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When the River Runs Hot · The Climate Translation

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  Music
• 0:07
  Imagine the hottest part of the summer when air conditioners are running non-stop and electricity demand is surging.
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  This is exactly when we need power plants working at full capacity.
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  But extreme heat can make those power plants harder to operate and the reason is water.
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  Today we're going to explore the hidden connection between electricity and water.
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  Why warmer rivers can become a problem for the power grid.
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  And what happens when infrastructure built for yesterday's climate has to operate in tomorrow's heat?
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  Welcome back to the podcast. I'm Dr. Mac and this is the Climate Translation.
• 0:54
  To understand why hot water can become a problem for a power plant, we first need to understand some basic physics.
• 1:04
  Generating electricity creates a lot of heat.
• 1:08
  Think about the engine in a car. A combustion engine operates by burning gasoline.
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  The energy that is released helps to drive the pistons, which turn the crank shaft, that powers the wheels and helps move the car down the road.
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  But not all of the energy released is used for motion. A great deal becomes waste heat. It's why your car needs a radiator.
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  Without some way to remove that excess heat, the engine would eventually overheat.
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  Many large power plants face a similar problem.
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  Coal plants burn carbon-rich fuel to reduce heat. Nuclear plants produce heat through nuclear fission.
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  Natural gas plants burn methane to generate heat.
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  But whatever the fuel source, some of that energy is released and can be used to boil water and produce high-pressure steam that spins a turbine.
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  The turbine turns a generator and the generator produces electricity. So far so good.
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  But after that steam passes through the turbine, we have a problem. It's hot.
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  And before the water can be used again, you need to cool that steam down and turn it back into a liquid.
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  This is where the cooling system comes in.
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  Many power plants are built near water bodies. The cool water from rivers and lakes, reservoirs, or even the ocean can be used to pass through equipment called a condenser.
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  Inside these machines, the steam from a power plant is separated from the cool water intake, but close enough so that the heat can be transferred from one to the other.
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  The steam cools. It condenses back into liquid water and then can be sent back through the plant to be used again.
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  But the important part here is that the heat didn't just magically disappear. The energy was just transferred, in this case to the water that was drawn from the water body.
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  So now the water is warmer than it started out, and somehow the power plant has to get rid of it.
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  Some plants use what's called once-through cooling. They draw large amounts of water from a river or a lake, allow that water to absorb the heat from the plant, and then return the water to the environment.
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  Other plants use cooling towers. You've probably seen them. They are the enormous towers that sometimes appear beside power stations with huge white clouds rising from the top.
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  The white cloud is mostly water vapor. In these systems, much of the cooling water is reused again and again, while some of the heat escapes through evaporation.
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  There are also plants that use air for cooling and require less water, but those systems come with their own trade-offs.
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  The important point here is that in all the examples, power plants are just moving heat around, and heat energy moves more efficiently when there's a large difference between something hot and something cool.
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  Cold river water can absorb heat relatively easy, but warmer river water has less room to do so.
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  It's a simple piece of physics, part of what we call thermodynamics, and it is what connects the temperature of a river to how efficiently a power plant can operate and ultimately, how much electricity it can produce.
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  And during a heat wave, that difference can begin to matter very quickly.
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  The bodies of water, such as the river, that power plants are sometimes built by, are part of a larger ecosystem. Fish and other aquatic organisms in these ecosystems have evolved to tolerate a certain range of temperatures.
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  If a power plant discharges warmer water back into a river, it can change the local environment, especially if the river is already unusually warm.
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  Warm water, for instance, holds less dissolved oxygen, and that can cause an additional stress to aquatic life. Think about a can of soda.
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  If you open it when it's warm, you'll note that the carbon dioxide inside fizzes out very fast, sometimes leading to the soda tasting flat.
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  A cold drink, by contrast, holds on to that dissolved carbon dioxide much better.
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  Gases generally become less soluble in liquids, as temperatures rise.
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  So power plants usually operate under environmental rules, limiting how much heat they can put in the water around them.
