Page - 48 - in Water, Energy, and Environment - A Primer

and a 10,000 hour lifetime for the LED, which means that you replace the incandescent bulb five times more often than the LED. We will also assume the cost of electricity to be $0.10perkWh. Thus, after 10,000 (104) hours the cost of operating with incandescent bulbs, including the purchase costs for 5 bulbs, would be: $5+ (0.1kW)× (104h)× ($0.10/kWh)=$105. The cost of operating the LED would be $10+ (0.011kW)× (104h)× ($0.10/kWh)=$11. This comparison, even without considering labor costs, shows why the switch from incandescent bulbs to LEDs is inevitable and now taking place rapidly. Utilities also benefit because they will need fewer power plants tomeet lighting electricity requirements, as well as reducing environmental impacts of power generation. Given that lighting consumes a significant fraction of global electricity, the benefits of this lighting revolution in combating globalwarming and climate change are obvious. 5.5.7 Energyefficiency inbuildings Buildingsaccountforapproximately40%oftheenergy(electrical andthermal)consumedintheUSandEurope,andabout30%ona global basis.Most of this energy today is fossil-fuel based.As a result, this energy consumption accounts for a significant share of global emissions of carbon dioxide. Thismakes it imperative that buildings be a primary target for reducing energy and fossil fuel demand. 5.5.7.1 Zeroenergybuildings One approach that is gaining visibility is the introduction of net zero energy buildings (ZEBs) and the retrofit of existing buildings to approach net zero energy operation.AZEB ismost often defined as a building that, over the course of a year, uses asmuch energy as is produced by renewable energy sources on the building site. This is the definition that will be considered Water,Energy, andEnvironment–APrimer48