Low-emissions sources are set to cover almost all the growth in global electricity demand in the next three years

U.S. Renewable Energy Forecast 2024 will see wind and solar power surpass one-fourth of electricity generation, EIA projects, as coal declines, natural gas dips, and clean energy capacity, grid integration, and policy incentives expand.

Key Points

EIA outlook: renewables at 26% of U.S. power in 2024, led by wind and solar as coal declines and gas share dips.

✅ Wind and solar hit 18% combined, surpassing coal's 17%.

✅ Natural gas dips to 37% as demand rebounds modestly.

✅ Coal plant closures accelerate amid costs, emissions, and age.

Renewable energy is poised to reach a milestone, after a record 28% in April this year, as a new government report projects that wind, solar and other renewable sources will exceed one-fourth of the country’s electricity generation for the first time, in 2024.

This is one of the many takeaways from the federal government’s Short Term Energy Outlook, a monthly report whose new edition is the first to include a forecast for 2024. The report’s authors in the Energy Information Administration are expecting renewables to increase in market share, while natural gas and coal would both decrease.

From 2023 to 2024, renewables would rise from 24 percent to 26 percent of U.S. electricity generation; coal’s share would drop from 18 percent to 17 percent; gas would remain the leader but drop from 38 percent to 37 percent; and nuclear would be unchanged at 19 percent.

It was a big deal in 2020 when generation from renewables passed coal for the first time in 130 years over a full year. Coal made a comeback in 2021 and then retreated again in 2022 as renewables surpassed coal in generation. The ups and downs were largely the result of fluctuations in electricity demand during and then after the Covid-19 pandemic.

The new report indicates that coal doesn’t have another comeback in the works. This fuel, which was the country’s leading electricity source less than a decade ago, is declining as many coal-fired power plants are old and economically uncompetitive. Coal plants continue to close, and developers aren’t building new ones because of concerns about high costs and emissions, a trend underscored when renewables became the second-most prevalent source in 2020 across the U.S.

The growth in renewable energy is coming from wind and solar power, with wind responsible for about one-third of the growth and solar accounting for two-thirds, the report says, and combined output from wind and solar has already exceeded nuclear for the first time in the U.S. Other renewable sources, like hydropower and biomass, would be flat.

In fact, the growth of wind and solar is projected to be so swift that the combination of just those two sources would be 18 percent of the U.S. total by 2024, which would surpass coal’s 17 percent.

A key variable is overall electricity consumption. EIA is projecting that this will fall 1 percent in 2023 compared to 2022, due a mild summer. Then, consumption will increase 1 percent in 2024.

If demand was rising more, then natural gas power would likely gain market share because of gas power plants’ ability to vary their output as needed to respond to changes in demand.

I asked Eric Gimon, a senior fellow at the think tank Energy Innovation, what he thinks of these latest numbers.

He said wind and solar have gotten so big that it almost makes sense to track them as their own categories as opposed to lumping them into the larger category of renewables. He expects that the government will do this sometime soon.

Also, he thinks the projected increases for wind and solar, while substantial, are still smaller than those resources are likely to grow.

“My experience over the last 10 years is that the EIA tends to have flattish forecasts,” he said, meaning the federal office has underestimated the actual growth.

Some energy analysts have criticized EIA for being slow to recognize the growth of renewables. But much of the criticism is about the Annual Energy Outlook, which has numbers going out to mid-century, even as the U.S. is moving toward 30% from wind and solar by the end of the decade. The Short Term Energy Outlook, with numbers going one year into the future, has been more reliable.

Gimon said EIA is “kind of like your conservative uncle” in its forecasts, so it’s notable that the office expects to see a significant uptick in wind and solar.

Even so, he thinks the latest Short Term Energy Outlook should be read as the lower end of the range of potential increase for wind and solar.

