>One of the big challenges now is whether the technology can be scaled up to really make a difference - and will the developers be able to use it to get electricity out as well as heat?

>The efficiency falls dramatically when the sand is used to just return power to the electricity grid.

So it's useful where you have district heating, but that's not most places.

Not really useful to turn the heat back into electricity.

It's something but it doesn't solve green energy's "big problem" like the headline suggests.