Let There Be Energy-efficient Light

October 22, 2010 at 12:04 pm 2 comments

Let there be light. And TV and DVD and Wii. Let there be laptops with printers and speakers. Let there be microwaves, refrigerators, cell phone chargers, washers and clothes dryers and hair dryers, water heaters, leaf blowers and circular saws. Let there be fax machines, copiers, and projectors for PowerPoint presentations. And, please, let there be A/C and coffee makers.

We Americans rely on electricity to power our lives. We also like to lower our utility bills. So when we hear “Conserve energy,” we’ve learned to turn off the lights, unplug techno toys when not in use, buy energy-efficient appliances. For most of us, conserving energy means using less electricity. Until I asked some of my DEP collegues, I didn’t know that conserving electricity also conserves water.

The average Florida household uses 1,120 kilowatts hours (kWh) of electricity each month and thermoelectric power plants generate most of it.

Thermoelectric power plants burn coal and natural gas or use nuclear fission to heat water. The steam drives a generator to produce electricity.  The water for generating steam comes from nearby water bodies such as rivers or lakes.  Most of the water is returned to its source, but it has to be cooled before being discharged back into the native ecosystem from whence it came, where fishes and other life forms have an aversion to steam baths. Cooling towers lower the water’s temperature, but some of the water evaporates as it cools. How much? The National Renewable Energy Laboratory reported that as much as 0.47 gallons of water evaporate for each kWh of electricity generated.

According to a 2006 U.S. Department of Energy report, water usage at thermoelectric power plants accounted for 39 percent of all freshwater use in the U.S. in 2000, almost as much as that used for irrigating our orange groves, strawberry fields, tomatoes, corn and all sorts of other useful agricultural products.

If you think that’s a lot of water to power our amenities, consider the water budget of a typical hydroelectric power plant.  On a national average, hydroelectric power plants use 18 gallons of water to produce a kWh, about 40 times more than is used to generate thermoelectric power.  These losses arise because reservoirs built to produce hydroelectric power create additional surface area where water can evaporate.

According to the NREL report, the 120 largest hydroelectric facilities in the U.S. lose about 9,063 million gallons of water per day to evaporation.   That’s more than we withdraw for public supply in the entire state of Florida each day. 

Though I don’t know how potential energy in water and a chunk of coal magically shows up to power my toaster, I do know that saving energy saves money. And now I also know that simple actions like turning off the lights, switching to energy-efficient appliances and unplugging electronics also conserve water.

Information provided by:
Daniel M. Kuncicky, PhD  
Environmental Manager
Solid Waste Section
Florida Department of Environmental Protection

Entry filed under: Water. Tags: , , , .

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