For him to be right, the wind and solar industries will need to figure out solutions to the challenges they’ve been having in obtaining parts; they will need to make progress in dealing with local opposition to many projects and in having enough interstate power lines to deliver the electricity. And, new policies like the Inflation Reduction Act will need to have their desired effect of encouraging projects through the use of tax incentives.

It’s not much of a stretch to imagine that clean energy industries will make some progress on all of those fronts.

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Michigan Distributed Energy Cap Repeal advances a bipartisan bill to boost rooftop solar and net metering, countering DTE and Consumers Energy claims, expanding energy freedom, jobs, and climate resilience across investor-owned utility territories.

Key Points

A Michigan bill to remove the 1% distributed energy cap, expanding rooftop solar, net metering, and clean energy jobs.

✅ Removes 1% distributed generation cap statewide

✅ Supports rooftop solar, net metering, and job growth

✅ Counters utility cost-shift claims with updated tariffs

A bipartisan group of Michigan lawmakers has introduced legislation to eliminate a 1% cap on distributed energy in the state’s investor-owned utility territories.

It’s the third time in recent years that such legislation has been introduced. Though utilities and their political allies have successfully blocked it to date, through tactics some critics say reflect utilities tilting the solar market by incumbents, advocates see an opportunity with a change in state Republican caucus leadership and Michigan’s burgeoning solar industry approaching the cap in some utility territories.

The bill also has support from a broad swath of legislators for reasons having to do with job creation, energy freedom and the environment, amid broader debates over states' push for renewables and affordability. Already the bill has received multiple hearings, even as DTE Energy and Consumers Energy, Michigan’s largest private utilities, are ramping up attacks in an effort to block the bill. 

“It’s going to be vehemently opposed by the utilities but there are only benefits to this if you are anybody but DTE,” said Democratic state Rep. Yousef Rabhi, who cosigned HB 4236 and has helped draft language in previous bills. “If we remove the cap, then we’re putting the public’s interest first, and we’re putting DTE’s interest first if we keep the cap in place.” 

The Michigan Legislature enacted the cap as part of a sweeping 2016 energy bill that clean energy advocates say included a number of provisions that have kneecapped the small-scale distributed energy industry, particularly home solar. The law caps distributed energy production at 1% of a utility’s average in-state peak load for the past five years. 

Republicans have controlled the Legislature and committees since the law was enacted, amid parallel moves such as the Wyoming clean energy bill in another state, and previous attempts to cut the language haven’t received House committee hearings. However, former Republican House leader Lee Chatfield has been replaced, and already the new bill, introduced by Republican state Rep. Gregory Markkanen, the energy committee’s vice chair, has had two hearings. 

Previous attempts to cut the language were also a part of a larger package of bills, and this time around the bill is a standalone. The legislation is also moving as Consumers and Upper Peninsula Power Co. have voluntarily doubled their cap to two percent, which advocates say highlights the need to repeal the cap . 

Rabhi said there’s bipartisan support because many conservatives and progressives view it as an infringement on customers’ energy freedom since the cap will eventually effectively prohibit new distributed energy generation. Legislators say the existing law kills jobs because it severely limits the clean energy industry’s growth, and Rabhi said he’s also strongly motivated by increasing renewable energy production to address climate change. 

In February, Michigan Public Service Commission Chairman Dan Scripps testified to the House committee, with observers also pointing to FERC action on aggregated DERs as relevant context, that the commission is “supportive in taking steps to ensure solar developers in Michigan are able to continue operating and thus support in concept the idea of lifting or eliminating the cap” in order to protect the home solar industry. 

The state’s solar industry has long criticized the cap, and removing it is a “no brainer,” said Dave Strenski, executive director of Solar Ypsi, which promotes rooftop solar in Ypsilanti. 

“If they have a cap and we reach that cap, then rooftop solar is shut down in Michigan,” he said. “The utilities don’t mind solar as long as they own it, and that’s what it boils down to.”  

