Environmental Science / Unit 8: Energy Resources
8.6 Efficiency and Conservation
Notes
The cheapest, cleanest energy is the energy that is not used.
- Conservation means using less energy (turning off lights, driving less). Efficiency means getting the same service with less energy (LED lights, better insulation).
- Household examples: LEDs use about 75 to 90% less energy than incandescent bulbs; ENERGY STAR appliances; insulation and sealing leaks; smart thermostats.
- Transportation: higher fuel economy standards, hybrid and electric vehicles, public transit, carpooling, biking.
- Cogeneration (combined heat and power) captures waste heat for useful purposes, increasing efficiency.
- Green building (LEED standards) reduces energy needs.
- The rebound effect occurs when savings from efficiency lead people to use more of a service, offsetting some savings.
- Example: replacing a 60 W incandescent bulb with a 9 W LED used 5 hours per day saves $(60 - 9) \times 5 = 255$ Wh, or 0.255 kWh, per day.
Practice
Which is an example of energy efficiency rather than conservation?
Efficiency delivers the same service using less energy.
A 60 W bulb is replaced by a 10 W LED. Each runs 5 hours per day. How much energy is saved per day?
$(60 - 10) \times 5 = 250$ Wh $= 0.25$ kWh.
A factory captures waste heat from its electricity generation to heat its buildings. This is:
Using waste heat increases overall efficiency.
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