Supplying clean power is easier than storing it

Cutting emissions relies on energy-storage technology coming of age

It sounds simple:  lift heavy blocks with a crane, then capture the power generated from dropping them. This is not an experiment designed by a ten-year-old, but the premise of Energy Vault, which has raised $110m from SoftBank, a big Japanese tech investor. The idea has competition. A cluster of billionaires including Bill Gates, Jack Ma, Ray Dalio and SoftBank’s Masayoshi Son are backing other schemes to capture power. A firm incubated at Alphabet, Google’s parent company, wants to store electricity in molten salt. Such plans hint at one of the power business’s hardest tasks. Generating clean power is now relatively straightforward. Storing it is far trickier.

Solar and wind last year produced 7% of the world’s electricity. By 2040, that share could grow by over five times, according to the International Energy Agency, an intergovernmental forecaster. The trouble is, a lull in the wind leaves a turbine listless. Clouds have a habit of blocking the sun. That means that solar and wind cannot, on their own, replace coal and gas plants, which produce continual power reliably.

One answer is to store power in batteries, which promise to gather clean electricity when the sun and wind produce more than is required and dispatch it later, as it is needed. In 2018 some 3.5 gigawatts of storage was installed, about twice the amount in 2017, according to Bloombergnef, an energy data firm. Total investment in storage this year may reach $5.3bn, it estimates. As this grows it could drive an extraordinary expansion (see chart). However at present only about 1% of renewable energy is complemented by storage, reckons Morgan Stanley, a bank. There are still plenty of hurdles to clear.

The most common method of storage so far has been to pump water into an elevated reservoir at times of plenty and release it when electricity is needed. This type of hydropower is not the answer to providing lots more storage. Building a new reservoir requires unusual topography and it can wreak environmental havoc.

Batteries offer an alternative and availability should improve as electric cars become ever more popular. “The whole production supply chain for lithium-ion batteries for electric vehicles is gearing up,” says Andrés Gluski of aes, an electricity company, “so we’re going to piggyback on that.” As greater demand led to greater manufacturing scale, the cost of batteries dropped by 85% from 2010 to 2018, according to Bloombergnef. That makes batteries cheap enough not only to propel mass-market electric cars but for use in the power system, too.

And as electric cars become more widespread their batteries could serve as a source of mobile storage, feeding power back into the grid, if required, when the vehicles are parked and plugged in. With the right infrastructure in place, fleets of electric cars could substitute for new dedicated storage capacity.

Batteries do a variety of things. A firm called Sunrun sells residential solar panels paired with batteries, a particularly appealing proposition for Californian homeowners desperate for an alternative to fire-induced blackouts. Within the broader grid, batteries can act as a shock absorber to deal with variations in supply from one minute to the next. Other uses include shifting electricity supply from the day, when solar panels often produce a surfeit of power, to the evening, when demand rises.

The growth of storage is becoming a headache for old-fashioned power generators that rely on gas or coal. NextEra Energy Resources, which builds clean-power installations, is increasingly pairing large solar farms with batteries. aes, which has battery-storage facilities in 21 countries and territories, runs a scheme in Hawaii that combines solar with storage to meet peaks in demand. The Rocky Mountain Institute, a clean-energy research group, warns that solar and battery projects, combined with measures such as smarter appliances to control demand, may turn gas-powered plants into stranded assets.

Nevertheless, the battery industry faces several barriers to broader deployment. To start with, if a battery overheats it can catch fire, producing gases that might explode. In the past year installations in South Korea have caught fire. A fire and explosion in April damaged a storage site in Arizona run by Fluence, a joint venture between aes and Siemens, a German engineering giant. The causes are still under investigation. As the industry matures, safety measures are likely to become more rigorous.

In the meantime, the industry will have to cope with a patchwork of other rules and regulations. South Korea has offered incentives for storage, in part to create a market for its domestic battery-makers, which are among the world’s leaders. Some states in America, such as New York and New Jersey, have mandated storage to help reduce emissions. In others, America’s federal electricity regulator is trying to open markets to storage, but the details of how that will work in practice are unclear. In Britain, batteries are deemed “generation assets”, which exposes storage developers to extra fees and costs, says Michael Folsom of Watson Farley & Williams, a law firm.

Even if electricity regulations were smoothed, lithium-ion batteries would eventually reach their limits. Breakthrough Energy Ventures (bev) is a fund backed by Messrs Gates, Ma, Dalio and other billionaires to invest in transformational technologies. The cost of lithium-ion batteries is falling quickly, but to store power for days let alone weeks “lithium-ion is never going to get cheap enough”, says Eric Toone, bev’s head of science.

Alternatives include flow batteries, that use electrolytes in tanks of chemical solution, as well as mechanical means such as Energy Vault’s falling blocks. Hydrogen can also be made using clean power and turned back into electricity in gas-fired power plants or fuel cells. In the future liquefied gases might provide a solution (see article). Unlike solar panels, which have become standardised, different batteries are likely to serve different purposes on a grid. “All batteries are like humans, equally flawed in some specific way,” says Mateo Jaramillo, who led storage development at Tesla, an electric carmaker.

