When people write or talk about clean energy—myself included—climate, economics, and policy tend to dominate the discussion and analysis. The debate gets muddied as climate deniers argue either climate change isn't happening or is not caused by mankind. Further clouding debate is that renewables arguably still don't operate on an equal economic or policy playing field with fossil fuels and nuclear generation sources.
But there's another argument for renewables that can't be denied - or more appropriately, a reality of thermal generation that makes fossil fuel based electricity generation unsustainable and a real threat to long term prosperity: it's thirst for water.
As Minnesota faces swollen rivers and what seems like an unending stream of wet weather, water scarcity hardly seems to be a pressing issue. But as more aquifers and water sources become stressed, water needs to be taken into account when we make long term energy plans.
Think about it - most power plants you see are on rivers or other bodies of water. It's not a coincidence. An average coal plant, for example, depending on its cooling system, withdraws up to 180 billion gallons of water per year, actually consuming up to 1.1 billion gallons per year for cooling purposes.
How much is that? The roughly 400,000 Minneapolis residents (plus some of the surrounding suburbs) use about 8.4 billion gallons of water annually. The city as a whole cleans 21 billion gallons per year for all tap water uses. 1.1 billion gallons for one power plant is not an insignificant amount in comparison.
Now take a look at the following map. Nationally, but particularly in the Southwest, our water systems are becoming stressed - overused to the point that they may no longer recharge and be available in the future. They are also warming, decreasing their use for cooling. Minnesota, despite wet weather right now, also has water systems that are at risk.
Our energy systems already feel the consequences. Low water flow and warmer water from longer, hotter heat waves has forced several power plants to shut down or ramp down capacity. The EPA has also granted temporary permission to some plants to dump warmer than allowed water back into the environment, raising the temperature of aquatic ecosystems even further.
As the planet experiences higher average temperatures combined with growing stress on water supplies, policy makers and regulators will be put in a tough situation - use precious water to cool our power plants, irrigate our crops, or be used for drinking water. Uncertain water supply and and temperature will also impact the reliability of thermal generation output.
Renewables, on the other hand, have a minimal water footprint.
The relationship between water and energy in the U.S. and particularly in Minnesota is not yet a critical threat to energy security and reliability. But the link between water and energy - the "water-energy nexus" as it is commonly referred to - needs to be better integrated into long term energy planning and taken in to account when we weigh the true costs and benefits of traditional, fossil fuel-based thermal generation and renewable energy.
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