Environmental technology

Audit a workshop light

A drawing bench needs the same light level for 800 hours each year. Its existing lamp draws 50 W. A replacement draws 12 W. Check the illumination at the working surface before assuming the lamps provide an equivalent service. Once that condition is met, the difference in power is 38 W, or 0.038 kW. Multiply by 800 hours to find an annual saving of 30.4 kWh.

Power measures the rate of energy transfer. A kilowatt-hour is an amount of energy. The actual saving depends on operating time, so keep a short log before projecting a full year. If the bench is used for only 400 hours, the estimate halves. A timer or occupancy control changes the running hours as well as the power of the lamp.

Match the timing of supply and demand

Suppose a small solar panel delivers an average of 80 W for three hours in a classroom model. It supplies 240 Wh. A 20 W load needs 240 Wh to run for 12 hours. The totals are equal, but overnight demand cannot draw directly on afternoon sunlight. Storage or a second source would be needed. In a real installation, battery and conversion losses also matter.

Make a table with one row per hour. Record generation, demand and the difference. A positive annual total can conceal a shortfall on a particular day. Label assumed values clearly so that a reader can replace them with measurements.

Look beyond the electricity meter

Consider two designs for the lamp bracket. One can be unbolted and reused when the lamp fails. The other is glued to its housing. Comparing their environmental effects means looking at material extraction, manufacture, packaging, transport, use, repair and disposal. A simple mass comparison alone cannot tell you which design has the lower overall impact.

For a short project, choose one measurable improvement and one possible trade-off. For example, a lighter folded bracket might use less metal but take an extra forming operation. Sketch both versions, specify the same load and span, then propose a test using the forces and materials lesson.