The state’s utilities see the situation differently. Spokespeople for DTE and Consumers told the Energy News Network that lifting the cap would shift the cost burden of maintaining their territory-wide infrastructure from all customers to low income customers who can’t afford to install solar panels, often invoking reliability examples such as California's reliance on fossil generation to justify caution.

The bill “doesn’t address the subsidy certain customers are paid at the expense of those who cannot afford to put solar panels on their homes,” said Katie Carey, Consumers Energy’s spokesperson. 

However, clean energy advocates argue that studies have found that to be untrue. And even if it were true, Rabhi said, the utilities told lawmakers in 2016 that a new inflow/outflow tariff that the companies successfully pushed for to replace net metering dramatically reduced compensation for home solar users and would address that inequality. 

“DTE’s and Consumers’ own argument is that by making that change, distributed generation is no longer a ‘burden’ on low income customers, so now we have inflow/outflow and the problem should be solved,” Rabhi said. 

He added that claims that DTE and Consumers are looking out for low-income customers are disingenuous because they have repeatedly fought larger allowances for programs that help those customers, and refuse to “dip into their massive corporate profits and make sure poor people don’t have to pay as much for electricity.”

“I don’t want to hear a sob story from DTE about how putting solar panels on the house is going to hurt poor people,” he said. “That is entirely the definition of hypocrisy — that’s the utilities using poor people as a pawn and that’s why people are sick of these corporations.” 

The companies have already begun their public relations attack designed to help thwart the bill. DTE and Consumers spread money generously among Republicans and Democrats in the Legislature each cycle, and the two companies’ dark money nonprofits launched a round of ads targeting Democratic lawmakers, reflecting the broader solar wars playing out nationally. Several sit on the House Energy Committee, which must approve the bill before it can go in front of the full Legislature. 

The DTE-backed Alliance For Michigan Power and Consumers Energy-funded Citizens Energizing Michigan’s Economy have purchased dozens of Facebook ads alluding to action by the legislators, though there hasn’t been a vote. 

Facebook ads aren’t uncommon as they get “bang for their buck,” said Matt Kasper, research director with utility industry watchdog Energy And Policy Institute. Already hundreds of thousands of people have potentially viewed the ads and the groups have only spent thousands of dollars. The ads are likely designed to get Facebook users to interact with the legislators on the issue, Kasper said, even if there’s little information in the ad, and the info in the ad that does exist is highly misleading.

DTE and Consumers spokespersons declined to comment on the spending and directed questions to the dark money nonprofits. No one there could be reached for comment.

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Chinese EV Makers in Europe target the EU market with electric SUVs, battery swapping, competitive pricing, and subsidies, led by NIO, Xpeng, MG, and BYD, starting in Norway amid Europe's zero-emissions push.

Key Points

Chinese EV makers expanding into EU markets with tech, pricing, and lean retail to gain share.

✅ Early launches in Norway leverage EV incentives

✅ Compete via battery swapping, OTA tech, and price

✅ Mix of importers, online sales, and lean dealerships

China's electric carmakers are darting into Europe, hoping to catch traditional auto giants cold and seize a slice of a market supercharged by the continent's EV transition towards zero emissions.

Nio Inc (NIO.N), among a small group of challengers, launches its ES8 electric SUV in Oslo on Thursday - the first foray outside China for a company that is virtually unheard of in Europe even though it's valued at about $57 billion.

Other brands unfamiliar to many Europeans that have started selling or plan to sell cars on the continent include Aiways, BYD's (002594.SZ) Tang, SAIC's (600104.SS) MG, Dongfeng's VOYAH, and Great Wall's (601633.SS) ORA.

Yet Europe, a crowded, competitive car market dominated by famous brands, has proved elusive for Chinese carmakers in the past. They made strategic slips and also contended with a perception that China, long associated with cheap mass-production, could not compete on quality.

Indeed, Nio Chief Executive William Li told Reuters he foresees a long road to success in a mature market where it is "very difficult to be successful".