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  But this can create a squeeze. If a river is already warm to begin with, power plants may have their discharges limited, and thus their only option can be to reduce how much electricity they're producing.
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  We saw this problem play out across Europe during the summer of 2026.
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  In Switzerland, the Beznau nuclear plant sets along the Aare River, which supplies water used in the plant's cooling system.
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  During a June heat wave, the river reached about 25 degrees Celsius, or 77 degrees Fahrenheit.
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  At first, the plant's operator, Axpo, reduced the output of both reactors to about half their normal power.
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  Then, when the river remained too warm, both reactors had to be temporarily shut down.
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  And Switzerland was not alone. During the summer of 2026, high river temperatures forced several nuclear reactors in France to reduce their electrical output or temporarily shut down.
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  But it's not a problem unique to nuclear power plants.
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  It's a problem for any thermal power plant that relies heavily on nearby water to carry away waste heat.
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  The French company EDF was dealing with the same basic problem at multiple locations.
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  In southern France, even a natural gas power station at Martigues faced restrictions because the Mediterranean water used for cooling had become unusually warm.
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  So a situation develops. The hottest days are often when electricity demand is the highest, because millions of air conditions are running.
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  But those same hot days can warm rivers and lakes enough to make power plants less efficient or force them to reduce their output.
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  And warm water is only half the problem. Sometimes, there's simply not enough of it in the first place.
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  In August of 2026, Romania faced such an unusual problem that the government brought in military engineers and explosives. The problem was the Danube River.
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  A severe drought had pushed water levels so low that the Cernavodă nuclear power plant was struggling to get enough water into its cooling system.
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  So engineers tried to redirect more of the river toward the plant. They dredged channels. They positioned barges filled with rock.
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  And at one point, military engineers used explosives to remove rock formations along the old branch of the Danube, hoping to increase the amount of water reaching the plant.
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  It may sound extreme, but it illustrates something important about the relationship between electricity and water.
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  A power plant can't simply pull cooling water from a river no matter how low that river becomes.
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  The intake has to remain submerged. Pump's need enough water around them to operate properly.
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  And there has to be enough water moving to the river to receive whatever heat the plant eventually releases.
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  Think about drinking through a straw. As long as there's plenty of liquid in the glass, everything works fine.
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  But if you keep lowering the water level, eventually the bottom of the straw reaches the surface.
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  It doesn't matter how powerful you are at sucking through the straw. The water's not there.
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  And something similar can happen at a power plant. By the summer of 2026, the Danube was extremely low.
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  According to Europe's Copernicus Climate Service, nearly two-thirds of the river experienced July flows that were at their lowest in the last 34 years.
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  Cernavodă had already shut down one of its two reactors in late July. Despite the efforts to redirect more water towards the plant, the river continued falling.
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  On August 13th, operators began shutting down the second reactor as well.
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  For a time, Romania's only nuclear power plant stopped producing electricity. And that mattered because that plant normally provides about one-fifth of the country's electricity.
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  And Romania wasn't the only country dealing with this problem.
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  Father upstream of the same river, Hungary's Pax Nuclear Power Plant was also forced to reduce production as the Danube levels fell.
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  This is where drought creates a different problem from the one we discussed.
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  Warm water limits how much additional heat a river can safely absorb. Low water limits how much water is available in the first place.
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  And the two often occur together. Extended hot weather increases evaporation from soils, reservoirs, and vegetation.
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  If rainfall is also limited, rivers shrink. Meanwhile, electricity demand may remain high because people are trying to stay cool.
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  And there can be another complication. Drought can reduce hydroelectric generation at the same time thermal plants are struggling for cooling water.
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  So one change in the water cycle can affect several parts of the electrical system all at once.
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  It doesn't mean that every drought is going to cause power shortages. Power grids draw electricity from many different sources and operators try to plan for changing conditions.
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  But the events along the Danube show why the amount of water flowing past a power plant is not just an environmental issue.
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  It's also an energy issue. And as climate conditions change, engineers are having to think more carefully about a question that was once largely taken for granted.
