As Martin Schwoerer mentions, energy storage is a necessary part of any renewable energy solution. People in the energy industry talk about something called the “duck curve”. Basically, if you chart energy usage against renewables production, it looks a bit like a duck: at the end of the day, solar energy drops off, but people haven’t shut off their air conditioners because it’s still hot. Worse, they’re plugging in electric cars when they get home, and other appliances get turned on.
One approach is to use natural gas power generation to make up for the duck curve deficit (gas turbines spool up fairly quickly, and it’s much cleaner than coal). Nuclear works for this, but the nuclear fuel is hot 24/7, meaning there’d be a daytime surplus with this + renewables.
Large scale energy storage is one solution, particularly in islands that import all the hydrocarbons used for power generation (e.g. Japan, Puerto Rico, DR, etc.) There are non-battery storage solutions. For instance, if power is generated with hydro, water can be pumped uphill, the potential energy represented by the water above the turbines is stored energy. And there’s been some interesting work on large scale battery farms.
On the other hand, there is something called ‘microgrids’ (essentially an island in the power distribution network that can be connected to the network overall — and can be disconnected). For a microgrid the size of a house, the Tesla ‘powerwall’ makes sense. Utilities can encourage local storage in microgrids through time of use rate pricing (i.e. make it cheaper when there’s a grid surplus). In places where the overall grid is of questionable reliability (e.g. Puerto Rico) this is a no-brainer. It also couples well with grids supplied by a combination of 24/7 power (nuclear, hydro) and renewables.
The cohousing community I live in (25 families on about 18 acres) is considering becoming a microgrid — so I’ve been looking at this. We’re also looking at eventually disconnecting from natural gas heating and eventually we will all have electric cars, so it’s a bit challenging. Particularly as air-to-air heat pumps use a good bit of energy and we’re in a cold climate. The grid occasionally goes down (blizards and ice storms). (bright side: geothermal becomes more cost practical when houses are close enough together to be able to share wells/groundloops)
Finally, I’ve been tracking changes in battery technology. We’re about to see a large improvement in how quickly batteries can be charged (Tesla internal battery plate heat sinks / cooling) and the physical size / storage capacity relationship (graphine cathodes). The downside is that both these technologies use lithium, which is very dirty to extract.