Chinese carmakers may need up to a decade to "gain a firm foothold" in Europe, the billionaire entrepreneur said - a forecast echoed by He Xiaopeng, CEO of electric vehicle (EV) maker Xpeng (9868.HK) who told Reuters his company needs 10 years "to lay a good foundation" on the continent.

These new players, many of which have only ever made electric vehicles, believe they have a window of opportunity to finally crack the lucrative market.

While electric car sales in the European Union more than doubled last year and jumped 130% in the first half of this year, even as threats to the EV boom persist, traditional manufacturers are still gradually shifting their large vehicle ranges over to electric and have yet to flood the thirsty market with models.

"The market is not that busy yet, if you compare it with combustion-engine models where each of the major carmakers has a whole range of vehicles," said Alexander Klose, who heads the foreign operations of Chinese electric vehicle maker Aiways.

"That is where we think we have an opportunity," he added on a drive around Munich in a U5, a crossover SUV on sale in Germany, the Netherlands, Belgium and France, where new EV rules are aimed at discouraging purchases of Chinese models.

The U5 starts at 30,000 euros ($35,000) in Germany - below the average new car price and most local EV prices - before factoring in 9,000 euros in EV subsidies, though France's EV incentives have tightened for Chinese models - and comes in just four colours and two trim levels to minimize costs.

'GERMAN PEOPLE BUY GERMAN CARS'
As Chinese carmakers gear up to enter Europe, they are trying out different business models, from relying on importers, low-cost retail options or building up more traditional dealerships.

The new reality that top Western carmakers like BMW (BMWG.DE) and Tesla Inc (TSLA.O) now produce cars in technological powerhouse China, where the EV market is intensely competitive, has likely undermined past perceptions of low quality workmanship - though they can be hard to shake.

Antje Levers, a teacher who lives in western Germany near the Dutch border, and her husband owned a diesel Chevrolet Orlando but wanted a greener option. They bought an Aiways U5 last year after plenty of research to fend off criticism for not buying local, and loves its handling and low running costs.

She said people had told her: "You can't buy a Chinese car, they're plastic and cheap and do not support German jobs." But she feels that is no longer true in a global car industry where you find German auto parts in Chinese cars and vice versa.

"German people buy German cars, so to buy a Chinese car you need to have a little courage," the 47-year-old added. "Sometimes you just have to be open for new things."

NIO LANDS IN NORWAY WITH NOMI
Nio launches its ES8 electric SUV alongside a NIO House - part-showroom, part-cafe and workspace for customers in the capital of Norway, a country that's also the initial base for Xpeng.

Norwegian state support for EVs has put the country at the forefront of the shift to electric. It makes sense as a European entry point because customers are used to electric vehicles so only have to be sold on an unknown Chinese brand, said Christina Bu, secretary general of the Norwegian EV Association.

"If you go to another European country you may struggle to sell both," said Bu, adding that her organisation has talked extensively with a number of Chinese EV makers keen to learn market specifics and consumer culture before launching there.

She is uncertain, though, how consumers will react to Nio's approach of swapping out batteries for customers rather than stopping to charge them, a contrast to other EV battery strategies in the industry, or the carmaker's strategy of leasing rather than selling batteries to customers.

"But where the Chinese are really at the forefront is the technology," she added, referring in particular to Nomi, the digital assistant in the dashboard of Nio's cars.

NEWCOMERS' STRATEGIES DIVERGE
One size does not fit all. While Nio and Xpeng have been hiring staff building up their organizations in Norway, SAIC's MG works through a car importer to sell cars in a handful of European markets.

Aiways is trying an lower-cost approach to selling cars in Europe, though Klose says it varies by market.

In Germany, for instance, the company sells its cars through Euronics, an association of independent electronics retailers, rather than building traditional dealerships.

It aims to sell across the EU by next year and to enter the U.S. market by 2023, said Klose, a former Volvo and Ford executive.

