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Old 05-27-11, 02:22 PM   #1
Indyplumber
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Default New Ideas for using Alternative Energy

I just had a revelation..epiphany...whatever you want to call it. It has occured to me that we are trying to power current electrical appliances that use 120v AC power with usually 12v DC power running through an inverter. Why hasnt somebody come up with a home system and appliances that use 12v power directly? I realize that stuff like your A/C, dishwasher, and furnace blower need more power and you would need an inverter for those things.

It just seems to me that producing the power is only half of the alternative energy equation. Using it as efficiently as possible should be the other half.

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Old 05-27-11, 02:51 PM   #2
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I don't think its uncommon for off the grid homes to use a 12V power system for some things like lighting.
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Old 05-27-11, 10:44 PM   #3
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The major problem with using 12v is the losses make you end up spending a lot on bigger copper wiring.

A 400w Plasma HDTV 120vac runs 3.33 amps. A 12vdc HDTV running 400w needs 33.3 amps..

The losses I'm talking about is caused by resistance in the wiring.

Watts lost = Resistance x Amps squared.
33.3 squared= 1,111.11 which would be multiplied by the resistance in ohms.
So, if I had about 0.2 ohms resistance in the power cable, the cable would
be heating the room to the tune of 222.22 watts of heat..


If you think about it for a while, you will come to understand,
120vac / 240vac is a pretty efficient power delivery method.
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Old 05-27-11, 11:21 PM   #4
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Those losses in the wiring are great enough that very few off grid homes run 12v so 24v is more common and 36v or 48v is much more common, inverters tend to be cheaper with the higher voltages, you spend less on wire because it's sized smaller and you get more energy because less of it is turning to heat in the wires!
Back when I was a kid, we had 32v lights, power tools, kitchen appliances and so on because 32v is what trains used for many years so when people started getting wind generators 32v became common because you could get a 32v toaster already, but our house also had wiring for 12v, only in a few locations tho because the larger wire cost so much more, but we used it for things that would plug in to a car's lighter plug.
But in a modern house look at how many new electronics work with 120v ac that use less power then there 12v counter part.
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Old 05-29-11, 08:11 AM   #5
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I basically understand wiring sizes and resistance...being a plumber and all lol...but what I was trying to say...and thank for helping me to clarify my thinking...is that there should be more research into making products that use the lower voltages supplied by alternative energy systems. Using your example Xringer, why can't somebody make a 12vdc HDTV that uses less than 400w. (if you are trying to save money, why even buy an HDTV ) Everybody wants to be comfortable, everybody wants to save money. Maybe the definition of comfortable needs to change a little.

Its like the refridgerator. It used to be the biggest energy hog in the house. Now they make ones that use as much power as a 75w light bulb. As the energy supply changes the appliances that use that energy need to change too.
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Old 05-29-11, 08:44 AM   #6
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I can see where the RV market would use those 12V TV sets, but I'm not real sure
about saving a very high percentage over using 120vac.

Plus, some display technology uses voltages higher than 12vdc and the design would
need an inverter or buck booster to increase the voltage.
Look at laptop PCs, some run off 18vdc and use florescent tubes(HV) as a backlight.



I think other things could be done. This PC goes into power save mode,
when I leave it and not come back for a while. Using very little power.

Why not install a people sensor into TV sets? If you leave the room,
the picture starts dimming. If you don't move (IR sensor) or hit the
remote, it gets real dim and goes into standby, until it senses you're back.
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Old 05-29-11, 10:42 AM   #7
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When I wired up my parents house I added low voltage wiring, the spare fridge for extra garden produce is a 24v fridge made by sunfrost, it's still one of the most efficient fridges you can buy and it's 23 years old and I think the wires going to it are either 6 or 8 gauge wire, copper the size of a pencil! and it's a short run of wire.
The low voltage wiring in the rest of their house isn't really used, I put it in for LED lighting because you can get 12v and 24v LEDs for boats and RV's, but that extra wiring is not something I would bother doing again, with switching power supplies you loose such a small amount of energy that it just makes sense to bump the voltage up for going long distances, so while I am sure someone could make or hack more devices to run straight off the lower voltage from an off grid system I don't see it as being worth while.

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Old 06-01-11, 05:34 PM   #8
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I guess what I'm really trying to say is appliances should have their entire electrical architecture reworked so that it uses only 12vdc or 24vdc or something similar. No slapping on inverters or boosters to current technology but developing an entirely new system to use the energy to its greatest advantage. I don't want to re-invent the wheel, I want to make a flying car.
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Old 06-02-11, 08:19 AM   #9
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The direction that solar is going looks to be the micro inverter that is attached to the back of each solar panel so that you can have as short of run of low voltage DC as possible and bumping the voltage up as close to the source as possible, the other thing that is being done is higher voltage DC wiring between panels and inverters or batteries, in my parents solar electric system we wired up the PV panels at 72v and installed a maximum power point tracker that among other things it drops the voltage down to the lower voltage needed for the battery bank (higher voltage battery bank would have been expensive), the panels being wired at this higher voltage reduced the losses enough point to offset the cost of the extra equipment.
Running low voltage wiring any distance is not creating a flying car, it's putting your wheels on a dirt road.
To me, things like switching power supplies that replace transformers are the flying car like devices that we should be looking at because they allow us to push electricity at an efficient high voltage and without alot of losses step it down to exactly what the device needs, after all, even if you did have a device running at a lower voltage you would still need a voltage regulator or a DC to DC converter to give the device the exact voltage that it needed, otherwise the further you get from your battery bank (longer wire run) the dimmer your light bulb is going to be and if that voltage drop is great enough your newer modern electronics will start burning up.

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