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A podcast by GBH News reporter Ian Coss gives this notorious project a long-overdue reappraisal. Bonus: The show comes with lessons for climate infrastructure projects of the future.

If you’ve lived in Massachusetts at any point in the last 50 years, you’ve heard of the Big Dig. It’s infamous — a tunnel project that was supposed to bury an elevated highway in Boston to the tune of $2 billion that eventually ballooned in cost to $15 billion and took a quarter of a century to finish.
The Big Dig was more than just a highway project, though. It was a monumental effort that Ian Coss, a reporter at GBH News, calls a “renovation of downtown Boston.” The project built tunnels and bridges, yes, but it also created parks, public spaces, and mass transit options that transformed the city. In a nine-episode podcast series appropriately called The Big Dig, Coss dives into the long, complicated history of the project, making a case for why the Big Dig was so much more than the boondoggle people think it was.
I talked to Coss about how the Big Dig came to be and the lessons we can learn from it as we continue to adapt our built environment to a changing climate. Our interview has been edited for length and clarity.
I moved to Boston for college in 2010, and I remember going to the North End and being struck by how beautiful it was. I didn’t realize how recently that view had changed until I listened to your podcast — I mean, the Big Dig had only wrapped up a few years earlier.
It’s easy to forget how quickly it transformed. I grew up in Massachusetts, so when I would come into the city I would see [the Big Dig] being built — I have vague memories of the elevated artery. And when I moved to Boston Proper in 2013, which was less than a decade after the project wrapped, it was stunning for me to be like, “oh, this is what that project was,” because I definitely didn’t understand it at the time.
What made you decide to create an entire podcast about this “renovation” of Boston?
I think part of it was this disconnect where I grew up hearing about the Big Dig and mostly hearing bad things about it — it was behind schedule, it was a disaster, a boondoggle, etc. — because that really was the reputation of the project, nationally and locally. And then moving to the city and seeing the fruits of it, it was hard to reconcile those things. Like, this “disaster” created a greenway through the middle of the city. Now you can actually get to the airport.
What was driving that narrative of its being a disaster?
The Big Dig went on a very long emotional journey. It started as this kind of visionary, idealistic project championed by activists and supported by politicians of both parties. And then, after navigating the process of funding, permitting, contracting, managing, and designing, by the time it's in construction, it really is not a source of pride.
There are a number of technical things about the Big Dig that could have been done better, and we can learn lessons from it. The way it was contracted could have been done better. The management structure could have been done better. There were flaws in the design, including a fatal flaw that cost the life of a driver in the tunnel.
I think a lot of it is about the storytelling. Just to give one example, so much of the negative narrative around the Big Dig was around the cost. You often hear about how it started with an estimated cost of $2 billion and wound up costing $15 billion. But I think that narrative misses a few things.
One is that it was never going to cost $2 billion. That was not a realistic estimate. But in our country, it is so hard to get approval, political support, funding, and permitting in place that there is a very strong incentive all throughout the process to downplay the costs, downplay the risks, downplay the disruption, make it sound like this is going to be quick and easy and painless and cheap, just to get to the starting line. Because the paradox of it is that if we had known in 1983 or 1987 or 1991 that this was going to be a $15 billion project, it would have never happened. And yet, in hindsight, there are many smart people who told me that this project was a bargain at $15 billion because of what we got in terms of economic benefits, transportation improvements, and environmental improvements.
There’s almost an element of asking for forgiveness rather than permission here, but that forgiveness is inevitably laced with anger because of those expectations.
Right. If only it were just forgiveness.
The Big Dig had its roots in the National Highway Program. Were all those projects going constantly over budget?
There’s a great paper that I cite in episode four where the authors studied the cost of highway building per mile every year from the 1970s through the 1990s, and it’s actually a great sample set because we’ve built so many highways of different sizes in different states. Basically, what they found is that highway costs per mile really ramp up significantly in the 1970s. And that’s, of course, the period when the [Big Dig] was first getting conceived.
So the short answer to your question is, it was cheaper once. But there were other costs, in that those early highways in the ‘50s and ‘60s largely did not consider the impact on communities or on the environment. They did not make a lot of mitigation efforts to minimize the day to day disruption caused by those projects. So I think part of what the Big Dig captures is this really historic change in the way we build things in this country that was ushered in by the anti-highway movements, by citizen activism, and by the National Environmental Policy Act. Over the course of the 1970s we made it much harder to build things, for very good reasons.