Past failed attempts by Chinese carmakers to conquer Europe are unlikely to hurt Chinese EV makers today, as consumers have grown accustomed to electronics coming from China, he added.

Such failures included Brilliance in 2007, whose vehicle received one out of five stars in a German car crash test, damaging the brand.

"The fact there are more Chinese carmakers entering the market will also help us, as it will make Chinese brands more accepted by consumers," Klose said.

Selling cars to Europeans is a "tough business, especially if your product isn't well known," said Arnie Richters, chairman of Brussels-based industry group Platform for Electromobility.

"But if they bring a lot of innovation they have a lot of opportunity."

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U.S. Solar Panel Shipments 2021 surged to 28.8 million kW of PV modules, tracking utility-scale and small-scale capacity additions, driven by imports from Asia, resilient demand, supply chain constraints, and declining prices.

Key Points

Record 28.8M kW PV modules shipped in 2021; 80% imports; growth in utility- and small-scale capacity with lower prices.

✅ 28.8M kW shipped, up from 21.8M kW in 2020 (record capacity)

✅ 80% of PV module shipments were imports, mainly from Asia

✅ Utility-scale +13.2 GW; small-scale +5.4 GW; residential led

U.S. shipments of solar photovoltaic (PV) modules (solar panels) rose to a record electricity-generating capacity of 28.8 million peak kilowatts (kW) in 2021, from 21.8 million peak kW in 2020, based on data from our Annual Photovoltaic Module Shipments Report. Continued demand for U.S. solar capacity drove this increase in solar panel shipments in 2021, as solar's share of U.S. electricity continued to rise.

U.S. solar panel shipments include imports, exports, and domestically produced and shipped panels. In 2021, about 80% of U.S. solar panel module shipments were imports, primarily from Asia, even as a proposed tenfold increase in solar aims to reshape the U.S. electricity system.

U.S. solar panel shipments closely track domestic solar capacity additions; differences between the two usually result from the lag time between shipment and installation, and long-term projections for solar's generation share provide additional context. We categorize solar capacity additions as either utility-scale (facilities with one megawatt of capacity or more) or small-scale (largely residential solar installations).

The United States added 13.2 gigawatts (GW) of utility-scale solar capacity in 2021, an annual record and 25% more than the 10.6 GW added in 2020, according to our Annual Electric Generator Report. Additions of utility-scale solar capacity reached a record high, reflecting strong growth in solar and storage despite project delays, supply chain constraints, and volatile pricing.

Small-scale solar capacity installations in the United States increased by 5.4 GW in 2021, up 23% from 2020 (4.4 GW), as solar PV and wind power continued to grow amid favorable government plans. Most of the small-scale solar capacity added in 2021 was installed on homes. Residential installations totaled more than 3.9 GW in 2021, compared with 2.9 GW in 2020.

The cost of solar panels has declined significantly since 2010. The average value (a proxy for price) of panel shipments has decreased from $1.96 per peak kW in 2010 to $0.34 per peak kW in 2021, as solar became the third-largest renewable source and markets scaled. Despite supply chain constraints and higher material costs in 2021, the average value of solar panels decreased 11% from 2020.

In 2021, the top five destination states for U.S. solar panel shipments were:

California (5.09 million peak kW)
Texas (4.31 million peak kW)
Florida (1.80 million peak kW)
Georgia (1.15 million peak kW)
Illinois (1.12 million peak kW)
These five states accounted for 46% of all U.S. shipments, and 2023 utility-scale project pipelines point to continued growth.

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O2 Tidal Turbine delivers tidal energy in Orkney, Scotland, supplying grid-connected renewable power via EMEC and enabling green hydrogen production, providing clean electricity with predictable generation from strong coastal currents.

Key Points

A 2 MW, grid-connected tidal device in Orkney that delivers clean power and enables EMEC green hydrogen production.

