Grid-scale energy storage will be critical to the transition to zero emissions electricity. Today, batteries are being touted as the storage medium of choice, but there are lots of ways storing electricity for later use.
Energy Vault proposes to do it by lifting hundreds of concrete blocks weighing 35 metric tons each into the air and piling them on top of each other. The lifting is done using electric motors. Later, when the blocks are lowered to the ground, the motors turn into generators which send electricity back to the grid. Think of it as an electric vehicle weighing millions of pounds slowly descending a hill using regenerative braking to send electricity back to its battery.
The movement of the blocks is controlled autonomously by software that responds to changes in power availability in the electrical grid — storing up energy when electricity is abundant and creating electricity when needed.
According to TechCrunch, the company says the cost of its technology is lower than that of battery storage at about 6 cents per kilowatt-hour. In addition, its installations have a 40-year service life — about double that of battery storage facilities.
What may be even more important is that an Energy Vault system can store up to 80 megawatt-hours of electricity, which is far more than any battery installation in the world today. For comparison purposes, the new Tesla Megapack has a storage capacity of 3 megawatt-hours.
Energy Vault could be the answer to long term storage that will allow electricity created by spring winds or summer sun to heat homes in the winter. Note, however, that the Energy Vault system cannot provide the voltage and frequency regulation functions of a battery facility.
Softbank’s Vision Fund has been sufficiently impressed with the Energy Vault technology to make a $110 million investment in the company. Energy storage is poised to become big business as the transition to renewables heats up. ScottishPower has recently announced it plans to spend $7.2 billion between now and 2022 on renewable energy, grid upgrades, and storage technologies.
There are many energy storage proposals on the table at the moment, with pumped hydro accounting for the largest amount worldwide. But as the demand for storage increases, so will the ways of meeting that demand.
MIT has proposed a “sun in a box” concept in which the sun’s rays are used to heat liquid silicon until it glows white hot. While some concentrated solar systems plan to use silicon as a heat storage medium, the MIT approach would use solar panels to harvest the light from the molten silicon.
Who is leading in the solar storage sweepstakes? Arguably Tesla, with its new Megapack system. But terrain, access to the existing grid, and geographic considerations will likely favor one solution over others in any given scenario. Is there a place for the Energy Vault system? Softbank seems to think so. Check out the Energy Vault system in the video below.