Future: DC yes, AC no?

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June 23rd, 2016 at 1:36:36 PM permalink
odiousgambit
Member since: Oct 28, 2012
Threads: 73
Posts: 1571
One thing about AC I thought I knew seems not true: that it was preferable for power transmission because DC would require gigantic copper wires.

If I understand modern electrical engineer's thinking on the matter as given in the article, it was the practicality of ginning up the voltage that was the problem, along with other problems that now have solution. Note that the Chinese are opting for DC power transmission in at least one case, along with some US plans in the west.

http://www.extremetech.com/extreme/142741-tesla-turns-in-his-grave-is-it-finally-time-to-switch-from-ac-to-dc/2
The light at the end of the tunnel is often a freight train coming the other way! per Fleastiff
June 23rd, 2016 at 4:01:32 PM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 736
Posts: 8585
Quote: odiousgambit
Note that the Chinese are opting for DC power transmission in at least one case, along with some US plans in the west.


China now has 7 of the top 10 largest HVDC projects in the world. Two of the remaining 3 are in Brazil.

Historically one of the largest HVDC projects in the world was started under JFK in the 1960's to supply LA basic with cheap hydroelectric power from Washington state.


The proposed Energy superhighway for the USA is a network of 765-kV lines, but as to how much they will use DC is still debated.


HVDC is very important for underwater power cables in Europe.


But the idea of bringing DC straight to the home is pretty radical, although proponents include Google who favors delivering 12V DC to the home and changing building codes.



Of course a 12V DC microwave costs $300.
June 23rd, 2016 at 4:05:09 PM permalink
Nareed
Member since: Oct 24, 2012
Threads: 329
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You can change anything you want, so long as existing installations and appliances work without changes.
If Trump where half as smart as he thinks he is, he'd be twice as smart as he really is.
June 23rd, 2016 at 4:34:03 PM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 736
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Quote: Nareed
You can change anything you want, so long as existing installations and appliances work without changes.


Just out of curiosity how much electricity do you use in a month in Mexico. You don't seem to use electricity for heating water or heating the home or cooking food. I assume that you just have refrigeraters and air conditioners.

How about lighting? Are LED bulbs commonplace now? They are often subsidized in the USA by power companies so they are inexpensive to purchase.

Quote: Living With a 12V DC Home Power System

Low Voltage Appliances

Just about any appliance that you can imagine having is available for 12-volt living. You'll discover quickly that these items are somewhat more expensive than their 120V AC counterparts, but they're generally quite well made. Low-voltage items should last for decades with an occasional replacement of brushes in their motors. Furthermore, 12V DC brushless motors are gradually becoming available, which should make the low voltage appliances virtually maintenance-free.

Modern 12-volt refrigerators are true marvels. They can do with 500 watts what your run-of-the-mill home icebox takes 3,000 watts to get done. But, as you'll discover when thumbing through catalogs, this incredible efficiency doesn't come cheap. The ArcticKold, Marvel, and Sun Frost refrigerator/freezers all retail for between $1,500 and $3,000. For the low-voltage home, however, the only commercial alternative to these units is to find an absorption-cycle icebox that runs on a fossil fuel. The Sibir, which is sold by Lehmann Hardware, appears to be a fine unit. There are also used refrigerators around that run on propane or even kerosene.

The only 12-volt washing machines we've come across are conversions of standard machines from companies such as Real Goods Trading Company or Windlight Workshop. This isn't as difficult as it sounds: Just about any wringer washer can be converted easily, and conversion kits are available that help you to alter many popular modern machines. David Copperfield's book, Convert Automatic Washers to 12 Volts, is also helpful.

Television and home entertainment systems are no problem at all. Quality 12-volt color and black-and-white televisions are readily available from recreational vehicle suppliers, and automotive stereo systems can rival the fidelity of the best 120-VAC equipment.
June 23rd, 2016 at 4:44:36 PM permalink
Nareed
Member since: Oct 24, 2012
Threads: 329
Posts: 11371
Quote: Pacomartin
Just out of curiosity how much electricity do you use in a month in Mexico.


To effing @#&!! much.

Sorry, I just paid the last bill, and it was about US $180 for the past two months. It's outrageously high.

Quote:
You don't seem to use electricity for heating water or heating the home or cooking food. I assume that you just have refrigeraters and air conditioners.


