Mix Mountains and Gravity for Long-Term Energy Storage

Hunt and his collaborators have devised a novel method to enhance lithium-ion battery use for electricity storage in excess of the extensive operate: Mountain Gravity Strength Storage, or MGES for limited. Identical to hydroelectric ability, MGES entails storing content at elevation to develop gravitational electricity. The electricity is recovered when the stored content falls and turns turbines to generate electrical energy. The group describes its method in a paper published 6 November in Strength.

“Instead of building a dam, we propose building a significant sand or gravel reservoir,” explains Hunt. The essential to MGES lies in obtaining two mountaintop internet sites that have a ideal variance in elevation—1,000 meters is great. “The higher the height variance, the more cost-effective the technologies,” he states.

The internet sites will look equivalent, with just about every comprised of a mine-like station to retail outlet the sand or gravel, and a filling station immediately under it. Valves release the content into waiting vessels, which are then transported by using cranes and motor-operate cables to the upper internet site. There, the sand or gravel is stored—for weeks, months, or even years—until it’s all set to be applied. When the content is moved again down the mountain, that stored gravitational electricity is released and transformed into electrical electricity.

The method is incredibly versatile, states Hunt, mainly because you can very easily alter the speed of the cables, enhance the load, or adjust the selection of vessels to satisfy varying electricity needs. And MGES is greater than classic extensive-time period storage procedures these kinds of as pumped-storage hydropower and dams mainly because its affect on the environment is small, Hunt statements. “Also, piles of sand are inexpensive, more cost-effective than h2o. And sand doesn’t evaporate so you can carry on using it indefinitely,” he states.

Hunt estimates that the annual cost of storing electricity by using this method will fluctuate amongst $fifty to $100 for every megawatt hour (MWh). Lithium-ion batteries, by comparison, cost at the very least 10 occasions far more. And he states that the electricity expended to transportation elements to the upper sits will be offset by the amount of money of gravitational electricity the method produces.  

Hunt and his co-authors are not the initial to propose using gravitational likely electricity as a storage option. Swiss startup Strength Vault has produced a “battery” that entails increasing and releasing five,000 concrete blocks as a result of a 33-tale building Edinburgh-dependent Gravitricity has strategies to drop weights down disused mine shafts and Heindl Strength in Germany would like to carry a incredibly significant rock mass using h2o pumps. But so considerably, no just one has recommended using mountains.

MGES technologies will be in particular beneficial for grids that have tiny electricity storage needs, states Hunt. These are normally microgrids making use of less than twenty megawatts, or the amount of money of electricity it requires to ability seven,000 four-bedroom houses. The technologies can most likely be applied to little or isolated islands these kinds of as Molokai in Hawaii, the Galapagos, and Cape Verde, exactly where the cost of giving electricity is significant and need is usually seasonal owing to tourism. 

“In these cases, it can be a viable choice [to fossil fuels],” he states. “It can be a serious detail in the potential.”