The key to unlocking wind and solar: Making it last

For week 69, I covered ARES gravity storage. The concept is to use excess energy to move carts uphill. To reclaim that energy, you let gravity pull the cart back down.

In Australia they've taken that concept in a slightly different direction.

Australia's current political leadership ... earlier this year backed a project that would pump huge amounts of water up a hill to use as a backup energy option. Called "pumped hydro," this decades-old technology is the most common way to store energy, though it's a far less high-profile way than batteries.

Traditional batteries might seem like they're the future, but density and practicality are just as important as other natural resources. Batteries might be better served in transport rather than being responsible for the grid.

By the numbers:

• The government-backed pumped hydro project under construction now would have an ability to store 2,700 times more energy than the world's largest battery that Tesla built in South Australia.
• If built, the hydro project could produce the same power output as two large nuclear reactors and sustain that for a full week, according to Harvard University electricity expert Jesse Jenkins, who nonetheless predicts it will remain a niche technology in most regions given its location constraints.

Being able to store that amount of energy without a traditional battery is quite impressive. I wonder if wetter climates could make use of rain water to top the 'battery' up to claim even more energy.