WASHINGTON – The Department of Energy announced new efforts Wednesday to address one of the most difficult engineering challenges facing President Biden’s quest for a solar and wind-dominated power grid – namely, what to do when the sun stops shining and the wind stops blowing.

The government is pursuing a promising but unsafe solution: an inexpensive way to store electricity generated by the sun or wind for hours, days, or even weeks, so that it can be stored when it is needed most. That goes far beyond what current batteries can do. While dozens of companies are working on different ideas for so-called “long-term energy storage”, most are still too expensive to make sense.

As part of its initiative, the Ministry of Energy wants to reduce the cost of long-term storage by 90 percent below the cost of today’s lithium-ion batteries by 2030. The agency will direct experts in its national laboratories to focus on improving such technologies while seeking funding for early demonstration projects from Congress.

The announcement is part of the agency’s Energy Earthshots initiative, which aims to accelerate the deployment of emerging technologies to combat climate change. The program is in recognition of the fact that the United States has not yet developed all of the technology it needs to meet Mr. Biden’s goal of reducing the country’s emissions to zero by 2050 to warm the planet.

“If we want to achieve net zero emissions, we not only have to use proven solutions such as wind and solar energy,” said Jennifer Granholm, Minister of Energy, in an interview at the beginning of the year. “We also need to figure out how to scale clean energy technologies that have been demonstrated in a laboratory to the world. This is really urgent. “

Last month, Ms. Granholm announced a goal of cutting the cost of clean hydrogen fuels by 80 percent, which could help curb emissions from factories, trucks or the power grid. Both programs are modeled after the Obama-era Sunshot Initiative, which is credited for helping reduce the cost of solar power and bring the technology into the mainstream in the 2010s.

To achieve his goal of having the United States getting 100 percent of its electricity from zero-carbon power plants by 2035, Biden is turning to increasingly cheaper solar and wind power. The White House is currently trying to convince Congress to use a clean standard of electricity that would require utilities nationwide to achieve this goal.

The electricity sector is responsible for a quarter of greenhouse gas emissions in the United States, with about 60 percent of electricity still generated from burning fossil fuels, mostly natural gas and coal. The Biden government sees curbing electricity emissions as a central part of its climate plans as it is also trying to convince Americans to buy more electric cars and heat pumps that plug into the grid.

But cleaning up the power sector requires more than just new laws, experts said. It also poses major technological challenges.

Several recent studies have shown that utility companies could plausibly get 80 percent clean electricity using today’s technology, mainly by installing significantly more wind turbines and solar panels and using existing hydroelectric dams and nuclear reactors.

But cleaning up the last 20 percent of emissions could prove to be more difficult. One obstacle: wind and solar parks only generate electricity when the weather conditions are favorable. This means that utilities today still rely on gas or coal-fired power plants as a backup.

Many utility companies are now installing large arrays of lithium-ion batteries, similar to those used in electric cars, to accommodate fluctuations in supply. However, these batteries usually only store four to six hours of electricity at a time, which is not enough to handle major seasonal fluctuations in wind and solar energy. In some regions of the country there may be days or weeks with little wind.

There are plausible solutions, but many still have disadvantages. Network operators could build massive new transmission lines across the country on the theory that it’s usually windy somewhere. But some communities have spoken out against new power lines.

Utilities could also use excess wind and solar power to produce hydrogen, which can then be cleanly burned into electricity when needed. This fall, the New York Electricity Department will test this type of “green” hydrogen as a replacement for some of the gas that normally burns at a Long Island facility. But for now, this remains more expensive than burning fossil fuels like natural gas.

Another possibility is the development of new types of carbon-free power plants that can run around the clock, such as modern nuclear reactors, geothermal systems or gas-fired power plants that can capture and bury their emissions underground. But many of these technologies are still in their infancy.

Long-term storage offers another potentially useful option. Dozens of companies are experimenting with different devices that could store electricity over a longer period of time.

Some utility companies build pumped storage hydropower, an older technology that uses electricity when there is an abundant pumping of water uphill and releases the water to turn a turbine for electricity when needed. The Los Angeles Department of Water and Power is researching ways to inject compressed air or hydrogen into underground salt caverns that can later be used to generate electricity.

Other companies are working on new battery chemistries. Form Energy, a Bill Gates-backed startup, recently announced it is partnering with a Minnesota utility on a pilot project to build an aqueous air battery that could provide 150 hours of uninterrupted electricity.

However, energy researchers say that these long-term storage technologies have to get drastically cheaper to be profitable, also because they are seldom operated. A recent study in Nature Energy estimates that capacity costs may need to drop below $ 50 per kilowatt-hour – about a third of the cost of today’s grid-scale lithium-ion batteries – before utility companies begin to deploy long-term storage on a larger scale. And such storage may only have to cost $ 1 to $ 10 per kilowatt hour before it becomes a dominant solution.

“These cost targets will not be easy to achieve, although they match the goals of many developers,” said Nestor Sepulveda, who led the study as a researcher at the Massachusetts Institute of Technology. “A major obstacle right now is that utility companies are not legally obliged to build long-term storage facilities. It’s easier and cheaper to just burn natural gas. “

Ultimately, it can take years for utility companies to have a clear sense of which technologies work best to balance large amounts of wind and solar energy. Jesse Jenkins, an expert at Princeton University, said long-term storage could play a valuable role if it gets cheap. However, during his research, he found that utilities are likely to need a mix of different solutions for a clean grid, possibly including hydrogen or advanced zero-emission power plants that can run 24/7.

“Energy storage as the Holy Grail answer to wind and solar intermittivity has a strong focus on energy storage,” said Dr. Jenkins. “And we’ve found that it can be a solution, but it’s one of many. So today we have to make as many bets as possible on new technologies so that when we really need them in a decade or two, they are ready to go. “