✅ 2 MW capacity; powers ~2,000 UK homes via EMEC grid

✅ Predictable renewable output from strong coastal currents

✅ Enables onshore electrolyzer to produce green hydrogen

“The world’s most powerful” tidal turbine has been hooked up to the onshore electricity grid in Orkney, a northerly archipelago in Scotland, and is ready to provide homes with clean, green electricity, even as a major UK offshore windfarm begins supplying power this week.

The tidal turbine, known as the O2, was developed by Scottish engineering firm Orbital Marine Power. On July 28, they announced O2 “commenced grid connected power generation” at the European Marine Energy Centre (EMEC) in Orkney, meaning it's all set up and providing energy to the local power grid, similar to another Scottish tidal project that recently powered nearly 4,000 homes.

The 74-meter-long (242-foot) turbine is said to be “the world’s most powerful” tidal turbine. It will lay in the waters off Orkney for the next 15 years with the capacity to meet the annual electricity demand of around 2,000 UK homes. The 2MW turbine is also set to power the EMEC’s land-based electrolyzer that will generate green hydrogen (hydrogen made without fossil fuels) that can also be used as a clean energy source, in a UK energy system that recently set a wind generation record for output.

“Our vision is that this project is the trigger to the harnessing of tidal stream resources around the world and, alongside investment in UK offshore wind, to play a role in tackling climate change whilst creating a new, low-carbon industrial sector,” Orbital CEO, Andrew Scott, said in a press release.

Tidal energy is harnessed by converting energy from the natural rise and fall of ocean tides and currents. The O2 turbine consists of two submerged blades with a 20-meter (65-foot) diameter attached to a turbine that will move with the shifting currents of Orkney’s coast to generate electricity. Electricity is then transferred from the turbine along the seabed via cables towards the local onshore electricity network, a setup also being used by a Nova Scotia tidal project to supply the grid today.

This method of harnessing energy is not just desirable because it doesn't release carbon emissions, but it’s more predictable than other renewable energy sources, such as solar or Scotland's wind farms that can be influenced by weather conditions. Tidal energy production is still in its infancy and there are relatively few large-scale tidal power plants in the world, but many argue that some parts of the world could potentially draw huge benefits from this innovative form of hydropower, especially coastal regions with strong currents such as the northern stretches of the UK and the Bay of Fundy in Atlantic Canada.

The largest tidal power operation in the world is the Sihwa Lake project on the west coast of South Korea, which harnesses enough power to support the domestic needs of a city with a population of 500,000 people. However, once fully operational, the MeyGen tidal power project in northern Scotland hopes to snatch its title.

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US Renewable Energy Transition is the shift from fossil fuels to wind, solar, and nuclear, targeting net-zero emissions via grid modernization, battery storage, and new transmission to replace legacy plants and meet rising electrification.

Key Points

The move to decarbonize electricity by scaling wind, solar, and nuclear with storage and transmission upgrades.

✅ Falling LCOE makes wind and solar competitive with gas and coal.

✅ 4-hour lithium-ion storage shifts solar to evening peak demand.

✅ New high-voltage transmission links resource-rich regions to load.

Generating electricity to power homes and businesses is a significant contributor to climate change. In the United States, one quarter of greenhouse gas emissions come from electricity production, according to the Environmental Protection Agency.

Solar panels and wind farms can generate electricity without releasing any greenhouse gas emissions, and recent research suggests wind and solar could meet about 80% of U.S. demand with supportive infrastructure. Nuclear power plants can too, although today’s plants generate long-lasting radioactive waste, which has no permanent storage repository.

But the U.S. electrical sector is still dependent on fossil fuels. In 2021, 61 percent of electricity generation came from burning coal, natural gas, or petroleum. Only 20 percent of the electricity in the U.S. came from renewables, mostly wind energy, hydropower and solar energy, according to the U.S. Energy Information Administration, and in 2022 renewable electricity surpassed coal nationwide as portfolios shifted. Another 19 percent came from nuclear power.