I think the Big Dig — which some people describe as the last great project of the interstate era — captures an attempt to do a massive, ambitious infrastructure project that is also loaded with environmental mitigation and also has a robust community process. Part of what we learned through that is that you can have a project that’s cheap and efficient, you can have a project that’s democratic and humane, but it’s tough to have it all. And the Big Dig was trying to have it all, and we did get it all, but at enormous cost. That was the thing that could never be solved.
You make a connection between the Big Dig and climate change right from the first episode. What are the climate lessons we can learn from the Big Dig?
In some ways, it’s ironic to hold up the Big Dig as a case study for climate change because it’s a highway project. My point is not that the Big Dig is, like, the future of infrastructure. But what it offers is a recent case study on a massively ambitious building project. We have some distance, and you can see the whole arc of it, but it very much lives within our era. It’s not the Hoover Dam or the Golden Gate Bridge or any of those other big projects built in a different time under different conditions.
The way I see it is that in order to mitigate or prevent the worst effects of climate change — and you can feel free to disagree with me — we’re going to need to build a lot of stuff. This is not a problem that we’re going to solve by riding bicycles and growing vegetables in the backyard, both of which I do and hope everyone does. And of course, those projects might look different than the Big Dig because building a wind turbine isn’t exactly analogous to building a downtown tunnel. But I think there are relevant analogies, especially things like coastal mitigation in cities, improving mass transit, building high energy transmission lines — these large scale projects that will affect people but also are an important public good.
You talked on the show about the Big Dig as an attempt to make this process more democratic at some level. People on both sides had very strong feelings about it. This reminded me of the NIMBY/YIMBY dichotomy of climate projects. Did anyone mention any best practices that could be applied to future projects of this kind?
I’ve talked with Fred Salvucci [former Massachusetts Secretary of Transportation and driving force of the Big Dig] about this. He mentioned this biblical parable — he’s full of parables — about Jesus walking across the water and then turning to his disciples and telling them to follow. But they step into the water and fall right in, and when they get back out they say it’s impossible. And then Jesus says, “It’s easy to walk across the water. You just have to know where the stones are.”
And Fred said the lesson there is that, in order to navigate this kind of process, you have to know where the flashpoints are, what the issues will be. That way you can anticipate them rather than just going in and saying “this is my project, I’m going to do it this way and you can fight me on it.”
Part of what I think is really interesting about this, which I think speaks to present-day projects like offshore wind, is that in that fight, you have very well-intentioned actors who are trying to make the project better and using the environmental process to do that. And you also have bad actors who are weaponizing and manipulating the environmental process to their own personal ends. And those two things get all mixed up.
You know, I’m an environmentalist. I believe in environmental review. I don’t want to sit here and say that we need to get rid of all environmental permitting because it makes it too hard to build things. But I think it’s also important to recognize that these things can be weaponized.
Scheme Z, which proposed this big spiral loop of ramps and a bridge over the river, is a good example. Politically, that became very messy — they were trying to impose concentrated harm in the name of a public good. And I know, strategically, maybe there are things [Salvucci] could have done to mitigate that or circumvent that, but given the structures in place, the logical outcome is that it spends a decade in lawsuits and review committees and you wind up with something that’s okay, that everyone can live with.
The funny thing about that is that it turned into the Zakim Bridge, which is now a Boston icon.
Right. I mean, that’s part of the communication piece, too.
I was biking under the Zakim bridge the other day, and I biked through where there’s a nice pedestrian and bicycle bridge and this skate park that is always filled with people. Truly, that is maybe the best utilized public space created by the Big Dig.
It’s easy for me to play Monday morning quarterback and say “oh, you should have communicated that better, you should have told the story better.” I mean, he was saying all the right things. But then all you had to say on the other side was “it’s 18 lanes and five ramps,” and that sounded terrible and looked terrible on the page. And I mean, sure, I wish there weren’t all those ramps there, but like you said, ironically, the bridge became an icon of the city.
I think a big part of the lesson for me is how hard it is to build infrastructure democratically because the timescales are all wrong. These things have short-term costs and cause short-term disruption and bring very long-term benefits.
I was constantly struck by this issue of scale, both in terms of time and money. It’s hard to wrap your head around the idea of billions of dollars and projects that span decades. These are just things that are impossible for any regular person to really plan out.
