This episode, we’re looking at how clean energy is stored. How is it that we can use electricity generated from solar farms at night, or from wind farms when the wind isn’t blowing? And how has that technology been improving in recent years? We spoke to Paul Denholm from the National Renewable Energy Laboratory to find out.
Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
Today, we’re taking a look at how renewable energy, like wind or solar, is stored so it can be used when the sun’s not shining or the wind isn’t blowing.
We had Brendan Gardner and Ashley Junger from our Possibly Team look into this. Welcome, Brendan and Ashley!
Brendan Gardner: Hi, Megan!
Ashley Junger: Hello!
Megan Hall: So, why do we need to store wind and solar energy?
Ashley Junger: Well, right now, we power most of our cities with fossil fuels like coal or natural gas. Those power sources create greenhouse gas emissions, but they do have one advantage.
Megan Hall: What’s that?
Ashley Junger: They can create exactly the amount of electricity we need whenever we need it.
Brendan Gardner: One of the big obstacles with renewable energy, like wind and solar power, is that we can’t make the wind blow harder or the sun shine more if we need more electricity.
Megan Hall: And that’s why we need to find a way to store it?
Ashley Junger: Exactly. But storing that energy can be a challenge.
Brendan Gardner: To learn more, we spoke to Paul Denholm from the National Renewable Energy Laboratory.
Paul Denholm: On the grid, the basic idea of energy storage is to store excess electricity in times where it’s not really needed, and use that electricity at a later time.
Megan Hall: So how does this actually work?
Ashley Junger: Well, you can do it the old-school way….
Brendan Gardner: For the past 100 years, we’ve been storing energy by pumping water up a hill and then running it through turbines when we need more electricity.
Ashley Junger: This method is called pumped-storage hydropower and it’s still what we use for almost all of the stored energy in the US.
Brendan Gardner: Paul says that the United States has about 23 gigawatts in pumped-storage hydropower.
Paul Denholm: For context, one gigawatt is a big power plant, like a big nuclear power plant. You can power a pretty sizable city with that.
Brendan Gardner: 23 gigawatts is enough energy to power the city of Washington, DC for about ten days.
Megan Hall: So, a lot, but not enough to run the country?
Brendan Gardner: Yep. Pumped hydro is efficient, and effective, but it’s only viable where you have enough water, and the right topography. On the East Coast, for example, that’s a challenge.
Megan Hall: What about batteries?
Ashley Junger: Right now, the most common type of battery for energy storage is called the lithium-ion battery – they’re the same as in your cell phone or electric car.
Brendan Gardner: And if you strung a lot of these batteries together, you could store a lot of power. But the technology hasn’t really reached the proper scale yet–the largest lithium-ion battery in the world can only power about 300,000 homes for a short period of time.
Ashley Junger: And grid scale lithium batteries are still a pretty big fire risk, though that’s improving.
Brendan Gardner: In the short term, batteries are likely to be used to provide a few hours of power.
Megan Hall: Why is that?
Ashley Junger: Well, we use our dirtiest energy sources, like gas-powered turbines, when we have a surge or a peak in electricity needs. And Paul says
Paul Denholm: Peak demand period is two to four hours long. And so if you build a four hour battery, you can nicely clip that peak discharge electricity.
Ashley Junger: That amount of storage helps keep some of the dirtiest fossil fuel power plants turned off, so it’s a big step.
Brendan Gardner: But what we really need is storage that can last all night, so we can make up for the missing solar energy when the sun isn’t shining.
Megan Hall: How close are we to all of this becoming a reality?
Brendan Gardner: We’re getting closer every day. The technology for these batteries keeps getting more efficient and cost-effective, and capacity is increasing rapidly.
Ashley Junger: But there is a long way to go before batteries can provide constant electricity while being charged only from intermittent sources like wind and solar.
Megan Hall: I figured. Thanks, Brendan and Ashley!
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Possibly is a co-production of the Institute at Brown for Environment and Society, Brown’s Climate Solutions Initiative, and the Public’s Radio.
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