More california insanity

[darcane]

Originally Posted by jamesqf

Sure there are: it's called hydro, much of which comes from out-of-state already. (See e.g. https://en.wikipedia.org/wiki/Pacific_DC_Intertie ) Then there's geothermal, which provides 24/7 power. And if all else fails, Elon Musk will be happy to sell you a battery backup system: Tesla Powerwall

Hydroelectricity is not always consistent either. The droughts have really taken a toll on that.

Power capacity at Hoover Dam, on the Arizona-Nevada border, has dropped nearly 25 percent since 2000. In California, home to 287 hydroelectric plants and where almost half the state today is classified as being in “exceptional drought,” hydropower has fallen 60 percent in the past four years.

Western drought steals clean energy along with fresh water at power plants - The Washington Post

Hydro has a love-hate relationship with the environmentalists. They praise it for being clean, and hate it for messing with the salmon. Here in Washington, we've torn down several large dams to improve salmon runs and I'd be surprised if we were ever able to build new dams.

[basjoos]

Originally Posted by UFO

I'm sure you meant AC transmission lines. DC died with Edison.

DC is more efficient for long distance transmission than AC since it doesn't have the wire capacitance losses of AC cycling. Google "dc long distance transmission".

[whatmaycome14]

Originally Posted by basjoos

DC is more efficient for long distance transmission than AC since it doesn't have the wire capacitance losses of AC cycling. Google "dc long distance transmission".

Ok, this goes against everything I thought I knew. Wasn't the reason A/C caught on BECAUSE it was better to travel longer distances??
I just read the Wikipedia article...

Originally Posted by UFO

I'm sure you meant AC transmission lines. DC died with Edison.

It would appear not. I'm amazed. Here a good video on this why D/C is better. (ignore the sales pitch part of it)

https://youtu.be/g17f9J1-r-k

[UFO]

Originally Posted by basjoos

DC is more efficient for long distance transmission than AC since it doesn't have the wire capacitance losses of AC cycling. Google "dc long distance transmission".

Please explain how capacitance causes loss. Capacitance is merely energy storage, it's resistance that causes loss. Yes, RMS losses for the same voltage level are slightly higher, but you have to look at the system as a whole, and it is far less efficient to boost line voltage to 110kV as DC than AC.

[jamesqf]

Originally Posted by whatmaycome14

Ok, this goes against everything I thought I knew. Wasn't the reason A/C caught on BECAUSE it was better to travel longer distances??

That depends on just what you mean by "long distances". Miles, tens of miles, even up to a few hundred, A/C wins, especially at lower voltages. But IIRC long distance A/C transmission lines seldom run over 500 kV (at least as far as I remember, it's been a couple of decades since I worked in the field), while DC can easily go up to a megavolt or more.

There were also other reasons for the success of AC in distribution and small/medium scale transmission, most notably that transformers are pretty easy to build, so system voltages are easily stepped down from the 230-500 kV transmission lines, to 14.4 kV or so distribution systems, and then to the 110/220 volts used in residential systems.

[jamesqf]

Originally Posted by UFO

Please explain how capacitance causes loss.

Ever stood close to (well, not TOO close, though :-)) to a high voltage power line, and heard the 60-cycle hum? That's power being lost. Changing currents (and AC is always changing, by definition) generate electromagnetic radiation, which is energy lost over & above the resistance of the conductor.

...it is far less efficient to boost line voltage to 110kV as DC than AC.

But it is significantly MORE efficient to boost voltage to 1000 kV and send 1000 miles or so as DC, than as A/C.

[H-Man]

Originally Posted by UFO

Please explain how capacitance causes loss. Capacitance is merely energy storage, it's resistance that causes loss. Yes, RMS losses for the same voltage level are slightly higher, but you have to look at the system as a whole, and it is far less efficient to boost line voltage to 110kV as DC than AC.

A capacitor has a resistance (real word is impedance) to an AC waveform. Impedance of a capacitor goes down as frequency goes up.

Longer: If this was a DC voltage, the capacitor would draw current when connected and the current would decrease. If you flip the capacitor around 120 times a second, the DC voltage would have to charge the capacitor 60 times from fully negatively charged to fully positively back to fully negative.

An AC circuit.
May seem like sorcery, but that just explains why every electrical engineer I've ever seen has a beard.

[UFO]

Originally Posted by jamesqf

Ever stood close to (well, not TOO close, though :-)) to a high voltage power line, and heard the 60-cycle hum? That's power being lost. Changing currents (and AC is always changing, by definition) generate electromagnetic radiation, which is energy lost over & above the resistance of the conductor.



But it is significantly MORE efficient to boost voltage to 1000 kV and send 1000 miles or so as DC, than as A/C.

It's not necessary to move power that distance. Yes, AC has losses, but 5% is not that much. DC requires heavier cables, and that means buried lines which is significantly more costly. And again, boosting that voltage is not cheap or particularly efficient compared to AC.

[UFO]

Originally Posted by H-Man

A capacitor has a resistance (real word is impedance) to an AC waveform. Impedance of a capacitor goes down as frequency goes up.

Longer: If this was a DC voltage, the capacitor would draw current when connected and the current would decrease. If you flip the capacitor around 120 times a second, the DC voltage would have to charge the capacitor 60 times from fully negatively charged to fully positively back to fully negative.

An AC circuit.
May seem like sorcery, but that just explains why every electrical engineer I've ever seen has a beard.

A capacitor does not have "resistance" as you say. Impedance is not like resistance in that whatever voltage you charge it, one can discharge it as well. The capacitance of AC transmission lines can be balanced to remove the reactive power losses, so it's false to claim that capacitance is responsible for the power loss -- only on unbalanced lines.

[NeilBlanchard]

Originally Posted by UFO

I'm sure you meant AC transmission lines. DC died with Edison.

No, actually very high voltage DC transmission lines are more efficient than AC.