In an era of stressed watersheds and aquatic ecosystems rendered
fragile by global warming, we’re learning more about our hidden water
use. For instance: 42 gallons – that’s the water footprint for the
average kilowatt-hour of U.S. electricity as of 2009.
OK, it’s nothing compared to how much water it takes to produce a big, juicy hamburger – that’s at least 4,000 gallons [PDF] – but then again, you consume a lot more kilowatt-hours of electricity in a day than you do hamburgers. Presumably.
In fact, the average U.S. home uses around 1,000 kWh of energy every
month, which means – according to a report from the Portland, Ore.-based
River Network – it takes an average of 39,829 gallons of water to meet
our monthly energy use, five times more than our direct residential use
of water.
The staggering water requirements of our current grid electricity are
just one more reason to embrace water-sparing renewables, the group
argues in “Burning Our Rivers: The Water Footprint of Electricity” [PDF].
“Expanding the deployment of wind energy and photovoltaic (PV) solar power could vastly reduce wateruse conflicts in some regions,” they write.
Some might argue that not all or even most of the water used to make
power from traditional sources like coal, nuclear and natural gas is
used up in the process of creating the energy. But that ignores one of
the great sins of power production, River Network says: once-through
cooling.
The water that is used to cool down conventional power plants might
largely be returned to its source, but not without repercussions. “Some
of this water is evaporated while the majority of this water is warmed
up – causing thermal pollution – killing aquatic life, increasing toxic
algae blooms and decreasing the sustainability of our water supplies.”
Furthermore, the biggest source of electricity in the U.S., coal,
takes this impact a step further because “immense amounts of water are
used or polluted to mine, wash and transport coal before it even reaches
the power plant, while even more water is used to consumed at the power
plant.”
River Network has a lot of recommendations for fixing the problem,
including deploying better cooling technologies. But it’s the
endorsement of wind and PV that lead its long list.
“Wind and PV solar require virtually no water to generate
electricity, and their lifecycle water footprints are far smaller than
hydro, nuclear or fossil fuels,” the report states. “The technology
exists for wind to provide 20 percent of our electricity by 2024.”
It does take some water to make wind turbines and solar panels, but
not much. Weighted by production, River Network puts hydroelectric’s
contribution to the total water footprint of electricity at 29,920
gallons; coal’s at 7,143 gallons per megawatt-hour; natural gas at 1,512
gallons/MWh; and nuclear at 2,995 gallons/MWh. PV, meanwhile, comes in
at 2 gallons/MWh, and wind at just 1.
“Since the majority of the water used by wind and PV solar is
‘upstream’ (to acquire and process materials for fabrication),
manufacturing can be focused in water rich regions without increasing
water impacts in dry regions,” the River Network report says.
No comments:
Post a Comment