San Francisco’s Secret DC Grid

The last direct-current power lines are being dismantled just as DC distribution seems headed for a comeback

7 min read
PG&E’s Steve Austin draws out  a DC circuit map
Photo: Peter Fairley

Nikola Tesla’s alternating current may have “won” the War of Currents at the end of the 19th Century, but the defeated incumbent—direct-current distribution, aggressively championed by Thomas Edison—endured. As historian of technology Thomas P. Hughes observed in his influential essay on the evolution of large technological systems, the War of Currents ended “not with victor and vanquished, but with the invention of devices making possible the interconnection of the two systems.” Remnants of DC power distribution kept performing their assigned tasks for decades as the AC grid thickened around them.

Keep Reading ↓Show less

This article is for IEEE members only. Join IEEE to access our full archive.

Join the world’s largest professional organization devoted to engineering and applied sciences and get access to all of Spectrum’s articles, podcasts, and special reports. Learn more →

If you're already an IEEE member, please sign in to continue reading.

Membership includes:

  • Get unlimited access to IEEE Spectrum content
  • Follow your favorite topics to create a personalized feed of IEEE Spectrum content
  • Save Spectrum articles to read later
  • Network with other technology professionals
  • Establish a professional profile
  • Create a group to share and collaborate on projects
  • Discover IEEE events and activities
  • Join and participate in discussions

The Unsung Inventor Who Chased the LED Rainbow

LEDs came only in shades of red—until George Craford expanded the palette

10 min read
Vertical
Man  with grey hair wearing dress shirt and tie standing in front of an LED stoplight and holding a panel with yellow and red LEDs glowing
DarkBlue2

Walk through half a football field’s worth of low partitions, filing cabinets, and desks. Note the curved mirrors hanging from the ceiling, the better to view the maze of engineers, technicians, and support staff of the development laboratory. Shrug when you spot the plastic taped over a few of the mirrors to obstruct that view.

Go to the heart of this labyrinth and there find M. George Craford, R&D manager for the optoelectronics division of Hewlett-Packard Co., San Jose, Calif. Sitting in his shirtsleeves at an industrial beige metal desk piled with papers, amid dented bookcases, gym bag in the corner, he does not look like anybody’s definition of a star engineer.

Keep Reading ↓Show less