An Energy Decision for the Classroom Computers

The Research Station Report

Room 214 has six desktop computers that students use for research. Between lessons, the computers sometimes sit unused. The school council asked whether changing their settings could save electricity without delaying lessons. A report from the local electricity supplier explained that some electricity supplied to the community comes from burning fuels. Obtaining these fuels uses Earth's resources, and burning them releases air pollution. The council wanted evidence before changing settings throughout the school.

The school's technology team described three choices for idle computers. A screen saver shows changing pictures while the computer keeps running. Sleep reduces computer activity, but the machine still uses some electricity. Shutting down stops normal computer operations, although starting again takes longer. These choices affect what happens between lessons. Students still need working computers when research begins. The council therefore decided to examine both electricity use and lesson readiness.

A trained technician tested each setting on the same six computers for five school days. Each test covered six hours per day. The technician used matching schedules with the same research tasks, amounts of computer-use time, and lengths of idle time. The setting used during idle time was changed. Electricity meters measured the total energy used by the six computers, reported in kilowatt-hours, or kWh. Students read the records; the technician handled plugs and equipment. The graph shows the totals for the three tests.

Each test schedule included 24 planned starts of research sessions. A session counted as ready if all six computers could begin the assigned task within one minute. With the screen saver, 24 sessions were ready on time. With sleep, 23 were ready. With shutdown, 17 were ready. The council's goals were at least 22 ready sessions and no more than 11 kWh during a five-day test.

The tests did not measure fuel use at power stations or pollution in the air. They also did not include evenings, weekends, or other computer models. Before expanding a program, the technology team could test other classrooms. Teachers could record delays, and the school council could review those records alongside electricity measurements.