I was talking to someone who said that their dad was in his 70s when the Big Dig was just getting started. And for him, it was like, “my city’s going to be torn up for the rest of my life,” right? That’s what this project meant for him — he would live with this mess of a project and never see the results. And he had to deal with that so that you could move to Boston in 2010 and never know the city another way. The cost of that benefit is borne by another generation.
And it’s the same thing with climate change. It moves on a scale that is so much longer than politics. The Big Dig took almost 40 years from conception to completion. So if you’re thinking about political capital, if you’re thinking about two- and four-year election cycles, it’s very, very hard to conceive, plan, and deliver a project on that kind of time scale.
The benefits and costs are almost inverted in climate change, in a way. We’re talking about future benefits, yes, but we’re also talking about future costs if we don’t do anything. But it’s so hard to make people think in a 40- or 50-year timescale.
If the Big Dig was so hard to make happen politically with what I think was a more genial political environment overall, it feels kind of impossible to think of building anything on that scale right now.
I gave a talk at City Hall a few weeks ago and I was talking with some of the young planners there, people who are in their 30s. Some of them have been listening to the series, and they told me they could not imagine what it would be like to get that kind of federal funding out of Washington, get all the local players on board, get it through the permitting process, and get it contracted. Because right now if they try to take away one parking spot and put in one bike line, they’re bogged down in meetings for a year.
I think climate change is also the inverse of projects like this because with the Big Dig, for example, you can feel the tangible benefits of a quicker commute and a more beautiful city. But with climate change, if the projects work, you’d actually feel nothing.
Exactly. Climate change is way, way harder. A road project or a rail project will have benefits. You get ribbon cuttings and photo ops. But if we make Boston resilient to flooding or something, you know, do some big project that would improve the shoreline or whatever ideally, that historic storm surge may never come, or it’ll come and we’ll be prepared for it and nothing will happen. But yeah, you’re working with long term counterfactuals.
It feels to me like climate change was designed in a laboratory to flummox institutions. It takes all of our cognitive biases, our ingrained social and biological blind spots and weak points and just flicks them all at us at once.
All nine episodes of The Big Dig are out now. You can listen on the WGBH website, Apple Podcasts, Spotify, or wherever you get your podcasts.
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Current conditions: The snow squalls and cold air headed from the Ohio Valley to the Northeast are coming with winds of up to 55 miles per hour • A “western disturbance,” an extratropical storm that originates in the Mediterranean and travels eastward, is set to arrive in India and bring heavy snow to the Himalayas • Tropical Storm Basyang made landfall over the Philippines this morning, forcing Cebu City to cancel all in-person classes for public school students.
Vice President JD Vance delivered a 40-minute speech Wednesday appealing to 54 countries and the European Union to join a trading alliance led by the United States to establish a supply of critical minerals that could meaningfully rival China. The agreement would create a “preferential trade zone” meant to be “protected from disruptions through enforceable price floors.” The effort comes in response to years of export controls from Beijing that have sent the prices of key minerals over which China has near monopolies skyrocketing. “This morning, the Trump administration is proposing a concrete mechanism to return the global critical minerals market to a healthier, more competitive state,” Vance said at the State Department’s inaugural Critical Minerals Ministerial in Washington.
Under the Biden administration, the U.S. attempted to coordinate a network of trading partners, to make up for the minerals American mines no longer produced. The Treasury Department allowed automakers that sourced battery minerals to countries with which the U.S. had a free trade agreement to benefit from the most valuable version of the landmark electric vehicle tax credit reserved for power packs made with domestically-sourced metals. The White House worked with Republicans in Congress to eliminate the tax credit last year, demonstrating what Heatmap’s Matthew Zeitlin referred to as the “paradox” of Trump’s push for more domestic mining: A push to increase supply while eliminating one of the biggest sources of demand. The on-again, off-again tariff wars with allies haven’t done much to rally the spirit of camaraderie among America’s traditional trade partners either. Since then, as I have covered repeatedly in this newsletter, Trump has gone on a shopping spree for equity stakes in mining companies, shelled out grants through the military to mineral startups, and, most recently, created a $12 billion federal stockpile. Yet it’s come with plenty of missteps, as a former Department of Energy official told our colleague Robinson Meyer in his latest Shift Key podcast. Still, Congress is backing up the mining push. The House voted 224-195 Wednesday to approve legislation meant to speed up mining on federal lands.
