Starting on developing a 10 acre permaculture homestead in a sub-urban area. see http://www.my10acres.info
Jerry Ward wrote:
Some problems/issues I see:
1. You lose efficiency trying to send a lot of current via DC unless you use REALLY thick wire. But most of the devices I'm talking about are low current.
2. There is no "standard" DC voltage. I have stuff that goes from 3V-24V and changing voltage in the DC world is a hit in efficiency
3. It would be a pain to retrofit an existing house to run both AC & DC to each room.
Advantages:
1. You could have a good sized battery that is intermittently recharged from the grid. This would keep these electrical device up and running during a power outage, how long depends on the size of your battery.
2. All of the individual transformers at every device could be eliminated.
3. Easy to add alternative energy since most of it is DC and could be feed directly into your house without needing to go through an inverter.
Unknowns:
1. How much power would you really save? Many of these DC devices are very low power users. I suspect that many times the wall wort transformer wastes more power then the device actually consumes. Would you ever save, for example, the amount of energy it takes to make the additional copper wire you are using to distribute this DC power?
2. I know I should put such transformers on some kind of switch and turn it off, but this is an area I just plain lazy and will not likely do it. Plus things like a clock you need powered up all the time. Maybe the solution is to put batteries in these devices and recharge them as needed, unplugging the charging transformer when not in use. But the device would stay up and running without constantly running a transformer.
Some food for thought and I welcome all comments. My real understanding on this stuff is over 25 years old, back when I was in electronics classes. Some things remain the same, but I sure others have changed. I started thinking about this again because I just got a new 32" LED TV and it has a transformer with a very small wire running from the transformer to the TV. Just based on the cord size I would say this consumes less than 1/10th the power of the old CRT's.
My $.02 worth (well maybe $.05)
Kull Conquered wrote:If you used solar power this would make some sorta of practical use. The problem with just doing it is you have to go through a conversion from AC to DC so you are already losing if you do it in real time. You could charge batteries, but it becomes complicated. DC batteries don't do well with high voltages (they explode), so you have to step down, or voltage divide. Voltage dividing is worse than using a transformer because you bleed it off in heat.
I would have DC sockets for the common voltages at each socket. It would be something like 3,5,9,12 (have to research it a bit). You could even have an "odd one" where you voltage divide with a potentiometer and mark the voltages. You can achieve this by just using several batteries that allow you to stack the voltages. You tap in where you want what voltage. The farther up the chain, the higher the voltage. You prevent the voltage from increasing by using diodes between the batteries.
The most difficult part is actually by-passing the power section in all the stuff you have that does not have an adapter outside of itself. In many cases this would require you to have a decently intimate knowledge of the power section so you can feed right into the output (most likely connect to capacitors that are right after diodes). You can't bypass the power section because many of today's electronics actually run on several different voltages within themselves. This requires a schematic... some are free others cost you. They can cost more than some devices are worth. The other way around is using a multimeter to find out what voltage is after rectification; that you have to duplicate off the wall.
The price of refrigerators, washers, dryers, blenders, and anything with an electric motor would become astoundingly expensive. They can run on DC motors but DC motors are instant on-off things that can go in reverse. Even if you put in fail-safes to prevent people from totally screwing them up, it would cost money. The bearings in them have to much, much better. The overall build is of an entire different quality. In commercial settings they can turn on and reverse thousands of pounds back and forth like it is nothing, on a dime, in an instant, but they machinery has to be built to handle that stress.
Kull Conquered wrote:You make it sound simple... but that is very complicated and beyond most means.
I think you might be surprised at the different voltages of wall warts. (and the switching ones are ok but too noisy for many applications)
Uh I would would want to check that anything runs off 100v or even near it off the rails (rectification). They have transformers. You have to step that down and skip the transformer or you are not doing anything but being as wasteful as with AC. Computers these days have 3.3, 5, 12, -12 in them from the power supply
Hand tools that use DC are battery powered, and most are worthless compared to their wall powered counter parts. Good drills (cordless) run on 18v; anything else is just wimpy these days.
The point of voltage dividing is to remove inefficiencies of anything between power source and the thing being used. Also noise is kept at zero, enhancing the life and fatigue level (for the user) of all electronics.
Personally I think AC is pretty darn good as is for what we need, on grid. Perfect, no, versatile? Very. Problems? Using it for heat... excessive stupid stuff, low build equality making things less efficient.
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velacreations Hatfield wrote:we wired our house with both DC and AC, because we run completely off a solar/wind system.
All lights are DC, as well as the fridge, deep freeze, and water pump. We have DC car adapters for the computers.
We did it this way in case of inverter failure (we've had several in the decade we've been living like this).
So, each plug int he wall is actually 2 plugs. One AC and one DC, and they are marked accordingly.
Len Ovens wrote:
DC plugs are 12V? What kind of socket do you use? RVs seem to use the cigar lighter style.
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velacreations Hatfield wrote:
Len Ovens wrote:
DC plugs are 12V? What kind of socket do you use? RVs seem to use the cigar lighter style.
Yes, our DC plugs are 12V, straight from the battery bank. We use regular 2 prong plugs for this, but mark them 12VDC, and they are a different color.
We modify the cords on things to make them work.
We tried the cig lighter adapters initially, but found that they wear out fast, usually making a bad connection, then heating up and melting the plastic casing.
Do you have any fusing/breakers between the battery and the receptacle? Generally ac style breakers are good for dc use up to 24 volts. They normally have the ac and dc voltage rating printed right on them. These are what I used in our boat for nav lights and instruments. I found a bunch of small amp breakers in machines we were removing. (1 to 5 amps) Saved them from the dump.
I would have thought to use 3prog, just because they can only be plugged in one way. Some of the two prog plugs have two blades the same size. A bridge rectifier in the plug would protect from that too.
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velacreations Hatfield wrote:
Do you have any fusing/breakers between the battery and the receptacle? Generally ac style breakers are good for dc use up to 24 volts. They normally have the ac and dc voltage rating printed right on them. These are what I used in our boat for nav lights and instruments. I found a bunch of small amp breakers in machines we were removing. (1 to 5 amps) Saved them from the dump.
We use 12 vDC breakers and fuses. You have to be careful using AC stuff, cause DC is hard on the contacts.
Kull Conquered wrote:Strange... I would of never thought that hand held grinders where DC.
I think you confused my idea of a voltage dividing scheme with a traditional one that would use resistors. My suggestion has no resistors, no efficiency loss.
The only thing in the circuit would be diodes and batteries. Instead of starting with a higher voltage and dividing down, you start with the lowest battery voltage you want and add more to increase the voltage. You use the diodes to prevent power taps earlier on at lower voltages from gaining voltage from the rest of the batteries in the circuit. So you could have a 3v, diode, 2v (to make a total of 5v), diode, 4v, diode, 3v. Giving you 3, 5, 9, and 12 voltages available. Obviously the 12v would have more amperage available. This is just an idea to suit the many needs of different voltages things require.
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