> http://www.calculator.net/voltage-drop-calculator.html

House wiring is typically 12 gauge wire ( 20amp @ 240v )
Lets say 20M distance from the DB to the plug where the computer is.


Our calculator says

Voltage drop: 8.34v
Voltage drop percentage: 69.50%
Voltage at the end: 3.66v

Thats insufficient to run our 12v device. Waaaay insufficient.


Calculator for that example


Please feel free to run some calculations and learn something about what we're all trying to explain to you.

Now, I know you're going to say, ah, but I'm not going to run hundred watt devices on my DC cabling.
Well, are you going to run a cable from the DB to each plug? (rewiring a house isn't cheap).
Or multiple devices on one circuit? (higher amp usage).

(Much) Higher voltage DC is the only sensible option to this, or stick to AC.
Low voltage DC is only useful in a handful of specific situations.


I'm going to give it one more go (this one), and see if I can't teach you something. If not, I recuse myself from this thread, as you obviously aren't willing to learn something, despite many people trying to teach you otherwise.

I'll give you one out though - IF however, we manage to invent room temperature superconductors, then we can do the DC runs like you say. May take a while for science to get to that point though.

 

[Swa]

I'm sorry you feel that way.

 

[Paul_S]

The point is to be self sufficient and not rely on an external utility to supply power for essential appliances. I guess you're quite happy though to put all your eggs in a basket that will in one months time be technically bankrupt.

Tomorrow I could:
Go buy a 240V generator with AVR tomorrow to be self-sufficient.
Go buy a 12V to 240V inverter that I can run off a car battery and be self-sufficient (run the car to keep the battery charged).

In a couple of weeks I could set up a solar PV system.
The best thing of all is that I won't have to replace a single appliance in my entire house because they just all happen to be powered from 220-240V AC.
Why would I want to start running dual feeds around my house to become self-sufficient?

Those with two separate supplies will at least be able to use some appliances when things go belly up. You probably missed this part as well but your DC appliances are already using two standards as they convert from the wall supply to DC.

But we can already do that. Pop into Makro and buy a generator with AVR and if you're really concerned run it through a line interactive, pure sinewave UPS.
That way you can power all your appliances an not just the ones which expect 12V.

 

[Sonic2k]

I have never in my life, read so much bull**** as what is written in this thread.
Darwin is strong with this one.

As for a little bit of info, I started my business based on the fact that my erstwhile employer actually fell for the snake oil and other crap they were offered by so-called local inventors. One of them was this supposed 12V DC kettle. It never worked, and that dude that tried to coin it from my then employer is now missing in action. That is why I left, because I became unpopular at work, because I was the only one with 1/2 a brain debunking all this flux capacitor crap being offered to my employer and they thought I was just being difficult, meanwhile I was not prepared to waste my time with this crap.

Transformers in appliances converting to DC is indeed wasteful. What very few consider is that the motor in your computer's hard disk is actually a 3-phase AC machine. So if DC was soooo wonderful, then why don't they use DC motors. That would sure as hell make hard disks 30% cheaper.

 

[itareanlnotani]

I will say that a workable 12v DC kettle shouldn't be too hard to make - 12v @ 200A would do the 5 min 1litre to boiling at a guess (haven't done the math though).

May be a tad unfeasible in real life though for fairly obvious reasons (cable thickness, amp requirements etc)

Most of the available 12v Kettles appear to be 12v @ 10A or 20A. They won't be doing much more than a cup of water at what sort of output. Would be better to use gas for that sort of situation. Or in our climate, a small solar still, as that would work very well given sunlight availability.

 

[The_Unbeliever]

As for a little bit of info, I started my business based on the fact that my erstwhile employer actually fell for the snake oil and other crap they were offered by so-called local inventors. One of them was this supposed 12V DC kettle. It never worked, and that dude that tried to coin it from my then employer is now missing in action.

A-ha! There you have it. It just is not feasible.

Wonder why he is MIA? Borrowed too much money?

 

[richjdavies]

Wonder why he is MIA?

Probably like the guy who started the thread -- after installing one 'system' for someone, the guy probably realised it wasn't the panacea he sold it as and got lots of demands for money back.

It's surprising quite how many people do spin so many falsehoods about electricity; although I expect it's not too different from muju, cars, money generally... it's not necessarily lying, it's just they don't know any better... and can make a quick buck telling others!

To sum up the thread so far:
- Wouldn't it be great if we could make all our own electricity at 12V...
- Yes it would be great... but you don't need do make it all DC to do that
(lots of rambling about voltage drops and bad maths later)
- But you wouldn't want to run your whole house on 12V... (kettle, vacuum)
- No you wouldn't would you... so what were you talking about in the first place

Basically, yes, we can be 'self sufficient'; making everything DC wouldn't change all of that.