IMO A/C in Mex City for a home is superfluous. There are a few hot days in Spring (not in summer. summer is rain season and the constant cloudiness keeps the heat down), and they're not that hot.

Quote:
How about lighting? Are LED bulbs commonplace now? They are often subsidized in the USA by power companies so they are inexpensive to purchase.


Ugh! There was a subsidy offered a couple of years back (it's gone now), but at the time you couldn't find soft light if the world depended on it. I hate cool light. But prices have come down a bit and I got a few recently to test.
If Trump where half as smart as he thinks he is, he'd be twice as smart as he really is.
June 23rd, 2016 at 6:14:24 PM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 736
Posts: 8585
Quote: Nareed
To effing @#&!! much.

Sorry, I just paid the last bill, and it was about US $180 for the past two months. It's outrageously high.


That would be the cost of ~ 1270 kWh plus customer fees where I am from, but the price is much higher in a large city. An average home in the USA uses closer to 2000 kWh in two months. Of course, average has very little meaning. A home in Maine uses very little electricity because they need no air conditioning and it is way too cold to have electric heat. The price of electricity is very high in California or Hawaii or NYC. Kentucky and Tennessee use a lot of electricity because they tend to both heat and air condition their homes with electricity since the climate is about in the median for the country.

I pay $0.1192 per kWh or roughly 2.226 pesos per kWh plus monthly customer fee of $14.27 or 267 pesos. Monthly billing is common here, but I understand that being billed every two months is more common in Mexico.

I have read that some Mexican homes have a high voltage which can artificially inflate their electric usage. Also that they tend to have more tiered rates. Instead of $0.1192 per kWh, you might pay three different rates for the first 150 kWh, the second 150 kWh, and the everything that exceeds 300 kWh.

June 24th, 2016 at 8:17:03 AM permalink
DRich
Member since: Oct 24, 2012
Threads: 18
Posts: 765
Our rates in Las Vegas are similar to California. We pay about $0.11 kwh. We used about 3100 kwh this past month and it will probably be near double that this month because of the high temperatures. Although we use so much, we do not turn our thermostat below 78F. The two air-conditioner units are running about 80% of the day now just to keep it at 78F.
June 24th, 2016 at 9:25:14 AM permalink
Pacomartin
Member since: Oct 24, 2012
Threads: 736
Posts: 8585
Quote: DRich
We used about 3100 kwh this past month and it will probably be near double that this month because of the high temperatures.


That's about 100 kwh per day. Nareed would go into shock if her usage passed 100 kWh in a day. We only went above 100 kWh for seven days last year in Pennsylvania (6 in the winter).

Sat, Jan 17, 15 118.5 kWh
Sun, Jan 18, 15 109.5 kWh
Thu, Jan 29, 15 127.3 kWh
Mon, Feb 9, 15 111.5 kWh
Fri, Feb 20, 15 107.5 kWh
Sat, Feb 21, 15 140.5 kWh

Mon, Jul 20, 15 127.8 kWh
June 24th, 2016 at 9:44:39 AM permalink
Nareed
Member since: Oct 24, 2012
Threads: 329
Posts: 11371
Quote: Pacomartin
I pay $0.1192 per kWh or roughly 2.226 pesos per kWh plus monthly customer fee of $14.27 or 267 pesos.


I pay 3.356 pesos, which is around $0.17 with today's devalued rate (thank you British bigots!!)
If Trump where half as smart as he thinks he is, he'd be twice as smart as he really is.
June 24th, 2016 at 10:23:52 AM permalink
kenarman
Member since: Oct 24, 2012
Threads: 3
Posts: 930
Quote: Pacomartin

But the idea of bringing DC straight to the home is pretty radical, although proponents include Google who favors delivering 12V DC to the home and changing building codes.



Of course a 12V DC microwave costs $300.


Bringing 12VDC into the house is not a technically viable option right now. We have too many appliances that use too much power to distribute it economically. A 1500W appliance will draw 100 amps and needs an appropriate size wire to feed the receptacle for it.

If we all are able to scale back and live like those who are off the grid and survive on solar it might become possible. Currently even many "off the grid" homes still fire up the gas generator so they have enough power for wash day.

Most 12VDC electronics we use today are not designed for a larger capacity 12V service feed. They don't have the fusing or self limiting circuitry to protect themselves from anything but the limited output 'wall wart' they come with.
"There is no sin but ignorance" Christopher Marlow
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