What’s it going to take to win American independence from dirty energy?

The Fourth of July seems like a good time to ask — especially as we celebrate the first Independence Day under an administration whose motto might as well be “Make America Suck Coal Again.” (Now watch, Trump will put that on a hat.)

But beyond that, it’s also a good time to ask because of a … let’s just call it a spirited debate that recently broke out between two groups of scientists who work on climate and energy. Both want to see the United States fight climate change, ditch polluting fossil fuels, and ramp up renewables. But there’s a bitter disagreement between them over how it can happen.

The whole thing started in 2015, when Stanford professor Mark Jacobson and some colleagues published a paper arguing that, by mid-century, the United States could be powered entirely by clean energy sources — and by clean, he meant the really clean stuff (wind, solar, hydropower), not the only-somewhat-cleaner-than-coal stuff like natural gas, nuclear energy, and biofuels.

As you can imagine, that got the kind of folks who get excited about clean energy pretty excited. (Bernie Sanders, Mark Ruffalo, big green groups, Grist vet David Roberts. And we were no exception — our editors put Jacobson on the inaugural Grist 50 list of game changers and planet savers.) Better still, Jacobson’s blueprint started to inform policy discussions, with serious people taking the idea of 100 percent renewables pretty seriously.

Still, it’s a long way to go in a relatively short period of time (add up wind, solar, and hydro, and it’s currently just 13 percent of the U.S. energy supply). Many experts sweated the details of the sunny picture that Jacobson and his colleagues presented.

Last month, they did it with the scientific equivalent of a switchblade. Twenty-plus researchers published a study in the Proceedings of the National Academy of Sciences arguing that Jacobson’s original paper (published in the same journal — ouch) “used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions.”

Those are fighting words for research-types, and Jacobson struck back, which elicited yet another reply. The whole thing probably looked pretty bad to outsiders. In fact, to anyone not enmeshed in the details, it probably looked like a fight over whether it’s even possible to convert the entire United States to clean energy and combat climate change.

Except it wasn’t. Regardless of whether Jacobson took some shortcuts on his road map, both sides agreed that the goal of weaning ourselves off fossil fuels and shutting off greenhouse gas emissions is possible. The question is: What’s the best route to follow?

So rather than continue to focus on an internecine squabble, we talked to six of the smartest energy experts around and asked them to program the GPS coordinates for America’s clean energy future. Here’s how they responded.

It’s too late to stop clean energy

Ramez Naam

Ramez Naam, former Microsoft computer scientist, technologist, and science fiction author

It’s true: Wind and solar are intermittent. So how do you deal with that? You really have three choices:

One, build so many wind turbines and solar panels that you can fulfill America’s energy need even when there’s barely any wind or sun. The problem with that is, it’s expensive. You have a lot of capacity you don’t need most of the time.

Two, you build storage for that wind and solar energy. But we don’t really have a viable technology for seasonal storage. [Editor’s note: Folks are working on it.]

Your third option is to keep something that’s not wind or solar running — some nuclear, or maybe some natural gas.

If we had to go off the economics and the technology we have today, we’d say it’s cheapest to take the third option. In the future, the declining cost of tech might change those economics, but overcoming climate change is too important to bet entirely on that.

Here’s my best guess of what the clean energy world of the future looks like: a lot of wind turbines in the Great Plains and Texas, and some offshore. A lot of solar in the West, the Southwest, and the South. Together, solar and wind are providing 70 percent or more of our electricity. Hydro is another 10 percent or more. And we’ve built a lot of long-range transmission.

People think that wind and solar mean getting off-grid or less dependent on the grid, but the opposite is true. You need more grid investment and more movement of energy from the sunniest and windiest places (where it’s cheapest and most reliable to produce) to the places the energy is consumed.

Possibly, in the future, we’ve solved the long-duration storage problem. More likely, there are still nuclear plants running, and there may even be some natural gas plants lingering in the system — not running at full capacity, but they have the ability to power up quickly when there’s not a lot of sun or wind. Along the way, we’ve electrified most of the things that currently run on fossil fuels.

Many people are concerned Trump is dooming us. I don’t think so. We’ve missed the window where policy makers could really stop clean energy. The biggest drivers of clean energy in the United States right now are economics and the states. The congressional districts that produce the most clean energy in the country are almost all Republican. Climate change is hugely polarizing, while clean energy is bipartisan and loved across the board.

The question is no longer if we’ll get to a mostly clean grid, it’s a question of when.

