Reply #17: AC/DC

[hunter]

Modern power handling technology makes the distinctions you list much less important. It is often easy, efficient, and economical to switch between AC and DC and back again, even in a throw-away device like a compact fluorescent bulb. In modern compact fluorescents the 60Hz AC current is first converted to DC and then converted back again to AC at a frequency of about 20,000 Hz. Television sets haven't used line frequency for synchronization for a long time now. Clocks often do use line frequency because it is adjusted to be accurate over long time periods by the utilities even though the short term drift can be pretty bad. Larger industrial motors these days often have DC controlers in which the one or three phase power is first converted to DC and then to AC again in order to optimise the motor speed and efficiency.

At the supply end, HVDC systems operating at a million volts or more are a mature technology. HVDC links between, say, the deserts of the Southwest and the rest of the continental United States would be very feasible. The Pacific Intertie linking Los Angeles with the Pacific Northwest was completed in 1970 with a capacity of 1600 MW, and has been upgraded to a capacity of 3100 MW as the technology has improved.