The contribution from renewables has been increasing steadily since the 1990s, and the rate of increase has accelerated, with renewables projected to reach one-fourth of U.S. generation in the near term. For example, wind power provided only 2.8 billion kilowatt-hours of electricity in 1990, doubling to 5.6 billion in 2000. But from there, it skyrocketed, growing to 94.6 billion in 2010 and 379.8 billion in 2021.

That’s progress, as the U.S. moves toward 30% electricity from wind and solar this decade, but it’s not happening fast enough to eliminate the worst effects of climate change for our descendants.

“We need to eliminate global emissions of greenhouse gases by 2050,” philanthropist and technologist Bill Gates wrote in his 2023 annual letter. “Extreme weather is already causing more suffering, and if we don’t get to net-zero emissions, our grandchildren will grow up in a world that is dramatically worse off.”

And the problem is actually bigger than it looks, even as pathways to zero-emissions electricity by 2035 are being developed.

“We need not just to create as much electricity as we have now, but three times as much,” says Saul Griffith, an entrepreneur who’s sold companies to Google and Autodesk and has written books on mass electrification. To get to zero emissions, all the cars and heating systems and stoves will have to be powered with electricity, said Griffith. Electricity is not necessarily clean, but at least it it can be, unlike gas-powered stoves or gasoline-powered cars.

The technology to generate electricity with wind and solar has existed for decades. So why isn’t the electric grid already 100% powered by renewables? And what will it take to get there?

First of all, renewables have only recently become cost-competitive with fossil fuels for generating electricity. Even then, prices depend on the location, Paul Denholm of the National Renewable Energy Laboratory told CNBC.

In California and Arizona, where there is a lot of sun, solar energy is often the cheapest option, whereas in places like Maine, solar is just on the edge of being the cheapest energy source, Denholm said. In places with lots of wind like North Dakota, wind power is cost-competitive with fossil fuels, but in the Southeast, it’s still a close call.

Then there’s the cost of transitioning the current power generation infrastructure, which was built around burning fossil fuels, and policymakers are weighing ways to meet U.S. decarbonization goals as they plan grid investments.

“You’ve got an existing power plant, it’s paid off. Now you need renewables to be cheaper than running that plant to actually retire an old plant,” Denholm explained. “You need new renewables to be cheaper just in the variable costs, or the operating cost of that power plant.”

There are some places where that is true, but it’s not universally so.

“Primarily, it just takes a long time to turn over the capital stock of a multitrillion-dollar industry,” Denholm said. “We just have a huge amount of legacy equipment out there. And it just takes awhile for that all to be turned over.”

Intermittency and transmission
One of the biggest barriers to a 100% renewable grid is the intermittency of many renewable power sources, the dirty secret of clean energy that planners must manage. The wind doesn’t always blow and the sun doesn’t always shine — and the windiest and sunniest places are not close to all the country’s major population centers.

Wind resources in the United States, according to the the National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
Wind resources in the United States, according to the the National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
The solution is a combination of batteries to store excess power for times when generation is low, and transmission lines to take the power where it is needed.

Long-duration batteries are under development, but Denholm said a lot of progress can be made simply with utility-scale batteries that store energy for a few hours.

“One of the biggest problems right now is shifting a little bit of solar energy, for instance, from say, 11 a.m. and noon to the peak demand at 6 p.m. or 7 p.m. So you really only need a few hours of batteries,” Denholm told CNBC. “You can actually meet that with conventional lithium ion batteries. This is very close to the type of batteries that are being put in cars today. You can go really far with that.”

So far, battery usage has been low because wind and solar are primarily used to buffer the grid when energy sources are low, rather than as a primary source. For the first 20% to 40% of the electricity in a region to come from wind and solar, battery storage is not needed, Denholm said. When renewable penetration starts reaching closer to 50%, then battery storage becomes necessary. And building and deploying all those batteries will take time and money.
 

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