Despite President Donald Trump’s threats to eliminate its funding, Congress has spared the long-running federal program that helps low-income Americans pay for heating and electric bills. The budget deal the president signed Tuesday to fund most federal agencies through September added $20 million to the Low Income Energy Assistance Program, bringing the total funding to just over $4 billion. It’s a full reversal of Trump’s position in May, when the administration asked Congress to completely eliminate the funding, Utility Dive reported. A second appropriations package Trump signed last month also included a small increase in funding for a separate program that subsidizes weatherization projects and other energy efficiency renovations for low- and moderate-income households.

Last week, I told you about copper prices soaring to a record — and seemingly unsustainable — high. While Goldman Sachs analysts expected the price for the metal needed for virtually anything electric to fall, it was still forecast to level off well above the average for the past few years. Well, that’s good news José Antonio Kast, the far-right leader scheduled to be inaugurated president of Chile next month. His incoming finance minister told the Financial Times the government plans to deliver economic growth rates of 4% and balance the country’s budget by 2029. If that proves possible, it’s only because Chile is the world’s largest producer of the red metal.
The U.S., meanwhile, is seeing early fruits of its global mineral diplomacy. The federal government’s International Development Finance Corporation said Wednesday that a U.S.-backed venture will begin shipping 50,000 tons of copper from the Democratic Republic of the Congo to Saudi Arabia and the United Arab Emirates. The export package comes a month after the same Congolese project pledged to send 100,000 tons to the U.S. The lending agency’s chief executive, Ben Black, said the partnership between Washington and Kinshasa “ensures valuable critical minerals are directed to the U.S. and our allies.”
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Newcleo, the best-known European nuclear startup promising to build fourth-generation small modular reactors, just netted $85 million in its latest financing round, bringing its total fundraising for the past 12 months to more than $125 million. The financing round includes venture funds Kairos and Indaco Ventures, asset manager Azimut Investments, the CERN pension fund, and industrial giants such as steelmaker Danieli, concrete manufacturer Cementir Holding, and components producers such as Walter Tosto and Orion Valves. The money will “accelerate our expansion into the U.S.,” a nascent effort that has included brokering a partnership with fellow next-generation reactor startup Oklo. Unlike the California company, whose microreactor design uses liquid sodium instead of water as a coolant, Paris-based Newcleo has proposed building a lead-cooled unit. The design has already gained approval in the United Kingdom. “Our ability to deliver impactful low-carbon energy solutions for energy-intensive firms is proving an attractive investment rationale for both industrial and financial investors,” said Newcleo CEO Stefano Buono.
Last week, I told you about the trouble brewing for the controversial wood-pellet giant Drax, which built its business on government subsidies predicated on the idea that burning felled trees for electricity could somehow provide a low-carbon alternative to fossil fuels. Facing overdue scrutiny of its green credentials, the British company had hoped Japan, the world’s No. 2 importer of wood pellets, would provide a growth market. But Tokyo indicated it’s cutting off the subsidy spigot. Then, two days ago, I told you that a former Drax employee admitted the company misled the public when claiming it wasn’t felling old-growth trees to make its wood pellets. Now the union that represents its British workers, Unite, has blasted Drax for the “shameful betrayal” of threatening to cut as many as 350 jobs. That could total up to 10% of the workforce. “It is shameful that a firm making billions such as Drax is choosing to target its staff,” Sharon Graham, Unite’s general secretary, said, according to Energy Voice. “It is morally wrong that workers, their families, and local communities pay the price for corporate greed.”
Over at The Washington Post, billionaire owner Jeff Bezos’ management team just gutted the newspaper's Pulitzer Prize-winning climate desk. The paper sent layoff notices to at least 14 climate journalists, newsroom sources told veteran beat reporter Sammy Roth for his Climate-Colored Goggles newsletter. The pink slips included eight writers and reporters, an editor, and several video, data, and graphics journalists. I’ll echo Sammy’s sentiment with the highest compliment I can give: I was routinely jealous of the top-notch reporting the climate team published at the Post. Losing that nuanced, complex reporting, at this particular juncture in the history of our nation and our atmosphere, is devastating. It’s also infuriating when you read the back-of-the-napkin math New York Times reporter Peter Baker posted on X yesterday: “Last reported annual losses of Post: $100 million,” he wrote. “Number of years Bezos could absorb those losses with what he makes in a single week: 5.”