The shiny future

Krishna Kolluri

Varun Sivaram, acting director of the Council on Foreign Relations energy security and climate change program (and member of this year’s Grist 50)

In the United States, wind and solar power just cracked the 10 percent threshold for energy use. (And we are at far more than 10 percent clean energy use, thanks to nuclear and hydro.) But fossil fuels still account for the majority of both electricity use and primary energy use overall, and at no time in the near future will that change.

So we’re not aiming for 100 percent renewable. We’re aiming for near-zero greenhouse gas emissions, or “deep decarbonization.” The target we tend to look at is an 80 to 100 percent reduction in electricity sector emissions by 2050. That’s a goal that we can get our heads around. The strategy looks something like: Make electricity nearly zero-carbon, and then electrify as many end uses as possible. Make transportation run off electricity, make industry run off electricity, and voila, you’re going to get to deep decarbonization of the whole economy.

It’s not feasible with today’s technologies. It could be feasible if we invest in innovation. That can be technological innovation: better nuclear reactors, better forms of energy storage, better solar panels. We could reimagine the way the power grid works. Instead of today’s AC power grid, we could have a bunch of networked DC microgrids that are super efficient. We could have a massive supergrid. We could have both!

You can imagine a world in which you have very cheap solar coatings. These coatings convert sunlight into electricity just like today’s panels, but these are so dirt cheap and flexible and colorful you can do anything with them. You can paint skyscraper windows with them, you can paint your house with them — but they still only generate power when the sun is shining. So, you also have super-efficient concentrated solar plants that take the sun’s rays, convert them by heating up something like a molten salt, and store that heat so you can generate electricity 24/7. You put them together, and you have very reliable power.

On top of this, you also want fuels for your planes, ships, cars, and trucks. So you have technologies that will look something like a tarp that you unroll over a football field. It soaks up the sunlight and spits out hydrogen, and you use that hydrogen fuel for cars, ships.

That’s a vision of the world where new technologies allow us to basically power all of our uses with sunlight.

Costs matter

UC Berkeley

Meredith Fowlie, University of California energy and environmental economist

There are different paths to meeting greenhouse gas emissions reduction targets, and some will cost a lot more than others. The long-run political viability of decarbonization depends on finding lower-cost paths.

The marginal cost of supplying electricity changes all the time. Every now and then, when demand is really high, it spikes.


Fowlie et al.

Traditionally, we’ve built gas plants to meet demand in these peak hours. Instead, we could be providing incentives to trim these peaks! For most electricity consumers — say, the person who wants to inefficiently run his air conditioner with the windows open — the price doesn’t change hour-to-hour, not even at the moment at which that extra electricity requires a whole new plant to come online. That makes economists sad.

It’s kind of crazy if you think about it: There’s no information sent to consumers about when it’s expensive to supply more electricity and when it’s not.

Think about a world with a lot of renewables, where the sun is rising and setting, and the wind is gusting and ebbing. You need to match this variable supply with demand. You can do this with more investment in flexible gas plants or batteries that bank supply and move it to meet demand. But there’s another important lever we should be using. If you just charge people a lower price when there’s a lot of wind and sun (when the supply of electricity is abundant and cheap) and a higher price at times when there’s not, they’ll reduce consumption when electricity is scarce.

In an experiment, we tried sending people a price signal, where they were paying more in those peaks, and we saw a significant response: People use less electricity when the price is high.

This may seem like it’s in the weeds, but it’s important. We can’t achieve our goals if we ignore cost.

All of the above

Fatima Ahmad

Fatima Maria Ahmad, fellow at the Center for Climate and Energy Solutions, former Interior Department staffer

After President Trump pulled us out of the Paris Agreement, I thought it was an encouraging sign that so many mayors and governors and university presidents committed to reducing carbon emissions – the “We Are Still In” campaign.

It’s hard to put an exact time on it, but I do think we can still hit the Paris Agreement’s target of net zero emissions by the second half of this century. It is achievable. But fossil fuels will still serve as a source of energy demand, and so the only way to achieve our goal is through carbon-capture technology.

We want to achieve deep decarbonization as quickly and as cheaply as possible. And I think that carbon capture is the cost-effective way to do it.

Politically it makes a lot of sense, too. There’s a lot of disagreement between Republicans and Democrats about energy, but with CCS you get bipartisan support. What else gets coal companies, some environmental groups, and labor unions in support of it? If there’s a bipartisan agreement on something that can help us, we should seize it.

I’m definitely a proponent of the “all of the above” strategy. I don’t know if there’s one silver bullet. You need multiple sources of energy — wind, solar, natural gas. Maintaining our nuclear energy is important to hit our clean-energy goals.

