How will people cope when the brown-outs and rotating blackouts begin to illuminate the wisdom of Lovins and Colmoner?
They will cope¾just as Europeans coped in World War II, and as people are still coping in the Soviet Empire, where electric power is not produced for profit, but planned by bureaucrats. Hospitals have their own emergency diesel generators; so do radio and TV stations, and of course, so do police and government agencies, for as illustrious sage Lovins tells us, it is abundant energy from concentrated sources that locks us into a system with big government.
Housewives get up at 2 a.m. to bake a cake, so that its precious flour and milk are not wasted by the power or gas going off when it is in the oven¾and that is more likely to happen during the day or in the evening.
All of this is well known to those who have lived through power shortages. But there is also a new aspect: What happens to computers when the power is turned off? The information lost in the data processors can be incomparably more precious than a little dough in the oven. Moreover, unlike a hospital or TV station, a computer cannot afford to wait a few seconds before a diesel generator goes automatically into operation and reaches full speed. It can't even afford half a second¾during which it may perform a million operations.
The simplest way to avert disaster is to have a small reservoir of power (perhaps only the charge on a large capacitor) and a sensor that beats the alarm when the voltage is dropping and about to disappear. The computer will then interrupt the program it is executing and will quickly store all critical information (including the point where it was interrupted) in a non-volatile memory, that is, in memory that does not go blank when the power is turned off. Magnetic tape and disks store information indefinitely (as do printouts on paper), but since recording on them involves mechanical transport, they are far too slow to save information in a fraction of a second. However, magnetic core memory is accessed only electronically, and unlike semiconductor memory, it is non-volatile.
Such emergency storage will avoid loss of information, but not loss of time during which the computer stands idle. (Processing time can run $1,000/hr and more). To keep going when the power fails, one needs not only a standby source of power (usually storage batteries), but also an arrangement that will switch over from utility power to the standby without even a nanosecond (1 billionth of a second) of interruption.
This can be done electronically, but there is also a mechanical system which has proved simple and reliable (though not noiseless). It is a motor and generator on the same shaft, the motor being run by utility power, and the generator powering the computer. If the power driving the motor fails, sensors will detect this and switch to the standby power supply. There is plenty of time to do the switching, for mechanical inertia will keep the motor-generator turning for many seconds, when all that is needed for the switching is a few milliseconds.
[More: "Uninterruptible power systems," Digital Design, Feb. 1980.]
|
Vol. 7, No. 8
Newsletter: Access to Energy Newsletter Archive Volume: Volume 7 Issue/No.: Vol. 7, No. 8 Date: April 01, 1980 03:23 PM (For actual publication date see newsletter.) Title: Anniversary of the Grand Disaster
Copyright © 2004 - Access to Energy Newsletter Archive
|