Take a guess who wrote this on X yesterday morning: “Solar energy is the energy of the future. Giant fusion reactor up there in the sky — we must rapidly expand solar to compete with China.” Go ahead, I’ll wait. Whomever you were going to name, you’re probably wrong. The answer, astonishingly, is Katie Miller, the right-wing influencer wife of top Trump adviser Stephen Miller. A regular feature of White House social media content, Katie Miller posted her praise for an industry her husband’s boss has done much to stymie in response to an Axios article on a poll that found strong support for solar among GOP voters. The survey, commissioned by the panel manufacturer First Solar, comes as the solar industry says that the administration is throttling its permitting. While Trump seems unlikely to let up on wind, it could be a sign of a brighter future for America’s fastest-growing source of electricity.
Microreactor maker Antares Nuclear just struck a deal with BWX Technologies to produce TRISO.
Long before the infamous trio of accidents at Three Mile Island, Chernobyl, and Fukushima, nuclear scientists started working on a new type of fuel that would make a meltdown nearly impossible. The result was “tri-structural isotropic” fuel, better known as TRISO.
The fuel encased enriched uranium kernels in three layers of ceramic coating designed to absorb the super hot, highly radioactive waste byproducts that form during the atom-splitting process. In theory, these poppyseed-sized pellets could have negated the need for the giant concrete containment vessels that cordon off reactors from the outside world. But TRISO was expensive to produce, and by the 1960s, the cheaper low-enriched uranium had proved reliable enough to become the industry standard around the globe.
TRISO had another upside, however. The cladding protected the nuclear material from reaching temperatures high enough that could risk a meltdown. That meant reactors using them could safely operate at hotter temperatures. When the United States opened its first commercial high-temperature gas-cooled reactor in 1979, barely three months after Three Mile Island, the Fort St. Vrain Generating Station in Colorado ran on TRISO. It was a short-lived experiment. After a decade, the high cost of the fuel and the technical challenges of operating the lone commercial atomic station in the U.S. that didn’t use water as a coolant forced Fort St. Vrain to close. TRISO joined the long list of nuclear technologies that worked, but didn’t pencil out on paper.
Now it’s poised for a comeback. X-energy, the nuclear startup backed by Amazon that plans to cool its 80-megawatt microreactors with helium, is building out a production line to produce its own TRISO fuel in hopes of generating both electricity for data centers and heat as hot as 1,400 degrees Fahrenheit for Dow Chemical’s petrochemical facilities. Kairos Power, the Google-backed rival with the country’s only deal to sell power from a fourth-generation nuclear technology — reactors designed to use coolants other than water — to a utility, is procuring TRISO for its molten fluoride salt-cooled microreactors, which are expected to generate 75 megawatts of electricity and reach temperatures above 1,200 degrees.
Then there’s Antares Nuclear. The California-based startup is designing 1-megawatt reactors cooled through sodium pipes that conduct heat away from the atom-splitting core. On Thursday, the company is set to announce a deal with the U.S. government-backed nuclear fuel enricher BWX Technologies to establish a new production line for TRISO to fuel Antares reactors, Heatmap has learned exclusively.
Unlike X-energy or Kairos, Antares isn’t looking to sell electricity to utilities and server farms. Instead, the customers the company has in mind are the types for whom the price of fuel is secondary to how well it functions under extraordinary conditions.
“We’re putting nuclear power in space,” Jordan Bramble, Antares’ chief executive, told me from his office outside Los Angeles.
Just last month, NASA and the Department of Energy announced plans to develop a nuclear power plant on the moon by the end of the decade. The U.S. military, meanwhile, is seeking microreactors that can free remote bases and outposts from the tricky, expensive task of maintaining fossil fuel supply chains. Antares wants to compete for contracts with both agencies.
“It’s a market where cost matters, but cost is not the north star,” Bramble said.
Unlike utilities, he said, “you’re not thinking of cost solely in terms of fuel cycle, but you’re thinking of cost holistically at the system level.” In other words, TRISO may never come as cheap as traditional fuel, but something that operates safely and reliably in extreme conditions ends up paying for itself over time with spacecrafts and missile-defense systems that work as planned and don’t require replacement.
