Load Shedding and Time Shifting Activities

by Bryan A. Thompson

Last Updated 2/10/03

Overview

Remember the TV show Green Acres?  Electrical power was limited in the Douglas household.  They numbered each electrical appliance according to its power requirements.  They had to remember to only plug a total load of "7" or less, or the fuse on the pole blew.  Well, it turns out that the same techniques apply to any situation where power is limited. 

 

Load-Shedding

It is possible to use a generator or power inverter with a peak power capacity much lower than the peak electrical load if load-shedding techniques are used.  This is essentially switching off power to lower priority devices (this is called a "load shed") so that power can be directed to high power loads such as an electric heater, hair dryer or microwave.  In order to power high-priority loads (computer, clock, phone, etc), UPSes were incorporated.  When generator / inverter power capacity is less than the peak power load requirements, power must be redirected from low-priority and high-priority loads to high-power loads, the UPSes ensure that high-priority devices continue to receive power.  Depending on the length that the peak load lasts, it may be necessary to modify the UPSes for longer run-time.  More information about UPS modifications can be found here.

Unplug everything you're not using!  Lots of devices consume power whether they're on or not.  These devices are anything that uses a wall transformer, devices that can be turned on by remote control, computers with ATX power supplies, anything with a standby light, etc.

 

Implementing Load Shedding

There are UPSes (the Tripp-Lite RM1500 is one) that are capable of prioritizing loads and shutting down non-essential loads as energy becomes more scarce.  It also allows outlets to be shut down remotely if need be.

 

Time-Shifting Activities

It is possible to minimize peak electrical energy usage by time-shifting some activities.  I decided that I could probably live without the electric heater and the George Foreman Grill at the same time, and that I could probably live without AC while I was cooking.  I don't need the TV and computer monitor on at the same time.  By planning these activities, I reduced the peak electrical demand in my apartment from over 8KW to less than 1500W, allowing me to conserve energy and buy a smaller generator.