NSF's Weather or Not!
NSF-funded researchers forecast the impact of heat and drought on power generation in the western U.S. and explain why power plants need to become more resilient
National Science Foundation
Interviewer: Charlie Heck
Interviewees: Matthew Bartos and Mikhail Chester
Charlie: In the western US, heat, drought and wildfires often lead the news, but another topic well worth attention is the increasing strain on power plants. I’m Charlie Heck at the NSF, co-editor of the Science360 news service, co-host of the Super Science News Show and… science geek in training.
New research by the National Science Foundation shows power plants in the western US need to plan for a hotter, drier climate, and become resilient against power outages.
Matthew: There are a couple incidents in the last couple decades actually where power plants were forced to reduce generation capacity because either the water temperature was too hot or there wasn't enough water to maintain full generation capacity.
Mikhail: Under drought that occurs with a frequency of about once every ten years we could expect up to about an 8.8 percent loss of generation capacity.
Charlie: NSF-funded Matthew Bartos and Mikhail Chester, both at Arizona State University, co-authored a new paper on the subject. I spoke with them about their research and “climate proofing” the capacities of western US power plants.
First Chester explains how power plants are affected:
Mikhail: So as air temperatures change and a lot of climate forecasts show that air temperature is going to rise and as stream flow as well as stream flow temperatures change then power generation facilities, which take in air and take in water and then expel warmer air and warmer water at times, are going to have an efficiency loss. And we assess whether that efficiency loss was going to be significant. We assessed a number of climatological forecasts out to mid-century around the 2040 to 2060 time period. And we found that under average summertime conditions, which is when the electricity grid is working the hardest, we can expect about a one to three percent loss in generation capacity. And more seriously under drought that occurs with a frequency of about once every ten years we could expect up to about an 8.8 percent loss of generation capacity.
Charlie: Chester says these capacity losses are significant in terms of how we plan for our future electricity supply. And how extreme heat or drought affect a power plant depends on what kind of power plant it is…Here’s Matthew Bartos:
Matthew: For some of them it's fairly intuitive. Hydroelectric power plants require water to generate power because they patch flowing water through a turbine. And if there's less stream flow available, particularly for run of the river, hydroelectric power plants, then there's less power generation capacity at those generation stations.
Matthew: For other types of power plants, it's a little bit less intuitive. So for large space loads, nuclear and natural gas power plants, they require water for cooling. So if they don't have enough cooling water, they generally have to reduce generation capacity. So under climate change we may see elevated water temperatures and reduced stream flow, especially under extreme heat and drought scenarios. And this may cause these large base load power plants to reduce generation capacity.
Charlie: Bartos says this is something that has actually happened. That in the last couple decades, power plants were forced to reduce generation capacity because either the water temperature was too hot or there wasn't enough water to maintain full generation capacity.
Matthew: So in 2003 there was an incident where more than 30 European power plants had to reduce their generation capacity because the water was too hot to maintain temperature discharge limits. The same thing happened in 2007 in the Southeast United States. So those are some of the main reasons that power generation may be reduced under future scenarios. However, there are other generation technologies as well that can experience reduced capacity under higher air temperature. So, for instance, combustion turbines, which are used for peaking power generation. So they produce power when electricity load is at its highest. They can suffer capacity reductions under high air temperatures because as air temperatures get higher the air gets less dense, which means there's less mass flow rate through these types of turbines.
Charlie: And renewable energy, such as solar power or wind power? Bartos says they are also vulnerable
Matthew: Renewables also can potentially see capacity reduction due to higher air temperatures and other, you know, climatic changes. So, solar photovoltaic cells also experience some capacity reductions under higher air temperatures. And wind turbines are also affected by changes in air density and wind speed.
Charlie: The research team relied on two components for this study. First…they determined how a changing climate will affect things like air temperature…stream flow…stream temperature and other variables. Then, they applied those projections to the physical models of the power plants that the team had created. So, with the results of their study, Chester explains how power plants can “climate proof” their operations.
Mikhail: There's a few things they could do. So, one is we found that certain generation technologies are more climate-proof as we call it than others or less susceptible to changing climatological conditions. So we found that in general renewables, wind and solar, tend to be less vulnerable to changing climatological conditions compared to thermoelectric power plants, both steam turbine as well as combustion turbine. So those would be technologies like gas, natural gas, nuclear as well as coal. Those three tend to be very susceptible to changes in air temperature and stream temperature as well as stream flow. They could think about deploying larger shares of renewables to particularly vulnerable areas, for example, the Southwest of the United States where we found that there would be significant capacity losses. Another thing that they could do is that there are certain areas of the West where we didn't find a significant decrease in generating capacity. As a matter of fact, in certain areas like the Pacific Northwest we found an increase in potential generating capacity. For example, as a result of more frequent precipitation leading to more ability to generate hydroelectricity. So, that brings up an interesting question of whether or not there's-- whether or not it's possible to increase long distance transmission of electricity from places like the Pacific Northwest to the Southwest, from less vulnerable regions to more vulnerable regions.
Charlie: In this study, the team specifically looked at the western US. But Bartos says the same methods could be applied to study the East.
Matthew: We just wanted to look at the Western United States because...because the West is becoming significantly dryer as a result of climate change, at least the Southwest. Some models predict that the Pacific Northwest may receive more precipitation. But in general climate impacts on the West are expected to be relatively severe. But the Eastern United States is kind of a different story. Their generation portfolio is a little bit older. So they rely on more large base load full power plants. And they also use older types of cooling systems. So they mostly use open loop cooling for their large base load power plants, which basically just takes water in from the stream and then dumps it back out into the stream. So those ones are actually more susceptible to changes in stream temperature than most of the portfolio in the West because we use a lot of recirculating cooling. So, I would expect that the Eastern United States may receive even greater capacity reductions than the West.
Charlie: And because you want to know and I REALLY wannna know, I asked Bartos to share his wow, really moment in the study!
Matthew: I guess one of the things that stuck out to me was--is the spatial differences in how different--how different regions are going to be affected. So, in particular, in Southwest California they're expected to see the greatest reductions in capacity by quite a wide margin compared to the Pacific Northwest, which relies on a lot of hydro power, and they actually see more precipitation. So, yeah, impacts of power generation aren't equal across all the West. There's quite a bit of disparity between different regions with some of the Southwestern regions seeing average impacts of up to 5 percent by mid-century.
Charlie: So what’s next? Chester says what they’re thinking about now are the potential impacts on transmission and distribution:
Mikhail: We started by looking at supply, how the generation of electricity might be impacted. Now we're moving into the transmission of electricity. As we move electricity lines get hot. And if they get too hot, then there's significant efficiency losses. So we're assessing how power lines across the West might be impacted by warmer temperatures. And then the third piece that we need to understand is the demand side. How might electricity demand change? So things get hotter in the West, people might run their air conditioning more frequently, which may result in more demand for electricity. So, you know, the combination of supply, transmission and demand are the sort of three pieces of the puzzle that we need to rigorously understand to make sure that we are developing strategies such that we have reliable electricity out to mid-century.
Charlie: That was Mikhail Chester, an assistant professor and Matthew Bartos, a research scientist, both at Arizona State University.
Both are authors of the paper “Impacts of climate change on electric power supply in the Western United States,” published in the journal Nature Climate Change.
I’m Charlie Heck, co-editor of Science360’s news service and co-host of the Super Science News Show, at the National Science Foundation. If you have any questions about this story or suggestions for interviews about super cool NSF-funded science, I’m standing by right now, waiting for your email. Okay, not really, but email me your ideas anyway: editor@Science360.gov.