It’s also going to require stable policy from federal and state governments and corporate leadership with research and development. I think we need a lot of private-public partnerships, like Petra Nova in Texas, where NRG Energy and other companies retrofitted a coal-fired power plant with carbon capture technology. It’s the largest carbon capture project in the world. It received investments from U.S. and Japanese companies — the technology was created by Mitsubishi — and also the Recovery Act.

There are federal financing policies that could help fund renewable energy and carbon capture. We need to double our R&D spending. And obviously, a price on carbon would help us get corporations to focus on this.

A lot of states have renewable portfolio standards. Some states, a few, have clean-energy standards, sometimes called alternative-energy standards. They’re broader than wind and solar and can include nuclear and carbon capture storage. Massachusetts has one that includes capture. Utah and Michigan have similar standards. If states could expand this, it would do a lot to drive investment.

Let’s do the math

Saul Griffith

Saul Griffith, inventor and MacArthur Fellow (but don’t call him a genius — he gets angry)

If we’re going to eliminate greenhouse gas emissions, the two biggest opportunities are transportation and electricity. These complement each other: If we fully electrify transportation and run it off renewables or nuclear, you’d reduce the energy transportation consumed by two thirds.

So, what would we have to pay for it? America uses about 3.5 terawatts of energy. If we electrified transportation and everything else, we’d only need 2 terawatts. The cost of solar is about $1 per watt when you have the most sun, and about five times as much if you want power all day long. So switching over to 24-hour renewables is $10 trillion. Add in electric cars and let’s call it $15 trillion.

That’s a lot of money, but we’ve made that kind of investment before. There’s 8.6 million lane-miles of road in America, and it costs us upwards of $1.5 million to build a lane. If you do the math, the current value of the U.S. road system is $13 trillion, an investment made over the last century. And if we got the incentives right, the private sector would pay for 90 percent, which brings public costs down to $1 trillion.

If we cared, we could do this in a decade. To be more practical, think about the replacement rate of the components of our system. The turnover in the U.S. car fleet is about 10 years, so if everyone bought an electric car the next time they bought a car, you’d have 95 percent electric cars in 10 years. If half of people buy an electric car, you have 87 percent electric cars in 30 years. And if we waited until the end of each power plant’s lifespan to replace it with clean energy, we could be done in 25 to 50 years.

We lock ourselves into bad carbon behavior every time we replace one retiring piece of infrastructure with another that runs on fossil fuels. What we really need to do is focus on the big purchases — like cars and power plants — and provide the information and financing to help people make better choices.

Policy comes first

UC Berkeley

Andrew Campbell, former ExxonMobil engineer, Energy Institute at Haas executive director

I don’t view fossil-fuel independence per se as a goal. Reducing greenhouse gas emissions is the goal. And to get there, we’d need to put in place underlying policy mechanisms. Pricing carbon dioxide would be a big one, and coupling that with aggressively funding research and development in many different areas.

I’m most enthusiastic about policy approaches that are either technology neutral or pursue lots of options. It could be that carbon capture and sequestration is going to be a very important piece of this. It could be nuclear power. It very well could be solar and wind, combined with storage.

Getting to an emission-free future will require a real commitment to research and development, technology development, and support for technologies as they enter the market — like ARPA-E, but at an even larger scale. I could imagine maybe 12 different technologies supported through that process, and it turns out two or three will end up having a big impact.

The Paris accord is hugely encouraging, even though the United States pulled out. It’s the first international agreement where almost all countries agree that climate change is an issue that needs to be addressed. There’s also been sustained success of some of the cap-and-trade markets in Europe and North America. I understand that China is moving forward with cap-and-trade markets. That’s been a very encouraging development that seems to be spreading outside of the United States.

I’m most pessimistic about the transportation sector. It’s much more consumer driven — people and businesses making choices about where they live, where they work, the characteristics of the transportation they want to use.

Cities like to keep things as they are and aren’t really promoting the sort of business and residential development necessary to reduce people’s travel. On the vehicle side, politicians are very afraid of gasoline taxes — a key ingredient to begin to transition the sector.

I don’t know if being emission free by 2050 is possible, and certainly we’re taking significant steps back domestically in terms of no longer pursuing regulations — not making CAFE standards more aggressive and not moving forward with the Clean Power Plan. One thing to keep in mind, though, is that the current four-year presidential term is just a blip in the next 35 years.

Reporting by Nathanael Johnson, Matthew Craft, Nikhil Swaminathan, and Amelia Urry