Mr Jaramillo now leads Form Energy, a firm that is developing an electrochemical alternative to lithium-ion batteries. Investors include bev and Eni, an large Italian oil and gas firm. Mr Jaramillo declines to predict when his work will be commercialised. But the goal is clear. “If you can develop a long-term storage solution,” he says, “that’s how you retire coal and that’s how you retire natural gas.” SOURCE

How the humble chairlift could revolutionize renewable energy

JOSEPH EID / AFP via Getty Images

What do you see when you imagine a zero-carbon future? Electric buses zipping by? Rolling hills covered with solar panels? Offshore wind farms towering over the sea? If batteries are part of your vision, good thinking. But there’s a promising, if whimsical, piece of the renewable energy puzzle that might be missing from your mental picture: the world of gravity energy storage.

When the grid depends on clean but sporadic natural resources like wind and the sun, we’re going to need ways to capture any extra energy they produce so we can use it later. Lithium-ion batteries help solve that problem, but they have limitations. They degrade over time, and they aren’t suited to store energy for months-long periods, like a seasonal stretch of gray skies or motionless air.

Enter gravity energy storage. Generating electricity using gravity is hardly a new concept — think of your classic hydropower plant, which captures the energy of falling water via a turbine. But some hydropower systems don’t just produce energy. A “pumped-storage” hydroelectric plant draws excess energy from the grid and uses it to pump water back up into an elevated reservoir where it can fall again. When full, the upper reservoir is like a charged battery, ready to be deployed for weeks or months at a time, depending on how much water it holds.

The United States already uses pumped-storage hydropower. In fact, it currently accounts for 95 percent of our utility-scale energy storage. But it’s tough to add a new pumped-storage project to the grid — it requires building a dam and creating new reservoirs, which are expensive and politically unpopular. Two-thirds of existing pumped-storage hydropower plants were built in the 1970s and 1980s. Only one new plant has come online in the past fourteen years.

But who needs water when there are all kinds of things we can slide down a mountain or drop off a cliff? Really, you can use almost any material for gravity energy storage, as long as it’s heavy, cheap, and you can figure out how to transport it up and down a steep slope.


This incredible illustration depicts a system called “Mountain Gravity Energy Storage” that was proposed in the journal Energy last week. It involves a ski-lift-style cable that carries huge bins of sand up and down a mountain. The sand gets stored in an enormous vessel at the top, and when the grid needs extra energy, it’s sent down the mountain, pulled by the force of gravity, thereby powering an electric generator. Depending on the amount of sand, the height of the mountain, and the speed of the fall, the authors estimate that it can generate electricity for anywhere from five to 555 days.

As idiosyncratic as it may seem, this isn’t a new idea. Julian Hunt, the lead author of the study and a postdoc at the International Institute for Applied Systems Analysis, said he was inspired by a similar project that Bill Gates invested in back in 2012. “I don’t think it actually worked out,” Hunt said. “So I was trying to find ways to make it viable and trying to estimate the cost of the project.”

The Bill Gates-funded venture was a company called Energy Cache, and the model was nearly identical. The company actually built a 50-kilowatt prototype back in 2012. It got as far as entering discussions with grid operators, but never had a chance to prove it could work at utility scale. Aaron Fyke, one of the founders of Energy Cache, told Grist they couldn’t find the money they needed to keep going.


But today, Fyke said, policies like 100 percent clean energy bills and energy storage mandates in several states have made the market for storage more attractive to investors. And while there’s no ski-lift charging facility in the world yet, there are several other unconventional ideas that are much closer to becoming a reality.

Engineers have patented systems that would utilize the slopes of defunct coal mines — of which there are hundreds of thousands around the world — to haul soil, coal dust, or other earth materials to higher and lower elevations. Several companies are developing alternatives that involve dropping a heavy cylindrical weight into a big hole in the ground. Near the southern tip of Nevada, a company called Advanced Rail Energy Storage is currently building a train to nowhere across 106 acres of public land that will transport heavy weights up and down a hill. It’s expected to be operational next year.


Then there’s Energy Vault, a Jenga-like tower made of concrete bricks, perpetually being assembled and destroyed by 400-foot tall puppeteering cranes. When energy is needed, the cranes select bricks to drop down to the ground. Fyke, who’s now an advisor for Energy Vault, said the system’s advantage is that it’s modular and can be placed anywhere — it doesn’t require a mountain slope or a pit in the ground. The company is planning to construct two full-scale models in Italy and India.

The potential of gravity energy storage is almost limitless. So next time you’re lost in thought, envisioning our green energy future, don’t forget to put some ski-lifts, ghost trains, and Jenga towers on the landscape, okay? SOURCE