That’s a familiar market for BWXT. The company — spun out in 2015 from Babcock and Wilcox, the reactor developer that built more than half a dozen nuclear plants for the U.S. during the 20th century — already enriches the bulk of the fuel for the U.S. military’s fleet of nuclear submarines, granting BWXT the industry’s highest-possible security clearance to work on federal contracts.
But BWXT, already the country’s leading producer of TRISO, sees an even wider market for the fuel.
“The value is that it allows you to operate at really high temperatures where you get high efficiencies,” Joseph Miller, BWXT’s president of government operations, told me. “We already have a lot of customer intrigue from the mining industry. I can see the same thing for synthetic fuels and desalination.”
BWXT isn’t alone in producing TRISO. Last month, the startup Standard Nuclear raised $140 million in a Series A round to build out its supply chain for producing TRISO. X-energy is establishing its own production line through a subsidiary called TRISO-X. And that’s just in the U.S. Russia’s state-owned nuclear company, Rosatom, is ramping up production of TRISO. China, which operates the world’s only commercial high-temperature gas-cooled reactor at the moment, also generates its own TRISO fuel.
Beijing’s plans for a second reactor based on that fourth-generation design could indicate a problem for the U.S. market: TRISO may work better in larger reactors, and America is only going for micro-scale units.
The world-leading high-temperature gas reactor China debuted in December 2023 maxes out at 210 megawatts of electricity. But the second high-temperature gas reactor under development is more than three times as powerful, with a capacity of 660 megawatts. At that size, the ultra-high temperatures a gas reactor can reach mean it takes longer for the coolant — such as the helium used at Fort St. Vrain — to remove heat. As a result, “you need this robust fuel form that releases very little radioactivity during normal operation and in accident conditions,” Koroush Shirvan, a researcher who studies advanced nuclear technologies at the Massachusetts Institute of Technology, told me.
But microreactors cool down faster because there’s less fuel undergoing fission in the core. “Once you get below a certain power level,” Shrivan said, “why would you have [TRISO]?”
Given the military and space applications Antares is targeting, however, where the added safety and functionality of TRISO merits the higher cost associated with using it, the company has a better use case than some of its rivals, Shrivan added.
David Petti, a former federal researcher who is one of the leading U.S. experts on TRISO, told me that when the government was testing TRISO for demonstration reactors, the price was at least double that of traditional reactor fuel. “That’s probably the best you could do,” he said in reference to the cost differential.
There are other uranium blends inside the TRISO pellets that could prove more efficient. The Chinese, for example, use uranium dioxide, essentially just an encased version of traditional reactor fuel. The U.S., by contrast, uses uranium oxycarbide, which allows for increased temperatures and higher burnups of the enriched fuel. Another option, which Bramble said he envisions Antares using in the future, would be uranium nitride, which has a greater density of fuel and could therefore last longer in smaller reactors used in space.
“But it’s not as tested in a TRISO system,” Petti said, noting that the federal research program that bolstered the TRISO efforts going on now started in 2002. “Until I see a good test that it’s good, the time and effort it takes to qualify is complicated.”
Since the uranium in TRISO is typically enriched to higher levels than standard fuel, BWXT’s facilities are subject to stricter safety rules, which adds “significant overhead,” Petti said.
“When you make a lot of fuel per year in your fuel factory, you can spread that cost and you can get a number that may be economic,” he said. “When you have small microreactors, you’re not producing an awful lot. You have to take that cost and charge it to the customer.”
BWXT is bullish on the potential for its customer base to grow significantly in the coming years. The company is negotiating a deal with the government of Wyoming to open a new factory there entirely dedicated to TRISO production. While he wouldn’t give specifics just yet, Miller told me BWXT is developing new technologies that can make TRISO production cheaper. He compared the cost curve to that of microchips, an industry in which he previously worked.
“Semiconductors were super expensive to manufacture. They were almost cost prohibitive,” Miller said. “But the cost curve starts to drop rapidly when you fully understand the manufacturing process and you know how to integrate the understanding into operational improvements.”
He leaned back in his chair on our Zoom call, and cracked a smile. “Frankly,” he said, “I feel more confident every day that we’re going to get a really, really cost driven formula on how to manufacture TRISO.”
The startup — founded by the former head of Tesla Energy — is trying to solve a fundamental coordination problem on the grid.
The concept of virtual power plants has been kicking around for decades. Coordinating a network of distributed energy resources — think solar panels, batteries, and smart appliances — to operate like a single power plant upends our notion of what grid-scale electricity generation can look like, not to mention the role individual consumers can play. But the idea only began taking slow, stuttering steps from theory to practice once homeowners started pairing rooftop solar with home batteries in the past decade.