It's like saying, I'm sick of having to wait for the Bus, I think I'll buy myself a Car. And then saying it HAS to be a Diesel* car... because Diesel is a bit more efficient than Petrol. It's based on a truth (diesel is more efficient), but the truth doesn't align to the reasoning... (that you want a car)

* = if diesel wasn't available anywhere and couldn't use the same roads as petrol cars...

 

[Swa]

Tomorrow I could:
Go buy a 240V generator with AVR tomorrow to be self-sufficient.
Go buy a 12V to 240V inverter that I can run off a car battery and be self-sufficient (run the car to keep the battery charged).

In a couple of weeks I could set up a solar PV system.
The best thing of all is that I won't have to replace a single appliance in my entire house because they just all happen to be powered from 220-240V AC.
Why would I want to start running dual feeds around my house to become self-sufficient?



But we can already do that. Pop into Makro and buy a generator with AVR and if you're really concerned run it through a line interactive, pure sinewave UPS.
That way you can power all your appliances an not just the ones which expect 12V.

We did that. It costs more than R100 for a tank of petrol and then it only runs for 10 hours at most. Talk about throwing the baby out with the bathwater. PS: You're still not self sufficient.

I have never in my life, read so much bull**** as what is written in this thread.
Darwin is strong with this one.

As for a little bit of info, I started my business based on the fact that my erstwhile employer actually fell for the snake oil and other crap they were offered by so-called local inventors. One of them was this supposed 12V DC kettle. It never worked, and that dude that tried to coin it from my then employer is now missing in action. That is why I left, because I became unpopular at work, because I was the only one with 1/2 a brain debunking all this flux capacitor crap being offered to my employer and they thought I was just being difficult, meanwhile I was not prepared to waste my time with this crap.

Transformers in appliances converting to DC is indeed wasteful. What very few consider is that the motor in your computer's hard disk is actually a 3-phase AC machine. So if DC was soooo wonderful, then why don't they use DC motors. That would sure as hell make hard disks 30% cheaper.

Yes Darwin is indeed strong and your example makes no sense. The rest of your hard disk runs on DC. The fact of the matter is we need both but somewhere someone decided we should only have AC and convert from there to DC which is what most appliances now use. And FYI that motor in your hard drive is technically called a stepper motor. It's a DC device that works by transferring power to different coils so it's much more complicated than 3-phase AC.

 

[wetkit]

Bottom line.....
We need both DC and AC power.
Each one have it's advantages and it's disadvantages.

Generation:
Here AC is the king.

Transmission lines:
Here DC is actually the king, but the cost and size of the protection gear makes it uneconomical.

@Home:
Use whatever you like, but copper is where the cost is. Using AC is just more economical and we already have set standards for that.

The OP is welcome to use DC in his home, but his got to wire it himself....

 

[ToxicBunny]

@Home:
Use whatever you like, but copper is where the cost is. Using AC is just more economical and we already have set standards for that.

The OP is welcome to use DC in his home, but his got to wire it himself....

Actually legally I'd question whether the OP is welcome to use DC in his house in the way he invisages... I doubt he'd be able to get an Electrical Compliance certificate...

 

[Swa]

Actually legally I'd question whether the OP is welcome to use DC in his house in the way he invisages... I doubt he'd be able to get an Electrical Compliance certificate...

A lawyer is welcome to chip in here but from what I can gather regulations and a compliance certificate are only applicable to mains current.

 

[ToxicBunny]

A lawyer is welcome to chip in here but from what I can gather regulations and a compliance certificate are only applicable to mains current.

They'll be applicable to any electrical installation in your house.

 

[ToxicBunny]

A lawyer is welcome to chip in here but from what I can gather regulations and a compliance certificate are only applicable to mains current.

They'll be applicable to any electrical installation in your house.

 

[Swa]

They'll be applicable to any electrical installation in your house.

Yet they aren't.

 

[ToxicBunny]

Yet they aren't.

You may want to argue that point with your insurance company after the deny your insurance claim...

 

[ToxicBunny]

Yet they aren't.

You may want to argue that point with your insurance company after the deny your insurance claim...

 

[Swa]

You may want to argue that point with your insurance company after the deny your insurance claim...

Insurance companies have to act withing the laws and regulations.

 

[Billy]

* = if diesel wasn't available anywhere and couldn't use the same roads as petrol cars...

Best suggestion on the thread!

 

[Swa]

I hope the naysayers in this thread are sleeping comfortably: http://mybroadband.co.za/news/energy/116738-sa-on-brink-of-total-blackout-eskom-ceo.html