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  When a power plant needs water, will the water still be there?
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  So what do we do about this?
• 11:58
  Power plants are going to continue producing waste heat. Rivers are going to continue getting warm during heat waves.
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  And in some parts of the world, drought will continue to limit how much water is available.
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  But that does not mean every power plant has to depend on a large river or lake or reservoir beside it.
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  There are other ways to design the system. One of the most interesting examples is sitting in the Arizona desert.
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  The Palo Verde generating station is the largest nuclear power plant in the United States.
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  And unlike most nuclear plants, it's not located beside a river, lake or ocean. There isn't one nearby.
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  Instead, Palo Verde uses treated waste water from surrounding communities, water that's already passed through homes and businesses and has been cleaned, treated at the power plant and then used in the cooling towers.
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  The plant recycles about 20 billion gallons of waste water every year.
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  It's a reminder that cooling water does not necessarily have to come from a river.
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  Another option is to use less water in the first place.
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  Remember those cooling towers we talked about earlier?
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  They allow power plants to reuse some of the same cooling water rather than constantly drawing enormous amounts from a river or lake.
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  That dramatically reduces how much water has to be withdrawn, but some of the water is lost through evaporation, so we solve one problem but create another.
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  There are also dry cooling systems. Instead of using water to carry away most of the waste heat, you can use air.
• 13:40
  Air passes over equipment carrying the heat away and moves the energy into the atmosphere.
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  That can reduce water use enormously, but of course there's a catch. Air cooling only works if the air itself is cool.
• 13:54
  On a 100 degree afternoon, getting rid of heat using 100 degree air is going to be pretty hard.
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  A dry cooled power plant can therefore lose some efficiency on hot days when electricity demand is at its highest.
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  Engineers can combine the two approaches though. Hybrid systems use air when conditions allow and water when additional cooling is needed.
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  That reduces water use without depending entirely on air during extreme heat.
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  And then there's another solution that does not involve changing the cooling system at all.
• 14:29
  You just change where the electricity comes from.
• 14:32
  Wind turbines and solar panels don't produce electricity by boiling water, so they don't need the enormous cooling systems used by traditional carbon-based thermal power plants or nuclear plants.
• 14:47
  That doesn't mean that they have no environmental impact or that they can replace every power plant by themselves,
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  but adding electricity sources that are not dependent on cooling water can make the larger grid less vulnerable when rivers become hot or too low.
• 15:05
  The same is true of energy storage and stronger connections between different parts of the electrical grid.
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  If one region loses generating capacity during a drought or heat wave, electricity could be available from somewhere else.
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  And that might be the larger lesson in all of this. For decades, power plants were designed using what engineers knew about the local climate.
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  How hot does the river get? How low does it normally fall? How much extreme heat does an area get?
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  But with man-made climate change, those historical conditions are changing.
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  A river that rarely reached a critical temperature in the past may cross the threshold more often in the future.
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  A drought considered unusual when the plant was designed may be less unusual now or in the future.
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  So adapting the electrical system to climate change is not simply about producing cleaner energy.
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  It's also about making sure that the infrastructure we already depend on can continue working in the climate it will actually experience.
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  Because sometimes keeping the lights on begins with something surprisingly basic, making sure there's enough cool water to carry the heat away.
• 16:29
  When extreme weather pushes electricity to its peak, warm rivers and historic droughts create a dangerous paradox.
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  The very days we need power are the days that thermal plants struggle the most.
• 16:42
  Whether the solution is recycling municipal waste water, upgrading to hybrid cooling or relying on water-free wind and solar, the reality is clear.
• 16:53
  We can no longer engineer a power grid for yesterday's climate. In a hotter world, energy security and water security are two sides of the same coin.
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  I'm Dr. Mac and this has been the Climate Translation.
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  If you have a question about the climate you've been too afraid to ask or if you have a differing opinion, I want to hear from you.
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  I can use your viewpoints in future episodes.
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  You can reach me at the climate translation at gmail.com.
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  I'll see you next time.