Now, enthusiasm is accelerating as extreme weather, electricity load growth, and increased renewables penetration are straining the grid and interconnection queue. And the money is starting to pour in. Today, home battery manufacturer and VPP software company Lunar Energy announced $232 million in new funding — a $102 million Series D round, plus a previously unannounced $130 million Series C — to help deploy its integrated hardware and software systems across the U.S.
The company’s CEO, Kunal Girotra, founded Lunar Energy in the summer of 2020 after leaving his job as head of Tesla Energy, which makes the Tesla Powerwall battery for homeowners and the Megapack for grid-scale storage. As he put it, back then, “everybody was focused on either building the next best electric car or solving problems for the grid at a centralized level.” But he was more interested in what was happening with households as home battery costs were declining. “The vision was, how can we get every home a battery system and with smart software, optimize that for dual benefit for the consumer as well as the grid?”
VPPs work by linking together lots of small energy resources. Most commonly, this includes solar, home batteries, and appliances that can be programmed to adjust their energy usage based on grid conditions. These disparate resources work in concert conducted by software that coordinates when they should charge, discharge, or ramp down their electricity use based on grid needs and electricity prices. So if a network of home batteries all dispatched energy to the grid at once, that would have the same effect as firing up a fossil fuel power plant — just much cleaner.
Lunar’s artificial intelligence-enabled home energy system analyzes customers’ energy use patterns alongside grid and weather conditions. That allows Lunar’s battery to automatically charge and discharge at the most cost-effective times while retaining an adequate supply of backup power. The batteries, which started shipping in California last year, also come integrated with the company’s Gridshare software. Used by energy companies and utilities, Gridshare already manages all of Sunrun’s VPPs, including nearly 130,000 home batteries — most from non-Lunar manufacturers — that can dispatch energy when the grid needs it most.
This accords with Lunar’s broader philosophy, Girotra explained — that its batteries should be interoperable with all grid software, and its Gridshare platform interoperable with all batteries, whether they’re made by Lunar or not. “That’s another differentiator from Tesla or Enphase, who are creating these walled gardens,” he told me. “We believe an Android-like software strategy is necessary for the grid to really prosper.” That should make it easier for utilities to support VPPs in an environment where there are more and more differentiated home batteries and software systems out there.
And yet the real-world impact of VPPs remains limited today. That’s partially due to the main problem Lunar is trying to solve — the technical complexity of coordinating thousands of household-level systems. But there are also regulatory barriers and entrenched utility business models to contend with, since the grid simply wasn’t set up for households to be energy providers as well as consumers.
Girotra is well-versed in the difficulties of this space. When he first started at Tesla a decade ago, he helped kick off what’s widely considered to be the country’s first VPP with Green Mountain Power in Vermont. The forward-looking utility was keen to provide customers with utility-owned Tesla Powerwalls, networking them together to lower peak system demand. But larger VPPs that utilize customer-owned assets and seek to sell energy from residential batteries into wholesale electricity markets — as Lunar wants to do — are a different beast entirely.
Girotra thinks their time has come. “This year and the next five years are going to be big for VPPs,” he told me. The tide started to turn in California last summer, he said, after a successful test of the state’s VPP capacity had over 100,000 residential batteries dispatching more than 500 megawatts of power to the grid for two hours — enough to power about half of San Francisco. This led to a significant reduction in electricity demand during the state’s evening peak, with the VPP behaving just like a traditional power plant.
Armed with this demonstration of potential and its recent influx of cash, Lunar aims to scale its battery fleet, growing from about 2,000 deployed systems today to about 10,000 by year’s end, and “at least doubling” every year after that. Ultimately, the company aims to leverage the popularity of its Gridshare platform to become a market maker, helping to shape the structure of VPP programs — as it’s already doing with the Community Choice Aggregators that it’s partnered with so far in California.
In the meantime, Girotra said Lunar is also involved in lobbying efforts to push state governments and utilities to make it easier for VPPs to participate in the market. “VPPs were always like nuclear fusion, always for the future,” he told me. But especially after last year’s demonstration, he thinks the entire grid ecosystem, from system operators to regulators, are starting to realize that the technology is here today. ”This is not small potatoes anymore.”